Gamma Knife is a type of radiation treatment known as stereotactic radiosurgery that destroys a brain or pituitary tumor without opening the skull as in traditional open surgery.

A CT or MRI scan is used to pinpoint the exact location of the tumor in the brain. High-energy radiation beams are trained on the tumor from different angles. The radiation destroys the tumor.

Radiosurgery is called "surgery" because it is a one-session radiation therapy treatment with similar results to an open surgical procedure. The advantage of knifeless procedures is that they have fewer complications and the recovery time is much shorter.