Differential recovery from potentially lethal damage in normal human lung fibroblasts after irradiation with 60Co gamma-rays and accelerated N-ion beam.

PLD recovery after irradiation with accelerated N-ion was examined and compared with that after irradiation with 60Co gamma-rays in normal human lung fibroblasts (IMR-90). No shoulder region was observed in the survival curve of the cells after N-ion irradiation. Ratios of D0 values before and after a 6-hour incubation in plateau phase were 1.1 and 1.8 for N-ion irradiation and gamma-ray irradiation, respectively. The results show that recovery after irradiation with high-LET radiation is slow and much less than after low-LET irradiation.