Volumetric Modulated Arc Therapy Planning & QAchapter.aapm.org/pennohio/2012FallSympPresentations/Cao...1386 diode detectors arranged in cylindrical geometry Measures entrance and

2012 Penn2012 Penn--Ohio AAPM Chapter Ohio AAPM Chapter Fall Symposium, ClevelandFall Symposium, Cleveland

Volumetric Modulated Arc TherapyVolumetric Modulated Arc Therapy--

Planning & QA Planning & QA

Daliang Cao, PhD, DABR

Swedish Cancer Institute, Seattle, WA


OutlineOutline

VMAT treatment planningVMAT treatment planning

Comparison between VMAT and Helical TomotherapyComparison between VMAT and Helical Tomotherapy

VMAT machine QA and patient specific QA VMAT machine QA and patient specific QA


VMAT Treatment PlanningVMAT Treatment Planning


Commercial Planning SystemsCommercial Planning Systems

Elekta Ergo++Elekta Ergo++®®

Elekta MonacoElekta Monaco®® VMAT 3.0VMAT 3.0

Elekta MonacoElekta Monaco®® VMAT 3.2VMAT 3.2

Eclipse RapidArcEclipse RapidArc®®

Philips SmartArcPhilips SmartArc®®

ProwessProwess®®

NucletronNucletron -- OncentraOncentra VMATVMAT

anatomy based semi-inverse planning

fluence based planning

aperture based planning


Comparison of Comparison of different inverse planning approaches different inverse planning approaches


A Pancreas CaseA Pancreas Case

Anatomy-based Fluence-based Aperture-based


A Pancreas CaseA Pancreas Case

Thick Solid lines: Anatomy-basedThin Solid lines: Fluence-basedDashed lines: Aperture-based


A H&N CaseA H&N Case

Thin Solid lines: Anatomy-basedThick Solid lines: Fluence-basedDashed lines: Aperture-based


Which Planning System to Choose?Which Planning System to Choose?

The anatomyThe anatomy--based Inverse planning is easy to plan and based Inverse planning is easy to plan and is capable of generating conformal dose distributions for is capable of generating conformal dose distributions for simple cases. However, it may fail to provide a solution simple cases. However, it may fail to provide a solution for more complex cases.for more complex cases.

Both fluenceBoth fluence--based and aperturebased and aperture--based inverse planning based inverse planning approaches can achieve comparable plan qualities for approaches can achieve comparable plan qualities for most of the clinical cases.most of the clinical cases.


Comparison Between VMAT and Helical Comparison Between VMAT and Helical TomotherapyTomotherapy


Lung CaseLung Case

Helical Tomotherapy 1-arc VMAT


Lung CaseLung Case

GTV

PTV

heart

lungcord

Delivery time for VMAT plan was 2’04”

Delivery time for the Tomotherapy plan was 5’44”

Solid lines: VMATDashed lines: Tomo


Prostate CaseProstate Case


PTV1 PTV1

bladder bladderrectum rectum




GTV

PTV1

PTV2

Rectum

BladderFemoralHeads


Delivery time for Tomotherapy plan was 3’31”


Head & Neck Case #1Head & Neck Case #1

Two targets with prescription levels of 5040 and 4500 cGy




Two targets with prescription levels of 5040 and 4500 cGyTwo targets with prescription levels of 5040 and 4500 cGy



Average V95: Tomotherapy = 98.4% and VMAT = 98.6%

Max cord dose: Tomotherapy = 34.4 Gy and VMAT = 21.6 GyMean parotids dose: Tomotherapy = 12.1 GY and VMAT = 12.6 Gy.


GTV

PTV1

PTV2

LT Parotid

RT Parotid

Cord



Delivery time for the Helical Tomotherapy plan was 9’07”


Solid = SmartArc Dashed = Tomotherapy


PTV70

PTV60

PTV66

CordLt. Parotid

Rt. Parotid

PTV50

Lt. Parotid


VMAT provided a 43% reduction in treatment time.


VMAT machine QAVMAT machine QA


VMAT Machine Specific QAVMAT Machine Specific QA

MLC leaf positionMLC leaf position

Gantry angleGantry angle

Dose rateDose rate

The three major variables during VMAT deliveryThe three major variables during VMAT delivery


A special VMAT plan with specific MLC A special VMAT plan with specific MLC leaf motion patterns and dose rate leaf motion patterns and dose rate

variations was developed to check all variations was developed to check all three major variables three major variables

Gantry continue rotates while the MLC leaves are moving.

Dose rate also varies while gantry is rotating.

The plan was measured using a MatriXX 2D ion chamber inserted in a MULTICube phantom.

The data were recorded in movie mode with 0.1 second sampling time.


The VMAT plan for machine QAThe VMAT plan for machine QA

The theoretical dose distribution calculated using convolution/superposition dose engine in Pinnacle. The calculation was done with 1° gantry spacing.


How to check the variablesHow to check the variables

MLC leaf motion: The projection position of the tip for MLC leaf motion: The projection position of the tip for each MLC leaf on the MatriXX device can be used to each MLC leaf on the MatriXX device can be used to determine the MLC leaf motion accuracy.determine the MLC leaf motion accuracy.

Gantry angle: The projection width of the 1cm gap Gantry angle: The projection width of the 1cm gap between MLC leaves on the MatriXX device can be used between MLC leaves on the MatriXX device can be used to determine the gantry angle.to determine the gantry angle.

Dose rate: The absolute dose measured in the open Dose rate: The absolute dose measured in the open area from each 0.1s sample can be used to determine area from each 0.1s sample can be used to determine the actual dose rate.the actual dose rate.


The measurement resultThe measurement result

The measurement was interpolated into 1mm dose grid using cubic splineinterpolation method. The sample time is 0.1 second.


QA ResultsQA Results

The standard deviation of the gantry angle error is 1.0° with a maximum error of 2.6°. The standard deviation of the leaf position error is 1.1mm with a maximum error of 3.1mm in this case.The mean error of the dose rate is 2.7 MU/minutes or 3.2% in relative mode.


VMAT patient specific QAVMAT patient specific QA


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

MatriXX in MULTICube phantomMatriXX in 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


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.



Plan Measurement

Ion Chamber measurement is 1.3% below the predicted value


H&N CaseH&N Case


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

0.975

0.980

0.985

0.990

0.995

1.000

1.005

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00 450.00 500.00

dose rate (MU/minute)

rela

tive

dose

res

pons

e

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.

-10.0

-5.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

-180 -120 -60 0 60 120 180Gantry Angle

Per

cent

Err

or (

%)

180°°°°

90°°°°

0°°°°

-90°°°°

Couch

detector array& phantom

-180°°°°

phantom setup MapCheck Diode MatriXX ion chamber

-10.0

-5.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

-180 -120 -60 0 60 120 180

Gantry Angle

perc

ent e

rro

r (%

)


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.


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


MatriXX & MULTICube phantomMatriXX & 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 sagittLaser is used to align system. Dose from both coronal and sagittal planes al planes can be measured depending on the phantom.can be measured depending on the phantom.


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

180°°°°

90°°°°

0°°°°

-90°°°°

Couch

detector array& phantom

-180°°°°

phantom setup

-10.0

-6.0

-2.0

2.0

6.0

10.0

-180 -120 -60 0 60 120 180Gantry Angle

per

cen

t err

or

(%)


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%


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 (Prostate)(Prostate)


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


SummarySummary

VMAT planning systems using different techniques are available iVMAT planning systems using different techniques are available in n the market. Fluence and aperture based algorithms can provide the market. Fluence and aperture based algorithms can provide better dose distributions than anatomy based algorithm, especialbetter dose distributions than anatomy based algorithm, especially ly for more complex cases.for more complex cases.

VMAT and Helical Tomotherapy provide comparable IMRT plan VMAT and Helical Tomotherapy provide comparable IMRT plan quality. However, VMAT delivery efficiency is much better.quality. However, VMAT delivery efficiency is much better.

The three major variables during VMAT The three major variables during VMAT delivery(gantrydelivery(gantry angle, MLC angle, MLC leaf position and dose rate) should be checked as part of the VMleaf position and dose rate) should be checked as part of the VMAT AT machine specific QA. machine specific QA.

There are many methods/devices available for VMAT patient QA. There are many methods/devices available for VMAT patient QA. 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!


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)


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


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

Documents

Volumetric Modulated Arc Therapy Planning & QAchapter.aapm.org/pennohio/2012FallSympPresentations/Cao...1386 diode detectors arranged in cylindrical geometry Measures entrance and