What is a Gamma Knife?
The Gamma Knife is not a knife, but rather a sophisticated technology that can in some situations be used to replace neurosurgery. It uses a single, high dose of gamma radiation delivered using a lightweight head holder (frame), a helmet called a collimator, and the Gamma Knife unit itself. The Gamma Knife procedure treats brain lesions with enough radiation to destroy them even in the most critical, difficult-to-access areas of the brain without delivering significant radiation doses to healthy normal brain tissue. The Gamma Knife is faster and more precise than other radiosurgical tools that are currently available. It uses 201 separate radiation beams to target lesions that have been defined by MRI scans or angiograms. The 201 individual beams intersect at a single spot with the accuracy of less than one-tenth of a millimeter (about the thickness of a sheet of paper). Referred to as "surgery without a scalpel," the Gamma Knife procedure does not require the surgeon to make an incision in the scalp, nor an opening in the skull.
How does the Gamma Knife procedure compare to regular neurosurgery?
Gamma knife radiosurgery is an outpatient procedure that allows patients to go home in about half a day. Only a single treatment is usually needed. The Gamma Knife treatment itself takes about two hours on average. Patients can usually return to their normal routine within a day of the procedure. Almost all patients are treated on an ambulatory basis and very few require hospitalization. Much of the convalescence required for conventional surgery is avoided. In contrast, surgery generally requires shaving of the hair, general anesthesia, a short stay in the intensive care unit, several days in the hospital and weeks of convalescence time at home.
How is Gamma Knife different from radiation therapy?
Gamma Knife surgery is different from conventional radiation therapy of the brain because the radiation is directed at the target and spares the surrounding normal brain tissue and other structures. It also differs because Gamma Knife requires only a one day treatment, rather than many treatments with smaller doses of radiation over several weeks. In addition, Gamma Knife radiosurgery can be used in conjunction with conventional surgery as a treatment for tumors that cannot be totally excised. It can also be used in some cases where the tumor is inoperable.
Can Gamma Knife treatment be given more than once?
Yes, in some cases patient’s who have been treated with Gamma Knife for metastatic, or secondary, brain tumors and who subsequently develop additional tumors, can be treated again with Gamma Knife.
Is Gamma Knife treatment effective?
The Gamma Knife is not an experimental form of treatment. It is a highly effective method of brain tumor treatment and its use is supported by two decades of clinical research published in the mainstream medical literature.
What is involved in a typical Gamma Knife treatment?
On the day of treatment, the patient is given light sedation. Next, local anesthesia is used to secure an aluminum head frame to the patient’s head. The frame is used in conjunction with an imaging procedure to accurately locate the diseased area. With the frame in place, the patient undergoes an MRI or CT scan, or in the case of an arteriovenous malformation (AVM), angiography, in order to locate the lesion in the brain to be treated. With this arrangement, the treating physician can measure the position of the lesion inside the patient’s head with respect to the frame on the outside. While the patient rests, the treatment team (which consists of a neurosurgeon, radiation oncologist and physicist) uses a computer to devise a treatment plan. This takes from 30 to 90 minutes to complete, depending upon the geometry and location of the disease. When the individual treatment plan is completed, the patient is placed on the Gamma Knife couch so that the head is precisely positioned for treatment. The patient is then moved automatically, head first into the machine, and treatment begins. Treatment typically lasts from 20 minutes to 2 hours, during which time the patient feels nothing. At the completion of the treatment, the patient is automatically moved out of the machine, and the head frame is removed. The patient usually goes home at this point, but may remain in the hospital overnight for observation on occasion.
What does the patient feel during the Gamma Knife Treatment?
There is mild pain from administration of the local anesthetic used during placement of the head frame (similar to the sensation of having blood drawn). Patients have reported that they feel a pressure sensation when the frame is applied, but not pain. The pressure can be a little uncomfortable but it does not last for long. During actual treatment, the patient does not see or feel the radiation.
What can the patient expect after Gamma Knife treatment?
After the treatment session is finished, the head frame is removed. Sometimes there is a little bleeding from where the pins contact the patient’s head. Pressure is applied to stop the bleeding and Bandaids may be used to keep the pin sites clean. It is usually recommended that the patient refrain from physical activity over the next 18 to 24 hours.
How quickly will the Gamma Knife treatment work?
The effects of Gamma Knife radiosurgery occur over a period of time that can range from several weeks to several years, depending on the condition being treated. The radiation alters the DNA of tumor cells so that they can no longer reproduce. Some tumors shrink gradually and eventually disappear. Others simply grow no further. The effectiveness of the treatment is monitored by MRI scans at regular intervals. The goal of radiosurgery is tumor control, which is defined as either unchanging (stable) tumor size or tumor shrinkage.