What is a Gamma Knife?

Cancers treated:
Brain tumors, cancerous tumors that originate elsewhere in the body but have spread to the brain

Why performed: Gamma Knife “surgery” is a noninvasive alternative to traditional open-brain surgery. The precisely focused radiation beams of the Gamma Knife allow surgeons to treat very small, deep-seated tumors without damaging nearby brain tissue.

Patient preparation: Patients should not eat or drink anything after midnight the night before the procedure. They should inform their doctor if they are taking medication to control diabetes, are allergic to shellfish or iodine, or have implanted medical devices in the body. Patients must remove glasses, contact lenses, jewelry, makeup, nail polish, wigs, and dentures.

Steps of the procedure: Surgeons apply a local anesthetic and use four screws to attach a lightweight frame to the patient’s head. The frame prevents the head from moving and allows surgeons to identify the treatment target accurately. With the head frame in place, surgeons take magnetic resonance images of the brain to establish the exact size, shape, and location of the target. From the images, surgeons develop a specific treatment plan.

For the treatment, the patient lies on a couch. A helmet is attached to the head frame. The couch slides into the Gamma Knife unit, where radiation destroys the tumor. The patient is awake during the procedure, which lasts from a few minutes to more than an hour, depending on the size and location of the tumor.

After the procedure: When the treatment is completed, the head frame is removed. In most cases, the patient goes home the same day and returns to a normal routine in a day or two.

Risks: Because surgeons make no incisions, the risk of complications from use of the Gamma Knife is low. Some patients feel minor soreness from the head frame. Temporary swelling and irritation are also possible. Some patients experience mild headache, dizziness, or nausea, which last only a short while.

The dose of radiation outside the target is very low and poses little risk. Occasionally, patients experience swelling in the brain, which is temporary and treatable.

Results: The effects of radiation treatments take time: weeks, months, or even years.

Allen, Barry, Loredana Marcu, and Eva Bezak. Biomedical Physics in Radiotherapy for Cancer. Collingwood: CSIRO, 2012. Digital file.

"Gamma Knife." Penn Medicine. Trustees of the U of Pennsylvania, 2014. Web. 6 Oct. 2014.

"Gamma Knife." RadiologyInfo. Radiological Soc. of North Amer., 2014. Web. 6 Oct. 2014.

"Gamma Knife—Cobalt-60 Therapy." American Brain Tumor Association. Amer. Brain Tumor Assn., 2014. Web. 6 Oct. 2014.

L'Annunziata, Michael F. Radioactivity: Introduction and History. Amsterdam: Elsevier, 2007. Digital file.

"Understanding Radiation Therapy." Cancer.org. Amer. Cancer Soc., 2 May 2014. Web. 6 Oct. 2014.