radiotherapy

therapeutic radiology: the treatment of disease with penetrating radiation, such as X-RAYS , beta rays, or gamma rays, which may be produced by machines or given off by radioactive isotopes. Beams of radiation may be directed at a diseased part from a distance (see TELETHERAPY ), or radioactive material, in the form of needles, wires, or pellets, may be implanted in the body (see BRACHYTHERAPY ). Many forms of CANCER are destroyed by radiotherapy.