医学数字信号处理心电图课件

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,*,资料仅供参考,不当之处，请联系改正。,霍金教授的办公室（剑桥大学）,“我的书每增加一个公式，读者就减少一半”,霍金教授,BME在百年诺贝尔生理与医学奖中的份额,美国的保罗,-,劳特布尔和英国的彼得,-,曼斯菲尔德共同获得了,2003,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,(1901-2000),91,（届次）,100%,属于,BME,范畴,16,18%,与,BME,密切相关,13,14%,不采用,BME,方法、技术、设备与材料就不能完成的,39,43%,与,BME,无关的,23,25%,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,Lecture 2,Electrocardiology,Electrocardiogram,ECG,第,2,讲,心电学,心脏机械收缩之前，先产生电激动，心房和心室的电激动可经人体组织传到体表。心电图是利用心电图机从体表记录心脏每一心动周期所产生电活动变化曲线图形。,心脏的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）,构成。心脏传导系统与每一心动周期顺序出现的心电变化密切相关。正常心电活动始于窦房结，兴奋心房的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-普肯耶纤维顺序传导，最后兴奋心室。这种先后有序的电激动的传播，引起一系列电位改变，形成了心电图上相应的波段。,心电图机是记录心电图的专用仪器，有单道心电图机和多道心电图机，多道心电图机可以同时记录多导联的心电，最多有同时记录12导联的，而单道心电图机只能顺序记录12个导联，有手控的心电图机，也有程控的、微电脑控制或数字式的心电图机，在很多其它仪器中也常有心电记录电路模块。,三道心电图机,顺序记录导联心电图后重新排列在一幅纸上,运动心电图记录系统,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),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.,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,Figure 2.5 Einthoven equilateral triangle.RA and LA are the right and left arms and LL is the left leg.,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的电流源和穴(漏,)。,当心肌细胞去极化(读注：实际应包含反极化和复极化)时，这样一个偶极子的大小和方向在整个心搏周期都是变化的，这就导致了向量表示法。,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),为该矢量的正交分量，也称为标量导联，,X,Y,Z,是,X,Y,Z,方向的单位矢量。,The forward solution provides the potential at any arbitrary point on the body surface for a given cardiac dipole.Expressed mathematically，,对于给定的心电偶极子，心电正问题的解提供了体表任意点的电位，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),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的，而传递系数则只决定于胸部的几何形状和非均匀性。因此，一组,k,体表电位,(,即,导联,)，,就有,k,equations,个方程的方程组，并可表示成矩阵形式。,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,是未知的。然而，若我们有计算心脏矢量的方法，就可用之解正问题并获得任意体表位置的,ECS。,解此类问题的方法建立在人体胸廓物理模型的基础上。该模型提供了众多体表点的电位与心脏向量的关系的传递系数。用该信息，则只选择三个,ECS,导联就能概括欲模拟的所希望的异常,ECS,的本质特征。然后，就解逆问题以求出心脏偶极向量。,Thus,for three heart vector component,there are three linear equations of the form,因此，对于,三个心脏向量的分量，有如下形式的三个线性方程,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.,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 so