Marcelino Monteiro de Andrade

Semi-automatic algorithm for construction of the left ventricular area variation curve over a complete cardiac cycle

BackgroundTwo-dimensional echocardiography (2D-echo) allows the evaluation of cardiac structures and their movements. A wide range of clinical diagnoses are based on the performance of the left ventricle. The evaluation of myocardial function is typically performed by manual segmentation of the ventricular cavity in a series of dynamic images. This process is laborious and operator dependent. The automatic segmentation of the left ventricle in 4-chamber long-axis images during diastole is troublesome, because of the opening of the mitral valve.MethodsThis work presents a method for segmentation of the left ventricle in dynamic 2D-echo 4-chamber long-axis images over the complete cardiac cycle. The proposed algorithm is based on classic image processing techniques, including time-averaging and wavelet-based denoising, edge enhancement filtering, morphological operations, homotopy modification, and watershed segmentation. The proposed method is semi-automatic, requiring a single user intervention for identification of the position of the mitral valve in the first temporal frame of the video sequence. Image segmentation is performed on a set of dynamic 2D-echo images collected from an examination covering two consecutive cardiac cycles.ResultsThe proposed method is demonstrated and evaluated on twelve healthy volunteers. The results are quantitatively evaluated using four different metrics, in a comparison with contours manually segmented by a specialist, and with four alternative methods from the literature. The methods intra- and inter-operator variabilities are also evaluated.ConclusionsThe proposed method allows the automatic construction of the area variation curve of the left ventricle corresponding to a complete cardiac cycle. This may potentially be used for the identification of several clinical parameters, including the area variation fraction. This parameter could potentially be used for evaluating the global systolic function of the left ventricle.

Análise eletromiográfica da pré-ativação muscular induzida por exercício monoarticular

OBJETIVO: Verificar se a execucao de um exercicio monoarticular de baixa intensidade para os extensores do joelho e uma estrategia eficaz para aumentar o numero de unidades motoras recrutadas no musculo vasto lateral durante a realizacao de um exercicio multiarticular subsequente. METODOS: Nove sujeitos saudaveis do sexo masculino (23,33±3,46 anos) foram submetidos a rotinas de treinamento nas quais os exercicios cadeira extensora e leg press 45° eram realizados em sequencia. Na rotina de baixa intensidade (R30), foram realizadas 15 extensoes unilaterais de joelho, seguidas de 15 repeticoes de leg press 45° com cargas de 30% e 60% de uma repeticao maxima (1-RM), respectivamente. Na rotina de alta intensidade (R60), a mesma sequencia foi executada, porem a carga dos dois movimentos foi de 60% de 1-RM. Uma serie simples de 15 repeticoes leg press 45° com carga de 60% de 1-RM foi utilizada como exercicio controle (RC). A eletromiografia de superficie foi registrada no musculo vasto lateral por meio de um arranjo linear de eletrodos. O valor RMS foi calculado para cada repeticao do leg press 45° e, a partir desses resultados, foram calculadas regressoes lineares. As inclinacoes das retas obtidas foram entao normalizadas pelos coeficientes lineares das equacoes de regressao e comparadas por meio da ANOVA de um fator para medidas repetidas. RESULTADOS: As inclinacoes observadas na rotina RC foram significativamente inferiores as de R30 e as de R60 (p<0,05). CONCLUSOES: Os resultados indicaram um recrutamento mais efetivo de unidades motoras nas rotinas de exercicio multiarticular precedidas de exercicio monoarticular. Artigo registrado na Australian New Zealand Clinical Trials Registry (ANZCTR) sob o numero ACTRN12609000413224.

Motor unit action potential conduction velocity estimated from surface electromyographic signals using image processing techniques

In surface electromyography (surface EMG, or S-EMG), conduction velocity (CV) refers to the velocity at which the motor unit action potentials (MUAPs) propagate along the muscle fibers, during contractions. The CV is related to the type and diameter of the muscle fibers, ion concentration, pH, and firing rate of the motor units (MUs). The CV can be used in the evaluation of contractile properties of MUs, and of muscle fatigue. The most popular methods for CV estimation are those based on maximum likelihood estimation (MLE). This work proposes an algorithm for estimating CV from S-EMG signals, using digital image processing techniques. The proposed approach is demonstrated and evaluated, using both simulated and experimentally-acquired multichannel S-EMG signals. We show that the proposed algorithm is as precise and accurate as the MLE method in typical conditions of noise and CV. The proposed method is not susceptible to errors associated with MUAP propagation direction or inadequate initialization parameters, which are common with the MLE algorithm. Image processing -based approaches may be useful in S-EMG analysis to extract different physiological parameters from multichannel S-EMG signals. Other new methods based on image processing could also be developed to help solving other tasks in EMG analysis, such as estimation of the CV for individual MUs, localization and tracking of innervation zones, and study of MU recruitment strategies.

Relationship between ventilatory threshold and muscle fiber conduction velocity responses in trained cyclists.

The relationship between surface electromyography (SEMG) amplitude and the ventilatory threshold has been extensively studied. However, previous studies of muscle fiber conduction velocity (MFCV) are scarce and present insufficient evidence concerning the relationship between MFCV and metabolic responses during cycling. Based on that fact, the purpose of this study is twofold: (1) to investigate the existence of a MFCV threshold (MFCVT) during cycling and (2) to verify if this possible breakpoint is correlated with the ventilatory threshold (VT) and the SEMG threshold (SEMGT). Eight trained male cyclists (age 36.0±9.7years) performed an incremental cycling test with initial workload of 150W gradually incremented by 20Wmin(-1) until the exhaustion. Gas analyses were conducted using a breath-by-breath open-circuit spirometry and SEMG were registered from vastus lateralis in each pedaling cycle with a linear array of electrodes. A bi-segmental linear regression computer algorithm was used to estimate VT, MFCVT and SEMGT respectively in the carbon dioxide production (VCO2), MFCV and electromyography root mean square (EMG RMS) curves. The one way ANOVA for repeated measures did not reveal any significant difference among VT (77.1±7.5% of VO2max), MFCVT (80.3±10.4% of VO2max) and SEMGT (81.9±11.7% of VO2max). The Bland and Altman procedure confirmed a good concordance between SEMGT and VT (Bias=5.5 of %VO2max) as well as MFCVT and VT (Bias=5.2 of %VO2max). The present findings suggest that muscle fiber conduction velocity threshold is a valid and reliable non-invasive tool to obtain information about ventilatory threshold in trained cyclists.

Automatic counting of Aedes Aegypti eggs deposited in ovitrap by algorithm of Digital Image Processing and Artificial Neural Network

According to World Health Organization, Dengue is identified as one of the main pandemic viral disease in tropical and semi-tropical countries in the world. A lot of researches have divulged that the use of ovitraps has itself shown a simple and inexpensive alternative for monitoring and controlling Dengue vector, Aedes Aegypti, but generally the process of counting Dengue mosquito eggs in ovitraps is performed manually. This paper describes a proposal for automatic counting of Aedes Aegypti eggs deposited in ovitraps by Digital Image Processing techniques associated to an Artificial Neural Network.

Development of an automatic identification algorithm for antibiogram analysis

Routinely, diagnostic and microbiology laboratories perform antibiogram analysis which can present some difficulties leading to misreadings and intra and inter-reader deviations. An Automatic Identification Algorithm (AIA) has been proposed as a solution to overcome some issues associated with the disc diffusion method, which is the main goal of this work. AIA allows automatic scanning of inhibition zones obtained by antibiograms. More than 60 environmental isolates were tested using susceptibility tests which were performed for 12 different antibiotics for a total of 756 readings. Plate images were acquired and classified as standard or oddity. The inhibition zones were measured using the AIA and results were compared with reference method (human reading), using weighted kappa index and statistical analysis to evaluate, respectively, inter-reader agreement and correlation between AIA-based and human-based reading. Agreements were observed in 88% cases and 89% of the tests showed no difference or a <4mm difference between AIA and human analysis, exhibiting a correlation index of 0.85 for all images, 0.90 for standards and 0.80 for oddities with no significant difference between automatic and manual method. AIA resolved some reading problems such as overlapping inhibition zones, imperfect microorganism seeding, non-homogeneity of the circumference, partial action of the antimicrobial, and formation of a second halo of inhibition. Furthermore, AIA proved to overcome some of the limitations observed in other automatic methods. Therefore, AIA may be a practical tool for automated reading of antibiograms in diagnostic and microbiology laboratories.

Parâmetros eletromiográficos em exercícios fatigantes realizados com diferentes tipos de resistência

En esta investigacion se pretendio estudiar los estandares electromiograficos de fatiga muscular durante la realizacion de ejercicio dinamico con resistencia variable (elastico) y resistencia fija (polea). Han participado voluntariamente diez varones entrenados. Se llevo a cabo dos contracciones voluntarias maximas (CVIM) de flexion de codo, cada cual de cinco segundos de duracion y dos minutos de intervalo entre las mismas. Despues los voluntarios hicieron la flexion unilateral del codo hasta sentirse cansados, y emplearon la resistencia fija y elastica con ritmo prestablecido de dos segundos para cada fase del movimiento. Se llevo a cabo la resistencia constante en la polea a 30% de la CVIM. Relativo a la resistencia elastica, el control de carga se basaba en una percepcion subjetiva del esfuerzo empleado por el participante. El orden del ejercicio fue aleatorio, y se registro la senal electromiografica del musculo biceps durante las contracciones. Desde la senal electromiografica relativa a cada ejecucion del movimiento se dibujo rectas de regresion lineal para las variables RMS y la frecuencia de potencia media (FPM). Se confirmo las inclinaciones de rectas normalizadas por el coeficiente lineal de las ecuaciones de regresion a traves de la prueba t pareada. No se observaron diferencias significantes entre los tipos de resistencia (elastica y polea). Los estandares electromiograficas de fatiga durante la practica de ejercicios de flexion de codo empleando resistencia elastica y polea no fueron distintos. La percepcion del esfuerzo durante la practica de ejercicio con elastico no trae consecuencias al estandar de senal electromiografico (RMS y FPM).

Estándares electromiográficos en ejercicios extenuantes empleando distintos tipos de resistencia

En esta investigacion se pretendio estudiar los estandares electromiograficos de fatiga muscular durante la realizacion de ejercicio dinamico con resistencia variable (elastico) y resistencia fija (polea). Han participado voluntariamente diez varones entrenados. Se llevo a cabo dos contracciones voluntarias maximas (CVIM) de flexion de codo, cada cual de cinco segundos de duracion y dos minutos de intervalo entre las mismas. Despues los voluntarios hicieron la flexion unilateral del codo hasta sentirse cansados, y emplearon la resistencia fija y elastica con ritmo prestablecido de dos segundos para cada fase del movimiento. Se llevo a cabo la resistencia constante en la polea a 30% de la CVIM. Relativo a la resistencia elastica, el control de carga se basaba en una percepcion subjetiva del esfuerzo empleado por el participante. El orden del ejercicio fue aleatorio, y se registro la senal electromiografica del musculo biceps durante las contracciones. Desde la senal electromiografica relativa a cada ejecucion del movimiento se dibujo rectas de regresion lineal para las variables RMS y la frecuencia de potencia media (FPM). Se confirmo las inclinaciones de rectas normalizadas por el coeficiente lineal de las ecuaciones de regresion a traves de la prueba t pareada. No se observaron diferencias significantes entre los tipos de resistencia (elastica y polea). Los estandares electromiograficas de fatiga durante la practica de ejercicios de flexion de codo empleando resistencia elastica y polea no fueron distintos. La percepcion del esfuerzo durante la practica de ejercicio con elastico no trae consecuencias al estandar de senal electromiografico (RMS y FPM).

Electromyographic parameters in fatiguing exercises performed with different types of resistance

En esta investigacion se pretendio estudiar los estandares electromiograficos de fatiga muscular durante la realizacion de ejercicio dinamico con resistencia variable (elastico) y resistencia fija (polea). Han participado voluntariamente diez varones entrenados. Se llevo a cabo dos contracciones voluntarias maximas (CVIM) de flexion de codo, cada cual de cinco segundos de duracion y dos minutos de intervalo entre las mismas. Despues los voluntarios hicieron la flexion unilateral del codo hasta sentirse cansados, y emplearon la resistencia fija y elastica con ritmo prestablecido de dos segundos para cada fase del movimiento. Se llevo a cabo la resistencia constante en la polea a 30% de la CVIM. Relativo a la resistencia elastica, el control de carga se basaba en una percepcion subjetiva del esfuerzo empleado por el participante. El orden del ejercicio fue aleatorio, y se registro la senal electromiografica del musculo biceps durante las contracciones. Desde la senal electromiografica relativa a cada ejecucion del movimiento se dibujo rectas de regresion lineal para las variables RMS y la frecuencia de potencia media (FPM). Se confirmo las inclinaciones de rectas normalizadas por el coeficiente lineal de las ecuaciones de regresion a traves de la prueba t pareada. No se observaron diferencias significantes entre los tipos de resistencia (elastica y polea). Los estandares electromiograficas de fatiga durante la practica de ejercicios de flexion de codo empleando resistencia elastica y polea no fueron distintos. La percepcion del esfuerzo durante la practica de ejercicio con elastico no trae consecuencias al estandar de senal electromiografico (RMS y FPM).

Método Automático para Morfometria de Membranas Neuronais Utilizando Perceptron de Múltiplas Camadas e Código de Cadeia Diferencial

Resumo—Neuropatias periféricas são alterações motoras e cognitivas em nervos que carecem de um diagnóstico rápido e eficiente para tratamento. Métodos de morfometria são normalmente utilizados para comparação de nervos saudáveis e patológicos, fazendo uso de análise de imagem para identificar, quantificar e extrair as caracterı́sticas de comparação. O objetivo do presente trabalho foi desenvolver uma técnica totalmente automatizada para extrair e medir as caracterı́sticas de axônios (especialmente o parâmetro G-ratio) presentes em imagens de cortes transversais do nervo ciático. Dessa forma, foi apresentado o algoritmo ADA utilizando uma rede Perceptron de Múltiplas Camadas (PMC) para classificar os objetos segmentados da imagem (N = 429 axônios) e o Código de Cadeia Diferencial de Freeman para separar os axônios. Os resultados dos G-ratios obtidos foram similares quando comparado com morfometria semiautomática (software Albeit) mostrando um erro absoluto médio de 1,85% e erro absoluto máximo de 2,80% (menor valor na literatura). A accuracy do ADA situou-se entre 80-86%.