title: Interactive navigation-guided ophthalmic plastic surgery: assessment of optical versus electromagnetic modes and role of dynamic reference frame location using navigation-enabled human skulls.
abstract: OBJECTIVE
  The aim of this study was to assess the anatomical accuracy of navigation technology in localizing defined anatomic landmarks within the orbit with respect to type of technology (optical versus electromagnetic systems) and position of the dynamic reference marker on the skull (vertex, temporal, parietal, and mastoid) using in vitro navigation-enabled human skulls. The role of this model as a possible learning tool for anatomicoradiological correlations was also assessed.
  
  
  METHODS
  Computed tomography (CT) scans were performed on three cadaveric human skulls using the standard image-guidance acquisition protocols. Thirty-five anatomical landmarks were identified for stereotactic navigation using the image-guided StealthStation S7™ in both electromagnetic and optical modes. Three outcome measures studied were accuracy of anatomical localization and its repeatability, comparisons between the electromagnetic and optical modes in assessing radiological accuracy, and the efficacy of dynamic reference frame (DRF) at different locations on the skull.
  
  
  RESULTS
  The geometric localization of all the identified anatomical landmarks could be achieved accurately. The Cohen's kappa agreements between the surgeons were found to be perfect (kappa =0.941) at all predetermined points. There was no difference in anatomical localization between the optical and electromagnetic modes (P≤0.001). Precision for radiological identification did not differ with various positions of the DRF. Skulls with intact anatomical details and careful CT image acquisitions were found to be stereotactically useful.
  
  
  CONCLUSIONS
  Accuracy of anatomic localization within the orbit with navigation technology is equal with optical and electromagnetic system. The location of DRF does not affect the accuracy. Navigation-enabled skull models can be potentially useful as teaching tools for achieving the accurate radiological orientation of orbital and periorbital structures.
authors.affiliation: Ophthalmic Plastic Surgery Service.
authors.forename: Mohammad Javed
authors.initials: MJ
authors.lastname: Ali
authors.affiliation: Ophthalmic Plastic Surgery Service.
authors.forename: Milind N
authors.initials: MN
authors.lastname: Naik
authors.affiliation: Ophthalmic Plastic Surgery Service.
authors.forename: Chetan Mallikarjuniah
authors.initials: CM
authors.lastname: Girish
authors.affiliation: The Operation Eyesight Universal Institute for Eye Cancer, L.V. Prasad Eye Institute, Hyderabad, India.
authors.forename: Mohammad Hasnat
authors.initials: MH
authors.lastname: Ali
authors.affiliation: The Operation Eyesight Universal Institute for Eye Cancer, L.V. Prasad Eye Institute, Hyderabad, India.
authors.forename: Swathi
authors.initials: S
authors.lastname: Kaliki
authors.affiliation: Ophthalmic Plastic Surgery Service.
authors.forename: Tarjani Vivek
authors.initials: TV
authors.lastname: Dave
authors.affiliation: Ophthalmic Plastic Surgery Service.
authors.forename: Gautam
authors.initials: G
authors.lastname: Dendukuri
keywords: anatomy; image guidance; navigation; ophthalmic plastic surgery; orbit; teaching model