Conductivity Imaging of Postmortem and In-vivo Canine Brains using MREIT

Magnetic resonance electrical impedance tomography (MREIT) has the potential to provide conductivity images with high spatial resolution and accuracy. Following recent studies using various conductivity phantoms, we performed postmortem and also in vivo animal imaging studies of canine brains. Using imaging currents of 40 and 5 mA in postmortem and in vivo experiments, respectively, we have produced conductivity images of canine brains with a pixel size of 1.406times1.406 mm
²
. Reconstructed conductivity images show clear contrast between white and gray matters in situ. Considering the anisotropic conductivity of white matters, we interpreted reconstructed conductivity images as equivalent isotropic conductivity images. Estimated conductivity ratios of white to gray matters were between 1.13 and 1.20 depending on the choice of a region of interest in reconstructed images. Higher conductivity values of white matters compared with those of gray matters stem from the fact that reconstructed equivalent isotropic conductivity values of white matters reflect higher conductivity of white matters in the longitudinal direction.