Tissue Dose in Thorotrast Patients

Abstract

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 =?h tissue distribution, and steady state activity ratios between the subsequent daughters.Correcting for the a-particle self absorption within Thorotrast aggregates, the mean or-ray dose to a standard 70-kg man at 30 yr after the injection of 25 ml of Thorotrast is 750rad to the liver, 2100rad to the spleen, 270rad to the red marrow, 60-620rad 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 *"Ra 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/lOO rad of average skeletal dose from 224Ra and its daughters, the induction of 1.6-3.1 bone sarcomas per lo00 Thorotrast patients is predicted.

Neoplastic Diseases Induced by Chronic Alpha-irradiation - Epidemiological, Biophysical and Clinical Results of the German Thorotrast Study**

“…Dose rate calculations were done based on the results of Kaul and Noffz (1978) . According to the results of Thorotrast tissue distribution analysis, about 97% of the intravascularly injected colloidal thoriumdioxide is retained by the organs of the RES of the standard Thorotrast patient: liver 59%; spleen 29%; bone marrow 9%; skeleton (except marrow) 2%; lungs 0.7%; kidneys 0.1%.…”

“…With regard to individual organs there may be differences in thoriumdioxide content by up to a factor of 100 . According to Kaul and Noffz (1978) an intravascular injection of 25 ml Thorotrast in a 70 kg person causes the following absorbed dose rates: liver 25 cGy/yr; spleen 70 cGy/yr; bone marrow 9 cGy/yr; endothelial layer in bone 16 cGy/yr; kidney 0.4 cGy/yr. The radiation dose in the lung tissue is mainly caused by the daughter product 220Rn, which is exhaled by the breath .…”

Thorotrast and in vivo thorium dioxide: Numerical simulation of 30 years of α radiation absorption by the tissues near a large compact source

“…More precisely the ratio of the activity of a species in a tissue sample with respect to the activity of 232 Th in the same sample is reported. These coefficients are taken from [13], who refined and summarized the results of previous works, and refer to liver and spleen tissues.…”

“…The parameters of the biological depletion in the last column of Table 2 are the long-term relative activities of some nuclear species with respect to the one of 232 Th, as reported in [13]. These numbers are not directly used in the code.…”

“…These deposits persist over a time scale that is much longer that a human life (see for example [12]). In particular 90 % of the total thorium dioxide burden of the body accumulates in liver and spleen (see [13]), in the form of compact granular aggregates large enough to absorb a relevant fraction of the emitted α radiation ( [11]). …”