文档摘要：超低场磁共振成像(ULF-MRI)设备具有成本低、质量轻、体积小等优点,在特殊领域的应用需求越来越大,如移动磁共振成像救护车、床旁监护、偏远地区等.但由于其磁场强度低,导致信噪比也较低,图像分辨率差,因此提升信噪比对促进ULF-MRI技术的发展具有重要意义.该文基于低频表面超材料的特性,提出一种电感-电容谐振阵列,用来提升ULF-MRI的信噪比.首先,建立了等效电路模型来评估磁场增强效果;其次,利用部分元等效电路法计算射频线圈的等效电阻和信噪比,根据成像要求设计优化谐振线圈结构,并提出考虑谐振耦合的匹配方法和线圈阵列的解耦方法.最后,利用自主研发的54.6mT的ULF-MRI系统(工作频率:2.32MHz)进行成像实验,图像信噪比得到显著提高.
Abstract：Ultra-lowfieldmagneticresonanceimaging(ULF-MRI)offersthebenefitsofcompactsizeandlightweight.However,theimagingsignal-to-noiseratio(SNR)islowerduetolimitationsinthemainmagneticfieldstrength.Thus,aresonantcoilarrayisusedforlocalizedsignalenhancementinULF-MRIat54.6mT(atafrequencyof2.32MHz).Giventhesignificantfrequencycontrastwithhigh-fieldMRI,theapplicationanddesignapproachforresonantcoilsinULF-MRIispresented.Theprincipleisexplainedusinganequivalentcircuit.Theresonantcoilispositionedonthesurfaceofthesample,coaxiallyalignedwiththeradiofrequency(RF)receivingcoilformaximumenhancement.It'stunedtotheresonantfrequencywithanadditionalcapacitor.DuringRFreception,thecoilamplifiesthelocalRFmagneticfield,enhancingthereceivedmagneticresonancesignalsandimprovingtheSNRoftheimage.Amatchingmethodforthereceivingcoilwiththeresonancecoilisintroduced.Duetothestrongcouplingbetweentheresonantcoilandthereceivingcoil,traditionalmethodsofmatchingthereceivingcoilbecomeineffective.Anappropriatedeviationofthematchingcapacitorfortheresonantcoilisrequiredtomaximizethetransferfactorfromthereceivingcoiltothepreamplifier.Theoptimizationdesignoftheresonantcoilisthencarriedoutusingacombinationofthepartialelementequivalentcircuit(PEEC)methodandunitarydesign.ThePEECmethodallowsrapidcalculationoftheACresistance,whiletheuniformdesignmethodfacilitatestheselectionofoptimalcoilstructuresundermultipleconstraintsanddesignobjectives.Finally,anoverlappeddecouplingapproachminimizesthecouplingbetweenindividualcoilswithintheresonantcoilarray,andtheoptimumcenter-to-centerdistancebetweenthecoilsisgiven.Forthesingleresonantcoil,simulationandimagingresultsshowthattheSNRenhancementdecreaseswithdistance.TheoverallSNRremainshigherthanintheabsenceofresonantcoils.Cleartrendsintheimagingresultsfora5.5cmdiameterwaterphantomdemonstratethiseffect,withamaximumSNRenhancementofupto8.4times.Resonantcoilarraysarealsousedinimagingexperimentswithalargewaterphantomof110mmdiameter,andamaximumSNRenhancementof2.7timesisobserved.AlthoughtheSNRenhancementdecreasescomparedtosinglecoils,thearrayprovidesalargerandmoreuniformenhancementregion.Armimagingexperimentsverifytheperformanceofthearrayinhumanimagingbywrappingtheresonantarrayaroundthesubject'sforearm.Afterthearrayisapplied,themaximumSNRisimprovedbyafactorof4.9.TheSNRimprovementisslightlyhigherthanforthelargewaterphantomduetothesmallerdiameteroftheforearm.Theeffectivenessoflocalizedenhancementusingresonantcoilshasbeenconfirmed.Comparedtoconventionalsurfacecoils,theyofferlowercost,awirelessdesignforflexibleplacement,andeliminatetheneedforadditionalRFchannels.ResonantcoilarraysaresuitableforenhancingthelocalSNRindifferenthumanbodyregionsandcanbefreelyconfiguredintoarraysbasedonimagingrequirements.Infuturework,resonantcoilarrayscanbedesignedspecificallyforotherbodyregionstoachieveoptimalenhancementeffects.
作者：孔晓涵 张雅娜 吴嘉敏 贺玉成 徐征 Author：KongXiaohan ZhangYana WuJiamin HeYucheng XuZheng
作者单位：重庆大学电气工程学院重庆400044深圳航天科技创新研究院深圳518057;哈尔滨工业大学机电工程学院哈尔滨150001深圳航天科技创新研究院深圳518057
刊名：电工技术学报 ISTICEIPKU
Journal：TransactionsofChinaElectrotechnicalSociety
年，卷(期)：2024, 39(13)
分类号：TM153
关键词：磁共振成像 射频线圈 低频超材料 信噪比
Keywords：Magneticresonanceimaging radio-frequencycoil low-frequencymetamaterial signal-to-noiseratio
机标分类号：TP391.41V443.5TN958.98
在线出版日期：2024年7月22日
基金项目：国家自然科学基金，深圳科创委承接国家重大科技项目，深圳市科技重大专项基于低频表面超材料的超低场磁共振成像信噪比增强方法[
期刊论文] 电工技术学报--2024, 39(13)孔晓涵 张雅娜 吴嘉敏 贺玉成 徐征超低场磁共振成像(ULF-MRI)设备具有成本低、质量轻、体积小等优点,在特殊领域的应用需求越来越大,如移动磁共振成像救护车、床旁监护、偏远地区等.但由于其磁场强度低,导致信噪比也较低,图像分辨率差,因此提升信噪比对促进...参考文献和引证文献
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关键词：磁共振成像,射频线圈,低频超材料,信噪比,
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