| Popis: |
ThO/sub 2/ is known to be distributed quite inhomogeneously within the tissues of Thorotrast patients. For reasons of calculating the dose with special emphasis on tissue dose on cellular level in man, animal experiments were done, with regard to the agglomeration of ThO/sub 2/ particles as a function of time of Thorotrast burden and self-absorption of ..cap alpha..-particles within Thorotrast aggregates of various sizes. Colloidal ThO/sub 2/, 25, 125, and 250 ..mu..l, was injected intravenously into female mice, or 2 ml of the colloid was administered intravascularly to male rabbits. The animals were sacrificed between 1 and 100, and 392 days, respectively, and tissue samples of the liver and spleen were analyzed by histoautoradiography and light and electron microscopy with respect to the aggregates' size distribution. For dose calculations the aggregates were assumed to be of spherical shape and classified into groups from 0.045 to 20 ..mu..m radus. Dose rate estimates were made with respect to cellular structures, cells adjacent to Thorotrast granules, and liver tissue in general, considering self-absorption of ..cap alpha..-particles as a function of Thorotrast particle sizes and time of Thorotrast body burden. According to the results local dose rates may vary from about 4000 rad/year (cellmore » membranes) to about 30 rad/year (mean dose rate to nuclei of liver cells), the mean dose rate to cells within the range of ..cap alpha..-particles emitted from aggregates of some micrometers in diameter will be in the order of 0.2 mrad/year to 2 rad/year.« less |
