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1
Content available Sequential separation of twin pregnancy electrocardiograms
Kotas M., Leski J. M., Wrobel J.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2016
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Vol. 64, nr 1
91--101
EN
We propose to tackle the problem of maternal abdominal electric signals decomposition with a combined application of independent component analysis and projective or adaptive filtering. The developed method is employed to process the four-channel abdominal signals recorded during twin pregnancy. These signals are complicated mixtures of the maternal ECG, the ECGs of the fetal twins and noise of various origin. Although the independent component analysis cannot separate the respective signals, the proposed combination of the methods deals with this task successfully. A simulation experiment confirms high efficiency of this approach.
2
Content available remote Wykorzystanie składowych głównych z normą L1 do filtracji projekcyjnej
Przybyła T.
Przegląd Elektrotechniczny
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2014
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R. 90, nr 5
134--137
PL
W niniejszej pracy zaprezentowano zmodyfikowaną metodę nieliniowej filtracji projekcyjnej. Zaproponowana modyfikacja dotyczy problemu wyznaczania podprzestrzeni projekcyjnej. W oryginalnej metodzie filtracji do wyznaczenia podprzestrzeni projekcyjnej wykorzystuje się metodę analizy składowych głównych (PCA), gdzie wykorzystywana jest norma L2. Norma L2 wrażliwa jest na próbki obce, stąd zaproponowano metodę PCA z normą L1 do wyznaczenia podprzestrzeni projekcyjnej jak również do wyznaczenia końcowej wartości próbki sygnału.
EN
The paper presents a modification of nonlinear state-space projections (NSSP) method. The proposed approach deals with the sub-space estimation problem. In the original NSSP method, the principal component analysis (PCA) is used for the sub-space determination. The classical PCA uses L2 norm which is sensitive to outliers. Thus, in this paper the L1 norm PCA is proposed for a sub-space determination as well as for the final value of the processed signal sample
3
Content available Projective filtering based on L1-norm PC
Przybyła T., Wróbel J., Pander T., Czabański R., Jeżewski J., Matonia A.
Journal of Medical Informatics & Technologies
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2013
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Vol. 22
79--86
EN
The paper presents a modification of nonlinear state-space projections (NSSP) method. The proposed approach deals with the sub-space estimation problem. In the original NSSP method, the principal component analysis (PCA) is used for the subspace determination. The classical PCA uses L2-norm. It is well known that the L2-norm is sensitive to outliers. Thus, in this paper the L1-norm PCA is proposed a subspace determination. In numerical experiments an analytic signal and real ECG signals are processed with the proposed method. The signals are contaminated with Gaussian distributed noise with different signal to noise ratio (SNR). Obtained results confirm the usefulness of the proposed modification.
4
Content available Separation of abdominal fetal electrocardiograms in twin pregnancy
Kotas M., Jeżewski J., Matonia A., Kupka T.
Journal of Medical Informatics & Technologies
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2008
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Vol. 12
83--89
EN
A combined application of independent component analysis and projective filtering of the time-aligned ECG beats is proposed to solve the problem of fetal ECG extraction from multi-channel maternal abdominal electric signals. The developed method is employed to process the four-channel abdominal signals recorded during twin pregnancy. The signals are complicated mixtures of the maternal ECG, the ECGs of the fetal twins and noise of other origin. The independent component analysis cannot separate the respective signals, but the proposed combination of the methods allows to suppress the maternal ECG and when the level of noise is low it leads to an effective separation of the twins' signals.
5
Content available remote Combined application of independent component analysis and projective filtering to fetal ECG extraction
Kotas M.
Biocybernetics and Biomedical Engineering
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2008
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Vol. 28, no. 1
75-93
EN
The maternal abdominal signals contain a few components: the dominant maternal ECG, various types of noise and the signal of the primary interest - the fetal ECG. In order to obtain the fetal ECG, the maternal signal should first be suppressed. In the paper, we propose a combined application of the independent component analysis and projective filtering of the time-aligned beats to solve the problem of the fetal ECG extraction from multi channel abdominal signals, when the number of the channels is low. The independent component analysis performs spatial decomposition of the signals. It often leads to a successful separation of the maternal and the fetal ECG. When the separation is not complete, projective filtering can be applied to enhance the partially separated maternal ECG. Then the maternal ECG contained in the respective channels can be reconstructed and subtracted from the original composite signals. This operation leads to the extraction of the fetal ECG in the respective channels. The signal can still be enhanced by the second application of the independent component analysis. The developed system operation is ilIustrated, and the results of its application are compared to the results achievable by application of the independent component analysis.
6
Content available remote Projective filtering of time-aligned beats for foetal ECG extraction
Kotas M.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2007
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Vol. 55, nr 4
331-339
EN
Extraction of the foetal electrocardiogram from single-channel maternal abdominal signals without disturbing its morphology is difficult. We propose to solve the problem by application of projective filtering of time-aligned ECG beats. The method performs synchronization of the beats and then employs the rules of principal component analysis to the desired ECG reconstruction. In the first stage, the method is applied to the composite abdominal signals, containing maternal ECG, foetal ECG, and various types of noise. The operation leads to maternal ECG enhancement and to suppression of the other components. In the next stage, the enhanced maternal ECG is subtracted from the composite signal, and this way the foetal ECG is extracted. Finally, the extracted signal is also enhanced by application of projective filtering. The influence of the developed method parameters on its operation is presented.
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