Recovery of signal void arising from field inhomogeneities in echo planar imaging

摘要

A prescan process is performed in which an EPI pulse sequence acquires a series of pilot images. Each pilot image is acquired with a different slice selection refocusing gradient and a rephasing map is produced which indicates the optimal refocusing gradient to be used for each pixel. The rephasing map is used to determine the optimal refocusing gradient amplitudes to use in a subsequent scan to reduce signal drop out caused by susceptibility gradients.