Medical treatment by X-rays. The treatment of disease (especially cancer) by exposure to radiation; SYN. radiation therapy, actinotherapy, irradiation.
Treatment of disease by radiation from X-ray machines or radioactive sources. Radiation, which reduces the activity of dividing cells, is of special value for its effect on malignant tissues, certain nonmalignant tumors, and some diseases of the skin.
Generally speaking, the rays of the diagnostic X-ray machine are not penetrating enough to be efficient in treatment, so for this purpose more powerful machines are required, operating from 10,000 to over 30 million volts. The lower-voltage machines are similar to conventional X-ray machines; the higher-voltage ones may be of special design; for example, linear accelerators and betatrons. Modern radiotherapy is associated with fewer side effects than formerly, but radiotherapy to the head can cause temporary hair loss, and if the treatment involves the gut, diarrhea and vomiting may occur. Much radiation now given uses synthesized radioisotopes. Radioactive cobalt is the most useful, since it produces gamma rays, which are highly penetrating, and it is used instead of very high-energy X-rays.