Monte Carlo calculation of nanoscale dosimetric distributions of MeV proton tracks with secondary electron transport

Our MC4 Monte Carlo code which simulates in an event-by-event mode the electronic losses and slowing down process of protons and all their secondary electrons in water is used to obtain dosimetric distributions of interest to the biophysical modelling of proton beams at the submicron scale. Energy loss scattering models constructed from the oscillator strength formalism of Bethe as well as Ritchie’s dielectric approach have been implemented in order to explore the influence of non-linear density effects induced by the liquid-like cellular environment. We present results on energy deposition and its straggling for nanometer spherical volumes relevant to DNA- and chromatin-size targets. The influence of the impact geometry and the size of the volume are examined.