MR

ChinMedSciJ

    ;June2000

    ;JoRART【CLES

    ;CHINESE

    ;MEDICALSCIENCES

    ;JOURNAL

    ;Vo1.15,No.2

    ;P.67—72

    ;MRIMAGINGOFCORONARYARTERYBYPASS

    ;GRAFT:APRELIMINARYSTUDY

    ;ZhuJiemin?(朱杰敏),ZhangZhuhua(张竹花)andLiuYuqirlg一(刘玉清)

    ;DepartmentofRadiology,PekingUnionMedicalCollogeHospital, ;CAMS&PUMC.Beijing100730

    ;一DepamnentofRadiology,CardiovascularInstituteandFuWai ;Hospital,CAMS&PUMC,Beijirlg100037

    ;Keywords(3oronaryarterybypass;magneticresonalleeimaging;flow ;0.Tomakeapreliminaryinvestigationofthepotencyandfunctionofcoronaryarteryb)ass

    ;(CABG)bymasticresonance(MR)imagesandtoestablishasuitablemethodf

orfollow-upstuayafterCABGopera—

    ;donamongChinese.

    ;Methods.MRimag~wasperfomaedwithaToshiba1.5-Tunitin27parle,itswith74grafls.仙patie.tswere

    ;examinedwithabr~h-ho]dECG-gatedtwo-dimemionalfastfieldecho(n)8eqllencetoevaluatethepateneyofby-

    ;pass,amongthem16patientswith42weref_u妇examinedwithaphaseshiftf

    瑚cs0f啪eax~iog-

    ;raphyflow(PSbtRAflow)sequencetoevaluatethegraflspatencyB.SwellB.Stheflowvelocityandflowvolume”V8.

    ;1L,rle.

    ;Resu/~.rllaeresultsshowedthat66ofthe74intheparle,itsofthepresentseriesstudiedwithFFEwere

    ;patentwithapatencyrateof89.2%.rllaeresultsevaluatedbothwithFFEandPSbtRAflowlremainedthesameexcept

    ;thattwograftswerepatentwithFFEandtheIetswithPSMRAflowwereuncertain.Diastolicpeffusionpattemcln”ve8

    ;werefoundin25ofthe32inpatientsofthepresentseries.ComparingtheflowCUlVe8oftheafleftinternal

    ;mammaryarterywithtI瞄

    eofthenativerightinternalmammaryarteryin7patie,lts,thesystolicpeakvelocityvalue

;(sev)ofthebedarterieswassignificantlylowerthanthatoftheungraftedOl’le

    8,whereasthediastolicpeakveloci-

    ;tyvalue(1)PV)andtheratioofDPVtoSPVweresignificantlygreaterthanthat

    oftheungrafedOl’le8.,

    ;

    (.IheFFEandPSbtRAflowsequenoeswereefficientinevaluatingpater1clya

    ndobklintIlecu艄of

    ;flowvelocityandvolumeofthebypassgrafts.’Therefore,theymayofferanon-invasivescreeningraethodforfollow-up

    ;stuayinpatie~afterCABGsurgery,-lthoughitsaccuracyshouldbefurthereva

    luatedinr/lorepatie.tsandc0曲一

    ;tivelystudiedwithothermethods.

    ;Coronaryarterybypassgraft(CABG)surgeryhasbe- ;ReceivedforpubfieadonMay26,1999

    ;Correspondingauthor.

    ;comeincreasinglypopularinourcountryinrecentyears. ;Thepostoperativeselectivecoronarygraftangio~aOlyre- ;mainsthe”goldstandard”toevaluatethepatencyofthe

    ;graft.However,asaninvasivemethodandforother嗍-

    ;sons,itisnotwillinglyacceptedbytheChinesepeople.To ;

    ;68C|?NESEMEDJCALscIENCESJOURNAL

    ;develop,therefore,anoninvasiveandeffectiveimaging ;modalityinevaluatingthepatencyofthegraftanditsped.u- ;sionreservefunctionisofclinicalimportance.

    ;Patients.Twenty-sevenpatients(male25andfemale ;2)underwentcoronarybypasssurgery.Agerangedfrom36 ;to69years(mean:56.1?9.5years).Thedurationfrom ;June20Do

    ;CABGsurgerytopost-operativeMRIexaminationvariedfrom ;1monthto7years.Accordingtothepatients’records.the

    ;resourcesaswellastheanastomoticsitesofthetotal74 ;graftswereshowninTable1.Nosymptomsofanginaormy- ;ocardialinfarctionwerefoundinanypatientsaftersurgery. ;Thosepatientswithpacemakers,artificialheartvalvesorre- ;mainingpacemakerstringswereexcludedbychestX-ray ;films.

    ;Table1.Resourcesof心andtheanastomoticsitetocoronaryarterie—

    ;s

    ;Note:LAD=leftanteriordescendingartery,LEX=leftcircumflexartery,RCA=rightcoronaryartery,:includingtheirmainbranches,native: ;theproximalpartofthegraftwasnotsevered,free:thegraftwasseveredandana

    stomosedonbothsides,othel’~:includinggraftstobranchesof

    ;LCX,branchofLCXandRCA,orbranchesofRCA.

;Rimag/ng.AT0SHIBAVISART1.5.TMRunit

    ;‘vithfieldstrength1.5Tandgradientstrength17rnrr/mwas

    ;usedforthisstudy.Breath.holdECG-gatedsegmentedtwo. ;dimensionalfastfieldecho(ra~E)sequenceimagingwasper- ;formedinallpatientstoassessgraftpatency.Inaddition ;ECG-gatedphaseshiftMRangiographyflow(PSMRAnow) ;sequenceimagingwasconductedin16patientswith42 ;grgts,amongwhichcurvesofflowvelocityandflowvolume ;versustimewereobtainedin13patients.Scanwasper- ;formedwithpatientsinpronepositionandasupinesurface ;coilwasused.Thetotaltimeofscaningwasaboutonehour. ;F1imagingparameterswereasfollows:repetition ;time(TR)15ms,echotime(TE)8ins,flipangle30~, ;fieldofview30em×30cm.slicethickness3to4mlnwitha ;gapof0IBm,andacquisitionmatrix128×256,spmialres- ;olution2.3lnln×1.2lnln,foroneacquisition,triggering ;delaytime50to60percentofR.Rintervaltoacquirethe ;dataduringthemid.diastolicphase.Flowcompensationand ;fat-suppressionpulsewereused.Afterobtainingend-expira—

    ;torybreathholdcoronalscout—film.F1imagingwiththe

    ;sa/nebreath—holdmethodwasperformedmainlyusinga

    ;tl’ansverseplaneaclCOSstheheartandasagitalplaneacross

;thepulmonaryartery.Eachbreath—holdtook10to18s.

    ;whichapproximatelyequaledthetimeof16heartbeats.Two ;FIimageswereshowninFigs1and2.

    ;PSMRAflowimagingparameterswereasfollows:,m25 ;l/is,,IE10ins,flipan对e20.,fieldofview24cm×24

    ;cm,slicethickness5mln,acquisitionmatrix160×256, ;spatialresolution1.5rain×0.9lnin.foroneacquisition. ;Fig1.TransverseFIrEimageatthelevelofpI山mary

    ;valve.Thegrafttorightcoronaryarteryisv~ual- ;izedasahighsignalneartherightanteriorsideof ;theaorta(small?),thenativeleftinternalmam—

    ;maryarterygraRtoleftanteriordescendingarteryis ;neartheleftanteriorsideofthepldIn【岫aIyvalve

    ;(1arge?),therightinternallrmlmmlyartery

    ;(1arge)andvein(smal1)arealsovisual—

    ;ized.

    ;andthephaseencodedirectionanteriortoposterior,nowrap ;addedonbothphaseencodeandread—outdirections.The

    ;dataacquiredwereonly80to90percentofR—Rinter—

    ;va1.Thevelocityencodingvaluewas50to90cm/sforthe ;

    ;CHINKSEMEDICALSCIENCESJOURNAL

    ;Fig2.sagittalFFEimagecrossingpulmonaryartery,high ;sigrlaldotsofthreegrafbinfrontofthepulmonary ;arteryarevisualized(sm~Lla),cross-sectionalim—

    ;ageoftheleftmaincoronaryarteryisalsovisualized ;(1argea).

    ;nativeintemalm舢nlaryarterygraft.whilethatfortheother ;田墨fwas35to50cnl//~.Withreferencetothebestcross—

    ;sectionalimageofthegraftonthesequence.thetrans—

    ;verseplanescarfingatthelevelofpulmonaryarterybifurca—

    ;tionwasperformedtoshowthenativeintemalmammary ;arterygraft,satalplanescaningacrossthepulmonary ;arterytoshowtheleftanteriordescending,diagonal,cir—

    ;Fig3.FourkindsofPSMRAflowimage~.A:protonimage;B: ;phasen’nage;C:flowimage;D:vesselimage.Ahigh

    ;signaldotwilt8visualizedinfrontofthepulmonaryartery ;onfouriIl1ag(?).

    ;cumflexorobtusemarginalarterygraft,andthetransverse ;planescanningabovetherightcoronarytoshowthegraftsof ;therightcoronaryartery.FromPSMRAflowimaging,four ;kindsofimagescanbeobtained(Fig3).3heprotonimage ;wasanori~nalgradientechoimagebeforesubtractionand ;wasusedtovisualizetheanatomicalstructures;andthe

    ;phaseimagewasusedtoobtainbloodflowvelocityandflow ;volumeCHIVes,onwhichthesignalmfl~teddephasedspin ;angle,whichvariedwithflowvelocity.3heflowilna窘eCOB—

    ;binedwiththevesselimagewereusedsupplementallyforob—

    sectionalvesselimages.3hesignalofthe ;servingcross—

    ;phaseandflowimagewasconectedwithflowdirection,and ;thecombinationofthesetwokindsofimageswasusedfor ;graftpatencyreevaluation.AhiIghsignalrepresentedcranial ;tocaudalandrighttoleftdirectionofflowwhereasnosignal ;representedthereversedirectionofflow.

    ;MR/cr/ter/aofCABGpatency.CABGpatencyisusual—

    ;lyclassifiedintothreecatogories:patent,uncertainlypatent ;andoccluded.Accordingtootherpublishedmfemnces(1—

    ;5),weadoptedthefollowingcriteriaofCABGpatency.On ;FFEimages,agraftvisualizedasaroundhighsignaldot ;withatleasttwocontinuousslicesisconsideredpatent;and ;anuncertainlypatentgraftisvis!lo|iz~asaroundhi【ghsig—

    ;naldotononlyonesilceoradotwithmoderatelyhighsignal ;intensityonatleasttwocontinuousslices.whiletheab唧ce

    ;ofahighormoderatelyhighsignaldotvis!mliz~donany ;sliceisconsideredanoccludedgraft.

    ;WithPSMARflowimages,agraftvisualizedasahigh

    ;signaldotonseveralprotonim~esaswellasatleasttwo ;flowimagesofdifferentphasesinonecardiaccycleiscon—

    ;sideredpatent.Whenasraftisvisualizedasahighsignal ;dotononlyoneprotonimage,thegraftisconsideredUilC~r—

    ;tainlypatent.Intheabsenceofahighsignaldotvisualized ;onanyprotonorflowimages,thesraftisconsideredocclud—

    ;ed.

    ;F/owve~/tya,~flowvolumestudy.Aflowstuaywas ;onlyevaluatedforthosepatentgraftswithPSMRAflowse—

    ;quence.Furthermore,thegraftshouldremainatthesiteon ;protonimagesofallphasesinonecardiaccycle.Drawthe ;regionofinterestaroundthehighsignaldotonphaseimages ;usingflowquantificationsoftwaretoobtainthecurvesofflow ;velocityandflowvolumevei’sustime.Accordingtoother

    ;publishedreforences(6,7),agraftisconsideredtohave ;goodfunctionifthecurvesshowadiastolicperfusionpat—

    ;tern,eitherwithtypicaltwopeal【sinthesystolicandthedi—

    ;astolicphasesandthepeakinthediastolicishigher ;thanthatinthesystolicphase(Fig4),orthetwopeaksare ;notveryprominent.buttheunderlyingareaoftheflowvol—

    ;unlecurveinthediastolicphaseislargerthanthatinthe ;systolicphase.

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    ;CHINESEMEDJCALSCIENCESJOURNAL

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