Artifact Reduction for Rapid Phase-Based EPT in the Human Brain In Vivo Using a Multi-Echo 2D EPI Sequence

Motivation: To date, phase-based electrical properties tomography (EPT) has been performed using time-consuming (~5-minute) gradient-echo sequences. Goal(s): To calculate EPT conductivity maps from a rapid multi-echo 2D-EPI acquisition (TR~4s), overcoming slice-to-slice phase inconsistencies. Approach: We investigated the effect of four different methods to remove slice-to-slice inconsistencies from the phase offset (φ0) of the multi-echo 2D-EPI data on conductivity maps in a numerical phantom and in vivo. Results: Removing the median φ0 in each slice in the brain provided high quality conductivity maps with clear delineation between grey matter, white matter and CSF. Tissue conductivity values showed good inter- and intra-subject repeatabilityImpact: We developed a rapid, repeatable method for phase-based EPT from multi-echo 2D-EPI, overcoming slice-to-slice phase inconsistencies. This will facilitate clinical applications of EPT, particularly in studies already using multi-echo 2D-EPI for fMRI, and paves the way towards functional EPT.