Double strand break formation as a response to X-ray and targeted proton-irradiation

The use of targeted ion beams has been an important development for understanding the response of biological systems to radiation exposure. Most investigations in this field have been performed with helium ion microbeams; however, irradiations using a beam of protons, covering different LET values, can deliver complementary results and additional information on radiation effect related to radiation quality and low dose exposure. Recently, several experiments have been carried out at the new single ion hit facility in the Institute of Nuclear Physics in Cracow using a focused proton microbeam. In parallel, similar cross-validation experiments have been performed using the well-established particle microbeam situated at the Gray Cancer Institute with the same cell line and proton energy. Pilot studies have compared the yields of double strand breaks (DSBs) in cells uniformly irradiated with 240 kV X-ray with those irradiated with microbeam delivered protons, and in some cases helium ions. The number of DSBs increased with the X-ray dose. In the samples irradiated with individually counted protons, fewer foci were found in comparison to the number of protons delivered per cell. Studies also compared the distribution of foci per cell between the different radiation qualities