Consideration on the LET dependence of DNA double strand breaks from the microdosimetric viewpoint

Watanabe, Ritsuko; Hirayama, Ryoichi*; Yokoya, Akinari; Terato, Hiroaki*; Tsuruoka, Chizuru*; Eguchi, Kiyomi*; Furusawa, Yoshiya*; Kobayashi, Katsumi*

DNA double strand breaks (DSB) is thought to be the most critical damage for cell death. However, a considerable discrepancy is often observed between LET dependence of the frequency of cell death and that of the DSB yield. Also, several studies on the DSB yields as a function of LET have reported different tendency in the DSB-LET relationships. To obtain insight of the relationship between DSB and cell death, it is necessary to clarify the actual LET dependence of DSB. We have been discussing about the reason why the difference of the results depending on the groups. Here we will report on the results of our discussion. In particular, some points on the experimental detection system of DSB and the problems in calculation of absorbed dose (Gy) for particle beams will be discussed.