[The medical management of high risk individuals. Experiences with persons exposed to chronic internal irradiation].

The medical management and counseling of persons at high risk due to exposure to chemicals or radiation or due to personal disposition, present an additional challenge for physicians and especially radiologists involved. This article is based on own experiences with patients who had been exposed to Thorotrast. They had been injected with the contrast medium Thorotrast, which was in use world-wide until around 1950. Thorotrast caused a chronic alpha irradiation mainly of the liver (up to 0.4 Gy/a), spleen (1.2 Gy/a) and bone marrow (0.1 Gy/a). For the Thorotrast patients and their physicians the most worrying problem was the risk of primary malignant liver tumors which occurred in more than 20% of the exposed persons, i.e. 100 times more frequently than in a non-exposed control group. The medical and especially radiological experiences with the management of these patients summarize a general aspect of the problem and can be referred to when managing other high risk groups.