Перегляд за Автор "Ivanushkina, N. H."

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    Estimation of Multiple Cardiac Cells’ Action Potentials From Extracellular Field Potentials
    (КПІ ім. Ігоря Сікорського, 2023) Shpotak, M. O.; Ivanushkina, N. H.; Ivanko, K. O.; Prokopenko, Y. V.
    Modern biomedical technologies use a combination of microelectrode array (MEA) systems and artificially grown cells to study disease mechanisms and test drug effects. MEA systems measure extracellular field potentials (FPs) of cell cultures or tissues, but they cannot record intracellular action potentials (APs) without some modifications or additional devices, limiting the depth of electrophysiological analysis. One of the possible solutions to the inability of MEA systems to measure APs is to mathematically reconstruct them using recorded FPs. However, accurately reconstructing APs of multiple cells is challenging task, which is complicated by many factors such as the number of cells, synchronicity of their APs, identification of their electrophysiological parameters, and noise. This paper aims to address the mathematical problem of AP synchronicity, asynchronicity and partial synchronicity between multiple cells. In this study, mathematical techniques were employed to derive a system of equations capable of reconstructing the APs of N cells simultaneously, using the FPs recorded with N + 1 electrodes. The equations take into account the number of cells, synchronicity and variation of their APs and specific electrical properties of the cells and the medium. In numerical experiments the equations were applied to reconstruct APs from FPs for cases with different types of synchronicity in noise-free and noisy conditions. The reconstructed APs, when combined with recorded FPs, expand the number of electrophysiological characteristics available for cardiotoxicity assessment in MEA systems.
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    The Method of Preprocessing of ECG Signals for Detecon of Atrial and Ventricular Late Potenals
    (КПІ ім. Ігоря Сікорського, 2023) Mnevets, A. V.; Ivanushkina, N. H.
    This article is aimed at analyzing and improving the methods of preprocessing ECG signals for the task of detecting low-amplitude regular components. This study analyzed the main advantages and disadvantages of existing ECG signal preprocessing methods for the detection of late ventricular and atrial potentials. Based on this analysis, a cardiac cycle averaging method was proposed in order to increase the accuracy of detection of late potentials by various algorithms and improve the quality of preprocessing of the ECG signal aimed at detection of low-amplitude components. The main feature of the proposed method is the division of a large number of cardiocycles for averaging into smaller aggregates (epochs), and the subsequent application of linear matrix decomposition to suppress irregular inclusions. Also, when dividing into epochs, it can be used overlapping. It can reduce the difference between epochs, and increase the number of cardiocycles for averaging. The use of this approach allows to minimize irregular inclusions in the ECG signal and increase the accuracy of the selection of low-amplitude late potentials. In addition, the division into epochs and overlapping makes possible to avoid blurring of low-amplitude high-frequency components during averaging as a result of heart rate variability, as well as to improve the quality of averaging with a reduced number of cardiocycles. To test the proposed method, various approaches were used to assess the ECG signal preprocessing. Mostly, we compared the cardiac cycles obtained as a result of different averaging algorithms and the proposed method with the template. To test the averaging method, an artificial ECG signal was developed with existing noise, late ventricular and atrial potentials, heart rate variability, and a high-amplitude component that occurs at a random location every two heartbeats. The template cardiac cycle was obtained from the original artificial signal without any distortion or noise. Firstly, we visually compared and evaluated different averaging methods with the template. Secondly, we calculated the similarity metrics of the late potentials on the averaged cardiac cycle with the late potentials on the template signal. Based on these metrics, the curves of dependence of the similarity values on the amplitude of late potentials on the ECG signal were calculated. Thirdly, we evaluated the impact of the proposed aver aging method on the classification results of various machine learning algorithms on real ECG signals with available late potentials. The overall testing result showed that the proposed averaging method is able to reproduce the morphology of low-amplitude regular components by 10-30% more accurately and improve the classification accuracy by 5-12%.