Role of the interaction processes in the depth-dose distribution of proton beams in liquid water

We use a simulation code, based on Molecular Dynamics and Monte Carlo, to investigate the depth-dose profile and lateral radial spreading of swift proton beams in liquid water. The stochastic nature of the projectile-target interaction is accounted for in a detailed manner by including in a consistent way fluctuations in both the energy loss due to inelastic collisions and the angular deflection from multiple elastic scattering. Depth-variation of the projectile charge-state as it slows down into the target, due to electron capture and loss processes, is also considered. By selectively switching on/off these stochastic processes in the simulation, we evaluate the contribution of each one of them to the Bragg curve. Our simulations show that the inclusion of the energy-loss straggling sizeably affects the width of the Bragg peak, whose position is mainly determined by the stopping power. The lateral spread of the beam as a function of the depth in the target is also examined.This work has been financially supported by the the Spanish Ministerio de Ciencia e Innovación (Project FIS2010-17225) and the European Union FP7 ANTICARB (HEALTH-F2-2008-201587). PdV thanks the Conselleria d’Educació, Formació i Ocupació de la Generalitat Valenciana for its support under the VALi+d program. We acknowledge support provided by the COST Action MP 1002, Nanoscale Insights into Ion Beam Cancer Therapy