Importance: Middle ear OCT imaging in patients has not previously been directly compared to a standard of care clinical 3D imaging technology such as CT. This represents the first such comparison and provides new insight into OCT's capabilities, strengths and limitations. Objective: To qualitatively compare the capabilities of middle ear OCT to CT in normal and pathological ears on representative slices in co-registered OCT and CT datasets. Design, Setting, and Participants: One normal middle ear, one ear affected by traumatic injury and one ear with cholesteatoma were imaged with both OCT and high-resolution clinical temporal bone CT. Participants were drawn from the patient population of a tertiary otology clinic. CT and OCT images were aligned using rigid co-registration with manual landmark selection. Main Outcomes and Measures: Images were analyzed qualitatively for field of view, resolution, shadowing, artefacts, soft tissue and bony tissue contrast and presentation of diagnostically important features. Results: In the three imaged ears, OCT was capable of visualizing many of the important features indicative of middle ear pathology. When compared to CT, OCT was found to exhibit a limited field of view (FOV) largely confined to the mesotympanum and subject to shadowing from bony structures. However, OCT could resolve soft tissue features that were not readily apparent in the CT images, to have a higher resolution than CT and to provide excellent anatomical fidelity with CT which allowed OCT images to be accurately co-registered with CT images. Conclusions and Relevance: The results support a role for middle ear OCT in otological diagnostics. While OCT is not capable of replacing CT due to its limited FOV and inability to image through thick bony tissues, it can visualize many signs of pathology including some soft tissue features that are difficult to visualize with CT. Given OCT's ability to image in real-time, its compatibility with in-office imaging and its lack of ionizing radiation, it may, despite its limitations compared to CT, be an appealing imaging modality for many applications in middle ear diagnostics.

Mr. Wang, Drs. Farrell, Morris, Adamson reported owning equity in Audioptics Medical Inc., a start-up company working to commercialize middle ear optical coherence tomography technology during the conduct of the study. Drs Couvreur, Ghedia, Shoman reported no conflict.

This study was supported by the Natural Sciences and Engineering Research Council of Canada (501100000038) 151950 and Canadian Institutes of Health Research (501100000024) PJT180435.

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The study was performed at a hospital tertiary otology clinic (QEII Health Sciences Centre) under approval from the hospital's Research Ethics Board (File #1019922). Informed consent was obtained in accordance with the Helsinki Declaration (JAMA 2000; 284:3043-3049).

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