Extended Data Fig. 4: Gradient coil performance and distortions in EPI.
From: Next-generation MRI scanner designed for ultra-high-resolution human brain imaging at 7 Tesla
Measures of distortion in high-resolution EPI using two different gradient coil performances. Distortion is measured as the level of non-linear warping required to bring two images with opposite phase encode (showing equal but opposite levels of distortion) into alignment. The distortion is expressed as a warp field map, showing the amount of distortion in mm experienced at each voxel, with the sign of the map value showing the direction of distortion along an image axis. Values near zero show little distortion, with more positive or negative values indicating greater distortion.
