Basic Clinical Radiobiology 2017

• Suspension containing particles of thorium dioxide • Contrast medium in X-ray diagnostics in 1930s and 40s • Excellent images: thorium has high absorption cross section • The naturally abundant nuclide 232 Th is slightly unstable, decays through emission of an alpha particle • Drug is distributed to liver, spleen, lymph nodes, bone • Biological half-life is 22 years, physical half life >10 10 years!