COCHLEAR IMPLANTSComparing Cochlear Duct Lengths Between CT and MR Images Using an Otological Surgical Planning SoftwareGeorge-Jones, Nicholas A.∗; Tolisano, Anthony M.†; Kutz, J. Walter Jr∗; Isaacson, Brandon∗; Hunter, Jacob B.∗Author Information ∗Department of Otolaryngology—Head and Neck Surgery, University of Texas Southwestern Medical Center, Dallas, Texas †Department of Otolaryngology—Head and Neck Surgery, Walter Reed National Military Medical Center, Bethesda, Maryland Address correspondence and reprint requests to Jacob B. Hunter, M.D., Department of Otolaryngology—Head and Neck Surgery, University of Texas Southwestern Medical Center, 2001 Inwood Road, Dallas, TX 75235; E-mail: [email protected] This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. J.B.H. has been provided the software and travel support from MED-EL Corporation. N.A.G.-J., A.M.T., J.W.K., and B.I. declare that involvement in research was conducted in the absence of any commercial or financial relationships. Institutional Review Board Approval: STU 032018-085. The views expressed in this manuscript are those of the author(s) and do not reflect the official policy or position of the Department of the Army, Department of Defense, or the US Government. The authors disclose no conflicts of interest. Otology & Neurotology: October 2020 - Volume 41 - Issue 9 - p e1118-e1121 doi: 10.1097/MAO.0000000000002777 Buy Metrics Abstract Objective: We sought to examine the intra- and interobserver variability in measuring the cochlear duct length (CDL) from magnetic resonance imaging (MRI) images versus computed tomography (CT) images using an otological surgical planning software that uses measurements of the basal turn diameter and cochlear width to estimate the CDL. Patients: Twenty-one adult cochlear implant patients with preoperative MRI and CT images. Intervention: Three fellowship-trained neurotologists served as the raters in the study. One rater measured the CDL using preoperative CT scans to serve as the benchmark. Two of the raters measured the CDL on preoperative MRI scans. One rater also remeasured the scans using MRI images after a period of 1 week to assess intraobserver variability. Main Outcome Measure: Intraclass correlational coefficients were calculated to assess for intra- and interobserver agreement. Results: The mean CDL measured from the CT scans was 32.7 ± 2.0 mm (range 29.4 – 37.6 mm). The mean difference between the raters when measuring the CDL using MRI scans was −0.15 ± 2.1 mm (range −3.2 to 4.3 mm). The intraclass correlational coefficients for inter-rater reliability of CDL determination using MRI scans was judged as fair to excellent (0.68; 95% CI 0.41–0.84). The intrarater reliability of CDL determination using MRI scans was judged at fair to excellent (0.73; 95% CI 0.491–0.866). Conclusion: We demonstrate that a validated otological surgical planning software for estimating the CDL preoperatively had comparable performance using MRI scans versus the gold-standard CT scans. © 2020, Otology & Neurotology, Inc.