What is Gamma Knife Surgery?
Gamma Knife radiosurgery has been used for decades for brain tumor treatment and brain disorders without scalpels. Using this method, doctors are able to focus radiation directly, and very precisely, on the target in the brain without affecting surrounding healthy tissue. Gamma Knife surgery is an alternative or can be complementary to open surgery. Since no incision is made, and the surgery is non-invasive, the risk of surgical complications is low. The treatment is complete in one session and seldom takes more than a few hours. The full effects of Gamma Knife surgery may be realized over the course of several months following treatment. The Gamma Knife procedure is normally performed by a neurosurgeon accompanied by a radiation oncologist and medical physicist. The treatment is performed on an out-patient basis and the patient resumes normal activities almost immediately.
Studies show strong treatment success rates; for example, local control (successful treatment of a specific site) of tumors in any brain location exceeds an average of 85%. And, despite the name, there is no blade or knife – it’s called Gamma Knife because radiosurgery (one-session treatment) has such a dramatic and precise effect in the target zone that the changes are considered ‘surgical.’ So there’s no incision or blood, and minimal risk of complications.
Through the use of three-dimensional, computer-aided planning and the high degree of immobilization of the patient, the treatment can minimize the amount of radiation to surrounding healthy brain tissue. There are approximately 200 sources of cobalt-60 loaded within the treatment unit. Thousands of radiation beams can be generated from these sources with a level of accuracy of more than 0.5mm, about the thickness of a strand of hair. Individually, each radiation beam is too weak to damage the normal tissues it crosses on the way to the target. But when focused precisely on that target, the beams intersect and the combined radiation is sufficient to treat the targeted area.
Because Gamma Knife radiosurgery is so accurate, the full dose of radiation can be delivered during a single session, compared with multiple visits for traditional radiation therapy treatments, which use lower doses delivered in many fractions (hyperfractionated treatment).
Stereotactic refers to precise positioning in three-dimensional space. In Gamma Knife therapy, this means a 3-D reference frame is attached to the patient’s head during the procedure. The stereotactic head frame provides a 3-D reference which can be seen on the imaging equipment to provide exact coordinates for the target. The frame totally immobilizes the patient’s head to ensure pinpoint accuracy when targeting and delivering radiation.
The Head Frame
One of the key components of Leksell Gamma Knife – the tool that allows your doctor to precisely pinpoint your brain tumor or problem – is the special stereotactic head frame.
This lightweight frame, which is attached to your head with four small screws, ensures that the radiation beams are precisely targeted.
The frame also prevents your head from moving during the treatment procedure, which ensures that only the target area in your brain receives radiation.
Imaging
After your head frame is in place, a number of advanced imaging tests – such as an MRI or CT scan – will be required to precisely locate the size, shape and location of your brain tumor, lesion or abnormality.
If your physician is treating a blood vessel abnormality, an angiogram may also be required.
As you may already know, an angiogram involves the injection of a dye into your bloodstream so that the imaging procedure clearly shows the blood vessels and arteries in the brain.
The coordinate markers on your head frame, which are part of the images taken, will help your physician develop an exact plan for your procedure.
Treatment Planning
Once your images have been taken, you can sleep, rest or relax while your physician develops your specialized treatment plan. First, your brain images are computerized. Then, using Leksell Gamma Knife 3-D planning software, a treatment protocol is planned.
No two treatment plans are alike; every patient’s plan is specifically designed to address his or her specific medical condition.
Because Leksell Gamma Knife includes a set of unique helmets that have 201 holes for the precise delivery of radiation to your brain, your plan will consist of one or more treatments using these helmets.
The Treatment
Once the Gamma Knife treatment plan is complete, you’ll lay down on the treatment table and your head frame will be attached to the helmet for your first treatment. You’ll be awake during the procedure and able to communicate with your Leksell Gamma Knife team through a video and audio connection.
When Gamma Knife® Surgery begins, the treatment table, which is much like the one you were on for your MRI or CT scan, will move into the dome section of the unit.
The team will be monitoring your procedure at all times. There may be several treatments lasting anywhere from two to forty-five minutes during your Leksell Gamma Knife session.
Back To Your Normal Routine
Once your treatment is complete, the head frame will be removed. If you had an angiogram, you might have to lie quietly for several more hours. Some patients experience a mild headache or minor swelling where the head frame was attached, but most report no problems. Your doctor will tell you whether or not he wants you to stay overnight for observation or if you can go home immediately. Either way, you should be able to return to work or your normal routine in another day or so.
The effects of your Leksell Gamma Knife treatment will occur over time. Radiation treatments are designed to stop the growth of tumors or lesions, which means they won’t disappear immediately but over a period of weeks or months. Your physician and Leksell Gamma Knife® team will stay in contact with you to assess your progress, which will include follow-up MRI or CT images in the near future and periodic check-ups.
