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1、BehaviouralNeurology21(2009)394939DOI10.3233/BEN-2009-0234IOSPressDiffusiontensorimaginginAlzheimersdiseaseandmildcognitiveimpairmentG.T.Stebbins∗andC.M.MurphyDepartmentofNeurologicalSciences,RushUniversityMedicalCenter,Chicago,IL,USAAbstract.Structuralmagneticresonanceimaging(MRI)studiesofAlzheim
2、ersdiseaseandmildcognitiveimpairment(MCI)havefocusedonthehippocampusandentorhinalcortex;graymatterstructuresinthemedialtemporallobe.FewstudieshaveinvestigatedtheintegrityofwhitematterinpatientswithADorMCI.Diffusiontensorimaging(DTI)isaMRItechniquethatallowsfortheinterrogationofthemicrostructuralin
3、tegrityofwhitematter.Basedonincreasesintranslationaldiffusion(meandiffusivity:MD)anddecreasesdirectionaldiffusion(fractionalanisotropy:FA)damagetowhitemattercanbeassessed.StudieshaveidentifiedregionsofincreasedMDanddecreasedFAinpatientswithADandMCIinalllobesofthebrain,aswellasmedialtemporallobestru
4、cturesincludingthehippocampus,entorhinalcortexandparahippocampalwhitematter.ThepatternofwhitematterintegritydisruptiontendstofollowananteriortoposteriorgradientwithgreaterdamagenotedinposteriorregionsinADandMCI.Recentstudieshaveexploitedinter-voxeldirectionalsimilaritiestodevelopmodelsofwhitematte
5、rpathways,andhaveusedthesemodelstoassesstheintegrityofinter-cerebralconnections.Particularfocushasbeenappliedtotheparahippocampalwhitematter(includingtheperforantpath)andtheposteriorcingulum.AlthoughmanystudieshavefoundDTIindicatorsofimpairedwhitematterinADandMCI,otherstudieshavefailedtodetectanyd
6、ifferencesinMDorFAbetweenthegroups,demonstratingtheneedforlargereplicativestudies.DTIisanevolvingtechniqueandadvancesinitsapplicationoughttoprovidenewinsightsintoADandMCI.Keywords:Dementia,fractionalanisotropy,meandiffusivity,perforantpath,tractography,entorhinalcortex,magneticresonanceimaging,hip
7、pocampus,memory,medialtemporallobe1.Introductionmorevariablepatternofadditionalcognitiveandotherdeficits[56,79,94].Memorydeclineisoneofthemostcommoncog-Non-dementedindividualwithmemorycomplaintsnitivecomplaintsint
