Speaker
Description
Nanodosimetry focuses on measuring and simulating ionizations in low-pressure gas detectors that mimic tiny volumes and may serve as proxies for cellular DNA constituents and induction of clustered DNA damage. Nanodosimetry provides unprecedented measurements of physical parameters that govern biological effects of ionizing radiation. However, radiation-induced effects leading to biological endpoints are not limited to ionizations but include also excitations. Furthermore, both energy deposition types produce chemical species that diffuse, undergo mutual chemical reactions, and form radicals that attack DNA constituents. For sparsely ionizing radiation, these indirect effects represent the majority of the total DNA damage, while the role of direct effects from energy depositions to the DNA increases with linear energy transfer (LET). A natural question arises how far do ionization-derived quantities used in nanodosimetry such as ionization cluster size distributions (ICSD) represent biological effects across radiation qualities, from low-LET radiation used in conventional radiotherapy over ion beams in hadrontherapy to high-Z, high-energy particles in space radiation. To help address this question, ICSD simulations with PARTRAC Monte Carlo track structure code have been performed for 1 – 1000 MeV/u H – Fe ions (LET ranging from 0.2 to 4000 keV/µm) in 1 – 100 nm spheres. Nanodosimetric quantities such as the probabilities of at least two or three ionizations in these targets (F2 or F3) were compared with previously reported simulations on the yields of DNA double-strand breaks and their clusters including both direct and indirect effects, as well as with cell killing data from the Particle Irradiation Data Ensemble (PIDE) database. The results will be presented and discussed.