中文摘要：

以人肝癌细胞系和正常肝细胞系为材料，报道了不同传能线密度射线辐射引发细胞染色体原初断裂及24h内的修复情况。计算了相对生物学效应的值。以L02染色体总断裂数量得出的RBE值96．05keV／μm的12C6＋为3．6，512keV／μm36Ar18＋为2．9。而以7721染色体总断裂数量得出的RBE值：96．05keV／μm的12C6＋为3．5，512keV／μm36ArAr18＋也为2．9。用产生等点染色单体断裂计算，则RBE更高。对比得出，高LET对增加等点染色单体断裂量的作用要远远大于对增加染色单体断裂量的作用。等点染色单体的断裂修复难度要远远大于染色单体断裂的修复难度，这也是高LET高致死率的一个重要原因。

英文摘要：

Human hepatoma SMMC-7721 and normal liver L02 cells were irradiated with γ-rays, 12C6＋and 36Ar18＋ ion beams at the Heavy Ion Research Facility in Lanzhou（HIRFL）. We reported the kinetic re-pair of chromosome breaks of L02 and SMMC-7721 cells in 24 h of post-irradiation time. The relative bio-logical effectiveness（RBE） for inducing chromatid breaks were 3.6 for L02 and 3.5 for SMMC-7721 cell lines at the linear energy transfer（LET） peak of 96.55 keV/μm 12C6＋ ions, and 2.9 （both of the two cell lines） at 512 keV/μm 36Ar18＋ ions. It suggested that the RBE of isochromatid-type breaks induced bya 36Ar18＋ was higher than those by 12C6＋. We concluded that the high production of isochromatid-type breaks, induced by the densely ionizing track structure, could be regarded as a signature of high-LET radi-ation exposure.