See radiosurgery.
A high-precision method of radiation therapy in which several powerful beams of radiation located at different angles around the head come together to focus precisely on a brain tumor.
A form of IGRT which involves attachment of an external device with precisely known geometry to the head or the body. After imaging the patient with the device attached, a tumor may be precisely targeted based upon the relationship of its location to the external device. An arrangement of narrow X-ray, gamma ray, or particle beams is designed which only intersect through the tumor. A large dose of radiation is delivered with little or no set-up margin in a single treatment.