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.