The Gamma Knife is an advanced radiation treatment for adults and children with small to medium brain tumors, abnormal blood vessel formations called arteriovenous malformations, Parkinson's disease, trigeminal neuralgia, a nerve condition that causes chronic pain, and other neurological conditions.

Despite its name, the Gamma Knife isn't a knife but is a machine that delivers a single, finely focused, high dose of radiation 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 with no overnight hospital stay.

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 have been treated using this state-of-the-art equipment. Now, 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 UCSF 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.

Preparing for Gamma Knife

If you undergo this treatment, there are many things you will need to do to prepare for a Gamma Knife procedure. One to two days before the procedure, you will need to visit the hospital for blood tests and to meet with the doctors who will perform the procedure. You will also meet with a neurosurgeon and a radiation oncologist. Each doctor will record your medical history, perform a physical examination and obtain your consent to perform the Gamma Knife procedure. You will have an opportunity to tour the Gamma Knife treatment room and ask questions about the procedure and expected results.

The Night Before Treatment

Do not eat after 2 a.m. Take your regular medications the day before and the morning of the procedure with a small amount of water.

Morning of Treatment

Typically, you will be in the hospital only for the day of the procedure. Bring your medications so you can take them during the day as needed. Slipper-socks and robes are provided. Please bring reading materials, music CDs or tapes, or a video to watch in the patient waiting area. Remember to leave your valuables, such as jewelry and large sums of cash, at home.

An escort will take you to the fourth floor pre-operative area. A family member or friend may accompany you there. You will be asked to put on a hospital gown and a nurse will start an intravenous (IV) line through which you will receive fluids and a mild sedative during the procedure. The same IV is used to administer the contrast agent for your imaging studies.

Procedure

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.

You will check into the Gamma Knife program early in the morning. An intravenous line will be inserted into a vein. The neurosurgeon will use local anesthesia to numb four spots on your scalp and forehead before attaching a "stereotactic frame." This frame allows highly precise treatment. You 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, you will lie on a treatment couch. Your 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.

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

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

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

Reviewed by health care specialists at UCSF Medical Center.
Last updated March 8, 2012