ABSTRACT
Objective Toexploretheroleofmodel-basediterativereconstruction (MBIR)algorithminimprovingthequalityof thyroidCTimagesbyreducinghardeningartifactsattheentrancetothethorax.Methods ChestCTscansof20patientswiththyroidnoduleswere retrospectivelyreviewed.AlgorithmsofFBP,ASIR40,MBIRSTNDandMBIRNR40 wereusedtoreconstructatthe0.625mmslicethickness.Region ofinterestwasplacedonthecoronalimageswiththemostobvioushardeningartifacts.ThestandarddeviationsoftheCTvaluesof theleftandrightthyroidarteriesandthesurroundingnormalthyroidtissueweremeasured,furthermore,thevalueofthyroidartifact index(AI)andAI=sqrt(SDa2-SDb2)werecalculated.Tworadiologistsused4-pointmethodtoassessimageartifactssubjectivly.(1 point,severeartifacts,unclearthyroidrimsandnodules,undiagnosed;2points,moderateartifacts,poorlydisplayingthyroid margins andinternaldetails,affectivediagnosis;3points,mildartifacts,showingthyroid marginandinternaldetails,noaffectingthediagnosis;4 points ,no ribbon artifacts ,displaying thyroid edge and internal details very w ell ).ANOVA and paired t-test w ere used to co m pare the CTvaluesofnormalthyroidtissueofleftandrightlobeamongdifferentreconstructedimagesofthyroid.Subjectivescoredifferenceswere testedusingthe W ilcoxon symbolscale.Results ThevalueofCTreductionandAIatFBPandASIR40reconstructionimagesweresignificantly greaterthanthoseatMBIRSTNDandMBIRNR40reconstructionimages. Whiletherewerenodifferenceofleftandrightlobeofthyroid CTreductionand AIvalueatFBPand ASIR40reconstruction imagesnorthoseatMBIRSTNDandMBIRNR40reconstructionimages. SubjectiveevaluationofclavicleartifactswasincreasedatMBIRSTND and MBIRNR40image,andMBIRNR40imagehadoptimalsubjectiveevaluationresults(P<0.05).Conclusion MBIRcansignificantlyreducethe impactoftheclavicularharnesshardeningartifactsandnoiseonthethyroidanditsnodulesduringCTscans,especiallyoptimizingthe low-densitycontrastsettingofMBIRNR40.