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Browsing ESS - AUD - Artigos by Author "Areias, Bruno"
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- 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.
- 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.
- A finite element model to predict the consequencesof endolymphatic hydrops in the basilar membranePublication . Areias, Bruno; Parente, Marco P. L.; Gentil, Fernanda; Caroça, Cristina; Paço, João; Jorge, Renato M. NatalMénière's disease is an inner ear disorder, associated with episodes of vertigo,fluctuant hearing loss, tinnitus, and aural fullness. Ménière's disease is associ-ated with endolymphatic hydrops. Clinical evidences show that this disease isoften incapacitating, negatively affecting the patients' everyday life. The patho-genesis of Ménière's disease is still not fully understood and remains unclear.Previous numerical studies available in the literature related with endolym-phatic hydrops, are very scarce. The present work applies the finite elementmethod to investigate the consequences of endolymphatic hydrops in the nor-mal hearing, associated with the Ménière's disease. The obtained results forthe steady state dynamics analysis are in accordance with clinical evidences.The results show that the basilar membrane is not affected in the same inten-sity along its length and that the lower frequencies are more affected by theendolymphatic hydrops. From a clinical point of view, this work shows therelationship between the increasing of the endolymphatic pressure andthe development of hearing loss.
- Finite element modelling of sound transmission from outer to inner earPublication . Areias, Bruno; Santos, Carla; Natal Jorge, Renato M; Gentil, Fernanda; Parente, Marco P. L.The ear is one of the most complex organs in the human body. Sound is a sequence of pressure waves, which propagates through a compressible media such as air. The pinna concentrates the sound waves into the external auditory meatus. In this canal, the sound is conducted to the tympanic membrane. The tympanic membrane transforms the pressure variations into mechanical displacements, which are then transmitted to the ossicles. The vibration of the stapes footplate creates pressure waves in the fluid inside the cochlea; these pressure waves stimulate the hair cells, generating electrical signals which are sent to the brain through the cochlear nerve, where they are decoded. In this work, a three-dimensional finite element model of the human ear is developed. The model incorporates the tympanic membrane, ossicular bones, part of temporal bone (external auditory meatus and tympanic cavity), middle ear ligaments and tendons, cochlear fluid, skin, ear cartilage, jaw and the air in external auditory meatus and tympanic cavity. Using the finite element method, the magnitude and the phase angle of the umbo and stapes footplate displacement are calculated. Two slightly different models are used: one model takes into consideration the presence of air in the external auditory meatus while the other does not. The middle ear sound transfer function is determined for a stimulus of 60 dB SPL, applied to the outer surface of the air in the external auditory meatus. The obtained results are compared with previously published data in the literature. This study highlights the importance of external auditory meatus in the sound transmission. The pressure gain is calculated for the external auditory meatus.
- Finite element modelling of the surgical procedure for placement of a straight electrode array: Mechanical and clinical consequencesPublication . Areias, Bruno; Parente, Marco P. L.; Gentil, Fernanda; Jorge, Renato M. NatalA cochlear implant is an electronic device implanted into the cochlea to directly stimulate the auditory nerve. Such device is used in patients with severe-to-profound hearing loss. The cochlear implant surgery is safe, but involves some risks, such as infections, device malfunction or damage of the facial nerve and it can result on a poor hearing outcome, due to the destruction of any present residual hearing. Future improvements in cochlear implant surgery will necessarily involve the decrease of the intra-cochlear damage. Several implant related variables, such as materials, geometrical design, processor and surgical techniques can be optimized in order for the patients to partially recover their hearing capacities The straight electrode is a type of cochlear implant that many authors indicate as being the less traumatic. From the finite element analysis conducted in this work, the influence of the insertion speed, the friction coefficient between the cochlear wall and the electrode array, and several configurations of the cochlear implant tip were studied. The numerical simulations of the implantation showed the same pattern of the insertion force against insertion depth, thus indicating the different phases of the insertion. Results demonstrated that lower insertion speeds, friction coefficients and tip stiffness, led to a reduction on the contact pressures and insertion force. It is expected that these improved configurations will allow to preserve the residual hearing while reducing surgical complications.
- 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.
- Numerical study of tympanosclerosis including its effect on human hearingPublication . Gentil, Fernanda; Parente, Marco; Santos, Carla; Areias, Bruno; Jorge, Renato NatalTympanosclerosis is an abnormal disorder of the middle ear or only the eardrum (i.e., myringosclerosis) in which there are calcium deposits. Normally, it is caused by recurrent middle ear infections. In this work, a 3D finite element model of the ear was developed, simulating different cases of tympanosclerosis. Through this model, the magnitude and the phase angle of the umbo and stapes displacement were obtained. The middle ear sound transfer function was determined for a stimulus of 80, 90 and 100 dB SPL, in a frequency range between 100 Hz and 10 kHz, applied on the outer surface of the eardrum in the external auditory canal. Depending on the tympanosclerosis affected area, the main conclusion is that worse results (leading to hearing loss) occur when all of the ossicular chain is affected.