Bio-computational study of tinnitus

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The influence of muscles activation on the dynamical behaviour of the tympano-ossicular system of the middle ear

Publication . Gentil, Fernanda; Parente, Marco; Martins, Pedro; Garbe, Carolina; Paço, João; Ferreira, António J.M.; Tavares, João Manuel R.S.; Jorge, Renato Natal

The human ear is a complex biomechanical system and is divided into three parts: outer, middle and inner ear. The middle ear is formed by ossicles (malleus, incus and stapes), ligaments, muscles and tendons, which transfers sound vibrations from the eardrum to the inner ear, linking with mastoid and Eustachian tube. In this work, a finite element modelling of the tympano-ossicular system of the middle ear was developed. A dynamic study based on a structural response to harmonic vibrations, for a sound pressure level (SPL) of 110, 120 and 130 dB SPL applied in the eardrum, is presented. The connection between the ossicles is made using a contact formulation. The model includes the different ligaments considering its hyperelastic behaviour. The activation of the muscles is based on the constitutive model proposed by previous work. The harmonic responses of displacement and pressure obtained on the stapes footplate, for a frequency range between 100 Hz and 10 kHz, are obtained simulating the muscle activation. The results are compared considering the passive and active states. The results are discussed and they are in accordance with audiological data published with reference to the effects of the middle ear muscles contraction.

2013Journal article

Open access

Segmentation algorithms for ear image data towards biomechanical studies

Publication . Ferreira, Ana; Gentil, Fernanda; Tavares, João Manuel R. S.

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.

2014Journal article

Open access

Analysis of eardrum pathologies using the finite element method

Publication . Gentil, Fernanda; Garbe, Carolina; Parente, Marco; Martins, Pedro; Ferreira, António; Jorge, Renato Natal; Santos, Carla; Paço, João

This work investigates the effect of eardrum perforations and myringosclerosis in the mechanical behavior of the tympano-ossicular chain. A 3D model for the tympano-ossicular chain was created and different numerical simulations were made, using the finite element method. For the eardrum perforations, three different calibers of perforated eardrums were simulated. For the micro perforation (0.6 mm of diameter) no differences were observed between the perforated and normal eardrum. For the numerical simulation of the eardrum with the largest perforation caliber, small displacements were obtained in the stapes footplate, when compared with the model representative of normal ossicular-chain, at low frequencies, which is related with major hearing loss in this frequency range. For the numerical simulations of myringosclerosis, the larger differences in the displacement field between the normal and modified model were obtained in the umbo. When observing the results in the stapes footplate, there were no significant differences between the two models, which is in accordance to the clinical data. When simulating an eardrum perforation along with myringosclerosis, there is a decrease in the displacements, both from the umbo and the central part of the stapes footplate, often associated with a pronounced hearing loss. It could be concluded that the reduced displacement of the stapes footplate may be related to a greater hearing loss.

2014Journal article

Open access