Improvement of low-energy stopping power algorithms in the FLUKA simulation program

Monte Carlo methods are actually the best tools to perform the detailed dosimetric and radiobiological calculations required in conformal radiotherapy. In this work we focus our attention on the FLUKA simulation program and on the electronic stopping power calculations for protons and α particles in materials of interest for therapy. We discovered large inaccuracies (>10%) with respect to the values suggested by ICRU (standard reference) for protons in compounds and α particles both in elements and compounds below 1 MeV/amu. These deviations, due to the standard approach based on additivity and scaling rules, could indeed affect radiobiological evaluations for primary charged hadron and neutron beams. Therefore, we developed new algorithms based on proper parametric formulae and inserted them in the FLUKA code. The new approach allows an agreement with ICRU data much better than 1% in the entire energy range 1 keV–100 MeV/amu spanned by the old one.