Abstract
Thorotrast, a colloidal solution of thorium dioxide was injected to wounded soldiers, for angiography from 1930 to 1945. The patients who received Thorotrast are interesting objects for finding a biological effect due to the internal irradiation by 232Th. To determine a distribution and body burden of 232Th, forty-one Thorotrast patients were measured their gamma-rays with a pair of NaI (Tl) scintillation detectors coaxially positioned above and below the coach in the whole body counter of Nagasaki University. The comparison between the usual method using constant values and the method using individual values depend on the organ positions determined with CT (Computed Tomography) scanner for patients was performed to estimate the errors due to the individual differences in the detection efficiency of 232Th. From the results, the estimates by the whole body counter of the amounts of 232Th deposits in abdominal region were obtained within the uncertainties of 16%. And the absorbed dose in the liver and the spleen was also estimated from the amounts of 232Th.
