Imaging high-frequency periodic motion in the mouse ear with coherently interleaved optical coherence tomography

Abstract

Vibratory measurements of the structures of the ear are key to understanding much of the pathology in mouse models of hearing loss. Unfortunately the high-speed sampling required to interrogate the high end of the mouse hearing spectrum is beyond the reach of most optical coherence tomography (OCT) systems. To address this issue, we have developed an algorithm that enables phase-sensitive OCT measurements over the full range of the mouse hearing spectrum (4-90 kHz). The algorithm phase-locks the line-trigger to the acoustic stimulation and then uses interleaved sampling to reconstruct the signal with higher temporal sampling. The algorithm was evaluated by measuring the vibratory response of mouse tympanic membrane to a pure tone stimulus.

Fig. 1

(Color online) Schematic diagram of coherent interleaving algorithm for three phase steps. Arrows indicate how the samples are interleaved.

Fig. 2

Measured vibrational response, f_meas, from a piezo element without (a) and with (b) coherent interleaved sampling and driven at input frequency, f_in. The amplitude (gray scale) is a logarithm of the measure signal.

Fig. 3

(Color online) (a) B-scan of mouse tympanic membrane. Arrow indicates where the vibratory response was measured. Scale bar is 500 μm. (b) Vibratory response with 30 kHz stimulation (top) and 40 kHz stimulation (bottom). Arrow indicates residual aliased peaks at 6.2 and 17.6 kHz.