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•
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