全文预览已结束
下载本文档
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
Correspondingauthor:ShaHong.email:sha_hong_2000SimulationStudyofElectrodeSystemOptimizationinElectricalImpedanceTomographyWangYan,RenChaoshi,ZhaoShu,WangLei,ShaHongInstituteofBiomedicalEngineeringChineseAcademyofMedicalSciences&PekingUnionMedicalCollegeTianjin,China.E-mail:sarahyky163.cmAbstractElectrodeliesinthefrontoftheElectricalimpedancetomography(EIT)systemandcontactswithhumanbodydirectly.ItisoneofthemostsensitiveandthepivotalpartsofEITsystem.Thetypeandtheconfigurationofelectrodesysteminfluencethereconstructionimagegreatly,especiallyforthecentralareaofbody,wherethemeasurementsensitivityisverylow.Asimulationplatformisdevelopedtooptimizetheelectrodestructureparameterbasedonthecoerciveequipotentialnodesmodelfortheimagingobjectofthedeepareaofbody.Theinfluencesonthemeasurementsensitivityandtheimagereconstructionqualityhavebeenstudiedusingdifferentelectrodetypesandconfigurations.Thesimulationresultssuggestthatoptimalselectionofelectrodetypesandconfigurationscanhelpfullyincreasetheimagequalityandmeasurementsensitivityoftheimageespeciallyincentralarea.SeveraltypeandconfigurationparameterofEITelectrodethatfitforcentralobjectimagingarealsopresented.Keywords-EIT;electrodesystem;reconstructionquality;measurementsensitivity;simulationevaluationI.0BINTRODUCTIONEITisoneoftheimportantresearchtopicsintodaysbiomedicalengineering1-3.EITelectrodearrayisoneofthemostsensitiveandthepivotalpartsofEITsystem.UsuallytenormoreelectrodesareusedinEITsystem.TheelectrodearrayliesinthefrontoftheEITsystemandcontactswithhumanbodydirectly.Thestructureandperformanceoftheelectrodesystemgreatlyinfluencetheoriginalinformationextraction,realtimepropertyofthesystem,imageresolvingpower,andespeciallytheinformationextractionfromcentralarea,wheretheEITmeasurementsensitivityispoor.Intheearlyoptimumstudyofelectrodeconfiguration,itiswidelyacceptedthatcurrentexcitationelectrodesshouldbeaslargeaspossiblewhilethevoltagemeasuringelectrodesarerequiredassmallaspossible4.PingHua5studiedtheinfluenceofcontactimpedancebetweenelectrodeandskin,andshowedthatthebesteffectcanbeobtainedwhenthetotalwidthofelectrodearrayisabout80-90%oftheimagedareasperimeter.E.J.Woo6usedannularcurrentandvoltageelectrodescovering90%ofthesurface.P.A.T.Pinheiro7reportedthattheoptimumareaunderneaththeelectrodesis80%oftheoverallboundaryareafortheadjacentpatternsand60%fortheoppositeones.WangChaoetal89carriedonthesimulationresearchontheinfluenceofelectrodewidthusingthecoerciveequipotentialnodefiniteelementmethod(FEM)model,andshowedthatthebesteffectwasobtainedwhentheoverlayrateofelectrodesis57.1%.AlthoughcontinuousprogressesonthechoiceofelectrodestructureparameterinEIThavebeenmade,thecompleteandsatisfactoryresulthasnotbeenseensofar.Inpractice,thedesignofEITelectrodestructureandparameterisstillbasedonexperience.AmongEITelectrodes,thecompoundelectrodehasmorecomplexstructure.FourparametersofthecompoundelectroderestricteachotherandtheirinfluenceonEITsystemaremuchcomplex.Theinfluencesofallparametersshouldbeconsideredcomprehensively.Usingonlytheoverlayrateofelectrodesisnotagoodwaytodealwiththecompoundelectrodeoptimizingdesign.InEITmeasurement,thecentralarea,correspondingtodeepareaofbody,isoftentheregionofinterest.Butthemeasurementsensitivityofthecentralareaisrelativelylowerandtheimagequalityisrelativelypoor.HowtoraisethemeasurementsensitivityandimprovetheimagequalityofthecentralareaisakeyprobleminEITmeasurement.TheexcitationpatternisalsoanimportfactorinEITmeasurement.Adjacentexcitationhasmoreindependentmeasurenumber.Oppositeexcitationpatternhaslessindependentmeasure,butthefielddistributionismorereasonablethanthatinadjacentpattern.Inthispaper,asimulationstudyofEITelectrodestructureandparameterdesignaimingattheimagingobjectofcentralareaispresented.Usingthecoerciveequipotentialnodemodelforcompoundelectrode10,asimulationplatformisdevelopedtocarryouttheoptimizingdesignoftheelectrodesystem.Basedonthemodelandtheplatform,theinfluencesoftheelectrodenumber,type,configuration,andexcitationpatternoftheelectrodesystemonthemeasurementsensitivityandtheimagereconstructionqualityhavebeenstudied.ThesimulationstudyofEITimagingwithdifferentdepthsofimagingobjecthasbeenmadewithequipotentialbackprojectionalgorithm.978-1-4244-4713-8/10/$25.002010IEEEII.1BMETHODA.4BFiniteElementModelforComplexElectrodesElectrodeplatesinroundorrectangleshapeareusuallyusedinEIT.Theprojectionsofbothelectrodesonthetomogramplanearealineandthelengthofthelineequalstothewidthoftheelectrodes,calledlineelectrode,asshownin(1)and(2)ofFig.1.Forthecompoundelectrodewithacomplexstructure,theprojectiononthetomogramplaneconsistsof3lines,asshownin(3)and(4)ofFig.1.Theexcitationelectrodeconsistsoftwolines,jinFig.1,ontheleftandtherightrespectively,andthemiddleline,cinFig.1,representsthemeasurementelectrode.Thereare4structureparametersforthecompoundelectrode(Fig.1),theexcitationelectrodewidthj,themeasurementelectrodewidthc,thespacebetweentheexcitationelectrodeandthemeasurementelectrodeb,andthedistancebetweentwoadjacentcompoundelectrodesa.EachofthemispresentedbythecountofFEMnodes.ForanEITelectrodesystemwithcertainboundary(suchas256nodesinthisstudy),whentheelectrodenumbers(32here)andelementsdividedinFEM(1210here)aredetermined,thesumofelectrodewideandthespacebetweenadjacentelectrodesisfixedtoo(8here).Figure1.ThelineelectrodeandcompoundelectrodeinEITAfiniteelementmethod(FEM)ofthecompoundelectrodeusingcoerciveequipotentialnodemodelhasusedtostudytheEITelectrodestructureparameteroptimizing10.B.5BEstimateFunctionsInordertoestimatetheinfluencesofelectrodestructureandparametersonthemeasurementsensitivityandtheimagereconstructionqualityinEIT,themeasurementsensitivityfunctionSandtheimagereconstructionqualityfunctionDaredefinedrespectivelyasfollows.1)10BThemeasurementsensitivityfunctionS%10011010=NiMjijSNMSHereMisthemeasurementnumbercorrespondingofonecurrentexcitation.Nisthenumberofcurrentexcitations.Sijdenotesthemeasurementsensitivityforjthmeasurementinithcurrentexcitation:0101=VVSijSijshowsthatthevoltageofthemeasurementelectrodechangesfromV0toV1whiletheconductanceofacertainregioninthemeasuredfieldchangesfrom0to1.SistheaveragesensitivityofallNtimesofexcitations.Itonlydependsontheelectricfielddistributionduetotheconductancechangeofthemeasuredregion,andisindependentofimagereconstructionalgorithmandhardwareerrors(supposethatsignaltonoiseratioofeachelectrodeisfixed).ThebiggertheSis,thehigherthemeasurementsensitivityis.2)11BTheImageReconstructionQualityFunctionD%100255)()(11=MpSpGpGiMD(p=1,2,M)HereMisthenumberofalltheelementsdividedintheimagingregion.Gs(p)isthegrayvalueofpthelementintheimagingmodel.Gi(p)isthegrayvalueofpthelementinthereconstructedimage.Dshowsthenormalizedaveragevalueofthegreyscaledifferencesbetweenthereconstructedimageandtheimagingmodelofeachelementintheimagingregion.Dsensitivelyreflectsthereconstructedimagequality.UsingD,thedifferencebetweenthereconstructedimageandtheimagingmodelcanbeevaluatedwithoutanyimageprocessing.ThesmallerDis,thelessthedifferencebetweenthereconstructedimageandtheimagingmodelis,thehigherthereconstructedimagequalityis.C.6BImagingModelsInthestudyofthispaperthetotalnumberoffiniteelementsis1210,including734nodes.Thereare256nodesonthecircumferenceofthemeasuredfield.6imagingmodelscorrespondingtodifferentmeasurementdepthhavebeenused(Fig.2).Theimagedobjectmovesfromtheboundarytothecentralareafrommodel1to6,andthemodel6istheimagedobjectofcentralarea,correspondingtodeepareaofbody.III.2BSIMULATIONEXPERIMENTANDRESULTA.7BEffectsofElectrodeNumberEITsystemwith8,16,32,64,128and256pointelectrodesareusedrespectivelyforstudy.TheestimateresultsusingfunctionsDfor6imagingmodelsinFig.1isshowninFig.3.Theimagingresultsofmodel3andmodel6areshowedinFig.4.B.EffectsofElectrodeTypeandStructureParameterThereconstructionimageshavebeenmadeusingthecoerciveequipotentialnodemethodforlineelectrodeandcompoundelectrode.Somecomparisonstudiesoftheparameterinfluencesonmeasurementsensitivityandreconstructionqualitybetweenlineelectrodeandcompoundelectrodehavebeencarriedout.Figure2.ImagingmodelsofdifferentdepthsFigure3.TheeffectsofelectrodenumberonimagequalityFigure4.Imagingresultswithdifferentelectrodenumberformodel3and6Thetotalwidthofbothlineelectrodeandcompoundelectrodearesettothesame.Asanexample,thewidthoflineelectrodeis5FEMnodes,whilecompoundelectrodehas3cases,inwhichthetotalwidthsofthemarealso5FEMnodes.Thefirsta=3,j=1,c=3andb=0,theseconda=3,j=1,c=1andb=1,thethirda=3,j=2,c=1andb=0.Theothercasesofdifferentwidthhavesimilarresult.ThefunctionsSandDofthereconstructionimagescorrespondingtoimagemodel6andmodel3respectivelyhavebeencalculatedandshownintableIandtableII.C.9BEffectofExcitationPatternTheeffectofexcitationpatternofEITonthereconstructedqualityandthemeasurementsensitivityhasinvestigated.Theexcitationpattern,whichdetermineshowthecurrentflowsintotheinterestingarea,influencesthedistributionofelectromagneticfielddirectly.Inthisstudy,theadjacent,intervalandoppositeexcitationmodeareused.Taken32electrodesasanexample,theexcitationcurrentisappliedbytwoelectrodes,andtheintervaloftheelectrodesischangedfrom1to16.Whentheintervalis1,itisadjacentexcitation.Andwhentheintervalis16,itisoppositeexcitation.Othercasesarecalledintervalexcitation,Fig.5.Thereconstructionresultsof32electrodesatintervalsof1,4,8,12,16electrodesrespectivelyhavebeenmadewiththeimagemodelsshowninFig.2.TheeffectsofexcitationpatternonimagequalityandmeasurementsensitivityhavebeenshowninFig.6andFig.7.TABLEI.COMPARISONOFLINEELECTRODEANDCOMPOUNDELECTRODEFORMODEL6TABLEII.COMPARISONOFLINEELECTRODEANDCOMPOUNDELECTRODEFORMODEL3Figure5.Adjacentexcitation,intervalexcitationandoppositeexcitationpatternFigure6.EffectsofexcitationpatternonimagequalityElectrodeTypeandStructureParameterDSLineelectrode:5nodeswide18.7060.003979a=3j=1c=3b=018.5840.003897a=3j=1c=1b=118.5760.003889a=3j=2c=1b=018.5890.003977ElectrodetypeandstructureparameterDSLineelectrode:5nodeswide14.3560.001871a=3j=1c=3b=014.6100.001836a=3j=1c=1b=114.4750.001831a=3j=2c=1b=014.4510.001875510152025308163264128256Delectrodecountmodel6model5model4model3model2model100.0050.010.0150.020.0251481216S%Intervalofcurrentelectrodesmodel6model5model4model3model2model1Figure7.EffectsofexcitationpatternonmeasurementsensitivityIV.3BRESULTSANDDISCUSSIONSFromFig3andFig4,itisshowedthatfornoncentralimagingobject,smallerelectrodenumberwillincreasethereconstructionerror.Butwhentheelectrodenumberturneduptoacertainextent,theimprovementbecamelesssignificant.Theimagequalityisalmostthesamewhenelectrodenumberismorethan64inthestudycondition.Fortheimagedobjectofcentralarea,especiallyformodel6,reconstructionqualityisverysimilar.Whentheelectrodenumberenlargedto128and256,theimagingqualityturnedabitworse.Thissuggeststhatforcentralobject,biggerelectrodenumbercannotbringbetterimagingquality.Inthispaper,the32and64electrodesystemisbetter.IntableI,fortheimagingobjectinthecentralarea,compoundelectrodehashigherimagequality,thanlineelectrode.AndintableII,fortheimagingobjectatsemi-radius,theeffectoflineelectrompoundelectrodeishelpedtoimproveimagequalityofthecentralarea.ThemeasurementsensitivitySoflineelectrodearealmostthesamewiththatofthethirdcaseofcompoundelectrode,andbetterthantheothertwocases,inbothtableIandII.Itmeansthat,ifthetotalelectrodewidthisfixed,themeasurementsensitivityisbetterwhenlargeexcitationelectrodehasbeenused.FromFig.6and7,itcanbeseenthatforeverydepthsofimagingobject,imagequalityturnsworseatintervalsofbiggerdistance,andthemeasurementsensitivityisincreasedsignificantly.Itisthesuggestionthatoptimizingofelectrodesystemaccordingtotheapplicationrequirement,forexampletheimagingobjectofdifferentdepthsandthedifferentexcitationpattern,isveryimportant.ThesimulationstudyofEITelectrodestructureandparameterdesignishelpfultogethighermeasurementsensitivityandgoodimagequality.12BREFERENCES1BarberD.C.andBrownB.H.,“Appliedpotentialtomography”,J.Phsy.E:Sci.instrum.,1984,17,pp.723-733.2Bro
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 2023年发射塔架、发射台以及移动发射装置相关项目计划书
- 工程意向合同样板
- 2024年竹藤家具项目资金需求报告
- 社会劳动合同制
- 承揽劳动合同案例
- 2024年医用真空负压机项目资金需求报告代可行性研究报告
- 2024年压缩式垃圾车项目资金需求报告
- 2023年悬架系统减震元件项目投资申请报告
- 五级综合布线职业技能鉴定备考题库大全-下(多选、判断题)
- 逾期物料重检单
- 工程变更联系单模板
- 电缆桥架、电缆安装施工方案(完整版)
- 电子商务创新创业教育研究.doc
- 110kV~750kV架空输电线路设计规范
- 深圳观澜湖维杰球场球道图及攻略
- 教育培训海明威《老人与海》艺术特色名著知识点梳理PPT模板
- 幼儿园安全工作领导小组职责与分工
- 飞行模拟器项目投资计划与经济效益分析
- 北师大版六年级数学下册期中测试卷附答案
- 组合把持器在封闭电炉中的应用
- 防毒面具规范
评论
0/150
提交评论