Monte Carlo -II: Clinical Impact Outline

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Monte Carlo - II: Clinical impactMonte Carlo forElectron Beam Treatment PlanningC-M Charlie Ma, Ph.D.Dept. of Radiation OncologyFox Chase Cancer CenterPhiladelphia, PA 19111Why Use Monte Carlo forRadiotherapy Treatment PlanningAn accuracy of about 5% in dosedelivery is required to effectively treatcertain types of cancers and to reducecomplications.ICRU Reports 24 (1976) and 42 (1988)Outline Current status of electron Monte Carlo Implementation of Monte Carlo for electronbeam treatment planning dose calculations Application of Monte Carlo in conventional andmodulated electron beam therapy Monte Carlo for other beam modalitiesThe Accuracy Requirement forTreatment Planning Dose Calculationσ2 σ2calib σ2dose σ2setup σ2motion andσ 2σdose 5%thenσdose 2.5%

Uncertainties in Electron Beam DosimetryLimitations of dose calculation algorithmssource modelsFluence Profiles from an eMLCABABBeam modifier effectheterogeneous patient anatomyLimitations of dose measurement systemsnon-calibration conditionscomplex beam modifier geometryJin et al (AAPM 2007)Pencil Beam Pinnacle3Monte Carlo (BEAM)Achterberg et al (ESTRO 1999)Pencil Beam Pinnacle3Monte Carlo (BEAM)Achterberg et al (ESTRO 1999)

20 MeV Beamlet DistributionsMonte Carlo (MCDOSE)Pencil Beam (FOCUS)Monte Carlo Codesfor Electron Beam Dose Calculations The BEAMnrc/DOSXYZnrc system Voxel Monte Carlo (VMC) Macro Monte Carlo (MMC) Superposition Monte Carlo Other programs (ITS, MCNP, PENELOPE) EGS4/MCRTP/MCDOSE/MCSIMMa et al (PMB 2000)Commercial Implementation Nucletron Oncentra MasterPlan (2001)– Implementation of Kawrakow’s VMC MonteCarlo dose calculation algorithm (2000) Varian Eclipse eMC (2004)– Based on Neuenschwander’s MMC doseTiming – Nucletron Oncentra MasterPlan 10x10 cm2 applicator50k histories/cm2Anatomy - 41 CT slicesPentium 4 Xenon 2.2 GHzCalculation time– 1.5 minutes for 6 MeV beam– 8.5 minutes for 20 MeV beamcalculation algorithm (1992)Faster than pencil beam!Courtesy of Joanna Cygler

Eclipse eMC no smoothingImplementation proceduresVoxel size 2 mmAir Modeling of clinical electron beamsAir1201101009080depth 6.7 cm706050depth 7.7 cm4018 MeVdepth 4.7 cm807060504030 Dose calculation, data processing and display11090RelativeDose CT data and beam setup conversion120depth 4.7cm18 MeV100Relative Dose Commissioning of clinical electron beams4.7 0246-6Off-axisX position /cm-4-2024Off-axisY position /cmDing et al (PMB 2006)Effect of voxel size and smoothingMU real patient vs.water tank(MC / Water tank 292 / 256 1.14)AirAir2mmandnosmoothing18 MeV110Relative Dose1009080702mmandwith3Dsmoothing605 mm and with 3D smoothing50120Relative Dose1201104.7 cmBoneBone405 mm and with3D smoothing90807060502 mm and with 3D smoothing40302mmandnosmoothing18 MeV10030depth 4.9 cm202010depth 4.9 cm1000-6-4-20246Off-axisX position /cm-6-4-20246Off-axisY position /cmDing et al (PMB 2006)Courtesy of Joanna Cygler6

MU real patient vs.water tankInternal mammary nodes(MC / Water tank 210 / 206 1.019)Target 1,2 MCbased MUTarget 1,2 water tankbased MULt eye watertank basedLt eye MCMUbased MURt eye watertank basedMURt eye MCbased MUCourtesy of Joanna CyglerMonte Carlo forMixed Beam Treatment for BreastCombined Photon/Electron Plan Based on MC Conventional (46 Gy, 14 Gy boost)Photon beams to whole breast: 23 fractions, 2Gy/fractionElectron boost to tumor bed: 7 fractions, 2 Gy/fraction Hypofractionated (45 Gy, 56 Gy)IMRT to whole breast: 2.25 Gy x 20 fractionsIMRT/MERT to tumor bed: 2.8 Gy x 20 fractionsCourtesy of Jinsheng 22.5Gy13.5Gy4.5GyCourtesy of Jinsheng Li

Conclusions Monte Carlo is a useful tool for radiotherapytreatment planning & dose verification Monte Carlo has a more important role inelectron dose calculation High accuracy, high efficiency, low cost More work is needed to make it clinicallyavailable

Electron Beam Treatment Planning C-MCharlie Ma, Ph.D. Dept. of Radiation Oncology Fox Chase Cancer Center Philadelphia, PA 19111 Outline Current status of electron Monte Carlo Implementation of Monte Carlo for electron beam treatment planning dose calculations Application of Monte Carlo in conventi

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