The Experts below are selected from a list of 306 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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Thickness of the human eardrum in fresh and preserved specimens
Middle Ear Mechanics in Research and Otology, 2004Co-Authors: Liesbeth C. Kuypers, Joris J.j. DirckxAbstract:In literature, data of eardrum thickness is only available at a small number of measuring points by means of conventional light microscopy. The membrane had to be fixed, dehydrated, stained and decalcified to obtain histological sections. This process induces shrinking and hence influences the thickness measurements. We have used an optical sectioning technique and developed a procedure that can be applied for quantitative thickness measurements of fresh tissue. By this procedure, measured data is corrected for the effects caused by refractive-index mismatch to obtain exact thickness. We developed a numerical correction procedure to obtain calibrated data from confocal depth measurements. We present a quantitative comparison of thickness measurement between a fresh eardrum and the same membrane in the successive stages of preparation. On the basis of this analysis it becomes possible to quantify shrinking artifacts on histological sections. In a first stage, the eardrum was dissected out of the fresh temporal bone and optical depth sections perpendicular to the eardrum’s surface were recorded with a confocal microscope. From adjacent images along anterior-to-posterior lines across the membrane, several thickness profiles were obtained. Next, the tissue was fixed. Thickness was measured along the same lines. In a third stage, the tissue was preserved in Cialit for six days, where after and thickness was measured along the same lines. In the last stage, the tissue was decalcified, dehydrated and stained before slicing it with a microtome. Histological sections were studied with a conventional light microscope to obtain thickness data at the same positions as before. This study shows no significant difference in thickness between the untreated, fixed and in-Cialitpreserved eardrum. There is, however, a large difference in thickness between the preserved and the prepared eardrum. The preparation method to obtain histological sections does induce a shrinking effect up to 25 %.
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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.
Shmuel C. Shapira - One of the best experts on this subject based on the ideXlab platform.
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Eardrum Perforation in Explosion Survivors: Is It a Marker of Pulmonary Blast Injury?
Annals of Emergency Medicine, 1999Co-Authors: Dan Leibovici, Ofer N. Gofrit, Shmuel C. ShapiraAbstract:Abstract Study Objectives: To determine whether isolated eardrum perforation is a marker for concealed blast lung injury in survivors of terrorist bombings. Methods: Survivors who arrived at hospitals after 11 terrorist bombings in Israel between April 6, 1994, and March 4, 1996, were examined otoscopically by ear, nose, and throat specialists. All patients with eardrum perforation underwent chest radiography and were hospitalized for at least 24 hours for observation. The clinical course and final outcome of patients with isolated perforation of the Eardrums and of those with other blast injuries were surveyed. Results: A total of 647 survivors were examined; 193 (29.8%) of them sustained primary blast injuries, including 142 with isolated eardrum perforation and 51 with other forms of blast injuries (18 with isolated pulmonary blast injury, 31 with combined otic and pulmonary injuries, and 2 with intestinal blast injury). Blast lung injury was promptly diagnosed on admission by physical examination and chest radiography. No patient presenting with isolated eardrum perforation developed later signs of pulmonary or intestinal blast injury (mean 0%; 95% confidence interval, 0% to 2.7%). Conclusion: Isolated eardrum perforation in survivors of explosions does not appear to be a marker of concealed pulmonary blast injury nor of a poor prognosis. Therefore, in a mass casualty event, persons who have sustained isolated eardrum perforation from explosions may safely be discharged from the emergency department after chest radiography and a brief observation period. [Leibovici D, Gofrit ON, Shapira SC: Eardrum perforation in explosion survivors: Is it a marker of pulmonary blast injury? Ann Emerg Med August 1999;34:168-172.]
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Eardrum Perforation in Explosion Survivors: Is It a Marker of Pulmonary Blast Injury?
Annals of emergency medicine, 1999Co-Authors: Dan Leibovici, Ofer N. Gofrit, Shmuel C. ShapiraAbstract:To determine whether isolated eardrum perforation is a marker for concealed blast lung injury in survivors of terrorist bombings. Survivors who arrived at hospitals after 11 terrorist bombings in Israel between April 6, 1994, and March 4, 1996, were examined otoscopically by ear, nose, and throat specialists. All patients with eardrum perforation underwent chest radiography and were hospitalized for at least 24 hours for observation. The clinical course and final outcome of patients with isolated perforation of the Eardrums and of those with other blast injuries were surveyed. A total of 647 survivors were examined; 193 (29.8%) of them sustained primary blast injuries, including 142 with isolated eardrum perforation and 51 with other forms of blast injuries (18 with isolated pulmonary blast injury, 31 with combined otic and pulmonary injuries, and 2 with intestinal blast injury). Blast lung injury was promptly diagnosed on admission by physical examination and chest radiography. No patient presenting with isolated eardrum perforation developed later signs of pulmonary or intestinal blast injury (mean 0%; 95% confidence interval, 0% to 2.7%). Isolated eardrum perforation in survivors of explosions does not appear to be a marker of concealed pulmonary blast injury nor of a poor prognosis. Therefore, in a mass casualty event, persons who have sustained isolated eardrum perforation from explosions may safely be discharged from the emergency department after chest radiography and a brief observation period.
Willem F. Decraemer - One of the best experts on this subject based on the ideXlab platform.
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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.
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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 moiré 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.
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.
