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1、汕头大学硕士学位论文血流量水平接近脑缺血半暗带阈值，这表明CEST图像所显示的病灶范围接近于缺血半暗带。运用化学交换饱和转移序列不但在诊断超急性期脑梗塞方面有很大优势，而且很可能在预测缺血半暗带方面也具有重要的临床意义。关键词：化学交换饱和转移；pH成像；脑梗塞；1.5T。II汕头大学硕士学位论文AbstractObjectiveCerebralinfarctionistheblockageoftheflowofbloodtothecerebrum,causingorresultinginbraintissuedeath
2、.Earlydiagnosisandrapidtreatmentwouldhelptoalleviatesymptoms,increasesurvival,andreducedisability.Inthehyperacuteinfarctstage,routineCTandMRI(T1WI,T2WIandFLAIR)usuallyarenegative.PWIandDWIpresentasalowperfusionareaandhyperintensityareainthisstage,buttheyarearenot
3、penumbra-specific.Thereforeanewtechnologywhichcanmakeanearlydiagnosisandprognoseischemicpenumbraisgreatsignificantforclinic.CESTimagingisanewtechnologywhichissensitivetopHchange.Asweknow,whencerebralnervoustissuelacksofbloodandoxygen,neurocyteisalteredinmetabolis
4、m,followingwithacid-basedisturbance.SopH-sensitiveCESTimagingcanreflectthealterationinmetabolism.Usingthistechnologytoimageischemicbrainmaymakeanearlydetectioninthehyperacuteinfarctstageandhaveaadvantagetoprognoseischemicpenumbra.MaterialsandMethodsInourstudy,twe
5、lvemalecatsweighing2.4to2.8kgunderwentpermanentmiddlecerebralarteryocclusion(MCAO),andischemicevolutionwasobservedataclinical1.5-TscannerthroughclinicalT1WI,T2WI,DWIandtheCEST-imagingthattheimagingsequencedesignedbyourgroup.CEST-imagingreadoutwasasspin-echoimagin
6、gwithanoffsetfrequencyof3.5ppm.Atlast,comparetheabilityofT1WI,T2WI,DWIandCEST-imagingtodetectcerebralinfarctwithinthehyperacutestage.ResultsIn7of12animals,whentherearenotanyalterationsintheDWIyet,wecanfindhypointensityregionsintheocclusionsideintheCEST-imaging.In
7、other5of12animals,wecanobservertheintensityalterationsinDWIandCEST-imagingatthesametime.ThesignalintensityinthelesionregionislowerthanthatIII汕头大学硕士学位论文inthehealthynervoustissueinCEST-imaging,andthedarkestpartintheCEST-imagingcorrespondswiththelightestpartintheDWI
8、.Itmaymeanthetissueofthisareasuffersthemostseriouslackofischemiaandanoxia.Inaddition,wecanseethelesionareadisplayedintheCEST-imagingislargerthanthatintheDWI.In
