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Zusammenfassung:
Inhomogeneities of the static magnetic field cause geometric distortions in echo-planar imaging (EPI), which is commonly used for functional neuroimaging (fMRI). Usually, distortion correction is based on static field maps, which increases acquisition time and does not account for dynamic changes. We employed single-shot multi-echo EPI with alternating phase encoding (PE) direction. By comparing the echoes showing opposite distortions, displacement fields could be estimated. Application of the inverse displacement yielded an improved match of the echoes and allowed for weighted averages to increase contrast-to-noise ratio. This methodology is of interest for fMRI at higher fields and real-time applications.
