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F. Foppiano 1 , S. Agostinelli 1 , S. Garelli 1 , G. Paoli 1 , M. Bevegni 1 ,

COMPARISON BETWEEN PLATO ISODOSE DISTRIBUTION OF A 192 IR SOURCE AND THOSE SIMULATED WITH GEANT4 TOOLKIT. F. Foppiano 1 , S. Agostinelli 1 , S. Garelli 1 , G. Paoli 1 , M. Bevegni 1 , M.G. Pia 2 , P. Franzone 1 , T. Scolaro 1 , L. Andreucci 1

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F. Foppiano 1 , S. Agostinelli 1 , S. Garelli 1 , G. Paoli 1 , M. Bevegni 1 ,

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  1. COMPARISON BETWEEN PLATO ISODOSE DISTRIBUTION OF A 192IR SOURCE AND THOSE SIMULATED WITH GEANT4 TOOLKIT F. Foppiano1, S. Agostinelli1, S. Garelli1, G. Paoli1, M. Bevegni1, M.G. Pia2, P. Franzone1, T. Scolaro1 , L. Andreucci1 1National Cancer Institute and 2Physics Dept. of Genova foppiano@hp380.ist.unige.it

  2. Brachytherapy facility At the National Cancer Institute of Genova Ir-192 brachytherapy treatments are performed by a High Dose Rate (HDR) Microselectron afterloading unit. For the treatment planning we use Plato BPS, v 1.2.3 software

  3. Monte Carlo for brachytherapy Monte Carlo simulation topics for brachytherapy: • Dose calculation • Computation of dose deposition kernels for treatment planning dose calculation algorithms based on convolution/superposition methods • Separation of primary, first scatter and multiple scatter components for complex dose deposition models • Computation of other model-dependent parameters, e.g. anisotropy function • Accurate computation of dose deposition in high gradient regions (i. e. near sources) • Verification of experimental calibration procedures

  4. GEANT4 Low Energy Electromagnetic Physics down to250 eVfor electrons and photons • based on the LLNL data libraries • shell effects Geant4 Low Energy Electromagnetic package extends the coverage of physics interactions down to~ 1 keVfor hadrons and ions • Bethe-Block above 2 MeV • Ziegler and ICRU parameterisations (with material dependence) • free electron gas model • quantal harmonic oscillator model • charge dependence (Barkas effect) Further extensions are in progress Relevant for medical, space science, astrophysics etc. applications

  5. Geant4 tests: simulation of  Simulated water (attenuation coefficient) versus NIST data with Geant4 Standard electromagnetic package and Low Energy extension

  6. Description of -Selectron 192Ir source • Geant4 allows complete flexible description of the real geometry • 192Ir energy spectrum • currently described as monochromatic at 356 keV • will soon be described by the new GEANT4 RadioactiveDecay class

  7. Simulation of dose deposition in water • The simulated source is positioned in a 30 cm water box • The dose deposition is investigated in the longitudinal plane • Plane is partitioned in 1 million 1mm3 voxels • A minimum of 10 millions photons are generated on the 4 solid angle -Selectron 192Ir source Longitudinal plane partitioned in cells

  8. Results: PDD

  9. Results: Isodoses distribution

  10. Conclusions and future goals • Monte Carlo simulation is useful in brachytherapy both to obtain model-dependent parameters and to verify experimental data • Geant4 offers reliable particle-matter Monte Carlo simulation within a flexible modern object-oriented toolkit • We have used Geant4 to simulate  coefficients and a commercial brachytherapy source with full dose deposition calculation • Geant4 simulated dose deposition has been compared with Plato BPS calculations and has been found to be consistent Future goals • More realistic description of 192Ir source energy spectrum with the new Geant4 RadioactiveDecay class • Simulation of shielded and Leipizig brachytherapy applicators

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