Abstract
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.
In this study, event-by-event Monte Carlo track structure simulation technique was used to evaluate the LET-DSB relationship. Both of direct and indirect actions to DNA molecules can be considered in the simulation of strand break induction by irradiation of several types of ions with wide energy range. The strand breaks in diluted solution, cell mimetic condition and humid sample mimetic condition were calculated. The simulation results show the DSB yields increase with the increase of LET for all tested conditions. This result supports the idea that the increase of energy deposition density induces the increase of biological effect as a result of the increase of dense and severity of DNA damage. Although, our result is not consistent with some recent studies reporting the decrease or consistency of DSB yields with the increase of LET. To explain the cause of such discrepancy, some points in experimental detection system of DSB and the problems in calculation of absorbed dose (Gy) for particle beams will be discussed.
