Thorotrast is the trade name of 25% colloidal solution of thorium dioxide which is natural a-emitter. It was used as a radiological contrast medium during World War II. Since it deposited in so-called reticuloendothelial system long life, it caused hepatic malignant tumors by local exposure to a-particles decades after injection. The main goal of this archive is to provide data for epidemiological analysis of biological effects and risk assessment, and for the study of molecular mechanisms of radiation carcinogenesis induced by exposure to internally deposited radiation. This archive is mainly made of pathological data accumulated from all over Japan.

  The content of this archive is characterized by valuable data from various aspects: human cases, fairly homogeneous physical backgrounds of patients, accurate estimation of deposited amount of thorium and cumulative dose in major organs, presentation of meetings and journals where individual cases were reported and confirmed pathological diagnosis. Therefore the quality and the quantity of cases in this archive are incomparable in the world.

  All the data are filed for easy access by researchers. From the stand point of protection of privacy, only sequential case number, gender. age at injection, incubation period, deposited amount of thorium and histological diagnosis of induced liver tumors are presented on this home page,.

  The outcome obtained from this archive is presented.

  Although Thorotrast was the best radiological contrast medium at the time it was used, usage of Thorotrast resulted in grave consequences, that is, victims of radiation-induced cancers. Considering the fact, we hope this archive will contribute much not only to the risk assessment of radiation but also the protection of human cancers.

  Dr. Takesaburo Mori’s dedicated efforts and cooperation of all the pathologists, researchers and technical assistances all over Japan made it possible to construct this archive.

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