Heavy charged particles in radiation biology and biophysics

Ionizing radiations induce a variety of molecular and cellular types of damage in mammalian cells as a result of energy deposition by the radiation track. In general, tracks are divided into two classes of sparsely ionizing ones such as electron tracks and densely ionizing tracks such as heavy ions. The paper discusses various aspects and differences between the two types of radiations and their efficacies in radiation therapy. Biophysical studies of radiation tracks have provided much of the insight in mechanistic understanding of the relationship between the initial physical events and observed biological responses. Therefore, development of Monte Carlo track-structure techniques and codes are paramount for the progress of the field. In this paper, we report for the first time the latest development for the simulation of proton tracks up to 200MeV similar to beam energies in proton radiotherapy and space radiation. Vital to the development of the models for ion tracks is the accurate simulation of electron tracks cross sections in liquid water. In this paper, we report the development of electron track cross sections in liquid water using a new dielectric model of low-energy electrons accurate to nearly 10% down to 100 eV. 5 Author to whom any correspondence should be addressed. New Journal of Physics 10 (2008) 075006 1367-2630/08/075006+28$30.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft