QUALITY CONTROL OF GAMMA CAMERA USING

PHANTOMS

AMARDEEP SINGH SRAN

MSc NUCLEAR MEDICINE

What is QC bull QC schedule for NM instrumentation prepared by a 1979

IAEA advisory groupbull The acceptance tests recommended from the American

association of physicists in medicine(AAPM)the International electrotecnical commission(IEC)and NEMA

bull Quality control which may be defined as an established set of ongoing measurements and analyses designed to ensure that the Performance of a procedure or instrument is within a predefined acceptable range

Quality Control of Equipments

bull Acceptance reference testingndash Measurements to assess whether instrumentation

comply with its specifications Manual availablebull Routine testing

ndash Performed to maintain high quality and standard of the equipment

bull Analysis of resultsndash Is the observed result significantly different from the

reference testingndash Is the observed result due to errors in the QC

procedurebull Records

Main Parametersbull The performance parameters most commonly evaluated

as part of a routine -camera QC program include-bull Uniformitybull Sensitivitybull Spatial resolutionbull Spatial linearitybull Energy resolution bull Peaking

PHANTOM REQUIRED FOR GAMMA CAMERA QC

bull Flood field phantombull Orthogonal hole transmission pattern

phantom Resolution and linearity phantom

bull PLES bar phantombull Step-wedge phantombull Total performance phantombull CT phantom

Construction of flood source phantom

bull Flood source phantom is used for measuring uniformity or sensitivity

bull Source and flood (dis water) are uniform mixedbull No air bubblesbull No overfilling with liquidbull The walls of the phantom should not be very

thickbcz thick walls increase the count in CFOVwhich is due to scattering and septum penetrationthese effect can cause non uniform result

bull Perspex (Lucite) wall thickness approximately 1 cm

bull No leakage of radioactive contents

Cont

bull The dimension of the flood source should be larger than the collimated FOV

bull After use if the phantom are not disposed the solution should be replenished regularly in order to avoid the growth of algae which is bind to Tc 99m compounds causing hot artifacts

Examples Fillable flood sources mdash air bubble

Results

Uniformity image A discrete circular cold area is seen in the middle of the FOV Visual inspection of the flood source revealed a large air bubble The cold indentation at the top left edge of the FOV was also due to an air bubble

Cont

Spatial resolution image using a four quadrant bar pattern A discrete large circular cold area is seen in the lower right quadrant By changing the position of the flood source the position of the cold area was also moved The cold area was due to an air bubble in the solution that was clearly visible on physical inspection

Example Fillable flood source mdash bulging sides

The phantom was filled with too much water which produced bulging of the centre part of the phantomResults The image shows a dome shaped increase in counts at the centre due to the bulging sides of the phantomComments This phantom had thin walls and when upended for the purpose of filling was prone to bulging if overfilled with water The effect could be avoided by filling the phantom in a horizontal position and with only the correct volume of water

FLOOD-FIELD PHANTOM

bull Co-57 Disc flood field phantom used in uniformity measurements

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

What is QC bull QC schedule for NM instrumentation prepared by a 1979

IAEA advisory groupbull The acceptance tests recommended from the American

association of physicists in medicine(AAPM)the International electrotecnical commission(IEC)and NEMA

bull Quality control which may be defined as an established set of ongoing measurements and analyses designed to ensure that the Performance of a procedure or instrument is within a predefined acceptable range

Quality Control of Equipments

bull Acceptance reference testingndash Measurements to assess whether instrumentation

comply with its specifications Manual availablebull Routine testing

ndash Performed to maintain high quality and standard of the equipment

bull Analysis of resultsndash Is the observed result significantly different from the

reference testingndash Is the observed result due to errors in the QC

procedurebull Records

Main Parametersbull The performance parameters most commonly evaluated

as part of a routine -camera QC program include-bull Uniformitybull Sensitivitybull Spatial resolutionbull Spatial linearitybull Energy resolution bull Peaking

PHANTOM REQUIRED FOR GAMMA CAMERA QC

bull Flood field phantombull Orthogonal hole transmission pattern

phantom Resolution and linearity phantom

bull PLES bar phantombull Step-wedge phantombull Total performance phantombull CT phantom

Construction of flood source phantom

bull Flood source phantom is used for measuring uniformity or sensitivity

bull Source and flood (dis water) are uniform mixedbull No air bubblesbull No overfilling with liquidbull The walls of the phantom should not be very

thickbcz thick walls increase the count in CFOVwhich is due to scattering and septum penetrationthese effect can cause non uniform result

bull Perspex (Lucite) wall thickness approximately 1 cm

bull No leakage of radioactive contents

Cont

bull The dimension of the flood source should be larger than the collimated FOV

bull After use if the phantom are not disposed the solution should be replenished regularly in order to avoid the growth of algae which is bind to Tc 99m compounds causing hot artifacts

Examples Fillable flood sources mdash air bubble

Results

Uniformity image A discrete circular cold area is seen in the middle of the FOV Visual inspection of the flood source revealed a large air bubble The cold indentation at the top left edge of the FOV was also due to an air bubble

Cont

Spatial resolution image using a four quadrant bar pattern A discrete large circular cold area is seen in the lower right quadrant By changing the position of the flood source the position of the cold area was also moved The cold area was due to an air bubble in the solution that was clearly visible on physical inspection

Example Fillable flood source mdash bulging sides

The phantom was filled with too much water which produced bulging of the centre part of the phantomResults The image shows a dome shaped increase in counts at the centre due to the bulging sides of the phantomComments This phantom had thin walls and when upended for the purpose of filling was prone to bulging if overfilled with water The effect could be avoided by filling the phantom in a horizontal position and with only the correct volume of water

FLOOD-FIELD PHANTOM

bull Co-57 Disc flood field phantom used in uniformity measurements

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Quality Control of Equipments

bull Acceptance reference testingndash Measurements to assess whether instrumentation

comply with its specifications Manual availablebull Routine testing

ndash Performed to maintain high quality and standard of the equipment

bull Analysis of resultsndash Is the observed result significantly different from the

reference testingndash Is the observed result due to errors in the QC

procedurebull Records

Main Parametersbull The performance parameters most commonly evaluated

as part of a routine -camera QC program include-bull Uniformitybull Sensitivitybull Spatial resolutionbull Spatial linearitybull Energy resolution bull Peaking

PHANTOM REQUIRED FOR GAMMA CAMERA QC

bull Flood field phantombull Orthogonal hole transmission pattern

phantom Resolution and linearity phantom

bull PLES bar phantombull Step-wedge phantombull Total performance phantombull CT phantom

Construction of flood source phantom

bull Flood source phantom is used for measuring uniformity or sensitivity

bull Source and flood (dis water) are uniform mixedbull No air bubblesbull No overfilling with liquidbull The walls of the phantom should not be very

thickbcz thick walls increase the count in CFOVwhich is due to scattering and septum penetrationthese effect can cause non uniform result

bull Perspex (Lucite) wall thickness approximately 1 cm

bull No leakage of radioactive contents

Cont

bull The dimension of the flood source should be larger than the collimated FOV

bull After use if the phantom are not disposed the solution should be replenished regularly in order to avoid the growth of algae which is bind to Tc 99m compounds causing hot artifacts

Examples Fillable flood sources mdash air bubble

Results

Uniformity image A discrete circular cold area is seen in the middle of the FOV Visual inspection of the flood source revealed a large air bubble The cold indentation at the top left edge of the FOV was also due to an air bubble

Cont

Spatial resolution image using a four quadrant bar pattern A discrete large circular cold area is seen in the lower right quadrant By changing the position of the flood source the position of the cold area was also moved The cold area was due to an air bubble in the solution that was clearly visible on physical inspection

Example Fillable flood source mdash bulging sides

The phantom was filled with too much water which produced bulging of the centre part of the phantomResults The image shows a dome shaped increase in counts at the centre due to the bulging sides of the phantomComments This phantom had thin walls and when upended for the purpose of filling was prone to bulging if overfilled with water The effect could be avoided by filling the phantom in a horizontal position and with only the correct volume of water

FLOOD-FIELD PHANTOM

bull Co-57 Disc flood field phantom used in uniformity measurements

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Main Parametersbull The performance parameters most commonly evaluated

as part of a routine -camera QC program include-bull Uniformitybull Sensitivitybull Spatial resolutionbull Spatial linearitybull Energy resolution bull Peaking

PHANTOM REQUIRED FOR GAMMA CAMERA QC

bull Flood field phantombull Orthogonal hole transmission pattern

phantom Resolution and linearity phantom

bull PLES bar phantombull Step-wedge phantombull Total performance phantombull CT phantom

Construction of flood source phantom

bull Flood source phantom is used for measuring uniformity or sensitivity

bull Source and flood (dis water) are uniform mixedbull No air bubblesbull No overfilling with liquidbull The walls of the phantom should not be very

thickbcz thick walls increase the count in CFOVwhich is due to scattering and septum penetrationthese effect can cause non uniform result

bull Perspex (Lucite) wall thickness approximately 1 cm

bull No leakage of radioactive contents

Cont

bull The dimension of the flood source should be larger than the collimated FOV

bull After use if the phantom are not disposed the solution should be replenished regularly in order to avoid the growth of algae which is bind to Tc 99m compounds causing hot artifacts

Examples Fillable flood sources mdash air bubble

Results

Uniformity image A discrete circular cold area is seen in the middle of the FOV Visual inspection of the flood source revealed a large air bubble The cold indentation at the top left edge of the FOV was also due to an air bubble

Cont

Spatial resolution image using a four quadrant bar pattern A discrete large circular cold area is seen in the lower right quadrant By changing the position of the flood source the position of the cold area was also moved The cold area was due to an air bubble in the solution that was clearly visible on physical inspection

Example Fillable flood source mdash bulging sides

The phantom was filled with too much water which produced bulging of the centre part of the phantomResults The image shows a dome shaped increase in counts at the centre due to the bulging sides of the phantomComments This phantom had thin walls and when upended for the purpose of filling was prone to bulging if overfilled with water The effect could be avoided by filling the phantom in a horizontal position and with only the correct volume of water

FLOOD-FIELD PHANTOM

bull Co-57 Disc flood field phantom used in uniformity measurements

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

PHANTOM REQUIRED FOR GAMMA CAMERA QC

bull Flood field phantombull Orthogonal hole transmission pattern

phantom Resolution and linearity phantom

bull PLES bar phantombull Step-wedge phantombull Total performance phantombull CT phantom

Construction of flood source phantom

bull Flood source phantom is used for measuring uniformity or sensitivity

bull Source and flood (dis water) are uniform mixedbull No air bubblesbull No overfilling with liquidbull The walls of the phantom should not be very

thickbcz thick walls increase the count in CFOVwhich is due to scattering and septum penetrationthese effect can cause non uniform result

bull Perspex (Lucite) wall thickness approximately 1 cm

bull No leakage of radioactive contents

Cont

bull The dimension of the flood source should be larger than the collimated FOV

bull After use if the phantom are not disposed the solution should be replenished regularly in order to avoid the growth of algae which is bind to Tc 99m compounds causing hot artifacts

Examples Fillable flood sources mdash air bubble

Results

Uniformity image A discrete circular cold area is seen in the middle of the FOV Visual inspection of the flood source revealed a large air bubble The cold indentation at the top left edge of the FOV was also due to an air bubble

Cont

Spatial resolution image using a four quadrant bar pattern A discrete large circular cold area is seen in the lower right quadrant By changing the position of the flood source the position of the cold area was also moved The cold area was due to an air bubble in the solution that was clearly visible on physical inspection

Example Fillable flood source mdash bulging sides

The phantom was filled with too much water which produced bulging of the centre part of the phantomResults The image shows a dome shaped increase in counts at the centre due to the bulging sides of the phantomComments This phantom had thin walls and when upended for the purpose of filling was prone to bulging if overfilled with water The effect could be avoided by filling the phantom in a horizontal position and with only the correct volume of water

FLOOD-FIELD PHANTOM

bull Co-57 Disc flood field phantom used in uniformity measurements

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Construction of flood source phantom

bull Flood source phantom is used for measuring uniformity or sensitivity

bull Source and flood (dis water) are uniform mixedbull No air bubblesbull No overfilling with liquidbull The walls of the phantom should not be very

thickbcz thick walls increase the count in CFOVwhich is due to scattering and septum penetrationthese effect can cause non uniform result

bull Perspex (Lucite) wall thickness approximately 1 cm

bull No leakage of radioactive contents

Cont

bull The dimension of the flood source should be larger than the collimated FOV

bull After use if the phantom are not disposed the solution should be replenished regularly in order to avoid the growth of algae which is bind to Tc 99m compounds causing hot artifacts

Examples Fillable flood sources mdash air bubble

Results

Uniformity image A discrete circular cold area is seen in the middle of the FOV Visual inspection of the flood source revealed a large air bubble The cold indentation at the top left edge of the FOV was also due to an air bubble

Cont

Spatial resolution image using a four quadrant bar pattern A discrete large circular cold area is seen in the lower right quadrant By changing the position of the flood source the position of the cold area was also moved The cold area was due to an air bubble in the solution that was clearly visible on physical inspection

Example Fillable flood source mdash bulging sides

The phantom was filled with too much water which produced bulging of the centre part of the phantomResults The image shows a dome shaped increase in counts at the centre due to the bulging sides of the phantomComments This phantom had thin walls and when upended for the purpose of filling was prone to bulging if overfilled with water The effect could be avoided by filling the phantom in a horizontal position and with only the correct volume of water

FLOOD-FIELD PHANTOM

bull Co-57 Disc flood field phantom used in uniformity measurements

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

bull The dimension of the flood source should be larger than the collimated FOV

bull After use if the phantom are not disposed the solution should be replenished regularly in order to avoid the growth of algae which is bind to Tc 99m compounds causing hot artifacts

Examples Fillable flood sources mdash air bubble

Results

Uniformity image A discrete circular cold area is seen in the middle of the FOV Visual inspection of the flood source revealed a large air bubble The cold indentation at the top left edge of the FOV was also due to an air bubble

Cont

Spatial resolution image using a four quadrant bar pattern A discrete large circular cold area is seen in the lower right quadrant By changing the position of the flood source the position of the cold area was also moved The cold area was due to an air bubble in the solution that was clearly visible on physical inspection

Example Fillable flood source mdash bulging sides

The phantom was filled with too much water which produced bulging of the centre part of the phantomResults The image shows a dome shaped increase in counts at the centre due to the bulging sides of the phantomComments This phantom had thin walls and when upended for the purpose of filling was prone to bulging if overfilled with water The effect could be avoided by filling the phantom in a horizontal position and with only the correct volume of water

FLOOD-FIELD PHANTOM

bull Co-57 Disc flood field phantom used in uniformity measurements

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Examples Fillable flood sources mdash air bubble

Results

Uniformity image A discrete circular cold area is seen in the middle of the FOV Visual inspection of the flood source revealed a large air bubble The cold indentation at the top left edge of the FOV was also due to an air bubble

Cont

Spatial resolution image using a four quadrant bar pattern A discrete large circular cold area is seen in the lower right quadrant By changing the position of the flood source the position of the cold area was also moved The cold area was due to an air bubble in the solution that was clearly visible on physical inspection

Example Fillable flood source mdash bulging sides

The phantom was filled with too much water which produced bulging of the centre part of the phantomResults The image shows a dome shaped increase in counts at the centre due to the bulging sides of the phantomComments This phantom had thin walls and when upended for the purpose of filling was prone to bulging if overfilled with water The effect could be avoided by filling the phantom in a horizontal position and with only the correct volume of water

FLOOD-FIELD PHANTOM

bull Co-57 Disc flood field phantom used in uniformity measurements

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

Spatial resolution image using a four quadrant bar pattern A discrete large circular cold area is seen in the lower right quadrant By changing the position of the flood source the position of the cold area was also moved The cold area was due to an air bubble in the solution that was clearly visible on physical inspection

Example Fillable flood source mdash bulging sides

The phantom was filled with too much water which produced bulging of the centre part of the phantomResults The image shows a dome shaped increase in counts at the centre due to the bulging sides of the phantomComments This phantom had thin walls and when upended for the purpose of filling was prone to bulging if overfilled with water The effect could be avoided by filling the phantom in a horizontal position and with only the correct volume of water

FLOOD-FIELD PHANTOM

bull Co-57 Disc flood field phantom used in uniformity measurements

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Example Fillable flood source mdash bulging sides

The phantom was filled with too much water which produced bulging of the centre part of the phantomResults The image shows a dome shaped increase in counts at the centre due to the bulging sides of the phantomComments This phantom had thin walls and when upended for the purpose of filling was prone to bulging if overfilled with water The effect could be avoided by filling the phantom in a horizontal position and with only the correct volume of water

FLOOD-FIELD PHANTOM

bull Co-57 Disc flood field phantom used in uniformity measurements

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

FLOOD-FIELD PHANTOM

bull Co-57 Disc flood field phantom used in uniformity measurements

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Uniformity

bull It is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation

bull A non uniform area may be visualized as a hot spot or a cold spot

-Camera uniformity may be evaluated either intrinsically ie without collimation or extrinsically ie with collimator and is also known as system uniformity

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

57Co Flood Sheet Source

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Extrinsic Uniformity

bull Extrinsically a uniform flood or sheet source (typically 185ndash555 MBq) of 57Co is placed directly on the collimated detector

bull A total of 10ndash15 million counts is acquired ( for both intrinsic as well as extrinsic) and uniformity quantitated for the integral and differential uniformities which actually express the deviation from uniformity of the flood image

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Quantitate uniformity

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

bull IUs of 3 amp DUs of to 2 or better are routinely obtained for modern -cameras

bull An alternative and perhaps even more robust measure of uniformity is the SD of the counts per pixel in the flood image

bull If -camera uniformity for any radionuclide is out of tolerance (ie IU or DU gt 5) the uniformity (or sensitivity) correction table of that radionuclide should be updated

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cause of non uniformity

A

bull Wrong energy window setting

bull Eg extrinsic flood field uniformity

bull Co-57 sheet source used as a phantom

bull In both instances the energy window had not been set for 57Co but remained at the energy window setting of 99mTc

Results Both images show non-uniformity

Fig A shows poor tuning and visible PM tubesFig B shows discrete small cold spots

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

bull Comment-

This incorrect energy window still produces a reasonable count rate so that an image can be made However the time taken for collectionof the image is much longer than is usual

if the reverse situation existed and 99mTc were imaged in a 57Co energy window then the cold spots seen in image B would become hot spots

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Example Static clinical study energy peak shift electrical grounding problem

This static clinical lung perfusion study using 99mTc macroaggregates was obtained with the scintillation camera

Six static images (400 000 counts each image) forming a clinical lung perfusion study in six different views

Results In the set of images of the lungs two intense hot spots are seen in the same location in the right half of the FOV in each image

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

bull The artefacts were observed at a time when the camera was known to have an unstable photopeak position with respect to the energy window The changes in energy peak position were dynamic processes and were caused by a fault in the electrical grounding of the digital camera which had one ADC per PM tube Significant changes could be found within minutes

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Symmetric energy window mdash 99mTc

bull A symmetric energy window is one where the photopeak energy is at the centre of the window

bull For 99mTcbull A 20 energy window set symmetrically over

the 99mTc photopeak is equivalent to140 plusmn 10 keV or a window spanning 126ndash154 keV

bull A 15 energy window set symmetrically over the 99mTc photopeak is equivalent to140 plusmn 75 keV or a window spanning 130ndash151 keV

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Symmetric 20 energy window

Routine intrinsic uniformity image 99mTc 3 million counts 20 energy window set symmetrically over the 140 keV photopeak of 99mTcResults The image shows good uniformity

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Example Asymmetric energy window mdash crystal hydration

Intrinsic uniformity 99mTc 30 million counts each image 512 times 512 matrixTL 20 symmetric energy windowTR 10 asymmetric high energy windowBL 10 asymmetric low energy window

Results The effect of hydration is clearly visible on the right border of the FOV It is seen as discrete cold spots on the offset high image (TR) and as complementary hot spots on the offset low image(BL) An indication of the presence of hydration is also visible on the symmetric window image (TL)

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

bull Comments

A high number of total counts is required When obtaining a digital image a large matrix size (small pixel size) must be used because larger pixel sizes could cause small scale defects to be concealed

since it is already visible in the symmetric energy window image However the hydration is at the edge of the FOV and when the collimator is mounted it will not give artefacts in clinical images This situation needs to be carefully monitored inorder to assess the progress of hydration as it spreads and covers more of the FOV The crystal will eventually need to be replaced

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Spatial Resolution

bull The ability to resolve two separate point of radiation as separate entities

bull In practice spatial resolution is generally assessed semi quantitatively by using of resolution phantom such as the 4-quadrant bar phantom

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Spatial Resolution Phantoms

Four-QuadrantBarPhantom

OrthogonalHole

(PLES)

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

RESOLUTION AND LINEARITY PHANTOM

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Spatial Linearity

bull It the amount of spatial distortion of the image with respect to the object

bull Image of PLES Phantom deviation from straight line of less than 05mm for CFOV and 09 mm for UFOV

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Image Non-Linearity

bull Non-linearity refers to that a straight line object appear as curved line image

bull Non-linearity occurs when the X and Y positional signals do not change linearly with the displacement distance

bull ldquoPincushionrdquo distortion is an inward ldquobowingrdquo image and ldquoBarrelrdquo distortion is an outward ldquobowingrdquo image

bull A PM tube may have high light collection efficiency in the centre which may result in a ldquopincushionrdquo in the centre and ldquobarrelrdquo between PM tubes This kind of images could results in a ldquowavyrdquo line pattern

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Example NEMA slit pattern mdash non-linearity

Intrinsic image of the NEMA slit phantom pattern (1 mm wide slits in a sheet of lead with separations of 30 mm) using a distance point source of 99mTcAt 5 UFOV distance20 energy window3 million countsResults Image shows distinct non-linearity of the lines Also the lines have different intensities

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Example effect of no linearity or energy corrections being applied

Four quadrant bar pattern intrinsic uniformity 99mTc 4 million counts

Results The bar pattern image shows wavy lines compressed towards the centre of the PM tubes and expanding between the tubes This is due to non-linearity The hot areas corresponding to PM tubesare an effect of no energy correction being applied

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Energy Resolution

bull Energy resolution is the ability to distinguish between photons of different energies in particular between primary and scattered radiation

-Camera energy resolution may be evaluated by the percentage FWHM of the photopeak energy

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

4-Quadrant Bar Phantom

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

-cameraimage of 4-quadrant bar phaomnt

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

bull Intrinsic resolution in X amp Y directions can be estimated in terms of FWHM of line spread function using relationship

bull FWHM = 175B

bull Where B is the width of smallest bars that camera can resolve

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Extrinsic Resolution

bull System spatial resolution can also be determine by using quadrate bar phantom along with fillable or 57Co flood source

bull Extrinsic resolution is the quadrature sum of the geometric resolution of the collimator and the intrinsic resolution of the detector

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Sensitivity

bull Ability to detect ionizing events in a sodium iodide crystal expressed in counts per second per micro curie (cpsuCi)

bull Measured simultaneously when uniformity performed if source activity and room background known

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

bull Source must be measured amp corrected for decay

bull Obtain the count rate per unit activitybull Compare calculated sensitivity with previous

valuesbull Change in sensitivity is useful indicator of slow

degradation of the systembull Should be done routinely as recommended by

manufacturer

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Factors Affecting Sensitivity Results

bull Incorrect energy settings

bull Incorrect collimation in case of extrinsic studies

bull Sensitivity does not change as the source is moved away from the collimator

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Orthogonal hole test phantom

bull OHTP used for image non-uniformity and special distortion it is also used for special resolution and pixel size

bull Construction-

bull OHTP consisted of 496 mm diameter and 6 mm thick lead plate in which a regular array of 15 mm diameter(3 mm acc to NEMA) holes has been drilled

bull The inter hole spacing is 15 mm in the x direction and 175 mm in the y direction

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

ORTHOGONAL HOLE TRANSMISSION PHANTOM

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Uniformity and sensitivity test using OHTP

bull Remove collimator OHTP pattern is placed on the face of the detector

bull A point source of Tc-99m (500-600 micro Ci) is placed at a distance 5 UFOV to obtain a parallel beam of photons

bull Matrix size is 128 into128bull Energy window 20bull Total no of counts are 80 kctsbull Time taken for this procedure is approx less than 5

minbull Ref-OHTP for QC of sci camerasby Roert

ylchuPhD Radiology 145848-49dec1982

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

a Image of the test pattern (128 X 128 matrix)

b A sub matrix (64 X 64) from the center of the image shown in a

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

STEP-WEDGE PHANTOM

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Step-wedge phantom

bull Step-wedge phantom is used for optional test

bull We check contrast sensitivity with a chosen radionuclide in flood source configuration by using step-wedge phantom

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

TOTAL PERFORMANCE PHANTOM

bull Overall system performance may be evaluated using any number of commercially available fillable phantoms containing non radioactive (cold) inserts of different sizes and visually inspecting the resulting images

For such cylinder phantom studies a 99mTc For such cylinder phantom studies a 99mTc activity of about 10 mCi and at least 64 activity of about 10 mCi and at least 64 projections at 40 s per projection or longer are projections at 40 s per projection or longer are recommended Usrecommended Using this phantom overall SPECT system performance should be checked

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

CT phantom

bull CT phantom is used for CT QC In combined SPECTCT system

bull Using this phantom we check-bull Calibration- the reconstructed CT image must

exhibit accurate absolute CT no (in bn 0 to 5 HU)ndash Calibration is done using phantom that includes insert

a known CT nondash Calibration is checked daily with a water filled cylinder

(usually 24 cm in diameter provided by manufacture)

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

bull Field uniformity-ndash To check reconstructed CT image must

exhibit uniform response throughout the field of view (FOV)

Schedule of diagnostic-quality CT QC for SPECTCT unitsTest FrequencyWater phantom QC- DailyTube warm-up -DailyAir calibration (ldquofast QCrdquo)- DailyWater phantom checks slice thickness accuracy positioning-

Monthly

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

bull The SPECT (emission image) and (transmission image) CT image must be in registration in practice this means that the SPECT and CT acquisition may not simultaneously image the same slice (due to x y z misalignment of bed motion)ndash Error of misalignment should not be greater

than the specific resolution of SPECT scan

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Cont

bull Attenuation correction accuracy-ndash The use of the CT image for SPECT att Correction

require a transformation of observed CT no to att Coefficient at the energy of the radionuclide

Misregistration consequencees-Recent pub Suggest that an incidence in excess of 40 of misregistration judged to be ldquomoderate to severe ldquo effect occur routinelyMisregistration by only one pixel may create perfusion artifacts

Ref-ASNC imaging guidelines for nucl Cardiology procedures J nucl Cardiol novdec 200714e61-78

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Quality Control Practicesbull 1 Peak daily for 57Co 99mTc amp other isotopes to be used that day

bull 2 Uniformity - Flood images of 5-15 million counts each day of usebull before imaging beginsbull a) Extrinsic flood image is preferred and tests heavily usedbull collimators

bull b) Intrinsic flood image to test detector only especially at thebull periphery of the FOV Acquired at least one per week

bull 3 Resolution - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts of four-quadrant bar phantom once per week

bull 4 Linearity - Intrinsic (preferred) or extrinsic images of 5-10 millionbull counts with PLES or four-quadrant bar phantom once per week

bull 5 Uniformity Correction Matrix 1056787 Flood images of 100 Mcts or morebull once per month for each isotope used (vendor dependent)

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You

Thank You

• QUALITY CONTROL OF GAMMA CAMERA USING PHANTOMS
• What is QC
• Quality Control of Equipments
• Main Parameters
• PHANTOM REQUIRED FOR GAMMA CAMERA QC
• Construction of flood source phantom
• Cont
• Examples Fillable flood sources mdash air bubble
• Slide 9
• Example Fillable flood source mdash bulging sides
• FLOOD-FIELD PHANTOM
• Uniformity
• Slide 13
• 57Co Flood Sheet Source
• Extrinsic Uniformity
• Quantitate uniformity
• Slide 17
• Cause of non uniformity
• Slide 19
• Example Static clinical study energy peak shift electrical grounding problem
• Slide 24
• Symmetric energy window mdash 99mTc
• Symmetric 20 energy window
• Example Asymmetric energy window mdash crystal hydration
• Slide 28
• Spatial Resolution
• Spatial Resolution Phantoms
• RESOLUTION AND LINEARITY PHANTOM
• Spatial Linearity
• Image Non-Linearity
• Slide 34
• Example NEMA slit pattern mdash non-linearity
• Example effect of no linearity or energy corrections being applied
• Energy Resolution
• 4-Quadrant Bar Phantom
• g-camera image of 4-quadrant bar phaomnt
• Slide 40
• Extrinsic Resolution
• Sensitivity
• Slide 43
• Factors Affecting Sensitivity Results
• Orthogonal hole test phantom
• ORTHOGONAL HOLE TRANSMISSION PHANTOM
• Uniformity and sensitivity test using OHTP
• Slide 48
• STEP-WEDGE PHANTOM
• Step-wedge phantom
• TOTAL PERFORMANCE PHANTOM
• CT phantom
• Slide 55
• Slide 56
• Slide 57
• Quality Control Practices
• Slide 59
• Slide 60
• Thank You