Susceptibility artifact

The magnetic field distortions created by susceptibility effects result in variations in precessional frequency across the patient and even within individual voxels. These frequency changes, in turn, produce signal loss from T2*-dephasing and spatial mismapping of the MR signal. The MR imaging characteristics reflect both of these physical mechanisms: geometric distortion with focal areas of signal void and regions of very bright signal resulting from “piling up” signal assigned to the wrong areas.