The effects of dose-fractionation on radiation-induced heart disease in rats

The hearts of Wistar rats were irradiated locally with a range of total doses given in 1, 3, 5 or 10 fractions in 4 weeks. As even after the lowest single dose of 17.5 Gy all animals died within 18 months after irradiation from heart failure, no ED50 could be determined. Therefore, the mean survival time following irradiation was chosen as isoeffect for the comparison of different treatment groups. Fractionation has a marked sparing effect on the radiation-induced heart disease. For an isoeffect of a mean survival time of 42 weeks an alpha/beta of 1 Gy was found.