MR-IMAGING ARTIFACTS THAT SIMULATE DISEASE - HOW TO RECOGNIZE AND ELIMINATE THEM

Occasionally, artifacts may simulate pathologic conditions on magnetic resonance (MR) images, Motion artifacts especially affect images of t he chest and abdomen, There are a number of techniques for reducing mo tion artifacts, including respiratory and cardiac gating, k-space phas e reordering, gradient moment nulling, even echo rephasing, and physic al restraints, Aliasing occurs when the field of view does not include all of the anatomic structures present in the imaged section, Aliasin g artifacts can be eliminated by increasing the field of view, oversam pling, and use of saturation pulses or surface coils, Truncation artif acts represent the difference between the original and the reconstruct ed image and can be reduced with data extrapolation algorithms or imag e filtering, Chemical shift artifacts and magnetic susceptibility arti facts are due to a local deformity of the magnetic field, resulting in spatial misregistration, Chemical shift artifacts are more severe in images acquired with a narrow-bandwidth technique; magnetic susceptibi lity artifacts are more severe in images acquired with a long echo tim e, Pitfalls in the interpretation of MR images can be avoided by becom ing familiar with the appearances and causes of common MR imaging arti facts.