radiology, branch of medicine specializing in the use of X rays, gamma rays, radioactive isotopes, and other forms of radiation in the diagnosis and treatment of disease. X ray machines and fluoroscopes are essential in diagnosing bone fractures, tumors, and other abnormalities of the internal organs. The computerized axial tomography (CAT) scan uses computer technology to focus X rays on precise sections of the body. Magnetic resonance imaging (MRI) utilizes supercooled magnets to concentrate and focus radiation in very small areas of the body, rendering sharp detail. Radioactive isotopes are also employed in diagnosis, e.g. iodine-131 is used to confirm cases of suspected thyroid disorder. In radiotherapy, X rays, gamma rays, and other radiation sources are used in the treatment of cancer and related diseases.

Branch of medicine that uses radiation for diagnosis (diagnostic imaging) and treatment (radiation therapy) of disease. Originally, it involved X rays for diagnosis and X rays, gamma rays, and other ionizing radiation for treatment. Diagnostic methods now include isotope scanning (see nuclear medicine), use of nonionizing radiation, as in ultrasound and magnetic resonance imaging, and radioimmunoassay (in which radioactive isotopes in antibodies against hormones detect minute amounts of hormones for diagnosis of endocrine disorders). Radiotherapy now includes, in cancer treatment, radioactive hormones and chemotherapeutic drugs.

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