Adaptive Filtering and Artificial Intelligence Methods on Fetal Ecg Extraction
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Journal of Critical Reviews ISSN- 2394-5125 Vol 7, Issue 7, 2020 ADAPTIVE FILTERING AND ARTIFICIAL INTELLIGENCE METHODS ON FETAL ECG EXTRACTION Dr. M. Pradeepa1,Dr. S. Kumaraperumal2 1Assistant Professor (Sr.), School of Information Technology, Vellore Institute of Technology, Vellore, India. Email: [email protected] 2Sr. Assistant Professor , Xavier Institute of Management & Entrepreneurship, Bangalore, India. Email: [email protected] Corresponding Author Email ID [email protected] Received: 11.02.2020 Revised: 19.03.2020 Accepted: 23.04.2020 Abstract Above 30 percent of infant’s death occur due to heart problem like congenital heart disease during 2004 in United States of America. Every year, one in 125 infants is born with heart imperfection. To address these problems, early identification of cardiac anomalies and consistent monitoring of fetal heart can support Pediatric Cardiologist and Obstetrics to take necessary care on time to prescribe medicines and take precautionary measures during gestation period, delivery and/or after birth. Majority of cardiac abnormalities contain some symptoms in the cardiac electrical signal morphology. Electrocardiography gives more information in measuring cardiac signals compare to sonographic measurement. However, in non-invasive heartbeat recording by fetal Electrocardiogram (ECG) application Electrocardiography has its limitation due to low signal- noise ratio where impeding bio-signals are too stronger than fetal electrocardiogram signals. Various adaptive filtering and Artificial intelligence techniques are applied to solve this complex problem. The complex real world problems need a combination of knowledge, skills, and techniques from various sources as an intelligent system. That intelligent system should possess expertise of human, adjust itself to changing environment and learn to improve on its own. Keywords: Artificial Intelligent, Adaptive Filter, Adaptive Neuro-Fuzzy Inference System (ANFIS), Kalman filtering (KF). © 2019 by Advance Scientific Research. This is an open-access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) DOI: http://dx.doi.org/10.31838/jcr.07.07.47 INTRODUCTION signals from more than one channels utilized to extract the fetal Fetus health condition is monitored by many methods where ECG components recorded at noisy environment. To extract Electrocardiography is one of the frequently used methods which desired signal many types of adaptive filters are used, in which shows the fetus heart’s electrical activities. some of them are presented below. Generally, an invasive or non-invasive method of recording of Time sequenced adaptive filtering has been recommended by Fetal ECG (FECG) is performed. In invasive method of recording, Ferrara & Widrow [4] for FECG enrichment. They identified the the electrode has to be placed on the scalp of the fetus to non-stationary fetal ECG signal having recurring statistical measure the ECG but the electrode has to be passed through characteristics. The Least Mean Square (LMS) adaptive filter can mother’s womb which creates difficulties to the mother [1] and able to follow up such fast changing non stationarities, hence an also possible only at the later stage of pregnancy period. The adaptive filter have to be designed with rapidly varying impulse non-invasive method of recording does not provide any trouble response to improve the performance of the extraction. The to the mother because the electrode has to be placed on mothers’ method uses many sets of hyper parameters to adapt for fast abdomen to measure the ECG of the fetus. changing impulse response. In order to adapt for fast changing impulse response, the method requires more abdominal signals There are several approaches proposed to record the fetal ECG and also timely identification of estimated fetal pulse. Apart from under non- invasive method which uses either a single lead or the above requirements the technique needs prior information of two leads or multiple leads. For a single lead method of fetal ECG positions. The time sequenced adaptive filtering recording, only one electrode is positioned on the mothers’ provides more accurate results compared to classical LMS abdomen, two lead systems uses two electrodes which have to be adaptive filter. The overall performance of the adaptive filter is positioned on the chest and abdomen and multiple lead systems increased when the number of channel input is increased. The require multiple electrodes to record the fetal ECG. main advantage of this approach is that the prior knowledge of There are several complications in non-invasive method of signals’ power spectrum is not required. But, the time sequenced recording fetal ECG, because the recording is not directly taken method need the estimation for the timely identification of the from the fetus which is measured on the abdomen, hence the pulse, to synchronize the filter regeneration and the fetal cardiac fetal ECG is to be extracted from signal contaminated by multiple cycles. They stated the future direction to enhance the results by sources of interferences. Apart from these sources of finding better method to locate the fetal pulse positions in order interferences the low signal level of fetal ECG [2] and the spectral to make this approach with recordings having lower SNR. overlapping of mother ECG and fetal ECG [3] makes the Kam & Cohen [5] identified a method to find the fetal ECG using extraction more critical. Infinite Impulse Response (IIR) filtering technique and Genetic Algorithm (GA). The hybrid IIR-GA approach on fetal ECG MATERIALS AND METHODS extraction, the adaptation rule is combined with GA, whenever Adaptive Filter based Methods the estimated gradient stuck with local extremum. Hybrid IIR-GA Generally, an adaptive filter has the ability of self-adjusting its provide best with simulation compared to FIR LMS based weight towards minimization of error. In this technique recorded method but with real data, the method fails to show the Journal of critical reviews 295 ADAPTIVE FILTERING AND ARTIFICIAL INTELLIGENCE METHODS ON FETAL ECG EXTRACTION significant difference between them. This may be because of the results than EKF. The performance evaluation was performed by body transfer function acts as a simple low pass filter so that a calculation accuracy, sensitivity, and positive predictive value. lower order FIR adaptive filter is sufficient, and the authors Single channel is used for the extraction which requires needs suggested further studies are required to analyze this few electronic components and suits for portable monitoring assumptions. system. Talha et al. [6] also presented similar approach of GA based Khamene & Negahdaripour [10] developed a method to extract Finite Impulse Response (FIR) filter for extraction where Genetic desired signal by wavelet transform using the modulus maxima algorithm is used as a optimizer for FIR filter and the results are which is in the wavelet domain and singularity detection, compared with the other approaches of adaptive filters like acquired from the abdomen signal. To differentiate the maternal wiener filter, Recursive Least Mean Square (RLMS) and NLMS and fetal ECG signals, abdominal signal’s modulus maxima filters. The NLMS approach provide better results in terms of locations are used. The authors projected two different reliability and speed of convergence but provide divergence approaches for implementation of the algorithm, in the first results when the adaptation is too large which have been approach, to carry out the classification minimum one thoracic overcome by the method of GA based FIR filter. GA with eight bits signal is used, but in the approach no thoracic signal is required. and ten iterations provide better quality compared to other A reconstruction algorithm is applied to extract the desired algorithms and an improvement may be provided by changing signal from the identified fetal modulus maxima. The developed the order of the filter. procedure varies from the traditional time domain approaches. In this method, the significant features of the signal provide high The adaptive filtering approach may be combined with other performance against other signal disturbances is studied. approaches to provide enhancement in extraction. Kholdi et al. [7] identified a GA based adaptive filter which uses LMS based Elloumi et al. [11] projected a fetal Electrocardiogram extraction adaptive filter for extracting fetal ECG, where the best filter through two stages Pitch Synchronous Wavelet Transform coefficients are calculated based on genetic algorithm which (PSWT). This implementation is based on a modeling idea which makes the adaptive filter response converge into global is capable of capturing the signal and its fluctuations by the use extremum. The random search nature of GA find the optimum of basic elements. In the two stage method, first the maternal filter coefficients even the structure of nonlinear transformation component estimation from a contaminated abdominal signal by is unknown or the structure may vary for different person. This a pitch synchronous decomposition is made. From the result of adaptive process does not need the knowledge in advance about first stage estimation, the next iteration is carried out to extract the signal and noise statistics, only assumes the signal is the required FECG signal. The pitch synchronous wavelet uncorrelated with noise. The input and output SNR are calculated decomposition permits to identify the