简介：Segmentingwholeheartfromcardiaccomputedtomography(CTimagescanprovideanimportantbasisfortheevaluationofcardiacfunctionandhelpimprovetheaccuracyofclinicaldiagnosis.Manualsegmentationisthemostaccuratemethodforcardiacsegmentation.Butitistimeconsumingandnotsufficientlyreproducible.However,cliniciansstillrelyonthismethodinpracticalapplications.Soafullyautomaticmethodisneededtoimprovethesegmentationefficiency.Thispapeproposesaregistration-basedautomaticapproachforthree-dimensional(3DsegmentationofcardiacCTimages.TheproposedmethodutilizesthesimilarityocardiacCTimagesbetweendifferentindividuals,andusesregistrationtoachievethesegmentation.Affinetransformationisfirstlyimplementedtoachieveglobalcoarseregistration.Then,cubicB-splinesareusedtorefinethelocaldetailsinlocallyaccurateregistration.Mutualinformation(Ml)isusedasthesimilaritymeasure,andadaptivestochasticgradientdescent(ASGD)astheoptimizationalgorithm.Oumethodisappliedtothedual-sourcecardiacCTimagestosegmentwholeheartExperimentalresultsshowthattheproposedmethodcanautomaticallysegmentwholeheartfromcardiacCTimages.

简介：Interfacedebondingbetweenprosthesesandabutmentswasthemostfrequentfailuremodeofresin-bondedfixedpartialsdentures(RBFPDs)inclinic.ThepurposeofthisstudywastoinvestigatetheeffectofaccessoryretentionformsonthebondstrengthofRBFPDs.Threetypesof3Dfiniteelementmodelswereconstructed.ThemodelofposteriormetalplateRBFPDwithspoon-shapedocclusalrestseatsservedasthecontrol.Theremainingtwotypesofmodelsbasedonthecontroladdedtheretentionformdesignofthepinholeandaxialgrooverespectively.Theaxialorbuccolingualloadof150Nwasappliedontheprosthesis,firstpremolarandfirstmolarrespectively.Themaximumprincipalstressesoftheadhesivelayerindifferentmodelswerecalculated.Undertheloadofthesamemagnitude,thestressduetothebuccolingualloadwassignificantlyhigherthanthatduetotheaxialloadintheadhesivelayer.Theproximalshoulder,occlusalrestseatswallandtheproximalmarginadjacenttotheshoulderwerethehighriskregionwheretheadhesivelayerdamagedeasily.Comparedwiththecontrolmodel,thepinandgroovemodelscouldslightlydecreasethestressintheadhesivelayeraftertheaxialloading,whilethestressintheadhesivelayerdrasticallydecreasedafterhorizontalloadingandreducedby22%and31%respectively.TheseresultsindicatethatthehorizontalocclusalforcehasamoreseriousharmtothedebondingofRBFPDs.Inaddition,theaccessoryretentionforms(e.g.pinandaxialgrooveretentionforms)candecreasethestresslevelintheadhesivelayer,whichareconducivetoincreasetheload-bearingcapacityofRBFPDs.