Combined image guidance and intraoperative computed tomography in facilitating endoscopic orientation within and around the paranasal sinuses

Background: The utility of image guidance (image-guided surgery [IGS]) and intraoperative computed tomography (CT) scanning as a tool for less experienced endoscopic surgeons to aid in localization of paranasal sinus and skull base anatomic structures was evaluated. Methods: Partial endoscopic dissection was performed on cadaver specimens by three fellowship trained rhinologists. Anatomic sites within and around the sinuses were tagged with radio-opaque markers. Otolaryngology residents identified tagged anatomic sites using four successive levels of technology: endoscopy alone (simulating outpatient clinic), endoscopy plus preoperative CT (simulating endoscopic sinus surgery [ESS] without IGS), endoscopy plus IGS registered to preoperative CT (simulating current ESS with IGS), and endascopy plus IGS registered to real-time intraoperative CT. Responses were graded as follows: consensus rhinologist answer (4 points), close answer without clinically significant difference (3 points), witkin anatomic region but definite clinical difference (2 points), outside of anatomic region (2 point), no answer (0 points). Results: Eleven residents participated. Of 20 specific anatomic sites, IGS-intraoperative CT provided the most accurate anatomic identification at 16 sites. For 8 sites, IGS-intraoperative CT had a significantly higher score than endoscopy alone (p < 0.05, eta² = 0.29-0.67). For 6 sites, IGS-preoperative CT scan had a significantly higher score than endoscopy alone (p < 0.05; eta² = 0.30-0.67). All participants found that IGS-intraoperative CT scan made them most comfortable in identifying anatomy. Conclusion: Combined IGS and intraoperative CT scan technology may be an instructional adjunct for less experienced paranasal sinus surgeons for dissection and evaluation of unfamiliar or distorted anatomy.