Abstract: The majority of ionizing radiation accidents is partial exposure. Dolphin's model, recommended by IAEA, is applied to estimate partial exposure dose. Apply this model to calculate the chromosome aberration frequency in exposure area, and then put the chromosome aberration rate into dose-response curve established in vitro to estimate partial exposure dose. For elevating accuracy of partial exposure dose estimation, choosing appropriate dose-response curve is as important as accurately calculating chromosome aberration frequency. However, studies about affection of dose-response curve with different dose rate on partial exposure estimation are limited. Base on this, partial exposure doses were estimated by dic+r frequency and affection of dose-response curve with different dose rate on partial exposure estimation was analyzed in this study. Human peripheral blood lymphocytes (from sample A or sample B) were induced by ⁶⁰Co γ rays at 1 Gy and 5 Gy. Mix the exposed blood with the blood without exposure in 25% or 75% ratio to simulate partial exposure. Analyze dicentric chromosome (dic) plus centromeric ring (r) frequencies in mixed blood via Dolphin's model. Partial doses were estimated by using two curves with different dose rate. As results, dic+r distribution in most of mixed blood samples did not conform to poisson distribution. Based on the dose-response curve consistent with the actual dose rate, most partial doses were close to the actual doses, and the relative deviation was less than 10%. However, the estimated dose of 1 Gy 25% groups of two samples deviate greatly from the actual dose. Applying the dose-response curve inconsistent with the actual dose rate, all the relative deviation between estimated partial doses and actual doses were more than 10%. In conclusion, dic+r can be used to estimate the simulated partial exposure dose in vitro. It is more accuracy for partial exposure dose estimation to apply dose-response curve, which dose rate is same as actual dose rate.

Key words: partial exposure, dolphin's model, chromosomal aberration, dose estimation