The long-term goal of this project is to determine how the structure and mechanical properties of human ear affect acoustic-mechanical transmission through the external ear canal and middle ear to inner ear (or cochlea) in normal, pathological and reconstructed ears. Our hypothesis is that incorporation of our 3-D comprehensive FE model of the human ear into clinical tympanometry, a diagnostic tool commonly used on middle ear diseases, and laser Doppler interferometry, a potential clinical tool for diagnosis of conductive hearing loss, can improve the diagnosis of otitis media with effusion (OME). There are four specific aims proposed here: (1) to identify how alterations in middle ear structures affect sound transmission from the ear canal through the middle ear to the cochlea measured with laser interferometry and tympanometry; (2) to measure mechanical properties or viscoelasticity of middle ear tissues such as the ligaments and tympanic membrane; (3) to develop multi-field (i.e., acoustic-structure-fluid) coupled analysis of the 3-D FE model with structural alterations in middle ear on human temporal bones; and (4) To correlate our 3-D FE model results with clinical measurements obtained by tympanometry and laser interferometry for improvement of the diagnosis of middle ear diseases such as OME. Four unique approaches are incorporated in the project: (a) accurate geometric reconstruction of entire human ear based on histological images of temporal bone morphometry; (b) direct, accurate measurement of viscoelastic properties of middle ear tissues using the nanoindentation system and digital image correlation techniques; (c) improved human temporal bone experiment with dual laser Doppler interferometry system to measure simultaneously the acoustic-mechanical conduction through the middle ear; and (d) coupled acoustic-structure-fluid analysis of sound transmission from the ear canal to middle ear, and to the cochlea. Experiments described in this proposal will show how changes in middle ear structure and cochlear load affect the sound transmission in the ear. The FE model will demonstrate the potential clinical applications on how the middle ear fluid, ligament cut or removal, and ossicular disarticulation, fixation, or necrosis affect the middle ear transfer function. Thus, the results will be essential for improving the diagnosis of OME, assessing surgical treatment for conductive hearing loss, and potentially improve the quality of life for millions of people.
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