Hinnerk Schulz-Hildebrandt ¹ Svetolik Spasic ^2* Fang Hou ¹ Kuan-Chung Ting ^2* Shelley Batts ² Guillermo Tearney ^1,3,4* Konstantina M. Stankovic ^2,5,6*

• ¹ Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States
• ² Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, United States
• ³ Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States
• ⁴ Harvard-MIT Division of Health Science and Technology, Cambridge, MA, United States
• ⁵ Department of Neurosurgery, School of Medicine, Stanford University, Stanford, California, United States
• ⁶ Wu Tsai Neurosciences Institute, Stanford University, Stanford, California, United States

Sensorineural hearing loss (SNHL) is caused by damage to the mechanosensory hair cells and auditory neurons of the cochlea. The development of imaging tools that can directly visualize or provide functional information about a patient's cochlear cells is critical to identify the pathobiological defect and determine the cells' receptiveness to emerging SNHL treatments. However, the cochlea's small size, embedded location within dense bone, and sensitivity to perturbation have historically precluded high-resolution clinical imaging. Previously, we developed micro-optical coherence tomography (µOCT) as a platform for otologic imaging in animal models and human cochleae. Here we report on advancing µOCT technology to obtain simultaneously acquired and co-localized images of cell viability/metabolic activity through dynamic µOCT (DµOCT) imaging of intracellular motion. DµOCT obtains cross-sectional images of ATP-dependent movement of intracellular organelles and cytoskeletal polymerization by acquiring sequential µOCT images and computing intensity fluctuation frequency metrics on a pixel-wise basis. Using a customized benchtop DµOCT system, we demonstrate the detailed resolution of anatomical and metabolic features of cells within the organ of Corti, via an apical cochleostomy, in freshly-excised adult mouse cochleae. Further, we show that DµOCT is capable of capturing rapid changes in cochlear cell metabolism following an ototoxic insult to induce cell death and actin stabilization. Notably, as few as 6 frames can be used to reconstruct cochlear DµOCT images with sufficient detail to discern individual cells and their metabolic state. Taken together, these results motivate future development of a DµOCT imaging probe for cellular and metabolic diagnosis of SNHL in humans.