Browsing by Author "Santos, Carla F."
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- 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.
- Biomechanics of the vestibular system: a numerical simulationPublication . Santos, Carla F.; Belinha, Jorge; Gentil, Fernanda; Parente, Marco; Jorge, Renato M. NatalThe vestibular system is located in the posterior portion of the inner ear. It is a key component to our sense of balance and movement. Any changes in this system can cause effects or symptoms such as dizziness, blurred vision, imbalance, and nausea, which are vertiginous syndrome indicators. Vertigo is reported as one of the most common symptoms in the world. It is considered the third most frequent complaint in medicine, transmitting a sense of inadequacy and insecurity. The aim of this work is to contribute to a better understanding of how the vestibular system works. This knowledge will help in the development of new techniques that will facilitate a more effective rehabilitation. Vestibular rehabilitation consists of a set of exercises, known as maneuvers, which can reduce and even eliminate symptoms of dizziness and imbalance associated with a vestibular disorder. In this work, a three-dimensional computational model of the vestibular system, containing the fluids promoting the body balance, will be presented. The smoothed-particle hydrodynamics (SPH) method will be used to simulate the fluid behavior. The results provide a better comprehension of the biomechanics of the vestibular system, which contribute to recover from any system disorders.
- 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.
- 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.
- 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.
- On the hearing effects of a cholesteatoma growing: A biomechanical studyPublication . Mendonça, Leonor ; Santos, Carla F.; Gentil, Fernanda; Parente, Marco ; Areias, Bruno ; Jorge, Renato NatalChronic otitis media enables the appearance of a benign middle ear tumor, known as a cholesteatoma, that may compromise hearing. To evaluate the influence of a cholesteatoma growth on the hearing function, a computational middle ear model based on the finite element method was used and three different size of cholesteatoma were modeled. The cholesteatoma solidification and the consequent degradation of the ossicles were also simulated as two condition that commonly occurs during cholesteatoma evolution. A sound pressure level of 80 dB SPL was applied in the tympanic membrane and a steady state analysis was performed for frequencies from 100 Hz to 10 kHz. The displacements of both the tympanic membrane and the stapes footplate were measured. The results were compared with a healthy case and it was shown that the cholesteatoma development leads to a decrease in the umbo and stapes displacements. The ossicles degradation simulation showed the higher difference comparing with the cholesteatoma in an initial stage, with lower displacements in the stapes footplate mainly for high frequencies. The observed displacement differences are directly connected to hearing loss, being possible to conclude that cholesteatoma evolution in the middle ear will lead to hearing problems, mainly in an advanced stage.
- Simulação do comportamento da cupula do ouvido interno em casos patológicosPublication . Santos, Carla F.; Belinha, Jorge; Gentil, Fernanda; Parente, Marco; Jorge, Renato N.O sistema vestibular é a estrutura do ouvido interno que contribui, juntamente com a visão e a locomoção, para a manutenção do equilíbrio do corpo humano. A enfolinfa é um fluido que se estabelece como um dos seus principais constituintes e encontra-se no interior da estrutura óssea e membranosa que constitui o sistema vestibular. A vertigem é um dos principais sintomas resultante de perturbações associadas ao sistema vestibular. Sendo esta uma das patologias mais frequentes em todo o mundo e a principal queixa em idosos, é essencial o seu estudo de modo a prevenir as complicações que podem advir de uma tontura, como por exemplo uma queda. O objetivo do trabalho apresentado é contribuir para um melhor entendimento relativamente à biomecânica do sistema vestibular. Na consequência deste estudo pretende-se associar este conhecimento a uma das terapêuticas mais comuns em caso de patologia de vertigem que é a reabilitação vestibular, a qual resulta de um processo empírico. O modelo computacional usado no presente estudo foi construído com base nas dimensões de um ouvido interno humano. A parte exterior do modelo, que reproduz a membrana exterior do canal, foi discretizada utilizando elementos de casca (S4R). Relativamente à representação da cupula e da endolinfa, que se encontram do interior da membrana, foram utilizados elementos tetraédricos (C3D4) e elementos de partículas (PC3D), respetivamente. A densidade e a viscosidade utilizadas para a endolinfa são respetivamente 1.0kg/m3 e 4.8x10-3Pa.s. As simulações foram realizadas com o software ABAQUS. A utilização de elementos finitos para simulação e construção de modelos biomecânicos mostrou, como esperado, ser uma opção eficiente. Os resultados obtidos com este trabalho foram um primeiro passo para compreender a diferença do funcionamento mecânico da estrutura da cúpula em casos saudáveis e patológicos relacionados com a vertigem. Este estudo permitirá melhorar a tomada de decisão no processo de reabilitação vestibular.
- The free vibration computational analysis of the cupula in the inner earPublication . Santos, Carla F.; Belinha, Jorge; Gentil, Fernanda; Parente, Marco; Areias, Bruno; Jorge, Renato NatalThe three semicircular canals, arranged in three orthogonal planes, are the main components of the inner ear with the balance function. They are sensitive to angular acceleration [1,2]. Each canal is composed of a circular path of fluid continuity, interrupted at the cupula, where the sensory epithelium is placed - known as hair cells, which is the focus of this work. The hair cells exhibit constant discharge of neurotransmitters that are modified by the direction of cupula deflection. One of the causes of vestibular disorders is the abnormal concentration of otoconia particles in the vicinity of the cupula. Thus, the accurate determination of the natural frequency (first vibration mode) of the cupula will allow to stimulate externally the cupula. Theoretically, the resonance phenomena will disperse the otoconia particles, reducing the vertigo symptoms. In order to understand the dynamic response of the cupula, first it is necessary to obtain its free vibration modes. Thus, a 2D and 3D geometrical model of the cupula was constructed. Then, a free vibration analysis was performed using two distinct numerical techniques, such as the finite element method (FEM) and a radial point interpolation meshless method (RPIM). Meshless methods are advanced discretization techniques that allow to discretize the problem domain using only a cloud of points, allowing them to discretize geometrical models directly from medical images. The results obtained with the 2D and 3D geometrical model show that RPIM is capable to deliver results very similar with the FEM. However, the RPIM solution is smoother. On the other hand, the FEM computational cost is lower than the RPIM.