OCT has been exploited extensively in studies of cochlear mechanics due to its ability to non-invasively measure vibrations of various cochlear structures. A key limitation has been the ability to measure only in one dimension, along the optical axis. However, recent evidence suggests the organ of Corti has complex, three-dimensional vibratory micromechanics. Therefore, a 3D-OCT vibrometry system has been developed to measure the vector of motion within the cochlea and hopefully shed light on the underlying mechanics that lead to cochlear amplification and the exquisite sensitivity and frequency selectivity of mammalian hearing. The system uses three independent sample arms (channels) with a single reference arm to acquire vibrations, exploiting the long coherence length of the laser to depth encode the three channels. The system was first validated using a piezoelectric actuator. This yielded an RMS error of ≤0.3° in both polar angles with expected sensitivity to vibrational amplitude. Preliminary measurements in the cochlea of a live mouse demonstrate direction-dependent differences in vibratory responses.
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