Dose-time relationships for skin reactions and structural damage in rat feet exposed to 250-kVp x rays.

The effects of fractionated irradiation on the feet of rats were the subjects of a time-dose study. The doses required to produce various levels of early skin damage, late skin damage, and late structural damage were determined for single doses and for treatments employing three fractions per week and lasting up to 50 days. The data did not follow the relationship first proposed by strandqvist, in which dose is proportional to time-n; rather, when the normal-tissue reactions were plotted on a linear-coordinate graph, they formed parallel time-dose isoeffect curves with distinct positive curvatures.