Browsing by Author "Jorge, Renato Natal"
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- Analysis of eardrum pathologies using the finite element methodPublication . Gentil, Fernanda; Garbe, Carolina; Parente, Marco; Martins, Pedro; Ferreira, António; Jorge, Renato Natal; Santos, Carla; Paço, JoãoThis 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.
- Biomechanical study of the vestibular system of the inner ear using a numerical methodPublication . Santos, Carla F.; Belinha, Jorge; Gentil, Fernanda; Parente, Marco; Areias, Bruno; Jorge, Renato NatalThe inner ear has two main parts, the cochlea, dedicated to hearing, and the vestibular system, dedicated to balance. Dizziness and vertigo are the main symptoms related to vestibular disorders, which commonly affects older people. In order to eliminate these symptoms a vestibular rehabilitation is performed; this consists in a range of movements of the head, known as maneuvers, performed by a clinical professional. This procedure does not always work as expected. The aim of this work is to contribute to a better understanding on how the vestibular system works. This knowledge will help in the development of new techniques that will facilitate a more efficient rehabilitation. In order to achieve that goal, a three-dimensional numerical model of the vestibular system, containing the fluids which promote the body balance, was constructed. The vestibular components will be discretized using the finite element method and the fluid flow will be analyzed using the Smoothed Particle Hydrodynamics The results obtained with the numerical model of the semicircular canal built to study the rehabilitation process are presented and compared with other authors. The solution achieved is similar with literature.
- A computational framework to simulate the endolymph flow due to vestibular rehabilitation maneuvers assessed from accelerometer dataPublication . Santos, Carla F.; Belinha, Jorge; Gentil, Fernanda; Parente, Marco; Areias, Bruno; Jorge, Renato NatalVertiginous symptoms are one of the most common symptoms in the world, therefore investing in new ways and therapies to avoid the sense of insecurity during the vertigo episodes is of great interest. The classical maneuvers used during vestibular rehabilitation consist in moving the head in specific ways, but it is not fully understood why those steps solve the problem. To better understand this mechanism, a three-dimensional computational model of the semicircular ducts of the inner ear was built using the finite element method, with the simulation of the fluid flow being obtained using particle methods. To simulate the exact movements performed during rehabilitation, data from an accelerometer were used as input for the boundary conditions in the model. It is shown that the developed model responds to the input data as expected, and the results successfully show the fluid flow of the endolymph behaving coherently as a function of accelerometer data. Numerical results at specific time steps are compared with the corresponding head movement, and both particle velocity and position follow the pattern that would be expected, confirming that the model is working as expected. The vestibular model built is an important starting point to simulate the classical maneuvers of the vestibular rehabilitation allowing to understand what happens in the endolymph during the rehabilitation process, which ultimately may be used to improve the maneuvers and the quality of life of patients suffering from vertigo.
- Cupula response to otoconia debris in the semicircular canalPublication . Santos, Carla F.; Belinha, J.; Gentil, Fernanda; Parente, Marco; Jorge, Renato NatalThe vertigo symptoms are commonly related with inner ear diseases and it affects 20%-30% of the world population, and its prevalence increases with age. In this work, a three-dimensional computational model of the semicircular canal of the vestibular system, containing the fluids which promote the body balance, was used. The smoothed-particle hydrodynamics method was the computational process used to simulate the fluid behaviour, in which the elements are represented by particles and have constant mass. The other vestibular components were discretized using the finite element method. The movement performed to endolymph/cupula interaction analysis was reproduced in the simulation through the acquisition of the displacement field based on image analysis. The results obtained with the frames of the video recorded during the process is the appropriate method to simulate the real moves, due to the analysis of the region of interest located near the inner ear. The data obtained from the video acquisition were the input in the simulation with the semicircular model. The principal stress cupular response allowed to understand the interaction of the vestibular structures during a vertigo episode, and the influence of the otoconia in the cupula displacement. This model is the first step to improve the vestibular rehabilitation and the quality of life of patients suffering from vertigo.
- Effects of the fibers distribution in the human eardrum: A biomechanical studyPublication . Gentil, Fernanda; Parente, Marco; Martins, Pedro; Garbe, Carolina; Santos, Carla; Areias, Bruno; Branco, Carla; Paço, João; Jorge, Renato NatalThe eardrum separates the external ear from the middle ear and it is responsible to convert the acoustical energy into mechanical energy. It is divided by pars tensa and pars flaccida. The aim of this work is to analyze the susceptibility of the four quadrants of the pars tensa under negative pressure, to different lamina propria fibers distribution. The development of associated ear pathology, in particular the formation of retraction pockets, is also evaluated. To analyze these effects, a computational biomechanical model of the tympano-ossicular chain was constructed using computerized tomography images and based on the finite element method. Three fibers distributions in the eardrum middle layer were compared: case 1 (eardrum with a circular band of fibers surrounding all quadrants equally), case 2 (eardrum with a circular band of fibers that decreases in thickness in posterior quadrants), case 3 (eardrum without circular fibers in the posterior/superior quadrant). A static analysis was performed by applying approximately 3000Pa in the eardrum. The pars tensa of the eardrum was divided in four quadrants and the displacement of a central point of each quadrant analyzed. The largest displacements of the eardrum were obtained for the eardrum without circular fibers in the posterior/superior quadrant.
- How the computational methods can contribute to better knowledge of the earPublication . Gentil, Fernanda; Parente, Marco; Santos, Carla; Areias, Bruno; Belinha, Jorge; Jorge, Renato NatalThe biomechanical behavior of the human ear can be studied using mathematical approaches, such as the finite element method. This methodology allows to perform simulations to evaluate the influence of sound transmission through all way of the ear, since the sound is selected by the outer ear to the inner ear. The finite element method is currently the preferred method for the numerical solution of partial differential equations, and it is used in several fields of the biological sciences. Due to its large applicability and efficiency, there are several works where this methodology is applied in different specialties, to analyze loads, strains or displacements, as in the case of the biomechanical study of the ear. From CT images, three-dimensional accurate computational models are created. The technique employs a set of calculations of numerical analysis for solutions of kinematic (displacements and rotations) and mechanical aspects (strength, stress, pressure, deformation). The use of these computer models enables the motion analysis of all ossicular chain points at any moment.
- Influence of middle ear tumours on the biomechanical behaviour of the chorda tympaniPublication . Mendonça, Leonor; Santos, Carla F.; Gentil, Fernanda; Parente, Marco; Areias, Bruno; Jorge, Renato NatalChronic otitis media may lead to the development of a cholesteatoma, a benign middle ear tumour. If this occurs, the chorda tympani nerve, a facial nerve branch that crosses the middle ear, may be compromised. The influence of cholesteatoma development near chorda tympani nerve was studied, in order to assess the consequences of this mass in terms of possible facial paralysis. To do so, an ear model based on the finite element method was used. The chorda tympani nerve was originally discretized and assembled in the model. Two different sized tumours were created so cholesteatoma growth could be simulated. The pressure in this nerve were assessed in two moments - when the tumour first interacts with it, pushing it down, and when the tumour compresses it against the incus. Moreover, the effect of applying pressure directly on the nerve was also evaluated, so tumour geometry did not interfere in the analysis. The obtained stress allowed to infer on the consequences regarding taste disturbance and facial paralysis, although some studies report that when pressure fades away, it is possible to fully recover. The von Mises stress was higher when the chorda tympani nerve was pushed against the incus by the large tumour, in the contact area between the nerve and the ossicle.
- Influence of the basilar membrane shape and mechanical properties in the cochlear response: A numerical studyPublication . Areias, Bruno; Parente, Marco; Gentil, Fernanda; Jorge, Renato NatalHearing impairment is one of the most common health disorders, affecting individuals of all ages, reducing considerably their quality of life. At present, it is known that during an acoustic stimulation a travelling wave is developed inside the cochlea. Existing mathematical and numerical models available in the literature try to describe the shape of this travelling wave, the majority of them present a set of approaches based on some limitations either or both of the mechanical properties used and the geometrical description of the realistic representation. The present numerical study highlights the distinctions of using a spiral model of the cochlea, by comparing the obtained results with a straight, or simplified model. The influence of the implantation of transversely isotropic mechanical models was also studied, by comparing the basilar membrane with isotropic and transversely isotropic mechanical properties. Values of the root mean square error calculated for all models show a greater proximity of the cochlear mapping to the Greenwood function when the basilar membrane is assumed with transversely isotropic mechanical properties for both straight and spiral model. The rootmean square errors calculated were: 2.05, 1.70, 2.72, 2.08 mm, for the straight-isotropic, straight-transversely isotropic, spiral-isotropic and spiral-transversely isotropic model, respectively.
- Modelação computacional de um tumor do ouvido médio e análise biomecânica do seu impacto na audiçãoPublication . Santos, Carla F.; Mendonça, Leonor; Gentil, Fernanda; Parente, Marco; Jorge, Renato NatalA otite média crónica é uma condição que pode levar ao aparecimento e crescimento de um tumor benigno do ouvido médio, um colesteatoma, o que poderá comprometer a audição [1]. De forma a avaliar a influência do crescimento de um colesteatoma na função auditiva, foi utilizado um modelo do ouvido médio desenvolvido através do método de elementos finitos. O colesteatoma foi modelado na conexão entre o martelo e a bigorna, e foram desenvolvidos três tumores de diferente tamanho [2]. Os deslocamentos da membrana timpanica e da platina do estribo foram analisados após a imposição de um nível de pressão sonora de 80dB SPL na membrana timpânica. Foi realizada uma análise entre as frequências de 100Hz a 10kHz para estado estacionário. Os resultados foram comparados com a situação saudável e a análise indica que o desenvolvimento do colesteatoma leva à diminuição dos deslocamentos das estruturas no inicio e no fim da cadeia ossicular. Outras simulações que foram realizadas incluem a atribuição de diferentes propriedades ao tumor de maiores dimensões, considerando que estas estruturas se tornam mais duras e densas ao longo do tempo. A degradação dos ossículos simulando uma situação real e atribuindo propriedades do tumor a alguns elementos ósseos também foi analisada. Nos resultados correspondentes a estas simulações foram observadas as maiores diferenças de deslocamento. É cientificamente aceite que estas diferenças no deslocamento estão relacionadas com a perda auditiva, desta forma é possível concluir que o crescimento de um tumor no ouvido médio irá conduzir a problemas auditivos.
- Numerical simulation of the maneuvers performed in vestibular rehabilitationPublication . Santos, Carla F.; Parente, Marco; Belinha, Jorge; Jorge, Renato Natal; Gentil, FernandaThe aim of this work is to contribute to a better understanding on how the vestibular system works. This knowledge will help in the development of new techniques that will facilitate a more efficient rehabilitation. Vestibular rehabilitation consists in a set of exercises, known as maneuvers, which can reduce and even eliminate the symptoms of dizziness and imbalance associated with a vestibular disorder. In this work, a three-dimensional model of the vestibular system, containing the fluids which promote the body balance, will be used. One of the aims is to simulate the fluid behaviour and the study of its interaction with the soft tissues of the vestibular structure. This model will allow the simulation of the maneuvers of the vestibular rehabilitation in order to improve its results and the quality of life of patients suffering from vertigo.