Impedance magnetic resonance imaging with external AC field added to main static field

This paper addresses the feasibility for visualization of electrical impedance distributions based on magnetic resonance imaging (MRI). By the previously proposed method the electrical impedance distribution was visualized. However obtained images were often associated with artifacts in the directions of phase-encoding and reading-out. In this paper, the authors propose a new method to eliminate the artifacts by triggering the added external AC field, which is parallel to the main static field. By this method, one can visualize electrical properties of living organisms noninvasively and in principle, at an arbitrary frequency. The phantom experiments have been carried out to verify the concept of the shielding effects of induced eddy currents in the subject on spin precession and to figure out methodological details of triggering using an MRI system of 7.05-T with a bore size of 183-mm in diameter.