Gamma Knife Explained


Gamma Knife radiosurgery is usually a one-time therapy completed in a single day. Most patients can return to activity after 24 hours.

The procedure may take less than an hour to about four hours, depending on the size and shape of the target. During the procedure:

  • You won’t feel the radiation
  • You won’t hear any noise from the machine
  • You’ll be able to talk with the doctors via a microphone
  • You can listen to music during the treatment

Gamma Knife radiosurgery is an outpatient procedure, but the entire process can take most of a day. You may be advised to have a family member or friend who can be with you during the day and who can take you home.

Treatment Explained

Advantage of Gamma Knife

Gamma Knife® radiosurgery is done only for tumors and other medical problems of the head. For tumors and problems elsewhere in the body, other radiosurgery systems may be used. Gamma Knife® surgery represents a major advance in brain surgery, and in the last three decades has changed the landscape within the field of neurosurgery. Its development has enhanced neurosurgical treatments offered to patients with brain tumors and vascular malformations by providing a safe, accurate and reliable treatment option. Gamma Knife® enables patients to undergo a non-invasive form of brain surgery without surgical risks, a long hospital stay or subsequent rehabilitation.

The clinical effectiveness of Gamma Knife® has been documented over four decades. More than 1,000,000 cases have been treated worldwide, providing data for over 4,000 publications in peer-reviewed medical literature.

Gamma Knife® surgery is unique in that no surgical incision is made to expose the inside of the brain, thereby reducing the risk of surgical complications and eliminating the side effects and dangers of general anesthesia. The “blades” of the Gamma Knife® are the beams of gamma radiation programmed to target the lesion at the point where they intersect. In a single treatment session, 192 beams of gamma radiation focus precisely on the lesion. Over time, most lesions slowly decrease in size and dissolve. The exposure is brief and only the tissue being treated receives a significant radiation dose, while the surrounding tissue remains unharmed.

With the Gamma Knife®, a surgical incision is not required; the attendant risks of open neurosurgical procedures (hemorrhage, infection, cerebrospinal fluid leakage, etc.) are therefore avoided.

Conditions for which the Gamma Knife® is considered most effective are:

  1. Intracranial tumors such as acoustic neuromas, pituitary adenomas, pinealomas, craniopharyngiomas, meningiomas, chordomas, chondrosarcomas, metastases and glial tumors.
  2. Vascular malformations including arteriovenous malformations.
  3. Functional disorders such as trigeminal neuralgia and obsessive-compulsive disorder.

The Gamma Knife® technology can be used to treat those who do not require urgent surgical care for disabling symptoms and those whose tumors are, in general, 3 cm or less.

As an example, Meningiomas are the most common benign brain tumors. Gamma Knife® has a 95% control rate for the treatment of meningiomas. The following images show the decrease in meningioma after Gamma Knife® treatment.

Leksell Gamma Knife® is a registered trademark of Elekta Instruments, Inc.

Novalis Tx®, CyberKnife®, TomoTherapy®

Linac is short for the term linear accelerator. Linear accelerator machines produce radiation that is referred to as high energy X-ray. A linear accelerator machine is designed to be a general purpose radiation delivery machine (not brain specific like the Gamma Knife®)  and in general requires modifications to enable it to be used for radiosurgery.

Radiosurgery can be performed with linear accelerator machines but requires 2-5 treatments versus 1 treatment with Gamma Knife®. The tumor receives a very high one time dose of radiation with radiosurgery, and smaller doses over time with radiation therapy. This can result in more side effects, some of which may be permanent. More importantly, a reduced amount of radiation delivered to the tumor with each radiation therapy treatment, rather than a very high one time dose using the Gamma Knife®, can result in less tumor control and poorer outcomes than with radiosurgery.

Because of the significant risks associated with millimeter errors in targeting for the brain, Gamma Knife® surgery combines physical immobilization of the patient’s head with ultra-accurate targeting and delivery. The most important measurement of accuracy is the total clinical accuracy. This is an end-to-end measurement combining mechanical and radiological accuracy plus imaging. Gamma Knife®’s average achievable clinical accuracy is 0.48mm compared to CyberKnife®’s linac machine average total of 2.10mm. The precision of brain stereotactic Gamma Knife® radiosurgery results in minimal damage to healthy tissues surrounding the target.

San Diego Gamma Knife Center

Contact Us

Ask us any questions or request more information!
Coming from out of town? Let us know and we can assist with accommodations during your stay.

San Diego Gamma Knife Center


9834 Genesee Ave. #110
La Jolla, CA 92037




3 + 5 =