Radiation therapy administered by a machine that is positioned at some distance from the patient. Typically, a teletherapy unit can rotate around a patient and thus allow use of multiple beams that intersect at the tumor and thus lower the dose to surrounding normal tissue.
Cancer treatment in which the radiation source is placed outside the body.
The term originates from the earlier “radium bomb” X-ray tube, wherein the entire tube is shielded with lead, except for a small designated area from which the radiation is emitted. This shielding technique is still employed today in cobalt therapy.