How does Gamma Knife Radiosurgery Work?

Radiosurgery works in the same manner as other types of therapeutic radiology: it distorts or destroys the DNA of tumor cells, causing them to be unable to reproduce and grow. The tumor will shrink in size over time. For blood vessel lesions such as an arteriovenous malformation (AVM), the blood vessels eventually close off after treatment.

Gamma Knife treatment generally involves these steps: 

• Head Frame Placement
  In order to keep the head from moving during treatment, a box-shaped frame is attached to the head. Pins designed specifically for this purpose fasten the head frame to the skull. The head frame also is a guide to focus the gamma ray beams to the exact location of the lesion being treated.
• Tumor or Lesion location Imaging
  Once the head frame is in place, the exact location of the lesion to be treated will be determined using computed tomography (CT scan) or magnetic resonance imaging (MRI).
• Radiation Dose Planning
  After the CT or MRI scan has been completed, the radiation therapy team will determine the treatment plan. The results of the imaging scan, along with other information, will be used by a medical physicist to determine the best treatment.
• Radiation Treatment
  After being positioned for the treatment, a type of helmet with many hundreds of holes in it is placed over the head frame. These holes help to focus the radiation beams on the target. Treatment will last a few minutes up to a few hours, depending on the type and location of the area being treated. Generally, only one treatment session is required for a lesion.

A Gamma Knife procedure involves a treatment team approach. The treatment team generally includes a radiation oncologist (a physician specializing in radiation treatment for cancer), a neurosurgeon and/or a neuroradiologist, a radiation therapist, and a registered nurse. In addition, a medical physicist and a dosimetrist work together to calculate the precise number of exposures and beam placement necessary to obtain the radiation dose that is prescribed by the radiation oncologist. Your treatment team may include other healthcare professionals in addition to or in place of those listed here.

The Gamma Knife system is one of three types of radiosurgery systems. Gamma Knife systems are cobalt ⁶⁰ systems, which means they use cobalt as a source for gamma rays. During Gamma Knife treatment, the equipment remains stationary (does not move).

Two other types of radiosurgery are: 

• Linear accelerator (LINAC) systems
  Linear accelerator (LINAC) systems use high-energy x-rays to treat a tumor or other lesion. Some common types of LINAC systems include CyberKnife®, X-Knife®, Novalis®, and Peacock®.
  
  In addition to using x-rays rather than gamma rays, LINAC systems also differ from the Gamma Knife in that the machinery moves around the patient during treatment. For this reason, LINAC systems are able to treat larger tumors and larger affected areas than the Gamma Knife. Areas other than the brain can be treated with a LINAC system.
• Proton beam therapy or cyclotron
  Proton beam therapy is a type of particle beam radiation therapy. Rather than using rays of radiation, such as gamma rays or x-rays, particle beam therapy uses particles such as protons or neutrons. Proton beam therapy is the most widely-used type of particle beam therapy.
  
  Proton beam therapy may be used for radiosurgery procedures or for fractionated radiotherapy (several smaller doses of radiation over a certain period of time).
  
  There are only a few facilities in North America that provide proton beam therapy.