Microdistribution and Microdosimetry of Thorium Deposited in the Liver

Abstract

The distribution of thorium in the liver of a patient 36 y after injection with Thorotrast was examined with autoradiographic and scanning electron microscope backscatter image techniques. Autoradiographic examination of randomly selected histologic sections of the liver showed a total alpha activity calculated at 33.7 Bq g-1, with the highest concentration of alpha activity sequestered in subcapsular scare tissue. Subcapsular scare tissue received 4.8 cGy d-1 of alpha radiation, periportal areas were accumulating 1.4 cGy d-1, and the hepatic cord areas 0.09 cGy d-1 of alpha radiation at the time of death. The concentration of dose in periportal areas correlates with higher incidence of bile duct tumors (than hepatocellular carcinomas) found in patients exposed to Thorotrast. The backscatter technique was demonstrated as useful for identifying thorium in liver specimens.

Radiation Risk of Malignant Neoplasms in Organs of Main Deposition for Plutonium in the Cohort of Mayak Workers with Regard to Histological Types

“…This result is consistent with the reported proportion of hemangiosarcomas among liver cancers attributable to thorotrast irradiation of 21Y28% (Mori et al 1999;van Kaick et al 1991;Andersson 1997), while among atomic bomb survivors the fraction of liver hemangiosarcomas was 0.2Y0.3%. Cholangiocarcinomas arise in the bile ducts, which were estimated to receive 15 times higher exposure than the hepatic cord tissue (Dagle et al 1992). The high proportion of hepatocellular cancer in the present study is consistent with findings for the atomic bomb survivors (Preston et al 2007) but not with studies of Thorotrast exposed patients for which cholangiocarcinoma was found to be the major histological type (UNSCEAR 2008).…”

Radiation and Risk of Liver, Biliary Tract, and Pancreatic Cancers among Atomic Bomb Survivors in Hiroshima and Nagasaki: 1958–2009

“…Patients who were chronically exposed to alpha particles from Thorotrast (contrast material containing colloidal thorium dioxide) (9, 10) and workers at the Mayak nuclear facility who were exposed to both inhaled plutonium and external gamma radiation (8,45,46) had elevated risks for liver cancer. Of note, the dominant histological type is hepatocellular carcinoma among the LSS participants (Table 2) and Mayak workers with relatively lower plutonium doses (46), while it is cholangiocarcinoma and/or hemangiosarcoma among Thorotrast patients, reflecting the fact that intravenously administered Thorostast is more likely to deposit in periportal areas than in hepatic cord areas of the liver (47). In the Mayak workers cohort, hemangiosarcoma was also observed, exclusively among workers exposed to higher plutonium doses (!4 Gy) (46).…”

213Bi-DOTATOC receptor-targeted alpha-radionuclide therapy induces remission in neuroendocrine tumours refractory to beta radiation: a first-in-human experience

“…In addition, the spatial resolution of a gamma camera is insufficient to provide reliable microdosimetry. In a post-mortem autoradiography evaluation of a subject exposed to the alpha emitter 232 Th, microscopic “hot spots” with doses up to 50-fold higher than those assuming a homogeneous organ biodistribution were found [ 36 ]. Therefore the 440 keV gamma images of 213 Bi-DOTATOC are not sufficient for imaging-based dosimetry.…”