The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Joris J.j. Dirckx - One of the best experts on this subject based on the ideXlab platform.
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Eardrum displacement and strain in the Tokay gecko (Gekko gecko) under quasi-static pressure loads.
Hearing Research, 2020Co-Authors: Pieter Livens, Kilian Gladine, Joris J.j. DirckxAbstract:Abstract The Eardrum is the primary component of the middle ear and has been extensively investigated in humans. Measuring the displacement and deformation of the Eardrum under different quasi-static loading conditions gives insight in its mechanical behavior and is fundamental in determining the material properties of the Eardrum. Currently, little is known about the behavior and material properties of Eardrums in non-mammals. To explore the mechanical properties of the Eardrum in non-mammalian ears, we investigated the quasi-static response of the Eardrum of a common lizard: the Tokay gecko (Gekko gecko). The middle ear cavity was pressurized using repetitive linear pressure cycles ranging from −1.5 to 1.5 kPa with pressure change rates of 0.05, 0.1 and 0.2 kPa/s. The resulting shape, displacement and in-plane strain of the Eardrum surface were measured using 3D digital image correlation. When middle-ear pressure is negative, the medial displacement of the Eardrum is much larger than the displacement observed in mammals; when middle-ear pressure is positive, the lateral displacement is much larger than in mammals, which is not observed in bird single-ossicle ears. Peak-to-peak displacements are about 2.8 mm, which is larger than in any other species measured up to date. The peak-to-peak displacements are at least five times larger than observed in mammals. The pressure-displacement curves show hysteresis, and the energy loss within one pressure cycle increases with increasing pressure rate, contrary to what is observed in rabbit Eardrums. The energy lost during a pressure cycle is not constant over the Eardrum. Most energy is lost at the region where the Eardrum connects to the hearing ossicle. Around this Eardrum-ossicle region, a 5% increase in energy loss was observed when pressure change rate was increased from 0.05 kPa/s to 0.2 kPa/s. Other parts of the Eardrum showed little increase in the energy loss. The orientation of the in-plane strain on the Eardrum was mainly circumferential with strain amplitudes of about +1.5%. The periphery of the measured Eardrum surface showed compression instead of stretching and had a different strain orientation. The TM of Gekko gecko shows the highest displacements of all species measured up till now. Our data show the first shape, displacement and deformation measurements on the surface of the Eardrum of the gecko and indicate that there could exist a different hysteresis behavior in different species.
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strain distribution in rabbit Eardrums under static pressure
Hearing Research, 2019Co-Authors: Kilian Gladine, Joris J.j. DirckxAbstract:Abstract Full-field strain maps of intact rabbit Eardrums subjected to static pressures are presented. A stochastic intensity pattern was applied to 12 Eardrums, and strain maps were measured at the medial site using a stereoscopic digital image correlation setup for pressures between −2 and 2 kPa. Ear canal overpressures induced circumferential orientated positive strains between manubrium and the Eardrum border that increased almost linearly with pressure. Radially orientated negative strains were found at the border and manubrium. Ear canal underpressures caused negative circumferential strains between manubrium and the tympanic annulus but radially orientated positive strains at the borders. The magnitudes of these negative strains at underpressures were larger than those of positive strains at overpressures and were nonlinearly proportional to pressure. In three ears, strains were calculated with intact and removed cochlea. The effect of cochlea removal on the peak-to-peak strain was found to be no more than 3%.
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How flexibility and Eardrum cone shape affect sound conduction in single-ossicle ears: a dynamic model study of the chicken middle ear
Biomechanics and Modeling in Mechanobiology, 2019Co-Authors: Pieter G.g. Muyshondt, Joris J.j. DirckxAbstract:It is believed that non-mammals have poor hearing at high frequencies because the sound-conduction performance of their single-ossicle middle ears declines above a certain frequency. To better understand this behavior, a dynamic three-dimensional finite-element model of the chicken middle ear was constructed. The effect of changing the flexibility of the cartilaginous extracolumella on middle-ear sound conduction was simulated from 0.125 to 8 kHz, and the influence of the outward-bulging cone shape of the Eardrum was studied by altering the depth and orientation of the Eardrum cone in the model. It was found that extracolumella flexibility increases the middle-ear pressure gain at low frequencies due to an enhancement of Eardrum motion, but it decreases the pressure gain at high frequencies as the bony columella becomes more resistant to extracolumella movement. Similar to the inward-pointing cone shape of the mammalian Eardrum, it was shown that the outward-pointing cone shape of the chicken Eardrum enhances the middle-ear pressure gain compared to a flat Eardrum shape. When the outward-pointing Eardrum was replaced by an inward-pointing Eardrum, the pressure gain decreased slightly over the entire frequency range. This decrease was assigned to an increase in bending behavior of the extracolumella and a reduction in piston-like columella motion in the model with an inward-pointing Eardrum. Possibly, the single-ossicle middle ear of birds favors an outward-pointing Eardrum over an inward-pointing one as it preserves a straight angle between the columella and extrastapedius and a right angle between the columella and suprastapedius, which provides the optimal transmission.
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Real-time structured light-based otoscopy for quantitative measurement of Eardrum deformation.
Journal of Biomedical Optics, 2017Co-Authors: Sam Van Der Jeught, Joris J.j. DirckxAbstract:An otological profilometry device based on real-time structured light triangulation is presented. A clinical otoscope head is mounted onto a custom-handheld unit containing both a small digital light projector and a high-speed digital camera. Digital fringe patterns are projected onto the Eardrum surface and are recorded at a rate of 120 unique frames per second. The relative angle between projection and camera axes causes the projected patterns to appear deformed by the Eardrum shape, allowing its full-field three-dimensional (3-D) surface map to be reconstructed. By combining hardware triggering between projector and camera with a dedicated parallel processing pipeline, the proposed system is capable of acquiring a live stream of point clouds of over 300,000 data points per frame at a rate of 40 Hz. Real-time Eardrum profilometry adds an additional dimension of depth to the standard two-dimensional otoscopy image and provides a noninvasive tool to enhance the qualitative depth perception of the clinical operator with quantitative 3-D data. Visualization of the Eardrum from different perspectives can improve the diagnosis of existing and the detection of impending middle ear pathology. The capability of the device to detect small middle ear pressure changes by monitoring Eardrum deformation in real time is demonstrated.
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Effect of middle ear components on Eardrum quasi-static deformation
Hearing Research, 2001Co-Authors: Joris J.j. Dirckx, Willem F. DecraemerAbstract:Eardrum deformation induced by quasi-static middle ear pressure was studied at progressive stages of dissection of gerbil temporal bones. With our high resolution moire interferometer we recorded the shape and deformation of the Eardrum along a line perpendicular to the manubrium and through the umbo, at different middle ear pressures. The deformation was measured from the medial side, after serially removing the cochlea, removing the stapes, cutting the tensor tympani, exposing the incudo-mallear joint, and cutting the anterior bony process which connects the malleus to the tympanic bone. The mean displacement as a function of pressure was also determined at all stages of dissection. Removing the cochlea and stapes, and cutting tensor tympani has no effect on static Eardrum deformation. Exposing the incudo-mallear joint increases Eardrum movement, and cutting the anterior bony connection between malleus and temporal bone strongly changes Eardrum rest position and further increases its displacement.
Hanif M. Ladak - One of the best experts on this subject based on the ideXlab platform.
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Estimation of the quasi-static Young's modulus of the Eardrum using a pressurization technique
Computer Methods and Programs in Biomedicine, 2013Co-Authors: Nastaran Ghadarghadar, Sumit K. Agrawal, Abbas Samani, Hanif M. LadakAbstract:The quasi-static Young's modulus of the Eardrum's pars tensa is an important modeling parameter in computer simulations. Recent developments in indentation testing and inverse modeling allow estimation of this parameter with the Eardrum in situ. These approaches are challenging because of the curved shape of the pars tensa which requires special care during experimentation to keep the indenter perpendicular to the local surface at the point of contact. Moreover, they involve complicated contact modeling. An alternative computer-based method is presented here in which pressurization is used instead of indentation. The Young's modulus of a thin-shell model of the Eardrum with subject-specific geometry is numerically optimized such that simulated pressurized shapes match measured counterparts. The technique was evaluated on six healthy rat Eardrums, resulting in a Young's modulus estimate of 22.8?1.5MPa. This is comparable to values estimated using indentation testing. The new pressurization-based approach is simpler to use than the indentation-based method for the two reasons noted above.
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Measuring the quasi-static Young’s modulus of the Eardrum using an indentation technique
Hearing Research, 2010Co-Authors: S. Mohammad Hesabgar, Sumit K. Agrawal, Abbas Samani, Harry R. Marshall, Hanif M. LadakAbstract:Accurate estimation of the quasi-static Young's modulus of the Eardrum is important for finite-element modeling. In this study, we adapted a tissue indentation technique and inverse finite-element analysis to estimate the Young's modulus of the Eardrum. A custom-built indentation apparatus was used to perform indentation testing on seven rat Eardrums in situ after immobilizing the malleus. Testing was done in most cases on the posterior pars tensa. The unloaded shape of each Eardrum was measured and used to construct finite-element models with subject-specific geometries to simulate the indentation experiment. The Young's modulus of each specimen was then estimated by numerically optimizing the Young's modulus of each model so that simulation results matched corresponding experimental data. Using an estimated value of 12 microm for the thickness of each model Eardrum, the estimated average Young's modulus for the pars tensa was found to be 21.7+/-1.2 MPa. The estimated average Young's modulus is within the range reported in some of the literature. The estimation technique is sensitive to the thickness of the pars tensa used in the model but is not sensitive to relatively large variations in the stiffness of the pars flaccida and manubrium or to the pars tensa/pars flaccida separation conditions.
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Measuring the quasi-static Young's modulus of the Eardrum using an indentation technique.
Hearing Research, 2010Co-Authors: S. Mohammad Hesabgar, Sumit K. Agrawal, Abbas Samani, Harry Marshall, Hanif M. LadakAbstract:Accurate estimation of the quasi-static Young's modulus of the Eardrum is important for finite-element modeling. In this study, we adapted a tissue indentation technique and inverse finite-element analysis to estimate the Young's modulus of the Eardrum. A custom-built indentation apparatus was used to perform indentation testing on seven rat Eardrums in situ after immobilizing the malleus. Testing was done in most cases on the posterior pars tensa. The unloaded shape of each Eardrum was measured and used to construct finite-element models with subject-specific geometries to simulate the indentation experiment. The Young's modulus of each specimen was then estimated by numerically optimizing the Young's modulus of each model so that simulation results matched corresponding experimental data. Using an estimated value of 12 microm for the thickness of each model Eardrum, the estimated average Young's modulus for the pars tensa was found to be 21.7+/-1.2 MPa. The estimated average Young's modulus is within the range reported in some of the literature. The estimation technique is sensitive to the thickness of the pars tensa used in the model but is not sensitive to relatively large variations in the stiffness of the pars flaccida and manubrium or to the pars tensa/pars flaccida separation conditions.
K. Begall - One of the best experts on this subject based on the ideXlab platform.
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Observation of Eardrum movements during quasi-static pressure changes by high-speed digital imaging.
Audiology & neuro-otology, 1999Co-Authors: Ulrich Vorwerk, Gunnar Steinicke, K. BegallAbstract:Under specific quasi-static pressure conditions during the Valsalva manoeuvre, high-speed digital video pictures of Eardrum displacements were recorded using an endoscope and a Kodak Image Ektapro 1000 Motion Analyzer. A new type of data interface enabled the complete videoclip to be saved and processed digitally, and, with special mathematical algorithms, it is possible to generate three-dimensional computer animations of Eardrum movements under quasi-static pressure. The present study describes patterns of Eardrum movements under static pressure changes (Valsalva manoeuvre). These patterns were consistent with the results of finite-element simulations of highly similar Eardrum displacements reported by other workers.
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High-Speed Digital Videoimaging of Fast Eardrum Motions During Valsalva Maneuver
ORL, 1998Co-Authors: Ulrich Vorwerk, Matthias Hey, Gunnar Steinicke, K. BegallAbstract:Digital high-speed camera systems are used to record high-frequency videoclips. After adapting this technology to the analysis of Eardrum motions, fast motions of the Eardrum can be recorded using an
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High-Speed Digital Videoimaging of Fast Eardrum Motions During Valsalva Maneuver
ORL; journal for oto-rhino-laryngology and its related specialties, 1998Co-Authors: Ulrich Vorwerk, Matthias Hey, Gunnar Steinicke, K. BegallAbstract:Digital high-speed camera systems are used to record high-frequency video-clips. After adapting this technology to the analysis of Eardrum motions, fast motions of the Eardrum can be recorded using an endoscope. Under specific static pressure conditions during the Valsalva maneuver, recordings of Eardrum motions were made. The use of a Kodak Image Ektapro 1000 Motion Analyzer allowed only conventional videosignal processing and storage. A new type of data interface made it possible to save and process the complete video-clip digitally. Using an image-processing workstation and special mathematical algorithms, three-dimensional computer animations of fast Eardrum motions under static pressure can be generated. In the present study, several animations of fast Eardrum movements are described. High-speed digital videoimaging is an adequate method to describe fast Eardrum displacements under static pressure (Valsalva maneuver). It is possible to create visible timeshift images of separate Eardrum parts during the fast Valsalva maneuver.
Ulrich Vorwerk - One of the best experts on this subject based on the ideXlab platform.
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Observation of Eardrum movements during quasi-static pressure changes by high-speed digital imaging.
Audiology & neuro-otology, 1999Co-Authors: Ulrich Vorwerk, Gunnar Steinicke, K. BegallAbstract:Under specific quasi-static pressure conditions during the Valsalva manoeuvre, high-speed digital video pictures of Eardrum displacements were recorded using an endoscope and a Kodak Image Ektapro 1000 Motion Analyzer. A new type of data interface enabled the complete videoclip to be saved and processed digitally, and, with special mathematical algorithms, it is possible to generate three-dimensional computer animations of Eardrum movements under quasi-static pressure. The present study describes patterns of Eardrum movements under static pressure changes (Valsalva manoeuvre). These patterns were consistent with the results of finite-element simulations of highly similar Eardrum displacements reported by other workers.
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High-Speed Digital Videoimaging of Fast Eardrum Motions During Valsalva Maneuver
ORL, 1998Co-Authors: Ulrich Vorwerk, Matthias Hey, Gunnar Steinicke, K. BegallAbstract:Digital high-speed camera systems are used to record high-frequency videoclips. After adapting this technology to the analysis of Eardrum motions, fast motions of the Eardrum can be recorded using an
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High-Speed Digital Videoimaging of Fast Eardrum Motions During Valsalva Maneuver
ORL; journal for oto-rhino-laryngology and its related specialties, 1998Co-Authors: Ulrich Vorwerk, Matthias Hey, Gunnar Steinicke, K. BegallAbstract:Digital high-speed camera systems are used to record high-frequency video-clips. After adapting this technology to the analysis of Eardrum motions, fast motions of the Eardrum can be recorded using an endoscope. Under specific static pressure conditions during the Valsalva maneuver, recordings of Eardrum motions were made. The use of a Kodak Image Ektapro 1000 Motion Analyzer allowed only conventional videosignal processing and storage. A new type of data interface made it possible to save and process the complete video-clip digitally. Using an image-processing workstation and special mathematical algorithms, three-dimensional computer animations of fast Eardrum motions under static pressure can be generated. In the present study, several animations of fast Eardrum movements are described. High-speed digital videoimaging is an adequate method to describe fast Eardrum displacements under static pressure (Valsalva maneuver). It is possible to create visible timeshift images of separate Eardrum parts during the fast Valsalva maneuver.
Abbas Samani - One of the best experts on this subject based on the ideXlab platform.
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Estimation of the quasi-static Young's modulus of the Eardrum using a pressurization technique
Computer Methods and Programs in Biomedicine, 2013Co-Authors: Nastaran Ghadarghadar, Sumit K. Agrawal, Abbas Samani, Hanif M. LadakAbstract:The quasi-static Young's modulus of the Eardrum's pars tensa is an important modeling parameter in computer simulations. Recent developments in indentation testing and inverse modeling allow estimation of this parameter with the Eardrum in situ. These approaches are challenging because of the curved shape of the pars tensa which requires special care during experimentation to keep the indenter perpendicular to the local surface at the point of contact. Moreover, they involve complicated contact modeling. An alternative computer-based method is presented here in which pressurization is used instead of indentation. The Young's modulus of a thin-shell model of the Eardrum with subject-specific geometry is numerically optimized such that simulated pressurized shapes match measured counterparts. The technique was evaluated on six healthy rat Eardrums, resulting in a Young's modulus estimate of 22.8?1.5MPa. This is comparable to values estimated using indentation testing. The new pressurization-based approach is simpler to use than the indentation-based method for the two reasons noted above.
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Measuring the quasi-static Young’s modulus of the Eardrum using an indentation technique
Hearing Research, 2010Co-Authors: S. Mohammad Hesabgar, Sumit K. Agrawal, Abbas Samani, Harry R. Marshall, Hanif M. LadakAbstract:Accurate estimation of the quasi-static Young's modulus of the Eardrum is important for finite-element modeling. In this study, we adapted a tissue indentation technique and inverse finite-element analysis to estimate the Young's modulus of the Eardrum. A custom-built indentation apparatus was used to perform indentation testing on seven rat Eardrums in situ after immobilizing the malleus. Testing was done in most cases on the posterior pars tensa. The unloaded shape of each Eardrum was measured and used to construct finite-element models with subject-specific geometries to simulate the indentation experiment. The Young's modulus of each specimen was then estimated by numerically optimizing the Young's modulus of each model so that simulation results matched corresponding experimental data. Using an estimated value of 12 microm for the thickness of each model Eardrum, the estimated average Young's modulus for the pars tensa was found to be 21.7+/-1.2 MPa. The estimated average Young's modulus is within the range reported in some of the literature. The estimation technique is sensitive to the thickness of the pars tensa used in the model but is not sensitive to relatively large variations in the stiffness of the pars flaccida and manubrium or to the pars tensa/pars flaccida separation conditions.
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Measuring the quasi-static Young's modulus of the Eardrum using an indentation technique.
Hearing Research, 2010Co-Authors: S. Mohammad Hesabgar, Sumit K. Agrawal, Abbas Samani, Harry Marshall, Hanif M. LadakAbstract:Accurate estimation of the quasi-static Young's modulus of the Eardrum is important for finite-element modeling. In this study, we adapted a tissue indentation technique and inverse finite-element analysis to estimate the Young's modulus of the Eardrum. A custom-built indentation apparatus was used to perform indentation testing on seven rat Eardrums in situ after immobilizing the malleus. Testing was done in most cases on the posterior pars tensa. The unloaded shape of each Eardrum was measured and used to construct finite-element models with subject-specific geometries to simulate the indentation experiment. The Young's modulus of each specimen was then estimated by numerically optimizing the Young's modulus of each model so that simulation results matched corresponding experimental data. Using an estimated value of 12 microm for the thickness of each model Eardrum, the estimated average Young's modulus for the pars tensa was found to be 21.7+/-1.2 MPa. The estimated average Young's modulus is within the range reported in some of the literature. The estimation technique is sensitive to the thickness of the pars tensa used in the model but is not sensitive to relatively large variations in the stiffness of the pars flaccida and manubrium or to the pars tensa/pars flaccida separation conditions.
