Registration accuracy and surface marking of an electromagnetic navigation system for use in endoscopic sinus surgery

Introduction: Since its introduction, surgical navigation systems have become integrated into surgical practices that include complex nasal endoscopic procedures to avoid serious complication such as injury to the optic nerve, the carotid artery, the dura mater and the brain parenchyma. Objective: We aimed to determine the accuracy of image guided system (IGS) by using different timing interval of computed tomography scan of paranasal sinus and our experience in performing the surface marking. Methods: A cross sectional study was done. Subjects were recruited from patients planned for endoscopic sinus surgery with IGS, who met the inclusion and exclusion criteria. The image guided navigation measurements were compared to the actual anatomical measurements of intercanthal distance of both eyes and the tangential line of inverted triangle to the philtrum. The estimated time to register the IGS was recorded. All measurements were done at the same time as the calibration of the IGS. Results: The mean intercanthal distance measured by IGS was 38.17 mm (SD 3.34) whereas the actual intercanthal distance was 38.17 mm (SD 3.37 mm). The tangential line measured by IGS was 46.62 (SD 3.39) whereas the actual measurement of the tangential line was 46.47mm (SD 3.27). The was no significant difference in both measurements between IGS and actual anatomical measurements (p¬=0.804 and 0.496, respectively). Conclusions: Even with the different intervals there was not much deviation from the actual anatomical distance. The IGS is accurate and is applicable for use in Asian patients.