External beam radiotherapy or teletherapy is the most common form of radiotherapy. The patient sits or lies on a couch and an external source of radiation is pointed at a particular part of the body. In contrast to internal radiotherapy (brachytherapy), in which the radiation source is inside the body, external beam radiotherapy directs the radiation at the tumour from outside the body. Kilovoltage ("superficial") X-rays are used for treating skin cancer and superficial structures. Megavoltage ("deep") X-rays are used to treat deep-seated tumours (e.g. bladder, bowel, prostate, lung, or brain).
While X-ray and electron beams are by far the most widely used sources for external beam radiotherapy, a small number of centers operate experimental and pilot programs employing heavier particle beams, particularly proton sources.
Read more about External Beam Radiotherapy: Photons, Electrons, Hadron Therapy, Multi-leaf Collimator, Intensity Modulated Radiation Therapy, Image-guided Radiation Therapy
Famous quotes containing the words external and/or beam:
“The burning of rebellious thoughts in the little breast, of internal hatred and opposition, could not long go on without slight whiffs of external smoke, such as mark the course of subterranean fire.”
—Harriet Beecher Stowe (1811–1896)
“Why beholdest thou the mote that is in thy brother’s eye, but considerest not the beam that is in thine own eye?”
—Bible: New Testament Jesus, in Matthew, 7:3.
From the Sermon on the Mount.