Adenoid Cystic Carcinoma Organization International 
Stereotactic Radiosurgery (SRS)
In reading information available from both radiation manufacturers and treatments centers, the word "Radiosurgery" is not used consistently. But according to many treatment centers, SRS is a precise radiation delivery system used only for brain and spine and is delivered in a single treatment, also known as a single "fraction". Gamma Knife was the very first platform used for brain tumors, and is the classic and widest used SRS platform. The GammaKnife is used exclusively to treat brain lesions and not any other area of the body. Some of the newer platforms such as Varian Trilogy, Novalis TX and CyberKnife can be used for SRS as well as having the additional flexibility to treat other areas of the body, which is called Sterotactic Body Radiation Therapy. SRS has been defined by various treatment centers and manufacturers in various ways with some emphasizing the region treated while others emphasize the single fraction treatment dose as being the defining component.
Below are brochures from Elekta and Varian who each manufacture radiation treatment equipment that is used for treating tumors in the brain and spine. There are other manufacturers platforms that treat brain lesions as well with many updates, features and new equipment being developed.