volumetric modulated arc therapy patient specific...

2012 AAPM Annual Meeting, Charlotte2012 AAPM Annual Meeting, Charlotte

Volumetric Modulated Arc TherapyVolumetric Modulated Arc Therapy--

Patient Specific QA Patient Specific QA

Daliang Cao, PhD, DABR

Swedish Cancer Institute, Seattle, WA


VMAT plan QA methodsVMAT plan QA methods

Film & ion chamberFilm & ion chamber

diode array diode array

MapcheckMapcheck in in MapPhanMapPhan phantomphantom

ArcCheckArcCheck

Delta4Delta4

2D ion chamber array 2D ion chamber array

MatriXXMatriXX in MULTICube phantomin MULTICube phantom

PTW 729 in PTW 729 in OctaviusOctavius phantomphantom

Composite dose measurement Fluence measurement

2D ion chamber array2D ion chamber array

MatriXXMatriXX mounted on Gantrymounted on Gantry

Portal Portal dosimetrydosimetry


Which system do you use/intend to use Which system do you use/intend to use in your clinic for VMAT QAin your clinic for VMAT QA

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A.A. Film & ion chamberFilm & ion chamber

B.B. Ion chamber array (Ion chamber array (MatriXXMatriXX, PTW 729), PTW 729)

C.C. Diode array (Diode array (mapcheckmapcheck, , ArcCheckArcCheck, Delta4), Delta4)

D.D. Portal Portal dosimetrydosimetry

E.E. othersothers


Film & Ion ChamberFilm & Ion Chamber

A stack of solid water phantom with a total thickness of 15cm.A stack of solid water phantom with a total thickness of 15cm.A 0.6cc farmer chamber was inserted at the depth of 10cm.A 0.6cc farmer chamber was inserted at the depth of 10cm.A film was sandwiched 1cm above the ion chamber. A film was sandwiched 1cm above the ion chamber.


Prostate CaseProstate Case

Plan Measurement

Ion Chamber measurement is 1.3% below the predicted value


H&N CaseH&N Case


H&N Case: absolute dose comparisonH&N Case: absolute dose comparison

The Gamma analysis passing rate in this case is 96.4%The Gamma analysis passing rate in this case is 96.4%The measured ion chamber dose was 0.2% more than the planned oneThe measured ion chamber dose was 0.2% more than the planned one

measurement plan


2D Diode Array2D Diode Array

A MapCheck device inserted into a A MapCheck device inserted into a MapPhanMapPhan solid water phantomsolid water phantom


MapCheck in MapCheck in MapPhanMapPhan QA resultQA result

With 3% and 3mm criteria, the gamma analysis passing rate is 96.With 3% and 3mm criteria, the gamma analysis passing rate is 96.5%5%Dose threshold in gamma analysis is 10%Dose threshold in gamma analysis is 10%


Dose Rate DependencyDose Rate Dependency

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Mapcheck diode

MatriXX ion chamber

The variation of dose response with the dose rate can reach up to 2.5% for MapCheck diode.


Calibrate MapCheck with medium dose rateCalibrate MapCheck with medium dose rate

Gamma passing rate increased to 98.8%Gamma passing rate increased to 98.8%

Dose calibration was performed at 224 MU/Min


Angular dose response of MapCheck Angular dose response of MapCheck diodediode

Significant variation of the dose response can be found when theSignificant variation of the dose response can be found when the incidence incidence beam angle is parallel to the detector plane.beam angle is parallel to the detector plane.Each diode in MapCheck may have different angular dose response Each diode in MapCheck may have different angular dose response curve. curve.

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1386 diode detectors arranged in cylindrical geometry1386 diode detectors arranged in cylindrical geometry

Measures entrance and exit doseMeasures entrance and exit dose

The QA can be done in composite or per control point The QA can be done in composite or per control point

Arc Check Arc Check –– Sun NuclearSun Nuclear


ArcCHECKArcCHECK features a versatile central cavityfeatures a versatile central cavity

–– May be used to accommodate different detectors and insertsMay be used to accommodate different detectors and inserts

–– MultiPlugMultiPlug (left) also accommodates EBT film cassette and (left) also accommodates EBT film cassette and multiple detector locationsmultiple detector locations

Central Cavity OptionsCentral Cavity Options


SNC Patient SoftwareSNC Patient Software

Software enables composite and control point analysisSoftware enables composite and control point analysis

DICOM RT Dose is imported and DICOM RT Dose is imported and ArcCHECKArcCHECK software then extracts 3D software then extracts 3D dose corresponding to detector locations, and performs a comparidose corresponding to detector locations, and performs a comparisonson

All data files from All data files from ArcCHECKArcCHECK are open format for easy exportare open format for easy export

–– Raw data also available for exportRaw data also available for export


ArcCheckArcCheck QA resultQA result

Gamma analysis passing rate is 95.2% for this case.


Virtual InclinometerVirtual Inclinometer


3DVH Option3DVH Option

The most advanced 3D patient dose and DVH tools availableThe most advanced 3D patient dose and DVH tools available

–– Uses existing Uses existing ArcCHECKArcCHECK measurementsmeasurements

–– Supports VMAT and Supports VMAT and RapidArcRapidArc deliveriesdeliveries

–– No secondary dose calculation algorithmNo secondary dose calculation algorithm

–– 3D dose and DVH analysis on 3D dose and DVH analysis on patientpatient geometry (not phantom geometry (not phantom geometry)geometry)


ScandidosScandidos DeltaDelta 44

A cylinder-shaped plastic phantom with 2 imbedded orthogonal crossing detector planes.1069 diode detectorsDose is recorded in 2 planes and a 3D dose is reconstructed for comparison with the QA plan.


CompositeComposite--level analysis of level analysis of SmartArc plan with DeltaSmartArc plan with Delta44


MatriXXMatriXX & MULTICube phantom& MULTICube phantom

MatriXX system has 1020 vented ion chambers with an active area MatriXX system has 1020 vented ion chambers with an active area of of 24.4cm x 24.4cm.24.4cm x 24.4cm.

The size of each ion chamber is 4.5cm (diameter) x 5cm (height).The size of each ion chamber is 4.5cm (diameter) x 5cm (height). The raw The raw pixel size is 7.62mm, which can be interpolated down to 1mm.pixel size is 7.62mm, which can be interpolated down to 1mm.

Laser is used to align system. Dose from both coronal and Laser is used to align system. Dose from both coronal and sagittalsagittal planes planes can be measured depending on the phantom.can be measured depending on the phantom.


MatriXX data conversionMatriXX data conversion

The raw image has only 1024 pixels with 7.62mm dose grid. The daThe raw image has only 1024 pixels with 7.62mm dose grid. The data set can be interpolated to ta set can be interpolated to 1mm dose grid.1mm dose grid.

linear

Cubic Spline


Results: Prostate CaseResults: Prostate Case

With 3% and 3mm criteria, the passing rate is 99% for this coronWith 3% and 3mm criteria, the passing rate is 99% for this coronal sliceal slice

measurement plan


MatriXX QA: H&N CaseMatriXX QA: H&N Case

measurement plan

With 3% and 3mm criteria, the passing rate is 98.2% for this corWith 3% and 3mm criteria, the passing rate is 98.2% for this coronal sliceonal sliceNo dose threshold was applied in gamma analysis. Note the passinNo dose threshold was applied in gamma analysis. Note the passing rate reduces to 97.1% g rate reduces to 97.1% if a 10% threshold is applied. if a 10% threshold is applied.


Angular variation of dose responseAngular variation of dose response

Up to 8% dose variation can be found when the photon beam is parUp to 8% dose variation can be found when the photon beam is parallel to the detector allel to the detector planeplane

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MatriXX EvolutionMatriXX Evolution

The gantry angle for each frame is recorded during the VMAT deliThe gantry angle for each frame is recorded during the VMAT delivery.very.

A angular dose response correction is applied to all the data baA angular dose response correction is applied to all the data based on the sed on the gantry angle information.gantry angle information.

InclinometerInput


With and Without Angular response With and Without Angular response correctioncorrection

The measured data without angular dose response The measured data without angular dose response correction is slightly colder than the one with correction.correction is slightly colder than the one with correction.

PlanMeasurement

Without CorrectionMeasurement

With Correction

A two-arc case: H&N


With and Without Angular response With and Without Angular response correctioncorrection

3% and 3mm passing criteria for Gamma analysis.3% and 3mm passing criteria for Gamma analysis.

Without Correction81.9%

With Correction96.2%


Which of the following cannot be Which of the following cannot be measured using measured using MatriXXMatriXX 2D ion chamber 2D ion chamber

arrayarray

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A.A. Dose distribution on a Dose distribution on a sagittalsagittal planeplane

B.B. Absolute dose at detector centerAbsolute dose at detector center

C.C. Dose distribution on a coronal planeDose distribution on a coronal plane

D.D. Dose distribution on a transverse plane Dose distribution on a transverse plane

E.E. Radiation Radiation fluencefluence of a VMAT planof a VMAT plan


AnswerAnswer

A.A. Dose distribution on a Dose distribution on a sagittalsagittal planeplane

B.B. Absolute dose at detector centerAbsolute dose at detector center

C.C. Dose distribution on a coronal planeDose distribution on a coronal plane

D.D. Dose distribution on a transverse plane Dose distribution on a transverse plane

E.E. Radiation Radiation fluencefluence of a VMAT planof a VMAT plan


Portal Portal DosimetryDosimetry

Portal Dosimetry Process

Created verification plan for each patient

Calibrated panel prior to collecting data

Data measured in units of CU

Definition of Calibrated Unit (CU)Field Size =10 x 10 cm2SDD = 105 cmDeliver 100 MU to panelSet reading = 1 CU1 CU is numerically approximate to 1 Gy


Portal Portal DosimetryDosimetry –– RapidArcRapidArc (Prostate)(Prostate)


Portal Portal DosimetryDosimetry –– RapidArcRapidArc (HN)(HN)


Which QA system has the highest Which QA system has the highest resolutionresolution

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A.A. portal portal dosimetrydosimetry using EPIDusing EPID

B.B. filmfilm

C.C. MatriXXMatriXX 2D ion chamber array2D ion chamber array

D.D. ArcCheckArcCheck

E.E. Delta4Delta4


AnswerAnswer

A.A. portal portal dosimetrydosimetry using EPIDusing EPID

B.B. filmfilm

C.C. MatriXXMatriXX 2D ion chamber array2D ion chamber array

D.D. ArcCheckArcCheck

E.E. Delta4Delta4


SummarySummary

VMAT QA using film and ion chamber is easy to setup and perform.VMAT QA using film and ion chamber is easy to setup and perform.However, there is no instantaneous result and It is timeHowever, there is no instantaneous result and It is time--consuming consuming for data analysis.for data analysis.

DiodeDiode--array and ionarray and ion--chamberchamber--array based devices can provide array based devices can provide instantaneous data analysis and can be used for VMAT patient instantaneous data analysis and can be used for VMAT patient specific QA once the angular dose response and dose rate specific QA once the angular dose response and dose rate dependence is considered during data analysis/collection.dependence is considered during data analysis/collection.

Portal Portal dosimetrydosimetry can provide an easy and robust way for patient can provide an easy and robust way for patient specific QA. The only issue with this technique is that informatspecific QA. The only issue with this technique is that information on ion on gantry angle cannot be checked independently. gantry angle cannot be checked independently.

Users need to know limit of each QA technique/device for best Users need to know limit of each QA technique/device for best patient specific QA result.patient specific QA result.


AcknowledgementAcknowledgement

David M. Shepard, Ph.D.David M. Shepard, Ph.D.

Muhammad K. N. Afghan, Ph.D.Muhammad K. N. Afghan, Ph.D.

Fan Chen, Ph.D.Fan Chen, Ph.D.

Min Rao, Ph.D.Min Rao, Ph.D.

Jinsong Ye, M.S.Jinsong Ye, M.S.

Tony P. Wong, Ph.D.Tony P. Wong, Ph.D.

Vivek Mehta, M.D.Vivek Mehta, M.D.

David HousleyDavid Housley

Grace KimGrace Kim

Igor Gomola, Ph.D.Igor Gomola, Ph.D.

Gerry Gerry VantellingenVantellingen

Jie Shi, Ph.D.Jie Shi, Ph.D.

Kris LyleKris Lyle


Thank you!Thank you!

volumetric modulated arc therapy patient specific...

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