基于改进FastICA的胎儿心电提取算法研究

针对FastICA算法容易陷入局部最优,导致提取的胎儿心电往往含有较多噪声的问题.本文将修正BFGS法(MB?FGS)和混沌优化算法相结合来代替传统的牛顿迭代法,提出一种新的独立分量分析方法,并用于胎儿心电信号的提取.分别用合成信号和临床信号对该算法进行验证,实验结果表明本文提出的算法能提取出清晰并不含母体心电的胎儿心电信号,而且算法性能更优于FastICA.     

使用广义回归神经网络的胎儿心电提取

针对胎儿心电难以提取问题,提出一种从母体腹壁混合信号中提取胎儿心电的方法。利用广义回归神经网络（GRNN）估计母体心电信号传导至腹壁的非线性变换,将非线性变换后的母体心电信号从腹壁混合信号中减去,再通过小波包去噪技术抑制胎儿心电的基线漂移和噪声,得到清晰的胎儿心电。应用合成心电信号和临床心电信号完成实验,在胎儿心电和母体心电QRS波完全重叠情况下,提取出清晰的胎儿心电。实验结果验证了方法的有效性。     

结合ICA和PCA方法的胎儿心电提取

在生物医学信号处理领域,独立分量分析(PCA)和主分量分析(ICA)是两种广泛应用的方法。但是,这两种方法各有其优缺点。提出了一种新颖的方法,将ICA和PCA相结合,通过求相关的技术,分别取ICA和PCA方法的优点。将该方法应用于从母体腹部测得的多通道信号中提取胎儿心电信号的实验,得到令人满意的结果。研究结果表明,这种结合ICA和PCA的方法能够比较准确地分离出所需要的胎儿心电信号,进而可以对胎儿心电进行监护,因此在临床上具有一定的实用价值。     

基于MICA技术的胎儿心电信号提取的应用研究

多维独立分析（Multidimensional Independent Component Analysis,MICA）方法适用于实现多分量信号分析和分量提取,可实际应用于对胎儿心电信号的提取。为了说明MICA算法分离结果的可靠性,利用动态心电合成模型生成仿真的心电信号数据进行了验证,用vkMICA、cfMICA、SJADE、MSOBI四种MICA算法对实际采集到孕妇心电数据集进行了处理。实验结果显示,四种MICA算法可提取出较纯净的胎儿心电信号,并能较好地反映出胎儿心电信号的实际特征。     

基于R峰配准重构的弱胎心电盲分离方法

利用盲分离技术从母亲腹心电中分离出胎心电在胎心电幅度较强的情况下是可行的,但如果胎心电过弱,盲分离中容易将胎心电视作噪声而无法正确分离.在胎心电过弱时,先对腹心电进行形态学滤波后检测胎心电的R峰,然后在配准胎儿R峰的前提下,平移、叠加并重构信号,最后对重构信号应用盲分离方法分离出较好的胎心电信号.实验证明,当胎心电微弱,直接盲分离容易将胎心电作为噪声而无法得到有效胎心电时,R峰配准重构可以有效地增强胎心电的信号强度,对重构后的信号进行盲分离可得到有效的胎心电,进而得到较精确的胎心率.     

Piecewise linear correction of ECG baseline wander: a curve simplification approach

In this paper, we suggest a novel method for ECG baseline correction, exclusively based on pattern recognition tools, namely, dominant points (DPs). The DPs are computed by the Douglas-Peucker curve simplification algorithm. The so-computed DPs include peak and baseline points, the discrimination of which yields gradual piecewise linear estimation of the baseline wander (BaselineW) in two iterations. At each iteration, the current BaselineW is subtracted from the input signal according to the decomposition scheme: ECG approximately ECG(ZBLW) + BaselineW, where ECG(ZBLW) is the underlying baseline wander free ECG. The method targets many types of baseline deviations in a unified approach: baseline drift due to respiration, amplitude modulation due to perspiration and abrupt potential change due to electrode loose contact. We tested the developed method on a variety of ECG records including half synthesized records contaminated with different types of baseline deviations (simulated) noise, and on records from the MITBIH database presenting important baseline deviations, including normal and abnormal heart beats cases. The method showed good performance in computing a piecewise linear estimation of the baseline deviation and in extracting the ECG(ZBLW), which represents the clinically significant electrocardiogram information.     

A new method for fetal ECG detection

Presented in this work is the theoretical basis of a new method we propose for the analysis of fetal ECG (FECG). This method is intended to detect the fetal HR from a weak FECG signal, and to supply us with an average FECG complex. The FECG signals studied in this work were recorded from the maternal abdominal wall. The core of our method is the computation of a triple parametric transform, using analyzing functions which have a greater correlation with the ECG signal than the correlation of the standard sine and cosine functions used in a Fourier transform. The functions used are trains of square waves characterized by the width of the square wave, their periodicity, and some initial phase value. This method, applied here to a medical problem, can be more generally applied to handle weak quasiperiodic sharp signals of any origin.     

基于回归支持向量机的胎儿心电提取

针对胎儿心电难以提取的问题,提出一种从母体腹壁混合信号中提取胎儿心电的方法.首先利用回归支持向量机(Support vector regression machine,SVRM)拟合母体心电传导至腹壁所经历的非线性变换,然后将母体心电经由所拟合的非线性变换得到腹壁混合信号中的母体心电干扰的最优估计,再从腹壁混合信号中减去母体心电干扰的最优估计得到含噪声的胎儿心电,最后通过小波包去噪技术抑制胎儿心电中的基线漂移和噪声,得到清晰的胎儿心电.在胎儿心电和母体心电QRS波完全重叠的情况下,通过该方法能够提取出清晰的胎儿心电.实验结果验证了该方法的有效性.     

Kernel-based nonlinear dimensionality reduction for electrocardiogram recognition

The human heart is a complex system that reveals many clues about its condition in its electrocardiogram (ECG) signal, and ECG supervising is the most important and efficient way of preventing heart attacks. ECG analysis and recognition are both important and tempting topics in modern medical research. The purpose of this paper is to develop an algorithm which investigates kernel method, locally linear embedding (LLE), principal component analysis (PCA), and support vector machine(SVM) algorithms for dimensionality reduction, features extraction, and classification for recognizing and classifying the given ECG signals. In order to do so, a nonlinear dimensionality reduction kernel method based LLE is proposed to reduce the high dimensions of the variational ECG signals, and the principal characteristics of the signals are extracted from the original database by means of the PCA, each signal representing a single and complete heart beat. SVM method is applied to classify the ECG data into several categories of heart diseases. Experimental results obtained demonstrated that the performance of the proposed method was similar and sometimes better when compared to other ECG recognition techniques, thus indicating a viable and accurate technique.     

A comparative analysis of principal component and independent component techniques for electrocardiograms

Principal component analysis (PCA) is used for ECG data compression, denoising and decorrelation of noisy and useful ECG components or signals. In this study, a comparative analysis of independent component analysis (ICA) and PCA for correction of ECG signals is carried out by removing noise and artifacts from various raw ECG data sets. PCA and ICA scatter plots of various chest and augmented ECG leads and their combinations are plotted to examine the varying orientations of the heart signal. In order to qualitatively illustrate the recovery of the shape of the ECG signals with high fidelity using ICA, corrected source signals and extracted independent components are plotted. In this analysis, it is also investigated if difference between the two kurtosis coefficients is positive than on each of the respective channels and if we get a super-Gaussian signal, or a sub-Gaussian signal. The efficacy of the combined PCA–ICA algorithm is verified on six channels V1, V3, V6, AF, AR and AL of 12-channel ECG data. ICA has been utilized for identifying and for removing noise and artifacts from the ECG signals. ECG signals are further corrected by using statistical measures after ICA processing. PCA scatter plots of various ECG leads give different orientations of the same heart information when considered for different combinations of leads by quadrant analysis. The PCA results have been also obtained for different combinations of ECG leads to find correlations between them and demonstrate that there is significant improvement in signal quality, i.e., signal-to-noise ratio is improved. In this paper, the noise sensitivity, specificity and accuracy of the PCA method is evaluated by examining the effect of noise, base-line wander and their combinations on the characteristics of ECG for classification of true and false peaks.     

基于信号质量评估的可穿戴动态心电监护

针对医疗保健领域人体生理监护的需要,提出了一种基于信号质量评估和卡尔曼滤波的可穿戴动态心电监护系统的设计。首先分析了可穿戴动态心电信号的特征,接着给出了基于信号质量评估和卡尔曼滤波的动态心率估计模型,并说明了利用R波检测和加速度计的结果来获得运动状态下心电信号质量指数SQI的方法,然后通过SQI的值对卡尔曼滤波器的参数进行动态调节,以获得最佳的心率估计。最后,通过实际的测试证明了该系统具有较高的可靠性和有效性。     

一种基于压缩域的穿戴式心电信号直接特征提取与分类方法

压缩感知是实现可穿戴式健康监测系统低能耗工作方式的一种有效途径,而现有基于压缩感知的心电信号分类方法大多需要在进行分类之前,先使用重构算法恢复出原始心电信号,这可能会导致较高的计算复杂度高,不适合于具有实时性需求的可穿戴式系统。提出一种基于压缩域的穿戴式心电信号的特征提取与自动分类方法。跳过信号重构步骤,使用改进的主成分分析法在压缩域上直接对压缩后的心电信号进行特征提取,并基于最小二乘支持向量机半监督学习方法实现心电信号的自动分类。实验结果表明,相较于在非压缩域上的分类方法,该方法在保证分类性能下降非常少的前提下,心电数据量大大地减少,有效提高了心电信号自动分类的效率。     

使用时频盲源分离和小波包去噪的胎儿心电信号提取

提出一种使用时频盲源分离(TFBSS)和小波包去噪的胎儿心电信号提取新方法。首先通过重排时频谱时频盲源分离方法进行胎儿心电信号的初次提取,并将初次提取得到的母体心电信号和噪声对应的各路分量置零,其余分量由混合矩阵进行重构;然后再利用重排时频谱的时频盲源分离方法对重构信号进行胎儿心电信号的二次提取,得到含噪声的胎儿心电信号;最后通过小波包去噪抑制胎儿心电信号中的基线漂移和噪声。在胎儿心电信号和母体心电信号的QRS波无重叠、部分重叠或完全重叠的情况下,通过该方法能有效抑制母体心电信号和噪声的干扰,提取胎儿心电信号。实验结果表明该方法能提取清晰的胎儿心电信号。     

A two-stage mechanism for registration and classification of ECG using Gaussian mixture model

An automatic classifier for electrocardiogram (ECG) based cardiac abnormality detection using Gaussian mixture model (GMM) is presented here. In first stage, pre-processing that includes re-sampling, QRS detection, linear prediction (LP) model estimation, residual error signal computation and principal component analysis (PCA) has been used for registration of linearly independent ECG features. GMM is here used for classification based on the registered features in a two-class pattern classification problem using 730 ECG segments from MIT-BIH Arrhythmia and European ST-T Ischemia datasets. A set of 12 features explaining 99.7% of the data variability is obtained using PCA from residual error signals for GMM based classification. Sixty percent of the data is used for training the classifier and 40% for validating. It is observed that the overall accuracy of the proposed strategy is 94.29%. As an advantage, it is also verified that Chernoff bound and Bhattacharya bounds lead to minimum error for GMM based classifier. In addition, a comparative study is done with the standard classification techniques with respect to its overall accuracy.     

Investigation of time, amplitude, and frequency parameters of a direct fetal ECG signal during labor and delivery

Direct acquisition and analysis of the fetal ECG signal during labor is important for monitoring the well being of the fetus. The results of the present study of the frequency, time, and amplitude parameters of fetal ECG signals can be used to develop algorithms for analyzing the fetal ECG during labor. The article was translated by the authors. This work was partially supported by the Russian Foundation for Basic Research, project no. 03-01-00216.     

基于改进EEMD的心电信号基线漂移消除方法

针对传统方法滤波效果不佳的问题,本文提出了基于改进集合经验模态分解（Ensemble empirical mode decomposition,EEMD）的消除心电信号基线漂移方法。该方法克服了经验模态分解（Empirical mode decomposition,EMD）模态混叠的问题,并对EEMD方法存在的问题和不足进行改进,建立集合经验模态分解方法中加入辅助白噪声大小的可依据准则,从而确定加入的辅助白噪声大小以及集合平均次数这两个重要参数。它从含噪心电信号中提取基线漂移信号,然后重构其余本征模函数（Intrinsic mode function,IMF）分量得到"干净"的心电信号,为后续的研究提供前提。经实验验证表明：相较于传统方法,这种方法能够提高信噪比、降低均方差、保持特征波形、去噪更加彻底,很好地解决了心电信号低频成分损失的问题。     

EMGdi signal enhancement based on ICA decomposition and wavelet transform

Diaphragmatic electromyogram (EMGdi) signal plays an important role in the diagnosis and analysis of respiratory diseases. However, EMGdi recordings are often contaminated by electrocardiographic (ECG) interference, which posing serious obstacle to traditional denoising approaches due to overlapped spectra of these signals. In this paper, a novel method based on wavelet transform and independent component analysis (ICA) is proposed to remove the ECG interference from noisy EMGdi signals. With the proposed method, the original independent components of contaminated EMGdi signal were first obtained with ICA. Then the ECG components contained were removed by a specially designed wavelet domain filter. After that, the purified independent components were reconstructed back to the original signal space by ICA to obtain clean EMGdi signals. Experimental results achieved on practical clinical data show that the proposed approach is better than several traditional methods include wavelet transform (WT), ICA, digital filter and adaptive filter in ECG interference removing.     

QRS detection based on wavelet coefficients

Electrocardiogram (ECG) signal processing and analysis provide crucial information about functional status of the heart. The QRS complex represents the most important component within the ECG signal. Its detection is the first step of all kinds of automatic feature extraction. QRS detector must be able to detect a large number of different QRS morphologies. This paper examines the use of wavelet detail coefficients for the accurate detection of different QRS morphologies in ECG. Our method is based on the power spectrum of QRS complexes in different energy levels since it differs from normal beats to abnormal ones. This property is used to discriminate between true beats (normal and abnormal) and false beats. Significant performance enhancement is observed when the proposed approach is tested with the MIT-BIH arrhythmia database (MITDB). The obtained results show a sensitivity of 99.64% and a positive predictivity of 99.82%.     

An algorithm for extracting fetal electrocardiogram

The extraction of fetal electrocardiogram (FECG) from the composite maternal ECG signal is discussed. This problem can be modelled from the perspective of blind source extraction. An important and primary work is done by Barros and Cichocki, who propose an FECG extraction method for the noisy-free mixing model. However, it is realistic to extract the FECG from noisy measurements. Therefore, we propose a new algorithm for the FECG extraction with additive noise. Theoretical analysis and simulation results confirm the validity of the proposed algorithm.     

An improved procedure for detection of heart arrhythmias with novel pre‐processing techniques

The objective of this study is to develop an algorithm to detect and classify six types of electrocardiogram (ECG) signal beats including normal beats (N), atrial pre‐mature beats (A), right bundle branch block beats (R), left bundle branch block beats (L), paced beats (P), and pre‐mature ventricular contraction beats (PVC or V) using a neural network classifier. In order to prepare an appropriate input vector for the neural classifier several pre‐processing stages have been applied. Initially, a signal filtering method is used to remove the ECG signal baseline wandering. Continuous wavelet transform is then applied in order to extract features of the ECG signal. Next, principal component analysis is used to reduce the size of the data. A well‐known neural network architecture called the multi‐layered perceptron neural network is then utilized as the final classifier to classify each ECG beat as one of six groups of signals under study. Finally, the MIT‐BIH database is used to evaluate the proposed algorithm, resulting in 99.5% sensitivity, 99.66% positive predictive accuracy and 99.17% total accuracy.