Synopsis

Keywords: Image acquisition: Artefacts, Contrast mechanisms: fMRI, Neuro: Brain

EPI is sensitive to inhomogeneities in the static magnetic field that arise from the interfaces between tissues with different magnetic susceptibilities. Field inhomogeneities cause geometric distortions in EPI in the phase-encoding direction leading to mislocalization of activation and difficulty coregistering functional results to anatomical scans. We will learn how to correct distortions using a field map calculated from the phase change between images acquired at different echo times. A single field map does not capture dynamic field changes occurring due to motion or respiration. We will thus also expand our capabilities to perform dynamic distortion correction.