Localized vibrations incorporated thickness assessment of cadaveric tympanic membranes using Doppler-optical coherence tomography

Vibrations of the tympanic membrane (TM) play a key role in the diagnosis of the middle ear in hearing research. The thickness is one of the factors that determines performance analysis of the TM and plays an important role in forming vibration patterns. When the thickness of TM is changed for various reasons, the vibration pattern is also changed, which interferes with sound transmission. The previously reported studies of measuring TM obtained the response of the entire or at a single point to understand the characteristics of the TM, which is limited to providing detailed information for the region of interest. However, in terms of the clinical applications, the various medical care including TM reconstruction, treatment of perforation, and otitis media with effusion, were mainly performed on a specific part of the TM rather than the whole range. In recent studies, optical coherence tomography (OCT) technology has been employed to visualize whole TM structures with exceptional resolution, while Doppler-OCT has emphasized the appropriateness of this technology for the identification of TM functionality. Since anomalies in vibration patterns of TM can cause hearing loss, Doppler-OCT was incorporated in the proposed scheme to investigate the functionality of TM by localizing vibrations and assessing thickness information of specific vibrating region. However, we focused on analyzing the difference in the TM response according to the thickness and structural changes at each sound wave frequencies. These vibrations and their corresponding tomographic thickness measurements were obtained from ex vivo cadaveric TM specimen placed in a soundproof chamber and was exposed to pure-tone sound frequencies, such as 1, 2, 4, and 6 kHz, respectively. Subsequently, a laboratory-customized cross-sectional image segmentation method was employed to obtain precise correlation between localized vibrations and TM thickness. Since the hearing abnormalities were occurred due to changes of structural formation and functionality, the qualitative and quantitative results of this demonstration are able to simultaneously provide vibration and thickness information for the actual target region and it suggests a possibility to apply for clinical applications, which require a target region-based data.