Abstract
The calculation of the dose rate and cumulative dose in the morrow-free skeleton and bone marrow of thorotrast patients presupposes the knowledge of both the translocation of thorium daughters to the skeleton, and the portion of 232Th that is localized in colloidal form in the bone marrow. Whereas in bon marrow 228Th is in equilibrium with 232Th up to only 20%, in marrow-free skeleton 228Th is present in excess to 232Th (average activity ratio 1·75), considering the measured activity ratios between 232Th and its daughters as well as the distribution of the colloid and the unclides of the thorium decay chain within the organism the dose rate and cumulative dose in bone marrow and marrow-free bone were calculated as function of the time of thorotrast burden and the amount of injected material.