Gamma Knife Radiosurgery


Gamma Knife does not actually involve cutting a tumor with a knife or scalpel. Instead the procedure, also known as stereotactic radiosurgery, uses high-energy gamma rays to pinpoint and destroy tumors or other brain abnormalities.

The UW Medicine Gamma Knife Center at Harborview offers the la​test Gamma Knife technology, the Gamma Knife Icon. This system uses 192 emitting sources of cobalt-60. Although the beam from each of these sources is relatively weak and does not damage tissue, when focused together, the combined beams can help destroy or contain the tumor while sparing nearby healthy tissue and other parts of the brain.

With the help of computerized imaging, our neurological surgery and radiation oncology team is able to map the exact location of the lesion or lesions and then direct the beams at the tumor with extreme accuracy.

Gamma Knife is particularly effective in reaching small, localized tumors deep inside the brain that would otherwise be difficult to reach. Gamma Knife radiosurgery is most commonly used for:

Procedural Details

At UW Medicine, we use the latest in Gamma Knife technology: the Gamma Knife Icon system. Patients may wear a head frame using four pins or screws to hold the frame in place. This allows treatment to be completed in one day. It is the best option for some conditions, including when there is more than one area in the brain to be treated. Local anesthesia and sedation are used for frame placement. These are customized for patient needs. With the Icon system, another option is for treatment with a specially-fitted face mask. Our mask-based treatment is completely painless, no pins are required, and treatment may be divided or “fractionated” to allow for recovery between fractions. Treatments are typically completed in 1-5 days.

Your care team will explain all options in detail and help you understand what is best for you

Image mapping and planning

Imaging, which may include MRI, CT and/or a cerebral angiogram, is used to locate the target area or areas. Once the targets are located, treatment planning software is used to create three-dimensional models of the brain. These models closely match the shape of the tumor or the affected area(s). Then a prescription dose is determined. This dose will be dependent upon the type of lesion or lesions, location, size and any prior therapy.


During treatment, while radiation is being delivered, the patient is monitored by a video and a two-way intercom that allows the patient to talk with the physician. When the procedure is completed, the head frame or mask is removed and the patient is evaluated and prepared for discharge. Many patients return to their normal activities the following day.

It may take many weeks or even up to several years before the effects of Gamma Knife treatment become apparent. The patient’s progress is monitored through follow-up imaging studies.


Occasionally, patients experience swelling around the areas in the brain that have been treated. Steroid medications may be prescribed to help treat this type of swelling.


More than 500,000 patients have been treated worldwide with a variety of different types of tumors and AVMs. Patients with the following conditions may be candidates for the Gamma Knife procedure:

  • Acoustic neuromas
  • Arteriovenous malformations
  • Astrocytomas
  • Craniopharyngiomas
  • Epilepsy
  • Essential Tremor
  • Gliomas
  • Meningiomas
  • Metastatic brain tumors
  • Pineal tumors
  • Pituitary tumors
  • Skull base tumors
  • Trigeminial neuralgia
​ A multidisciplinary team of radiation oncologists and neurosurgeons will determine if Gamma Knife is the best option for each particular patient.

Treating children

Some brain lesions in pediatric patients are suitable for Gamma Knife. For our young patients, general anesthesia is used and patients go home the same day.

Consultation and referrals

Typically, patients are seen in consultation initially by a neurosurgeon and/or a radiation oncologist. In addition, our radiosurgery panel may review a case. After further evaluation—which can include MRI, functional MRI, CT, angiography or neuropsychological testing—the appropriate method of therapy is tailored for each individual's needs.


Gamma Knife is used most effectively in the treatment of small intracranial tumors. 
Gamma Knife may also be used in the treatment of lesions that cannot be reached by conventional surgery. It can be used along with other forms of radiation therapy, and with conventional surgery when complete removal of a tumor is not possible. It can be used multiple times in the treatment of recurrent tumors. Gamma Knife may also be used to help stop the growth of brain metastases from cancer. 

The patient’s recovery depends on the size, type, and and number of abnormalities treated, ranging from a few weeks to several years. Many abnormalities shrink or disappear gradually and others just stop growing. However, in some cases, the tumor or AVM might not respond to Gamma Knife therapy.


Some side effects a patient may experience after Gamma Knife treatment include: 
  • Fatigue
  • ​Nausea
  • Headache
  • Skin or scalp irritation
  • Patchy hair loss
  • Neck stiffness
  • Pain or swelling at the frame securing sites
  • Swelling around the treated areas of the brain


The decision to use Gamma Knife radiosurgery should be made after careful consideration with your doctor. The procedure may be used to treat brain tumors or other brain abnormalities, or it may be used to help control the spread of cancerous cells in the brain.


The UW Medicine Gamma Knife Center’s dedicated physicians, nurses and care coordination team provide sensitive, compassionate, lifetime patient support with nearly 100 percent​ patient satisfaction. The team facilitates ongoing follow-up with patients and referring providers. We work closely with allied teams at Alvord Brain Tumor Center, University of Washington Medical Center and Seattle Cancer Care Alliance, including the Proton Center. We can often schedule patients for consult and Gamma Knife treatment within 1-2 weeks and will expedite urgent situations.