2016 Section 5 Green Book

Fig. 1. Manual segmentation of cross-sectional computed tomographic scan images was used to create a three-dimensional virtual view of anatomical structures. A 5 anterior; I 5 inferior; L 5 left; P 5 posterior; R 5 right; S 5 superior.

Contouring pertinent anatomy allows intuitive display of anatomical relationships during surgery. We recognized the need for further interface development and aimed to prepare for clinical introduction of this technology by rigorously testing the system in a preclinical trial. To truly identify the barriers to clinical implementation, we planned an intensive operative exercise in a realistic environment. We elected to exclude inexperienced sur- geons or trainees as subjects to avoid results that may not necessarily reflect the true clinical benefits and costs. We restricted participants to fellowship-trained otolaryngologists or neurosurgeons who regularly per- form endoscopic skull base surgery. Multi-institutional recruitment was required to achieve an experienced cohort. There was a significant time commitment (around 5 hours) from each participant, and the wet lab- oratory was designed to replicate the operating room (OR) environment as closely as possible. Surgeons performed surgical tasks with the LIVE- IGS system and also in a conventional manner so that paired data could be collected. We focused on qualitative feedback to identify interface design issues and target potential improvements. This included visual display settings, auditory alerts, and other ergonomic factors. We intended to update the system in response to feed- back throughout the trial. Task workload was assessed to identify whether this technology altered the demands on the surgeon.

MATERIALS AND METHODS Seven otolaryngology (n 5 5) and neurosurgery (n 5 2) skull base surgeons from five institutions participated in a cadaver dissection trial. Prior to dissection, each head under- went computed tomographic (CT) scanning followed by critical structure manual segmentation using ITK-SNAP 2.0 software. 9 Structures contoured included the carotid arteries, optic nerves, pituitary gland, dura, and orbits. Alert zones of approximately 2 to 3 mm were manually mapped around the carotid arteries and the dura (Fig. 1). This process was undertaken by the investigating surgeons and took approximately 60 minutes per case. In keeping with clinical protocols, we initially performed magnetic resonance imaging, but the quality of the scans was poor on cadaver specimens and offered no advantage over CT for the purposes of this study. CT angiography could not be per- formed on cadavers. The initial surgical approach was performed by the inves- tigators before the subjects started the study task (clivus abla- tion). Ethmoidectomy, posterior septectomy, and a wide, unified sphenoidotomy were performed, and then the heads were reim- aged with a surgical cone-beam CT (CBCT) system. 10 Deforma- ble registration allowed the contours delineated from the preoperative CT to be registered to the intraoperative CBCT imaging. 11 Optical IGS reflective markers were attached to the head, the 0 endoscope (Hopkins II telescope and IMAGE1 camera; Karl Storz, Tuttlingen, Germany), and the drill (M4 hand-piece; Medtronic, Jacksonville, FL). Registration of the head to the imaging data was then undertaken with an optical tracking sys- tem (Polaris; NDI, Waterloo, Ontario, Canada). Fiducial

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