@misc{oai:repo.qst.go.jp:00069358,
 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 = {Jun},
 note = {It is known that various biological effects of high-LET radiation such as heavy ions are showed an effective peak in the LET ranges of 100-200 keV/micrometer. However, some reports showed that the peak position of LET-RBE curves for cell death, induction of chromatin breaks and mutation induction shifted to higher LET ranges when using different ion species. 
In this study, we investigated the dependence of LET and ion-species for the induction of initially measured and non-rejoined chromatin breaks. Normal human fibroblasts were irradiated with 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 values were used 2 to 4 per each ion. Chromatin breaks were counted as a fragmentation of prematurely condensed chromosome using a technique of premature chromosome condensation (PCC). 
The number of excess fragments per cell per Gy for initially measured chromatin breaks increased with increasing LET up to around 100 keV/micrometer and showed a plateau above around 100 keV/micrometer. The number of initially measured breaks didn't show ion-species dependence. On the other hand, the number of non-rejoined chromatin breaks were clearly dependent on LET and ion-species. We also calculated a cross section and evaluated the LET and ion-species dependent on initially measured and non-rejoined chromatin breaks. The cross section curves of both chromatin breaks increased with increasing LET. Those for non-rejoined chromatin breaks were more scattered than those for initially measured chromatin breaks.  
These results suggest that the LET dependent structure in chromatin-breaks inductions is reflected in biological consequences of repair processes., 10th International Workshop Radiation Damage to DNA},
 title = {Dependence on LET and Ion-Species for the Induction of Initially Measured and Non-Rejoined Chromatin Breaks in Normal Human Fibroblasts.},
 year = {2008}
}