基于组织电阻抗差异的磁声电检测技术
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摘要
磁声电(MAE)检测是一种基于超声传播和霍尔效应的多物理场耦合新技术,利用磁场中带电粒子超声振动所产生的电势信号来实现生物组织电阻抗差异的测量.本文基于换能器的振动传播和组织电导率分布,推导了导电组织内MAE信号的解析公式,并利用强指向性换能器进行了公式简化.利用三层电导率突变组织模型进行了数值模拟,结果表明检测到的MAE波簇由组织边界产生,其振动幅度和极性反映了超声传播方向上电导率梯度的大小和方向.建立了一个MAE测量实验系统,对多层凝胶组织模型进行了实验测量,所采集的MAE信号和模拟结果高度一致.理论和实验结果证明,所提出的磁声电检测技术能测量组织边界的电导率梯度,反映超声传播路径上的电阻抗差异,为该技术在生物组织电导率的无损检测和成像提供了新方法.
Magneto-acousto-electrical( MAE) measurement is a recently developed technology based on the coupling of ultrasound transmission and Hall Effect with the interaction among the magnetic,acoustic and electrical fields. With the detected MAE signal generated by the acoustic vibration of charged particles in magnetic field,the conductivity difference at conductivity boundaries can be measured. For the acoustic vibration in biological tissues with conductivity variation,the analytical formula of the MAE signal is derived and also simplified for a strong directional transducer. Numerical simulations are conducted for several 3-layer conductive models,and prove that the wave clusters in MAE signal are generated at the conductivity boundary with the amplitude and polarity reflecting the value and the direction of conductivity gradient.With the established the MAE system,experimental measurements are performed for multi-layer gel models and the collected MAE signals agree well with the simulations. The favorable results demonstrate that the conductivity difference along the acoustic transmission path can be detected accurately with the conductivity gradient of the MAE technology,which suggests the application potential in noninvasive electrical impedance detection and biomedical imaging.
Magneto-acousto-electrical( MAE) measurement is a recently developed technology based on the coupling of ultrasound transmission and Hall Effect with the interaction among the magnetic,acoustic and electrical fields. With the detected MAE signal generated by the acoustic vibration of charged particles in magnetic field,the conductivity difference at conductivity boundaries can be measured. For the acoustic vibration in biological tissues with conductivity variation,the analytical formula of the MAE signal is derived and also simplified for a strong directional transducer. Numerical simulations are conducted for several 3-layer conductive models,and prove that the wave clusters in MAE signal are generated at the conductivity boundary with the amplitude and polarity reflecting the value and the direction of conductivity gradient.With the established the MAE system,experimental measurements are performed for multi-layer gel models and the collected MAE signals agree well with the simulations. The favorable results demonstrate that the conductivity difference along the acoustic transmission path can be detected accurately with the conductivity gradient of the MAE technology,which suggests the application potential in noninvasive electrical impedance detection and biomedical imaging.
引文
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[25]TAKEGAMI K,KANEKO Y,WATANABE T,et al.Polyacrylamide gel containing egg white as new model for irradiation experiments using focused ultrasound[J].Ultrasound in medicine and biology,2004,30(10):1 419-1 422.
[26]WANG J,ZHOU Y,SUN X,et al.Acoustic source analysis of magnetoacoustic tomography with magnetic induction for conductivity gradual-varying tissues[J].IEEE transactions on biomedical engineering,2016,63(4):758-764.
[2]SUROWIEC A J,STUCHLY S S,BARR J R,et al.Dielectric properties of breast carcinoma and the surrounding tissues[J].IEEE transactions on biomedical engineering,1988,35(4):257-263.
[3]JOSSINET J.The impedivity of freshly excised human breast tissue[J].Physiological measurement,1998,19(1):61-75.
[4]METHERALL P,BARBER D C,SMALLWOOD R H,et al.Three-dimensional electrical impedance tomography[J].Nature,1996,380(6 574):509-512.
[5]PAULSON K,LIONHEART W,PIDCOCK M.Optimal experiments in electrical impedance tomography[J].IEEE transactions on medical imaging,1993,12(4):681-686.
[6]HARTOV A,LEPIVERT P,SONI N,et al.Using multiple-electrode impedance measurements to monitor cryosurgery[J].Medical physics,2002,29(12):2 806-2 814.
[7]PAULSEN K D,MOSKOWITZ M J,RYAN T P,et al.Initial experience with EIT as a thermal estimator during hyperthermia[J].International journal of hyperthermia(the official journal of European society for hyperthermic oncology North American hyperthermia group),1996,12(5):593-594.
[8]HAN W,SHAH J,BALABAN R S.Hall effect imaging[J].IEEE transactions on biomedical engineering,1998,45(1):119-124.
[9]HAN W.Volumetric Hall effect tomography-a feasibility study[J].Ultrasonic imaging,1999,21(3):186-200.
[10]XU Y,HE B.Magnetoacoustic tomography with magnetic induction(MAT-MI)[J].Physics in medicine and biology,2005,50(21):5 175-5 187.
[11]MA Q,HE B.Magnetoacoustic tomography with magnetic induction:a rigorous theory[J].IEEE transactions on biomedical engineering,2008,55(2):813-816.
[12]MA Q,HE B.Investigation on magnetoacoustic signal generation with magnetic induction and its application to electrical conductivity reconstruction[J].Physics in medicine and biology,2007,52(16):5 085-5 099.
[13]WEN H,BENNETT E,SHAH J,et al.An imaging method using the interaction between ultrasound and magnetic field[J].Proceedings of the IEEE ultrasonics symposium,1997,2(2):1 407-1 410.
[14]HAIDER S,HRBEK A Y.Magneto-acousto-electrical tomography:a potential method for imaging current density and electrical impedance[J].Physiological measurement,2008,29(6):S41-S50.
[15]RENZHIGLOVA E,IVANTSIV V,XU Y.Difference frequency magneto-acousto-electrical tomography(DF-MAET):application of ultrasound-induced radiation force to imaging electrical current density[J].IEEE transactions on ultrasonics ferroelectrics and frequency control,2010,57(11):2 391-2 402.
[16]MONTALIBET A,JOSSINET J,MATIAS A.Scanning electric conductivity gradients with ultrasonically-induced Lorentz force[J].Ultrasonic imaging,2001,23(2):117-132.
[17]TSENG N,ROTH B J.The potential induced in anisotropic tissue by the ultrasonically-induced Lorentz force[J].Medical and biological engineering and computing,2008,46(2):195-197.
[18]福建春.声学原理[M].北京:科学出版社,2012.
[19]AMMARI H,GRASLAND M P,MILLIEN P,et al.A mathematical and numerical framework for ultrasonically-induced Lorentz force electrical impedance tomography[J].Journal de mathématiques pures et appliquées,2014,103(6):1 390-1 409.
[20]GRASLAND M P,DESTREMPES F,MARI J M,et al.Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography[J].Physics in medicine and biology,2015,60(9):3 747-3 757.
[21]KUNYANSKY L.A mathematical model and inversion procedure for magneto-acousto-electric tomography[J].Inverse problems,2011,28(3):35 002-35 022.
[22]SU H,GUO G M Q,TU J,et al.Noninvasive treatment efficacy monitoring and dose control for high-intensity focused ultrasound therapy using relative electrical impedance variation[J].Chinese physics B,2017,26(5):054302.
[23]LI Y,GUO G,MA Q,et al.Deep-level stereoscopic multiple traps of acoustic vortices[J].Journal of applied physics,2017,121(16):164 901.(下转第49页)
[24]ZHOU Y,WANG J,SUN X,et al.Transducer selection and application in magnetoacoustic tomography with magnetic induction[J].Journal of applied physics,2016,119(9):094903.
[25]TAKEGAMI K,KANEKO Y,WATANABE T,et al.Polyacrylamide gel containing egg white as new model for irradiation experiments using focused ultrasound[J].Ultrasound in medicine and biology,2004,30(10):1 419-1 422.
[26]WANG J,ZHOU Y,SUN X,et al.Acoustic source analysis of magnetoacoustic tomography with magnetic induction for conductivity gradual-varying tissues[J].IEEE transactions on biomedical engineering,2016,63(4):758-764.