Modelling low energy electron and positron tracks for biomedical applications

Purpose: To incorporate the effects of low energy electrons and positrons into radiation interaction models. Materials and methods: The simulation method proposed here was based on experimental and theoretical cross section data and energy loss spectra we have previously derived. After a summary of the main techniques used to obtain reliable input data, the basis of a Low Energy Particle Track Simulation (LEPTS) procedure was established. The programme is specifically designed to describe electron and positron interactions below 10 keV, down to thermal energies. Results: Single electron and positron tracks in water are presented and the possibility of using these results to develop tools for nanodosimetry is discussed. Conclusions: Standard approximations based on high incident energies, such as the Born-Bethe theory, are not suitable to simulate electron and positron tracks below 10 keV. Prior to the inclusion of low-energy effects in a radiation model, an appropriate study is required to determine both the interaction cross sections and the energy loss spectra.