An investigation of cochlear dynamics in surgical and implanation processes

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The aim of this research is to improve the understanding of the impact on the cochlear dynamics corresponding to surgical tools, processes and hearing implants such that these can be designed more appropriately in the future. The results suggest that enhanced performance of implants can be achieved by optimisation of the location with respect to the cochlea and have shown that robotic surgical tools used to enable precise, simplified processes can reduce harm and offer other benefits. With an ageing population, and where exposure to noise on daily basis is increased rather than industrial settings, at least two factors of age and noise, will contribute to a greater incidence of hearing loss in the population in the future. In the research a mathematical model of the passive cochlea was produced to increase understanding of the sensitivity and behaviour of the fluid, structure and pressure transients within the cochlea. The investigation has been complemented by an innovative experimental technique developed to evaluate the dynamics in the cochlear fluids while maintaining the integrity of the cochlear structure. This technique builds on the success of the state-of-the-art surgical robotic micro-drill. The micro-drill enables removal of bone tissue to prepare a consistent aperture onto the endosteal membrane within the cochlea. This is known as preparing a ‘Third window’. In this technique the motion of the exposed endosteal membrane is treated as the diaphragm element of a pressure transducer and is measured using a Micro- Scanning Laser Vibrometer operating through a microscope. There are two principal outcomes of the research: First, the approach has enabled disturbances in the cochlea to be contrasted for different surgical techniques, which it is expected to allude preferential methods in future surgery in otology. In particular it was shown that when using the robotic micro-drill to create a cochleostomy that the disturbance amplitude reduces to 1% of that experienced when using conventional drilling. Secondly, an empirically derived frequency map of the cochlea has been produced to understand how the location of implants affects maximum power transmission over the required frequency band. This has also shown the feasibility of exciting the cochlea at a third window in order to amplify cochlear response

An international review of laser Doppler vibrometry:Making light work of vibration measurement

© 2016 In 1964, just a few years after the invention of the laser, a fluid velocity measurement based on the frequency shift of scattered light was made and the laser Doppler technique was born. This comprehensive review paper charts advances in the development and applications of laser Doppler vibrometry (LDV) since those first pioneering experiments. Consideration is first given to the challenges that continue to be posed by laser speckle. Scanning LDV is introduced and its significant influence in the field of experimental modal analysis described. Applications in structural health monitoring and MEMS serve to demonstrate LDV's applicability on structures of all sizes. Rotor vibrations and hearing are explored as examples of the classic applications. Applications in acoustics recognise the versatility of LDV as demonstrated by visualisation of sound fields. The paper concludes with thoughts on future developments, using examples of new multi-component and multi-channel instruments

Фізика з основами біофізики

The text-book "Physics with Fundamentals of Biophysics" published in English is intended for the students who attend the English-speaking lectures in educational institutions of Ukraine; it can be useful for the foreign students and post-graduate students, translators and everybody who is interested in English terminology in the field of physics and biophysics. The main objectives of the course “Physics with Fundamentals of Biophysics” is to expose principal laws and theses of physics which make it possible to study general regularities of natural phenomena; to apply the principles and methods of the physical sciences to biological problems; to consider the biophysical problems which are concerned with the viability of living objects (plants, animals, microorganisms) and their interaction with the environment; to elucidate possible application of physical instrumentation to agricultural, biological, ecological, and medical practice. The text-book is supplied with the examples of solutions of practical biophysical problems, control questions pertaining to those problems that require clarification. Rating system of estimation of students´ level of knowledge is offered also. Each text modulus contains the vocabulary of physical and biophysical terms. The informative material is given in appendix.Даний підручник виданий англійською мовою, призначений саме для підготовки студентів, що слухають лекції англійською мовою в навчальних закладах ІІІ-IV рівнів акредитації України. Він може бути корисним для іноземних студентів та аспірантів, перекладачів та всіх, хто цікавиться англомовною термінологією в галузі фізики та біофізики. Основна мета підручника - навести основні положення, закони та теорії з курсу загальної фізики; розглянути фізичні процеси та механізми, що складають основу життєдіяльності живих організмів – рослин, тварин, мікроорганізмів; викласти проблеми впливу зовнішніх фізичних факторів на живі організми та їх здатності реагувати на ці фактори; висвітлити принципи дії та можливі застосування сучасних фізичних методів та приладів у сільськогосподарській, біологічній, екологічній та медичній практиці. Підручник містить приклади розв’язання практичних біофізичних проблем, контрольні завдання для перевірки засвоєння матеріалу студентами та запитання, відповіді на які студенти зможуть дати у разі ознайомлення із відповідними розділами підручника. Для оцінки знань студентів пропонується рейтингова система. Кожний змістовний модуль має словник фізичних та біофізичних термінів. Інформативний матеріал представлений у додатку

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

Experimental Study of Nonlinearity and Amplification in the Mammalian Cochlea

The mammalian hearing organ, the cochlea, has a marvelous sensitivity and frequency resolution. Due to passive mechanical properties (e.g. mass, stiffness, damping), sound-induced traveling waves are formed on the basilar membrane (BM), which are longitudinally tuned to different frequencies. In a live cochlea, a phenomenon called cochlear amplification, derived from the mechano-electric transduction of the outer hair cells (OHCs), locally enhances the traveling wave and increases the frequency selectivity. My research during the PhD program was focused on studying the in-vivo mechanical and electrophysiological responses of the cochlea in animal models.In the first set of experiments, the intra-cochlear motion and the OHC-generated local cochlear microphonic (LCM) responses were measured in the base of the gerbil cochlea. We used optical coherence tomography (OCT) to measure the intra-cochlear motion and a tungsten micro-electrode to obtain the LCM responses. We explored the effect of the two types of sound stimuli, single and multi-tone stimuli, to the nonlinear behavior of the LCM and the intra-cochlear motion responses in two frequency bands: a frequency band in which cochlear responses show a nonlinear peak (the best frequency (BF) band) and a frequency range below the large peak (sub-BF band: f < ∼ 0.7 × BF). In the sub-BF band, BM motion had linear growth for both stimulus types, and the motion in the OHC region was mildly nonlinear for single tones, and relatively strongly nonlinear for multi-tones. Sub-BF, the nonlinear character of the LCM was similar to that of the OHC- region motion. In the BF band, the LCM and the intra-cochlear motions all possessed the BF peak nonlinearity. Coupling these observations with previous findings on phasing between OHC force and traveling wave motions, we proposed the following framework for cochlear nonlinearity: The BF-band nonlinearity is an amplifying nonlinearity, in which OHC forces input power into the traveling wave, allowing it to travel further apical to the region where it peaks. The sub-BF nonlinearity is a non- amplifying nonlinearity; it represents OHC electromotility, and saturates due to OHC current saturation, but the OHC forces do not possess the proper phasing to feed power into the traveling wave. In the second set of experiments, we repeated the cochlear measurements as in the first project in the base of guinea pig cochlea. The goal was to compare the degree of nonlinearity and amplification in the LCM and intra-cochlear responses between gerbil and guinea pig. The experimental condition and method were similar to the gerbil study. In the BF band, our observations were similar to our previous measurements in gerbil: a nonlinear peak in LCM responses and in intra- cochlear displacements, and higher motion in the OHC region than the BM. Sub-BF, the responses in the two species were different. In both species the BM motion responses in the sub-BF band was linear and LCM was nonlinear. Sub-BF in the OHC-region, nonlinearity was only observed in a subset of healthy guinea pig cochleae while in gerbil, robust nonlinearity was observed in all healthy cochleae. The differences suggest that gerbils and guinea pigs may employ different mech- anisms for to achieve frequency selectivity. However, it cannot be ruled out that the differences are due to technical measurement differences across the species

Investigation of cochlear disturbance induced during surgical intervention

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonHearing loss is a common impairment or disability for human beings, and is impacting an increasing amount of people, augmented by the growing aging population around the globe. Cochlear implantation, as one of the most effective ways to restore hearing, can only applied to profoundly deaf patients at the moment. In order to expand the group of people who can benefit from cochlear implantation to those with less severe hearing loss, endeavours need to be made to best preserve residual hearing and minimise trauma induced during cochlear implantation surgery. In this thesis, the disturbance induced in the cochlea, i.e. the acoustic and mechanical energy transmitted into the cochlea, during cochleostomy drilling is studied – as well as establishing a comparison between a manually guided conventional technique and a manually supported tissue guided robotic drilling technique. The results show that by changing surgical techniques and how they are applied can have a significant impact on levels of disturbance induced – robotic-aided approach induced lower level of equivalent SPL for up to 86% of the time and can be as much as 39 dB lower than that generated by conventional surgical drilling. This work is timely because trauma is an important consideration to clinicians and health care providers. Cochleostomy is one of the major and most disruptive surgical process during cochlear implantation. With the increasing amount of cochlear implant electrode array designs that are shorter and less intrusive, and the increasing demand of electric-acoustic stimulation via cochlear implant to better resemble the human auditory system, the approach to reduce disruption during cochleostomy drilling is highly relevant to the progression in the hearing care industry and the benefits of the growing hearing impairment community.Queen Elizabeth Hospital Birmingham Charit

Cell Compatible Electrospun Poly(vinyl alcohol) Fibers for Tissue Regeneration

Poly(vinyl alcohol) (PVA) is a well known biocompatible synthetic polymer. PVA is not cell compatible due to its high hydrophilicity. As prepared by electrospinning in the form of nanofibers, it is unstable in aqueous environments including cell culture media. For tissue regeneration applications, this study demonstrates the use of PVA scaffold utilizing electrospun nanofibers with aqueous stability and cell compatibility toward creating biomaterial-tissue hybrid based medical devices. Two different approaches: heat treatment and ion beam treatment were developed to improve aqueous stability and promote cell compatibility for PVA fibers. Using a thermal annealing method at elevated temperatures, the fibers became stable in water. This observation correlated closely to the change in the crystallinity of PVA. Elastic moduli of individual fibers were determined using a multi-points bending approach by atomic force microscopy. Elastic moduli of as-spun PVA fibers were determined to be a function of fiber diameter and humidity. Significant changes in the elastic modulus of the modified PVA fibers were also observed. To improve the cell compatibility, low energy N+ and He+ ion beams were used to introduce amine and carbonyl functional groups. Cell compatibility was assessed in vitro using primary human skin fibroblasts (hsF). Confocal microscopy confirmed the adhesion and proliferation of hsF on both the random and aligned PVA fibers after the ion beam treatment, while cells failed to adhere to the untreated fibers. Cell morphology was observed to align and elongate along the fiber axis on aligned PVA fibers. After 10 days of proliferation, cells were found to form confluent layers and even multiple layers on the N+treated fibers. Cell proliferation depends on ion species, ion dose and fiber alignment. With the two post-processing treatments, PVA fibrous scaffold showed the potential to become biomaterial-tissue hybrid based medical devices for tissue regeneration applications

Ultrastructural analysis of odontocete cochlea

The morphological study of the Odontocete organ of Corti including possible pathological features resulting from sound over-exposure, represent a key conservation issue to assess the effects of acoustic pollution on marine ecosystems. Through the collaboration with stranding networks belonging to 26 countries, 150 ears from 13 species of Odontocetes were processed. In this dissertation, we present a standard protocol to 1) compare the ultrastructure of the cochlea in several Odontocete species and 2) investigate possible damage as a consequence of sound exposure, using scanning (SEM) and transmission (TEM) electron microscopy, and immunohistochemistry. In a preliminary study, computerized tomography scans were performed before decalcification with ears of 15 odontocete species, proposing a set of standard measurements which classified very well the species. In addition, the constant ratio between measurements of inner and middle ear structures contributed to confirm the active role of the odontocete middle ear in sound reception mechanism. We established a decalcification protocol using the fast commercial decalcifier RDO® and EDTA (Ethylendiaminetetraacetic acid). Although further experiments should be conducted to assess the suitability of using one or the other method (because the number of samples treated with EDTA was comparatively small), RDO® at specific dilutions decreased the decalcification time of cetacean ear bones with control of the decalcification endpoint, helping a faster access to inner structures. The complementary use of electron microscopy and immunofluorescence allowed the description in odontocetes of new morphological features of tectorial membrane, spiral limbus, spiral ligament, stria vascularis, hair cells and their innervation. Furthermore, this study revealed qualitative and quantitative morphological characteristics of the organ of Corti in high-frequency hearing species, including 1) an outer hair cell (OHC) small length, 2) a thick cuticular plate in OHC, and a thick reticular lamina, 3) robust cup formation of the Deiters cell body, 4) the high development of cytoskeleton in Deiters and pillar cells and 5) the basilar membrane high stiffness. Interestingly, all these features, including a common molecular design of prestin, are also shared by echolocating bats, suggesting a convergent evolution in echolocating species. The presence of scars among hair cell rows, the pattern of stereocilia imprints in the tectorial membrane and the condition of fibrocytes II and IV were criteria suitable to determine or discard possible acoustic trauma, despite the numerous artefacts that rapidly develop as a consequence of tissue autolysis. Consequently, matching the preliminary approximation of the cochlear frequency map with the damaged region would bring information on the sound source that would have triggered a possible lesion.Postprint (published version

Measuring nanometer, three-dimensional motions with light microscopy

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 173-182).by Charles Quentin Davis.Ph.D