FRAMELESS STEREOTAXIC LESION CONTOUR-GUIDED SURGERY USING A COMPUTER-NAVIGATED MICROSCOPE

BACKGROUND The Zeiss MKM System is a recently developed computerized o perating microscope for image-guided neurosurgery. The clinical advant ages, reliability, accuracy, and limitations of this technique were in vestigated. METHODS Since February 1995, 78 consecutive frameless ster eotactic image-guided procedures were performed in 73 patients (30 mal es, 43 females; mean age, 46.9 years; range, 16-77 years) for tumor su rgery (50/64.1%), cavernoma removal (16/20.5%), and functional procedu res (12/15.4%). Skin markers (74 cases) or bone markers (4 cases) and a standard imaging protocol (2-mm cranial computed tomography (CCT) in 59 cases/1.5-mm magnetic resonance imaging (MRI) in 19 cases) were us ed. RESULTS The main advantages were pre-operative skin incision, cran iotomy and corticotomy planning, and determination of lesion boundarie s. Useful registration and system reliability were noted in 97% (76/78 ) of the procedures. A significant improvement in registration accurac y was observed over the test period from a mean of 4.8 mm (SD = 3.36; Cases 1-25) to a mean of 2.2 mm (SD = 0.86; Cases 26-78). This resulte d in an improvement in application accuracy from <5 mm in 71% (Cases 1 -25) to <2 mm in 95% (Cases 26-78) of cases, and the accuracy led to s uccessful localization of the lesion in every case. Accuracy was relia ble at the beginning of every procedure, but degraded to values >5 mm by the end of the procedure in 29% (22/78) of cases. MRI cases achieve d higher application accuracy values (2.1 mm mean) than CT cases (3.7 mm mean). CONCLUSIONS The system offers a reliable alternative to fram e-assisted stereotactic craniotomies in lesion targeting, but would ne ed an intraoperative image update for resection guidance. (C) 1998 by Elsevier Science Inc.