| In Magnetic Resonance Electrical Impedance Tomography (MREIT), electrical currents are injected into an object, and the resulting magnetic flux density distribution measured using MRI. These measurements are then used to reconstruct the conductivity distribution within the object. This study investigates the theory and experimental implementation of this modality into the UCI 4T MRI system, and presents several improvements to the methodology. Sub-milliamp alternating current with a primary frequency component of 100Hz is utilized, along with a specialized pulse sequence to measure the resulting magnetic flux density distribution. For reconstruction, the Sensitivity Matrix Method is modified to incorporate Tikhonov regularization and iteration to improve the results. These data acquisition and reconstruction techniques are used to reconstruct the 2D conductivity distributions of various agarose gel phantoms. A thickness correction for 2D reconstruction is implemented. Correction algorithms for misaligned electrodes are tested. The variability of current injection profiles is investigated. Finally, the ability of MREIT to monitor changes in conductivity over time is verified through quantitative measurement of ion diffusion. |
