A frameless method for 3D MRI- and CT guided stereotaxic localisation

Abstract

MR and CT are well recognized as the best imaging procedures for localisation in stereotaxic neurosurgery. However special difficulties necessitate specific adaptation to: localise targets in the steriotaxic frame. A method using MR and CT images is presented: no special frame must be. used during imaging examinations, but only the four intracranian holders of the neurosurgical stereotaxic frame. The images data are transferred to: a PC-based system for 3D localisation of brain targets. By locating the four markers on the images, the transformation matrices can be computed to: obtain the coordinates of a lesion in the stereotaxic space. The system calculates the arc setting parameters of a probe trajectory to: the target, either for an orthogonal or a double oblique approach if needed. Simulated probe trajectory intersections with the consecutive slices can be viewed in order to: validate the trajectory before the surgical procedure. The systematic geometrical errors have been carefully evaluated. Original procedures and corrective algorithms have been implemented as well as checks to: detect geometrical distortion or movements made by the patient. In this way, millimeter accuracy is achieved in the three dimensions.