Abstract
Objectives: Application of image-guided surgery to otology has been limited by the need for submillimeter accuracy via a fiducial system that is easily useable (noninvasive and nonobstructive). Our goal was to overcome these limitations and demonstrate the feasibility of image-guided otologic surgery.
Methods: A dental bite-block was constructed to which a rigid frame was attached with extensions surrounding each external ear. This device was fitted to a cadaveric skull with 9 fiducial markers surrounding each ear. Two additional markers were placed at surgically significant locations. CT scanning was performed using temporal-bone algorithms (thickness = 0.5 mm). The markers' locations were measured in physical space using an image-acquisition system based on infrared optical tracking.
Results: With all 18 fiducial markers used for registration, target errors (TRE) for the surgical sites (TRE1 = internal auditory canal and TRE2 = stylomastoid foramen) were 0.41 mm and 0.90 mm, respectively. Surrounding the ear of interest with markers (9 markers) and balancing this with a single, centrally placed marker on the contralateral side produced similar results (TRE1 = 0.52 mm and TRE2 = 0.90 mm). For the inverse situation (9 markers surrounding the contralateral ear and 1 marker near the ear of interest), the worst results of 17 combinations of markers were obtained (TRE = 1.26 mm and TRE2 = 1.80 mm). Submillimeter error was reproducibly achievable using 5 markers surrounding the ear of interest and a centrally located marker on the contralateral side.
Conclusions: These findings show that image-guided otologic surgery with submillimeter accuracy is achievable with a minimally invasive fiducial frame.