Gamma Knife Radiosurgery

The Gamma Knife is an advanced radiation treatment for small- to medium-size brain tumors, abnormal blood vessel formations called arteriovenous malformations and other neurological conditions.

Despite its name, the Gamma Knife isn't a knife but is a machine that delivers a single, very finely focused, high dose of radiation precisely to its target, while causing little or no damage to surrounding tissue. Abnormalities measuring 1 inch in diameter — the size of a small pebble — can be treated with the Gamma Knife.

Today, patients with serious disorders can be treated with this noninvasive procedure in one day on an outpatient basis.

UCSF, which launched its Gamma Knife Radiosurgery Program in 1991, was the first medical center in Northern California to use a Leksell Gamma Knife to treat brain disorders. Since then, more than 3,000 patients, including children, have been treated using this state-of-the-art equipment. UCSF has acquired the newest Gamma Knife, called the Leksell Gamma Knife Perfexion. It offers the most precise treatment along with improved patient comfort and treatment efficiency.

The new machine allows neurosurgeons to treat more areas of the head and neck. Doses of radiation can be delivered to multiple target areas in one session, avoiding the need to move the patient or adjust the machine. This reduces the time a patient has to spend undergoing treatment and reduces discomfort.


The technique that permits this precise targeting within the brain is called stereotaxy. Stereotactic radiosurgery is performed with the aid of imaging techniques called computerized tomography (CT) scanning, magnetic resonance imaging (MRI) and angiography. These are used together with special computer-assisted instruments to provide 3-dimensional views of the target and surrounding brain structures. By studying these images, your doctor can locate the abnormality within the brain accurately, then precisely focus the gamma radiation beams on the abnormality.

If your child undergoes this treatment, you and your child will check into the Gamma Knife program early in the morning. An intravenous line will be inserted into a vein to administer anesthesia before the neurosurgeon attaches a "stereotactic frame" to your child's head. This frame allows highly precise treatment.

Children remain asleep during the Gamma Knife procedure. A neuro-anesthesiologist gives the anesthesia and stays with your child throughout the procedure.

Your child will undergo brain imaging that enables the doctors to delineate the target or targets for treatment. A Gamma Knife treatment plan will be developed with sophisticated computer software.

When the treatment is administered, your child will lie on a treatment couch. Your child's head will be held still during the session while 192 small radiation beams are focused simultaneously at the target. The size of the focal spot can be adjusted and multiple focal spots can be combined together to deliver a high radiation dose precisely to one target or to multiple targets of almost any shape, anywhere in the brain.

The principles of Gamma Knife treatment for children are the same as those for adults, but special care is provided, including imaging studies before treatment and anesthesia tailored for children.

Radiation exposure to other parts of the body is extremely low, making it an excellent option for children and women of child-bearing age.


Abnormalities that are treated effectively with the Gamma Knife include:

  • Benign brain tumors that grow slowly and do not tend to invade surrounding normal brain tissues, such as meningiomas, acoustic neuromas, pituitary adenomas, craniopharyngiomas and low-grade astrocytomas
  • Primary or recurrent malignant brain tumors, including glioblastoma and anaplastic astrocytoma
  • Solitary and multiple brain metastases
  • Ateriovenous malformations (AVMs)
  • Some cases of epilepsy

Patients who are candidates for Gamma Knife treatment are evaluated by a team of specialists including experienced neurosurgeons, radiation oncologists, physicists, neuro-radiologists, neuro-oncologists, nurses and radiation therapists.

Factors considered in the evaluation include age and general medical condition, location and size of the abnormality and previous treatments.

Some conditions may be treated with another non-invasive radiosurgery device called the CyberKnife that uses a robotic arm to deliver highly focused beams of radiation. At UCSF Benioff Children's Hospital, the CyberKnife is being used to treat areas of the body such as the spine and spinal cord that can't be treated by other radiosurgery techniques.

If your child is treated at UCSF, your child's referring doctor plays an important role in planning the treatment. When you are being considered, your child's doctor is consulted to be certain that all variables affecting your therapy are taken into consideration. During your stay with us, your child's doctor is kept informed about your progress, assuring continuity and coordination of the care provided.


Reviewed by health care specialists at UCSF Benioff Children's Hospital.

Related Information

UCSF Clinics & Centers

Pediatric Brain Center

Pediatric Brain Tumor Center
1825 Fourth St., Sixth Floor
San Francisco, CA 94158
Phone: (415) 353-2986
Fax: (415) 353-2657

Condition Information

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