"Shimming will help to reduce this artifact by making the magnetic field more homogeneous 4.The term Moiré when used in digital imaging and computer graphics describes an artefact that can be created by overlaying two semi-transparent grids or repeating line patterns on each other, which creates an interference pattern. In general radiography, the term has been used to describe the 'grid moiré pattern' where there is under sampling due to incorrect grid placement or alignment 3."