Proton beam profiling in soft biological matter by detailed Monte Carlo simulation

Distributions of relevance to proton beam profiling in soft biological matter are obtained by our Monte Carlo track structure code (MC4), which simulates in an event-by-event mode the electronic losses of light ions and all their secondary electrons in water. We present results on electronic energy density and clustering of interaction events around MeV proton tracks which are associated with important local track parameters. The detailed character of the simulation based on single-collision cross sections for all the elementary interaction processes allows a probing resolution of the order of nanometers. Since soft biological tissue exists in a liquid/solid like state we compare results obtained by both the oscillator strength properties of the water molecule and the dielectric response of liquid water. Their differences in terms of the nanometric pattern of proton tracks is examined. (c) 2006 Elsevier B.V. All rights reserved.