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What Is Stereotactic Radiosurgery?

When a patient is diagnosed with a brain tumor, surgeons evaluate the size and location of the tumor before developing a treatment plan. Because the brain is the most delicate and sophisticated organ of the body, surgery to remove a tumor is often an unacceptable option because so much healthy brain tissue is at risk during surgery. In such cases where surgery is not an option, surgeons treat tumors with chemotherapy or radiation or a combination of the two. However, some drugs are not suitable for the treatment of brain tumors because they cannot pass the blood-brain barrier.

Screenshot of Novalis treatment.
Separate beams of radiation attack the tumor from various angles to spare healthy tissue in the brain.

Radiation therapy is used to kill the tumor cells and to shrink or destroy the tumor. The beam of radiation changes the DNA in cells, which prevents them from reproducing and ideally kills the tumor. To keep from destroying healthy brain tissue, small beams of radiation pass through the tumor area from several points outside the brain. It’s not a single strong beam, but many weak beams overlapping and delivering a lethal dose to the tumor area, or isocenter.

In the past, radiation therapy was not as precise as Novalis because some healthy tissue inevitably was damaged. Novalis uses an innovative approach to mirror the exact dimensions of the tumor by using a beam shaping device called a collimator that moves a full 360 degrees around the head.

By using a complicated series of equations, the exact dimensions of the tumor can be computed and the collimator programmed to deliver a beam of radiation that mirrors those dimensions. As the beam moves around the head, the leaves of the collimator move in and out in correlation to the tumor.