This post explains how to unfold the undersampled, aliased image to the indices in the reconstruction matrix in SENSE.
In short I sketched how to place the mapping window for acceleration factors 2, 3 and 4. You can see the wrap-around of aliasing windows in the even acceleration factors.
Explanation of mapping wrapped pixels. SENSE SENSE (SENSitivity Encoding) is an image-domain parallel imaging technique in MRI. For more information, you can visit the following links: