title: Accuracy assessment for navigated maxillo-facial surgery using an electromagnetic tracking device.
abstract: OBJECTIVE
  To evaluate the accuracy and the usability of an electromagnetic tracking device in maxillo-facial surgery through testing on a phantom skull under operating room (OR) conditions.
  
  
  METHODS
  A standard plastic skull phantom was equipped with a custom made model of the maxilla and with target markers and dental brackets. Imaging was performed with a computed tomography (CT) scanner. The extent and robustness of the electromagnetic tracking system's target registration error (TRE) was evaluated under various conditions.
  
  
  RESULTS
  For each measurement a total of 243 registrations were performed with 5 point registration and 4374 registrations with 6 point registration. The average target registration error for the 5 point registration under OR conditions was 2.1 mm (SD 0.86) and 1.03 (SD 0.53) for the 6 point registration. Metallic instruments applied to the skull increased the TRE significantly in both registration methods.
  
  
  CONCLUSIONS
  The electromagnetic tracking device showed a high accuracy and performed stable in both registration methods. Electromagnetic interference due to metallic instruments was significant but the extent of TRE was still acceptable in comparison to optical navigation devices. A benefit of EM tracking is the absence of line-of-sight hindrance. The test setting simulating OR conditions has proven suitable for further studies.
authors: Department of Oral and Maxillofacial Surgery, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany. robin.seeberger@med.uni-heidelberg.de
authors: Robin
authors: R
authors: Seeberger
authors: Gavin
authors: G
authors: Kane
authors: Juergen
authors: J
authors: Hoffmann
authors: Georg
authors: G
authors: Eggers
mesh_terms: D055615:Electrical Equipment and Supplies; D055590:Electromagnetic Phenomena; D057918:Fiducial Markers; D006801:Humans; D008437:Maxilla / Q000000981:diagnostic imaging / Q000601:surgery*; D008953:Models, Anatomic; D010363:Pattern Recognition, Automated / Q000379:methods; D019047:Phantoms, Imaging; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D012886:Skull / Q000000981:diagnostic imaging; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*; D013515:Surgery, Oral / Q000295:instrumentation*; D015898:Tomography Scanners, X-Ray Computed; D036542:Tomography, Spiral Computed