@misc{oai:repo.qst.go.jp:00063162,
 author = {Tsuruoka, Chizuru and Suzuki, Masao and Furusawa, Yoshiya and Anzai, Kazunori and Okayasu, Ryuichi and 鶴岡 千鶴 and 鈴木 雅雄 and 古澤 佳也 and 安西 和紀 and 岡安 隆一},
 month = {Jul},
 note = {We studied the LET and ion-species dependence for cell-killing effect and the induction of chromatin breaks measured immediately after irradiation (initially measured chromatin breaks) and after 24h of irradiation (non-rejoined chromatin breaks). Normal human fibroblasts were irradiated with X rays (200 kV 20 mA) and heavy ions, such as carbon, neon, silicon and iron ions, generated by Heavy Ion Medical Accelerator in Chiba (HIMAC) at National Institute of Radiological Science (NIRS). The LET of different 2 - 8 values were used in each ion source. The cell-killing effect was detected as a reproductive cell death using a colony formation assay. Chromatin breaks were measured as an excess number of fragments of prematurely condensed chromosomes using a technique of premature chromosome condensation (PCC). The LET-RBE curves of the cell-killing effect and non-rejoined chromatin breaks were clearly dependent on LETs and ion-species. On the other hand, the curves of initially measured chromatin breaks were dependent on LET values up to 100 keV/µm, but not ion-species. We also calculated a cross section and evaluated the LET and ion-species dependence for cell-killing effect and the induction of chromatin breaks. The cross section curves of three different biological endpoints, such as cell-killing effect, initially measured chromatin breaks and non-rejoined chromatin breaks increased with increasing LET. These curves each ion source for the cell killing effect and non-rejoined chromatin breaks were very similar, and were more scattered than those for initially measured chromatin breaks. These results suggest that the LET dependent structure in biological effects is reflected in the consequence of biological repair process., Heavy ions in therapy and spece symposium},
 title = {Dependence on LET and ion-species dependence for cell killing and chromatin breaks in normal human fibroblasts.},
 year = {2009}
}