Biomedical subjects

Rong Z Gan

Publications and source records attributed to Rong Z Gan.

6 recordsLinked to original sources

PubMed2005

Acoustic-structural coupled finite element analysis for sound transmission in human ear--pressure distributions.

A three-dimensional (3D) finite element (FE) model of human ear with accurate structural geometry of the external ear canal, tympanic membrane (TM), ossicles, middle ear suspensory ligaments, and middle ear cavity has been recently reported by our group. In present study, this 3D FE model was modified to include acoustic-structural interfaces for coupled analysis from the ear canal through the TM to middle ear cavity. Pressure distributions in the canal and middle ear cavity at different frequencies were computed under input sound pressure applied at different locations in the canal. The spectral distributions of middle ear pressure at the oval window, round window, and medial site of the umbo were calculated and the results demonstrated that there was no significant difference of pressures between those locations at frequency below 3.5 kHz. Finally, the influence of TM perforation on pressure distributions in the canal and middle ear cavity was investigated for perforations in the inferior-posterior and inferior sites of the TM in the FE model and human temporal bones. The results show that variation of middle ear pressure is related to the perforation type and location, and is sensitive to frequency.

Acoustic Stimulation↗

PubMed2004

Lumped parametric model of the human ear for sound transmission.

A lumped parametric model of the human auditoria peripherals consisting of six masses suspended with six springs and ten dashpots was proposed. This model will provide the quantitative basis for the construction of a physical model of the human middle ear. The lumped model parameters were first identified using published anatomical data, and then determined through a parameter optimization process. The transfer function of the middle ear obtained from human temporal bone experiments with laser Doppler interferometers was used for creating the target function during the optimization process. It was found that, among 14 spring and dashpot parameters, there were five parameters which had pronounced effects on the dynamic behaviors of the model. The detailed discussion on the sensitivity of those parameters was provided with appropriate applications for sound transmission in the ear. We expect that the methods for characterizing the lumped model of the human ear and the model parameters will be useful for theoretical modeling of the ear function and construction of the ear physical model.

Acoustic Stimulation↗

PubMed2004

Three-dimensional finite element modeling of human ear for sound transmission.

An accurate, comprehensive finite element model of the human ear can provide better understanding of sound transmission, and can be used for assessing the influence of diseases on hearing and the treatment of hearing loss. In this study, we proposed a three-dimensional finite element model of the human ear that included the external ear canal, tympanic membrane (eardrum), ossicular bones, middle ear suspensory ligaments/muscles, and middle ear cavity. This model was constructed based on a complete set of histological section images of a left ear temporal bone. The finite element (FE) model of the human ear was validated by comparing model-predicted ossicular movements at the stapes footplate and tympanic membrane with published experimental measurements on human temporal bones. The FE model was employed to predict the effects of eardrum thickness and stiffness, incudostapedial joint material, and cochlear load on acoustic-mechanical transmission through the human ossicular chain. The acoustic-structural coupled FE analysis between the ear canal air column and middle ear ossicles was also conducted and the results revealed that the peak responses of both tympanic membrane and stapes footplate occurred between 3000 and 4000 Hz.

Acoustic Stimulation↗

PubMed2004

Human middle ear transfer function measured by double laser interferometry system.

HYPOTHESIS: Simultaneous measurements of vibrations on the stapes footplate, incudostapedial (IS) joint, and tympanic membrane (TM) can be made in both normal and drained cochleae, and the stapes displacement transfer function (S-DTF) and TM displacement transfer function (TM-DTF) are derived. BACKGROUND: A single laser Doppler interferometer previously has been used for measuring movement of the stapes or TM in temporal bones. However, there may be a limitation to optimally describing acoustic-mechanical transmission when the interferometer and temporal bone are moved frequently during experimental recordings. Simultaneous measurements of vibrations of the TM and stapes footplate, or TM and IS joint may reveal different acoustic-mechanical characteristics of the middle ear. METHODS: Dual laser interferometers simultaneously measured vibrations of the TM, IS joint, and stapes in 10 temporal bones with both intact and drained cochleae. From these measurements, the middle ear transfer function was expressed as the S-DTF, TM-DTF, and displacement transmission ratio (DTR). RESULTS: Simultaneous displacements of the TM, IS joint, and stapes footplate induced by sound pressure in the ear canal were recorded in both amplitude and phase. The middle ear transfer functions in terms of displacement ratio confirmed published single interferometer data but provided new information from drained cochlea. CONCLUSION: Stapes and TM displacement transfer functions were determined using dual interferometry, provided accurate amplitude and phase relationships from stapes footplate, IS joint, and TM, with new data from drained and normal cochlea.

Acoustic Stimulation↗

PubMed2002

An advanced computer-aided geometric modeling and fabrication method for human middle ear.

This paper presents a practical and systematic method for reconstructing accurate computer and physical models of the entire human middle ear. The proposed method starts with the histological section preparation of human temporal bone. Through tracing outlines of the middle ear components on the sections, a set of discrete points is obtained and employed to construct B-spline curves that represent the exterior contours of the components using a curve-fitting technique. The surface-skinning technique is then employed to quilt the B-spline curves for smooth boundary surfaces of the middle ear components using B-spline surfaces. The solid models of the middle ear components are constructed using these surfaces and then assembled to create the entire middle ear in a computer-aided design environment. This method not only provides an effective way to visualize and measure the three-dimensional structure of the middle ear, but also provides a detailed knowledge of middle ear geometry that is required for finite element analysis or multibody dynamic analysis of the human middle ear. In addition, the geometric model constructed using the proposed method is smooth and can be fabricated in various scales using solid freeform fabrication technology. The physical model of the human middle ear is extremely effective in realizing the middle ear anatomy and enhancing discussion and collaboration among researchers and physicians.

Anatomy, Cross-Sectional↗

PubMed2002

Three-dimensional modeling of middle ear biomechanics and its applications.

HYPOTHESIS: This study investigated whether combined technologies of finite element (FE) analysis and three-dimensional reconstruction of human temporal bones could be used to construct a computational model, useful in describing normal and pathologic middle ear sound conduction. BACKGROUND: FE models for biologic systems have been used in ear biomechanics. Three-dimensional reconstructions have also been made, but not in combination with FE modeling and laser interferometry measuring of human temporal bones. Furthermore, an FE model for the human middle ear with its ossicular attachments has not been reported on the basis of temporal bone histologic sections and morphometric reconstruction, to the authors' best knowledge. Because of the size, variability, and complexity of the middle ear, accurate morphologic data and boundary conditions are necessary for accurate FE modeling. METHODS: A fresh temporal bone was decalcified, embedded in celloidin, sectioned and stained, scanned, and digitized, and the normal middle ear was reconstructed. The histologic sections were used to construct a computer-aided design model with ligaments, muscles, and tendons as boundary conditions. The data thus obtained were converted into an FE mechanical model that was validated by comparison with displacements obtained by laser Doppler interferometry on 17 fresh human temporal bones. RESULTS: An FE model was generated, demonstrating dynamic behavior that moderately approximated the laser interferometric data from human temporal bones receiving 90-dB sound pressure level auditory frequencies at the tympanic membrane. CONCLUSION: Accurate FE modeling, incorporating both morphometric and interferometric performance data, predicted both normal and pathologic mechanical performance of the human ossicular chain.

Biomechanical Phenomena↗