STEREOTAXICALLY GUIDED RADIOSURGERY USING THE LINEAR-ACCELERATOR

Leksell initiated the concept of stereotactic radiosurgery in 1951. This last decade has seen a rapid proliferation in the development of the methodology which is certainly related in part to the simultaneous growth of high-resolution neuro-imaging techniques. By focusing the beams of 201 hemispherically arrayed cobalt 60 sources, the gamma-knife delivers a high dose of radiation to a small target. Another possibility proposed by several authors is the bragg peak cyclotron-generated irradiation with accelerated protons or helium ions. In Lille, since 1988, we have choosen to develop stereotactic radiosurgery, according to the system of Betti, by the association of Talairach's stereotactic methodology and external single-dose encephalic irradiation with high energy X-rays, delivered by means of a linear accelerator. The major indication for the use of this method is an arteriovenous malformation. Stereotactic radiosurgery may be proposed alone or in combination with surgery and embolisation. It has been shown to be a potentially effective treatment and an attractive alternative in carefully selected patients with intracranial tumours: slow-growing, well limited, deep-seated tumours, such as some gliomas, acoustic neurinomas, skull base meningiomas, pituitary adenomas. This treatment is also used to deliver a focal boost of radiation to previously administered fractionated radiotherapy in patients with small gliomas and solitary brain metastases.