A quantitative model for the evaluation of dose rates effects following exposure to low-dose gamma-radiation

Abstract

Simultaneous consideration of the irradiation time and the cumulative dose isnecessary for evaluating the risk of long-term exposure to radiation at low dose. This study intends to examine several numerical relationships between doses and dose rates in biological responses to gamma radiation. Data on inhibition of [ 3 H] thymidine uptake and micronucleus formation in human osteosarcoma cells were analyzed using the median effective dose (MED) as a measure of the risk. MEDs were calculated using parameters estimated by fitting general logistic curves to the dose-response relationships for each group defined by irradiation time. Both biological responses, the inhibition of [ 3 H] thymidine uptake and micronucleus formation, decreased sharply when the dose rates were less than 0.01 Gy/h. Exponential functions were fitted to the log relationships between MEDs and dose rates. This modified exponential model described well the quantitative effect of dose rates on MEDs, and suggested that risk is extremely low at very low dose rates.

WAM to SeeSaw model for cancer therapy – overcoming LQM difficulties –

“…We can find similar behaviors in the data using cancer cells, such as human U2OS, glioma MO59K cell lines, in vitro. These experimental data are very interesting (Matsushita et al 1999;Magae et al 2003Magae et al , 2011Mu et al 2003;Ogata et al 2005;Nakajima et al 2007Nakajima et al , 2017Dewan et al 2009), and we shall analyze them in a forthcoming paper.…”