R2*-mapping delivers quantitative information about tissue microstructure. We investigate the scale of image distortions in high-resolution, bipolar, multi-echo GRE acquisitions at 7T and their effects on R2*-mapping. We study reduction in variance by applying field map-based distortion correction while also considering the confounding effect of local smoothing. We show that for regions with signal displacement > 0.5 voxels the reduction in variance comes largely, not from smoothing, but from the appropriate repositioning of the tissue signal. Therefore, correcting distortions, also in sub-voxel regime, improves data consistency in bipolar GRE acquisitions, facilitating more robust R2*-mapping in high-resolution laminar studies for instance.
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