The Human Middle Ear - A Multidisciplinary Study by means of Tomographic Imaging, Stroboscopic Holography and Dynamic Finite Element Modeling

Date: 31 January 2017

Venue: UAntwerpen, Campus Middelheim, G0.10 - Middelheimlaan 1 - 2020 Antwerpen (route: UAntwerpen, Campus Middelheim)

Time: 4:00 PM

Organization / co-organization: Department of Physics

PhD candidate: Daniël De Greef

Principal investigator: Joris Dirckx

Short description: PhD defence Daniël De Greef - Faculty of Science, Department of Physics



Abstract

The human middle ear is a complex mechanical system that is yet fully understood in all its aspects. Nevertheless, this fundamental knowledge is necessary to improve the treatment of middle ear related instances of hearing loss. In this doctoral thesis, multiple steps have been taken towards a better insight into the mechanics of the human middle ear. The main goal of this thesis was to develop a numerical model of the middle ear that exhibits realistic behaviour in response to incoming sound waves.

In the first part of this thesis, an optical measurement technique called stroboscopic digital holography was is described. It was developed to map vibrational patterns of the eardrum. The fullfield vibrational maps, that could be recorded using our setup and software, gave insight into the intrinsic damping properties of the eardrum, among other things. These properties were important input parameters for the numerical model of the middle ear that was developed in this thesis.

Part two focuses on multiple morphologic properties of the human middle ear, studied mainly through high-resolution CT (computed tomography). Many of these properties have an important effect on the mechanics of the middle ear, either in healthy or in unhealthy condition.

The third part of the thesis deals directly with the mechanics of the middle ear system. In these chapters, finite element models of the middle ear were constructed and compared to multiple experimental observations (among which those obtained using the technique from part 1 of this thesis). Three models were developed, based on the geometry of three different donor ears, all of which exhibited realistic vibrational behaviour, after optimization of the material parameters. Subsequently, these three models were utilized to improve our understanding of hearing loss in case of a fracture in the first ossicle bone, the hammer. The final chapter of the thesis describes a study on the passive role of the eardrum for slow, quasi-static external pressure changes, an effect that is called the buffer capacity of the eardrum.

As a final product of this thesis, we now possess three numerical models of the middle ear, each of which are a realistic representation of healthy middle ears and can be used to improve our understanding of some unhealthy conditions and possible treatments for those conditions.



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