Gamma Knife

Gamma Knife

Radiosurgery is a medical procedure that allows non-invasive treatment of benign and malignant tumors and other brain pathologies, such as trigeminal neuralgia and some cases of epilepsy. The initial application of radiosurgery was in treatment of lesions in the brain, a technique also known as stereotactic radiosurgery (SRS). The compound word stereotactic is made up from Greek words: στερεος, which means solid, and τακτική (hinted τηχνη) which means "ability in disposition," meaning "tactic" as used in military language. In fact radiosurgery is stereotactic only if the distribution of radiation beams is in three dimensions and not in two as in traditional radiotherapy. In addition to cancer, it has also been shown to be beneficial for the treatment of some non-cancerous conditions, including functional disorders such as arteriovenous malformations (AVMs) and trigeminal neuralgia.

There are many neurological disorders for which conventional surgical treatment is difficult or inadvisable due to the required displacement or cutting of surrounding tissue, which can damage nearby arteries, nerves, and other vital structures.

Radiosurgery operates by directing tightly focused beams of ionizing radiation with high precision from multiple directions at intracranial and extracranial tumors and other lesions. The beam paths converge in the target volume, delivering a lethal cumulative dose of radiation, while exposing adjacent healthy tissue to a much smaller level of radiation.

It is a relatively recent technique, first developed in 1951 by Swedish physician Lars Leksell. His radiosurgery device (the "Gammaknife") used a helmet, in which the patient's head was locked in place, and could only treat cranial disorders.

In 1982, the technique was augmented with the use of a high precision linear accelerator as radiation source, and the patient was attached to a couch that could rotate on multiple axes, for three-dimensional treatments similar to those obtained with Gammaknife.

Recent innovations in radiosurgery (Cyberknife 1994) include platforms that sense the position of the patient and adjust the radiation to patient position, to avoid the effects of patient movement and breathing. This maintains the necessary precision for irradiating a very small target. It also allows radiosurgery of extracranial lesions, enormously extending treatment possibilities.

The latest radiosurgery technology available as of 2009 included the CyberKnife and Gamma Knife Perfexion systems, the Novalis Tx radiosurgery platform, and the Trilogy linear accelerator by Varian.

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