HISTOPATHOLOGY AND AM-241 MICRODISTRIBUTION IN SKELETAL USTUR CASE-246

Histopathology and qualitative autoradiography studies were undertaken on bone removed at autopsy from USTUR Case 246. The histopathology ex amination revealed extensive bone marrow peritrabecular fibrosis and d ecreased cellularity in most samples, In addition, histological indica tors suggest that bone cell turnover was suppressed at most sites? alt hough turnover was found to be essentially normal in a vertebral body sample, The autoradiographic studies showed that bone turnover that ha d occurred resulted in the redistribution of americium within bone, Ho wever, surface deposits of americium remained conspicuous at many site s, particularly those with low bone growth activity, A few percent of the americium was present in the bone marrow. The dosimetric and toxic ology findings indicate that current assumptions about the metabolic b ehavior of bone-seeking radionuclides are likely to be unrealistically simplistic.