Abstract
We have been studying LET and ion species dependence of RBE values in cell killing and mutation induction. Normal human fibroblasts were irradiated with heavy-ion beams, such as carbon (290Mev/u and 135Mev/u), neon (230Mev/u and 400Mev/u), silicon (490Mev/u) and iron (500Mev/u) ions, generated by Heavy Ion Medical Accelerator in Chiba (HIMAC) at National Institute of Radiological Sciences (NIRS). Cell killing effect was detected as a reproductive death using a colony-formation assay. Mutation induction in hprt locus was detected to measure 6-thioguanine resistant colonies.The RBE values of cell killing increase with increasing in the atomic number of ion species. The RBE-LET curve of mutation induction for carbon-ion beams showed a peak at the LET of around 100keV/micron, while it showed a plateau without a remarkable peak ranging from 100 to 150 keV/micron for silicon ion beams.There is evidence that the RBE-LET relationship for mutation induction is not the same with different ion species. [J Radiat Res 44:451 (2003)]
