an X-ray photograph made by bringing an object containing radioactive material into close contact with the emulsion on a film or plate: it shows the pattern of radioactivity in the object
See autoradiograph in American Heritage Dictionary 4
noun
An image recorded on a photographic film or plate produced by the radiation emitted from a specimen, such as a section of tissue, that has been treated or injected with a radioactively labeled isotope or that has absorbed or ingested such an isotope. Also called autoradiogram.