Effects of the fibers distribution in the human eardrum: A biomechanical study

The eardrum separates the external ear from the middle ear and it is responsible to convert the acoustical energy into mechanical energy. It is divided by pars tensa and pars flaccida. The aim of this work is to analyze the susceptibility of the four quadrants of the pars tensa under negative pressure, to different lamina propria fibers distribution. The development of associated ear pathology, in particular the formation of retraction pockets, is also evaluated. To analyze these effects, a computational biomechanical model of the tympano-ossicular chain was constructed using computerized tomography images and based on the finite element method. Three fibers distributions in the eardrum middle layer were compared: case 1 (eardrum with a circular band of fibers surrounding all quadrants equally), case 2 (eardrum with a circular band of fibers that decreases in thickness in posterior quadrants), case 3 (eardrum without circular fibers in the posterior/superior quadrant). A static analysis was performed by applying approximately 3000Pa in the eardrum. The pars tensa of the eardrum was divided in four quadrants and the displacement of a central point of each quadrant analyzed. The largest displacements of the eardrum were obtained for the eardrum without circular fibers in the posterior/superior quadrant

Evaluating fidelity of CT based 3D models for Zebrafish conductive hearing system

The zebrafish Weberian apparatus is an emerging model for human conductive hearing system. Their Weberian apparatus comprises minute bones and ligamentary links, and conducts sound pressure transmission from the gas bladder to inner ear through four pairs of Weberian ossicles along the vertebral column. We herein present a methodological study using MicroCT to image the Weberian apparatus for biomechanical and morphological analysis. The aim of this work is to evaluate computational models generated from multiple MicroCT scans with different parameters, to identify the most feasible scan combination for practical (minimized scan time) yet accurate (relative to highest resolution) biomechanical simulations. We segmented and created 3D models from CT scan image stacks at 4.64 μm, 5.05 μm, 9.30 μm and 13.08 μm voxel resolutions, respectively. Then, we used geometric morphometrics analysis to quantify inter-model shape differences, as well as a series of finite element modal and harmonic analyses to simulate auditory signal vibrations. Relative to the highest resolution and most accurate model, the Model 9.30 is closest in overall geometry and biomechanical behavior of all lower resolution models. The differences in resolution and quality of the CT substantially affect the segmentation and reconstruction process of the three-dimensional model of the ossicles, and the subsequent analyses. We conclude that scan voxel resolution is a key factor influencing outcomes of biomechanical simulations of delicate and minute structures, especially when studying the harmonic response of minute ossicles connected by ligaments using finite element modeling. Furthermore, contrast variations in CT images as determined by x-ray power and scan speed, also affect fidelity in 3D models and simulation outcomes

Development of Mathematical Models of a Human Virtual Ear

L’orecchio umano è un complesso sistema biomeccanico deputato alla ricezione e percezione del suono. Il presente lavoro di tesi verte sull’analisi delle parti esterna o media. Sono introdotti alcuni cenni di anatomia dell’orecchio esterno e medio ed una indagine di letteratura rivolta alla modellazione. È stato sviluppato un modello ad elementi finiti standard e generalizzati del canale uditivo e della membrana timpanica, a seguito di un approfondito confronto tra modelli di letteratura della membrana timpanica. Per la catena ossiculare, comprensiva di giunti, legamenti e tendini muscolari che la supportano, è stato adottato un approccio di tipo multibody. Il modello ad elementi finiti della membrana timpanica è stato combinato con il modello multibody della catena ossiculare al fine di ottenere un modello ibrido dell’orecchio medio. L’elaborazione dell’informazione nel sistema uditivo è un tema centrale della psicoacustica, una branca dell’acustica concernente la correlazione quantitativa delle grandezze fisiche e della percezione del suono. Un approccio psicoacustico è stato applicato in un’attività sperimentale e teorica per la valutazione del rumore da alzacristalli elettrici, nell’ambito di un progetto in collaborazione con un’azienda del territorio. The present thesis mainly focuses on the outer and middle parts of the human ear, which is a complex biomechanical system, devoted to sound reception and perception. The anatomy in brief and a model-oriented review of outer and middle ear are introduced. A model including the auditory canal and the tympanic membrane was developed applying standard and generalized finite element methods, following a thorough comparison between literature finite element models of the tympanic membrane. The multibody approach was adopted for the ossicular chain and supporting structures (joints, ligaments and muscle tendons). The tympanic membrane finite element model and the ossicular chain multibody model were combined in a hybrid finite element-multibody model of the middle ear. The information processing in the auditory system is a central issue of the psychoacoustics, a branch of acoustics concerning the quantitative correlation between the physical characteristics of sounds and their perceptual attributes. The psychoacoustic approach was applied in an experimental and theoretical activity on power window noise evaluation, within a project in collaboration with a local enterprise

Segmentation algorithms for ear image data towards biomechanical studies

In recent years, the segmentation, i.e. the identification, of ear structures in video-otoscopy, computerised tomography (CT) and magnetic resonance (MR) image data, has gained significant importance in the medical imaging area, particularly those in CT and MR imaging. Segmentation is the fundamental step of any automated technique for supporting the medical diagnosis and, in particular, in biomechanics studies, for building realistic geometric models of ear structures. In this paper, a review of the algorithms used in ear segmentation is presented. The review includes an introduction to the usually biomechanical modelling approaches and also to the common imaging modalities. Afterwards, several segmentation algorithms for ear image data are described, and their specificities and difficulties as well as their advantages and disadvantages are identified and analysed using experimental examples. Finally, the conclusions are presented as well as a discussion about possible trends for future research concerning the ear segmentation.info:eu-repo/semantics/publishedVersio

Modeling and Measurement of Sound Transmission in the Baboon Ear

While many animal models exist for middle ear research, the progression of knowledge is hindered by the impossibility of in vivo investigation in cadavers and the great physiological differences of the distantly related species of current animal models. Pediatric and age-related auditory research could be particularly valuable in the effort toward alleviating the enormous fiscal burdens of both middle ear infections in young children and hearing loss in both the young and elderly communities. The goal of this thesis is to provide steps toward the first nonhuman primate model for auditory research and begin the foundation for the role age plays in sound transmission through the primate ear. Micro-Computed tomography images were used to digitally reconstruct three-dimensional models of one adult and one newborn baboon middle ear, and dimensions were gathered for key tissue components. The adult elliptical tympanic membrane is 0.77 mm greater along the major axis than in the newborn baboon, while it is 0.61 mm smaller along the minor axis, 0.56 mm less deep in conic shape, and ~ 15 µm thinner. The adult ear canal opening was 0.84 mm larger in height and 0.38 mm larger in width. While the adult middle ear cavity was 1.56 mm greater in height, it was also 2.79 mm smaller in the anterior-posterior direction of the skull. Orientation of the ossicles within the middle ear cavity also differed between the adult and newborn baboon ears; the newborn TM was 31.3° more angled from horizontal and the newborn stapes was 14.4° less angled from horizontal. Next, finite element method was employed to analyze the fluid and structural dynamics of sound transmission through the ear canal at different frequencies. Finally, displacement at the umbo of the tympanic membrane was found using the FE model and validated using laser Doppler vibrometry experimental data for old (N=6) and young (N=6) baboon age groups. Treating the experimental mean as the accepted value and the FE results as the results to be compared, this gives a percent error of 21.7% at 200 Hz, 12.5% at 1200 Hz, and 24% at 10000 Hz for the newborn model and 30.7% at 200 Hz, 28.5% at 1200 Hz, and 105% at 10000 Hz for the adult model. Displacement values at very high frequencies deviated most from the experimental mean, and overall the shape of the FE curve is similar to that of the experimental curve. Possible limitations of these analyses include: 1) Each FE model was based on one temporal bone, each coming from a different sex; 2) Because no baboon research exists, human mechanical property values were used for analysis. While the FE models seem to be good representations of their corresponding age groups, further improvements can be made. Based on these preliminary results, age does seem to play an impact in sound transmission for baboons, with TM mobility increasing with age

Computer-integrated finite element modeling and simulation of human middle ear.

The work reported in this dissertation is the result of a joint venture of biomedical scientists and engineers for understanding human middle ear mechanics through finite element modeling and analysis. The main objective of the research is to explore the middle ear dynamics by using an accurate finite element model of the human middle ear.The base-line finite element model was employed for three preliminary clinical applications. The results suggest that the base-line finite element model is very useful in the study of the middle ear mechanics, and the design and test of implantable hearing devices.The research started with developing a systematic and accurate geometric modeling method that can be employed to reconstruct the middle ear from the histological sections of a human temporal bone in the Computer-Aided Design (CAD) environment. Using the method, a solid model of human middle ear was constructed which reveals excellent accuracy in geometry.Then a finite element model of the human middle ear was built by using the geometry translated from the CAD model and the published material properties of the middle ear system. The finite element model was finalized as the base-line finite element model by adjusting physical parameters based on the stapes footplate displacements obtained by laser Doppler interferometry measurements. Finally, the accuracy of the base-line finite element model was verified by using four sets of published experimental measurements. These verifications demonstrate that the base-line model constructed using the geometric modeling method developed in this research is adequate in predicting the dynamic behaviors of the middle ear. Therefore, it is appropriate to employ the finite element model to simulate the middle ear frequency response characteristics, which are the main concerns in the middle ear sound transmission study

Development of an optoelectronic holographic otoscope system for characterization of sound-induced displacements in tympanic membranes

The conventional methods for diagnosing pathological conditions of the tympanic membrane (TM) and other abnormalities require measuring its motion while responding to acoustic excitation. Current methodologies for characterizing the motion of the TM are usually limited to either average acoustic estimates (admittance or reflectance) or single-point mobility measurements, neither of which is sufficient to characterize the detailed mechanical response of the TM to sound. Furthermore, while acoustic and single-point measurements are useful for the diagnosis of some middle ear disorders, they are not useful in others. Measurements of the motion of the entire TM surface can provide more information than these other techniques and may be superior for the diagnosis of pathology. In this Thesis, the development of an optoelectronic holographic otoscope (OEHO) system for characterization of nanometer scale motions in TMs is presented. The OEHO system can provide full-field-of-view information of the sound-induced displacements of the entire surface of the TM at video rates, allowing rapid quantitative analysis of the mechanical response of normal or pathological TMs. Preliminary measurements of TM motion in cadaveric animals helped constrain the optical design parameters for the OEHO, including the following: image contrast, resolution, depth of field (DOF), laser power, working distance between the interferometer and TM, magnification, and field of view (FOV). Specialized imaging software was used in selecting and synthesizing the various components. Several prototypes were constructed and characterized. The present configuration has a resolution of 57.0 line pairs/mm, DOF of 5 mm, FOV of 10 ´ 10 mm2, and a 473 nm laser with illumination power of 15 mW. The OEHO system includes a computer controlled digital camera, a fiber optic subsystem for transmission and modulation of laser light, and an optomechanical system for illumination and observation of the TM. The OEHO system is capable of operating in two modes. A \u27time-averaged\u27 mode, processed at video rates, was used to characterize the frequency dependence of TM displacements as tone frequency was swept from 500 Hz to 25 kHz. A \u27double-exposure\u27 mode was used at selected frequencies to measure, in full-field-of-view, displacements of the TM surface with nanometer resolution. The OEHO system has been designed, fabricated, and evaluated, and is currently being evaluated in a medical-research environment to address basic science questions regarding TM function. Representative time-averaged holographic and stroboscopic interferometry results in post-mortem and live samples are herein shown, and the potential utilization discussed