Determination of thorium in the organs of deceased Thorotrast patients

“Thorotrast” was widely used in the past as an X-ray contrast medium, containing a colloidal solution of thorium dioxide (232ThO2). After injection, thorium accumulates and is mainly retained in the liver. Thus once Thorotrast is administered, patients might be chronically exposed to α-radiations. Recently, significant development of cirrhosis and cancer of the liver has often been noted among Thorotrast patients. Additionally the incidence of lung and breast disease has significantly increased. Thus, the assessment of internal radiation dose from deposits of Thorotrast is very important. In this report, the thorium content in various organs was determined by means of neutron activation analysis. All the samples were taken from organs of Thorotrast patients subsequent to death. The ashed samples were irradiated in a reactor. After cooling, the content of thorium was determined by measurement of gamma rays resulting from the decay of protactinium-233. For comparison, measurements by other analytical methods such as inductively coupled plasma mass spectrometry, colorimetric analysis using ArsenazoIII and radiation measurement of γ-rays from actinium-228, were carried out.