A FRAMELESS STEREOTAXIC APPROACH TO NEUROSURGICAL PLANNING BASED ON RETROSPECTIVE PATIENT-IMAGE REGISTRATION

A frameless stereotactic device interfacing an electromagnetic three-d imensional (3-D) digitizer to a computer workstation is described. The patient-image coordinate transformation was found by retrospectively registering a digitizer-derived model of the patient's scalp with a ma gnetic resonance (MR) imaging-derived model of the same surface. This procedure was performed with routine imaging data, eliminating the nee d to obtain special-purpose MR images with fiducial markers in place. After patient-image fusion was achieved, a hand-held digitizing stylus was moved over the scalp and tracked in real time on cross-sectional and 3-D brain images on the computer screen. This device was used for presurgical localization of lesions in 10 patients with meningeal and superficial brain tumors. The results suggest that the system is accur ate enough (typical error range 3 to 8 mm) to enable the surgeon to re duce the craniotomy to one-half the size advisable with conventional q ualitative presurgical planning.