Stereotactic Radiosurgery

Gamma Knife™ Treatment at Mayo Clinic

Gamma Knife Machine™

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Control Desk

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At Mayo's Gamma Knife™ Center, neurosurgery is performed without an incision. Instead, the surgeon uses gamma radiation to destroy diseased tissue while preserving the surrounding healthy tissue. Gamma Knife™ is one type of stereotactic radiosurgery. Mayo Clinic in Rochester is one of the most experienced gamma knife centers in the United States. Since 1990, more than 4,000 patients have received gamma knife surgery at the Mayo Clinic.

Brain metastases is the condition most commonly treated with Gamma Knife™. For benign tumors such as acoustic neuromas, meningiomas and pituitary adenomas, tumor control is achieved in more than 95 percent of cases.

Latest Technology

The latest version of the Gamma Knife™ was installed at Mayo Clinic in September 2007. With Gamma Knife™, the radiation source remains stationary and the patient is moved to accommodate radiation delivery. The new device automatically adjusts patient position, saving time and reducing the chance of human error. As a result, a treatment which took 2 hours to perform in the past can now be done in approximately 50 minutes. The larger size of this machine also increases its range, allowing doctors to treat multiple tumors in a single setting, as well as a larger number of head and neck tumors, including certain eye conditions.

See conditions treated with stereotactic radiosurgery.

How Gamma Knife™ Works

Gamma Knife™ treatment results

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One hundred ninety-two beams of radiation are delivered through holes in a helmet (collimator unit) inside the Gamma Knife™. Highly sophisticated computer software is used to determine the size, location and shape of the area to be treated. Only at the point where the radiation beams intersect is the treatment dose of radiation delivered, sparing the surrounding tissue.

Gamma Knife™ surgery involves a team of medical experts from neurosurgery, radiation oncology and radiation physics.

Results of Gamma Knife™ Treatment

Mayo Clinic researchers have published numerous studies documenting the results of Gamma Knife™ radiosurgery treatment for many diseases and conditions. Below are links to abstracts of these studies on PubMed, part of the National Library of Medicine.

What to Expect During Gamma Knife™ Treatment

Preparation Patients are admitted to Saint Marys Hospital the morning of the procedure. Like most surgical procedures, patients wear a hospital gown and remove jewelry, eyeglasses, contact lenses, dentures, wigs or hairpieces. Patients will receive a mild sedative through an IV.

Headframe application Patients are fitted for a lightweight frame which holds the head still during the procedure. A local anesthetic is injected in the four areas where the frame is attached to the head with mounting pins.

Patients feel slight pressure during the headframe application, but this sensation usually goes away when the headframe is in place. Patients are able to move their heads after the headframe is applied.

Imaging to pinpoint the target This may include CT (computed tomography), MRI (magnetic resonance imaging) and cerebral angiography. Patients may have had these studies performed before, but they must be repeated with the headframe in place to precisely map the area to be treated.

Computerized dose planning Physicians use computers to plan the radiation so it matches the desired target. Dose planning generally takes less than one hour.

Treatment When the radiation plan is ready, patients lie on the Gamma Knife™ couch and are positioned into a guiding device that holds their heads securely in the Gamma Knife™ helmet.

After patients are in position, the staff go into an adjoining room to monitor the procedure with video cameras and an intercom system. Patients can talk to the physicians or nurses throughout the procedure.

The number of minutes that each radiation dose lasts is determined during dose planning. The procedure usually includes multiple doses that are delivered one after the other, all on the same day.

Afterwards The headframe is removed and the patient's head is wrapped with gauze to apply pressure to each pin site. This head wrap remains in place for about two hours.

Most patients are discharged from the hospital the same day. Generally patients experience no immediate side effects from the Gamma Knife™ procedure other than a mild headache or nausea.