ITERATIVE IMAGE RECONSTRUCTION FOR DUAL-ENERGY X-RAY CT

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1、ITERATIVEIMAGERECONSTRUCTIONFORDUAL-ENERGYX-RAYCTUSINGREGULARIZEDMATERIALSINOGRAMESTIMATESWonseokHuhandJeffreyA.FesslerDepartmentofElectricalEngineeringandComputerScienceTheUniversityofMichigan1301BealAvenue,AnnArbor,MI48109-2122ABSTRACTThemeasurementsarefinite,butμ(x,E)isacontinuou

2、sX-rayCTimageshavevariousapplications,includingCT-functionofxandE.Thus,forreconstructionweparam-basedattenuationcorrection(CTAC)forPET.Low-doseCTeterizeμ(x,E)usingbasismaterialdecomposition[4]asimagingisparticularlydesirableforCTAC.Dual-energyfollows:L0Np(DE)CTimagingmethodsmayi

3、mprovetheaccuracyofμ(x,E)=βl(E)bj(x)ρlj,(2)attenuationcorrectioninPET.However,conventionalDECTl=1j=1approachestosinogrammaterialdecompositionuselogarith-mictransformsthataresensitivetonoiseinlow-dosescans.whereβl(E)denotestheenergy-dependentmass-attenuationThispaperdescribesaDErec

4、onstructionmethodbasedoncoefficient(MAC)ofthelthmaterialtype;weusetabulatedstatisticalmodelsthatavoidsusingalogarithm.WefirstMACvaluesforwaterandbone[5].{bj(x)}denotesunitlessestimatematerialsinogramsdirectlyfromtherawDEdataspatialbasisfunctionssuchassquarepixels,andρljare(withoutany

5、logarithm),withmildregularizationtocontrolunknowndensityoflthmaterialtypeatspatiallocationj.noiseandavoidoutliers.WethenapplyapenalizedweightedInDECT,weusuallychooseM0=2,L0=2.leastsquares(PWLS)methodtoreconstructimagesoftheSubstituting(2)into(1)yieldsthefollowingsimplifiedtwomaterial

6、components.Wealsoproposeajointedge-modelfortheensemblemeansofthemeasurements:preservingregularizerthatusesthepriorknowledgethatthey¯(s)=Ie−fmi(s)+r(3)twomaterialimageshavemanyregionedgeslocatedinthemimimisamepositions.Preliminarysimulationresultssuggestthatfmi(s)−logvmi(s)(4)thisi

7、terativemethodimprovesimagequalitycomparedtov(s)p(E)e−β(E)·sidE,conventionalapproachesbasedonlogdataforlow-doseDEmimiCTscans.form=1,...,M0,l=1,...,L0,andImi=Imi(E)dEdenotesthetotalintensityforthemthincidentspectrumandI.DUAL-ENERGYRECONSTRUCTIONtheithray,andwedefinethesinogramvector

8、siasfollows:I-A.Mea