Absorbed doses to the liver, spleen, red marrow, lungs, kidneys, and to various parts of bone tissue were calculated for long-term burdens of intravascularly injected Thorotrast. The estimates were performed for typical injection levels of 10, 30, 50 and 100 ml, based upon “best estimates” of 232Th tissue distribution, and steady state activity ratios between the subsequent daughters. Correcting for the alpha-particle self absorption within Thorotrast aggregates, the mean alpha-ray dose to a standard 70-kg man at 30 yr after the injection of 25 ml of Thorotrast is 750 rad to the liver, 2100 rad to the spleen, 270 rad to the red marrow, 60–620 rad in various parts of the lung, and 13 rad to the kidneys. Dose rates to various parts of bone tissue (bone surface, compact, and cancellous bone) were estimated by applying the ICRP model on alkaline earth metabolism to the continuous translocation of thorium daughters to bone and to the formation of thorium daughters by decay within bone tissue. The average dose to calcified bone from translocated 224Ra with its daughters is 18 rad at 30 yr after the injection of 25 ml of Thorotrast. Considering the Spiess-Mays risk coefficient of 0.9–1.7% bone sarcoma/100 rad of average skeletal dose from 224Ra and its daughters, the induction of 1.6–3.1 bone sarcomas per 1000 Thorotrast patients is predicted.
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Kaul et al. (1978) studied this question.