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Sensors (Basel) ; 21(17)2021 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-34502748


One of the most common sleep disorders is sleep apnea. It manifests itself by episodes of shallow breathing or pauses in breathing during the night. Diagnosis of this disease involves polysomnography examination, which is expensive. Alternatively, diagnostic doctors can be supported with recordings from the in-home polygraphy sensors. Furthermore, numerous attempts for providing an automated apnea episodes annotation algorithm have been made. Most of them, however, do not distinguish between apnea and hypopnea episodes. In this work, a novel solution for epoch-based annotation problem is presented. Utilizing an architecture based on the long short-term memory (LSTM) networks, the proposed model provides locations of sleep disordered breathing episodes and identifies them as either apnea or hypopnea. To achieve this, special pre- and postprocessing steps have been designed. The obtained labels can be then used for calculation of the respiratory event index (REI), which serves as a disease severity indicator. The input for the model consists of the oronasal airflow along with the thoracic and abdominal respiratory effort signals. Performance of the proposed architecture was verified on the SHHS-1 and PhysioNet Sleep databases, obtaining mean REI classification error of 9.24/10.52 with standard deviation of 11.61/7.92 (SHHS-1/PhysioNet). Normal breathing, hypopnea and apnea differentiation accuracy is assessed on both databases, resulting in the correctly classified samples percentage of 86.42%/84.35%, 49.30%/58.28% and 68.20%/69.50% for normal breathing, hypopnea and apnea classes, respectively. Overall accuracies are 80.66%/82.04%. Additionally, the effect of wake periods is investigated. The results show that the proposed model can be successfully used for both episode classification and REI estimation tasks.

Síndromes da Apneia do Sono , Humanos , Polissonografia , Respiração , Taxa Respiratória , Sono , Síndromes da Apneia do Sono/diagnóstico
Sensors (Basel) ; 19(19)2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31546656


In this paper an efficient method for signal change detection in multidimensional data streams is proposed. A novel tensor model is suggested for input signal representation and analysis. The model is built from a part of the multidimensional stream by construction of the representing orthogonal tensor subspaces, computed with the higher-order singular value decomposition (HOSVD). Parts of the input data stream from successive time windows are then compared with the model, which is either updated or rebuilt, depending on the result of the proposed statistical inference rule. Due to processing of the input signal tensor in the scale-space, the thumbnail like output is obtained. Because of this, the method is called a thumbnail tensor. The method was experimentally verified on annotated video databases and on real underwater sequences. The results show a significant improvement over other methods both in terms of accuracy as well as in speed of operation time.

Sensors (Basel) ; 19(13)2019 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-31262074


Real signals are usually contaminated with various types of noise. This phenomenon has a negative impact on the operation of systems that rely on signals processing. In this paper, we propose a tensor-based method for speckle noise reduction in the side-scan sonar images. The method is based on the Tucker decomposition with automatically determined ranks of factoring tensors. As verified experimentally, the proposed method shows very good results, outperforming other types of speckle-noise filters.

Artigo em Inglês | MEDLINE | ID: mdl-21095742


In this paper a computer vision system is proposed for automatic examination of implant placements based on the maxillary radiograph images. To find rotated and scale changed implants the system does template matching in the extended log-polar space. Matching is proposed to be performed in the anisotropic scale-space, starting from the coarse level. The precise location of an implant is then refined based on the fine level of this space. The two processes are additionally controlled by the contour images which delineate exact positions of implants and other dental works.

Implantação Dentária/instrumentação , Implantação Dentária/métodos , Implantes Dentários , Maxila/diagnóstico por imagem , Radiografia/métodos , Algoritmos , Anisotropia , Meios de Contraste/farmacologia , Processamento Eletrônico de Dados , Desenho de Equipamento , Humanos , Teste de Materiais , Modelos Estatísticos , Reprodutibilidade dos Testes , Software
Int J Neural Syst ; 18(4): 339-45, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18763733


In this paper we propose efficient color segmentation method which is based on the Support Vector Machine classifier operating in a one-class mode. The method has been developed especially for the road signs recognition system, although it can be used in other applications. The main advantage of the proposed method comes from the fact that the segmentation of characteristic colors is performed not in the original but in the higher dimensional feature space. By this a better data encapsulation with a linear hypersphere can be usually achieved. Moreover, the classifier does not try to capture the whole distribution of the input data which is often difficult to achieve. Instead, the characteristic data samples, called support vectors, are selected which allow construction of the tightest hypersphere that encloses majority of the input data. Then classification of a test data simply consists in a measurement of its distance to a centre of the found hypersphere. The experimental results show high accuracy and speed of the proposed method.

Inteligência Artificial , Percepção de Cores/fisiologia , Redes Neurais de Computação , Reconhecimento Automatizado de Padrão , Algoritmos , Simulação por Computador , Modelos Lineares , Processamento de Sinais Assistido por Computador , Fatores de Tempo