Doctor of Philosophy
Dr. Hanif Ladak
Finite-element (FE) modeling of the human middle ear could improve diagnostic techniques, such as tympanometry. Accurate representation of the mechanical properties and geometry of the middle ear, especially of the soft tissues, are crucial for FE modeling of the middle ear. The objective of this work is to quantitatively evaluate the efficacy of iodine potassium iodide (IKI) solution as a contrast agent for imaging the middle-ear soft tissues and to estimate the linear elastic properties of the human tympanic membrane (TM).
In the imaging study, six human temporal bones were used, which were obtained in right-left pairs, from three cadaveric heads. All bones were fixed using formaldehyde. Only one bone from each pair was stained using IKI solution. Samples were scanned using a micro-computed tomography system. Contrast-to-noise ratios of eight middle-ear soft tissues were calculated for each temporal bone. Results from Welch's t-test indicate significant difference between the two soft tissues group, i.e., stained and unstained, at a 95% confidence interval. Results from a paired t-tests for each of the individual soft tissues also indicated significant improvement of contrast in all tissues after staining. The increase in contrast with IKI solution confirms its potential application in sample-specific FE modeling.
In the linear elasticity study, experiments were performed on three specimens with a custom-built pressurization unit at a quasi-static pressure of 500 Pa. The shape of each TM before and after pressurization was recorded using a Fourier transform profilometer. The samples were also imaged using micro-CT to create sample-specific FE models. For each sample, the Young’s modulus was then estimated by numerically optimizing its value in the FE model so simulated pressurized shapes matched experimental data. Also, the effects of incorporating two forms of spatial non-uniformity in the distribution of Young’s modulus were studied, including partitioning the TM into 4 quadrants and 4 concentric rings. The estimated Young’s modulus values were 2.2 MPa, 2.4 MPa and 2.0 MPa, which are similar to recent literature values using an alternative method. An improved fit between simulated and experimental data were obtained when spatial non-uniformity was incorporated.
Rohani, Seyed Alireza, "Middle-Ear Imaging and Estimation of The Linear Elastic Properties of The Human Tympanic Membrane" (2016). Electronic Thesis and Dissertation Repository. 4264.
Available for download on Saturday, September 01, 2018