A procedure to find areas in the body where cells, such as tumor cells, are dividing rapidly. A small amount of radioactive material is injected into a vein or swallowed, and travels through the bloodstream. A machine called a scanner measures the radioactivity and produces pictures (scans) of internal parts of the body. The pictures can show abnormal changes in the area of the body containing the radioactive material. Examples of gamma scans include PET scans, gallium scans, and bone scans. Also called radionuclide scanning.