Occipital and cerebellar images in axial EPI scans look squished at the bottom and occipital poles contain large divots in them. Can they be eliminated?
This artifact shows up when the frequency direction is set to L-R. The bad news is that in general fieldmap unwarping can not fix these distortions because it involves image bunching due to overlap of misplaced voxels. The good news is that these distortions can be improved upon by inverting the phase-encode “view order” (i.e. the direction in which the k-space data is acquired) and then applying filedmap unwarping. By default the view order is set to “bottom-up”. This causes voxel bunching at the bottom of axial images (in the region of occipital poles and cerebellum) and image stretching at the top. Switching the view-order to “top-down” before EPI scans would produce images that bunch in the inferior frontal region and stretching in the occipital region. Image stretching (unlike bunching) can be effectively corrected by means of the fieldmap unwarpiign:justify; margin-top:0; margin-bottom:7px’> Scanner troubleshooting I was scanning successfully and after saving a regular series I w
