Extratympanic imaging of middle and inner ear structures of mouse and rat using optical coherence tomography

Background and Objective: Noninvasive middle and inner ear imaging using optical coherence tomography (OCT) presents some unique challenges for real-time, clinical use in animals and humans. The goal of this study was to investigate whether OCT provides information about the middle and inner ear microstructures by examining extratympanic structures. Materials and Methods: Five mice and rats were included in the experiment, and the swept-source OCT system was tested to identify the middle and inner ear microstructures and to measure the length or thickness of various structures. Results: It was possible to see middle ear structures through the tympanic membrane with the OCT instrument located extratympanically in both rats and mice. We could also obtain the inner ear images through the otic capsule in the mice, but the bulla needed to be removed to visualize the inner ear structures in the rats. The whole apical, middle and basals of the cochlea and the thickness of the otic capsule covering the cochlea could be visualized simultaneously. Conclusions: OCT is a promising technology to assess middle ear and inner ear microanatomy noninvasively in both mice and rats. OCT imaging could provide additional diagnostic information about the diseases of the middle and inner ear.