The Gamma Knife was activated on September 7, 1997, and is used to treat malignant and benign tumors of the brain, vascular malformations, and facial pain conditions. The Gamma Knife is the most accurate instrument available to perform radiosurgery on the brain. 201 individual beams of focused gamma radiation offer a precise treatment, leaving healthy tissue unharmed. The procedure utilizing only a local anesthetic and is usually an outpatient procedure. Patients return to normal activities the next day. For more information, see Gamma Knife.