MODEL RELEASED. Gamma scan. Middle-aged man undergoing a gamma or radionuclide scan of his abdomen, with a radiographer. This diagnostic technique is based on the detection of radiation emitted by radioactive substances known as radionuclides, which are introduced into the body. Specific radionuclides are swallowed by the patient. These are absorbed in different concentrations by different types of tissue, where they emit radioactive gamma rays. The rays are detected by a camera (upper left) which produces an image from which the functioning of the tissues is studied. Gamma scans are also known as scintigrams.