Abstract ID: 241 Geant4 simulation studies of secondary particles emission in hadrontherapy treatments.

The aim of this work is the full simulation with Geant4 (vs. 10.0.p03) of secondary particles emitted during an hadrontherapy treatment with 12C. An accurate study of the ion beam fragmentation is important for both the evaluation of secondaries field inside and outside the target volume (i.e. for radioprotection and biological effects evaluation) and the prediction of nuclear particle interactions and their reaction products. In this study we investigate the depth energy deposition (Bragg curve) and the rate of secondary particles produced in the interaction between 12C and targets of different materials (water and Plexiglas). Simple irradiation setup was first implemented for a preliminary comparison of the Geant4 code with literature studies [1,2]. A good agreement (∼0.04%) was found for the Bragg peak position and the peak-to-plateau ratio (∼0.3%). The complete CNAO [3] (Centro Nazionale di Adroterapia Oncologica) extraction beamline with the target water phantom was then simulated for a characterization of secondary particles energy deposition along the beam axis, angular distributions for outgoing protons, neutrons, heavy secondary particles and prompt gammas. An agreement within 0.03% was found for the Bragg peak position with respect to CNAO data and Fluka simulation for 279.97 MeV/u 12C, highlighting the reliability of the Geant4 simulation. Preliminary results agree with literature studies but experimental data are needed to validate the code. Comparisons with additional simulation codes are foreseen. Geant4 simulations studies to predict the development of different physical processes as a function of the beam energy are also ongoing for both protons and carbon ions.