title: Frameless stereotactic lesion contour-guided surgery using a computer-navigated microscope.
abstract: BACKGROUND
  The Zeiss MKM System is a recently developed computerized operating microscope for image-guided neurosurgery. The clinical advantages, reliability, accuracy, and limitations of this technique were investigated.
  
  
  METHODS
  Since February 1995, 78 consecutive frameless stereotactic image-guided procedures were performed in 73 patients (30 males, 43 females; mean age, 46.9 years; range, 16-77 years) for tumor surgery (50/64.1%), cavernoma removal (16/20.5%), and functional procedures (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 used.
  
  
  RESULTS
  The main advantages were pre-operative skin incision, craniotomy and corticotomy planning, and determination of lesion boundaries. Useful registration and system reliability were noted in 97% (76/78) of the procedures. A significant improvement in registration accuracy 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 resulted 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 successful localization of the lesion in every case. Accuracy was reliable 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 achieved higher application accuracy values (2.1 mm mean) than CT cases (3.7 mm mean).
  
  
  CONCLUSIONS
  The system offers a reliable alternative to frame-assisted stereotactic craniotomies in lesion targeting, but would need an intraoperative image update for resection guidance.
authors.affiliation: Department of Neurosurgery, University of Vienna Medical School, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Roessler
authors.forename: K
authors.initials: K
authors.lastname: Ungersboeck
authors.forename: M
authors.initials: M
authors.lastname: Aichholzer
authors.forename: W
authors.initials: W
authors.lastname: Dietrich
authors.forename: H
authors.initials: H
authors.lastname: Goerzer
authors.forename: C
authors.initials: C
authors.lastname: Matula
authors.forename: T
authors.initials: T
authors.lastname: Czech
authors.forename: W T
authors.initials: WT
authors.lastname: Koos
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001927:Brain Diseases / Q000601:surgery*; D001932:Brain Neoplasms / Q000601:surgery; D004827:Epilepsy / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008853:Microscopy / Q000295:instrumentation; D008875:Middle Aged; D016634:Radiosurgery / Q000295:instrumentation* / Q000379:methods; D016896:Treatment Outcome