What is Gamma Knife®?


Gamma Knife is an alternative to traditional brain surgery and whole brain radiation therapy for the treatment of complex, difficult brain conditions. Leading centers around the world choose Gamma Knife for its accuracy and documented outcomes.

Gamma Knife Perfexion

Gamma Knife radiosurgery is a highly effective, non-surgical outpatient treatment that replaces scalpels with radiation beams, targeted to a specific area, literally killing the offending tissue. Patients are in and out of the hospital in a day's time – and back to their normal routines immediately – with no incision.


Designed specifically for the brain, Gamma Knife radiosurgery replaces the surgeon’s scalpel with multiple narrow beams of radiation targeted to a specific area. Contrary to its name, there is no knife. No incisions are involved in this proven procedure. Patients are typically in and out of the hospital in a day’s time and back to their normal routines.
Gamma Knife is a non-invasive stereotactic radiosurgery instrument that involves no scalpel or incision – it is not a knife at all. Instead, Gamma Knife uses up to 201 precisely focused beams of radiation to control malignant and nonmalignant tumors, as well as vascular and functional disorders in the brain, without harming surrounding healthy tissue.

Patients are typically in and out of the hospital in a day’s time – and back to their normal routines soon after treatment. Gamma Knife radiosurgery may be used in place of, or in addition to, traditional surgery or whole brain radiation, depending on a patient’s diagnosis.



Unlike linear accelerator (LINAC) systems, which treat targets in the brain as well as other parts of the body, Gamma Knife is a "dedicated system" designed exclusively and optimized to treat targets in the head.



Gamma Knife does not require general anesthesia, nor does it involve the risks associated with open surgery, such as hemorrhage, infection, cerebral spinal fluid leaks or other surgical morbidities.



Hallmarks of Gamma Knife radiosurgery treatment includes precise target definition, exquisite conformity of the dose to the target while sparing normal brain and sub-millimeter accuracy of treatment delivery. Gamma Knife’s unique design enables the treatment of challenging brain tumors, trigeminal neuralgia, vestibular schwannoma, acoustic neuromas, vascular malformations, essential tremor and many other conditions.



Because the radiation delivered with Gamma Knife is highly focused, with limited exposure of radiation to normal brain tissue, published reports describe fewer side effects compared to conventional radiation therapy. Additional studies have documented that Gamma Knife delivers 2-3 times lower dose to normal structures compared to other radiosurgery devices.

Gamma Knife has the most established clinical track record and largest clinical evidence base of any radiosurgery system.

Published studies indicate Gamma Knife delivers less dose to normal brain than other radiosurgery systems and less complications compared to whole brain radiation therapy or open surgery

The number of peer-reviewed, published scientific articles documenting patient outcomes with Gamma Knife far exceeds that for any other form of stereotactic radiosurgery. Gamma Knife centers have published more than 2,800 papers and have treated more than 1 million patients worldwide during the last 40 years.

Studies include only those reporting on 30 patients or more.

Source: Elekta Database with information from PubMed;
through March 2015.

  • Convenient for Patients and Caregivers
    Most Treatments are delivered in a single session, allowing patients to return home the same day.
  • Multi-Beam Technology
    up to 201 beams of low-level radiation converge on the target with precision and accuracy.
  • Calm and Tranquil
    With a relaxing couch and music, many patients drift asleep and wake up wondering when the treatment will begin.
  • Constant Communication
    The patient and clinical team can communicate at any time during a Gamma Knife procedure.


Multiple beams deliver the exact prescribed dose to the
target area while sparing surrounding healthy tissue.


"What makes Gamma Knife so unique is that up to 201 simultaneously converging beams of radiation formed by the Perfexion can be shaped and moved to best conform to the target,” says Alex MacKay, M.D., Gamma Knife of Spokane Medical Director and full-time neurosurgeon. “Combine that capability with Gamma Knife head fixation process, and one can achieve unsurpassed accuracy other radiosurgery systems cannot deliver."


With Gamma Knife, the source of radiation and target are in a fixed relationship during radiation delivery, ensuring a high degree of accuracy.

Leading hospitals throughout the world choose
Gamma Knife for brain radiosurgery. 

Gamma Knife
Treatment Options

Most people will never have to face the need for brain surgery or whole brain radiation therapy, but for those who do, it's reassuring to know that there is a non-invasive, high-precision treatment. Gamma Knife can be used in place of, or in addition to, traditional surgery or whole brain radiation

Gamma Knife Alone
Because of its accuracy and clinical effectiveness, Gamma Knife is a preferred treatment for patients seeking a less invasive option. In an increasing number of cases, Gamma Knife is used as an alternative to surgery or whole brain radiation.
With Traditional Surgery
Gamma Knife may follow traditional surgery or whole brain radiation to further treat any residual tumor remaining after surgery or in the event of a recurrence after other therapies. In addition, Gamma Knife has become a well- documented secondary treatment option used in conjunction with chemotherapy and other radiation. Unlike whole brain radiation therapy, Gamma Knife treatments can be repeated if necessary.

Commonly Asked Questions


Gamma Knife is not a knife, but rather a sophisticated system that can be used to replace brain surgery or whole brain radiation in some situations. It uses a single, high dose of gamma radiation delivered via up to 201 individual beams which intersect at a single spot with the accuracy of less than one-tenth of a millimeter (about the thickness of a sheet of paper).

A Gamma Knife procedure can be used to treat targets even in the most critical, difficult-to-access areas of the brain without delivering significant radiation doses to healthy normal brain tissue. Referred to as "surgery without a scalpel," the Gamma Knife procedure does not require the surgeon to open the skull.

Gamma Knife can be used to treat an array of neurological disorders including brain metastases, arteriovenous malformations, facial nerve pain (trigeminal neuralgia), meningiomas, acoustic neuromas, recurrent gliomas and post-surgical pituitary tumors and essential tremor refactory to medication.

Contact your health professional to find out if Gamma Knife radiosurgery is the right choice for you.

On the day of treatment, the patient may be given light sedation. Next, local anesthesia is used to secure a head frame to the patient’s head. The frame is used in conjunction with an imaging procedure to accurately locate the target. 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. Using the imaging procedure, the treating team can define the position of the lesion(s) inside the patient’s head/. While the patient rests, the treatment team (which typically consists of a neurosurgeon, radiation oncologist and physicist) create a treatment plan. This takes from 30 to 90 minutes to complete, depending upon the geometry and location of the target(s). When the individual treatment plan is completed, the patient lies on the Gamma Knife couch so that their head is precisely positioned for treatment. The patient is then moved automatically, into the machine, and treatment begins. Treatment typically lasts from 20 minutes to 2 hours, during which time the patient feels and hears 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.

Gamma Knife is typically completed in a single-day with patients arriving in the morning and able to return home later in the day. Occasionally, physicians may choose to deliver the treatment over a few days.

The Gamma Knife is not an experimental form of treatment. It is a highly effective method of treating brain tumors and neurological and functional disorders and its use is supported by two decades of clinical research published in the mainstream medical literature.

Developed in 1968, it has been used in the treatment of over 1 million patients. There are over 2,800 peer reviewed publications describing the use of the Gamma Knife in an array of clinical conditions including brain tumors, vascular malformations, movement disorders and facial pain.

The results reported by Gamma Knife centers are typically as good as achievable with other techniques, frequently with lower complication rates.

The number of peer-reviewed, published scientific articles documenting patient outcomes with Gamma Knife far outweighs any other form of stereotactic radiosurgery. Gamma Knife centers have published more than 2,800 papers and have treated more than 1 million patients worldwide during the last 40 years. The fact that 74% of all published radiosurgery literature including most of the multicenter radiosurgery studies is based on the use of the Gamma Knife is especially significant given that both Gamma Knife and Linac-based radiosurgery systems were introduced in the same era.
Gamma Knife used in over 70,000 patients every year.
There might be 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.
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 a bandage 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.
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.

Gamma Knife radiosurgery is different from conventional radiation therapy of the brain. Gamma Knife delivers the entire course of radiation in one session, while patients undergoing radiation therapy will receive their radiation over the course of two weeks or in some cases more.

Gamma Knife is designed specifically to use radiation in place of a surgeon’s scalpel—limiting dose to the target to effect a clinical result, but sparing the surrounding tissue from any meaningful dose of radiation.

While single session radiosurgery can be done with linac based systems, due to technical limitations, linac systems will often require that the treatment be delivered over a limited number of sessions (3-5). Gamma Knife can almost always accomplish the goals of treatment in a single session.

While the Gamma Knife uses a head frame which is attached to the skull to ensure a high degree of immobilization and accuracy, linac systems frequently use mask based fixation. Patients are required to come to the hospital for mask fabrication. Actual treatment may occur a week later. All the steps of a Gamma Knife procedure occur sequentially virtually always in a single day.

Published results indicate that Gamma Knife delivers less dose to normal tissue when compared to linac radiosurgery systems.

The Gamma Knife clinical evidence base is superior to that of linac radiosurgery systems. There are far more publications documenting the results of Gamma Knife than linac radiosurgery. The disparity between the number of publications is especially striking for treatments demanding strict technical accuracy such as in the case of trigeminal neuralgia, pituitary tumors or vestibular schwannomas.

Gamma Knife radiosurgery is an outpatient procedure that usually allows patients to go home the same 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, several days in the hospital and weeks of convalescence time at home.



Christopher Loiselle, M.D.
Radiation Oncologist

Swedish Medical
Radiosurgery Center


> Download questions to discuss
with your doctor.

What conditions can be treated with Gamma Knife?
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Is Gamma Knife right for me?
What are potential side effects and recovery with different options?
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What if a condition reoccurs?
Disclaimer: This information is not intended as a substitute for professional medical advice and does not provide advice on treatments or conditions for individual patients. All health and treatment decisions must be made in consultation with your physician(s), utilizing your specific medical information. The links set out on this website are provided for your convenience only.

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