FRAMELESS ISOCENTRIC STEREOTAXIC LASER-BEAM GUIDE FOR IMAGE-DIRECTED MICROSURGERY

We have developed a frameless stereotactic multi-articulated arm suita ble for image-directed microsurgery and surgical navigation. The syste m comprises a frameless isocentric mechanism and a three-dimensional ( 3 D) digitizer for intra-operative monitoring. Five joints of our mult i-articulated arm are equipped with electromagnetic clutches, and the arms are provided with counterbalancing weights to ensure safe, smooth movement. Stereotactic microsurgical procedures were carried out with a laser beam guide mounted at the tip of the isocentric arm. We have used this system in 22 cases to resect tumours or epileptic foci. Ther e were 12 cases of glioma, 5 cases of deep seated benign tumours, 3 ca ses of multiple metastatic tumours, and 2 cases of temporal lobe epile psy. Postoperative enhanced CT images indicated total or subtotal rese ction in all cases. We also have used this system to determine the app roach for clipping of a posterior cerebral artery aneurysm in 2 cases. The error of mechanical accuracy of the system was less than 1 mm. We believe that this system will prove useful in image-directed microsur gical procedures.