Simultaneous 3D imaging of sound-induced motions of the tympanic membrane and middle ear ossicles

Abstract

Efficient transfer of sound by the middle ear ossicles is essential for hearing. Various pathologies can impede the transmission of sound and thereby cause conductive hearing loss. Differential diagnosis of ossicular disorders can be challenging since the ossicles are normally hidden behind the tympanic membrane (TM). Here we describe the use of a technique termed optical coherence tomography (OCT) vibrography to view the sound-induced motion of the TM and ossicles simultaneously. With this method, we were able to capture three-dimensional motion of the intact TM and ossicles of the chinchilla ear with nanometer-scale sensitivity at sound frequencies from 0.5 to 5 kHz. The vibration patterns of the TM were complex and highly frequency dependent with mean amplitudes of 70–120 nm at 100 dB sound pressure level. The TM motion was only marginally sensitive to stapes fixation and incus-stapes joint interruption; however, when additional information derived from the simultaneous measurement of ossicular motion was added, it was possible to clearly distinguish these different simulated pathologies. The technique may be applicable to clinical diagnosis in Otology and to basic research in audition and acoustics.

Investigation of middle ear anatomy and function with combined video otoscopy-phase sensitive OCT

“…The measured sensitivity of the instrument was 0.5nm (calculated for an SNR = 10). This correlate well with sensitivities reported by other groups: 4.8 mrad, reported by Chang et al [20] and 7.5 mrad, reported by Subhash et al [22].…”

“…A pilot study with a handheld OCT scanner has been recently reported [18], where the thickness of the TM was investigated as a diagnostic indicator for otitis media [19]. However, the functional characteristics of the middle ear structures cannot be analyzed with conventional OCT. A newer variant of OCT, called phase-sensitive OCT, has been used by some research groups both in animal models, such as mice and chinchillas, to measure the vibration of the middle ear TM and the ossicles [20], as well as to assess the functionality of the inner ear (e.g. the cochlea) [21].…”

Noninvasive in vivo imaging reveals differences between tectorial membrane and basilar membrane traveling waves in the mouse cochlea

“…First, one must correct for phase jitter caused by wavelength instability inherent to swept-laser sources and asynchrony between the source and sample clocks (22), as both factors impede measurement of subnanometer displacements. Using a phase reference from a nonvibrating structure within the scan can work in some situations (23). However, we completely eliminated phase jitter by calibrating the spectral interferograms every sweep using the phase of the Hilbert transform of the spectral interferograms from a Mach-Zehnder interferometer with a fixed optical delay that were simultaneously acquired.…”

Observation of sound-induced corneal vibrational modes by optical coherence tomography

“…The spatial profile of corneal vibration was determined by using the principle of vibrography previously described [19,20]. Briefly, at a constant sound frequency the optical beam was scanned along a line (~10 mm) or over an area.…”