抄録
To evaluate quantitative dose-response relationship on the biological response to radiation, it is necessary to consider a model including cumulative dose, dose-rate and irradiation time. In this study, we measured micronucleus formation and [3H] thymidine uptake in human cells as indicators of biological response to gamma radiation and statistically analyzed the data. Effective dose (EDx) was mathematically estimated by fitting a general logistic function to the dose-response relationship. It was obvious that EDx increased with longer irradiation time and that the biological response depends on not only cumulative dose but also irradiation time. We represented the relationship among the variables with a three-dimensional curved surface using a general multiple logistic function. It was found that the biological response declined sharply when dose-rate was less than 0.01Gy/h. To further estimate the dose-rate effect, we proposed modified exponential (MOE) models. Our models indicated that log(EDx) exponentially increased when dose-rate was less than 0.01Gy/h and that the risk approaches to 0 at infinitely low dose-rate. [J Radiat Res 44:402 (2003)]
