Magnetic resonance imaging of electric properties in living bodies

New methods for magnetic resonance imaging of electric properties in living bodies have been developed. The method of conductivity imaging was based on the proportionality between the electric conductivity and the diffusion coefficient of water. The conductivity images of the human brain exhibited high anisotropy in conductivity in some regions in the white matter. A distinctive signal inhomogeneity arises in the magnetic resonance images of samples whose dimension is comparable to the wavelength of RF electromagnetic fields. Spatial distributions of the magnitude and phase in cylindrical phantoms were obtained by theoretical calculations and experiments at 4.7 T. As the diameter of the phantom approaches to the wavelength of the electromagnetic fields in the phantom, the magnitude of the signals in the center increases because of the dielectric resonance effect. An increase in conductivity resulted in a suppression of the signal inhomogeneity due to the skin effect. In addition, the increase in conductivity caused a phase delay in the center of the phantom.