High resolution structural brain imaging at 7T can benefit from motion correction with volumetric navigators. Echo-planar-imaging (EPI) can reduce navigator durations and therefore allow for higher resolution navigators which are tempting to use to increase accuracy of the movement parameters. However, the severe B0 inhomogeneities at 7T lead to geometric distortions that change with head position and therefore lower navigator accuracy. We investigated the navigator accuracy for water and fat navigators of different resolutions and EPI readout durations. We found that the realignment parameter error grows with the amount of motion, voxel size, and EPI readout duration.
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