title: [A new method for computer-assisted orbitotomies].
abstract: BACKGROUND
  Surgical planning and tumor margins from preoperative image data sets can be transferred to the surgical site by use of computer-assisted navigation systems. Usually registration markers are placed prior to image data acquisition in order to correlate the patient's preoperative image data set with his/her position in the operating room. Pointers are commonly used for navigation, and the position of the pointer within the surgical site is compared to its position within the image data set. With a new navigation system, patient registration can be performed without registration markers. Tumor margins and osteotomy lines can be projected onto the surgical site.
  
  
  METHODS
  With the new navigation system, which has been developed by the Sonderforschungsbereich 414 of the Deutsche Forschungsgemeinschaft, markerless patient registration is performed using the contours of the patient's face. A scanner is mounted above the operating table, which detects the surface of the surgical site intraoperatively. Osteotomy lines and tumor margins are projected onto this surface using an intense beamer. The procedure is illustrated for a patient with a meningeal tumor of the orbit.
  
  
  RESULTS
  Patients can be registered with an accuracy of 1 mm. Pointers are not required to transfer the data on the surgical site. Furthermore, monitors are no longer required, since the information is projected directly on the patient's surface.
  
  
  CONCLUSIONS
  Surgical planning and tumor margins can exactly be visualized within the surgical site. Ergonomics are especially improved for navigated orbitotomies via a coronal approach.
authors.affiliation: Klinik und Poliklinik für Mund-, Kiefer- und Gesichtschirurgie der Universität Heidelberg. Ruediger_Marmulla@med.uni-heidelberg.de
authors.forename: R
authors.initials: R
authors.lastname: Marmulla
authors.forename: H
authors.initials: H
authors.lastname: Hoppe
authors.forename: G
authors.initials: G
authors.lastname: Kolling
authors.forename: J
authors.initials: J
authors.lastname: Mühling
authors.forename: S
authors.initials: S
authors.lastname: Hassfeld
mesh_terms: D000328:Adult; D004867:Equipment Design; D006804:Ergonomics; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation; D021621:Imaging, Three-Dimensional / Q000295:instrumentation; D008279:Magnetic Resonance Imaging / Q000295:instrumentation; D008297:Male; D008577:Meningeal Neoplasms / Q000175:diagnosis / Q000601:surgery*; D008579:Meningioma / Q000175:diagnosis / Q000601:surgery*; D019060:Minimally Invasive Surgical Procedures / Q000295:instrumentation; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis / Q000601:surgery*; D009918:Orbital Neoplasms / Q000601:surgery*; D010027:Osteotomy / Q000295:instrumentation; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*