医学数字信号处理 心电图课件（可编辑）

医学数字信号处理心电图课件BIOMEDICAL生物医学DIGITAL数字信号SIGNAL处理PROCESSING200903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百年总计1901200010091届次属于BME范畴1618与BME密切相关1314不采用BME方法、技术、3943设备与材料就不能完成的与BME无关的2325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WILLISJTOMPKINS书名BIOMEDICALDIGITALSIGNALPROCESSINGISBN7560925790页数246LECTURE2第2讲ELECTROCARDIOLOGY心电学ELECTROCARDIOGRAMECG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PUKINJEFIBER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。三道心电图机运动心电图记录系统顺序记录12导联心电图后重新排列在一幅纸上21ELECTROCARDIOLOGIC21心电学基础BASIS211三种基本技术211THREEBASICTECHNIQUES1标准临床ECG1STANDARDCLINICALECG12LEADS12导联2向量心电图2VCG3ORTHOGONALLEADS三维正交导联3MONITORINGECG1OR23监护ECGLEADS1或2导联212电极212ELECTRODESFIGURE23ASILVERSILVERCHLORIDEECGELECTRODEMANYMODERNELECTRODESHAVEELECTROLYTELAYERSTHATAREMADEOFAFIRMGELWHICHHASADHESIVEPROPERTIESTHEFIRMGELMINIMIZESTHEDISTURBANCEOFTHECHARGEDOUBLELAYER213THECARDIAC213心电等效EQUIVALENT发生器GENERATORFIGURE24BOTHTHEELECTRICALANDMECHANICALCONDITIONSOFTHEHEARTAREINVOLVEDINDETERMININGTHECHARACTERISTICSOFTHESPREADOFELECTRICALACTIVITYOVERTHESURFACEOFTHEHEARTAMODELOFTHISACTIVITYISCALLEDACARDIACEQUIVALENTGENERATORFIGURE25EINTHOVENEQUILATERALTRIANGLERAANDLAARETHERIGHTANDLEFTARMSANDLLISTHELEFTLEGACURRENTDIPOLEISACURRENT电流偶极子是相隔一段SOURCEANDACURRENTSINK距离的电流源和穴漏。SEPARATEDBYADISTANCESINCE当心肌细胞去极化读注SUCHADIPOLEHASMAGNITUDE实际应包含反极化和复ANDDIRECTIONWHICHCHANGE极化时,这样一个偶极THROUGHOUTAHEARTBEATASTHE子的大小和方向在整个CELLSINTHEHEARTDEPOLARIZE,心搏周期都是变化的,THISLEADSTOTHEVECTOR这就导致了向量表示法。REPRESENTATIONPTPXTX十PYTY十PZTZ21WHEREPTISTHETIMEVARYING式中PT是时变心脏偶极CARDIACVECTOR,PTARETHEI子,PT为该矢量的正交IORTHOGONALCOMPONENTSOFTHE分量,也称为标量导联,VECTORALSOCALLEDSCALARLEADS,X,Y,Z是X,Y,Z方向的单位ANDX,Y,ZAREUNITVECTORSINTHEX,矢量。Y,ZDIRECTIONSTHEFORWARDSOLUTIONPROVIDES对于给定的心电偶极THEPOTENTIALATANYARBITRARY子,心电正问题的解提POINTONTHEBODYSURFACEFORA供了体表任意点的电GIVENCARDIACDIPOLEEXPRESSED位,数学上表示为,MATHEMATICALLY,VTTPT十TPT十TPT22NNXXNYYNZYTHISFORWARDSO1UTLONSHOWSTHATTHEPOTENTIALVTNIE,THEECSATANYPOINTNONTHEBODYSURFACEISGIVENBYTHELINEARSUMOFTHEPRODUCTSOFASETOFTRANSFERCOEFFICIENTSTUNIQUETOTHATPOINTANDTHENICORRESPONDINGORTHOGONALDIPOLEVECTORCOMPONENTSPTITHEECSSARETIMEVARYINGAS心心电电信信号号与与偶偶极极子子分分心电信号与偶极子分ARETHEDIPO1ECOMPONENTS,量一样是时变的,而量量一一样样是是时时变变的的,而而WHILETHETRANSFERCOEFFICIENTS传传递递系系数数则则只只决决定定于于传递系数则只决定于AREONLYDEPENDENTONTHE胸部的几何形状和非胸胸部部的的几几何何形形状状和和非非THORACICGEOMETRYAND均均均匀匀匀性性性。因因因此此此,一一一组组组INHOMOGENEITIESTHUSFORASETKK体体表表电电位位即即,导导K体表电位即,导联,就有KOFKBODYSURFACEPOTENTIALSIE,联联,就就有有KK1EADS,THEREISASETOFKEEQQUUATATIIONONSS个方个方程程的的方方EQUATIONS个方程的方EQUATIONSTHATCANBEEXPRESSED程组,并可表示成矩程程组组,并并可可表表示示成成矩矩INMATRIXFORM阵形式。阵形式。阵形式。VTP23WHEREVISAKXLVECTORREPRESENTINGTHETIMEVARYINGPOTENTIALS,TISAKX3MATRIXOFTRANSFERCOEFFICIENTS,WHICHAREFIXEDFORAGIVENINDIVIDUAL,ANDPISTHE3X1TIMEVARYINGHEARTVECTOROOFFCCOOUURRSSEE,TTHHEEHHEEAARRTTVVEECCTTOORRAANNDDTTRRAANNSSFFEERROFCOURSE,THEHEARTVECTORANDTRANSFER自然,对于任一个体心CCCOOOEEEFFFFFFIIICCCIIIEEENNNTTTSSSAAARRREEEUUUNNNKKKNNNOOOWWWNNNFFFOOORRRAAAGGGIIIVVVEEENNN脏向量P和传递系数TINDIVIDUALHOWEVERIFWEHADAWAYTOIINNDDIIVVIIDDUUAALLHHOOWWEEVVEERRIIFFWWEEHHAADDAAWWAAYYTTOO是未知的。然而,若我CCOOMMPPUUTTEETTHHIISSHHEEAARRTTVVEECCTTOORRWWEECCOOUULLDDUUSSEECOMPUTETHISHEARTVECTORWECOULDUSE们有计算心脏矢量的方IIITTTIIINNNTTTHHHEEESSSOOO111UUUTTTIIIOOONNNOOOFFFTTTHHHEEEFFFOOORRRWWWAAARRRDDDPPPRRROOOBBBLLLEEEMMM法,就可用之解正问题ANDOBTAINTHEECSFORANYBODYSURFACEAANNDDOOBBTTAAIINNTTHHEEEECCSSFFOORRAANNYYBBOODDYYSSUURRFFAACCEE并获得任意体表位置的LLLOOOCCCAAATTTIIIOOONNNTTTHHHEEEAAAPPPPPPRRROOOAAACCCHHHTTTOOOSSSOOOLLLVVVIIINNNGGGTTTHHHIIISSSECS。解此类问题的方PPPRRROOOBBBLLLEEEMMMIIISSSBBBAAASSSEEEDDDOOONNNAAAPPPHHHYYYSSSIIICCCAAALLLMMMOOODDDEEELLLOOOFFF法建立在人体胸廓物理THEHUMANTORSOTHEMODELPROVIDESTTHHEEHHUUMMAANNTTOORRSSOOTTHHEEMMOODDEELLPPRROOVVIIDDEESS模型的基础上。该模型TTTRRRAAANNNSSSFFFEEERRRCCCOOOEEEFFFFFFIIICCCIIIEEENNNTTTSSSTTTHHHAAATTTRRREEELLLAAATTTEEETTTHHHEEE提供了众多体表点的电PPPOOOTTTEEENNNTTTIIIAAALLLSSSAAATTTMMMAAANNNYYYBBBOOODDDYYYSSSUUURRRFFFAAACCCEEEPPPOOOIIINNNTTTSSSTTTOOO位与心脏向量的关系的THEHEARTVECTORWITHTHISINFORMATION,TTHHEEHHEEAARRTTVVEECCTTOORRWWIITTHHTTHHIISSIINNFFOORRMMAATTIIOONN,传递系数。用该信息,WWWEEESSSEEE111EEECCCTTTTTTHHHRRREEEEEEEEECCCSSSLLLEEEAAADDDSSSTTTHHHAAATTT则只选择三个ECS导联SSSUUUMMMMMMAAARRRIIIZZZEEETTTHHHEEEIIINNNTTTRRRIIINNNSSSIIICCCCCCHHHAAARRRAAACCCTTTEEERRRIIISSSTTTIIICCCSSSOOOFFF就能概括欲模拟的所希TTHHEEDDEESSIIRREEDDAABBNNOORRMMAALLEECCSSTTOOTHEDESIREDABNORMALECSTO望的异常ECS的本质特SSSIIIMMMUUULLLAAATTTEEETTTHHHEEENNNWWWEEESSSOOOLLLVVVEEETTTHHHEEEIIINNNVVVEEERRRSSSEEE征。然后,就解逆问题PPPRRROOOBBBLLLEEEMMMTTTOOOFFFIIINNNDDDTTTHHHEEECCCAAARRRDDDIIIAAACCCDDDIIIPPPOOOLLLEEEVVVEEECCCTTTOOORRR以求出心脏偶极向量。PBV24WHEREBISA3XKMATRIXOFLEADCOEFFICIENTSTHATISDIRECTLYDERIVEDFROMINVERTINGTHETRANSFERCOEFFICIENTSMATRIXTTHUS,FORTHREEHEARTVECTOR因此,对于因此,对于因此,对于三个心脏向量三个心脏向量三个心脏向量COMPONENT,THEREARETHREE的分量,有如下形式的三的分量,有如下形式的三的分量,有如下形式的三LINEAREQUATIONSOFTHEFORM个线性方程个线性方程个线性方程PTBVTBVTBVT25XX11X22XKKIFWESELECTKBODYSURFACE如果选择了K个体表ECSLEADSVT,VT,ECS导联VT,121VTFORWHICHTHELEADVT,VT,且由K2KTCOEFFICIENTS,TTORB,ARE人体胸廓的物理模型KNOWNFROMTHEPHYSICAL得知了导联系数TTT或MODELOFTHEHUMANTORSO,WEB,则就可由24CANSOLVETHEINVERSEPROBLEM式求解逆问题并计算ANDCOMPUTETHETIMEVARYING时变的心脏向量P。HEARTVECTOR,P,USINGEQ24一旦有了这些偶极分ONCEWEHAVETHESEDIPOLE量,则就可用方程COMPONENTS,WESOLVETHE23解正问题以计算FORWARDPROBLEMUSINGEQ任意点的ECS23TOCOMPUTETHEECSFORANYPOINTONTHEBODYSURFACE214GENESISOFTHEECS214心电的起源TIMEVARYINGMOTIONOFTHE心脏向量的时变运动CARDIACVECTORPRODUCESTHEBODY产生体表心电,每搏SURFACEECSFORONEHEARTBEAT都有其特征性的P、TWITHITSCHARACTERISTICPANDT波和QRS复合波。WAVESANDQRSCOMPLEXFIGURE27BASICCONFIGURATIONFORRECORDINGANELECTROCARDIOGRAMUSINGELECTRODESATTACHEDTOTHEBODY,THEECGISRECORDEDWITHANINSTRUMENTATIONAMPLIFIERATRANSVERSETOPVIEWOFASLICEOFTHEBODYSHOWINGTHEHEARTANDLUNGSBFRONTALVIEWSHOWINGELECTRODESCONNECTEDINANAPPROXIMATELEADIICONFIGURATION在心脏矢量指向的FORTHEPOINTSINTIMETHATTHEVECTOR电极连到放大器正POINTSTOWARDTHEELECTRODECONNECTED端的那些时间点,TOTHEPOSITIVETERMINALOFTHE输出的ECS为正的。AMPLIFIER,THEOUTPUTECSWILLBE若心电向量指向的POSITIVEGOINGIFITPOINTSTOTHE电极连到放大器负NEGATIVEELECTRODE,THEECSWILLBE端,则输出的ECSNEGATIVETHEFOLLOWINGSTATEMENTIS为负的。BETTERANDMOREDETAILED“IFTHEVECTORPOINTSTOTHEELECTRODECONNECTEDTOTHENEGATIVETERMINALOFTHEAMPLIFIER,THEECSWILLBENEGATIVE”FIGURE28ELECTROCARDIOGRAMECGFORONENORMALHEARTBEATSHOWINGTYPICALAMPLITUDESANDTIMEDURATIONFORTHEP,QRS,TWAVESFIGURE29RELATIONSHIPBETWEENTHESPREADOFCARDIACELECTRICALACTIVATIONREPRESENTATVARIOUSTIMEINSTANTSBYASUMMINGVECTORINTHEUPPERFRAMESANDTHEGENESISOFTHEECSINTHELOWERFRAMESINFIGURE29A,THESLOWMOVINGDEPOLARIZATIONOFTHEATRIAWHICHBEGINSATTHESINOATRIALSANODEPRODUCESTHEPWAVEASFIGURE29BSHOWS,THESIGNALISDELAYEDINTHEATRIOVENTRICULARAVNODERESULTINGINANISOELECTRICREGIONAFTERTHEPWAVE,THENASTHEPURKINJESYSTEMSTARTSDELIVERINGTHESTIMULUSTOTHEVENTRICULARMUSCLE,THEONSETOFTHEQWAVEOCCURSINFIGURE29C,RAPIDDEPOLARIZATIONOFTHEVENTRICULARMUSCLEISDEPICTEDASALARGE,FASTMOVINGVECTORWHICHBEGINSPRODUCINGTHERWAVEFIGURE29DILLUSTRATESTHATTHEIMALVECTORREPRESENTSAPOINTINTIMEWHENMOSTOFTHECELLSAREDEPOLARIZED,GIVINGRISETOTHEPEAKOFTHERWAVEINFIGURE29E,THEFINALPHASEOFVENTRICULARDEPOLARIZATIONOCCURSASTHEEXCITATIONSPREADSTOWARDTHEBASEOFTHEVENTRICLESTOTHETOPINTHEPICTUREGIVINGRISETOTHESWAVEINFIGURE29A,THESLOWMOVINGDEPOLARIZATION图29A中,始于窦房结的、慢运动的心房OFTHEATRIAWHICHBEGINSATTHESINOATRIALSA去极化,产生P波。NODEPRODUCESTHEPWAVEASFIGURE29B正如图29B所示,SHOWS,THESIGNALISDELAYEDINTHEATRIOVENTRI信号通过房室结时被CULARAVNODERESULTINGINANISOELECTRIC延迟,产生P波后的REGIONAFTERTHEPWAVE,THENASTHEPURKINJE等电区。然后,当PURKINJE系统开始发SYSTEMSTARTSDELIVERINGTHESTIMULUSTOTHE送刺激到心室肌时,VENTRICULARMUSCLE,THEONSETOFTHEQWAVEQ波开始发生。在图OCCURSINFIGURE29C,RAPIDDEPOLARIZATIONOF29C中,心室肌的快THEVENTRICULARMUSCLEISDEPICTEDASALARGE,速去极化表现为大而FASTMOVINGVECTORWHICHBEGINSPRODUCINGTHE快速运动的矢量,开始产生R波。图29DRWAVEFIGURE29DILLUSTRATESTHATTHE说明,最大矢量代表IMALVECTORREPRESENTSAPOINTINTIMEWHEN了大多数细胞去极化MOSTOFTHECELLSAREDEPOLARIZED,GIVINGRISETO的时间点,产生R波THEPEAKOFTHERWAVEINFIGURE29E,THE的峰。图29E是激动FINALPHASEOFVENTRICULARDEPOLARIZATIONOCCURS向心室的基底部向图的顶部传播时的心室ASTHEEXCITATIONSPREADSTOWARDTHEBASEOFTHE去极化的终末时相,VENTRICLESTOTHETOPINTHEPICTUREGIVINGRISE产生S波。TOTHESWAVE215THESTANDARDLIMB215标准肢体导联LEADSFROMKIRCHHOFFSVOLTAGESLAW,THESUMOFTHEVOLTAGESAROUNDALOOPEQUALSZEROTHUSIIIIII026FIGURE210LEADSI,IIANDIIIARETHEPOTENTIALSDIFFERENCEBETWEENTHELIMBSASINDICATEDRAANDLAARETHERIGHTANDLEFTARMSANDLLISTHELEFTLEG216THEAUGMENTEDLIMBLEADS216加压肢体导联FROMTHEBOTTOMLEFTLOOPIRIRII028ORIRII/229FROMTHEBOTTOMRIGHTLOOPIRIIIAVL0210ORAVLIRIII211COMBININGEQS29AND211GIVESAVLII/2IIIII2III/2212FROMTHETOPCENTERLOOPFIGURE211THEAUGMENTEDIIIIII213LIMBLEADAVLISMEASUREDSUBSTITUTINGGIVESASSHOWNAVLIIII2III/2IIII/221422ECSLEADSYSTEMS22心电导联系统THEREARETHREEBASICLEADSYSTEMS心电学中有三种常用的基USEDINCARDIOLOGYTHEMOST本导联系统。最通用的是POPULARISTHE12LEADAPPROACH,12导联方法,该法定义WHICHDEFINESTHESETOF12了12种电位差的集合,POTENTIALDIFFERENCESTHATMAKEUP构成标准临床ECG。第THESTANDARDCLINICALECGA二种导联系统规定了记录SECONDLEADSYSTEMDESIGNATESTHEVCG的电极位置。典型LOCATIONOFELECTRODESFOR的监护系统只分析1或2RECORDINGVCGMONITORING个导联。SYSTEMSTYPICALLYANALYZEONEORTWOLEADS22112LEADECS22112导联心电FIGURE216STANDARD12LEADCLINICALELECTROCARDIOGRAMALEADIBLEADIICLEADIIINOTETHEAMPLIFIERPOLARITYFOREACHOFTHESELIMBLEADSDAVREVLFAVFTHESEAUGMENTEDLEADSREQUIRERESISTORNETWORKSWHICHAVERAGETWOLIMBPOTENTIALSWHILERECORDINGTHETHIRDGTHESIXVLEADSARERECORDEDREFERENCEDTOWILSONSCENTRALTERMINALWHICHISTHEAVERAGEOFALLTHREELIMBPOTENTIALSEACHOFTHESIXLEADSLABELEDV1V6ARERECORDEDFROMADIFFERENTANATOMICALSITEONTHECHEST中心电端C相连。所有单极导联皆参考此点电压。所有输入端皆采用高输入阻抗电路。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电极安放的位置肢体导联监护导联FIGURE217THE12LEADECGOFANORMALPATIENTCALIBRATIONPULSESONTHELEFTSIDEDESIGNATE1MVTHERECORDINGSPEEDIS25MM/SEACHMINORDIVISIONISIMM,SOTHEMAJORDIVISIONARE5MMTHUSINLEADI,THERWAVEAMPLITUDEISABOUT11MVANDTHETIMEBETWEENBEATSISALMOST1SIE,HEARTRATEISABOUT60BPMTHENOTESAREID0042804,S26,L2,C1,I,II,III,AVR,AVL,AVF,V1,V2,V3,V4,V5,V6,PATIENTNO4307400RESPECTIVELY222VCSLEADSYSTEM222向量心电导联系统FIGURE219THERESISTORNETWORKFORFIGURE218THEELECTRODECOMBININGBODYSURFACEPOTENTIALSTOPLACEMENTFORTHEFRANKPRODUCETHETHREETIMEVARYINGSCALARVECTORECSSYSTEMLEADSOFTHEFRANKVCSLEADSYSTEMFIGURE220THEVECTORCARDIOGRAMOFANORMALMALEPATIENTTHETHREETIMEVARYINGSCALARLEADSFORONEHEARTBEATARESHOWNONTHELEFTANDARETHEX,YANDZLEADSFROMTOPTOBOTTOMINTHETOPCENTERISTHEFRONTALVIEWOFTHETIPOFTHEVECTORASITMOVESTHROUGHOUTONECOMPUTEDHEARTBEATINBOTTOMCENTERISATRANSVERSEVIEWOFTHEVECTORLOOPLOOKINGDOWNFROMABOVETHEPATIENTONTHEFARRIGHTISALEFTSAGITTALVIEWLOOKIN