Aliasing artifacts

Case contributed by Prashant Mudgal

The part of the body that lies beyond the edge of the FOV is projected on to the other side of the image. 

Case Discussion

Aliasing artifacts occur in the phase encoding direction when the dimensions of the imaged object exceeds the field of view. Signal generated from outside the field of view appears as a superimposed object at the opposite edge of the image. Increasing the field of view, changing the gradient axes relative to the patient, or use of surface coils can reduce aliasing and are parameters which are controlled by the radiologist/technologist. The manufacturer may provide software packages which exploit two additional strategies, either limiting the volume of the patient from which the MR signal is acquired as in Inner Volume Imaging or display of resolution unless the number of phase encoding steps is increased at a cost of increased acquisition time. The radiologist may in some clinical situations choose to tolerate aliasing in favor of improved resolution in the area of interest and decreased acquisition time.

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