Designing a Synthetic ECG Signal in MATLAB

Import 05/08/2014Hlavním cílem této práce je vytvoření syntetického EKG signálu v prostředí MATLAB na základě analýzy Fourierových řad. Jednotlivé elementy EKG jsou aproximovány matematickým modelem, který je popsán a vysvětlen v teoretické části této práce. Vzniká tak model EKG signálu a to jak fyziologického, tak také některých jeho vybraných patologií. Na specifickém příkladu je tak ukázán návod na aproximaci a vytvoření syntetického modelu jakéhokoli periodického signálu. U vytvořeného syntetického EKG signálu je navíc uživateli dána možnost nastavení amplitudy a délky některých jeho vybraných parametrů. Touto metodikou jsme schopni vytvořit syntetický model EKG signálu s parametry zvolenými podle potřeby, který můžeme využít například jako základ pro kontrolu funkčnosti detektoru délky jednotlivých vln či intervalů apod. Druhá část této práce je věnovaná dalším tématům spojeným s EKG, jako je simulace rušení a následná filtrace EKG nebo transformace signálu do frekvenční oblasti. Vše je provedeno u reálných EKG signálů načtených uživatelem.The main point of this thesis is to design a synthetic signal using MATLAB based on the theory of Fourier series. Each ECG element is approximated by the mathematical model which is described in the theoretical part of the thesis. This way the synthetic model is made – either physiological or pathological. A practical example shows an instruction of any periodical signal approximation. There is also an option for the user to set the size of amplitude or the length of some ECG parameters. By this method it is possible to create a synthetic model of ECG signal with specific parameters chosen for the user’s needs, which can be used for example to control the function of the ECG length and amplitude size detector. The second part focuses on the different topics related with ECG as the simulation of the noise and filtering ECG or the transformation of the signal to the frequency domain. Both applied to the real ECG signals chosen by the user.450 - Katedra kybernetiky a biomedicínského inženýrstvívýborn

Hybrid methods based on empirical mode decomposition for non-invasive fetal heart rate monitoring

This study focuses on fetal electrocardiogram (fECG) processing using hybrid methods that combine two or more individual methods. Combinations of independent component analysis (ICA), wavelet transform (WT), recursive least squares (RLS), and empirical mode decomposition (EMD) were used to create the individual hybrid methods. Following four hybrid methods were compared and evaluated in this study: ICA-EMD, ICA-EMD-WT, EMD-WT, and ICA-RLS-EMD. The methods were tested on two databases, the ADFECGDB database and the PhysioNet Challenge 2013 database. Extraction evaluation is based on fetal heart rate (fHR) determination. Statistical evaluation is based on determination of correct detection (ACC), sensitivity (Se), positive predictive value (PPV), and harmonic mean between Se and PPV (F1). In this study, the best results were achieved by means of the ICA-RLS-EMD hybrid method, which achieved accuracy(ACC) > 80% at 9 out of 12 recordings when tested on the ADFECGDB database, reaching an average value of ACC > 84%, Se > 87%, PPV > 92%, and F1 > 90%. When tested on the Physionet Challenge 2013 database, ACC > 80% was achieved at 12 out of 25 recordings with an average value of ACC > 64%, Se > 69%, PPV > 79%, and F1 > 72%.Web of Science8512185120

Novel hybrid extraction systems for fetal heart rate variability monitoring based on non-invasive fetal electrocardiogram

This study focuses on the design, implementation and subsequent verification of a new type of hybrid extraction system for noninvasive fetal electrocardiogram (NI-fECG) processing. The system designed combines the advantages of individual adaptive and non-adaptive algorithms. The pilot study reviews two innovative hybrid systems called ICA-ANFIS-WT and ICA-RLS-WT. This is a combination of independent component analysis (ICA), adaptive neuro-fuzzy inference system (ANFIS) algorithm or recursive least squares (RLS) algorithm and wavelet transform (WT) algorithm. The study was conducted on clinical practice data (extended ADFECGDB database and Physionet Challenge 2013 database) from the perspective of non-invasive fetal heart rate variability monitoring based on the determination of the overall probability of correct detection (ACC), sensitivity (SE), positive predictive value (PPV) and harmonic mean between SE and PPV (F1). System functionality was verified against a relevant reference obtained by an invasive way using a scalp electrode (ADFECGDB database), or relevant reference obtained by annotations (Physionet Challenge 2013 database). The study showed that ICA-RLS-WT hybrid system achieve better results than ICA-ANFIS-WT. During experiment on ADFECGDB database, the ICA-RLS-WT hybrid system reached ACC > 80 % on 9 recordings out of 12 and the ICA-ANFIS-WT hybrid system reached ACC > 80 % only on 6 recordings out of 12. During experiment on Physionet Challenge 2013 database the ICA-RLS-WT hybrid system reached ACC > 80 % on 13 recordings out of 25 and the ICA-ANFIS-WT hybrid system reached ACC > 80 % only on 7 recordings out of 25. Both hybrid systems achieve provably better results than the individual algorithms tested in previous studies.Web of Science713178413175

Adaptive Signal Processing Techniques for Extracting Abdominal Fetal Electrocardiogram

Import 03/11/2016Tato diplomová práce se zabývá problematikou snímání plodového elektrokardiogramu z transabdominálního záznamu. Ten by se v budoucnu mohl stát velmi účinným a nezbytným nástrojem v monitorování a diagnostice ohrožených plodů v průběhu těhotenství a během porodu. Největším problémem, se kterým se tento způsob monitorace potýká, je velké množství nežádoucích složek, které jsou snímány společně s užitečným signálem, zejména pak mateřský elektrokardiogram. Autorka se zaměřuje zejména na využití adaptivních metod pro extrakci plodového elektrokardiogramu z takto zarušeného transabdominálního záznamu. Tato práce obsahuje mimo jiné také obsáhlé shrnutí této poměrně nové problematiky, klasifikaci a popis vybraných adaptivních metod a zejména návrh a realizaci adaptivního systému pro potlačování „nežádoucího“ mateřského elektrokardiogramu. Ověření funkčnosti tohoto systému bylo provedeno na syntetických i reálných datech.This thesis focuses on the fetal electrocardiogram recorded transabdominally. This method could become very efficient and essential tool in monitoring and diagnosing endangered fetuses during the pregnancy and the delivery. The greatest challenge connected with this kind of monitoring is the amount of noise that is recorded within the desired signal. This thesis aims at the use of adaptive methods for extracting fetal electrocardiogram from such abdominal signal. This thesis includes among others an extensive summary of this relatively new issue, classification and description of selected linear adaptive methods, and in particular, the design and the implementation of adaptive system for suppressing the ‚undesirable‘ maternal electrocardiogram.450 - Katedra kybernetiky a biomedicínského inženýrstvívelmi dobř

Optimization of adaptive filter control parameters for non-invasive fetal electrocardiogram extraction

This paper is focused on the design, implementation and verification of a novel method for the optimization of the control parameters of different hybrid systems used for non-invasive fetal electrocardiogram (fECG) extraction. The tested hybrid systems consist of two different blocks, first for maternal component estimation and second, so-called adaptive block, for maternal component suppression by means of an adaptive algorithm (AA). Herein, we tested and optimized four different AAs: Adaptive Linear Neuron (ADALINE), Standard Least Mean Squares (LMS), Sign-Error LMS, Standard Recursive Least Squares (RLS), and Fast Transversal Filter (FTF). The main criterion for optimal parameter selection was the F1 parameter. We conducted experiments using real signals from publicly available databases and those acquired by our own measurements. Our optimization method enabled us to find the corresponding optimal settings for individual adaptive block of all tested hybrid systems which improves achieved results. These improvements in turn could lead to a more accurate fetal heart rate monitoring and detection of fetal hypoxia. Consequently, our approach could offer the potential to be used in clinical practice to find optimal adaptive filter settings for extracting high quality fetal ECG signals for further processing and analysis, opening new diagnostic possibilities of non-invasive fetal electrocardiography.Web of Science174art. no. e026680

Fiber-optic interferometric sensor for monitoring automobile and rail traffic

This article describes a fiber-optic interferometric sensor and measuring scheme including input-output components for traffic density monitoring. The proposed measuring system is based on the interference in optical fibers. The sensor, based on the Mach-Zehnder interferometer, is constructed to detect vibration and acoustic responses caused by vehicles moving around the sensor. The presented solution is based on the use of single-mode optical fibers (G.652.D and G.653) with wavelength of 1550 nm and laser source with output power of 1 mW. The benefit of this solution lies in electromagnetic interference immunity and simple implementation because the sensor does not need to be installed destructively into the roadway and railroad tracks. The measuring system was tested in real traffic and is characterized by detection success of 99.27% in the case of automotive traffic and 100% in the case of rail traffic.Web of Science2662995298

A comparative study of single-channel signal processing methods in fetal phonocardiography

Fetal phonocardiography is a non-invasive, completely passive and low-cost method based on sensing acoustic signals from the maternal abdomen. However, different types of interference are sensed along with the desired fetal phonocardiography. This study focuses on the comparison of fetal phonocardiography filtering using eight algorithms: Savitzky-Golay filter, finite impulse response filter, adaptive wavelet transform, maximal overlap discrete wavelet transform, variational mode decomposition, empirical mode decomposition, ensemble empirical mode decomposition, and complete ensemble empirical mode decomposition with adaptive noise. The effectiveness of those methods was tested on four types of interference (maternal sounds, movement artifacts, Gaussian noise, and ambient noise) and eleven combinations of these disturbances. The dataset was created using two synthetic records r01 and r02, where the record r02 was loaded with higher levels of interference than the record r01. The evaluation was performed using the objective parameters such as accuracy of the detection of S1 and S2 sounds, signal-to-noise ratio improvement, and mean error of heart interval measurement. According to all parameters, the best results were achieved using the complete ensemble empirical mode decomposition with adaptive noise method with average values of accuracy = 91.53% in the detection of S1 and accuracy = 68.89% in the detection of S2. The average value of signal-to-noise ratio improvement achieved by complete ensemble empirical mode decomposition with adaptive noise method was 9.75 dB and the average value of the mean error of heart interval measurement was 3.27 ms.Web of Science178art. no. e026988

Detection of atrial fibrillation episodes in long-term heart rhythm signals using a support vector machine

Atrial fibrillation (AF) is a serious heart arrhythmia leading to a significant increase of the risk for occurrence of ischemic stroke. Clinically, the AF episode is recognized in an electrocardiogram. However, detection of asymptomatic AF, which requires a long-term monitoring, is more efficient when based on irregularity of beat-to-beat intervals estimated by the heart rate (HR) features. Automated classification of heartbeats into AF and non-AF by means of the Lagrangian Support Vector Machine has been proposed. The classifier input vector consisted of sixteen features, including four coefficients very sensitive to beat-to-beat heart changes, taken from the fetal heart rate analysis in perinatal medicine. Effectiveness of the proposed classifier has been verified on the MIT-BIH Atrial Fibrillation Database. Designing of the LSVM classifier using very large number of feature vectors requires extreme computational efforts. Therefore, an original approach has been proposed to determine a training set of the smallest possible size that still would guarantee a high quality of AF detection. It enables to obtain satisfactory results using only 1.39% of all heartbeats as the training data. Post-processing stage based on aggregation of classified heartbeats into AF episodes has been applied to provide more reliable information on patient risk. Results obtained during the testing phase showed the sensitivity of 98.94%, positive predictive value of 98.39%, and classification accuracy of 98.86%.Web of Science203art. no. 76

Fiber-optic cardiorespiratory monitoring and triggering in magnetic resonance imaging

During the past decades, fiber-optic technology has become a very popular tool for vital signs monitoring. Thanks to its advantageous properties, such as noninvasiveness, biocompatibility, and resistance to electromagnetic interferences, this methodology started to be explored under the conditions of a magnetic resonance (MR) environment. This review article presents the motivation and possibilities of using fiber-optic sensors (FOSs) in MR environment and summarizes the studies dealing with experimental validation of their compatibility with MR. Several aspects of the presented issue are highlighted and discussed, such as suitability of the fiber-optic approach for MR triggering, precision of vital sign detection, development of sensor designs, and its application to patient's body. From the literature review, it can be concluded that FOSs have promising future in the field of cardiorespiratory monitoring in MR environment. This is mainly due to their advantages originating from sensing mechanical signals instead of electrical ones, which makes them resistant to MR interference and extrasystoles. Moreover, these sensors are easy to use, reusable, and suitable for combined monitoring. However, there are several shortcomings that should be solved in future research before introducing them to clinical practice, namely, signal's delay or optimal placement of sensors.Web of Science71art. no. 400531

Fetal electrocardiograms, direct and abdominal with reference heartbeat annotations

Monitoring fetal heart rate (FHR) variability plays a fundamental role in fetal state assessment. Reliable FHR signal can be obtained from an invasive direct fetal electrocardiogram (FECG), but this is limited to labour. Alternative abdominal (indirect) FECG signals can be recorded during pregnancy and labour. Quality, however, is much lower and the maternal heart and uterine contractions provide sources of interference. Here, we present ten twenty-minute pregnancy signals and 12 five-minute labour signals. Abdominal FECG and reference direct FECG were recorded simultaneously during labour. Reference pregnancy signal data came from an automated detector and were corrected by clinical experts. The resulting dataset exhibits a large variety of interferences and clinically significant FHR patterns. We thus provide the scientific community with access to bioelectrical fetal heart activity signals that may enable the development of new methods for FECG signals analysis, and may ultimately advance the use and accuracy of abdominal electrocardiography methods.Web of Science71art. no. 20