[Stereotactic brain radiosurgery in the treatment of skull base tumors.].

Stereotactic radiosurgery has shown effectiveness in the multimodal treatment of skull base tumors, however it is suggested that in radiobiologically sensitive areas (eg. optic nerves and brainstem) the radiation dose should be reduced due to radiotoxic effects. To avoid the consequent therapeutic ineffectiveness, a recently implemented alternative is multisession radiosurgery (RCH).

Radiosurgery with a linear accelerator. Methodological aspects.

Based on the concepts of Leksell and on recommendations of different Swedish physicists on the use of linear accelerator for radiosurgical use, we developed a new methodology coupling the Talairach stereotactic system with a commercial linac. Anatomical facts encouraged us to use coronal angles of irradiation employing the angular displacement of the linac above the horizontal plane. Different coronal planes are obtained by rotation of the stereotactic frame.

[Multiple-beam stereotaxic irradiation].

The "Talairach" stereotactic multibeam irradiation system developed by the authors allows to irradiate selectively small intracranial or intraorbital lesions localized in the Talairach stereotactic system. The centre of the target volume is placed in the isocentre of rotation of a linear accelerator (160 degrees), a special head fixation allows for a stepwise rotation of the head (145 degrees) around the centre of the lesion. Special collimators adapt the width of the high energy photon beam to the dimensions of the target (some millimeters to 3 cm), creating a high dose radiation field limited to the lesion (deep AVM, pituitary adenomas, small gliomas in critical areas etc.