Stereotactic Radiosurgery – A form of radiation where multiple radiation beams are p assed along corridors to intersect at a target. The summation dose of the multiple beams at the point of their intersection is typically necrosing to the tissue within this “target” zone. The stereotactic or stereotaxis referes to using the 3-D coordinate grid defined by the imaging computer (MRI or CT) to calculate the corridor pathway and what tissue it passes through and to define the geometry of the target zone.