Abstract
General equations for fractionated protracted irradiation have been applied to the analysis of mouse lung data derived from isoeffect protocols. The data were accrued from a spectrum of different protocols including different radiation qualities, interfraction times and dose-rates. This analysis, based upon two component repair rate processes, suggests that there are possibly two repair-rate processes involved in the repair of sublethal damage in the lung. The two repair half-lives were 0·32 and 1·92 h with a low dose-rate partitioning of 1:0·38 between the amount of lethal damage resulting from rapid and slow sublethal damage repair processes at low dose-rates. The analysis also indicates that there may be a dose-rate amplification of the amount of resultant lethal damage, deriving from sublethal damage, associated with the longer repair process. It is also shown that the α/β ratio is probably independent of the radiation quality and that the ratios of multiple to single event damage for 240kVp X-rays and 60Co are almost identical. However, the absolute values of α and β for 240 kVp X-rays may be greater than for 60Co.