How Gamma Knife Perfexion Works

The Gamma Knife Perfexion works by utilizing the latest advanced diagnostic imaging and three-dimensional treatment planning software to deliver 192 finely-focused beams of gamma radiation to small targets inside your brain. The beams converge at a point to treat the affected tissue, while minimizing damage to your healthy brain tissue.

After you’re referred to St. Vincent’s for Gamma Knife treatment and your case is reviewed by our multidisciplinary team, your treatment day will be scheduled. On the day of your appointment, several steps take place.

Placement of the Head Frame

A stereotactic frame will be placed on your head and remain there throughout treatment. The frame is needed as a reference point during treatment planning, and it is used to hold your head in the exact position required for precise treatment. This frame provides the Gamma Knife with an unmatched level of accuracy to perform the treatment procedure.

Obtaining Precise Images

MRI, CT scans or angiography (a way to visualize the blood vessels) will be used to obtain images that clearly define where the tumor, malformation or treatment site is located. These images are used to design a custom treatment plan for each patient.

Treatment Planning

Once the images are transferred to the Gamma Knife's computer planning system, your care team will examine them and accurately define the target. The detailed treatment plan they create will determine how long treatment will take. Typically, planning a Gamma Knife treatment takes about an hour.


Once your treatment plan has been carefully checked by the team for precision and safety and has been explained to you, treatment will begin. You’ll enter the Gamma Knife suite and recline on the couch portion of the Gamma Knife. The team will position your head in the machine. The team conducts treatment in an adjacent room, maintaining contact with you through video and intercom. You may choose to listen to the radio or music of your choice during treatment.

When the treatment is over, you’re taken out of the machine and the head frame is removed. You will likely be observed for a period of time and then released; however, it is possible you may be required to stay overnight in the hospital. Barring any unusual outcomes, you should be able to return to normal pre-treatment activities within a day or two.

Post-Gamma Knife Treatment

The effects of Gamma Knife radiosurgery occur over several weeks to several years, depending on the type of medical condition treated. The radiation alters the DNA of the tumor or lesion being treated so the cells no longer reproduce, eventually rendering the lesion static. Some abnormalities dissolve gradually, eventually disappearing. Others simply exhibit no further growth.

The effectiveness of the treatment is monitored by appropriate imaging scans at regular intervals. A physician will monitor your treatment results by taking periodic MRI, CT scans or angiography. The Gamma Knife Center staff will stay in contact with your regular physician in order to monitor your treatment progress. We are available to provide any further consultation you may need.

For more information about how Gamma Knife works, call 904-308-7411.