Reduction of magnetic field inhomogeneity artifacts in echo planar imaging with SENSE and GESEPI at high field

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Abstract
Geometric distortion, signal-loss, and image-blurring artifacts in echo planar imaging (EPI) are caused by frequency shifts and T relaxation distortion of the MR signal along the k-space trajectory due to magnetic field inhomogeneities. The EPI geometric-distortion artifact associated with frequency shift can be reduced with parallel imaging techniques such as SENSE, while the signal-loss and blurring artifacts remain. The gradient-echo slice excitation profile imaging (GESEPI) method has been shown to be successful in restoring tissue T relaxation characteristics and is therefore effective in reducing signal-loss and image-blurring artifacts at a cost of increased acquisition time. The SENSE and GESEPI methods are complementary in artifact reduction. Combining these two techniques produces a method capable of reducing all three types of EPI artifacts while maintaining rapid acquisition time. Magn Reson Med 52:1418–1423, 2004.