Ionizing radiation has two very different uses in medicine namely diagnosis and therapy. Both are intended to benefit patients and, as with any use of radiation, the benefit must outweigh the risk.
Most people at some time in their lives have an X ray examination to help the physician diagnose disease or damage in the body. A much less common diagnostic procedure involves the administration of radionuclides to patients so that, detectors outside the body can be used to observe how organs are functioning. Physicians use either of these procedures if they cannot make a diagnosis without them. Radiation doses are generally low, although they can be appreciable in certain procedures.
Much higher doses are required to treat malignant diseases or malfunctioning organs sometimes in combination with other forms of treatment. A beam of radiation may be used to irradiate the affected part of the body or a fairly high activity of a radionuclide may be administered to the patient.
The use of X rays for examining patients is called diagnostic radiology and the use of pharmaceuticals labelled with radionuclides for diagnosis or therapy is called nuclear medicine. When radiation beams are used to treat patients, the procedure is called radiotherapy.
Table (10) : Radiation exposures from diagnostic medical procedures (UNSCEAR 2000 Report to the General Assembly )