Gamma scan injection. View of an intravenous injection of the radioisotope Technetium-99m, given into the arm of a patient prior to a gamma camera scan. Although Technetium-99m produces only a low-dose of radioactivity, the radiographer is protected by lead shielding around the syringe, while gloves prevent direct contact with the liquid. Technetium-99m is used for the majority of gamma scans, since it is readily linked to a variety of tracer chemicals that are taken up by various organs of the body, including bone, liver, kidneys and even blood cells. Gamma rays emitted from the tracer pass through the body to be mapped by an external gamma camera.