Reconstruction of transverse-longitudinal vibrations in the organ of Corti complex via optical coherence tomography

Optical coherence tomography (OCT) is a common modality for measuring vibrations within the organ of Corti complex (OCC) in vivo. OCT's uniaxial nature leads to limitations that complicate the interpretation of data from cochlear mechanics experiments. The relationship between the optical axis (axis of motion measurement) and anatomically relevant axes in the cochlea varies across experiments, and generally is not known. This leads to characteristically different motion measurements taken from the same structure at different orientations. We present a method that can reconstruct two-dimensional (2-D) motion of intra-OCC structures in the cochlea's longitudinal-transverse plane. The method requires only a single, unmodified OCT system, and does not require any prior knowledge of precise structural locations or measurement angles. It uses the cochlea's traveling wave to register points between measurements taken at multiple viewing angles. We use this method to reconstruct 2-D motion at the outer hair cell/Deiters cell junction in the gerbil base, and show that reconstructed transverse motion resembles directly measured transverse motion, thus validating the method. The technique clarifies the interpretation of OCT measurements, enhancing their utility in probing the micromechanics of the cochlea.