A helium-ion beam for stereotactic radiosurgery of central nervous system disorders.

A new radiation beamline configuration for stereotactic heavy-ion Bragg peak radiosurgery of patients with intracranial deep arteriovenous malformations, including carotid-cavernous fistulas, has been developed using the 230 MeV/u helium ion beam at the 184-in. Synchrocyclotron at the University of California, Berkeley. The modified beam has five characteristics: uniform field between 10 and 40 mm in diameter; variable depth of penetration between 40 and 140 mm; stopping region for primary ions that can be broadened up to 40 mm; sharply defined lateral and distal borders; and dose rate greater than 2 Gy/min. It is adapted to the ISAH (irradiation stereotactic apparatus for humans) at the 184-in. Synchrocyclotron, with effective stereotactic localization of defined volumes within the brain, and is designed to reach all intracranial targets. It has proven suitable for all patients with intracranial vascular disorders treated with stereotactic radiosurgery at our laboratory.