title: Noninvasive measurement of conductivity anisotropy at larmor frequency using MRI.
abstract: Anisotropic electrical properties can be found in biological tissues such as muscles and nerves. Conductivity tensor is a simplified model to express the effective electrical anisotropic information and depends on the imaging resolution. The determination of the conductivity tensor should be based on Ohm's law. In other words, the measurement of partial information of current density and the electric fields should be made. Since the direct measurements of the electric field and the current density are difficult, we use MRI to measure their partial information such as B1 map; it measures circulating current density and circulating electric field. In this work, the ratio of the two circulating fields, termed circulating admittivity, is proposed as measures of the conductivity anisotropy at Larmor frequency. Given eigenvectors of the conductivity tensor, quantitative measurement of the eigenvalues can be achieved from circulating admittivity for special tissue models. Without eigenvectors, qualitative information of anisotropy still can be acquired from circulating admittivity. The limitation of the circulating admittivity is that at least two components of the magnetic fields should be measured to capture anisotropic information.
authors.affiliation: Department of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Republic of Korea.
authors.forename: Joonsung
authors.initials: J
authors.lastname: Lee
authors.forename: Yizhuang
authors.initials: Y
authors.lastname: Song
authors.forename: Narae
authors.initials: N
authors.lastname: Choi
authors.forename: Sungmin
authors.initials: S
authors.lastname: Cho
authors.forename: Jin Keun
authors.initials: JK
authors.lastname: Seo
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Kim
mesh_terms: D000465:Algorithms; D016880:Anisotropy; D001703:Biophysics / Q000379:methods*; D003198:Computer Simulation; D003952:Diagnostic Imaging / Q000379:methods; D004553:Electric Conductivity; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D012815:Signal Processing, Computer-Assisted
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