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Characterization, Commissioning and Evaluation of Delta4 IMRT

QA System

Ram Sadagopan1UTMD Anderson Cancer Center Houston, TX.

Characterization, Commissioning and Characterization, Commissioning and Evaluation of DeltaEvaluation of Delta44 IMRT IMRT

QA SystemQA System

Ram Sadagopan1UTMD Anderson Cancer Center Houston, TX.

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Acknowledgements

• Collaborators: • Jose Bencomo, Rafael. M. Landrove, Peter

Balter, Sastry Vedam and Görgen Nilsson• Core Physics group at MDACC for their

support

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IntroductionIntroductionIntroduction

• IMRT dose distribution is complex and requires QA

• Current IMRT QA provides limited points and planes and the Gamma analysis is only 2D

• Labor intensive

• Leaves voids in the evaluation of plan and its delivery

• Field by Field and Segment by Segment analysis is typically not possible

• Does not readily extend to 4D

Question: Does the DELTA4 system potentially address these drawbacks?

•• IMRT dose distribution is complex and requires QAIMRT dose distribution is complex and requires QA

•• Current IMRT QA provides limited points and planes and the Current IMRT QA provides limited points and planes and the Gamma analysis is only 2DGamma analysis is only 2D

• Labor intensive

• Leaves voids in the evaluation of plan and its delivery

• Field by Field and Segment by Segment analysis is typically not possible

• Does not readily extend to 4D

Question: Does the DELTA4 system potentially address these drawbacks?

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4

Delta4 Device Fully AssembledDeltaDelta44 Device Fully AssembledDevice Fully Assembled

Currently commercially availableCurrently commercially available

ElectrometersElectrometersElectrometers

2D diode Arrays2D diode Arrays2D diode Arrays

Power, Synchronization and

Data Cables

Power, Power, Synchronization and Synchronization and

Data CablesData Cables

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2D Detector Arrays Units2D Detector2D Detector Arrays UnitsArrays Units

• Main Unit

• Detection Area 20x20 cm2

• Sensitivity 5nC/Gy

• Wing Unit

•• Main Main UnitUnit

•• Detection Area 20x20 cmDetection Area 20x20 cm22

•• Sensitivity 5nC/GySensitivity 5nC/Gy

•• WingWing UnitUnit

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Detector ArraysDetector ArraysDetector ArraysArea: 0.78 mmArea: 0.78 mm22

Height: 0.05 mmHeight: 0.05 mm

55• p-diodes in absolute dose

mode• High spatial resolution• 5 mm spacing at center• 10 mm spacing at periphery• 1069 diodes

•• pp--diodes in absolutediodes in absolute dose dose modemode

•• HighHigh spatial spatial resolutionresolution•• 55 mm spacing at centermm spacing at center•• 1010 mm spacing at peripherymm spacing at periphery•• 1069 diodes1069 diodes

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n - type

p - type

Phys. Med. Biol., 1987, Vol. 32, No 9, 1109-1117. 66

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Phys. Med. Biol., 1987, Vol. 32, No 9, 1109-1117.

n - type

p -type

General specifications for silicon semiconductors for use in radiation dosimetry

G. Rikner and E. Grussell 77

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Power Distribution SystemPower Distribution SystemPower Distribution System

• Provides each detector unitwith power

• Provides (external) synchronization signals to detector units

•• ProvidesProvides each detectoreach detector unitunitwith with powerpower

•• ProvidesProvides ((externalexternal) ) synchronizationsynchronization signalssignals to to detector unitsdetector units

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Pulse by Pulse MeasurementsPulse by Pulse MeasurementsPulse by Pulse Measurements

• Segment by Segment and 4D measurements possible

• Approximate pulse separation is 3ms and width is 3ms

• No measurement between pulses, results in a high signal to noise ratio

•• Segment by Segment Segment by Segment and 4D measurements and 4D measurements possible possible

•• Approximate pulse Approximate pulse separation is 3ms and separation is 3ms and width is 3mswidth is 3ms

•• No measurement No measurement between pulses, results between pulses, results in a high signal to noise in a high signal to noise ratioratio

• All diodes readings are recorded with time stamp and reset after each pulse

•• All diodes readings are All diodes readings are recorded with time stamp recorded with time stamp and reset after each pulseand reset after each pulse

Trig Pulse Dose Pulse

999

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Characterization MeasurementsCharacterization MeasurementsCharacterization Measurements

• Precision • Stability• Linearity• Dose rate (pulse rate) dependence• Dose per pulse rate dependence• Beam directional dependence• Energy dependence• Interpolation at non detector location• Sensitivity change – about 1% kGy

•• Precision Precision •• StabilityStability•• LinearityLinearity•• Dose rate (pulse rate) dependenceDose rate (pulse rate) dependence•• Dose per pulse rate dependenceDose per pulse rate dependence•• Beam directional dependenceBeam directional dependence•• Energy dependenceEnergy dependence•• Interpolation at non detector locationInterpolation at non detector location•• Sensitivity change Sensitivity change –– about 1% kGyabout 1% kGy

101010

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ResultsResultsResults

• Precision– 1σ = 0.1%, Range from 0 to 1% measured

exposing single field 10 times in a 6 MV beam

• Stability– 1σ = 0.6%, Range from 0 to 0.5% (Five

measurements of 4 Field box distribution over a 3 month period)

No ion chamber measurements are necessary

•• PrecisionPrecision–– 11σσ = 0.1%, Range from 0 to 1%= 0.1%, Range from 0 to 1% measured measured

exposing single field 10 times in a 6 MV exposing single field 10 times in a 6 MV beambeam

•• StabilityStability–– 11σσ = 0.6%, Range from 0 to 0.5% (Five = 0.6%, Range from 0 to 0.5% (Five

mmeasurements of 4 Field box distribution easurements of 4 Field box distribution over a 3 month period)over a 3 month period)

No ion chamber measurements are necessaryNo ion chamber measurements are necessary

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LinearityLinearityLinearity

Dose response of the central detector from 50 to 1000 MUDose response of the central detector from 50 to 1000 MUDose response of the central detector from 50 to 1000 MU

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y = 0.8632x + 0.0556R2 = 1

0

100

200

300

400

500

600

700

800

900

1000

0 200 400 600 800 1000 1200MU

Rea

ding

200 400 600 800 1000 12000

100200300400

500600700

800900

1000

Rea

ding

MU

R2 = 1y = 0.8632 x + 0.0556

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Dose Rate DependenceDose Rate DependenceDose Rate Dependence 131313

y = 86R2 = 1

40.0

50.0

60.0

70.0

80.0

90.0

100.0

0 100 200 300 400 500 600 700

MU/min

Rea

ding

Dose rate (Pulse rate) dependence: Negligible Dose rate (Pulse rate) dependence: Negligible from 100 MU/min to 600 MU/minfrom 100 MU/min to 600 MU/min

100 200200 300 400 500 600 700

MU/minMU/min0

40

50

60

70

80

90

100

Rea

ding

y = 86 R2 = 1

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Dose per Pulse DependenceDose per Pulse DependenceDose per Pulse Dependence 141414

y = 0.0174x + 0.981R2 = 0.0548

0.96

0.98

1.00

1.02

1.04

0.0000 0.1000 0.2000 0.3000 0.4000

Dose per pulse (mGy/pulse)

Rea

ding

per

Dos

e (R

dg/c

Gy)

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Directional dependence 6 MV beamDirectional dependence 6 MV beamDirectional dependence 6 MV beam 151515

80.0

90.0

100.0

110.0

0 90 180 270 360

Beam angle with respect to main detector plane

Res

pons

e (1

00%

@ 6

0 de

gr

RangeRange ±± 2.5 %2.5 %

Beam angle with respect to main detector plane (degrees)Beam angle with respect to main detector plane (degrees)

180900 270

NormalizationNormalization: : 100 % at 60 100 % at 60

degreesdegrees

36080

110

100

90 Res

pons

e (%

)R

espo

nse

(%)

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Response to Scatter and Leakage Radiation

Response to Scatter and Leakage Radiation

0.0380.0360.0410.045211x1110 X 10

0.0130.0170.0130.016-10x10MLC Leakage

0.1000.0900.0800.080111x1110 X 10

0.0190.0180.0200.02025 X 54 X 4

0.0600.0600.0400.05015 X 54 X 4

Lo Signal0.009Lo Signal0.00923 X 32 X 2

0.0400.0400.0200.03013 X 32 X 2

IC CC04 18 MV

DELTA4

18 MVIC CC04

6 MVDELTA4

6 MVDIST.

FieldEdgeJAW FSMLC FS

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CommissioningCommissioningCommissioning

• Absolute dose calibration against calibrated Farmer Type ion chamber in plastic-slab phantom

• Relative dose calibration in a stable beam

• Network, PC and interface with R&V system configuration (if needed)

• Configuring export (from TPS) and import(into Delta4) of DICOM RT and RTOG formatted files

•• Absolute dose calibration against Absolute dose calibration against calibrated Farmer Type ion chamber in calibrated Farmer Type ion chamber in plasticplastic--slab phantomslab phantom

•• Relative dose calibration in a stable beamRelative dose calibration in a stable beam

•• Network, PC and interface with R&V Network, PC and interface with R&V system configuration (if needed) system configuration (if needed)

•• Configuring Configuring exportexport (from TPS) and (from TPS) and importimport(into Delta(into Delta44) of DICOM RT and RTOG ) of DICOM RT and RTOG formatted filesformatted files

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EvaluationEvaluationEvaluation

• IMRT QA on Thirteen patient plans (HN, CNS, Thoracic, Gyn, GU and GI)

• Plans with Non coplanar beams were also measured

• All plans passed the criteria of Gamma (5% or 5mm) ≤ 1 for more than 97% of points

• Representative analysis presented

•• IMRT QA on Thirteen patient plans IMRT QA on Thirteen patient plans (HN, CNS, Thoracic, Gyn, GU and GI)(HN, CNS, Thoracic, Gyn, GU and GI)

•• Plans with Non coplanar beams were Plans with Non coplanar beams were also measuredalso measured

•• All plans passed the criteria of Gamma All plans passed the criteria of Gamma (5% or 5mm) (5% or 5mm) ≤≤ 1 for 1 for more than more than 97% of 97% of pointspoints

•• Representative analysis presentedRepresentative analysis presented

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Delta4 Software 3D ViewDeltaDelta44 Software 3D ViewSoftware 3D View

NormNormNorm

Software provides information onSoftware provides information on IMRT QA StatisticsIMRT QA Statistics

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Visualization of BEV MLC DeviationsVisualization of BEV MLC DeviationsVisualization of BEV MLC Deviations

Dose Comparison Dose Comparison 3D3DInteractiveInteractiveInteractive

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Dose comparison in 2D and Interactive Dose comparison in 2D and Interactive StatisticsStatistics

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Software allows for Profile Comparison –Composite Dose

Software allows for Profile Comparison Software allows for Profile Comparison ––Composite DoseComposite Dose 232323

Planned 90% iso dose line

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ConclusionsConclusions

• Accurate and Precise.

• It is an integrated 3D system with analysis software

• Timeliness: QA prior to treatment

• Powerful: Field by Field and Segment by Segment analysis, display of anatomical contours over the measured distribution

• Efficiency and convenience of central database

• Extension to 4D

Delta4 system does address the drawbacks in the current QA system

•• Accurate and Precise.Accurate and Precise.

•• It is an integrated 3D system with analysis softwareIt is an integrated 3D system with analysis software

•• Timeliness: QA prior to treatmentTimeliness: QA prior to treatment

•• Powerful: Field by Field and Segment by Segment Powerful: Field by Field and Segment by Segment analysis, display of anatomical contours over the analysis, display of anatomical contours over the measured distributionmeasured distribution

•• Efficiency and convenience of central databaseEfficiency and convenience of central database

•• Extension to 4DExtension to 4D

DeltaDelta44 system does address the drawbacks system does address the drawbacks in the current QA systemin the current QA system

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Future Work

• Research possibilities - RPC Head and Neck phantom

• Future work - Breast phantom, 4D lung phantom, Independent algorithm to verify the interpolation method used here, etc.

Future WorkFuture Work

•• Research possibilities Research possibilities -- RPC Head and Neck RPC Head and Neck phantomphantom

•• Future work Future work -- Breast phantom, 4D lung Breast phantom, 4D lung phantom, Independent algorithm to verify phantom, Independent algorithm to verify the interpolation method used here, etc.the interpolation method used here, etc.

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