It seems like an idea from a science fiction story: A device that can precisely target and eliminate brain tumors without a single scalpel stroke. But that’s exactly what Gamma Knife® does, and it’s a technology that’s been around for more than three decades.

HOW IT WORKS    The Gamma Knife uses ionizing radiation (gamma rays) produced by 201 cobalt-60 sources to target and destroy a tumor, a blood vessel abnormality such as an arteriovenous malformation (AVM) within or adjacent to brain tissue, or to treat the symptoms of Parkinson’s disease and trigeminal neuralgia (an excruciatingly painful facial condition) with extreme accuracy. Since each individual gamma ray is of relatively weak intensity, the normal brain tissue surrounding the abnormality is protected as the full dose of radiation is focused only at the point where all 201 beams converge. This explains why side effects are rare and usually temporary. Since the procedure is non-invasive, or “bloodless”, the risks of post-operative complications, such as infection and hemorrhage, are eliminated.    A multidisciplinary team consisting of a neurosurgeon, a radiation oncologist, and a radiation physicist accomplishes treatment with the Gamma Knife. The referring physician is an active partner in the treatment process, and patients accepted by Gamma Knife treatment remain in their primary physician’s care. Providing regular reports on patient status, the Gamma Knife team maintains ongoing communications with referring physicians through evaluation, treatment, follow-up, and outcome studies.

   “When you think of ‘knife’ you think of cutting,” said Dr Richard G. Ellenbougen, professor and chair of Neurosurgery at the University of Washington’s Harborview Medical Center in Seattle, which has been using Gamma Knife technology since the late 1990s. But Gamma Knife is a “bloodless way to obliterate brain lesions.”
    Invented in 1968 by Swedish neurosurgeon Lars Leksell, Gamma Knife is a radiosurgery technique that is in wide use in the medical field. Using radioactive cobalt to produce gamma rays, the Gamma Knife can deliver a high dose of radiation to a very specific area of the brain, destroying target cells while leaving surrounding, healthy tissue intact.
   “Gamma rays are similar, if not identical to, high-energy X-rays,” said Dr. Ronald Young, neurosurgeon and medical director of the Gamma Knife Center at Seattle’s Northwest Hospital and Medical Center. Northwest’s Gamma Knife Center opened its doors in 1993 and was the first Gamma Knife center in the Pacific Northwest region.
   The Gamma Knife radiation is formed into beams of various sizes and then directed at the target through a stereotactic halo, or helmet, worn by the patient. These beams can be combined into different shapes, so that the resulting radiation beam can accurately target tumors of irregular shape.
   Gamma Knife is used exclusively for treating brain lesions and other diseases related to the brain, including Parkinson’s disease; brain tumors, both benign and malignant; certain kinds of tremors; arteriovenous malformation, a blood vessel malformation; and trigeminal neuralgia, a condition that can cause severe face pain.
   “The main restriction for using Gamma Knife is size,” said Dr. Young, noting that some very large tumors may not be suitable for Gamma Knife treatment. “But aside from size considerations, any tumor or vascular malformation is suitable for Gamma Knife treatment.”
   The process of getting “Gamma Knifed,” as the phraseology goes, usually takes several hours, from start to finish. First the patient will be given a local anesthetic and the stereotactic halo will be screwed to the skull. Next an MRI or CAT scan will be done and the resulting data will be loaded into Gamma Knife’s computer system and used to calculate precisely how the radiation will be delivered. Then the actual Gamma Knife treatment takes place, lasting anywhere from a few minutes to an hour or so.
   With Gamma Knife, unlike traditional surgery, “we don’t ‘remove’ anything, per se,” said Dr Young. Instead, Gamma Knife damages the DNA in the nuclei of the targeted cells, causing the cells to die over time. Instead of removing tumors, doctors refer to the “control rate,” measured by the lesion’s lack of growth, shrinkage, or disappearance.
   “With Gamma Knife we generally achieve a 90 percent control rate,” said Dr. Young.
   Follow-up visits and periodic imaging scans are required to assess Gamma Knife’s effectiveness. The vast majority of patients who receive one Gamma Knife treatment never need another one. The few who do require additional treatments, said Dr Young, usually have months or even years before it becomes necessary.
   The one-time-only nature of the procedure, as well as the use of targeted beams of radiation, instead of whole-brain radiation, are just two of the advantages of Gamma Knife. Gamma Knife can also be used to attack deep-seated lesions that are in areas of the brain where it would be risky or impossible to reach with traditional surgery.
   Patients who might have other conditions that make surgery a high-risk proposition can also benefit from Gamma Knife treatment. Patients rarely experience the side effects associated with traditional radiation therapies, such as hair loss. And Gamma Knife treatment can also be more cost-effective than traditional surgery, since prolonged hospitalization is unnecessary and the risk of complications during surgery and recovery are eliminated.
   Northwest Hospital and Harborview Medical Center — which is in the process of upgrading its Gamma Knife to the new 4C model, the first on the west coast — are the only facilities in the Puget Sound area that currently offer Gamma Knife technology, although that will soon change. St. Joseph Medical Center in Tacoma will be adding Gamma Knife to its list of services very shortly and expects to be up and running with it sometime this fall.