Stereotactic Radiosurgery
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Stereotactic Radiosurgery

(Gamma Knife™ Treatment; CyberKnife® Treatment)


Stereotactic radiosurgery is a technique to treat brain disorders. It uses a highly focused beam of radiation to target specific areas of the brain. The beam of radiation destroys the tissue that a surgeon would otherwise have remove with a scalpel during an operation.

Treatment involves a team of specialists including:

  • Radiation oncologist—makes the treatment plan, ensures the dose delivered is appropriate, maintains the NRC license for dose administration
  • Neurosurgeon—often places the head frame for brain treatment delivery, and assists with planning
  • Medical Radiation Physicist—assists the radiation oncologist with dose prescription, maintains the actual radiation machine (gamma knife unit or linear accelerator)
  • Dosimetrist—specifically works on the radiation dose prescription
  • Radiation therapist—operates the machinery
  • Radiation Therapy Nurse—assists the radiation oncologist with direct patient care
  • Neurologist or Neuro-Oncologist—assists the neurosurgeon and radiation oncologist with the elements of brain tumors, such as seizure control and rehabilitation

Parts of the Body Involved

  • Head
  • Brain
  • Blood vessels (veins and arteries) in the brain
  • Spine

Reasons for Procedure

Stereotactic radiosurgery is used to:

  • Stop benign and malignant tumor growth
  • Shrink benign and malignant tumors
  • Close off arteriovenous malformations (AVMs)—abnormal blood vessels that disrupt blood flow to the brain
  • Treat functional disorders such as:

Brain Tumor

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Risk Factors for Complications During the Procedure

Although the risk for complications is low, advanced age, chronic medical conditions, and previous surgeries at or near the target site may increase the risk for complications.

What to Expect

Prior to Procedure

Your doctor will likely do the following:

  • Perform a neurological exam, to see how well your nervous system is functioning
  • Review your x-rays or other diagnostic test results
  • Order additional tests if necessary

Your doctor may ask if you:

  • Take medication or insulin to control diabetes
  • Are allergic to intravenous contrast material—an injected substance that can make a tumor or other abnormality easier to see
  • Are allergic to iodine or shellfish (iodine is present in both shellfish and contrast material)
  • Have a pacemaker or any other medical device implanted in your body
  • Have eye or ear implants
  • Have had any previous surgeries
  • Have ever had trauma to the skull
  • Suffer from claustrophobia

In the days leading up to your procedure:

  • Review your regular medications with your doctor; you may be asked to stop taking some drugs
  • Arrange for someone to:
    • Drive you to the treatment facility
    • Drive you home afterward
    • Stay with you during treatment
    • Stay with you the following night
    • You may be given a special shampoo to use on your hair

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 medications with you to the hospital
  • Do not wear jewelry, make-up, nail polish, a wig, or a hairpiece
  • You will be asked to remove any contact lenses, eyeglasses, and dentures
  • You will change into a hospital gown
  • An intravenous (lV) line will be inserted into your arm to deliver contrast material, medications, and fluids


  • You will receive a mild sedative, orally or through an IV, to help you relax
  • A local anesthetic may be injected to numb your scalp

Description of the Procedure

There are three types of stereotactic radiosurgery:

Cobalt-60-based Treatment (commonly called Gamma Knife™ Treatment)

The procedure is performed using 201 beams of highly focused gamma rays. It is used to treat smaller brain tumors and functional brain disorders. The Gamma Knife™ is the most well-known machine used for this procedure.

There are four phases to this treatment:

  • Head frame placement—Local anesthesia is injected into the front and back of your head to numb your scalp. Then, a box-shaped, aluminum frame is attached to your skull with special pins to keep your head from moving during treatment.
  • Imaging—You will have a computed tomography (CT) scan and/or magnetic resonance imaging (MRI) to pinpoint the exact location of the tumor. If you are being treated for an AVM, you will have a test called an angiography, to locate the abnormal veins.
  • Computerized dose planning—You will relax for about an hour while your doctors plan your treatment. When they are finished, you will lie down on a special couch. Your doctor will talk to you about the number of treatments you will receive and how long they will take. Your head frame will then be attached to a helmet full of small holes. Each will allow a single ray of radiation to target a specific part of your brain.
  • Radiation delivery—The doctors and nurses will leave the room. Your couch will move into the treatment area. You might hear a click as the helmet locks into place. Your doctor will be able to see and hear you during the entire procedure, and you will be able to talk to him or her. You will remain still during the procedure, and so will the machinery around you. You will not be able to see, feel, or hear the treatment being performed. When treatment is complete, the couch will move back to its original position.

Linear accelerator (LINAC)-based Treatment

This treatment utilizes one large, powerful radiation beam. It is used to treat larger brain tumors. You will go through the same phases listed above. During radiation delivery, however, part of the machine will move around you. The treatment couch will also be repositioned.

CyberKnife® Treatment

CyberKnife® treatment is given using a small linear accelerator mounted on a robotic arm. It is used to treat tumors and lesions of the brain and spine. No head frame is used.

There are three phases to treatment:

  • Set-up—If you are being treated for a brain tumor, a special mask will be made to fit your head. No pins are needed to keep it in place. You will be given a CT scan, and possibly an MRI, with the mask in place. If you are being treated for a spinal tumor, a customized foam body cradle will be made, instead of a mask. You will most likely have some small metal markers, called fiducials, implanted near the tumor to help guide the radiation beams during treatment. The fiducials are implanted during a short outpatient procedure. After they are in place, you will be given a CT scan.
  • Treatment planning—You may be allowed to go home while the doctors finalize your treatment plan. Actual treatment may take place that same day or several days after the set-up phase.
  • Treatment delivery—You will be fitted with your mask or body cradle and then lie down on the treatment table. Before the treatment starts, x-rays will be taken to help the linear accelerator move into the proper position. Once treatment begins, the robotic arm will move around you and administer radiation beams from many different angles. Sometimes the arm will stop and more x-rays will be taken.

After Procedure

If you received Gamma Knife™ or LINAC-based treatment:

  • The head frame and IV line will be removed.
  • Your head will be wrapped in gauze, or small bandages will be placed at the pin sites, where the pins secured the frame to your head.

How Long Will It Take?

  • Radiation delivery can take up to 2 hours for Gamma Knife™ and LINAC-based treatments. For Cyberknife® treatments, it can take up to 3 hours.
  • The total procedure usually takes 2 to 4 hours.

Will It Hurt?


  • Anesthesia prevents pain at the pin sites, if a head frame is used during treatment.
  • You will feel some pressure as the head frame is attached.
  • The treatment itself causes no pain.
  • You may experience headaches or nausea a few hours after treatment, but will receive medication to relieve any discomfort.

Possible Complications

Typically, there are no complications. If any do occur, they are usually mild. Complications can vary, depending on your diagnosis. They may include:

  • Headache
  • Scalp pain
  • Temporary swelling in the treatment site—caused when tumors lose their ability to regulate fluids after treatment
  • Swelling, numbness, or tingling around pin sites
  • Bleeding at pin sites
  • Skin irritation
  • Nausea
  • Seizures
  • Necrosis—dead tumor tissue that may need to be removed
  • Patchy hair loss from the radiation

Rare complications may include:

  • Vision loss
  • Deafness
  • AVMs that start bleeding again
  • Nerve problems

Average Hospital Stay

You can usually leave the hospital after a short observation period, but be prepared to stay overnight if necessary.

Postoperative Care

  • You can typically return to your regular daily activities the day after the procedure.
  • Resume your regular medications, unless told otherwise by your doctor.
  • Check with your doctor about performing any heavy lifting.
  • For about a week, avoid scrubbing the pin sites when you wash your hair.


Stereotactic radiosurgery works over time. It may take several months to several years to see results.

  • About one month after your procedure, your doctor will check your pin sites and perform a neurological exam.
  • Your first CT scan or MRI will be done about six months after your procedure, to check how well you are responding to treatment.
  • CT scans or MRIs will likely be performed after the procedure to assess for treatment effect. The number of scans and frequency with which you get them depends upon your doctor’s opinion and experience.
  • If you were treated for an AVM, you will have a test called a cerebral angiogram two to three years after treatment, to determine if treatment was successful.
  • In many cases, stereotactic radiosurgery treatments can be performed again, if necessary.

Call Your Doctor If Any of the Following Occurs

It is essential for you to monitor your recovery once you leave the hospital. That way, you can alert your doctor to any problems immediately. If any of the following occur, call your doctor:

  • Seizures
  • A new onset of numbness
  • Weakness
  • Loss of balance
  • Severe headache
  • Vision problems


American Association of Neurological Surgeons

Stereotactic Radiosurgery

Stereotactic Radiosurgery and Radiotherapy
Cleveland Clinic


International Radiosurgical Association

Stereotactic Radiosurgery Program
Dalhousie University


CyberKnife® Stereotactic Radiosurgery System. Georgetown University Hospital website. Available at: . Accessed October 4, 2005.

CyberKnife® Stereotactic Radiosurgery System Overview. CyberKnife Society website. Available at: . Accessed October 4, 2005.

Information for Patients. Yale-New Haven Hospital Gamma Knife Center website. Available at: . Accessed September 10, 2005.

Linear Accelerator. RadilogyInfo website. Available at: . Accessed September 9, 2005.

Stereotactic Radiosurgery. American Association of Neurological Surgeons website. Available at: . Accessed September 9, 2005.

Stereotactic Radiosurgery at Mayo Clinic. Mayo Clinic website. Available at: . Accessed September 9, 2005.

Stereotactic Radiosurgery Overview. International Radiosurgical Association website. Available at: . Accessed September 1, 2005.

Stereotactic Radiosurgery Questions and Answers. International Radiosurgical Association website. Available at: . Accessed September 9, 2005.

The CyberKnife®. University of Pittsburgh Department of Neurological Surgery website. Available at: . Accessed October 4, 2005.

What is Stereotactic Radiosurgery? University of Iowa Department of Radiation Oncology Virtual Hospital website. Available at: . Accessed September 9, 2005.

What is Stereotactic Radiosurgery and How is it Used? RadiologyInfo website. Available at: . Accessed September 1, 2005.

Last reviewed March 2008 by Igor Puzanov, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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