Frequently Asked Questions

What is a Gamma Knife?

The Gamma Knife is not a knife, but a highly sophisticated technology that can be used to replace some conventional neurosurgical procedures.

The body of the Gamma Knife is a shielded container in which 201 sources of Cobalt 60 that are constantly emitting narrow beams of gamma radiation. These individual beams converge at a central point that is fixed (fixed isocenter). The patient wears a lightweight head holder (frame) similar to a 'halo' often associated with head immobilization seen in neck injuries. The frame is placed on the patient's head using local anesthetic. At the beginning of a treatment session, the patient lies on a sliding couch and the head frame is attached to a collimator helmet which adds additional focus to the beams of radiation. Computer-driven motors on the helmet position the patient's head so that the target for treatment will lie at the focus of the beams of radiation. The actual treatment occurs when the shielding doors of the Gamma Knife have opened and the couch moves toward the Gamma Knife so that the collimator helmet docks with the radiation source in the Gamma Knife unit. At this point the beams of radiation are aligned with the openings in the collimator helmet so that radiation can pass. The dose of radiation is determined by the time spent in the docked position and by the size of the openings in the collimator helmet. During a treatment session, several different locations in a lesion can be targeted; the couch will move out of the treating position, cutting off delivery of radiation, the computer-driven motors will adjust the head position, and then the couch will move back into the treating position, as many times as are necessary to complete the planned treatment.

By holding the head immobile and delivering radiation via immobile sources, the Gamma Knife avoids errors which may be introduced by other radiation delivery devices which use a mobile radiation source. This allows precise targeting (within a few tenths of a millimeter).

The Gamma Knife is faster and more precise than other radiosurgical tools that are currently available. The Gamma Knife procedure can treat brain lesions with enough radiation to destroy them even in the most critical, difficult-to-access areas of the brain and yet spare healthy normal brain tissue. 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.

What can be treated?

The Gamma Knife is a dedicated radiation device exclusively for intracranial tumors and malformations.

Brain Tumors
The Gamma Knife is very effective in the treatment of brain tumors whether the tumor is a primary tumor (glioma, astrocytoma, meningioma) or secondary tumor (brain metastases - tumors that have their origin from cancer from elsewhere in the body).

Arteriovenous Malformations (AVMs)
When veins and arteries connect directly rather than through capillaries, the result is a tangle of thin-walled vessels susceptible to rupture, which can cause neurologic deficit, headaches, seizures, or even death. While the most definitive way to eliminate these malformations is by surgical removal, sometimes that is not possible or a patient may opt for a less invasive method of control. The radiation from the Gamma Knife causes the lining of the blood vessel at the target to thicken over time, creating a blockage that, over time, will reduce the chance of rupture.

Trigeminal Neuralgia
Gamma Knife treatment is an appropriate consideration when medication has failed to relieve the terrible sharp facial pain which is characteristic of this condition. Although surgical intervention is effective for these patients, operation on the trigeminal nerve at its origin from the brainstem is a quite major surgical procedure. Gamma Knife treatment works by creating a disturbance of conduction within the nerve, thereby blocking the transmission of this pain.

Acoustic Neuromas (vestibular schwannomas)
Dr. Neil Giddings, neuro-otologist, is a surgeon who has surgically removed hundreds of acoustic neuromas (benign tumors that develop on the nerve that effect hearing and balance). Dr. Giddings now uses the Gamma Knife extensively for treating these tumors because of its lower risk of deafness and facial paralysis.

Pituitary Tumors
These tumors are often associated with thyroid, adrenal and reproductive gland problems as the pituitary controls all their functions. Gamma Knife surgery is very effective in treating these difficult-to-access tumors.

Cancer Pain
By targeting the pituitary with the Gamma Knife, our team can perform a radiosurgical hypophysectomy which, in the case of intractable cancer pain, can result in marked improvement of the pain and less need for narcotic and psychoactive medication.

Tremors
Deep brain stimulation research has identified an area of the brain (close to the VIM nucleus) through which electrical signals are transmitted that cause the hands of a patient to tremble or move uncontrollably. This target can be treated with a 4mm 'shot' of radiation from the Gamma Knife that will disrupt the transmission of this unwanted signal. Whether it is an essential tremor, Parkinsonian tremor or one associated with multiple sclerosis, the Gamma Knife has been effective in reducing the tremor or eliminating it altogether.

If you have been diagnosed with either essential tremor or Parkinsonian tremor, there is research and our own experience that indicates you may benefit from gamma knife treatment. Working closely with Dr. David Greeley, our center has seen results similar to the findings of the aforementioned research. For additional information, contact Dr. Greeley directly and ask him about your suitability for gamma knife intervention.

How is the Gamma Knife different from radiation therapy?

In a sentence, Gamma Knife is more accurate and takes less time to deliver than traditional radiation therapy.

Traditional radiation therapy often breaks up (fractionates) delivery of radiation. This is done because cancer cells differ from healthy cells, recovering more slowly from radiation exposure and, due to differing mitotic (cell division and growth cycles) activity, are susceptible to cellular destruction. Fractions of the 'killing dose' are delivered to the target and while the healthy tissue recovers more quickly than cancer tissue, the diseased tissue then is ultimately destroyed. Fractions are often delivered with daily doses on weekdays over a period of 1 to 8 weeks, depending on the disease.

Gamma Knife surgery is different from conventional radiation therapy of the brain because the radiation is precisely directed at the target and spares the surrounding normal brain tissue and other structures. Because of this, the 'killing dose' can be delivered to just the targeted tumor in one session. It is an 'overwhelming' dose that destroys the tumor.

Gamma Knife radiosurgery can be used in conjunction with whole brain radiation therapy with excellent results. In addition, it can also be used with conventional surgery as a treatment for tumors that cannot be totally excised or, in some cases, where the tumor is inoperable.

Single versus multiple visits
Gamma Knife radiosurgery (single dose treatment) is different than traditional Linear Accelerator (LINAC) based radiation in that it is a single dose - one time, one day, and you're done, versus multiple treatments (fractionated). Because the Gamma Knife has 201 sources of radiation, healthy tissue gets only 1/200th of the dose delivered to the target. For that reason, the Gamma Knife can be used in a single-dose delivery, eliminating the need to fractionate (break up the total dose into smaller doses in order to preserve healthy brain tissue).

More accurate
Because the Gamma Knife has a fixed isocenter and fixates the skull for delivery, its accuracy (and resulting minimal dosing to healthy tissue) is superior to that of the LINAC.

Ease of treatment for you and the treating physicians
In addition, LINACs, used for stereotactic radiosurgery, usually take longer to treat than does the Gamma Knife (especially for multiple tumors). Bottom line? You wait less time with the Gamma Knife.

Do you use LINAC radiosurgery along with Gamma Knife?

We have extensive experience with both technologies and we no longer use the LINAC for intracranial radiosurgery.

How is this different from the CyberKnife?

The Gamma Knife has been in operation for over 40 years and has been used to treat over 350,000 patients. It is considered the 'gold standard' for intracranial tumor control. Because the Gamma Knife secures the skull with a lightweight frame and the radiation source is fixed (unmoving), its accuracy is within .3mm. The CyberKnife doesn't fix the patient's head and has moving delivery systems that do not offer the same level of accuracy as the Gamma Knife. This accuracy is significant when it comes to sparing healthy brain tissue during these very delicate procedures. The CyberKnife delivers between 2 to 6 times the radiation dose to healthy tissue than does the Gamma Knife.

Who is an appropriate candidate for Gamma Knife?

Our treatment team reviews many factors to determine whether Gamma Knife is the best approach. In many cases, our team evaluates the patient's medical history, existing films and laboratory tests before seeing the patient in order to determine whether a physical consultation is necessary.  For more information, click here.

Consultations include spending time with either Dr. John Demakas or Dr. Alex MacKay, or for acoustic neuromas, Dr. Neil Giddings. In addition, Dr. Robert Fairbanks, our chief radiation oncologist, or Dr. Lamoreaux will evaluate your entire radiation history and prescribe the appropriate dose for your condition.

How does the Gamma Knife procedure compare to neurosurgery for a brain tumor?

Because Gamma Knife radiosurgery requires no incisions and no general anesthesia, the risks of complications, infection or other side effects are greatly reduced if not eliminated altogether. As an outpatient procedure for trigeminal neuralgia, the patient can in most cases, return home by dinner the same day of surgery and resume normal activity. For many tumors and tremors, the actual procedure takes less than 3-4 hours from the time the head frame is affixed to 'frame off'. The patient usually stays overnight in the hospital for monitoring and observation. It is this factor - the single-day treatment with minor complications - that separates a Gamma Knife procedure from traditional neurosurgery. Patients 'get on with living' much more quickly after a Gamma Knife procedure than they would if they underwent a surgical procedure.

What's my typical day look like with the Gamma Knife treatment?

Day of Treatment

1. Patient arrives and is given mild sedation.
2. Local anesthesia is applied to the head where the frame will be affixed.
3. A Plexiglas box (for targeting) is affixed to the frame and the patient goes to MRI, CT or Angiography to get scanned.
4. Patient rests while the neurosurgeon, radiation oncologist, neuro-otologist and the medical physicist use the state-of-the-art computer to plot and target the radiation (called a treatment plan).
5. Once the team approves the plan, the patient is taken into the Gamma Knife vault and lies down on the table.
6. The physicians place the head frame into the Automatic Positioning System apparatus and the machine is checked and calibrated for the treatment.
7. Upon treatment, the patient's table and affixed head frame/helmet all move as one into the machine so that just the head and shoulders enter the apparatus.
8. Depending on the extent of the disease and location of the targets, treatments can range from between 20 minutes and 4 hours during which the patient feels nothing.
9. Patients bring their own CD's and can listen to the music and talk to their loved ones via intercom during the entire treatment.
10. Upon completion of the treatment, the patient is moved out of the machine and back to the holding room where the head frame is removed.
11. Patient then has a light meal and is either released to go home or may be admitted overnight into the hospital for observation.

What does the patient feel during the Gamma Knife Treatment?

The patient may feel a stinging sensation when the surgeon administers the local anesthetic to the pin sites. They also may feel a temporary pressure when the head frame is affixed. While being treated, the patient does not feel any of the treatment procedure.

What can the patient expect after Gamma Knife treatment?

After treatment, the head frame is taken off and the pin sites are bandaged and the whole head is snugly wrapped, applying slight pressure to prevent bleeding from those sites. After a few hours, bandaids are applied to the pin sites.

How quickly will the Gamma Knife treatment work?

The effects of the Gamma Knife depend on the type of target - for most metastatic tumors, they respond within a few weeks or months. Some tumors that are slow growing, may take longer to respond. The overall goal of Gamma Knife radiosurgery is tumor control by using radiation to halt tumor growth by altering the DNA structure of the cancer cells, preventing these cells from reproducing. So consequently, the faster growing the tumor is, the more rapidly this tumor will respond to Gamma Knife; brain metastases shrinking faster than meningiomas or acoustic neuromas.

How will I know that this procedure worked?

Drs. Demakas, MacKay or Giddings will follow up with you and do a repeat MRI within a month (sooner for some, later for others depending on the tumor/size/type).

I know I can't get whole brain radiation more than once. How about Gamma Knife - can I get multiple treatments?

Yes. In some cases, patients who have been treated and develop new tumors can come in for additional procedures. Because of the accuracy of the Gamma Knife, healthy tissue is not as compromised as it would be with conventional radiation therapy. In the case of trigeminal neuralgia, excellent results have been seen when the patient has follow-up procedures.

What do I take with me after the procedure?

Upon the day of treatment, you, your referring physician and radiation oncologist will receive a photo of your treatment plan and a letter from the treatment team. With that photo may be a copy of the screen shot of your MRI.