Equivalency of the quality of sublethal lesions after photons and high-linear energy transfer ion beams

The quality of the sublethal damage (sld) after irradiation with high-linear energy transfer (let) ion beams was investigated with low-let photons. chinese hamster v79 cells and human squamous carcinoma sas cells were first exposed to a priming dose of different ion beams at different lets at the heavy ion medical accelerator in the chiba facility. the cells were kept at room temperature and then exposed to a secondary test dose of x-rays. based on the repair kinetics study,the surviving fraction of cells quickly increased with the repair time,and reached a plateau in 2-3 h,even when cells had received priming monoenergetic high-let beams or spread-out bragg peak beams as well as x-ray irradiation. the shapes of the cell survival curves from the secondary test x-rays,after repair of the damage caused by the high-let irradiation,were similar to those obtained from cells exposed to primary x-rays only. complete sld repairs were observed,even when the let of the primary ion beams was very high. these results suggest that the sld caused by high-let irradiation was repaired well,and likewise,the damage caused by the x-rays. in cells where the ion beam had made a direct hit in the core region in an ion track,lethal damage to the domain was produced,resulting in cell death. on the other hand,in domains that had received a glancing hit in the low-let penumbra region,the sld produced was completely repaired. © the author 2017.