Common Artefacts

Abstract

The causes and remedies of a number of common image artefacts are discussed, including image examples of each. They include those that are a result of the image encoding and reconstruction process image aliasing in the phase encoding direction and image aliasing (or residual fold-over) that occurs with parallel imaging; Motion artefacts including image ghosting due to respiratory motion, image ghosting caused by pulsatile blood flow and flow-related signal loss in the presence of flow jets or turbulence with high velocity gradients; Artefacts related to differences in the resonant frequency of fat and water, including chemical shift artefact in spin echo imaging and in gradient echo imaging; Artefacts that relate to signal de-phasing caused by magnetic susceptibility differences in tissue and metallic artefacts; Artefacts that are caused by both continuous radiofrequency interference and noise spikes. The technique of flow compensation can be used to reduce motion artefacts from flowing blood. In-phase and out-of-phase gradient echo imaging exploits the chemical shift effect in gradient echo imaging.