医学数字信号处置心电图.pptx

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,BIOMEDICAL DIGITAL SIGNAL PROCESSING,生物医学数字信号处理,200,9.03,医学数字信号处置心电图专家讲座,第1页,霍金教授办公室（剑桥大学）,“我书每增加一个公式，读者就降低二分之一”,霍金教授,医学数字信号处置心电图专家讲座,第2页,BME在百年诺贝尔生理与医学奖中份额,美国保罗,-,劳特布尔和英国彼得,-,曼斯菲尔德共同取得了,年诺贝尔生理学或医学奖,-,核磁共振成像技术,-,三维图象,百年总计(1901-),91,（届次）,100%,属于BME范围,16,18%,与BME亲密相关,13,14%,不采取BME方法、技术、设备与材料就不能完成,39,43%,与BME无关,23,25%,医学数字信号处置心电图专家讲座,第3页,教材,作者：美国威斯康辛大学电气与计算机工程系教授,前,IEEE,生物医学工程学会主席,Willis J.Tompkins,书名：,Biomedical Digital Signal Processing,ISBN,：,7560925790,页数：,246,医学数字信号处置心电图专家讲座,第4页,Lecture 2,Electrocardiology,Electrocardiogram,ECG,第,2,讲,心电学,医学数字信号处置心电图专家讲座,第5页,心脏机械收缩之前，先产生电激动，心房和心室电激动可经人体组织传到体表。心电图是利专心电图机从体表统计心脏每一心动周期所产生电活动改变曲线图形。,医学数字信号处置心电图专家讲座,第6页,心脏特殊传导系统由窦房结、结间束（分为前、中、后结间束）、房间束（起自结间束，称,Bachmann,束）、房间交界区（房室结、希氏束）、束支（分为左、右束支，左束支又分为前分支和后分支）以及普肯耶纤维（,Pukinje fiber）,组成。心脏传导系统与每一心动周期次序出现心电改变亲密相关。正常心电活动始于窦房结，兴奋心房同时经结间束传导至房室结（激动传，然后循希氏束-左、右束支-普肯耶纤维次序传导，最终兴奋心室。这种先后有序电激动传输，引发一系列电位改变，形成了心电图上对应波段。,医学数字信号处置心电图专家讲座,第7页,心电图机是统计心电图专用仪器，有单道心电图机和多道心电图机，多道心电图机能够同时统计多导联心电，最多有同时统计12导联，而单道心电图机只能次序统计12个导联，有手控心电图机，也有程控、微电脑控制或数字式心电图机，在很多其它仪器中也常有心电统计电路模块。,三道心电图机,次序统计导联心电图后重新排列在一幅纸上,运动心电图统计系统,医学数字信号处置心电图专家讲座,第8页,2.1,Electrocardiologicbasis,2.1,心电学基础,2.1.1,three basic techniques,2.1.1,三种基本技术,1.,Standard clinical ECG,（,12 leads,）,1.标准临床,ECG,（,12,导联,）,2.,VCG(3 orthogonal leads),3.,Monitoring ECG(1 or 2 lead(s),2.向量心电图 (三维正交导联,),3.监护,ECG,(,1,或,2,导联),医学数字信号处置心电图专家讲座,第9页,2.1.2,Electrodes,2.1.2,电极,Figure 2.3 A silver-silver chloride ECG electrode.Many modern electrodes have electrolyte layers that are made of a firm gel which has adhesive properties.The firm gel minimizes the disturbance of the charge double layer.,医学数字信号处置心电图专家讲座,第10页,2.1.3,心电等效发生器,Figure 2.4 Both the electrical and mechanical conditions of the heart are involved in determining the characteristics of the spread of electrical activity over the surface of the heartA model of this activity is called a cardiac equivalent generator,2.1.3 The cardiac equivalent generator,医学数字信号处置心电图专家讲座,第11页,Figure 2.5 Einthoven equilateral triangle.RA and LA are the right and left arms and LL is the left leg.,医学数字信号处置心电图专家讲座,第12页,A current dipole is a current source and a current sink separated by a distance.,Since such a dipole has magnitude and direction which change throughout a heartbeat as the cells in the heart depolarize,this leads to the vector representation,.,电流偶极子是相隔一段距离电流源和穴(漏,)。,当心肌细胞去极化(读注：实际应包含反极化和复极化)时，这么一个偶极子大小和方向在整个心搏周期都是改变，这就造成了向量表示法。,P(t)=Px(t)X,十,Py(t)Y,十,Pz(t)Z (2.1),Where P(t)is the time-varying cardiac vector,P,i,(t),are the orthogonal components of the vector also called scalar leads,and,X,Y,Z,are unit vectors in the x,y,z directions.,式中,P(t),是时变心脏偶极子，,P,i,(t),为该矢量正交分量，也称为标量导联，,X,Y,Z,是,X,Y,Z,方向单位矢量。,医学数字信号处置心电图专家讲座,第13页,The forward solution provides the potential at any arbitrary point on the body surface for a given cardiac dipole.Expressed mathematically，,对于给定心电偶极子，心电正问题解提供了体表任意点电位，数学上表示为，,v,n,(t)=t,nx,P,x,(t),十,t,ny,P,y,(t),十,t,nz,P,y,(t)(2.2),This forward so1utlon shows that the potential,v,n,(t)(,i,e,the ECS)at any point n on the body surface is given by the linear sum of the products of a set of transfer coefficients,t,n i,unique to that point and the Corresponding orthogonal dipole vector components,P,i,(t),医学数字信号处置心电图专家讲座,第14页,The ECSs are time-varying as are the dipo1e components,while the transfer,coefficients are only dependent on the thoracic geometry and inhomogeneitiesThus for a set of k body surface potentials(i.e.,1eads)，there is a set of,k,equations that can be expressed in matrix form,V=TP,(2.3),Where V is a k x l vector representing the time-varying potentials,T is a k x 3 matrix of transfer coefficients,Which are fixed for a given individual,and P is the 3 x 1 time-varying heart vector,心电信号与偶极子分量一样是时变，而传递系数则只决定于胸部几何形状和非均匀性。所以，一组,k,体表电位,(,即,导联,)，,就有,k,equations,个方程方程组，并可表示成矩阵形式。,医学数字信号处置心电图专家讲座,第15页,Of course,the heart vector and transfer coefficients are unknown for a given individualHowever if we had a way to compute this heart vectorWe could use it in the so1ution of the forward problem and obtain the ECS for any body surface locationThe approach to solving this problem is based on a physical model of the human torsoThe model provides transfer coefficients that relate the potentials at many body surface points to the heart vector.With this information，we se1ect three ECS leads that summarize the intrinsic characteristics of the desired abnormal ECS to simulateThen we solve the inverse problem to find the cardiac dipole vector.,自然，对于任一个体心脏向量,P,和传递系数,T,是未知。然而，若我们有计算心脏矢量方法，就可用之解正问题并取得任意体表位置,ECS。,解这类问题方法建立在人体胸廓物理模型基础上。该模型提供了众多体表点电位与心脏向量关系传递系数。用该信息，则只选择三个,ECS,导联就能概括欲模拟所希望异常,ECS,本质特征。然后，就解逆问题以求出心脏偶极向量。,医学数字信号处置心电图专家讲座,第16页,Thus,for three heart vector component,there are three linear equations of the form,所以，对于,三个心脏向量分量，有以下形式三个线性方程,P,x,(t)=b,x1,v,1,(t)+b,x2,v,2,(t)+,+b,xk,v,k,(t)(2.5),P,=BV,(24),Where B is a 3 x k matrix of lead coefficients that is directly derived from inverting the transfer coefficients matrix T.,医学数字信号处置心电图专家讲座,第17页,If we select k,body surface,ECS leads,v,1,(t),v,2,(t),，,v,k,(t),for which the lead coefficients,，,T,(,or,B),，,are known from the physical model of the human torso,we can solve the inverse problem and compute the timevarying heart vector,P,using Eq.,(2.4).Once we have these dipole components,we solve the forward problem using Eq.(2.3)to compute the ECS for any point on the body surface.,假如选择了,K,个体表,ECS,导联,v,1,(t),v,2,(t),v,k,(t),，,且由人体胸廓物理模型得知了导联络数,T,(或,B,）,，则就可由,(2.4),式求解逆问题并计算时变心脏向量,P,。一旦有了这些偶极分量，则就可用方程,(2.3),解正问题以计算任意点,ECS.,医学数字信号处置心电图专家讲座,第18页,2.1.4,Genesis of the ECS,2.1.4,心电起源,Time varying motion of the cardiac vector produces the body surface ECS for one heartbeat with its characteristic P and T waves and QRS complex.,心脏向量时变运动产生体表心电，每搏都有其,特征性,P,、,T,波和,QRS,复合波。,Figure 2.7 Basic configuration for recording an electrocardiogram.Using electrodes attached to the body,the ECG is recorded with an instrumentation amplifier.(a)Transverse(top)view of a slice of the body showing the heart and lungs.(b)Frontal view showing electrodes connected in an approximate lead II configuration.,医学数字信号处置心电图专家讲座,第19页,For the points in time that the vector points toward the electrode connected to the positive terminal of the amplifier,the output ECS will be positive-going,If it points to the negative electrode,，,the ECS will be negative,(The following statement is better and more detailed.“If the vector points to the electrode connected to the negative terminal of the amplifier,the ECS will be negative”,),在心脏矢量指向电极连到放大器正端那些时间点，输出,ECS,为正。若心电向量指向电极连到放大器负端，则输出,ECS,为负。,医学数字信号处置心电图专家讲座,第20页,Figure 2.8 Electrocardiogram(ECG)for one normal heartbeat showing typical amplitudes and time duration for the P,QRS,T waves.,医学数字信号处置心电图专家讲座,第21页,Figure 2.9 Relationship between the spread of cardiac electrical activation represent at various time instants by a summing vector(in the upper frames)and the genesis of the ECS(in the lower frames).,医学数字信号处置心电图专家讲座,第22页,In Figure 2.9(a),the slow moving depolarization of the atria which begins at the sinoatrial(SA)node produces the P wave.As Figure 2.9(b)shows,the signal is delayed in the atrioventricular(AV)node resulting in an isoelectric region after the P wave,then as the Purkinje system starts delivering the stimulus to the ventricular muscle,the onset of the Q wave occurs.In Figure 2.9(c),rapid depolarization of the ventricular muscle is depicted as a large,fast-moving vector which begins producing the R wave.Figure 2.9(d)illustrates that the maximal vector represents a point in time when most of the cells are depolarized,giving rise to the peak of the R wave.In Figure 2.9(e),the final phase of ventricular depolarization occurs as the excitation spreads toward the base of the ventricles(to the top in the picture)giving rise to the S wave.,医学数字信号处置心电图专家讲座,第23页,In Figure 2.9(a),the slow moving depolarization of the atria which begins at the sinoatrial(SA)node produces the P wave.As Figure 2.9(b)shows,the signal is delayed in the atrioventri-cular(AV)node resulting in an isoelectric region after the P wave,then as the Purkinje system starts delivering the stimulus to the ventricular muscle,the onset of the Q wave occurs.In Figure 2.9(c),rapid depolarization of the ventricular muscle is depicted as a large,fast-moving vector which begins producing the R wave.Figure 2.9(d)illustrates that the maximal vector represents a point in time when most of the cells are depolarized,giving rise to the peak of the R wave.In Figure 2.9(e),the final phase of ventricular depolarization occurs as the excitation spreads toward the base of the ventricles(to the top in the picture)giving rise to the S wave.,图2.9(,a),中，始于窦房结、慢运动心房去极化，产生,P,波。正如图2.9(,b),所表示，信号经过房室结时被延迟，产生,P,波后等电区。然后，当,Purkinje,系统开始发送刺激到心室肌时，,Q,波开始发生,。在图2.9(,c),中，心室肌快速去极化表现为大而快速运动矢量，开始产生,R,波。图2.9(,d),说明，最大矢量代表了大多数细胞去极化时间点，产生,R,波峰。图2.9(,e),是激动向心室基底部(向图顶部,),传输时心室去极化终末时相，产生,S,波。,医学数字信号处置心电图专家讲座,第24页,2.1.5,The standard limb leads,2.1.5,标准肢体导联,I,+,III II=0 (2.6),Figure 2.10 Leads I,II and III are the potentials difference between the limbs as indicated.RA and LA are the right and left arms and LL is the left leg.,From Kirchhoffs voltages law,the sum of the voltages around a loop equals zero.Thus,医学数字信号处置心电图专家讲座,第25页,2.1.6,The augmented limb leads,2.1.6,加压肢体导联,Figure 2.11 The augmented limb lead aVL is measured as shown.,From the bottom left loop,iR+iR-II=0 (2.8),or,iR=II/2,(2.9),From the bottom right loop,iR+III+aVL=0 (2.10),Or aVL=iRIII (2.11),Combining Eqs.(2.9)and(2.11)gives,aVL=II/2III=(II-2III)/2 (2.12),From the top center loop,II=III+I (2.13),Substituting gives,aVL=(IIII-2III)/2=(IIII)/2 (2.14),医学数字信号处置心电图专家讲座,第26页,2.2,ECS lead systems,2.2,心电导联络统,心电学中有三种惯用基本导联络统。最通用是12导联方法，该法定义了12种电位差集合，组成标准临床,ECG。,第二种导联络统要求了统计,VCG,电极位置。经典监护系统只分析1或2个导联。,There are three basic lead systems used in cardiology.The most popular is the 12-lead approach,which defines the set of 12 potential differences that make up the standard clinical ECG.A second lead system designates the location of electrodes for recording VCG.Monitoring systems typically analyze one or two leads.,医学数字信号处置心电图专家讲座,第27页,2.2.1 12,lead ECS,2.2.1 12,导联心电,医学数字信号处置心电图专家讲座,第28页,Figure 2.16,Standard 12-lead clinical electrocardiogram.(a)Lead I.(b)Lead II.(c)Lead III.Note the amplifier polarity for each of these limb leads.(d)aVR.(e)VL.(f)aVF.These aug-mented leads require resistor networks which average two limb potentials while recording the third.(g)The six V leads are recorded referenced to Wilsons central terminal which is the average of all three limb potentials.Each of the six leads labeled V1-V6 are recorded from a different anatomical site on the chest.,医学数字信号处置心电图专家讲座,第29页,医学数字信号处置心电图专家讲座,第30页,中心电端,C,相连。全部单极导联皆参考此点电压。全部输入端皆采 用高输入阻抗电路,。,医学数字信号处置心电图专家讲座,第31页,12个标准心电图导联,双极,肢体,导联,：,I、II、III,单极加压肢体导联：,aVL、aVR、aVF,胸导联：,V1、V2、V3、V4、V5、V6,电极安放位置：,肢体导联,监护导联,医学数字信号处置心电图专家讲座,第32页,Figure 2.17 The 12-lead ECG of a normal patient.Calibration pulses on the left side designate 1 mV.The recording speed is 25 mm/s.Each minor division is I mm,so the major division are 5 mm.Thus in lead I,the R-wave amplitude is about 1.1 mV and the time between beats is almost 1 S(i.e.,heart rate is about 60 bpm).The notes are ID 0042804,S=26,L=2,C=1,I,II,III,aVR,aVL,aVF,V1,V2,V3,V4,V5,V6,Patient NO:4307400 respectively.,医学数字信号处置心电图专家讲座,第33页,2.2.2 VCS,lead system,2.2.2,向量心电导联络统,Figure 2.18 The electrode placement for the Frank vector ECS system.,Figure 2.19 The resistor network for combining body surface potentials to produce the three time-varying scalar leads of the Frank VCS lead system.,医学数字信号处置心电图专家讲座,第34页,Figure 2.20 The vectorcardiogram of a normal male patient.The three time-varying scalar leads for one heartbeat are shown on the left and are the x,y and z leads from top to bottom.In the top center is the frontal view of the tip of the vector as it moves throughout one computed heartbeat.In bottom center is a transverse view of the vector loop looking down from above the patient.On the far right is a left sagittal view looking toward the left side of the patient.,医学数字信号处置心电图专家讲座,第35页,2.2.3,Monitoring ECS,lead system,2.2.3,监护心电导联络统,Monitoring application do not use standard electrode positions but typically use two leads.Since the principal goal of these systems is to reliably recognize each heartbeat and perform rhythm analysis,electrodes are placed so that the primary ECS has a large R-wave amplitude.This ensures a high signal-to-noise ratio for beat detection.Since Lead II has a large peak amplitude for many patients,this lead is frequently recommended as the first choice of a primary lead by many manufacturers.A secondary lead with different electrode placements serves as a backup in case the primary lead develops problems such as loss of electrode contact.,监护应用不采取标准电极位置，经典使用两个导联。因该系统主要目标是可靠识别每一心搏，完成节律分析，所以电极放置以能取得最大,R,波幅度为准，这么就能确保检测心搏时有高信噪比。因,II,导联对很多病人都有大峰值，故该导联常被很多厂家推荐为首选导联。第二种导联有各种电极方法，作为主要导联发生问题(如电极接触不良,),时备用导联。,医学数字信号处置心电图专家讲座,第36页,2.3,ECS characteristics,2.3,心电信号特征,Figure 2.21,Bandwidth used in electrocardiography.The standard clinical bandwidth for the 12-lead clinical ECG is 0.005-250Hz.Monitoring systems typically use a bandwidth of 0.5-50Hz.Cardiotachometers for heart rate determination of subjects with predominantly normal beats use a simple bandpass filter centered at 17Hz and with a Q(Q-factor:quality factor)of about 3 or 4.,医学数字信号处置心电图专家讲座,第37页,心电图机原理,体表心电经电极、导联线送至心电图机，心电图机主体从原理上可分为输入回路、导联选择、放大电路、描笔驱动和走纸部分，当代心电图机通常还有程控部分。,医学数字信号处置心电图专家讲座,第38页,医学数字信号处置心电图专家讲座,第39页,医学数字信号处置心电图专家讲座,第40页,导联线,导联线是连接电极和心电图机多股电缆线，各股电缆线应绞合在一起以减小磁场干扰，并屏蔽以降低电场干扰。,导联线,可统计导联,3芯线,I or II or III,5芯线,aVR,aVL,aVF,V,12芯线,I,II,III,aVR,aVL,aVF,V1-V6,医学数字信号处置心电图专家讲座,第41页,谢谢！,医学数字信号处置心电图专家讲座,第42页,