The Gamma Knife is an advanced radiation treatment for small to medium primary or metastatic brain tumors, abnormal blood vessel formations called arteriovenous malformations, epilepsy, trigeminal neuralgia, a nerve condition that causes chronic pain, and other neurological conditions.
Despite its name, the device isn't a knife. It precisely delivers a single, very finely focused, high dose of radiation to its target, while causing little or no damage to surrounding tissue.
Gamma Knife treatment consists of six basic steps:
- Applying the frame
- Imaging studies
- Treatment planning
- Gamma Knife treatment
You will visit the hospital one to two days before the Gamma Knife procedure for blood tests and to meet with the doctors who will perform the procedure. A schedule of appointments will be sent to you by mail from the UCSF Gamma Knife Radiosurgery Program. Please let us know if you have had any of the required tests performed in the past year. If so, please bring copies of the test results with you.
You will 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. We recommend that you write down your questions before your appointment to ensure you don't forget them.
The Night Before Treatment
If you live outside of the San Francisco area, please stay in a hotel or guesthouse near UCSF Medical Center. 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.
The 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.
Please arrive at the hospital at 505 Parnassus Ave. between 6 and 6:30 a.m. Go to the Outpatient Surgical Waiting Area in room M-104J. The room is located on the first floor to the right of the lobby. An escort will meet you there. The phone number for the waiting area is (415) 353-1626.
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. If you have dentures, you may wear them. Please remove eyeglasses and other personal belongings.
Applying the Frame
The stereotactic frame is placed on your head while in a sitting position. It is applied in the pre-operative area. The frame acts as a guide to find the exact location of the brain lesion. Your head will not be shaved. Your neurosurgeon will inject local anesthesia into your scalp in four places or "pin sites" where the frame will be attached. You may feel some brief discomfort during these injections and can ask for more medication to help you relax. You may feel some pressure after the head frame is attached, but this will subside. You may fall asleep after the frame is attached.
Children are given general anesthesia before the frame is attached and remain asleep during the Gamma Knife procedure. A neuro-anesthesiologist gives the anesthesia and stays with your child throughout the procedure.
Before the procedure, you will undergo imaging studies, such as magnetic resonance imaging (MRI) or computerized tomography (CT) scans or cerebral angiogram. During the studies, we ask that the family member or friend return to the outpatient surgical waiting area. He or she can return after the imaging studies are done, prior to treatment. These studies help your doctors locate the brain lesion as it relates to the stereotactic frame.
After the imaging studies are performed, you will be taken to a waiting room while your treatment is planned. A videocassette player is available in the room, if you would like to bring a video. If your pin sites cause any pain, please inform your unit nurse. He or she will call the Gamma Knife nurse, who will inject the pin sites with local anesthesia.
Treatment planning will take one to several hours depending on the size and shape of the target area. Your doctors will locate the brain lesion in three dimensions using computer software and data from your imaging studies. The position of your head in the helmet, radiation dose and length of treatment will be decided.
Gamma Knife Treatment
After the doctors plan your treatment, you will be brought to the Gamma Knife area and placed on the treatment bed, lying on your back. Your blood pressure and pulse will be monitored throughout the treatment. The stereotactic frame will be fitted into a steel helmet and fixed in position. The doctors will leave the room when treatment is ready to begin and will observe you on video camera and talk with you by intercom.
When treatment starts, you will move into a large shielded sphere. The steel helmet will interlock with another helmet inside the sphere that holds the source of radiation. Only your head will be inside the sphere. During treatment, you won't feel, see or hear anything unusual. Each "shot" of radiation will last one to several minutes. At the end of each shot, the steel helmet unlocks from the inner helmet and the bed moves out of the sphere. For most cases the automatic patient positioning system moves you to the next position. In some cases, it is necessary for the doctors to manually position you in the helmet for each shot. The entire treatment may consist of one or several shots of radiation.
The entire procedure from frame application until treatment completion usually takes most of the day.
After treatment, the stereotactic frame is removed and you will be transferred to a recovery room. You may have a headache, and not having eaten all day may add to your discomfort. Medication for the headache will be provided as needed. You will be monitored, including your blood pressure and pulse. In most cases, patients are discharged later the same day. You may resume normal activities and eat and drink as you feel able.
Children are moved to the pediatric recovery room where parents can stay with their child until ready for discharge. Most children return home at the end of the day.
Follow-up instructions will be provided before you leave the hospital. If you need more medication, you will receive a prescription. If you are given any medications on the day of treatment, you must arrange a ride home. If you have any concerns or questions after the procedure, please call the Gamma Knife nurse at (415) 353-9325.
To contact the UCSF Gamma Knife Radiosurgery Program, please call (415) 353-7500.
UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.