Monte Carlo Geant4 Simulations of Protons Lateral Deviation in Liquid Water

Abstract

Proton therapy is an advanced treatment technique for cancer cells leading to promising results compared to conventional photon radiotherapy. The protons deposit a large portion of their energy by inelastic (coulomb) interactions with the outer shell electrons of medium molecules causing the ionization or excitation processes, specially near the end of their range and weakly by elastic interaction with the nucleus. The last process seems to be responsible for the lateral deflection of the protons in the medium. This work presents the determination of the stopping power ( SP ), range ( R ), and radial deviation ( r ) of protons with impact energies 180 - 215 Me, by using the Monte Carlo Geant4 toolkit. In this contribution, we focus on the interaction of energetic proton beams with liquid water. We studied the correlation between the radial deviation lateral ( r ) and the incident kinetic energy ( E ), and the range ( R ). The results are compared to the available experimental and other simulation results. Good agreements are generally observed especially for the radial deviation. We find that the ratio between lateral deviation and range does not exceed 3- 4 %.

Keywords: Monte Carlo, Geant4, proton, liquid water, lateral deviation, stopping power.