Preclinical Assessment of Various Technological Aids for Anterior Skull Base Endoscopic Navigation

Objectives: Modern image guidance systems (IGSs) potentially offer a wealth of information to the skull base surgeon. Applications such as 3D reconstructions, virtual views, volume targeting, proximity alerts, and instrument tracking are all possible but are rarely used in practice. Intraoperative CT allows images and navigation to be updated after an ablative procedure is performed. The benefits of near real-time, on-table imaging and augmented IGS are debated, and the methodology is infrequently used because of time, cost, and a sense that these applications may be unreliable and obtrusive and will not aid surgical decision making or safety. This study assesses whether these applications improve navigation and its effect on accuracy and confidence in identifying structures at the entire continuum of surgical experience, from junior residents to skull base surgeons. Methods: Cadaver specimens were partly dissected to allow localization of various anatomical landmarks and structures. Cadavers were scanned with a mobile cone beam CT both before and after dissection and linked with an IGS. Critical structures and important landmarks were contoured to allow display in a virtual view. After a short briefing, subjects located various skull base structures and used a tracked probe to register their position after perceived identification of the landmark. Various levels of technology were used, and the registered position was recorded and measured against a defined “gold standard.” Subjects had access to a preoperative CT scan before and during navigation. Accuracy of endoscopy alone was compared with endoscopy with an augmented 3D virtual view with “wall down” capacity, conventional IGS based on preoperative imaging, and updated IGS based on a post-dissection scan. Questionnaires assessed the degree to which the subjects felt the technology aided their accuracy and confidence in identification of structures, as well as perceived task load. Results: Quantitative data suggested performance improvement that was most significant for the less experienced operator. Qualitative data also suggested that the effect on the confidence of the operator was most significant for the less experienced surgeon. Conclusion: Technology that offered near real-time imaging was most beneficial to the less experienced surgeon, and it may also be beneficial to experienced surgeons in more advanced operations.