Gamma Knife radiosurgery is a very precise form of radiation therapy that focuses intense beams of gamma rays with pinpoint accuracy to treat lesions in the brain.
Despite its name, Gamma Knife surgery involves neither traditional surgery nor an actual knife. Gamma Knife radiosurgery is called “surgery” because its outcome is similar to that of a surgical procedure.
Gamma Knife radiosurgery can be effective in treating tumors, blood vessel malformations and nerve conditions. In each instance, surgeons and radiation oncologists use the Gamma Knife system somewhat differently:
- Radiosurgery for tumor treatment works by damaging or destroying the DNA of tumor cells so that these cells cannot reproduce or grow. Over time, the brain tumor shrinks.
- For blood vessel malformations, such as an arteriovenous malformation, Gamma Knife treatment causes the malformed blood vessels gradually to close off.
- When nerves are the target for treatment, as in the case of the pain disorder trigeminal neuralgia, radiosurgery diminishes the function of improperly acting nerves, which provides relief.
Many beams of gamma radiation, each emitted from a different location outside the head, join to focus on the lesion—without a surgical incision. On its own, each beam carries a very low dose of radiation and has minimal effect on the healthy tissue through which it passes, but when they converge on the lesion, the beams combine to provide a precise, intense dose of radiation. Your medical team will program the Gamma Knife system with extreme precision to deliver the radiation necessary for your individual situation—the strength of the beams, the angles from which they arrive, the number of times they are discharged and the exact location that is their destination.
Gamma Knife radiosurgery is used to treat certain conditions of the brain, many of which could only be treated by open surgery had this option not become available. At the Gamma Knife Center, our expert neurosurgeons and radiation oncologists most often use the Leksell Gamma Knife Icon to treat the following brain conditions:
Primary brain tumors, in particular:
- Acoustic neuroma/Vestibular Schwannoma
- Pituitary tumor
- Glomus jugulare tumor
- Pediatric brain tumors
- Arteriovenous malformation
- Trigeminal neuralgia
- Essential tremor
- Obsessive-compulsive disorder
Other conditions may also respond to Gamma Knife radiosurgery. This may be the procedure of choice when a brain lesion cannot be reached by conventional surgical techniques. Gamma Knife may also be used in lieu of operations that require craniotomy for those patients who must avoid open surgery.
Because the therapeutic effects of a Gamma Knife procedure occur over time, it may not be suitable for individuals whose condition requires more immediate therapy.
Gamma Knife radiosurgery can be used to treat children and adults.
How is this procedure performed?
The treatment team typically includes a neurosurgeon, a radiation oncologist, a radiation therapist and a registered nurse. In addition, a medical physicist calculates the precise beam placement and number of exposures necessary to obtain the radiation dose that is prescribed by the radiation oncologist. (Your treatment team may include other healthcare professionals in addition to, or in place of, those listed here.)
A Gamma Knife procedure may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary slightly depending on your condition.
Before the procedure begins, you may be asked to remove any clothing, jewelry, hairpins, dentures or other objects that may interfere, and you will be given a gown to wear. An intravenous (IV) line may be started in your hand or arm in order to supply you with medications and/or fluids.
Next, the head is prepared for placement of a box-shaped head frame or custom-made face mask. No shaving is required for either method. Which method is used depends on the individual condition and diagnosis of the patient. Frames confer maximum precision, necessary for working with trigeminal neuralgia, essential tremor, epilepsy and obsessive-compulsive disorder. Face masks, which may be more comfortable, also ensure an extremely high degree of accuracy. The frameless face mask also enables treatment of larger tumors over a series of days usually on an outpatient basis. The frequency and amount of treatments required will be determined by the Gamma Knife team.
If a head frame is used the head frame is attached to the head and will prevent the head from moving during the procedure. This technique is also called frame-based radiosurgery.
If a face mask is used, a thermoplastic mask will be placed and then molded over your face for a customized fit. The mask has an opening for your nose and you will be able to breathe comfortably while wearing it. The mask is then contoured to fit your face perfectly and will have a snug, tight fit, minimizing head movement during the procedure. It will take about 10 minutes or less for the mask to harden, forming a custom face mask. Although tight, the face mask is comfortable to wear throughout the procedure. This technique is also called frameless radiosurgery.
You may receive a mild sedative to help you relax prior to a frame or frameless procedure.
After the head frame or face mask is attached, you will undergo brain imaging so that the location of the brain lesion can be precisely identified. The brain imaging procedure may be a computed tomography (CT) scan, a magnetic resonance imaging (MRI) scan or a cerebral angiogram.
After the brain imaging has been completed, you will be allowed to rest and relax while the treatment team completes your treatment plan. Determining your treatment plan can take between 30 and 90 minutes. To make your treatment plan, the team will combine the results of the imaging scan with other information to determine optimal dosage and number of exposures. The team will input specific instructions to the computer system on where to focus the gamma rays, ensuring pinpoint precision and accuracy.
During the entire treatment, you will be monitored by the Gamma Knife team via live videofeed. You will have an intercom available to communicate with the team. They will be able to hear and communicate with you at all times.
The Icon machine is silent and you will not feel or hear anything during the procedure. The team will continuously monitor your head placement and radiation dosage. The head frame or face mask will keep your head in alignment.
The number of treatment sessions will depend on your specific diagnosis. You may be inside the Gamma Knife unit as briefly as 15 minutes, or up to a few hours; the duration will depend on the treatment plan designed for you.
After the treatment session is over, the treatment table will slide out of the Gamma Knife machine.
The head frame or face mask will be removed. You will then be briefly monitored by the nursing team prior to discharge.