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How Does Gamma Knife Work?

On the morning of your treatment, you will receive a type of sedation, called light sedation, as well as local anesthesia, which allows you to remain awake during the procedure, but feel no pain.

In order to determine the exact location of your tumor or malformation, a metal halo device, called a stereotactic frame, is attached to your skull with a set of rods or pins. Although this is usually painless, you may experience a feeling of pressure that should disappear in about 15 minutes.

After the frame is attached, you are brought to the radiodiagnostic suite where a picture of your brain is made using a scanner, such as an MRI (magnetic resonance imaging) or CT (computerized tomography). The image then appears on a computer screen as a three-dimensional picture with reference points to the head frame. The picture is used by your neurosurgeon, physicist and radiation oncologist to develop your treatment plan including the appropriate radiation strength. Then, the computer is programmed to "lock-in" the determined coordinates.

Once the coordinates have been determined, you will be placed on the Gamma Knife table, known as a couch, and your head frame will be attached to a large helmet with holes in it. The helmet shields your head from unwanted radiation, allowing only the predetermined amount to get through. When your imaging frame and helmet are in place, you will lie down on the Gamma Knife couch, face up. The couch will move you into a sphere. The sphere contains 190 sources of synthetic radioactive isotope material called cobalt 60. These sources are positioned so that the narrow beams of radiation focus directly on the area of your brain that needs treatment. If necessary, beam sizes can be adjusted by using different helmets with holes of various sizes.

Treatment can be as short as 15 minutes or as long as two hours, depending on several factors, such as the number of times you must be repositioned, the strength of the cobalt sources and the dose of radiation used. Doctors and nurses monitor you from an adjoining room, using video cameras, and an intercom system. There is generally little or no discomfort associated with the procedure. Recovery time is brief, and there are no immediate side effects and virtually no post-procedure discomfort. You will most likely be treated in one session and go home the same day to return to your normal routine.

You will probably be asked to see your doctor for a checkup about a month after the procedure. Depending upon your diagnosis, you may need a follow-up MRI or CT scan after the radiosurgery.