Wavelet Analysis on FECG Detection Using Two Electrodes System Device

Fetal electrocardiogram (FECG) signal detection during pregnancies is very useful in assessing fetal condition. Doppler ultrasound is very common in non-invasive FECG detection. It is safe, but inaccurate, highly sensitive to noise and the success of the measurement depends on the positioning of the probe. Recently, there are many research use non-invasive Ag/AgCl in FECG detection. However it involves large number of electrode during measurement. In addition, complex structures of signal processing are required. A study has been made on FECG detection using two electrodes biopotential device without reference electrode. Best possible electrode placement for maximum FECG waveforms detection has been identified. The FECG signals are successfully detected at 0.028Hz after processed using wavelet analysis

Wavelet denoising as a post-processing enhancement method for non-invasive foetal electrocardiography

Background and Objective: The detection of a clean and undistorted foetal electrocardiogram (fECG) from non-invasive abdominal recordings is an open research issue. Several physiological and instrumental noise sources hamper this process, even after that powerful fECG extraction algorithms have been used. Wavelet denoising is widely used for the improvement of the SNR in biomedical signal processing. This work aims to systematically assess conventional and unconventional wavelet denoising approaches for the post-processing of fECG signals by providing evidence of their effectiveness in improving fECG SNR while preserving the morphology of the signal of interest. Methods: The stationary wavelet transform (SWT) and the stationary wavelet packet transform (SWPT) were considered, due to their different granularity in the sub-band decomposition of the signal. Three thresholds from the literature, either conventional (Minimax and Universal) and unconventional, were selected. To this aim, the unconventional one was adapted for the first time to SWPT by trying different approaches. The decomposition depth was studied in relation to the characteristics of the fECG signal. Synthetic and real datasets, publicly available for benchmarking and research, were used for quantitative analysis in terms of noise reduction, foetal QRS detection performance and preservation of fECG morphology. Results: The adoption of wavelet denoising approaches generally improved the SNR. Interestingly, the SWT methods outperformed the SWPT ones in morphology preservation (p<0.04) and SNR (p<0.0003), despite their coarser granularity in the sub-band analysis. Remarkably, the Han et al. threshold, adopted for the first time for fECG processing, provided the best quality improvement (p<0.003). Conclusions: The findings of our systematic analysis suggest that particular care must be taken when selecting and using wavelet denoising for non-invasive fECG signal post-processing. In particular, despite the general noise reduction capability, signal morphology can be significantly altered on the basis of the parameterization of the wavelet methods. Remarkably, the adoption of a finer sub-band decomposition provided by the wavelet packet was not able to improve the quality of the processing

A phonocardiographic-based fiber-optic sensor and adaptive filtering system for noninvasive continuous fetal heart rate monitoring

This paper focuses on the design, realization, and verification of a novel phonocardiographic-based fiber-optic sensor and adaptive signal processing system for noninvasive continuous fetal heart rate (fHR) monitoring. Our proposed system utilizes two Mach-Zehnder interferometeric sensors. Based on the analysis of real measurement data, we developed a simplified dynamic model for the generation and distribution of heart sounds throughout the human body. Building on this signal model, we then designed, implemented, and verified our adaptive signal processing system by implementing two stochastic gradient-based algorithms: the Least Mean Square Algorithm (LMS), and the Normalized Least Mean Square (NLMS) Algorithm. With this system we were able to extract the fHR information from high quality fetal phonocardiograms (fPCGs), filtered from abdominal maternal phonocardiograms (mPCGs) by performing fPCG signal peak detection. Common signal processing methods such as linear filtering, signal subtraction, and others could not be used for this purpose as fPCG and mPCG signals share overlapping frequency spectra. The performance of the adaptive system was evaluated by using both qualitative (gynecological studies) and quantitative measures such as: Signal-to-Noise Ratio-SNR, Root Mean Square Error-RMSE, Sensitivity-S+, and Positive Predictive Value-PPV.Web of Science174art. no. 89

Non-Adaptive Methods of Fetal ECG Signal Processing

Tato diplomová práce se zabývá neadaptivními metodami zpracování břišního (abdominálního) plodového (fetálního) elektrokardiogramu (fEKG). Abdominální elektrokardiogram (aEKG) je tvořen směsí mateřského elektrokardiogramu (mEKG) a fEKG. Měřené fEKG je nositelem užitečných informací o stavu plodu, tj. plodová srdeční frekvence (fHR), morfologické informace a podobně. Nejprve se práce věnuje rozsáhlé rešerši zabývající se neadaptivními metodami extrakce fEKG a dále je vytvořen návrh popisující algoritmy zvolených metod. Primárně se tato práce zaměřuje na analýzu nezávislých komponent (ICA) a analýzu hlavních komponent (PCA). V této práci byla realizována softwarová aplikace pro verifikaci přesnosti extrahování fEKG. Funkčnost navrženého systému je otestována na syntetických i reálných datech z klinické praxe. Hodnocení kvality filtrace je provedena na základě stanovení tepové frekvence plodu (fHR) a odstupu signálu od šumu (SNR).This thesis deals with non-adaptive methods of processing abdominal fetal electrocardiogram (fECG). Abdominal electrocardiogram (aECG) is composed of a mixture of maternal electrocardiogram (mECG) and fECG. Measured fECG is a carrier of useful information about fetus, i.e. fetal heart rate (fHR), morphological information, etc. First part of this thesis is dedicated to a complex overview dealing with non-adaptive methods of extraction fECG and further developed a proposal describing algorithms of chosen methods. This work focuses primarily on independent component analysis (ICA) and principal component analysis (PCA). A software application was implement for verification of accuracy extraction fECG in this work. The functionality of the proposed system is tested on synthetic and real data from clinical practice. Evaluation of quality of filtration is performed based on the determination of fetal heart rate (fHR) and signal to noise ratio (SNR).450 - Katedra kybernetiky a biomedicínského inženýrstvívýborn

Estrazione non invasiva del segnale elettrocardiografico fetale da registrazioni con elettrodi posti sull’addome della gestante (Non-invasive extraction of the fetal electrocardiogram from abdominal recordings by positioning electrodes on the pregnant woman’s abdomen)

openIl cuore è il primo organo che si sviluppa nel feto, particolarmente nelle primissime settimane di gestazione. Rispetto al cuore adulto, quello fetale ha una fisiologia ed un’anatomia significativamente differenti, a causa della differente circolazione cardiovascolare. Il benessere fetale si valuta monitorando l’attività cardiaca mediante elettrocardiografia fetale (ECGf). L’ECGf invasivo (acquisito posizionando elettrodi allo scalpo fetale) è considerato il gold standard, ma l’invasività che lo caratterizza ne limita la sua applicabilità. Al contrario, l’uso clinico dell’ECGf non invasivo (acquisito posizionando elettrodi sull’addome della gestante) è limitato dalla scarsa qualità del segnale risultante. L’ECGf non invasivo si estrae da registrazioni addominali, che sono corrotte da differenti tipi di rumore, fra i quali l’interferenza primaria è rappresentata dall’ECG materno. Il Segmented-Beat Modulation Method (SBMM) è stato da me recentemente proposto come una nuova procedura di filtraggio basata sul calcolo del template del battito cardiaco. SBMM fornisce una stima ripulita dell’ECG estratto da registrazioni rumorose, preservando la fisiologica variabilità ECG del segnale originale. Questa caratteristica è ottenuta grazie alla segmentazione di ogni battito cardiaco per indentificare i segmenti QRS e TUP, seguito dal processo di modulazione/demodulazione (che include strecciamento e compressione) del segmento TUP, per aggiustarlo in modo adattativo alla morfologia e alla durata di ogni battito originario. Dapprima applicato all’ECG adulto al fine di dimostrare la sua robustezza al rumore, l’SBMM è stato poi applicato al caso fetale. Particolarmente significativi sono i risultati relativi alle applicazioni su ECGf non invasivo, dove l’SBMM fornisce segnali caratterizzati da un rapporto segnale-rumore comparabile a quello caratterizzante l’ECGf invasivo. Tuttavia, l’SBMM può contribuire alla diffusione dell’ECGf non invasiva nella pratica clinica.The heart is the first organ that develops in the fetus, particularly in the very early stages of pregnancy. Compared to the adult heart, the physiology and anatomy of the fetal heart exhibit some significant differences. These differences originate from the fact that the fetal cardiovascular circulation is different from the adult circulation. Fetal well-being evaluation may be accomplished by monitoring cardiac activity through fetal electrocardiography (fECG). Invasive fECG (acquired through scalp electrodes) is the gold standard but its invasiveness limits its clinical applicability. Instead, clinical use of non-invasive fECG (acquired through abdominal electrodes) has so far been limited by its poor signal quality. Non-invasive fECG is extracted from the abdominal recording and is corrupted by different kind of noise, among which maternal ECG is the main interference. The Segmented-Beat Modulation Method (SBMM) was recently proposed by myself as a new template-based filtering procedure able to provide a clean ECG estimation from a noisy recording by preserving physiological ECG variability of the original signal. The former feature is achieved thanks to a segmentation procedure applied to each cardiac beat in order to identify the QRS and TUP segments, followed by a modulation/demodulation process (involving stretching and compression) of the TUP segments to adaptively adjust each estimated cardiac beat to the original beat morphology and duration. SBMM was first applied to adult ECG applications, in order to demonstrate its robustness to noise, and then to fECG applications. Particularly significant are the results relative to the non-invasive applications, where SBMM provided fECG signals characterized by a signal-to-noise ratio comparable to that characterizing invasive fECG. Thus, SBMM may contribute to the spread of this noninvasive fECG technique in the clinical practice.INGEGNERIA DELL'INFORMAZIONEAgostinelli, AngelaAgostinelli, Angel

Abdominal Fetal Vectorcardiogram Extraction

Diplomová práce se v teoretické části zabývá prostudováním problematiky zpracování signálu, neinvazivními metodami snímání elektrokardiogramu plodu se zaměřením na metody jednokanálové. Cílem bylo vybrat vhodnou metodu k extrakci plodového EKG, která dokáže plodové EKG extrahovat v dostatečné kvalitě k vykreslení plodového vektorkardiogramu. Po provedené rešerši byla vybrána metoda šablonového odčítání (Template substraction) pro velmi dobré hodnocení extrakce. Cílem praktické části je ověření, zda lze neinvazivním způsobem získat elektrokardiogramy plodu ve třech osách tak, aby mohly být použity pro vykreslení plodového vektorkardiogramu. Dále je pak praktická část pak zaměřena na vygenerování syntetických abdominálních signálů, předzpracování a zpracování abdominálních signálů s následnou extrakcí plodového EKG pěti metodami šablonového odčítání. Experiment byl proveden na umělých datech, generovaných z databáze FECGSYNDB, která umožňuje nastavit velké množství parametrů signálu, vzájemných poměrů mateřského a plodového EKG a různé typy artefaktů. Součástí experimentu je vyhodnocení úspěšnosti jednotlivých metod extrakce porovnáním s originálním plodovým EKG, pomocí střední kvadratické odchylky MSE, směrodatné odchylky RMSE a korelace v každé ose snímání. Toto porovnání bylo umožněno použitím syntetických dat, která při generování abdominálního signálu používá původní, ničím nezkreslený signál plodového EKG. Ten byl při generování uložen a později po extrakci plodového EKG z abdominálního signálu použit ke vzájemnému porovnání. Nejlepší výsledky dosahuje podle MSE metoda SUZANNA, nejlepší korelace mezi původním a extrahovaným signálem je u metody CERUTTI, nelze však říci, že by obě metody byly výrazně lepší než ostatní. Významný rozdíl byl v časové náročnosti, kdy metoda PCA vyžaduje na extrakci čas asi 25x až 40x delší než ostatní metody. Metoda LP při extrakci v určitých místech na konci signálu vykazovala singularitu, což se projevilo i na extrahovaném signálu.In the theoretical part, the diploma thesis deals with the study of signal processing, non-invasive methods of fetal electrocardiogram scanning with a focus on single-channel methods. The aim was to select a suitable method for fetal ECG extraction, which can extract fetal ECG in sufficient quality to plot the fetal vector cardiogram. After the search, the template substraction method was chosen for a very good extraction evaluation. The aim of the practical part is to verify whether the electrocardiograms of the fetus in three axes can be obtained in a non-invasive way so that they can be used to plot the fetal vector cardiogram. Furthermore, the practical part is focused on the generation of synthetic abdominal signals, preprocessing and processing of abdominal signals with subsequent extraction of the fetal ECG by five methods of template subtraction. The experiment was performed on artificial data generated from the FECGSYNDB database, which allows to set a large number of signal parameters, maternal and fetal ECG ratios and different types of artifacts. A part of the experiment is the evaluation of the success of each extraction method by comparison with the original fetal ECG, using the mean square deviation (MSE), the standard deviation (RMSE) and the correlation in each scanning axis. This comparison was allowed by using synthetic data that uses the original, undistorted fetal ECG signal to generate the abdominal signal. This original signal was stored during generation and later, after extraction of the fetal ECG from the abdominal signal, it was used for comparison. According to MSE, the SUZANNA method achieves the best results; the best correlation between the original and extracted signal is by the CERUTTI method, but it cannot be claimed that both methods are significantly better than the others. There was a significant difference in time. The PCA method requires about 25 to 40 times longer extraction time than other methods. The LP method showed a singularity at certain points at the end of the signal, which was also reflected in the extracted signal.450 - Katedra kybernetiky a biomedicínského inženýrstvívýborn

A novel algorithm based on ensemble empirical mode decomposition for non-invasive fetal ECG extraction

Non-invasive fetal electrocardiography appears to be one of the most promising fetal monitoring techniques during pregnancy and delivery nowadays. This method is based on recording electrical potentials produced by the fetal heart from the surface of the maternal abdomen. Unfortunately, in addition to the useful fetal electrocardiographic signal, there are other interference signals in the abdominal recording that need to be filtered. The biggest challenge in designing filtration methods is the suppression of the maternal electrocardiographic signal. This study focuses on the extraction of fetal electrocardiographic signal from abdominal recordings using a combination of independent component analysis, recursive least squares, and ensemble empirical mode decomposition. The method was tested on two databases, the Fetal Electrocardiograms, Direct and Abdominal with Reference Heartbeats Annotations and the PhysioNet Challenge 2013 database. The evaluation was performed by the assessment of the accuracy of fetal QRS complexes detection and the quality of fetal heart rate determination. The effectiveness of the method was measured by means of the statistical parameters as accuracy, sensitivity, positive predictive value, and F1-score. Using the proposed method, when testing on the Fetal Electrocardiograms, Direct and Abdominal with Reference Heartbeats Annotations database, accuracy higher than 80% was achieved for 11 out of 12 recordings with an average value of accuracy 92.75% [95% confidence interval: 91.19-93.88%], sensitivity 95.09% [95% confidence interval: 93.68-96.03%], positive predictive value 96.36% [95% confidence interval: 95.05-97.17%] and F1-score 95.69% [95% confidence interval: 94.83-96.35%]. When testing on the Physionet Challenge 2013 database, accuracy higher than 80% was achieved for 17 out of 25 recordings with an average value of accuracy 78.24% [95% confidence interval: 73.44-81.85%], sensitivity 81.79% [95% confidence interval: 76.59-85.43%], positive predictive value 87.16% [95% confidence interval: 81.95-90.35%] and F1-score 84.08% [95% confidence interval: 80.75-86.64%]. Moreover, the non-invasive ST segment analysis was carried out on the records from the Fetal Electrocardiograms, Direct and Abdominal with Reference Heartbeats Annotations database and achieved high accuracy in 7 from in total of 12 records (mean values mu < 0.1 and values of +/- 1.96 sigma < 0.1).Web of Science168art. no. e025615

Fetal Electrocardiogram Processing Using Template Subtraction Methods

Cílem diplomové práce je zpracování plodového elektrokardiogramu za pomocí šablonového odčítání. Na začátku práce je probrána problematika vývoje kardiovaskulárního systému plodu a poté se práce věnuje rešerši na metody šablonového odčítání a jejich matematickému popisu. Praktická část je zaměřena na zpracování signálu využitím šablonových metod s následnou detekcí jednotlivých plodových QRS komplexů. Používané metody šablonového odčítání v diplomové práci jsou TS, TS – Cerutti, TS – Suzanna, TS – PCA a TS – LP. Extrahované signály fEKG jsou na konci vykreslovány v grafickém uživatelském rozhraní prostředí Matlab.The aim of the diploma thesis is to process fetal electrocardiogram using template subtraction. At the beginning of the thesis, the issue of the development of the fetal cardiovascular systém is discussed and then thesis is devoted to a review for template subtraction methods and their mathematical description. The practical part is focused on signal processing using template methods with subsequent detection of individual fetal QRS complexes. Evaluation of fetal ECG extraction is based on fetal heart rate. Method used in thesis are TS, TS – Cerutti, TS – Suzanna, TS – PCA and TS – LP. The extracted fECG signals are plotted in graphical user interface in Matlab environment.450 - Katedra kybernetiky a biomedicínského inženýrstvívýborn

A Comparative Study of the Efficacy of Non-Invasive Fetal ECG Extraction Methods using Data from Clinical Practice

Hlavní náplní této práce je srovnávací studie hybridních extrakčních metod neivazivního fetáního elektrokardiogramu. Pro přesnější stanovení efektivity metod je zde představen nový evaluační systém fungující na podobném principu, jaký je využíván u přístrojů v klinické praxi. Úspěšnost extrakce je v této práci stanovena určením délek jednotlivých segmentů elektrokardiografické křivky a vzájemným porovnáváním jejich morfologie. Protože posouzení účinnosti extrakce na syntetických datech je často zavádějící, byly v této práci metody porovnávány výhradně dle dosažených výsledků na reálných signálech z klinické praxe. Metody jsou srovnávány s referencí na základě Bland-Altmanovy analýzy a stanovení statistických parametrů ACC, Se, PPV a F1.This thesis introduces a comparative study of hybrid methods for extraction of non-invasive fetal electrocardiograms (fECGs). In order to assess the effectiveness of each method more precisely, a new evaluation system is proposed. The system is inspired by the devices used in clinical practice; the efficacy is determined by evaluating the lengths of the individual segments of the fECG waveform and comparing their morphology. Since the assessment of the extraction quality using synthetic data is often misleading, the dataset used in this thesis was composed solely from the real signals from the clinical practice. The direct fECG was used as the reference; the statistics includes Bland-Altman analysis and determination of quality parameters such as ACC, Se, PPV, and F1.450 - Katedra kybernetiky a biomedicínského inženýrstvívýborn