radiotherapy

Treatment of disease by radiation from X-ray machines or radioactive sources. Radiation in the correct dosage can be used to kill cancerous cells and prevent their spreading.

Generally speaking, the rays of a diagnostic X-ray machine are not penetrating enough to be efficient in treatment, so for this purpose more powerful machines are required, operating at from 10,000 volts 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 intestine, diarrhoea and vomiting may occur. Much radiation now comes from synthesized radioisotopes. Radioactive cobalt is the most useful, because it produces gamma rays, which are highly penetrating, and it is used instead of very high-energy X-rays.