Pathologic effects of intracavitary irradiation with Californium-252

The effect of exposures of miniature swine to 252Cf afterloading tubes placed in the cervix uteri with a tandem applicator were compared with those effects resulting from 226Ra sources. Dosimetry for the adjacent normal tissues was established by surgically attaching thermolumuniscent dosimeters (TLDs) at the various sites, as well as by theoretical calculation. Changes were observed in the rectum, urinary bladder, ureters and cervix as both early, 75 days, consequences of exposure. Although ureteral stricture was the most frequent complication, the consistency of response with dose did not permit calculation of a neutron relative biological effectiveness (RBE) for the ureters. However, changes in the other tissues (rectum, urinary bladder and uterine cervix) at risk in radiotherapy were used to calculate RBEs for both early and late complications. The overall value for early fibrosis was 4.34 ± 0.41. For late fibrosis the overall value was 6.73 ± 0.43, indicating that the repair potential of these tissues is not as good after neutron exposure. RBEs for vasculitis and muscle degeneration were similar.