Stereotactic radiosurgery is the very precise delivery of radiation to a brain tumor with sparing of the surrounding normal brain. To achieve this precision, special procedures for localization are necessary. These 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. Conventional radiotherapy is a very useful treatment modality for many brain tumors. The reason for fractionation is to improve 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 radiosurgery, as is discussed below. This means that the location of the frame is known, and, via the CT or MRI scans both 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.