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Stereotactic radiosurgery is a form of radiation therapy that focuses high-powered x-rays on a small area of the body. With regular radiation therapy treatment, healthy tissue that is nearby also receives radiation. Stereotactic radiosurgery better focuses the radiation on the abnormal area.

Despite its name, it is considered a form of radiation therapy, not a surgical procedure.

Alternative Names:

Gamma knife; Cyberknife; Stereotactic radiotherapy; Fractionated stereotactic radiotherapy; Cyclotrons; Linear accelerator; Lineacs; Proton beam radiosurgery


During treatment, you will lie on a table, which slides into a machine that delivers radiation beams. The machine may rotate around you while it works.

Sometimes, a head frame may be attached to your scalp to keep you very still during therapy. There are different machines used to perform stereotactic radiosurgery. Some require the use of a frame, and others do not.

At other times, a special plastic mask fitted for your face may be used.

  • You may need small pins or anchors that go through your skin but not into your skull or bone. If this is done the area will be cleaned, your skin will be numbed and you may be given medicine to help you relax. Even so, you will be awake and able to talk.
  • An MRI , MR angiography, or CT scan is then done to help plan the procedure. You will wait while your doctor reviews the results and plans your treatment.
  • During the actual treatment, you will be alone in the room. The nurses and doctors will be able to see you and talk with you.

The entire procedure, including the planning stage, takes about half a day or less. The time period when you are receiving the radiation is usually only about 30 minutes. Some patients receive therapy more than once.

Why the Procedure Is Performed:

It is often used to slow down the growth of small, deep brain tumors that are hard to remove during surgery. Such therapy may also be used in patients who are unable to have surgery, such as the elderly or those who are very sick. Radiosurgery may also be used after surgery to treat any remaining abnormal tissue.

Stereotactic radiosurgery was once limited to brain tumors, but today it may be used to treat other diseases and conditions, including:


Radiosurgery may damage tissue around the area being treated. Brain swelling may occur in people who received treatment to the brain. Swelling usually goes away, but some people may need medicine to control long-term swelling.

Before the Procedure:

Before the treatment, you will have MRI or CT scans. Using these images, a computer creates a 3-D (three dimensional) map of the tumor area. This planning process helps your neurosurgeon and radiation oncologist to determine the specific treatment area.

The day before your procedure:

  • Do not use any hair creams or hair spray.
  • Do not eat or drink anything after midnight unless told otherwise by your doctor.

The day of your procedure:

  • Wear comfortable clothing.
  • Bring your regular prescription medicines with you to the hospital.
  • Do not wear jewelry, make-up, nail polish, or a wig or hairpiece.
  • You will be asked to remove contact lenses, eyeglasses, and dentures.
  • You will change into a hospital gown.
  • An intravenous (lV) line will be placed into your arm to deliver contrast material, medicines, and fluids.

After the Procedure:

Often, you will be able to go home about an hour after the treatment is finished. You should arrange for someone to drive you home. Most people go back to their regular activities the next day, if there are no complications such as swelling. Some patients are kept in the hospital overnight for monitoring.

Outlook (Prognosis):

The effects of radiosurgery may take weeks or months to be seen. The prognosis depends on the condition being treated. Many times, your health care provider will monitor your progress using imaging tests such as MRI and CT scans.


DeAngelis LM. Tumors of the Central Nervous System and Intracranial Hypertension and Hypotension. In: Goldman L, Ausiello D. Goldman: Cecil Medicine. 23rd ed. Philadelphia, PA: Saunders Elsevier;2007:chap 199.

Kavanagh BD, Timmerman RD. Stereotactic radiosurgery and stereotactic body radiation therapy: an overview of technical considerations and clinical applications. Hematol Oncol Clin North Am. 2006;20:87-95.

Romanelli P, Anschel DJ. Radiosurgery for epilepsy. Lancet Neurol. 2006;5:613-620.

Sneed PK, Kased N, Huang K, Rubenstein JL. Brain metastases and neoplastic meningitis. In: Abeloff MD, Armitage JO, Niederhuber JE, Kastan MB, McKena WG, eds. Clinical Oncology. 4th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2008:chap 52.

Zivin JA. Hemorrhagic Cerbrovascular Disease. In: Goldman L, Ausiello D. Goldman: Cecil Medicine. 23rd ed. Philadelphia, PA: Saunders Elsevier;2007:chap 432.

Review Date: 1/22/2009
Reviewed By: Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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789 Central Avenue, Dover, NH 03820
Phone: (603) 742-5252
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