1. An image of the distribution and concentration of radioactivity in a tissue or other substance made by placing a photographic emulsion on the surface of, or in close proximity to, the substance.
2. An image recorded on a photographic film or plate produced by the radiation emitted from a specimen; such as, a section of tissue, which has been treated or injected with a radioactively labeled isotope or that has absorbed or ingested; such an, isotope.