1.Diagnostic Procedures Part 7 Optimization of Protection inOptimization of Protection in Medical ExposureMedical Exposure IAEA Training Material on Radiation Protection in Nuclear Medicine

2. Part 7. Medical Exposure Diagnostic Procedures2Nuclear Medicine OBJECTIVEOBJECTIVE To be able to apply the principles of radiation protection including design, operational considerations, calibration, clinical dosimetry and quality control for diagnostic procedures using these major equipment: Activity meter, monitoring equipment, probes, scanners, gamma cameras, SPECT-system including coincidence option, and PET. 3. Part 7. Medical Exposure Diagnostic Procedures3Nuclear Medicine ContentContent Activity meter and calibration of sources Probes and counters Equipment for morphological and functional studies Scanner Gamma camera PET Clinical dosimetry 4. Part 7. Medical Exposure Diagnostic Procedures4Nuclear Medicine OptimizationOptimization (BSS II.17)(BSS II.17) (b) (iii) appropriate image acquisition and(b) (iii) appropriate image acquisition and processing;processing; 5. Part 7. Medical Exposure Diagnostic Procedures5Nuclear Medicine QUALITY ASSURANCE (BSS)QUALITY ASSURANCE (BSS) II.23. Quality assurance programmes for medical exposures shall include: (a) Measurements of the radiation generators, imaging devices and irradiation installations at the time of commissioning and periodically thereafter. 6. Part 7. Medical Exposure Diagnostic Procedures6Nuclear Medicine OPTIMIZED USE OF EQUIPMENTOPTIMIZED USE OF EQUIPMENT Well trained staff with access to relevant manuals Quality control programme Regular maintenance 7. Module 7.1. Activity meter andModule 7.1. Activity meter and calibration of sourcescalibration of sources Part 7 Optimization of Protection inOptimization of Protection in Medical ExposureMedical Exposure IAEA Training Material on Radiation Protection in Nuclear Medicine 8. Part 7. Medical Exposure Diagnostic Procedures8Nuclear Medicine ACTIVITY METERACTIVITY METER DOSE CALIBRATORDOSE CALIBRATOR 9. Part 7. Medical Exposure Diagnostic Procedures9Nuclear Medicine CALIBRATION OF SOURCESCALIBRATION OF SOURCES BSS II.19BSS II.19 Registrants and licensees shall ensure that: (a) the calibration of sources used for medical exposure be traceable to a Standards dosimetry laboratory (d) unsealed sources for nuclear medicine procedures be calibrated in terms of activity of the radio- pharmaceutical to be administered, the activity being determined and recorded at the time of administration; 10. Part 7. Medical Exposure Diagnostic Procedures10Nuclear Medicine Activity meterActivity meter SC97 Proportionality between the number of photons emitted and the ionization current Well-shaped ionization chamber filled with a gas of high atomic number (e.g. Xenon) and kept under pressure 11. Part 7. Medical Exposure Diagnostic Procedures11Nuclear Medicine Activity meterActivity meter The response of the detector will depend on: Radionuclide (energy and abundance of photons). Geometry of the detector. Geometry of the source. The condition of the instrument (QC). 12. Part 7. Medical Exposure Diagnostic Procedures12Nuclear Medicine Activity meterActivity meter Calibration should be made at factory using reference sources that are traceable to a standard laboratory 13. Part 7. Medical Exposure Diagnostic Procedures13Nuclear Medicine ACTIVITY MEASUREMENTACTIVITY MEASUREMENT Setting Measured activity Tc-99m 1.00 Co-57 1.19 In-111 2.35 Tl-201 1.76 Ga-67 1.12 I-123 2.19 I-131 1.43 Measured activity/True activity of Tc.99m if the indicated settings are used 14. Part 7. Medical Exposure Diagnostic Procedures14Nuclear Medicine Geometric efficiencyGeometric efficiency The quotient: number of photons reaching the detector over the number of photons emitted from the sample Increasing geometric efficiency 15. Part 7. Medical Exposure Diagnostic Procedures15Nuclear Medicine SAMPLE HOLDERSAMPLE HOLDER (reproducible geometry)(reproducible geometry) 16. Part 7. Medical Exposure Diagnostic Procedures16Nuclear Medicine Radionuclide settings Background Reproducibility Radionuclide settings Background Reproducibility Activity meterActivity meter Operational considerations 17. Part 7. Medical Exposure Diagnostic Procedures17Nuclear Medicine Acceptance Daily Monthly Yearly High voltage/display P T T P Zero adjust P T T P Background P T T P Accuracy P P Precision P T P Relative responses P T P Subsidiary calibrations P Linearity P P Electrical safety P P Leakage radiation P P P: physicist The accuracy should be +/- 5% T: technician Traceability to a national standard. Interlaboratory comparisons. QUALITY CONTROL OF ACTIVITY METER (what should be done and who should do it) 18. Part 7. Medical Exposure Diagnostic Procedures18Nuclear Medicine Sealed sources for calibrationSealed sources for calibration of activity metersof activity meters Long half-life Range of photon energies Range of activities Calibrated within 5% Co57, Ba133, Cs137, Co60 19. Part 7. Medical Exposure Diagnostic Procedures19Nuclear Medicine Sealed sources for calibrationSealed sources for calibration of activity metersof activity meters RadionuclideRadionuclide PhotonPhoton energy (keV)energy (keV) Half-lifeHalf-life ActivityActivity (MBq)(MBq) Co-57Co-57 122122 271 d271 d 185185 Ba-133Ba-133 81, 35681, 356 10.7 y10.7 y 9.39.3 Cs-137Cs-137 662662 30 y30 y 7.47.4 Co-60Co-60 1173, 13321173, 1332 5.27 y5.27 y 1.91.9 20. Part 7. Medical Exposure Diagnostic Procedures20Nuclear Medicine Source (sealed): Cs-137 or Co-57 Procedure: Select settings for the radionuclide and adjust background. Insert source in holder and make 10 measurements. Data analysis: To assess precision, calculate for each source (i) the percentage difference between the measured activity Ai and their mean Amv. (+/-5%) To assess accuracy, calculate the percentage difference between the mean activity and the certified activity. (+/- 10%). Measurement of precision and accuracy 21. Part 7. Medical Exposure Diagnostic Procedures21Nuclear Medicine Mv: 9.834 SD: 0.125 0 5 10 15 20 0 20 40 60 Measurement no Activity Measure the activity of a sealed reference source e.g. every morning. Use Tc-99m settings. Measurement of reproducibility 22. Part 7. Medical Exposure Diagnostic Procedures22Nuclear Medicine Use a radionuclide with short half-life e.g. Tc-99m Make repeated measurements during several half-lives. Slope = -0.11471, R2=0.9999 T=6.04 h 1 10 100 1000 10000 100000 0 20 40 60 Time (h) Activity(MBq) Measurement of linearity 23. Part 7. Medical Exposure Diagnostic Procedures23Nuclear Medicine Measurement of linearity Graded source method Pipette into a series of sample vials by means of the remote pipetting device decreasing volumes of the radionuclide solution, with activities covering the range of interest (e.g. 10, 5, 2, l, 0.5, .2, 0.1 ml of a solution having an activity about 370 MBq/ml). Bring up the total volume in each vial to constant volume (e.g. 20 ml). Measure and record the activity. Attenuators Use a set of lead attenuators calibrated to to reduce the photon fluence from Tc-99m in a known way and hence simulating different activities. Measure and record the activity. A=A0 exp (- d) 24. Module 7.2. Sample countersModule 7.2. Sample counters and probesand probes Part 7 Optimization of Protection inOptimization of Protection in Medical ExposureMedical Exposure IAEA Training Material on Radiation Protection in Nuclear Medicine 25. Part 7. Medical Exposure Diagnostic Procedures25Nuclear Medicine Gamma counter Liquid scintillation counter Sample countersSample counters 26. Part 7. Medical Exposure Diagnostic Procedures26Nuclear Medicine RIA 125 I Kidney clearance 51 Cr Vitamin B12 deficiency 57 Co,58 Co Ferrokinetic studies 59 Fe Total body water 3 H Blood volume 125 I, 51 Cr, 99m Tc Biomedical research 3 H, 14 C Examples of use of sample counters 27. Part 7. Medical Exposure Diagnostic Procedures27Nuclear Medicine HV Ampl. PHA Timer Scaler Rate- meterGain Base Window Voltage Detector Sample Lead shield PM-tube Gamma counterGamma counter 28. Part 7. Medical Exposure Diagnostic Procedures28Nuclear Medicine Detector Photocathode cathodd Dynodes Anode Amplifier PHA Scaler Scintillation detectorScintillation detector Proportionality between the signal and the energy absor- bed in the detector 29. Part 7. Medical Exposure Diagnostic Procedures29Nuclear Medicine Pulse height analyzerPulse height analyzer UL LL Time Pulse height (V) The pulse height analyzer allows only pulses of a certain height (energy) to be counted. counted not counted 30. Part 7. Medical Exposure Diagnostic Procedures30Nuclear Medicine Pulse-height distributionPulse-height distribution NaI(Tl)NaI(Tl) 31. Part 7. Medical Exposure Diagnostic Procedures31Nuclear Medicine PROBE SYSTEMPROBE SYSTEM Thyroid uptake measurements Radionuclide angiography Renography 32. Part 7. Medical Exposure Diagnostic Procedures32Nuclear Medicine HV Ampl. PHA Timer Scaler Rate- meterGain Base Window Voltage Recorder Collimator PM D Probe systemProbe system 33. Part 7. Medical Exposure Diagnostic Procedures33Nuclear Medicine Window setting Geometry Reproducibility Count losses Background Operational considerations GAMMA COUNTERGAMMA COUNTER PROBEPROBE 34. Part 7. Medical Exposure Diagnostic Procedures34Nuclear Medicine Energy window setting depends on the energy resolution of the detector and the photon energies Window settingWindow setting 35. Part 7. Medical Exposure Diagnostic Procedures35Nuclear Medicine Gamma counter Different design of the detector 36. Part 7. Medical Exposure Diagnostic Procedures36Nuclear Medicine REPRODUCIBILITYREPRODUCIBILITY Mv: 9.834 SD: 0.125 0 5 10 15 20 0 20 40 60 Measurement no Activity Measure the activity of a reference source e.g. every morning or every week. Use window settings corresponding to the radionuclide 37. Part 7. Medical Exposure Diagnostic Procedures37Nuclear Medicine COUNT LOSSESCOUNT LOSSES ((LINEARITY OF ACTIVITY RESPONSE)LINEARITY OF ACTIVITY RESPONSE) Decaying source method Graded source method 38. Part 7. Medical Exposure Diagnostic Procedures38Nuclear Medicine PM PM Coinc Ampl PHA Scaler Timer Sample No window 100% geometric efficiency Liquid scintillation counterLiquid scintillation counter 39. Part 7. Medical Exposure Diagnostic Procedures39Nuclear Medicine Counting efficiency Quenching Sample preparation Window setting Reproducibility Background Counting efficiency Quenching Sample preparation Window setting Reproducibility Background Operational considerations Liquid scintillation counter 40. Part 7. Medical Exposure Diagnostic Procedures40Nuclear Medicine QUALITY CONTROLQUALITY CONTROL Scaler/timer/rate meter function Energy calibration Energy resolution Preset analyser facilities Sensitivity, counting efficiency Counting precision Count rate losses Linearity of energy response Background Linearity of activity response Geometrical response Quench correction methods (LSC) 41. Part 7. Medical Exposure Diagnostic Procedures41Nuclear Medicine IAEA-TECDOC-602 Quality control of Nuclear medicine instruments 1991 INTERNATIONAL ATOMIC ENERGY AGENCY IAEA May 1991 42. Module 7.3. Equipment forModule 7.3. Equipment for morphological and functional studiesmorphological and functional studies Part 7 Optimization of Protection inOptimization of Protection in Medical ExposureMedical Exposure IAEA Training Material on Radiation Protection in Nuclear Medicine 43. Part 7. Medical Exposure Diagnostic Procedures43Nuclear Medicine RECTILINEAR SCANNERRECTILINEAR SCANNER HV Ampl. PHA Scaler Rate- meter Gain Base Window Voltage Display processor Scanner drive mechanism Display device 44. Part 7. Medical Exposure Diagnostic Procedures44Nuclear Medicine RECTILINEAR SCANNERRECTILINEAR SCANNER Rollo 1977 Used to measure the spatial distribution of a radiopharmaceutical 45. Part 7. Medical Exposure Diagnostic Procedures45Nuclear Medicine COLLIMATORCOLLIMATOR Lead septa Focal distance Focal plane Focal point NaI (Tl) crystal Collimator crystal side Collimator patient side 46. Part 7. Medical Exposure Diagnostic Procedures46Nuclear Medicine COLLIMATORCOLLIMATOR 47. Part 7. Medical Exposure Diagnostic Procedures47Nuclear Medicine SCANNER IMAGESSCANNER IMAGES 48. Part 7. Medical Exposure Diagnostic Procedures48Nuclear Medicine SCANNERSCANNER Operational considerations: Scanning speed (optimum count density) Collimator Collimator mounting Tapper function Window setting Background 49. Part 7. Medical Exposure Diagnostic Procedures49Nuclear Medicine SCANNER QUALITY CONTROLSCANNER QUALITY CONTROL Acceptance Daily Weekly Yearly Energy window P T T P Energy resolution P P Sensitivity P T P Counting precision P P Linearity of energy response P P Test of integral background P T P Test of preset analyzer facilities P P System linearity P T P Background subtraction P P Contrast enhancement P P Scanner drive P P Total performance P T P P: physicist, T:technician 50. Part 7. Medical Exposure Diagnostic Procedures50Nuclear Medicine TOTAL PERFORMANCE PHANTOMTOTAL PERFORMANCE PHANTOM 51. Part 7. Medical Exposure Diagnostic Procedures51Nuclear Medicine Gamma cameraGamma camera Used to measure the spatial and temporal distribution of a radiopharmaceutical Siemens 52. Part 7. Medical Exposure Diagnostic Procedures52Nuclear Medicine Gamma cameraGamma camera ((principle of operation)principle of operation) PM-tubes Detector Collimator Position X Position Y Energy Z 53. Part 7. Medical Exposure Diagnostic Procedures53Nuclear Medicine Counter Clock PulsesEnergy windowr Time PHA ADC Computer Patient z x y GAMMA CAMERA 54. Part 7. Medical Exposure Diagnostic Procedures54Nuclear Medicine PM-tubesPM-tubes 55. Part 7. Medical Exposure Diagnostic Procedures55Nuclear Medicine Gamma camera collimatorsGamma camera collimators 56. Part 7. Medical Exposure Diagnostic Procedures56Nuclear Medicine Static Dynamic ECG-gated Wholebody scanning Tomography ECG-gated tomography Wholebody tomography Gamma camera Data acquisition 57. Part 7. Medical Exposure Diagnostic Procedures57Nuclear Medicine Dynamic acquisitionDynamic acquisition 58. Part 7. Medical Exposure Diagnostic Procedures58Nuclear Medicine R Interval n Image n ECG-gated acquisitionECG-gated acquisition 59. Part 7. Medical Exposure Diagnostic Procedures59Nuclear Medicine ECG-gated bloodpool scintigraphy 60. Part 7. Medical Exposure Diagnostic Procedures60Nuclear Medicine Left ventricle time-activity curveLeft ventricle time-activity curve 61. Part 7. Medical Exposure Diagnostic Procedures61Nuclear Medicine Whole body scanning 62. Part 7. Medical Exposure Diagnostic Procedures62Nuclear Medicine Tomographic acquisitionTomographic acquisition 63. Part 7. Medical Exposure Diagnostic Procedures63Nuclear Medicine y z x x-position Count rate z y Tomographic reconstruction 64. Part 7. Medical Exposure Diagnostic Procedures64Nuclear Medicine Tomographic planesTomographic planes 65. Part 7. Medical Exposure Diagnostic Procedures65Nuclear Medicine Myocardial scintigraphy 66. Part 7. Medical Exposure Diagnostic Procedures66Nuclear Medicine ECG GATED TOMOGRAPHYECG GATED TOMOGRAPHY 67. Part 7. Medical Exposure Diagnostic Procedures67Nuclear Medicine Distribution of radiopharmaceutical Collimator selection and sensitivity Spatial resolution Energy resolution Uniformity Count rate performance Spatial positioning at different energies Center of rotation Scattered radiation Attenuation Noise Distribution of radiopharmaceutical Collimator selection and sensitivity Spatial resolution Energy resolution Uniformity Count rate performance Spatial positioning at different energies Center of rotation Scattered radiation Attenuation Noise Factors affecting image formation 68. Part 7. Medical Exposure Diagnostic Procedures68Nuclear Medicine Distribution ofDistribution of radiopharmaceuticalradiopharmaceutical 69. Part 7. Medical Exposure Diagnostic Procedures69Nuclear Medicine Sum of intrinsic resolution and the collimator resolution Intrinsic resolution depends on the positioning of the scintillation events (detector thickness, number of PM-tubes, photon energy) Collimator resolution depends on the collimator geometry (size, shape and length of the holes) SPATIAL RESOLUTION 70. Part 7. Medical Exposure Diagnostic Procedures70Nuclear Medicine Object Image Intensity SPATIAL RESOLUTION 71. Part 7. Medical Exposure Diagnostic Procedures71Nuclear Medicine Resolution - distanceResolution - distance 0 5 10 15 20 25 30 0 2 4 6 8 10 12 14 16 Distance (cm) FWHM(mm) High sensitivity High resolution FWHM 72. Part 7. Medical Exposure Diagnostic Procedures72Nuclear Medicine Optimal Large distance SPATIAL RESOLUTION - DISTANCE 73. Part 7. Medical Exposure Diagnostic Procedures73Nuclear Medicine Linearity 74. Part 7. Medical Exposure Diagnostic Procedures74Nuclear Medicine NON UNIFORMITYNON UNIFORMITY 75. Part 7. Medical Exposure Diagnostic Procedures75Nuclear Medicine NON UNIFORMITYNON UNIFORMITY Cracked crystal 76. Part 7. Medical Exposure Diagnostic Procedures76Nuclear Medicine NON-UNIFORMITYNON-UNIFORMITY (Contamination of collimator) 77. Part 7. Medical Exposure Diagnostic Procedures77Nuclear Medicine NON UNIFORMITYNON UNIFORMITY RING ARTRING ARTIIFACTSFACTS Good uniformity Bad uniformity Difference 78. Part 7. Medical Exposure Diagnostic Procedures78Nuclear Medicine NON-UNIFORMITYNON-UNIFORMITY Defect collimator 79. Part 7. Medical Exposure Diagnostic Procedures79Nuclear Medicine COUNT RATE PERFORMANCECOUNT RATE PERFORMANCE (IAEA QC Atlas) 80. Part 7. Medical Exposure Diagnostic Procedures80Nuclear Medicine Spatial positioning at differentSpatial positioning at different energiesenergies Intrinsic spatial resolution with Ga-67 Point source (count rate < 20k cps); quadrant bar pattern; 3M counts; preset energy window widths; summed image from energy windows set over the 93 keV, 183 keV and 296 keV photopeaks. (IAEA QC Atlas) 81. Part 7. Medical Exposure Diagnostic Procedures81Nuclear Medicine Spatial positioning atSpatial positioning at different energiesdifferent energies 82. Part 7. Medical Exposure Diagnostic Procedures82Nuclear Medicine CENTER OF ROTATIONCENTER OF ROTATION 83. Part 7. Medical Exposure Diagnostic Procedures83Nuclear Medicine Tilted detectorTilted detector 84. Part 7. Medical Exposure Diagnostic Procedures84Nuclear Medicine Scattered radiationScattered radiation photon electron Scattered photon 85. Part 7. Medical Exposure Diagnostic Procedures85Nuclear Medicine The amount of scattered photonsThe amount of scattered photons registeredregistered Patient size Energy resolution of the gammacamera Window setting 86. Part 7. Medical Exposure Diagnostic Procedures86Nuclear Medicine PATIENT SIZEPATIENT SIZE 87. Part 7. Medical Exposure Diagnostic Procedures87Nuclear Medicine Pulse height distributionPulse height distribution Energy Counts 0 20 40 60 80 100 120 140 20 60 100 120 140 160 Tc99m Full energy peak Scattered photonsThe width of the full energy peak (FWHM) is determined by the energy resolution of the gamma camera. There will be an overlap between the scattered photon distribution and the full energy peak, meaning that some scattered photons will be registered. FWHM Overlapping area 88. Part 7. Medical Exposure Diagnostic Procedures88Nuclear Medicine Window widthWindow width 20% 10%40% Increased window width will result in an increased number of registered scattered photons and hence a decrease in contrast 89. Part 7. Medical Exposure Diagnostic Procedures89Nuclear Medicine SCATTER CORRECTIONSCATTER CORRECTION 90. Part 7. Medical Exposure Diagnostic Procedures90Nuclear Medicine -20 -15 -10 -5 0 0 20 40 60 80 100 120 140 Register 1000 counts Origin of counts ATTENUATION I=I0 exp(-x) 91. Part 7. Medical Exposure Diagnostic Procedures91Nuclear Medicine Contrast (2cm object) 23% 7% 2% ATTENUATION 92. Part 7. Medical Exposure Diagnostic Procedures92Nuclear Medicine ATTENUATION CORRECTIONATTENUATION CORRECTION 93. Part 7. Medical Exposure Diagnostic Procedures93Nuclear Medicine ATTENUATION CORRECTIONATTENUATION CORRECTION Transmission measurements Sealed source CT 94. Part 7. Medical Exposure Diagnostic Procedures94Nuclear Medicine ATTENUATION CORRECTIONATTENUATION CORRECTION Ficaro et al Circulation 93:463-473, 1996 95. Part 7. Medical Exposure Diagnostic Procedures95Nuclear Medicine Count density NOISE 96. Part 7. Medical Exposure Diagnostic Procedures96Nuclear Medicine Gamma cameraGamma camera Operational considerations Collimator selection Collimator mounting Distance collimator-patient Uniformity Energy window setting Corrections (attenuation, scatter) Background Recording system Type of examination 97. Part 7. Medical Exposure Diagnostic Procedures97Nuclear Medicine Acceptance Daily Weekly Yearly Uniformity P T T P Uniformity, tomography P P Spectrum display P T T P Energy resolution P P Sensitivity P T P Pixel size P T P Center of rotation P T P Linearity P P Resolution P P Count losses P P Multiple window pos P P Total performance phantom P P P: physicist, T:technician QC GAMMA CAMERA 98. Part 7. Medical Exposure Diagnostic Procedures98Nuclear Medicine IAEA-TECDOC-602 Quality control of Nuclear medicine instruments 1991 INTERNATIONAL ATOMIC ENERGY AGENCY IAEA May 1991 99. Part 7. Medical Exposure Diagnostic Procedures99Nuclear Medicine QC Gamma cameraQC Gamma camera 100. Part 7. Medical Exposure Diagnostic Procedures100Nuclear Medicine Energy resolutionEnergy resolution 101. Part 7. Medical Exposure Diagnostic Procedures101Nuclear Medicine LinearityLinearity Flood source or point source (Tc-99m) Bar phantom or orthogonal-hole phantom 1. Subjective evaluation of the image. 2. Calculate absolute (AL) and differential (DL) linearity. AL: Maximum displacement from ideal grid (mm) DL: Standard deviation of displacements (mm) 102. Part 7. Medical Exposure Diagnostic Procedures102Nuclear Medicine Flood source (Tc-99m, Co-57) Point source (Tc-99m) Intrinsic uniformity: Point source at a large distance from the detector. Acquire an image of 10.000.000 counts. With collimator: Flood source on the collimator. Acquire an image of 10.000.000 counts. UNIFORMITY 103. Part 7. Medical Exposure Diagnostic Procedures103Nuclear Medicine UniformityUniformity 1. Subjective evaluation of the image 2. Calculate Integral uniformity (IU) Differential uniformity (DU) IU=(Max-Min)/Max+Min)*100, where Max is the the maximum and Min is the minimum counts in a pixel. DU=(Hi-Low)/(Hi+Low)*100, where Hi is the highest and Low is the lowest pixel value in a row of 5 pixels moving over the field of view. Matrix size 64x64 or 128x128 104. Part 7. Medical Exposure Diagnostic Procedures104Nuclear Medicine UNIFORMITY/DIFFERENTUNIFORMITY/DIFFERENT RADIONUCLIDESRADIONUCLIDES D BOULFELFEL Dubai Hospital All 4 images acquired with: Matrix: 256 x 256, # counts: 30 Mcounts Tl 201 Ga 67 Tc 99m I 131 105. Part 7. Medical Exposure Diagnostic Procedures105Nuclear Medicine LINEARITY AND UNIFORMITYLINEARITY AND UNIFORMITY CORRECTIONSCORRECTIONS Dogan Bor, Ankara 106. Part 7. Medical Exposure Diagnostic Procedures106Nuclear Medicine OFF PEAK MEASUREMENTSOFF PEAK MEASUREMENTS Dogan Bor, Ankara 107. Part 7. Medical Exposure Diagnostic Procedures107Nuclear Medicine TOMOGRAPHIC UNIFORMITYTOMOGRAPHIC UNIFORMITY Tomographic uniformity is the uniformity of the reconstruction of a slice through a uniform distribution of activity. SPECT phantom with 200-400 MBq Tc99m aligned with the axis of rotation. Acquire 250k counts per angle. Reconstruct the data with a ramp filter. 108. Part 7. Medical Exposure Diagnostic Procedures108Nuclear Medicine INCORRECT MEASUREMENTINCORRECT MEASUREMENT Two images of a flood source filled with a solution of Tc-99m, which had not been mixed properly 109. Part 7. Medical Exposure Diagnostic Procedures109Nuclear Medicine Spatial resolutionSpatial resolution Measured with: Flood source or point source plus a Bar phantom Subjective evaluation of the image 110. Part 7. Medical Exposure Diagnostic Procedures110Nuclear Medicine SPATIAL RESOLUTIONSPATIAL RESOLUTION Lead 200 mm 50 mm Screw clip Polyethylene tubing about 0.5 mm in internal diameter Plastic shims 500 mm Rigid plastic 30 mm 60 mm 5 mm Intrinsic resolution System resolution IAEA TECDOC 602 111. Part 7. Medical Exposure Diagnostic Procedures111Nuclear Medicine Tc-99m or other radionuclide in use Intrinsic: Collimated line source on the detector System: Line source at a certain distance Calculate FWHM of the line spread function FWHM: 7.9 mm SPATIAL RESOLUTION 112. Part 7. Medical Exposure Diagnostic Procedures112Nuclear Medicine TOMOGRAPHIC RESOLUTIONTOMOGRAPHIC RESOLUTION Method 1: Measurement with the Jaszczak phantom, with and without scatter (phantom filled with water and with no liquid) Method 2: Measurement with a Point or line source free in air and Point or line source in a SPECT phantom with water 113. Part 7. Medical Exposure Diagnostic Procedures113Nuclear Medicine SensitivitySensitivity Expressed as counts/min/MBq andExpressed as counts/min/MBq and should be measured for each collimatorshould be measured for each collimator Important to observe with multi-headImportant to observe with multi-head systems that variations among heads dosystems that variations among heads do not exceed 3%not exceed 3% 114. Part 7. Medical Exposure Diagnostic Procedures114Nuclear Medicine 115. Part 7. Medical Exposure Diagnostic Procedures115Nuclear Medicine Multiple Window SpatialMultiple Window Spatial RegistrationRegistration Performed to verify that contrast isPerformed to verify that contrast is satisfactory for imaging radionuclides,satisfactory for imaging radionuclides, which emit photons of more than onewhich emit photons of more than one energy (e.g. Tl-201, Ga-67, In-111, etc.)energy (e.g. Tl-201, Ga-67, In-111, etc.) as well as in dual radionuclides studiesas well as in dual radionuclides studies 116. Part 7. Medical Exposure Diagnostic Procedures116Nuclear Medicine Multiple Window SpatialMultiple Window Spatial RegistrationRegistration Collimated Ga-67Collimated Ga-67 sources are used atsources are used at central point, four pointscentral point, four points on the X-axis and fouron the X-axis and four points on the Y axispoints on the Y axis Perform acquisitions forPerform acquisitions for the 93, 184 and 300the 93, 184 and 300 keV energy windowskeV energy windows Displacement of countDisplacement of count centroids from eachcentroids from each peak is computed andpeak is computed and maximum is retained asmaximum is retained as MWSR in mmMWSR in mm 117. Part 7. Medical Exposure Diagnostic Procedures117Nuclear Medicine Count Rate PerformanceCount Rate Performance Performed to ensure that the time toPerformed to ensure that the time to process an event is sufficient toprocess an event is sufficient to maintain spatial resolution andmaintain spatial resolution and uniformity in clinical images acquired atuniformity in clinical images acquired at high-count rateshigh-count rates 118. Part 7. Medical Exposure Diagnostic Procedures118Nuclear Medicine Count Rate PerformanceCount Rate Performance Use of decayingUse of decaying source or calibratedsource or calibrated copper sheets tocopper sheets to compute thecompute the observed count rateobserved count rate for a 20% countfor a 20% count loss and theloss and the maximum countmaximum count rate without scatterrate without scatter 119. Part 7. Medical Exposure Diagnostic Procedures119Nuclear Medicine Pixel sizePixel size 120. Part 7. Medical Exposure Diagnostic Procedures120Nuclear Medicine Center of rotationCenter of rotation Point source of Tc-99m or Co-57 Make a tomographic acquisition In x-direction the position will describe a sinus- function. In y-direction a straight line. Calculate the offset from a fitted cosine and linear function at each angle. Cosine function Linear function 121. Part 7. Medical Exposure Diagnostic Procedures121Nuclear Medicine Total performance phantom. Emission or transmission. Compare result with reference image. Total performance 122. Part 7. Medical Exposure Diagnostic Procedures122Nuclear Medicine SOURCES FORSOURCES FOR QC OF GAMMA CAMERASQC OF GAMMA CAMERAS Point source Collimated line source Line source Flood source Tc99m, Co57, Ga67