超高场强磁共振下DBS电极周围组织的病理改变

,MR-DBSInducedThermalInjuryontheBrain,Whythistopic,1,MRcompatibilitywithDBSonanimals.2,HarshrequirementsofclinicalMR-DBS.,IndicationsofMR-DBS,AccordingtoMRIguidelinesforDBS，whenMRcannotbesubstitutedbyotherexaminationslikeCTorultrasonic，thepatientwithDBScanundergoMR，IPGbeingturnedoff.11.5TMR，T-Rheadcoil2headSAR(specificabsorptionrate)0.1W/KG3dB/dt20T/s,Contraindicationsonspecification,1，otherartificialimplants2，anesthetizedpatients3，othersubstituteexaminationavailable4，bodycoil,headTcoilorheadRcoil5，not1.5T,Medtronicsvouch,Introduction,DBS:aleadingtoolforFunctionalNeurosurgery，appliedforessentialtremor(1997),PD(2002),dystonia(2003)(FDA)。Future:epilepsy,obsession,majordepressionandchronicpain.,Introduction,From2003,100,000patientsreceivedDBStreatmentglobally,morethan4000inChina,manyofwhichneedMRassistanceforguidenceoffurthertreatment.,Introduction,WhatwillhappenwhenpatientswithDBSundergoMRexamination?+=?,First,takealookatreportsonmedicaldevicesinducedthermalinjuryduringMRexamination.,Cases,1991,GBashein:acaseoffull-thicknessskinburninjuryinthevicinityofoxymeteraftercervicalMRscanning.acaseofsuperficialthighskinburninjurybeneaththeoxymeterwireafterheadMR.,Cases,1992,StevenG:acaseoflargeareaofsecond-degreeburninaxillaafterlumbosacralMR.Aspecificallydesignednon-MR-disruptivethermometerwassuspectedtobethecause.1996,Jones：FullthicknessburnattheECGcontactafterMR1997,Jackson:EyelidedemaandcongestionafterheadMR,probablyduetothepigmentationofeyelinerwhichcontainsmetal,WillMR-DBSleadtoburn?Themechanismsoftheheating.HowtoensurethesafetyofpatientswithDBSinfaceofMR?,Contents,IntroductionforMRheatingofconductsMechanismsofMR-DBSheatingBrainthermaldamageConfirmationofthermaldamageCases,IntroductionforMRheatingofconducts,MagneticResonnance,MRprinciples,MRprinciples,FeaturesofMRmagneticfield,3sortsofmagneticfieldsinMRa,Static-atalltimes，magnetictorque；b,gradient-scanning，framing；c,RF-scanning，energyleveltransitionRadiofrequency(RF)：03000GHzradar,television,phoneMR-RF-shortwave,ultrahighfrequency,RFheating,RFheatingaoverallheating-heatstressblocalheating-thermaldamage,SAR：measuringthequantityofRFenergythatisabsorbedbythebody,W/kg.influencedbyRFfrequency,type,coils,tissuemass,configuration,etc.mass=50%RFwavelenth，SARmax,Heatingmechanismsofconducts,1,ElectromagneticinductionprobableinMR-DBSclosedcircuit（IPG-wire-lead-body）-changeofmagneticflux-inducedvoltage-inducedcurrent-Jouleheat,Electromagneticinduction,HeatingofElectromagneticinductionArtificialcochlea(60C.,Caseforresonance,InsideMRcoil,LocalTEMPrise60C/30s,(Rcoil)outsideMRcoil,TEMPrisenotmuch(T-Rcoil),Heatingmechanismsofconducts,3,AntennaeffectpossibleinMR-DBSWiresofDBSlead,oxymeter,ECG,EEGareallantenna,receivingRFenergy.Antenna=1/2wavelenth:maxreception.Powerreceivedwillbereleasedonthetip,Antennaeffect,TEMPrise60C,Phantomtests：electrodeofspinalstimulator2-11C；ECGcontact69C,intravescularGUIDING72C。,WillMRcauseTEMPrise?,15volunteers:routineheadMR,multispotsTEMP(sublingualpocket,skin,rectum).Skin:0.2-2.0C,Core:0.Another,7.55T,AverageSAR6.0,multispot(esophagus,tympanic,dura,scrotum,eyeball)NodetrimentalTEMPrise(0.2-2.0C)Eye,testis(worstcoolingorgan)routineMR:TEMP36C(widelyaccepteddamagingTEMP:41-55C),WillMRcauseTEMPrise?,Animal:SAR4.0,RF,noelevationincore.SAR4.0,RF,slightrisenotsignificant,withchangeofheatdissipation,dogtonguesticking，rattailsecreting,whichoccurewhen38-40C.,MechanismsofMR-DBSheating,MechanismsofMR-DBSheating,RFpower-antenna-closedcircuit-changeofmagneticflux-inducedvoltage-inducedcurrent-JouleheatsimilartoRFpallidotomy,TEMPchangeofDBSlead,Rezai,phantom,1.5T,body:2.5-25.3,head:2.3-7.1,body：6.1(extrawiresurroundingburhole)25.3(surroundingIPG)head：2.3,Extrawiresintosmallloopswithchangingdiametersonthelevelofburhole.Left:open,Right:filled.1.5T,3.0T.0-2.75loops,1.5T:1.8-10.3C3.0T:0.8-7.3CSmallloopsreduceheatingofMR-DBS,NumericalmodelofMR-DBSheating,Maged,JNeuroengineer:Sumerizedplentyoftestsin-vitro,ex-vivoandin-vivo,constructednumericalmodel:DBS:M3389(1.5mm-0.5mm)andM3387(1.5mm-1.5mm).,M3389heatdistributionindifferentheatconductionrates（k=0.026,30,300）k(diamond)800-2000,k(d-likecarbon)30-40,TofDBSelectrodeinnormaloperation(0-1.75v)andMR-RF(1.75-5v),Fourki,3T,7TMR-DBS,gelphantom,SAR3,extrawire:loop;top,side,front.T:3T7T,T:sidetopfront,max:8.2/7.6Cexceptforsideloop,7TT2C,3TT4.5C6mmTslightlylessthancontacts.,Brainthermaldamage,Cellulardamageduetothermalinjury,Changeinmembraneconductance,enzymeactivity,actionpotentialthreshold.Ionaccumulation,malfunctionofcellularorgan,enzymeinactivation.,Thermaldamageofthebrain,CEM43，cumulativeequivalentperminindicatingheatdamageofdifferentcouplesofTandtCEM43=tR43-T，431min=4515s=401h,Thresholdforbrainthermaldamage,Dewhirst:Threshold:43C43C1min=heatdamage17min=evidentlydamaged60Cseveralseconds=necrosisHoops:43C1h=deathofneurons,Confirmationofthermaldamage,Pathologicalchanges,Heatsensitivity:neuronglialvesepithllReversibledamage:edema(ballon,lightlydyed）Irreversibledamage：Necrosis:swelling,karyopyknosis,karyorrhexis,karyolysisApoptosis:shrinking,celldensitification,chromotinmargination,apoptoticbody.Biochemistry180-200bpDNALadder.Redneuron：acutenecrosis.,Detectionofheatinjury,Wholebodyheating:sensitivetissueapoptosislocaloverheat:acutedamagenecrosis-transition-normal2happtssstart,24happtssmaxDetection:electronmicroscope,DNALADDER,TUNELdyeing,Molecularbiology-HSP70,HSP70：constitutional:prmolecularfoldingstress:wholebodyorlocal,heating,trauma,stressandseizure,decreasingcelldamage.LegalMedicine2012/EPResrch2011:stressorlocaldamageleadtoHSP70prandmRNArisesignificantly.,Cases,WhenstickingtoMRguideline,Kovacs:34MR-DBSsafeLarson:746DBS,1000MR,transientpain,safeChharbra:64,safeUllman:21DBShead,9beforedeath1.5TMR，Notissuedamagearoundelectrodes.4ex-vivo3.0TMR.Notissuedamage,Cases,2003,JNeurosurgery,JorgSpiegel:73y,F,PD,tremor,bilateralSTN-DBS,IIphasesM7428.Externalstimulation:righttremordisappear,leftdecreasesignificantly,slightdysarthria,nomovementenhancement.HeadMR(1.0T,T-Rhead),externallead:outsidecoil,straight,noinsulationdisorder.AfterMR,distonia,leftlegballisticmovement:leftfootcontinuousspasmicdorsalflexionandexternalextension.leftkneeballisticextension.Whenrightstimulatorturnson,thesymptomsgoworse.CT:negative.Gradu