Tomotherapy

Tomotherapy is a type of radiation therapy delivered by a treatment machine in which a thin radiation beam is modulated as it rotates around the patient while the patient is moved through the bore of the machine. The name comes from the use of a strip-shaped beam so that only one slice, from the Greek prefix tomo-, of the target is exposed to radiation at any one time, and the external appearance of the system and the movement of its radiation source and patient can be considered analogous to a CT scanner, which uses much lower radiation doses for imaging rather than treatment. Like a conventional external beam radiotherapy machine built around a linear accelerator, a tomotherapy machine generates the radiation beam, but its external appearance, patient positioning and treatment delivery differ, since conventional linear accelerators do not work slice by slice but typically use a large-area beam that can also be resized and modulated.