Imaging of Beta-Rays from Tissue Blocks with Thorotrast Deposition by Autoradiography using Fuji Computed Radiography

Abstract

Background: Autoradiography of tissue with radioactive substance such as Thorotrast by Fuji Computed Radiography (FCR) has been available. We obtained autoradiographs from Thorotrast-deposited tissue by FCR. However, the nature of radiation from tissue with Thorotrast was not certain, because alpha particles are shielded by the plastic front of the FCR cassette. Therefore, we undertook investigation to clearly explain the nature of radiation from Thorotrast in case of autoradiography.Materials and Methods: Tissue blocks of liver and spleen with Thorotrast deposition were imaged by autoradiography using FCR, and radioactivity of tissue blocks was measured by a GM survey meter. Measurement was carried out by both with and without an aluminum plate between the tissue and the surface of GM survey meter to shield beta-rays.Results: Autoradiographs of the liver and spleen with Thorotrast were successful. It took only one day to obtain autoradiograph of the spleen, and 14 days for the liver. The radioactivity count decreased dramatically when an aluminum plate was inserted between the specimen and GM survey meter, but some radiation remained. The tissue blocks were contained in a plastic bag and the front of the Cassette of Imaging Plate is covered by a thin plastic board, so alpha-rays from Thorium dioxide in Thorotrast had been shielded from the beginning.Conclusion: We concluded that the radiation from the tissue blocks with Thorotrast in a plastic bag was mostly from beta-rays and less than 5% of radiation was from gamma-rays from the daughter nuclei of Thorium dioxide.