Abstract
Purpose : To investigate the time-course of chromosomal aberrations following radiations of differing LET. Materials and Methods : Syrian hamster embryonic cells were irradiated with nitrogen ions (LET infinity = 530 keV/ μ m) and helium-ions (LET infinity = 36 and 77 keV/ μ m), also 137 Cs γ-rays as a reference radiation. The frequency of chromatid-type aberrations was determined after 0–6 h incubation in a 5% CO 2 incubator at 37°C. Results : The amount of chromosomal damage per cell for nitrogen ions detected immediately after irradiation was lower than induced by 137 Cs gamma-rays. In contrast, helium ions were more effective than gamma rays in inducing chromatid type damage. The RBE values for the nitrogen-ion beams were 0.45 for gaps, 0.43 for deletions and 0.20 for exchanges. For helium-ion beams, the RBE values for the 36 keV/mum beams and the 77keV/ μ m beams were 1.2 and 1.5 for gaps, 1.3 and 2.1 for deletions, and 1.5 and 1.9 for exchanges, respectively. The frequency of cells with chromosomal damage following exposure to γ-rays and helium-ion beams showed a downward trend with increasing incubation period. In contrast, in the case of nitrogen-ion beams, there was an increase with the incubation period. Conclusions : The results show that it is possible to underestimate chromosomal damage for different types of radiation by scoring aberrations at a single fixed sampling time.
Published Version
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