Abstract
Recent studies have showed that the sharp of the LET-RBE curves of biological effects was different, when using different ion species even if similar LET values. We reported that the sharps of LET-RBE curves of biological effects reflected by repair process, such as cell killing, mutation induction and non-rejoining chromatin breaks were dependent on ion species. However, the biological effect without going through repair process, such as initially measured chromatin breaks was independent on ion species and LET values over 100keV/μm.
In this study, we investigated whether repair kinetics of chromatin breaks induced by different heavy ions with a similar LET value were different or not.
Normal human skin fibroblasts were irradiated with around 100keV/μm of carbon, neon and silicon ions generated by Heavy Ion Medical Accelerator in Chiba at National Institute of Radiological Sciences. Chromatin breaks were counted as excess fragments of prematurely condensed chromosomes using a technique of prematurely chromosome condensation (PCC).
The ratios of residual chromatin breaks in carbon and neon ions after 24h of post-irradiation incubation were different in silicon ions. Furthermore, the ratios of residual chromatin breaks in carbon ions after 0.5h of post-irradiation incubation was greater than those in neon and silicon ions. These results suggest that difference in the ratio of residual chromatin breaks after 24h of post-irradiation incubation reflected the results of both fast and slow repair process.
