Stereotactic radiosurgery

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Stereotactic radiosurgery is a form of radiation therapy that focuses high-powered x-rays onto a small area. Despite its name, it is not considered a surgical procedure.

Gamma knife; Cyberknife

Stereotactic radiosurgery is a focused form of radiation therapy. Conventional radiation therapy directs radiation to the tumor and nearby tissue. Stereotactic radiosurgery more precisely focuses radiation onto the abnormal area. It is often used to slow down the growth of small, deep brain tumors that are hard to remove during surgery. Such therapy may also be used in patients who are unable to have surgery, such as the elderly or those who are very sick. Radiosurgery may also be used after surgery to treat any remaining abnormal tissue.

Before the actual treatment, you will have MRI or CT scans taken. Using these images, a computer creates a 3-D map of the tumor area. This planning process helps your neurosurgeon and radiation oncologist to determine the specific treatment area.

During treatment, you will lay down on a table, which slides into a machine that delivers radiation beams. The machine may rotate around you while it works.

For certain procedures, a head frame may be attached to your skull to keep you very, very still during therapy, or a plastic face mask may be used. However, improved methods that reduce the need for head frames have been developed. Because of this, tumors outside the brain, such as lung cancer, can now be treated with stereotactic radiosurgery, as long as special measures are taken to account for breathing movements.

Treatment times depend on the size and number of abnormal areas, but typically range from 15 minutes to an hour. If a single session of therapy is given, it is called stereotactic radiosurgery. If more than one session is required, the treatment is called stereotactic radiotherapy.

Three different machines are used to perform stereotactic radiosurgery:

1. The Gamma knife unit is the first device that was developed for radiosurgery.
2. Modified linear accelerators are custom-made versions of the machines used to perform conventional radiation therapy. One example is the Cyberknife. Some linear accelerators (lineacs) do not require a frame during stereotactic radiosurgery.
3. Cyclotrons are expensive. Few are in use in the United States.