Radiocirurgia

Radiosurgery of Intracranial Lesions by John S. Yu, Anne Luptrawan, Robert E. Wallace, and Behrooz Hakimian

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Radiosurgery of Intracranial Lesions

In 1951 Swedish neurosurgeon Lars Leksell coined the term radiosurgery to denote a noninvasive technique that precisely delivers a single high dose of radiation to a targeted area of brain through an intact skull. The desired biological effect of radiosurgery is the destruction of a targeted area in the brain while avoiding nearby normal tissue and critical structures. Leksell, along with biophysicist Dr. Borje Larsson, introduced the first gamma knife in Europe in 1968. Radiosurgery can be performed using two devices: gamma knife and linear accelerator. Photon and proton beam radiation are two forms of radiation sources used to perform stereotactic radiosurgery.

N Modified Linear Accelerator
Radiosurgery
The linear accelerator (linac) is another radiosurgery tool used to effectively treat brain lesions. Unlike a natural emission of gamma ray photons produced by the gamma knife cobalt-60 sources, photons are created via the linac by accelerating electrons along a linear path and colliding with a metal target. The single stream of photon radiation simulates multiple stationary beams by using multiple noncoplanar arcs around the patient’s head while the patient rotates on a turntable (couch) in each of four positions. Multiple beams of radiation can also be shaped with multileaved collimators to treat complex-shaped lesions. Linac radiosurgery delivers very precise and uniform irradiation, but unlike the gamma knife, it allows for fractionation of treatment. Fractionation of treatment divides treatments into multiple sessions using smaller doses, or fractions, of radiation. This treatment strategy is referred to as stereotactic radiotherapy. Fractionation allows for treatment of larger lesions and lesions that are intrinsically part of a critical structure while minimizing effects on surrounding normal