Scielo RSS <![CDATA[Revista Brasileira de Engenharia Biomédica]]> vol. 29 num. 3 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>A transição da RBEB para inglês</b>]]> <![CDATA[<b>Web-based neuromuscular simulator applied to the teaching of principles of neuroscience</b>]]> INTRODUCTION: The learning of core concepts in neuroscience can be reinforced by a hands-on approach, either experimental or computer-based. In this work, we present a web-based multi-scale neuromuscular simulator that is being used as a teaching aid in a campus-wide course on the Principles of Neuroscience. METHODS: The simulator has several built-in individual models based on cat and human biophysics, which are interconnected to represent part of the neuromuscular system that controls leg muscles. Examples of such elements are i) single neurons, representing either motor neurons or interneurons mediating reciprocal, recurrent and Ib inhibition; ii) afferent fibers that can be stimulated to generate spinal reflexes; iii) muscle unit models, generating force and electromyogram; and iv) stochastic inputs, representing the descending volitional motor drive. RESULTS: Several application examples are provided in the present report, ranging from studies of individual neuron responses to the collective action of many motor units controlling muscle force generation. A subset of them was included in an optional homework assignment for Neuroscience and Biomedical Engineering graduate students enrolled in the course cited above at our University. Almost all students rated the simulator as a good or an excellent learning tool, and approximately 90% declared that they would use the simulator in future projects. CONCLUSION: The results allow us to conclude that multi-scale neuromuscular simulator is an effective teaching tool. Special features of this free teaching resource are its direct usability from any browser (, its user-friendly graphical user interface (GUI) and the preset demonstrations. <![CDATA[<b>Aging related responses to conflicting proprioceptive and visual information about initial position during reaching</b>]]> INTRODUCTION: The purpose of the current study was to examine whether age-related differences are exhibited in the relative contributions of vision and proprioception with initial hand position to the control of movement distance of single-joint reaching movements. METHODS: We use a virtual reality display to systematically change the relationship between the actual hand position and the displayed hand position (virtual position) as subjects' positioned a cursor within a start circle. Visual feedback of the reaching hand was only available before movement onset. Two groups of subjects (older and young) reached to two different visual targets (115º and 125º elbow angle) from four possible starting locations (90º, 95º, 100º, 105º elbow angle) under four virtual/actual dissociation conditions (0º, 5º, 10º, 15º). RESULTS: For the mismatched conditions movement distance was generally longer for the older adults as compared to the younger. Also, the younger group better scaled their movement extent with cursor initial location, whereas, the older group showed scaling with hand location. Our results indicate age-related differences in the effects of initial position information when vision and proprioception initial information were dissociated. CONCLUSION: The young were able to completely rely on visual information through feedforward mechanism applying acceleration amplitude manipulation for controlling movement distance. In contrast, older subjects relied on proprioceptive information for the scaling of peak velocity with movement distance, suggesting more reliance on feedback-mediated error-correction mechanisms during the course of movement. <![CDATA[<b>Computer-aided system for diagnosis of Chagas' disease based on scalograms and self-organizing neural networks</b>]]> INTRODUÇÃO: A Doença de Chagas é uma endemia rural, prevalente em grande parte da América Central e América do Sul e, aproximadamente, metade dos pacientes contaminados com o parasita Trypanosoma cruzi não apresentam sinais clínicos, eletrocardiográficos e radiológicos de envolvimento cardíaco. Este trabalho, entretanto, propõe uma técnica de auxílio ao diagnóstico da Doença de Chagas baseada em sinais de eletrocardiografia, que extrai informações relevantes desses sinais. MÉTODOS: Duas abordagens são estudadas e implementadas. Ambas utilizam sinais de variabilidade da frequência cardíaca (VFC) e classificação por meio de rede neural, mais especificamente, o mapa auto-organizável de Kohonen. A VFC, que reflete a modulação neural autonômica simpática e parassimpática do coração, é avaliada com base em séries contínuas de intervalos RR do ECG convencional registradas durante 5 minutos. Na primeira abordagem, indicadores estatístico-temporais obtidos diretamente dos sinais de VFC são utilizados como entrada da rede neural para treinamento e teste do método de classificação. Na segunda proposta, são utilizados escalogramas wavelet com função de base DoG (derivative of Gaussian) para avaliação dos sinais de VFC. Indicadores obtidos dos escalogramas são utilizados como entrada da rede neural no treinamento e no teste do algoritmo. Os mapas topológicos de Kohonen são utilizados para comparar a capacidade dos indicadores calculados dos sinais de VFC em discriminar pacientes chagásicos cardiopatas, chagásicos indeterminados e indivíduos normais. Os indicadores temporais convencionais e os indicadores escalográficos são comparados. RESULTADOS: Os resultados mostram que os indicadores escalográficos têm poder discriminatório estatisticamente superior aos indicadores temporais convencionais. Em particular, a potência média da densidade de potência do escalograma na banda de altas frequências mostrou ser estatisticamente o indicador de maior poder discriminatório (p < 0,05 para os 3 casos). CONCLUSÃO: A metodologia proposta mostrou-se capaz de distinguir entre indivíduos normais, chagásicos cardiopatas e chagásicos indeterminados. Os índices escalográficos propostos mostraram maior capacidade classificatória que os índices temporais tradicionais.<hr/>INTRODUCTION: Chagas' disease is an endemic rural disease prevalent in much of Central America and South America, and approximately half of the patients infected with the parasite Trypanosoma cruzi show no clinical, electrocardiographic and radiological cardiac involvement. This paper, however, proposes a technique for the diagnosis of Chagas' disease based on ECG signals, which extracts relevant information from these signals. METHODS: Two approaches are studied and implemented. Both approaches use heart rate variability (HRV) signals, and classification by a neural network, more specifically, the Kohonen self-organizing map. The HRV, which reflects sympathetic and parasympathetic autonomic neural modulation of the heart, is evaluated based on continuous series of RR intervals, calculated from 5-minute records of conventional ECG. In the first approach, statistical/temporal indexes obtained directly from the HRV signals are used as neural network inputs for training and testing of the classification method. In the second approach, derivative of Gaussian (DoG) wavelet scalograms are used to evaluate the HRV signals. Scalographic indexes are used as neural network inputs for training and testing of the algorithm. Kohonen topological maps are used to compare the ability of these HRV indicators of discriminating between patients with Chagas heart disease, Chagas indeterminate heart disease, and normal subjects. Conventional temporal indicators and indicators obtained from DoG scalograms are compared. RESULTS: Results of the application of the proposed methods to HRV signal databases, and performance comparisons, are presented. The results show that scalographic indicators have superior discriminatory power than conventional time-domain indicators. Based on an analysis of statistical significance, we show that the average power of the high-frequency band of the scalogram power spectral density is the indicator with greatest discriminatory power (p < 0,05 for all 3 cases). CONCLUSION: The proposed method has the ability to discriminate between normal subjects, subjects with Chagas cardiomyopathy, and subjects with the indeterminate form of Chagas' disease. It was observed that scalographic neural networks present greater discrimination ability than temporal neural networks. <![CDATA[<b>The implementation of the Neuroid in the Gate Control System leads to new ideas about pain processing</b>]]> INTRODUCTION: Several theories have been proposed to elucidate the mechanisms related with pain perception, among which, the Gate Control Theory (GCT) provides one of the most explicit explanations. This theory, as elegantly conceived, is unable to explain how the Frequency-Intensity (F-I) curves exhibited by Aβ- and C-fibres influence pain processing. In this paper, a novel neuron-model known as the Neuroid, which emphasizes the functional rather the physiological character of nerve cells, was used as the main building block to replicate the Gate Control System (GCS). METHODS: Two Aβ-fibre models were built: one model that preserved the paradoxical relation between the activation threshold and the F-I curve slope, and one model based on the hypothetical average response across the receptive field. RESULTS: The results suggest that the average response of the Aβ-fibres does not increase monotonically but reaches a plateau for high intensity stimuli. In addition, it was seen that activation of C-fibres does not necessarily imply the activation of projection neurons and, therefore, the onset of pain sensation. Also, we observed that the activation of Aβ-fibres may both, decrease and increase the activity of the projections neurons, an aspect which has not been directly described in previous works. CONCLUSION: Hypothetical implications arise as a consequence of the implementation of the Neuroid, specifically, about the correlation between the intensity of stimulation and the physiological pain threshold. <![CDATA[<b>Effect of laser vs LED in the near infrared region on the skeletal muscle activity</b>: <b>clinical study</b>]]> INTRODUÇÃO: Estudos têm demonstrado a efetividade do laser no infravermelho (IV) sobre a atividade musculoesquelética. Contudo, não foram observados estudos sobre os efeitos da radiação emitida por um LED (Light Emitting Diode) no IV sobre a atividade do músculo masseter (MM, importante músculo da mastigação), sendo este o objetivo do presente estudo. MÉTODOS: Participaram do estudo 10 voluntários, os quais foram analisados por eletromiografia (atividade muscular, força e tempo de fadiga) e nível de lactato sanguíneo (mmol/L) após terapia placebo, laser (GaAlAs, 780 nm) e LED (GaAlAs, 880 nm). Os sinais obtidos previamente antes de realizadas as terapias foram tidos como controle. Os parâmetros de irradiação (laser ou LED) foram: potência de saída de 0,02 W, densidade de energia de 4 J/cm², área do feixe de 0,2 cm². Foram irradiados 8 pontos sobre o MM, de forma perpendicular e transcutânea, com distância de 1 cm entre os pontos. RESULTADOS: A atividade muscular foi significativamente maior pós-terapia laser e LED em relação aos valores controle. Não foram encontradas diferenças significativas nos valores de força, tempos de fadiga e níveis de lactato sanguíneo pós-terapia placebo, laser ou LED, quando comparados aos valores controle. CONCLUSÃO: Os resultados obtidos no presente estudo sugerem a otimização da atividade muscular com uso de terapia laser ou LED, sem causar efeitos colaterais, como a elevação de força e aumento dos níveis de lactato.<hr/>INTRODUCTION: Studies have demonstrated the effectiveness of the infrared laser (IR) on the skelet al muscle activity. However, it was not found studies on the effects of radiation emitted by IR LED (Light Emitting Diode) on the activity of masseter muscle (MM, important muscle of mastication), the aim of the present study. METHODS: Ten volunteers were involved and their electromyography (muscle activity, strength and fatigue time) and blood lactate levels (mmol/L) were analyzed after placebo, laser (GaAlAs, 780 nm) and LED (GaAlAs, 880 nm) therapies. The signals obtained previously conducted before the therapies were taken as control. The irradiation parameters (laser or LED) were: output power of 0.02 W, energy density of 4 J/cm² and beam area of 0.2 cm². Eight points on the MM were irradiated in a perpendicular and transcutaneous form with a 1-cm distance between the points. RESULTS: Muscle activity was significantly higher after laser and LED therapies when compared to control. No significant differences were found in force, fatigue time and blood lactate levels after placebo therapy, laser or LED, when compared to control. CONCLUSION: The results suggest the optimization of muscle activity with the use of laser or LED therapy, without causing side effects such as the increase in the force and levels of lactate. <![CDATA[<b>Electromagnetic interference reduction by dynamic impedance balancing applied to biosensors</b>]]> INTRODUCTION: Electromagnetic interference caused by electric power lines adversely affects the signals of electronic instruments, especially those with low amplitude levels. This type of interference is known as common-mode interference. There are many methods and architectures used to minimize the influence of this kind of interference on electronic instruments, the most common of which is the use of band-reject filters. This paper presents the analysis, development, prototype and test of a new reconfigurable filter architecture for biomedical instruments, aiming to reduce the common-mode interference and preserve the useful signal components in the same frequency range as that of the noise, using the technique of dynamic impedance balancing. METHODS: The circuit blocks were mathematically modeled and the overall closed-loop transfer function was derived. Then the project was described and simulated in the VHDL_AMS language and also in an electronics simulation software, using discrete component blocks, with and without feedback. After theoretical analysis and simulation results, a prototype circuit was built and tested using as input a signal obtained from ECG electrodes. RESULTS: The results from the experimental circuit matched those from simulation: a 97.6% noise reduction was obtained in simulations using a sinusoidal signal, and an 86.66% reduction was achieved using ECG electrodes in experimental tests. In both cases, the useful signal was preserved. CONCLUSION: The method and its architecture can be applied to attenuate interferences which occur in the same frequency band as that of the useful signal components, while preserving these signals. <![CDATA[<b>Current perception threshold and reaction time in the assessment of sensory peripheral nerve fibers through sinusoidal electrical stimulation at different frequencies</b>]]> INTRODUCTION: The Perception Sensory Threshold (ST) for sinusoidal current stimuli at 5, 250, and 2,000 Hz is commonly used in the assessment of peripheral nerve fibers (C, Aδ, and Aβ, respectively). However, the neuroselectivity of these frequencies is far from consensus. In addition, Reaction Time (RT) measurements suggest that 2,000 Hz stimuli excite Aβ-fibers, 250 Hz Aβ- or Aδ-fibers, as well as 5 Hz Aβ-, Aδ- or C-fibers. Therefore, we suppose that the sinusoidal current neuroselectivity may be better observed if ST and RT parameters are jointly evaluated. In addition, we have investigated whether there are other sets of frequencies that could be used. METHODS: Thus this work investigates ST and RT for stimuli with frequency ranging from 1 to 3,000 Hz, on 28 healthy subjects aged from 19 to 44 years old (27.1±5.49). ST and RT dissimilarity among different frequencies was evaluated applying bi-dimensional Fisher Quadratic Discriminant. RESULTS: The lowest classification error (3.6%) was obtained for 1, 250, and 3,000 Hz. Error for 5, 250, and 2,000Hz was 16.7%. Stimulation frequency at 1 Hz evoked more sensations related to C-fibers (53% of reports) than to Aβ-fibers (36%). However, this behavior did not repeat itself at 5 Hz (only 21% of perceptions were related to C-fibers against 64% to Aβ-fibers). Sensations related to Aβ-fibers prevailed for the highest frequencies presented to the subjects (2,000 Hz - 82% and 3,000 Hz - 93%). Mean RT values showed a decreasing trend with frequency. CONCLUSION: These results suggest that frequencies 1, 250, and 3,000 Hz are more neuroselective than 5, 250, and 2,000 Hz for the evaluation of peripheral sensitive fibers. Furthermore, they show RT usefulness. <![CDATA[<b>Bond Graph modeling of the human esophagus and analysis considering the interference in the fullness of an individual by reducing mechanical esophageal flow</b>]]> INTRODUCTION: This paper shows a proposal for the mathematical modeling of the human esophagus using Bond Graph formalism and the interference in the satiation of an individual by way of an Esophageal Flow Controller (EFC). Therefore, it was evaluated that there is a significant change in fall time that affects the process of human satiety when the diameter of the esophagus is reduced. METHODS: As a first study, the analysis did not consider all hypothetical influences; only the most important variables were considered. RESULTS: As a result, the order of the final equation was x ∈ ℜ10. Furthermore, the designed model can be classified as linear, established and time invariant. CONCLUSION: The simulation results allow us to conclude that using the EFC in order to reduce the esophageal diameter in the upper esophageal sphincter area of 3cm by 1 cm implies that the system response will be slower; and consequently this reduction will interfere with satiety. <![CDATA[<b>3D image fusion using MRI/CT and infrared images</b>]]> INTRODUÇÃO: A termografia por imagem infravermelha (IR) é uma técnica para diagnóstico não-invasiva que permite a avaliação e quantificação de variações de temperatura na superfície da pele. Apesar de fornecer informações significativas para auxiliar no diagnóstico médico, esta técnica não permite avaliar det alhes anatômicos da região sendo analisada. Este artigo apresenta uma nova metodologia para realizar a fusão entre diferentes modalidades de imagens, tais como ressonância magnética (MRI) ou tomografia computadorizada por raios X (CT), juntamente com imagens de termografia infravermelha. MÉTODOS: Para a construção do modelo 3D, primeiramente são adquiridas as imagens por ressonância magnética (MRI) ou tomografia computadorizada (CT) e um conjunto de imagens térmicas da região de interesse. Em seguida, realiza-se o registro utilizando as projeções 2D (dos planos tomográficos) com as imagens térmicas. Após o registro, as imagens térmicas são combinadas e projetadas sobre o modelo 3D das imagens de MRI ou CT. RESULTADOS: O resultado é uma imagem 3D que combina informação de duas modalidades de imagens médicas diferentes. A combinação dessas duas modalidades de imagens médicas disponibiliza uma nova técnica de imagem 3D que agrupa informações anatômicas (MRI ou CT) e funcionais (variações de temperatura na superfície do corpo). CONCLUSÃO: Os resultados obtidos até o momento com essa nova metodologia indicam que ela pode auxiliar em diagnósticos médicos.<hr/>INTRODUCTION: Infrared (IR) thermal imaging is a non-invasive and diagnostic technique that allows evaluation and quantification based on the temperature changes of the skin surface. It provides significant information for clinical diagnosis; however this technique does not present the anatomical details of the region under inspection. In this work, it is presented an innovative image fusion method between different imaging modalities, such as magnetic resonance images (MRI) or X-ray computed tomography (CT), together with IR thermal images. METHODS: Firstly, in order to build the 3D model, the MRI or CT images and the IR thermal images (from the region of interest) are acquired. Then, based on the tomographic planes (image slices), the 2D projections are generated, and the IR images are registered accordingly. Next, the already registered IR set of images are combined and projected over the 3D MRI or CT model. RESULTS: The result is a 3D fused image that combines the information contents from the two different medical imaging modalities. The combination of these two medical imaging modalities offers a new 3D imaging technique that combines anatomical (MRI or CT) and functional (the body's surface temperature) information. CONCLUSION: The results obtained up to now with this new methodology indicate that it can aid in medical diagnosis. <![CDATA[<b>A comparison of left ventricular border detection techniques applied to 2D echocardiograms</b>]]> INTRODUCTION: Cardiology has been one of the most important areas of medicine. For several applications to diagnose the heart functions diseases the measurement of left ventricular (LV) cavity area and LV fractional area change are of vital necessity. To achieve this task, it is necessary to trace the border of left ventricle, which manual tracing is a tedious and time-consuming work. To solve this problem, many techniques to automate this border detection have been developed using the specialist tracing as gold standard. METHODS: The purpose of this approach is to analyze the features of the main techniques applied to left ventricle border detection in medical imaging. To facilitate understanding, the left ventricle border detection techniques are divided into three categories: image-based techniques, model-based techniques and pixel-based techniques. For each of the category, a literature review was made to get examples of the techniques applied to left ventricle border detection and to describe them. The result of this review is a comparative tablewhere the main features of each technique is compared. CONCLUSION: From the comparative table we can conclude that the not mentioning of many features of the techniques by the authors and the lack of a standardization of the evaluation techniques hamper a more satisfactory comparison.