Regeneration of the mice liver after fractionated roentgen and proton irradiation

The authors studied the rate of regeneration of the locally irradiated liver of mice in different conditions of dose fractionation. Regeneration was induced by a partial hepatectomy, conducted on the 4th day upon the termination of irradiation. Increment in wet and dry weight served as the criteria of intensity of regeneration. Slowing down of the regeneration tempo in the dose range of 1570 to 3140 rad is linearly changed from 31 to 47% (by dry weight). Two tested irradiation conditions (fine fractionation---137 rad 4 times a week and large fractionation---550 rad once a week which had been carried out in the course of 3 to 6 weeks before obtaining cumulative doses (1650 and 3300 rad) caused similar suppression of regeneration) in 20 to 25% in the first case and 34 to 36% in the second one. The rate of regeneratlon after roentgen and proton irradiation carried out in strictly the same depth distribution of the absorbed dose in equivalent cumulative doses (3300 rad of roentgen and 4125 rad of proton irradiation, RBE coefficient 0.8, once a week in the course of 6 weeks) was suppressed to a similar degree. (auth)