A morphology-preserving algorithm for denoising of EMG-contaminated ECG signals

Goal: Clinical interpretation of an electrocardiogram (ECG) can be detrimentally affected by noise. Removal of the electromyographic (EMG) noise is particularly challenging due to its spectral overlap with the QRS complex. The existing EMG-denoising algorithms often distort signal morphology, thus obscuring diagnostically relevant information. Methods: Here, a new iterative regeneration method (IRM) for efficient EMG-noise suppression is proposed. The main hypothesis is that the temporary removal of the dominant ECG components enables extraction of the noise with the minimum alteration to the signal. The method is validated on SimEMG database of simultaneously recorded reference and noisy signals, MIT-BIH arrhythmia database and synthesized ECG signals, both with the noise from MIT Noise Stress Test Database. Results: IRM denoising and morphology-preserving performance is superior to the wavelet- and FIR-based benchmark methods. Conclusions : IRM is reliable, computationally non-intensive, fast and applicable to any number of ECG channels recorded by mobile or standard ECG devices

Autocorrelation for denoising biomedical signals

Photoplethysmography (PPG) has become a standard method for assessment of blood volume changes in clinical care and heart rate in home care [1]. Besides the pulse rate, PPG pulse forms carry signatures of diagnostically relevant events in cardiac cycle and can be used to estimate arterial stiffness. Extraction of these features requires removal of noise, motion artifacts and the superimposed slow varying signals, such as that from breathing, from the signal while preserving pulse morphology. However, modern filtering methods often fail to reproduce all signal features. Here, we propose a novel noise–removal method based on autocorrelation. Autocorrelation is a well-known method used in optics, mainly for estimating the duration of ultrashort laser pulses. We used autocorrelation to remove the noise and baseline wander (BLW) from a set of bioelectrical signals, namely electrocardiogram (ECG) and PPG. These signals comprise pulses (or beats) repeated in time but with slight changes. When we record several such beats and by averaging them get a noise-free signal with distorted morphology. However, taking a few steps further, namely subtracting the average from the original signal and filtering the difference in the frequency domain, enables the noise and BLW extraction from the original signal and reproduction of a faithful noise-free signal. We tested this method on the private ECG database, where added BLW component is from public MIT-NST database, and on the private PPG signals. The results show the superiority of our approach compared to the conventional cubic spline (CSP) method.XVI Photonics Workshop : Book of abstracts; March 12-15, 2023; Kopaonik, Serbi

Uticaj sastava disperzne sredine oksidnih solova na elektrokatalitičku aktivnost RuO2-TiO2/Ti anoda dobijenih sol-gel postupkom

The influence of the addition of methanol, ethanol, 1-propanol and 2-propanol to the dispersing medium of a mixture of RuO2 and TiO2 sols on the electrochemically active surface area for proton exchange, as well as on the electrocatalytic activity for the chlorine evolution reaction (CER) of RuO2-TiO2/Ti electrode obtained by sol-gel procedure was investigated. The electrochemically active surface area was examined by cyclic voltammetry, while the analysis of the activity for the CER was performed by polarization measurements. The stability of the obtained anode coatings was also checked by an accelerated stability test. The anode properties depend on the number of C atoms in the alcohol molecule, as well as on the elapsed time between the preparation of the sols/alcohol mixture and its application onto the titanium support. The addition of alcohol increased the activity of the anodes for the CER, compared to those prepared without the addition, but their stability was smaller.U radu je ispitivan uticaj metanola, etanola, 1-propanola i 2-propanola, dodatih u disperznu sredinu RuO2-TiO2 smeše solova, na elektrohemijski aktivnu površinu i elektrokatalitičku aktivnost za reakciju izdvajanja hlora (RIH) RuO2-TiO2/Ti elektroda dobijenih sol-gel postupkom. Elektrohemijski aktivna površina ispitivana je metodom ciklične voltametrije, dok je aktivnost za RIH ispitivana polarizacionim merenjima. Takođe je i ubrzanim testom stabilnosti ispitivana postojanost dobijenih oksidnih prevlaka. Utvrđeno je da osobine dobijenih anoda zavise od broja ugljenikovih atoma u molekulu dodatog alkohola i vremena proteklog od pripreme smeše alkohola i solova do nanošenja smeše na titanski nosač. Uočeno je da dodatak alkohola prouzrokuje povećanje aktivnosti anoda za RIH u odnosu na anode dobijene bez dodavanja alkohola. Istovremeno, anode dobijene dodavanjem alkohola su manje stabilne od anoda dobijenih bez dodavanja alkohola

Coronary Artery Occlusion Detection Using 3-Lead ECG System Suitable for Credit Card-Size Personal Device Integration

Background Early coronary occlusion detection by portable personal device with limited number of electrocardiographic (ECG) leads might shorten symptom-to-balloon time in acute coronary syndromes. Objectives The purpose of this study was to compare the accuracy of coronary occlusion detection using vectorcardgiographic analysis of a near-orthogonal 3-lead ECG configuration suitable for credit card-size personal device integration with automated and human 12 lead ECG interpretation. Methods The 12-lead ECGs with 3 additional leads (“abc”) using 2 arm and 2 left parasternal electrodes were recorded in 66 patients undergoing percutaneous coronary intervention prior to (“baseline”, n = 66), immediately before (“preinflation”, n = 66), and after 90-second balloon coronary occlusion (“inflation”, n = 120). Performance of computer-measured ST-segment shift on vectorcardgiographic loops constructed from “abc” and 12 leads, standard 12-lead ECG, and consensus human interpretation in coronary occlusion detection were compared in “comparative” and “spot” modes (with/without reference to “baseline”) using areas under ROC curves (AUC), reliability, and sensitivity/specificity analysis. Results Comparative “abc”-derived ST-segment shift was similar to two 12-lead methods (vector/traditional) in detecting balloon coronary occlusion (AUC = 0.95, 0.96, and 0.97, respectively, P = NS). Spot “abc” and 12-lead measurements (AUC = 0.72, 0.77, 0.68, respectively, P = NS) demonstrated poorer performance (P < 0.01 vs comparative measurements). Reliability analysis demonstrated comparative automated measurements in “good” agreement with reference (preinflation/inflation), while comparative human interpretation was in “moderate” range. Spot automated and human reading showed “poor” agreement. Conclusions Vectorcardiographic ST-segment analysis using baseline comparison of 3-lead ECG system suitable for credit card-size personal device integration is similar to established 12-lead ECG methods in detecting balloon coronary occlusion

A database of simultaneously recorded ECG signals with and without EMG noise

Goal: Noise on recorded electrocardiographic (ECG) signals may affect their clinical interpretation. Electromyographic (EMG) noise spectrally coincides with the QRS complex, which makes its removal particularly challenging. The problem of evaluating the noise-removal techniques has commonly been approached by algorithm testing on the contaminated ECG signals constructed ad hoc as an additive mixture of a noise-free ECG signal and noise. Consequently, there is an absence of a unique/standard database for testing and comparing different denoising methods. We present a SimEMG database recorded by a novel acquisition method that allows for direct recording of the genuine EMG-noise-free and -contaminated ECG signals. The database is available as open source

Long-period grating sensors for the measurement of apexcardiogram

Apexcardiogram (ACG) represents record of low-frequency vibrations of the precordium caused by heart contractions. The information obtained from ACG is mostly related to left ventricular contractions. The most common position for its measurement is in parasternal area of chest wall, above the apex of the heart. The measurement of ACG can provide date significant in timing of systolic events of the cardiac cycle. Particulary, ACG is used as aid in timing of the opening snap of the cardiac valves, for the identification of the exact timing of the third (S3) and fourth heart sounds (S4) and for early diagnosis of the mitral valve stenosis or regurgitation [1]. The frequently used methods for non-invasively recording of ACG include using of electro manometer sensor, piezoelectric microphone sensor and crystal-microphone sensor for measuring mechanical displacements of chest wall [2]. The disadvantages of these sensors are potential noise caused by electrical interference and technical difficulties in their application on body surface. The goal of this study is to evaluate possibility of using long-period grating (LPG) sensor as potential non-invasive method for ACG recording. The advantages of utilizing LPG sensors are their low cost, utilization simplicity, and insensitivity to electrical interference. The study protocol includes measurements on group of healthy volunteers utilizing a single LPG sensor. LPG sensor is positioned in paternal area of chest wall, above the apex of the heart and fixed with the elastic bandage. It is used as a sensor of mechanical pulsation on the body surface. All healthy volunteers are asked to hold their breath in mid-expiration phase for at least 10 seconds in order to avoid the interference of the ACG with a breathing signal. Our results show that we are able to record signals with morphology of normal ACG repeatably on each healthy volunteer, and with the significant signal-to-noise ratio. Hence, we can conclude that LPG sensors can be used for recording ACG by measuring mechanical low-frequency vibrations of the precordium on the body surface above the apex of the heart.VII International School and Conference on Photonics : PHOTONICA2019 : Abstracts of Tutorial, Keynote, Invited Lectures, Progress Reports and Contributed Papers; August 26-30; Belgrad

Optical fiber grating sensors for the measurement of superficial temporal artery pulsations

The measurement of arterial blood pressure waveform can provide important data about arterial health, from which general cardiovascular health can be estimated. The arterial blood pressure wave is created by heart contraction which then propagates along the arterial tree. Along its path, the pressure wave causes the distention of arterial walls which consequently can be palpated and measured as micro-movements on the surface of the body. The most frequently used places on the body for recording of the blood pressure waveform are in the fingers and above the radial artery on the wrist. However, since waveforms recorded on the periphery of the body alter from central ones, there is the necessity for non-invasive measurements closer to the ascending aorta [1]. The purpose of this study was to evaluate the possibility of utilizing the superficial temporal artery (STA) as a potential candidate for obtaining arterial waveform recorded non-invasively by fiber grating sensors. The STA is a terminal branch of the external carotid artery and it represents the major artery of the head. The sites over the main branch (near the ear) and the frontal branch of the STA (near ocular area) are easily accessible ones with negligible amounts of fat and muscle tissues. Assessment tests were carried out by using fiber grating sensors (fiber Bragg grating (FBG) and long-period grating (LPG)) as sensors of the arterial distention movement. Here we were focused on the possibility to record the STA pulsations in healthy volunteers when the sensors were just placed on the skin over the STA and fixed with the tape or elastic bandage. Our results show that with this type of application, LPG technology outperformed FBG in a sense of sensitivity and signal to noise ratio. The reason possibly lies in the fact that cladding modes generated by an LPG are much more affected by arterial distention than back-propagating core modes of an FBG [2]. By using LPG sensor we were able to record STA pulsations in all volunteers.VII International School and Conference on Photonics : PHOTONICA2019 : Abstracts of Tutorial, Keynote, Invited Lectures, Progress Reports and Contributed Papers; August 26-30; Belgrad

Deep Learning Approach for Highly Specific Atrial Fibrillation and Flutter Detection based on RR Intervals

Atrial fibrillation (AF) and atrial flutter (AFL) represent atrial arrhythmias closely related to increasing risk for embolic stroke, and therefore being in the focus of cardiologists. While the reported methods for AF detection exhibit high performances, little attention has been given to distinguishing these two arrhythmias. In this study, we propose a deep neural network architecture, which combines convolutional and recurrent neural networks, for extracting features from sequence of RR intervals. The learned features were used to classify a long term ECG signals as AF, AFL or sinus rhythm (SR). A 10-fold cross-validation strategy was used for choosing an architecture design and tuning model hyperparameters. Accuracy of 88.28 %, with the sensitivities of 93.83%, 83.60% and 83.83% for SR, AF and AFL, respectively, was achieved. After choosing optimal network structure, the model was trained on the entire training set and finally evaluated on the blindfold test set which resulted in 89.67% accuracy, and 97.20%, 94.20%, and 77.78% sensitivity for SR, AF and AFL, respectively. Promising performances of the proposed model encourage continuing development of highly specific AF and AFL detection procedure based on deep learning. Distinction between these two arrhythmias can make therapy more efficient and decrease the recovery time to normal heart rhythm. © 2019 IEEE.Conference of 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC 2019 ; Conference Date: 23 July 2019 Through 27 July 2019; Conference Code:15254

Uticaj sastava disperzne sredine oksidnih solova na elektrokatalitičku aktivnost RuO2-TiO2/Ti anoda dobijenih sol-gel postupkom

The influence of the addition of methanol, ethanol, 1-propanol and 2-propanol to the dispersing medium of a mixture of RuO2 and TiO2 sols on the electrochemically active surface area for proton exchange, as well as on the electrocatalytic activity for the chlorine evolution reaction (CER) of RuO2-TiO2/Ti electrode obtained by sol-gel procedure was investigated. The electrochemically active surface area was examined by cyclic voltammetry, while the analysis of the activity for the CER was performed by polarization measurements. The stability of the obtained anode coatings was also checked by an accelerated stability test. The anode properties depend on the number of C atoms in the alcohol molecule, as well as on the elapsed time between the preparation of the sols/alcohol mixture and its application onto the titanium support. The addition of alcohol increased the activity of the anodes for the CER, compared to those prepared without the addition, but their stability was smaller.U radu je ispitivan uticaj metanola, etanola, 1-propanola i 2-propanola, dodatih u disperznu sredinu RuO2-TiO2 smeše solova, na elektrohemijski aktivnu površinu i elektrokatalitičku aktivnost za reakciju izdvajanja hlora (RIH) RuO2-TiO2/Ti elektroda dobijenih sol-gel postupkom. Elektrohemijski aktivna površina ispitivana je metodom ciklične voltametrije, dok je aktivnost za RIH ispitivana polarizacionim merenjima. Takođe je i ubrzanim testom stabilnosti ispitivana postojanost dobijenih oksidnih prevlaka. Utvrđeno je da osobine dobijenih anoda zavise od broja ugljenikovih atoma u molekulu dodatog alkohola i vremena proteklog od pripreme smeše alkohola i solova do nanošenja smeše na titanski nosač. Uočeno je da dodatak alkohola prouzrokuje povećanje aktivnosti anoda za RIH u odnosu na anode dobijene bez dodavanja alkohola. Istovremeno, anode dobijene dodavanjem alkohola su manje stabilne od anoda dobijenih bez dodavanja alkohola

Uticaj sastava disperzne sredine oksidnih solova na elektrokatalitičku aktivnost RuO2-TiO2/Ti anoda dobijenih sol-gel postupkom

The influence of the addition of methanol, ethanol, 1-propanol and 2-propanol to the dispersing medium of a mixture of RuO2 and TiO2 sols on the electrochemically active surface area for proton exchange, as well as on the electrocatalytic activity for the chlorine evolution reaction (CER) of RuO2-TiO2/Ti electrode obtained by sol-gel procedure was investigated. The electrochemically active surface area was examined by cyclic voltammetry, while the analysis of the activity for the CER was performed by polarization measurements. The stability of the obtained anode coatings was also checked by an accelerated stability test. The anode properties depend on the number of C atoms in the alcohol molecule, as well as on the elapsed time between the preparation of the sols/alcohol mixture and its application onto the titanium support. The addition of alcohol increased the activity of the anodes for the CER, compared to those prepared without the addition, but their stability was smaller.U radu je ispitivan uticaj metanola, etanola, 1-propanola i 2-propanola, dodatih u disperznu sredinu RuO2-TiO2 smeše solova, na elektrohemijski aktivnu površinu i elektrokatalitičku aktivnost za reakciju izdvajanja hlora (RIH) RuO2-TiO2/Ti elektroda dobijenih sol-gel postupkom. Elektrohemijski aktivna površina ispitivana je metodom ciklične voltametrije, dok je aktivnost za RIH ispitivana polarizacionim merenjima. Takođe je i ubrzanim testom stabilnosti ispitivana postojanost dobijenih oksidnih prevlaka. Utvrđeno je da osobine dobijenih anoda zavise od broja ugljenikovih atoma u molekulu dodatog alkohola i vremena proteklog od pripreme smeše alkohola i solova do nanošenja smeše na titanski nosač. Uočeno je da dodatak alkohola prouzrokuje povećanje aktivnosti anoda za RIH u odnosu na anode dobijene bez dodavanja alkohola. Istovremeno, anode dobijene dodavanjem alkohola su manje stabilne od anoda dobijenih bez dodavanja alkohola