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Brain stereotactic radiosurgery

Medically reviewed by Last updated on Jul 21, 2023.


Gamma Knife radiosurgery is a type of radiation therapy. It can be used to treat tumors, veins that have developed differently than usual and other differences in the brain.

Similar to other types of stereotactic radiosurgery (STS), Gamma Knife radiosurgery is not a standard surgery because there is no cut, called an incision.

Instead, Gamma Knife radiosurgery focuses many tiny beams of radiation on a tumor or other target with extreme accuracy. Each beam has very little effect on the brain tissue it passes through. But a strong dose of radiation is delivered to the place where all the beams meet.

Why it's done

Gamma Knife radiosurgery is often safer than standard brain surgery, also called neurosurgery. Standard surgery requires making incisions in the scalp, skull and membranes surrounding the brain, and cutting into brain tissue. This type of radiation treatment is usually performed when:

In most cases, Gamma Knife radiosurgery has fewer side effects compared with other types of radiation therapy. This type of surgery can be done in one day compared with up to 30 treatments with typical radiation therapy.

Gamma Knife radiosurgery is most commonly used to treat the following conditions:


Gamma Knife radiosurgery doesn't involve surgical openings, so it's generally less risky than standard neurosurgery. In standard neurosurgery, there are possible complications associated with anesthesia, bleeding and infection.

Early complications or side effects are usually temporary. Some people experience mild headaches, a tingling sensation on the scalp, nausea or vomiting. Other side effects may include:

How you prepare

Food and medicines

Clothing and personal items

Wear comfortable, loose clothing.

Avoid wearing the following items during the procedure:

Other precautions

Tell a member of your health care team if you:

What you can expect

Before the procedure

Before the procedure begins, a lightweight frame will be attached to your head with four pins. This frame will keep your head stable during the radiation treatment. The frame also will serve as a point of reference for focusing the beams of radiation. During this process:

After the head frame is attached, imaging of the brain is performed to show the location of the tumor or other target in relation to the head frame. The type of scan used depends on the condition being treated:

The results of the brain scans are fed into a computer. A specialized planning program helps the radiosurgery team to figure out which areas to treat, doses of radiation and how to focus the radiation beams to treat the areas. This planning process usually takes less than an hour. During that time, you can relax in another room, but the frame must remain attached to your head.

Children often get medicines to put them in a sleep-like state for the imaging tests and the radiosurgery. Adults are usually awake, but may be given a medicine to help them relax.

During the procedure

You'll lie on a bed that slides into the Gamma Knife machine. The head frame attaches securely to a helmet inside the machine.

You'll get an intravenous (IV) tube that delivers fluids to your bloodstream to keep you hydrated during the day. A needle at the end of the IV is placed in a vein, most likely in your arm.

The time needed to complete the procedure may range from less than an hour to about four hours. It depends on the size and shape of the target. During the procedure:

Radiation oncologist monitoring Gamma Knife procedure

A radiation oncologist monitors the Gamma Knife procedure in progress.

How you prepare

Gamma Knife radiosurgery is usually an outpatient procedure, but the entire process may last into the afternoon. You may be asked to bring along a family member or friend who can be with you during the day and who can take you home. Rarely, you may stay overnight in the hospital.

Gamma Knife delivery of radiation

What you can expect

After the procedure

After the procedure, you might expect the following:


The treatment effect of Gamma Knife radiosurgery occurs slowly, depending on the condition being treated:

Gamma Knife radiosurgery results

Gamma Knife radiosurgery uses multiple tiny beams of radiation to shrink tumors. The left brain scan shows a pretreatment image of a noncancerous tumor — an image enhanced by the use of a special dye, called a contrast agent. At six months after treatment (middle image), the tumor appears slightly larger but doesn't take up as much of the contrast agent — isn't as bright in the center. This indicates a positive treatment effect. At seven years (right scan), the tumor appears much smaller.

Brain AVM before and after Gamma Knife treatment

Brain arteriovenous malformation (AVM) before Gamma Knife treatment (left) and 52 months after the procedure (right)

Brain tumor before and after Gamma Knife treatment

Malignant brain tumor before (left) and 111 months after Gamma Knife stereotactic radiosurgery (right)

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