title: Modality-based navigation.
abstract: Modality-based navigation (MBN) means the interactive tracking of instruments in a co-ordinate system defined by an imaging modality, eg, CT, MR, or a fluoroscope. During the registration process, a transformation matrix between the two co-ordinate systems of the digitizer and imaging modality is calculated. Navigation can start immediately after collection of the images without an intraprocedural registration process. Since the imaging modality belongs to the OR or the intervention suite, image update can be performed at any time. Following a step-by-step procedure with navigation and image update in a reasonable sequence, the risk for a virtual-real mismatch is minimized. For CT-MBN, we obtained a freehand absolute positioning accuracy of 1.9+/-1.1 mm in vitro. The in vivo freehand absolute positioning accuracy in pelvic fracture fixation was determined to be 3.1 mm (unpublished data). From our point of view, modality-based navigation is an efficient and safe alternative tool for computer aided interventions.
authors.affiliation: Division of Trauma Surgery, Department of Surgery, University Hospital Zurich, 8091 Zurich, Switzerland. peter.messmer@usz.ch
authors.forename: Peter
authors.initials: P
authors.lastname: Messmer
authors.forename: Thomas
authors.initials: T
authors.lastname: Gross
authors.forename: Norbert
authors.initials: N
authors.lastname: Suhm
authors.forename: Pietro
authors.initials: P
authors.lastname: Regazzoni
authors.forename: Augustinus L
authors.initials: AL
authors.lastname: Jacob
authors.forename: Rolf W
authors.initials: RW
authors.lastname: Huegli
mesh_terms: D005471:Fluoroscopy / Q000379:methods; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods; D019637:Orthopedic Procedures / Q000379:methods*; D011829:Radiation Dosage; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods