Conductivity imaging of human lower extremity using MREIT with multi-echo pulse sequence and 3 mA imaging current

We present our recent developments in tissue conductivity imaging of the human lower extremity using MREIT. In performing in vivo human knee and calf imaging experiments, we addressed two technical issues of the chemical shift artifact and measurement noise. Adopting a recently developed chemical shift artifact correction method for MREIT, we could improve the quality of conductivity images of the knee and calf. We found that the correction method is advantageous in terms of the signal-to-noise ratio (SNR) compared with a fat suppression method. Since the knee is more sensitive to injection currents, we limited the current amplitude in knee experiments to 3 mA to avoid painful sensation. Reduction of the current amplitude requests a similar reduction of the noise level in measured magnetic flux density signals since the signal is proportional to the current amplitude. We incorporated a lately developed multi-echo based MREIT pulse sequence to enhance MR signals and prolong the total current injection time, thereby reducing the noise level in measured magnetic flux density signals.