Long-wavelength 1.7-micron optical coherence tomography for otologic imaging and hearing research

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PROJECT SUMMARY/ABSTRACT Hearing loss affects the quality of life in nearly one-in-four adults in the United States, yet in many cases it is difficult to identify the cause. CT imaging can provide high-resolution contrast in the small bony structures in the middle/inner ear, and MRI can provide medium-resolution contrast in soft tissues, but there exists a need for high-resolution imaging of the soft cochlear tissues. Optical coherence tomography (OCT) is one technology that can fill this need and is gaining traction as a potential method for non-invasive otologic imaging due to its ability to record high-resolution volumetric images, blood flow, and vibrations through several millimeters of tissue. These advantages have also made OCT a popular tool in basic hearing research. Cochlear blood flow is a particularly useful metric to quantify since animal models of noise-induced hearing loss, and cadaveric studies of age-related hearing loss have identified impaired cochlear blood flow as part of their etiology. Vibrometry is another useful metric since in-vivo measurements of cochlear tuning and gain are being used to investigate cochlear mechanics in animal models. However, current OCT systems operating at 1.3 μm are limited in their ability to penetrate the bony otic capsule in humans, and also into the basal turn of the mouse cochlea. Extending the imaging depth of OCT may enable collection of blood flow and vibrometry data from physiologically important locations, such as the stria vascularis in humans and the basal turn of the mouse cochlea, which have been difficult to image using 1.3 µm OCT. Therefore, we aim to develop long- wavelength 1.7 μm OCT systems that will enable deeper imaging due to reduced tissue scattering at 1.7 µm. We aim to develop a handheld OCT otoscope device for non-invasive clinical imaging and blood flow quantification in the human cochlea via the ear canal. This may enable the first non-invasive measurements of cochlear blood flow in humans. We also aim to develop a benchtop stereomicroscope OCT system operating at 1.7 μm to enable OCT vibrometry in the basal turn of the mouse cochlea, where documented differences in cochlear mechanics remain to be explored. Completion of this project will result in the creation of new imaging devices for the otology clinic and for basic hearing research.