Current Density Imaging Using Directly Measured Harmonic B z Data in MREIT

Magnetic resonance electrical impedance tomography (MREIT) measures magnetic flux density signals through the use of a magnetic resonance imaging (MRI) in order to visualize the internal conductivity and/or current density. Understanding the reconstruction procedure for the internal current density, we directly measure the second derivative of B z data from the measured k-space data, from which we can avoid a tedious phase unwrapping to obtain the phase signal of B z. We determine optimal weighting factors to combine the derivatives of magnetic flux density data, ∇2 B z, measured using the multi-echo train. The proposed method reconstructs the internal current density using the relationships between the induced internal current and the measured ∇2 B z data. Results from a phantom experiment demonstrate that the proposed method reduces the scanning time and provides the internal current density, while suppressing the background field inhomogeneity. To implement the real experiment, we use a phantom with a saline solution including a balloon, which excludes other artifacts by any concentration gradient in the phantom.