DTI數(shù)據(jù)分析及應(yīng)用課件

DTI數(shù)據(jù)分析及應(yīng)用1精選課件pptPage2內(nèi)容提綱DTI的研究內(nèi)容DTI數(shù)據(jù)處理流程DTIStudioFSL:FMRIB’sDiffusionToolbox2精選課件pptPage3擴散張量成像的研究內(nèi)容纖維跟蹤算法基于DTI的應(yīng)用研究3精選課件pptDxyxyDyyDyz=(v1v2v3)0λ20擴散張量的數(shù)學描述D=

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v2DxzDyzDzz00λ3v34精選課件pptPage5確定性跟蹤算法跟蹤終止條件Morietal.,AnnNeurol,19995精選課件pptPage6確定性跟蹤結(jié)果Catanietal,Brain,2005粗大的白質(zhì)纖維束6精選課件pptUncertaintyPage7纖維走向的不確定性Jones,MRM,2003LinearityBootstrap方法7精選課件pptPage8概率跟蹤算法DirectionUncertaintyDTINoisePartialVolumeEffectsSlidefromTriNgo8精選課件pptPage9概率跟蹤的方法Non-parametric(modelfree)approachesBootstrapmethodHARDI:Q-ball,DSIParametricapproachesPriorknowledgeandmodels:BayesianframeworkProbabilitydensityfunction(PDF):local,globalHowtoestimatethedistributionoffiberorientationswithinavoxel?9精選課件pptPage10

概率跟蹤的思想Reference:Behrens,T.E.etal.Characterizationandpropagationofuncertaintyindiffusion-weightedMRimaging.MagnResonMed50,1077-88(2003).10精選課件pptPage11概率跟蹤結(jié)果Frimanetal,IEEETMI,200611精選課件pptPage12概率跟蹤的優(yōu)點：估計纖維走向的不確定性,一定程度上解決纖維交叉問題研究FA較低的灰質(zhì)腦區(qū)之間的解剖連接跟蹤結(jié)果對噪聲更穩(wěn)定定量描述空間任意兩個體素之間的連接概率概率跟蹤的缺點：需要采集較多梯度方向的DTI圖像計算量大，耗時12精選課件pptPage13Connectivity-basedclassificationof thalamicvoxelsproducesclustersBehrensetal,NatureNeuroscience,200313精選課件pptPage14ImprovementsonthediffusiontensormodelsinglefibremultiplefibresSlidefromSaadJbabdi14精選課件pptPage15確定性跟蹤常用軟件:DTIStudio,MedINRIA,3DSlicer等概率跟蹤常用軟件：FSL15精選課件pptPage16擴散張量成像的研究內(nèi)容纖維跟蹤算法基于DTI的應(yīng)用研究16精選課件pptPage17擴散屬性測度以上三種情況的ADC=0.7x10-3mm2/s17精選課件pptPage1818精選課件pptPage1919精選課件pptPage2020精選課件pptPage21基于擴散屬性測度的臨床研究基于全腦配準的分析方法基于體素的統(tǒng)計分析（VBA）基于白質(zhì)骨架的空間統(tǒng)計分析（TBSS）基于感興趣區(qū)的分析方法手工畫感興趣區(qū)的方法基于纖維重建的定量分析21精選課件pptPage22Voxel-BasedAnalysis(VBA)VBMonFA(Ashburner,2000;Rugg-Gunn,2001)StrengthsFullyautomated&quickInvestigationwholebrainImplementationstepsPreprocessingNormalizationofFAimagesSmoothVoxelwisestatistics(e.g.controls–patients)IssuesAlignmentdifficult;smallestsystematicshiftsbetweengroupscanbeincorrectlyinterpretedasFAchangeNoobjectivewaytochoosesmoothingextent(6,8or10mm?)22精選課件pptPage2323精選課件pptPage2424精選課件pptPage2525精選課件pptPage2626精選課件pptPage2727精選課件pptPage2828精選課件pptPage2929精選課件pptPage3030精選課件ppt精神分裂癥患者的VBA分析

FA降低的腦區(qū)：????????cerebralpeduncle;frontalregions;inferiortemporalgyrus;medialparietallobes;hippocampalgyrus;Insula;rightanteriorcingulumbundle;rightcoronaradiata

Page31Haoetal.Neuroreport200631精選課件pptPage32Tract-BasedSpatialStatistics(TBSS)PartofFSLsoftware()OvercomethedrawbacksinVBAmethod,suchasalignmentissueandsmoothingissueFlowchart32精選課件pptPage33TBSSstepsindetail:preprocessing-createFAimagesfromyourdiffusionstudydatatbss_1_preproc-prepareyourFAdatainyourTBSSworkingdirectoryintherightformattbss_2_reg-applynonlinearregistrationofallFAimagesintostandardspacetbss_3_postreg-createthemeanFAimageandskeletoniseittbss_4_prestats-projectallsubjects'FAdataontothemeanFAskeletonstats(e.g.,randomise)-feedthe4DprojectedFAdataintoGLMmodellingandthresholdinginordertofindvoxelswhichcorrelatewithyourmodel.33精選課件pptPage34Docross-subjectvoxelwisestatsonskeleton-projectedFA34精選課件pptPage35Fig.TBSSresultsfrom15MSpatients.A,B:3DsurfacerenderingsofthemeanFAskeleton.C:YellowshowsthewhereFAcorrelatesnegativelywithEDSSdisabilityscore.D:Redasabove.InCandD,greenshowsthemeanFAskeleton,blueshowsthegroupmeanlesiondistribution,andthebackgroundimageistheMNI152.Smithetal.,NeuroImage,200635精選課件pptPage36Scholzetal.,NatureNeuroscience200936精選課件pptPage37TBSSdataacquisitionrequirement:

Voxelsizeshouldbelessthan3×3×3mm3.Atleastoneb=0shouldbeacquired;ideallyoneb=0imageforeveryeightdiffusion-weightedimages.b-valueshouldbeatleast800s/mm2.Atleastsix-gradientdirectionsmustbeacquired.itisbettertousemoreuniquesamplingdirections(withisotropicangulardensity18)thantoobtainrepeatsamplesofthesamesetofdirections.SNRinthediffusion-weightedimagesshouldbemaximized.AnexampleprotocolthatshouldleadtosufficientlyhighSNRishavingb=1,000smm–2,24diffusion-weightedimagesandSNRgreaterthan15intheb=0image.37精選課件pptPage38Thedatashouldnotbeupsampled(e.g.,throughunfilteredzero-paddingduringreconstruction)ifthisisdoneinsuchawayastointroduceringingintothedata.Ifmultiplerepeatsofb=0ordiffusion-weightedimagesaretobeacquired,theymustnotbeaveragedonthescanner(astheymustbecoregisteredbeforeaveraging,andanyriskofaveragingthecomplexdatashouldbeavoided).Fatsaturationshouldbeusedwheneverpossibletoremovesignalfromthescalp,whichcandisruptsignalinthebrainowingtochemicalshiftorghostingartifacts.Avitamincapsuleleft–rightmarker(oil,notwater)shouldbeattachedtotherightsideoftheheadtoavoidanyleft–rightambiguitiesduringdataconversionandanalysis.38精選課件pptPage39Computingequipment:Unix-basedcomputers.AppleMac(runningMacOSXversion10.4orhigher)andPCs(runningLinuxflavorsRedHat9,Enterprise,FC4,Suse9.0-9.3orDebian)HighRAMrequirements(particularlyiftensofsubjectsareusedinastudy),itislikelythatthecomputerwillneedtobe64bit.Thecomputershouldhaveatleasta1GHzCPUclock,1GBRAM,5GBs20GBfreeharddiskspace.Ifmultiplenetworkedcomputers(oracomputercluster)areavailable,theregistrationstepscanbeparallelized,greatlyreducingthetotalcomputationtime.39精選課件pptPage40白質(zhì)纖維束的定量分析FA:LeftCingulum(Red)>RightCingulum(Blue)ParameterizationprocessGongetal,HumanBrainMapping,200540精選課件pptPage41同正常人相比，早期盲人的視放射白質(zhì)擴散異常，F(xiàn)A值顯著降低，ADC和λ23顯著升高。早期盲人大腦白質(zhì)擴散異常研究Shuetal,HumanBrainMapping,200941精選課件pptPage42單張量模型的假設(shè)無法解決纖維交叉問題纖維跟蹤技術(shù)的準確性缺乏嚴格的評價體系擴散張量成像的局限性42精選課件pptPage43內(nèi)容提綱DTI的研究內(nèi)容DTI數(shù)據(jù)處理流程DTIStudioFSL:FMRIB’sDiffusionToolbox43精選課件pptPage44數(shù)據(jù)處理的基本流程44精選課件pptPage45

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S5S6……45精選課件pptPage46PreprocessingDICOMdataconversionImagequalitycheckEddycurrentcorrection46精選課件pptPage47內(nèi)容提綱DTI的研究內(nèi)容DTI數(shù)據(jù)處理流程DTIStudioFSL:FMRIB’sDiffusionToolbox47精選課件pptPage48DTIStudioDownload&InstallUserManualMailinglist48精選課件pptPage49LaunchingtheProgramandHardwareRequirementDtiStudio-latest-x86.exeforWindowssystemMorethan1GBRAMisrecommended49精選課件pptPage50MainFunctionsImageViewerDiffusionTensorCalculationFiberTrackingandEditing3DVisualizationImageROIDrawingandStatistics50精選課件pptPage51Howtodotensorcalculationandfibertracking?51精選課件pptPage52E:\work\Training\ExampleDataRawdata:MRIcroNdcm2nii.exe(.img,.hdr,.bvec,.bval)Eddycurrentcorrection:AIRTensor,FA,MDcalculation:DTIstudioFibertractography:DTIstudioROIselection52精選課件pptPage53第一步：對原始DICOM數(shù)據(jù)進行格式轉(zhuǎn)換。利用MRIcroN軟件中的dcm2nii.exe工具，將DTI原始數(shù)據(jù)文件夾拖入，即可得到DTI掃描的梯度編碼文件.bval和.bvec，以及轉(zhuǎn)換后的NIFTI格式的圖像文件（OutputFormat選擇4DNIfTIhdr/img）。53精選課件pptPage54第二步：對DTI圖像進行頭動和渦流校正。打開DTIstudio,File->MRIView3D,選中上一步得到的4D.img文件，ImageParameters中選擇Image為Analyze，點擊OK，然后在Image面板ImageProcessing區(qū)域選擇AutomaticImageRegistration(AIR)，按圖3進行設(shè)置，然后點擊OK，等圖像配準完成后，在Image面板的OrthogonalViews區(qū)域的文件下拉框中看到Air_開頭的一系列文件，為校正后的DTI圖像文件，點擊Save，將Air_開頭的所有文件選中，選擇RawData，保存為一個4D的.dat文件。MRIView3D參數(shù)54精選課件pptPage55AIR的參數(shù)設(shè)置55精選課件pptPage56頭動和渦流校正后的DTI圖像保存56精選課件pptPage57第三步：張量解算以及FA,ADC等擴散指標的計算。打開DTIstudio,File->DTIMapping,選擇PhilipsREC格式，Continue，按圖5進行參數(shù)設(shè)置，Addafile中選中上一步保存的4D.dat文件，點擊OK，在DtiMap面板的Calculation區(qū)域選中Tensor,ColorMapetc.（計算ADC值選擇ADC-Map），根據(jù)圖像選擇噪聲水平，點擊OK，然后等DTIStudio算完后在Image面板的OrthogonalView區(qū)域可看到計算出來的各種擴散屬性文件。對于想要保存的文件，如FA,EigenVector-0，ColorMap-0等可以分別進行Save（.dat格式），便于下一次查看和使用。57精選課件pptPage58DtiMap面板進行張量解算58精選課件pptPage59各種擴散屬性的顯示59精選課件pptPage60第四步：纖維跟蹤及可視化。第一種方法：基于前面步驟，在DtiMap面板的FiberTracking區(qū)域點擊FiberTracking，然后進行參數(shù)設(shè)置，點擊OK，就會進行基于全腦體素（FA>0.2）的纖維重建；第二種方法：如果上一步已保存FA和EigenVector-0文件，可重新打開DTIStudio,File->Fiber-Tracking，選上FA-Map文件和PrincipleVector文件，并進行參數(shù)設(shè)置，點擊OK，就會進行基于全腦體素（FA>0.2）的纖維重建。通過任何一種方法，算完后右下角會出現(xiàn)Fiber面板，再此面板中可以對特定纖維束進行顯示和編輯，并可以對纖維屬性進行統(tǒng)計分析。60精選課件pptPage61纖維跟蹤方法261精選課件pptPage62纖維跟蹤的參數(shù)設(shè)置62精選課件pptPage63重建纖維束的可視化63精選課件pptPage6464精選課件pptPage65MajorwhitemattertractsReference:WakanaS,CaprihanA,PanzenboeckMM,etal.,Reproducibilityofquantitativetractographymethodsappliedtocerebralwhitematter.Neuroimage,2007,36(3):630-644.65精選課件pptPage66纖維屬性的統(tǒng)計分析66精選課件pptPage67NewModulesROIEditorROI