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Semi-Blind Source Separation for fetal ECG extraction

The thesis deals with the extraction of the fetal Electrocardiogram (fECG) signal from non-invasive ECG measurements recorded from the abdomen of a pregnant woman. As in adults, the well-being of a fetus can be assessed from the fetal ECG (fECG) signal.
Abdominal ECG recordings can be considered as a summation of different contributes: the maternal ECG (mECG) signal, the fECG signal and interference signals like power line interference, electromyography signals, motion artifacts, etc. It would be extremely useful to find a method for reliably extract the fECG signal. Many authors have been interested to this problem and nowadays various promising methods, mainly based on signal processing, were presented. However, due to the complexity of the problem none of them provided definitive results.
Extraction of fECG from a signals mixture suggest the application of independent component analysis (ICA), also because the assumption that the sources in the measurements (fECG, mECG, other noises) are independent is well verified at the short time scale used for separation. Indeed, Independent Component Analysis or Blind Source Separation (BSS) method were developed to separate mixtures of sources without any a-priori information. However, known limitation of this technique concern the number of recording needed to effectively separate signals and statistical property of the signals. ICA has several variants, in particular fastICA and JADE algorithms were considered in previous studies about this research topics.
In this thesis I proposed a methodology to overcome the limitation of ICA signal processing mainly the need of a high number of abdominal recordings, which limit the clinical application of the methodologies.
I tried to use all the a priori information about the interferences superimposed to the fECG (i.e. maternal ECG, baseline wander, power line interference, etc.) in order to preprocess abdominal recording before applying ICA separation algorithms. Therefore, the proposed method took the name of Semi-Blind Source Separation.
Real abdominal recording from pregnant women were employed to test effectiveness of the proposed methodology.
Experimental results shown that it is possible to obtain reliable fECG information (both heart rhythms and signal morphology) using only four abdominal leads.

Mostra/Nascondi contenuto.
Introduction 1 1 INTRODUCTION The electrocardiogram (ECG) signal is one of the most commonly employed physiological signals. ECG signal obtained by measuring the differences of potential generated by electrical activity of the heart through electrodes placed generally on the skin of the patient. The ECG can provide valuable clinical information. The monitoring and analysis of the ECG is a useful technique to support diagnosis of many cardiac diseases. There are two main significant features of the ECG useful in clinical diagnoses: its morphology and its timing (R-R interval is the reciprocal of the heart rate). As in adults, the well-being of a fetus can be assessed from the fetal ECG (fECG) signal during pregnancy. The fECG signal can be obtained from electrical measurements on the maternal abdomen. However, the abdominal ECG signal consists of a combination of the maternal ECG (mECG) signal, the fECG signal, and interference signals. As the amplitude of the mECG signal is typically much larger than the fECG signal and the interference signals can be comparable to fECG amplitude, fetal electrocardiography has been disregarded in clinical application for years. Signal processing can offer an effective solution to provide reliable fECG signals, also for clinical application. Nowadays due to the difficulty for the extraction of the fECG, a technique widely accepted to assessing the conditions of well-being of the fetus is the registration of the Fetal Heart Rate (FHR). In particular, the Doppler Ultrasound Cardiotocography (US-CTG) is the most widespread clinic prenatal methodic to assess fetal well-being. Nowadays, the fECG is considered as a possible alternative or complementary technique to the US-CTG. In order to obtain more and more detailed information on the well-being of the fetus is important to make more frequent and long-lasting FHR recordings; but the Doppler Ultrasound Cardiotography is an active technique, i.e. involves an administration of energy and it may create some problems for long-term monitoring. It is also worth mentioning that the US-CTG only provide fetal heart rate information and this it is not enough to provide certain diagnosis of some ominous fetal states. Indeed, fECG can provide more information than the mere heart rate by analyzing its morphology.

Laurea liv.II (specialistica)

Facoltà: Ingegneria

Autore: Federico Conte Contatta »

Composta da 145 pagine.

 

Questa tesi ha raggiunto 237 click dal 19/04/2011.

 

Consultata integralmente una volta.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.