Dose rate effect on cytogenetic damage in cells exposed to relativistic protons

Astronauts in space are chronically exposed particularly to high energetic protons [1]. However most of the data concerning biological effects of ionizing radiation come from studies in vitro and in vivo under acute conditions. To obtain a correct estimation of risk related to space radiation, it is necessary to compare biological damage obtained after acute and chronic irradiation. The aim of this project is to examine differences in cytogenetic damage induced by relativistic protons through the analysis of chromosomal aberrations (CAs). CAs are a useful indicator of biological risk [2]. During chronic exposure a lower frequency is expected compared to acute exposure, since intra-track effect will predominate in CA formation. The spectrum of aberrations should also be different. After acute exposure the inter-track effect should prevail, so more complex exchanges (derived from 3 or more breaks involving two or more chromosomes) are expected compared to chronic condition.