Repair kinetics of mouse lung.

Pathological manifestations of lung damage after irradiation support the use of death between 11 weeks (80 days) and 23 weeks (160 days) as an assay for pneumonitis in the C3Hf strain of mice. The proportion of deaths and the time to reach a specific percent of lethality were found to be dose and dose per fraction-related. The median survival time and the latency period for the time of occurrence of pneumonitis, were dependent on total biological dose over a narrow range, equivalent to "normalized" doses of 36-41 Gy in 2 Gy fractions. All these criteria entered into the analysis of data. The linear-quadratic isoeffect model gives a good fit for the results over a range of doses from 1.6 to 8 Gy per fraction, that is, with the exclusion of the single dose data. The value of alpha/beta was always approximately 4.0 Gy from three kinds of analyses. The half-time for repair from sublethal injury was approximately 0.75 h. Both of these values are in agreement with the results from other investigators.