Optimization of Echo Time in Direct Detection of Neuronal Currents with MRI

Introduction Various experiments have been performed to use MRI to directly detect magnetic fields produced by neuronal currents (termed ncMRI). However, feasibility of ncMRI has not been completely demonstrated due to limited sensitivity of MRI to neuronal currents. To increase the possibility of detecting ncMRI signal, it is necessary to improve the detection method to achieve higher detection sensitivity, and one improvement is to optimize choice of echo time (TE). The purpose of this study was to estimate the optimal TE for ncMRI experiments using gradient echo EPI pulse sequence. In this work, by modeling the contrast-to-noise ratio (CNR) of ncMRI signal, we obtained the optimal TEs for detecting ncMRI magnitude and phase signals in-vivo. These results will assist in future ncMRI experiments for selecting the optimal TE to achieve the best detection sensitivity.