心电信号的非线性小波检测方法

将非线性小波方法应用于心电信号的检测。利用二进Daubechies小波对有高频噪声干扰的心电信号按Mallat算法进行小波分解;探讨了非线性小波检测方法;结合Lipschitz指数判据,将其应用于高频干扰心电信号的去噪,实现了滤除噪声的同时又有效地恢复了心电信号。     

A new algorithm for ECG interference removal from single channel EMG recording

This paper presents a new method to remove electrocardiogram (ECG) interference from electromyogram (EMG). This interference occurs during the EMG acquisition from trunk muscles. The proposed algorithm employs progressive image denoising (PID) algorithm and ensembles empirical mode decomposition (EEMD) to remove this type of interference. PID is a very recent method that is being used for denoising digital images mixed with white Gaussian noise. It detects white Gaussian noise by deterministic annealing. To the best of our knowledge, PID has never been used before, in the case of EMG and ECG separation or in other 1D signal denoising applications. We have used it according to this fact that amplitude of the EMG signal can be modeled as white Gaussian noise using a filter with time-variant properties. The proposed algorithm has been compared to the other well-known methods such as HPF, EEMD-ICA, Wavelet-ICA and PID. The results show that the proposed algorithm outperforms the others, on the basis of three evaluation criteria used in this paper: Normalized mean square error, Signal to noise ratio and Pearson correlation.     

Anaesthetic EEG signal denoise using improved nonlocal mean methods

This paper applies the nonlocal mean (NLM) method to denoise the simulated and real electroencephalograph signals. As a patch-based method, the NLM method calculates the weighted sum of a patch. The weight of each point is determined by the similarity between the points of the own patch and its neighbor. Based on the weighted sum, the noise is filtered out. In this study, the NLM denoising method is applied to signals with additive Gaussian white noise, spiking noise and specific frequency noise and the results are compared with that of the popular sym8 and db16 Wavelet threshold denoising (WTD) methods. The outcomes show that the NLM on average achieves 2.70 dB increase in improved signal to noise ratio (SNRimp) and 0.37 % drop in improved percentage distortion ratio compared with WTD. The moving adaptive shape patches-NLM performs better than the original NLM when the signals change dramatically. In addition, the performance of combined NLMWTD denoising method is also better than original WTD method (0.50–4.89 dB higher in SNRimp), especially, when the signal quality is poor.     

Extended Kalman smoother with differential evolution technique for denoising of ECG signal

Electrocardiogram (ECG) signal gives a lot of information on the physiology of heart. In reality, noise from various sources interfere with the ECG signal. To get the correct information on physiology of the heart, noise cancellation of the ECG signal is required. In this paper, the effectiveness of extended Kalman smoother (EKS) with the differential evolution (DE) technique for noise cancellation of the ECG signal is investigated. DE is used as an automatic parameter selection method for the selection of ten optimized components of the ECG signal, and those are used to create the ECG signal according to the real ECG signal. These parameters are used by the EKS for the development of the state equation and also for initialization of the parameters of EKS. EKS framework is used for denoising the ECG signal from the single channel. The effectiveness of proposed noise cancellation technique has been evaluated by adding white, colored Gaussian noise and real muscle artifact noise at different SNR to some visually clean ECG signals from the MIT-BIH arrhythmia database. The proposed noise cancellation technique of ECG signal shows better signal to noise ratio (SNR) improvement, lesser mean square error (MSE) and percent of distortion (PRD) compared to other well-known methods.     

A novel approach to the extraction of fetal electrocardiogram based on empirical mode decomposition and correlation analysis

Fetal heart rate monitoring is the process of checking the condition of the fetus during pregnancy and it would allow doctors and nurses to detect early signs of trouble during labor and delivery. The fetal ECG (FECG) signal is so weak and also is corrupted by other signals and noises, mainly by maternal ECG signal. It is so hard to acquire a noise-free, precise and reliable FECG using the conventional methods. In this study, a combination of empirical mode decomposition (EMD) algorithms, correlation and match filtering is used for extracting FECG from maternal abdominal ECG signals. The proposed method benefits from match filtering ability to detect fetal signal and QRS complex to detect weak QRS peaks. The combined method, has been applied successfully on different signal qualities, even for signals that their analysis was hard and complicated for other methods. This method is able to detect R-R intervals with high accuracy. It was proved that the complete ensemble empirical mode decomposition method provides a better frequency resolution of modes and also requires less iterations that leads to a considerably less computational cost than EMD and ensemble empirical mode decomposition and can reconstruct the FECG completely from the calculated modes. We believe that this method opens a new field in non-invasive maternal abdominal signal processing so the FECG signal could be extracted with high speed and accuracy.     

Alexander fractional differential window filter for ECG denoising

The electrocardiogram (ECG) non-invasively monitors the electrical activities of the heart. During the process of recording and transmission, ECG signals are often corrupted by various types of noises. Minimizations of these noises facilitate accurate detection of various anomalies. In the present paper, Alexander fractional differential window (AFDW) filter is proposed for ECG signal denoising. The designed filter is based on the concept of generalized Alexander polynomial and the R–L differential equation of fractional calculus. This concept is utilized to formulate a window that acts as a forward filter. Thereafter, the backward filter is constructed by reversing the coefficients of the forward filter. The proposed AFDW filter is then obtained by averaging of the forward and backward filter coefficients. The performance of the designed AFDW filter is validated by adding the various type of noise to the original ECG signal obtained from MIT-BIH arrhythmia database. The two non-diagnostic measure, i.e., SNR, MSE, and one diagnostic measure, i.e., wavelet energy based diagnostic distortion (WEDD) have been employed for the quantitative evaluation of the designed filter. Extensive experimentations on all the 48-records of MIT-BIH arrhythmia database resulted in average SNR of 22.014?±?3.806365, 14.703?±?3.790275, 13.3183?±?3.748230; average MSE of 0.001458?±?0.00028, 0.0078?±?0.000319, 0.01061?±?0.000472; and average WEDD value of 0.020169?±?0.01306, 0.1207?±?0.061272, 0.1432?±?0.073588, for ECG signal contaminated by the power line, random, and the white Gaussian noise respectively. A new metric named as morphological power preservation measure (MPPM) is also proposed that account for the power preservance (as indicated by PSD plots) and the QRS morphology. The proposed AFDW filter retained much of the original (clean) signal power without any significant morphological distortion as validated by MPPM measure that were 0.0126, 0.08493, and 0.10336 for the ECG signal corrupted by the different type of noises. The versatility of the proposed AFDW filter is also validated by its application on the ECG signal from MIT-BIH database corrupted by the combination of the noises as well as on the real noisy ECG signals are taken from MIT-BIH ID database. Furthermore, the comparative study has also been done between the proposed AFDW filter and existing state of the art denoising algorithms. The results clearly prove the supremacy of our proposed AFDW filter.     

图像滤波技术在B型超声诊断仪中的应用研究

目的：依据医学超声图像固有特点,对B型超声医学图像滤波技术进行研究,以达到大幅度提高图像质量的目的。方法：通过Matlab等工具实现B型超声诊断仪图像的均值滤波、中值滤波、自适应中值滤波、小波变换以及各向异性扩散方程滤波。结果：对常见的B型超声诊断仪滤波算法进行了比较与研究。结论：所有的滤波方法对图像信号均有一定程度的增强,对噪声亦有抑制。均方误差反映了滤波图像在抑制噪声的同时,对细节的保持情况和超声医学图像两者之间达到一个最佳的平衡。     

心电信号数字滤波处理方法

本文基于３８６心电系统，给出了一种实时处理心电信号的特定的数字低通滤波器及自适应陷波器的设计方法。该方法将数字低通滤波及自适应滤波结合起来处理心电信号，明显优于以往的整系数平滑滤波及模拟陷波等方法。该方法在８０３８６系统上运行后表明对于抑制高频肌电干扰、变频的工频干扰等具有很好的效果。     

基于小波变换的ECG去噪法及仿真

为去除心电信号中的各种噪声,本文以小波变换的多分辨率分析为理论基础,利用自适应阈值调整小波变换系数,用调整后的系数进行心电信号重建。采用MIT-BIH数据库中的心电信号进行仿真、验证,有效地去除了噪声信号。与传统滤波器具去噪相比有明显的优越性。     

基于平稳小波变换的自适应心电信号去噪方法

针对小波变换的阀值去噪在心电信号消噪中的缺陷,提出将平稳小波变换和自适应滤波方法相结合的心电信号消噪方法。平稳小波变换有效地抑制了传统离散正交小波变换易产生Gibbs振荡现象。在高尺度的平稳小波分解系数中引入了自适应滤波,既消除了基线漂移噪声,又较好的保持了心电信号的低频低幅的P波、T波及ST段波的形态。这对于进一步分析心电信号的其他特征信息具有重要作用。     

心电信号数字滤波的MATLAB仿真

心电信号是一种基本的人体生理信号,然而体表检测人体心电信号中常带有工频干扰、基线漂移和肌电干扰等各种噪声,为了消除心电信号检测过程中带有的上述3种噪声,采用MATLAB有针对性的设计了三种数字滤波器来滤除相应干扰。     

ECG信号预处理的综合实现方法

体表电极检测到的ECG信号常含有不同类型的干扰，因此，检测分析前要进行预处理。文中采用数字滤波处理，在前人工作基础上进行了归纳，全面详细地阐述了对心电信号进行带通滤波、微分、平方非线性放大、移动窗积分等一系列预处理措施；用matlab验证来自MIT—BIH数据库的心电信号的处理效果。由结果可知．用文中方法消噪的同时又有效地恢复和放大了波形特征信息，优化了心电波形，为后继检测和分析提供了更加可靠的依据。由于其简单易行，为临床实现提供了重要的现实依据。     

便携式心电检测放大电路设计

目的：为便于日常心电监护，开发了一种便携式心电检测系统，介绍这种便携式心电检测系统中放大电路的设计。方法：该心电放大电路以AD620、OPA4277和TLC2254作为放大电路核心元件，针对心电信号的特殊信号和干扰频率范围，进行了分析，对由电极采集到的心电信号，通过前置放大部分，将微弱的心电信号高保真放大，并通过低通滤波、高通滤波及50Hz陷波滤除干扰。结果：差模电压增益为1000，共模抑制比为90dB，输入阻抗大于10GQ，通频带为0．035～110Hz。结论：系统具有高输入阻抗、高共模抑制比、低噪声、低温漂和高信噪比等优点，而且成本低、体积小、耗电少、携带方便。     

串口型心电信号检测模块设计

目的:设计基于串口的心电信号采集模块,该模决可以用于监护设备的设计或是临床科研的开展.方法:采用模拟和数字的混合技术,通过使用AD公司的高性能的放大器,设计高共模抑制比的前级放大器,结合硬件处理和软件的滤波方法实现信号的去噪,并转换成标准的RS232格式实现数据的获取.结果:完成了硬件电路设计,对单片机串口和定时中断、数模转化器控制程序编写,实现通过串口对外提供心电数据的服务,并可串口控制其导联的切换和滤波级别的选择等.结论:该模块能满足生产厂家、科研院所、医学工程专业院系等机构的需求,具有一定的科研用途与推广价值.     

Impedance cardiography signal denoising using discrete wavelet transform

Impedance cardiography (ICG) is a non-invasive technique for diagnosing cardiovascular diseases. In the acquisition procedure, the ICG signal is often affected by several kinds of noise which distort the determination of the hemodynamic parameters. Therefore, doctors cannot recognize ICG waveform correctly and the diagnosis of cardiovascular diseases became inaccurate. The aim of this work is to choose the most suitable method for denoising the ICG signal. Indeed, different wavelet families are used to denoise the ICG signal. The Haar, Daubechies (db2, db4, db6, and db8), Symlet (sym2, sym4, sym6, sym8) and Coiflet (coif2, coif3, coif4, coif5) wavelet families are tested and evaluated in order to select the most suitable denoising method. The wavelet family with best performance is compared with two denoising methods: one based on Savitzky–Golay filtering and the other based on median filtering. Each method is evaluated by means of the signal to noise ratio (SNR), the root mean square error (RMSE) and the percent difference root mean square (PRD). The results show that the Daubechies wavelet family (db8) has superior performance on noise reduction in comparison to other methods.     

一种高精度Holter ECG监测系统中的滤波电路设计

目的:介绍一种高精度动态心电图(Holter ECG)采集系统中的模拟滤波电路设计。方法:滤波电路设计采用AD8220作为前置放大器,OPA2604作为有源滤波器的基本单元,使用抗混叠滤波、双T陷波网络等技术。结果:该模拟滤波电路有效地解决了在ECG信号采集过程中所出现的信号混叠、噪声干扰等问题。结论:该模拟滤波电路实际应用到高精度Holter ECG采集系统中,可有效提高ECG信号进入AD转换之前的精度,最大化降低信号干扰对ECG采集系统所造成的影响,使得ECG数字化分析更加简便、准确,满足Holter ECG采集系统的稳定性、高精度的设计需求,具有一定的实用价值。     

论心电信号检测中的噪声与干扰及其消除方法

目的：认识心电信号是从体表检测到的心脏电生理信号,它对心脏疾病的诊断意义重大。方法：强调在心电信号检测过程中,很容易受到噪声（干扰）的影响,如随机噪声、工频干扰、检测系统的内部噪声等。结果：分析了心电检测中各种噪声和干扰产生的原因及消除和减小噪声（干扰）的方法。结论：为了尽可能地消除噪声（干扰）,又不使检测到的心电信号失真,这就需要改进采集电路、滤波电路,运用新的运算方法。     

基于边缘检测的CT图像粗糙集增强算法

粗糙集理论是一种处理模糊和不确定性问题的工具，是一种非线性处理方法。本文基于边缘检测对图像进行小波阈值去噪，在此基础之上引入粗糙集理论划分子图并分别进行增强处理，再进行对比度增强。该算法把边缘检测去噪与粗糙集理论结合起来增强图像，实践证明具有良好的图像增强效果。     

HHT在生物雷达回波信号噪声抑制中的应用

目的:利用Hilbert-Huang Transform(HHT)的频率区分特性,对生物雷达回波信号进行处理,去除高频噪声成分,提高生物雷达对生命信息的识别能力。方法:首先对经过预处理的雷达回波信号进行经验模态分解获取其固有模态函数,并根据能量分析方法将固有模态函数区分为有用信号占主导模态与噪声占主导模态2个部分,然后用小波软阈值的方法提取噪声占主导模态部分中的有用成分,与有用信号占主导模态部分的固有模态函数叠加,获取雷达回波信号中的生命信息,实现时目标的识别。结果:HHT有效地去除了生物雷达回波信号中的高频噪声成分,提取出了人体呼吸信号。结论:与传统傅里叶去噪方法相比,HHT分辨率更高,能保留信号中的细节特征,为生命体目标的识别提供了更多的信息。     

基于MATLAB的工频干扰陷波器设计

50Hz的工频干扰是心电信号的主要干扰源,尤其在供电系统不稳定、外界环境适应性差时严重影响心电信号正确判断。本文通过MATLAB提供的信号处理工具箱,简便高效地设计出了高性能50Hz陷波器,该设计省却了其它设计方法的繁琐过程,经滤波实地应用证明了该陷波器的有效性。