Rong Z. Gan - US grants

DESCRIPTION (provided by applicant): 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.

Proposal Title: Mechanics of Auditory System - Computational Modeling and Experimental Measurement

P.I.: Rong Z. Gan, Ph.D., University of Oklahoma

Abstract:

The goal of this project is to determine how the structure and mechanical properties of human auditory system affect sound transmission. We seek to use biomechanics systems methodology through both experimental measurement and computational modeling to reach this goal. There are three objectives: (1) to measure viscoelastic properties of the ear tissues (e.g., eardrum and ligaments); (2) to develop multi-field coupled analysis of the 3-D finite element (FE) model with normal and alternative middle ear structures; and (3) to correlate the 3-D FE model with acoustic-mechanical measurements on human temporal bones using laser Doppler interferometry. Four multi-disciplinary approaches are incorporated in the project: accurate geometric reconstruction of entire human ear, measurements of viscoelastic properties of ear tissues using the nanoindentation system and digital image correlation techniques, coupled acoustic-structure-fluid FE analysis of sound transmission, and measurement of acoustic-mechanical conduction through the ear with laser interferometry. The biomechanics systems methodologies in this proposal will provide a vital bridge between auditory mechanics of the ear and hearing restoration and rehabilitation. It will enhance the level of education associated with these areas and potentially improve quality of life for millions of people with hearing disabilities.

DESCRIPTION (provided by applicant): The middle ear, composed of ossicles and soft tissues including the tympanic membrane, ligaments, and joints plays a vital role in the transmission of sound and the sense of hearing. The mechanical properties of soft tissues change in middle ear diseases such as otitis media. As a consequence, the mobility of ossicular chain is reduced and significant conductive hearing loss occurs in otitis media ears. However, the mechanical property changes in soft tissue associated with disease are largely unstudied. It is almost impossible to identify mechanical changes of middle ear tissues in relation to hearing loss based on current clinical tools. The goal of this project is to characterize the biomechanical behaviors of soft tissues in normal and diseased ears, identify soft tissue changes which are associated with changes in normal hearing, and provide an improved 3-dimensional (3D) ear model to visualize and quantify structure-function relations in various diseases. Otitis media (OM) will be the primary focus for the project. Three specific aims are proposed: Aim 1: To Identify changes of mechanical properties of middle ear soft tissue in OM. We hypothesize that the change of mechanical properties of ear tissues in OM is related to morphological changes of the tissue in response to fluid, pressure, and duration of the OM. This hypothesis will be tested by comparison of measurement results of the ear tissues between normal and diseased ears in chinchillas using dynamic mechanical analyzer, split Hopkinson tension bar, acoustic driving with laser Doppler vibrometry (LDV), fringe Moiri system, and FE modeling of soft tissue. Aim 2: To quantify the effect of biomechanical changes of the middle ear on sound transmission in OM. It is hypothesized that the hearing loss in OM is caused by a combination of changes of ear tissues, fluid, and pressure in the middle ear. This hypothesis will be tested by measuring the ABR thresholds and the changes of middle ear transfer function and sound energy transmission in chinchilla OM ears with a novel theoretical analysis of fluid, pressure, and tissue properties with the aid of FE model of chinchilla ear to describe the mechanism of OM. Aim 3: To continue the development of our 3D FE model of the human ear with clinically-relevant applications. We will incorporate into the model with tissue properties determined in Aims 1 and 2, the microstructures of the TM and ISJ, and the stapedius muscle function. A FE model of pediatric ear will be created for studying OM in young children. The acoustic-mechanical vibration and energy transmission through the middle ear in diseased ears will be visualized and quantified in the 3D FE model by 4 novel model-derived "auditory test curves", named as: the middle ear transfer function (METF), energy absorbance (EA), admittance tympanogram (AT), and TM holography, which will assist physicians and audiologists to interpret the diagnostic test results and identify the specific type of middle ear disorders. PUBLIC HEALTH RELEVANCE: Middle ear diseases often result in conductive hearing loss due to the changes of middle ear structure and soft tissue properties caused by the diseases. Understanding the relationship between the middle ear structural change and function of the middle ear will help diagnosis of different middle ear diseases. The proposed research project is to determine mechanical property changes in ear tissues associated with middle ear diseases and provide a computational model of the human ear to visualize and quantify structure-function relations in various diseases.