Relation between chromosomal aberrations and radiation dose during the process of TBI

Purpose: The purposes of this study were (1) to consider the dose-response relationship in-vivo at high dose range by using the Colcemid method, which begins with predicting the risk of future late complication caused by a fixed dose of chromosomal aberration of peripheral lymphocytes after radiation emission and (2) to compare in-vivo and in-vitro dose-responses for chromosomal aberrations in lymphocytes of cancer patients undergoing total body irradiation (TBI). Methods: Eight patients diagnosed with hematological malignancies entered this study. TBI planning with a 6 MV linear accelerator consisted of 4 Gy/2 fractions/day, and the total treatment dose was 12 Gy. Results: At the observable dose range of up to 10 Gy, the unstable chromosomal aberrations of both dicentrics and fragments increased with the increment of irradiated dose, regardless of in-vivo or in-vitro irradiated samples. However, the average number of dicentrics and fragments obtained from in-vitro samples was found to be higher than that for in-vivo samples. Conclusion: This result strongly suggests that in-vivo dose-response curves are necessary to estimate the absorbed dose in-vivo. In-vivo dose-response curves obtained from cancer patients would be very important for standard curves for biodosimetry.