Stereotactic Radiosurgery can be used to treat vascular lesions, such as arteriovenous malformations; brain tumors such as a meningioma, an acoustic neuroma, a chordoma, a pituitary adenoma or a craniopharyngioma; pineal region tumors such as a germinoma, a pinealocytoma  a pinealoblastoma, a glioma, a yolk sac tumor or a malignant teratoma; and recurrent gliomas.

For this type of radiosurgery, a noninvasive relocatable system is developed for precise localization of the tumor during radiosurgery. This system is easily tolerated because it requires no "pin" placement as with conventional frames. For tumor treatment, the relocatable frame allows fractionation of treatment, permitting a more effective total radiation dose with reduced risk of toxicity.

Stereotactic radiosurgery is the very precise delivery of radiation to a brain tumor with sparing of the surrounding normal brain. To achieve precision, special procedures for localization are necessary. Tools include the stereotactic frame, the CT or MRI scanner, a computerized system for calculating the radiation dose, and a precise system for delivering the radiation.

Stereotactic radiosurgery is a one-day outpatient treatment that does not require opening the skin or skull.

Conventional radiotherapy is a very useful mode of treatment for many brain tumors. This modality is characterized by:

1. Large volumes of irradiation (sometimes including a large volume of normal brain), and
2. Fractionation, where treatment is divided into multiple smaller doses (fractions) of radiation. The reason for fractionation is to maximize the radiation effect on the tumor while minimizing the effect on the normal brain. Normal brain tolerates small daily doses of radiation relatively well. The tumor does not tolerate the small daily doses, resulting in control of the tumor. By exploiting this difference in response, the fractionated treatment can be very effective in reducing or even eliminating the tumor while sparing the normal brain. This concept of fractionation is also very important for stereotactic radiosurgery, as is discussed below.

For stereotactic radiosurgery, the stereotactic frame provides an external frame of reference for the subsequent radiation treatment planning. The location of the frame is known, and via the CT or MRI scans, the frame and the brain tumor can be simultaneously visualized and precisely localized for the subsequent treatment planning on the computer.

Once the CT or MRI scans showing the tumor and the frame are acquired, the images are transferred to a computer workstation. There, the tumor is outlined, and the treatment planning begins.

The radiosurgeon has several variables that must be carefully integrated for a successful plan. The dose to the tumor should be as uniform as possible with a very low dose to the surrounding normal brain. The radiosurgeon selects the position within the tumor that will be the center of the arc of rotation of the linear accelerator. This is the isocenter. For each isocenter, the diameter of the beam that best conforms to the tumor can be selected. Metal tubes (called "collimators") of different diameters, usually from about 13 mm to 34 mm in size, shape the beam. The collimators can be combined to yield very precise coverage of the tumor.

The dose plan is developed on the computer, checked by a physicist, and tested on the accelerator using a phantom to confirm the correct dose.