Bite-Block Relocation Error in Image-Guided Otologic Surgery

Otologic surgery is undertaken to treat ailments of the ear including persistent infections, hearing loss, vertigo, and cancer. Typically performed on healthy patients in outpatient facilities, the application of image-guided surgery has been limited because accurate (<1mm), non-invasive fiducial systems for otologic surgery are not available. We have developed such a system, which repeatably attaches to a subject via a dental bite block [1]. In a previous report, ex-vivo validation indicated that mean target registration error ± standard deviation for 234 targets within the surgical field was 0.73±0.23mm with a root mean square of 0.77mm [2,3]. In an effort to further understand the limitations of our system, we undertook, and report herein, a detailed error analysis to determine what portion of the error is attributable to the inaccuracies in relocation fit of the fiducial frame to a subject’s dentition. Our analysis shows that the root-mean-square error due to relocation alone is approximately 0.66 mm, while that due to fiducial registration is approximately 0.30 mm.