M.G. Pia et al. Brachytherapy at IST Results from an atypical Comparison Project Stefano Agostinelli 1,2, Franca Foppiano 1, Stefania Garelli 1, Matteo Tropeano 1 1 National Institute for Cancer Research and 2 Physics Dept. Univ. of Genova Petteri Nieminen & Maria Grazia Pia

M.G. Pia et al. History March 2000 Comparison Projects were approved by the CB/TSB as a milestone 2000 The group decided to contribute to the milestone June 2000 Proposals were presented to the TSB First results shown to the TSBThe status of comparison projects is presented at the Geant4 Workshop Further results presented at the Calor2000, MC2000, AIRO conferences and Geant4 workshop October 2000April 2000 Letters of intent were presented to the TSB by the experiments Work on the Comparison Project started May 2000 First results presented at the ICCR conference September 2000 Further results presented at the ESTRO conference December 2000 Code to be released as an advanced example Publications 2001

M.G. Pia et al. a radioactive source, for example 192 Ir, is used the source moves along catheters inserted in natural cavities of the body, e.g. vagina or bronchi; this allows the deposition of the therapeutic tumor dose right where it is needed the source track is programmed by an after-loading unit What is brachytherapy? ] Brachytherapy is a medical therapy used for cancer treatments ] Radioactive sources are used to deposit therapeutic doses near tumors while preserving surrounding healthy tissues ] In HDR endocavitary brachytherapy: Catheter along which source moves After-loading unit

M.G. Pia et al. Brachytherapy treatment planning A typical vaginal treatment plan: source moves along a single catheter A typical intra-uterine treatment plan: the source moves along 3 catheters

M.G. Pia et al. Monte Carlo for brachytherapy Monte Carlo simulation topics for brachytherapy: o Dose calculation n Computation of dose deposition kernels for treatment planning dose calculation algorithms based on convolution/superposition methods n 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) o Verification of experimental calibration procedures

M.G. Pia et al. Comparisons with data Simulated water  (photon attentuation coefficient) Comparison of NIST data with Geant4 Standard electromagnetic package and Low Energy extensions results Comparison with in-house experimental data and certifications of the supplying company Tests of Low Energy/Standard e.m. Physics packages ESA Radioactive Decay Module Full simulation of the radioactive source Simulation of a simple set-up

M.G. Pia et al. Comparisons with full source simulation Air kerma rate at various distances Comparisons with measurements of the air kerma rate at IST, following the Protocol for the Basic Dosimetry in Radiotherapy with Brachytherapy Sources of the Italian Association of Biomedical Physics Anisotropy Comparisons with published reference treatment planning data Isodoses Comparisons with tabulated isodoses for superficial brachytherapy applicators

M.G. Pia et al. Photon attenuation coefficient, Water (Statistical errors are smaller than dot size) Comparison of Geant4 LowE/standard e.m. processes and NIST data

M.G. Pia et al. Photon attenuation coefficient, Fe (Statistical errors are smaller than dot size) Comparison of Geant4 LowE/standard e.m. processes and NIST data

M.G. Pia et al. Photon attenuation coefficient, Pb (Statistical errors are smaller than dot size) Photons are all absorbed with Standard below 100 keV Comparison of Geant4 LowE/standard e.m. processes and NIST data

M.G. Pia et al. Description of  -Selectron 192 Ir source ] Geant4 allows complete flexible description of the real geometry ] 192 Ir energy spectrum l currently described as monochromatic at 356 keV l will soon be described by the ESA Geant4 RadioactiveDecay class

M.G. Pia et al. Simulation of dose deposition in water ] The simulated source is placed in a 30 cm water box ] The dose deposition is investigated in the longitudinal plane ] The plane is partitioned in 1 million 1mm 3 voxels ] A minimum of 10 millions photons are generated on the 4  solid angle Longitudinal plane partitioned in cells  -Selectron 192 Ir source

M.G. Pia et al. Investigated quantities: anisotropy ] The dose deposition is not isotropic due to source geometry and auto- absorption, encapsulation and shielding effects ] Anisotropy can be described by a simple angular function which can be computed by re-sampling our simulated voxels grid calculations

M.G. Pia et al. Investigated quantities: isodoses ] The simulated dose deposition data can also be used to derive isodoses

M.G. Pia et al. Products of this Comparison Project ] Tests of Geant4 LowE/standard e.m. processes ] Tests of the Geant4 Radioactive Decay Module  A physics test (  ) to become part of regular LowE testing ] An Advanced Example to be released to the user communities ] The porting of Geant4 2.0 to Windows/Cygnus ] 4 common presentations at conferences so far ] 2 common publications in preparation (+ IST group’s ones) ] A wide promotion of Geant4 in the medical environment ] A contribution to technology transfer

M.G. Pia et al. Conclusions and future goals ] This Comparison Project has already generated valuable products ] The activity of the experimental group and of the Geant4 collaborators are fully integrated, with mutual benefit ] Further developments and comparisons are planned in the next weeks / More realistic description of 192 Ir source energy spectrum with the new Geant4 RadioactiveDecay class / Comparison with in-house data / Simulation of shielded brachytherapy applicators Many thanks to Gabriele Cosmo and Alessandro Brunengo for their invaluable help!