Preparation of an injectable technetium-99m (Tc-99m) isotope tracer for gamma scintigraphy (gamma camera scanning). Tc-99m is so short lived that generators fuelled by its longer-lived parent isotope, molybdenum-99 (a fission product of a nuclear reactor) are supplied to hospitals to provide a continuous, short-term supply. This technetium source (held in clamp) is from an Amertec II generator supplied by Amersham International. Sterile saline is used to release the technetium from the generator's alumina columns. The radioactive solution is added to a tracer chemical before being injected into the body. Photographed at The London Hospital.