Simulation of MREIT using balanced steady state free precession (b-SSFP) pulse sequence

Magnetic resonance electrical impedance tomography (MREIT) utilizes the relation between conductivity and magnetic flux density induced by externally injected current to perform conductivity imaging of body tissues. A spin echo pulse sequence has been predominantly used in MREIT to acquire the z-component Bz of the induced magnetic flux density data from MR phase images. Spin echo based MREIT pulse sequences are most stable and successful in producing high-resolution conductivity images in postmortem and in vivo animal and human experiments. In some applications, localization of a physiological event is desirable. Examples may include detection of neural activities through conductivity changes. In such a case, it would be necessary to maximize the sensitivity. In this paper, we suggest using a balanced steady state free precession (b-SSFP) pulse sequence to localize a small conductivity change. The induced magnetic flux density Bz subject to an injection current makes an off-resonance phase in b-SSFP signals. We expect the high sensitivity of b-SSFP signals to any off-resonance phase change will be advantageous for detecting a small conductivity change. Using computer simulations, we show the feasibility of functional or time-difference MREIT using the b-SSFP pulse sequence.