Dose-Response Curve for Chromosome Translocations Induced by Low Dose Rate 137Cs Gamma Rays

What is it about?

A calibration curve for chronic exposure to 137Cs gamma rays is required for biological dosimetry of individuals exposed in connection with Chernobyl and other radiation accidents involving radiocaesium. Here, chromosome painting was used to measure the frequencies of reciprocal translocations in human lymphocytes following protracted exposures in vitro to 0.29, 0.62 and 0.95 Gy of 137Cs gamma rays. The exposures were delivered continuously during 48 hours.

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Why is it important?

A reliable measure of the liner slope (alpha coefficient) of the dose-response curve was obtained by analysing 18,389 metaphase lymphocytes in the irradiated samples and 25,067 in the controls. The alpha coefficient was measured to be 0.030 ± 0.003 translocation per cell per Gy when fitting the data with a linear model using a weighted least square method and a very similar 0.029 ± 0.009 translocations per cell per Gy when fitted with a weighted least square linear-quadratic model. These results provide a calibration curve for biodosimetry involving protracted or low dose exposures to 137Cs gamma rays, where the alpha coefficient defines the induced translocations frequency.