Sleep is a growing area of research interest in medicine and neuroscience. Actually, one major concern is to find a correlation between several physiologic variables and sleep stages. There is a scientific agreement on the characteristics of the five stages of human sleep, based on EEG analysis. Nevertheless, manual stage classification is still the most widely used approach. This work proposes a new automatic sleep classification method based on unsupervised feature classification algorithms recently developed, and on EEG entropy measures. This scheme extracts entropy metrics from EEG records to obtain a feature vector. Then, these features are optimized in terms of relevance using the Q-α algorithm. Finally, the resulting set of features is entered into a clustering procedure to obtain a final segmentation of the sleep stages. The proposed method reached up to an average of 80% correctly classified stages for each patient separately while keeping the computational cost low.

En este artículo se propone una metodología para soporte al diagnóstico en análisis de lesión de rodilla, teniendo en cuenta que dichas lesiones son comunes y se producen por diferentes causas, y donde su diagnóstico y tratamiento se realiza por medio de valoraciones por parte de un profesional en el área, que dependiendo de su criterio puede conllevar a exámenes invasivos y/o de alto costo. El sistema emplea señales electromiográficas de superficie (EMGS) y señales de goniometría, analizadas con métodos de análisis de señales en el espacio de tiempo-frecuencia mediante espectrograma y transformada wavelet. Como técnica de aprendizaje de máquina se emplean redes neuronales artificiales, por medio de un perceptrón multicapa. Las señales EMG fueron tomadas en cuatro músculos internos-externos asociados a la articulación, por medio de exámenes físicos de flexión y extensión, en el cual se registró además la goniometría en el plano sagital. Con este sistema se obtuvieron rendimientos superiores al 80% en la efectividad como medida de desempeño, convirtiéndose esta propuesta en una solución objetiva, que puede darle más elementos de juicio al profesional para el diagnóstico.

A method that improves the feature selection stage for non-supervised analysis of Holter ECG signals is presented. The method corresponds to WPCA approach developed mainly in two stages. First, the weighting of the feature set through a weight vector based on M-inner product as distance measure and a quadratic optimization function. The second one is the linear projection of weighted data using principal components. In the clustering stage, some procedures are considered: estimation of the number of groups, initialization of centroids and grouping by means a soft clustering algorithm. In order to decrease the procedure computational cost, segment analysis, grouping contiguous segments and establishing union and exclusion criteria per each cluster, is carried out. This work is focused to classify cardiac arrhythmias into 5 groups, according to the standard of the AAMI (ANSI/AAMI EC57:1998/ 2003). To validate the method, some recordings from MIT/BIH arrhythmia database are used. By employing the labels of each recording, the performance is assessed with supervised measures (Se = 90.1%, Sp = 98.9% y Cp = 97.4%), enhancing other works in the literature that do not take into account all heartbeat types.