Stereotactic frame for neuroradiology and charged particle Bragg peak radiosurgery of intracranial disorders.

The application of heavy charged particle Bragg peak radiosurgery for the treatment of intracranial vascular and other disorders requires a system of precise patient immobilization and stereotactic localization of defined intracranial targets. The process of using stereotactic neuroradiological procedures (including cerebral angiography, CT scanning and magnetic resonance imaging) for target definition and localization, and complex treatment planning constrain such a system to be adaptable and reusable. This paper describes a removable stereotactic frame-mask system that is used to immobilize and reposition the patient during stereotactic neuroradiological procedures and charged particle radiosurgery. It consists of four parts--(a) a plastic mask for immobilizing the patient's head; (b) a lucite-graphite mounting frame; (c) a set of fiducial markers; and (d) interfaces between the frame for immobilization and fixation to various diagnostic and therapeutic patient couches. The relationship between each component and the radiosurgical procedure is discussed. This system has proven to be safe, reliable, and noninvasive and it does not require fixation to the bones of the face or skull. When integrated into the radiosurgical treatment planning and localization procedures developed at Lawrence Berkeley Laboratory, it is capable of reliably repositioning the patient to 1 mm in each of three planes and contouring the intracranial target reliably to this accuracy. The application of this stereotactic system in heavy charged particle radiosurgery of intracranial arteriovenous malformations is described in other reports.