CORRECTION OF OFF RESONANCE-RELATED DISTORTION IN ECHO-PLANAR IMAGINGUSING EPI-BASED FIELD MAPS

We present, here, a simple method for measurement and correction of of f-resonance related geometric distortion in echo-planar imaging (EPI), This method uses high signal-to-noise ratio (SNR) EPI-based field map s, rapidly acquired using a series of gradient recalled images collect ed across a range of TE values, This field map is distorted in the sam e manner as the EPI images to be unwarped, providing a direct look-up table for the correct location of each pixel of data, This method adds very little scan time and is robust and easy to implement.