Imaging artifacts are routinely encountered in MR clinical practice. Therefore the presentation focuses on 1) the understanding why MR artifacts arise, 2) the identification of key artifacts and to understand their origins, 3) the elimination or mitigation of artifacts (if desired or possible), and 4) artifacts that can be utilized for diagnostic purposes.
In MR clinical practice, imaging artifacts are routinely encountered. Artifacts are defined as features of the MR image that are not present in the object being imaged. They appear if effects influence the spatial encoding of the MR signal. Such effects can be of physiological or physical nature. Some artifacts are encountered daily, while others are seen under special conditions.
The origin of artifacts are first discussed in general, than in somewhat more detail for the presented artifacts. In any case all of them are related to the MR signal acquisition or the image reconstruction process. After identifying the artifact, the question will be addressed how the artifact can be eliminated or minimized (if desired or possible), or how the artifact can be utilized for clinical benefit.
It is not possible to comprehensively discuss every artifact that can be clinically encountered. The focus instead will lie on representative artifacts that are either particularly common clinically, or are instructive such that understanding them provides insight into the MRI itself. Representative artifacts that are likely to be covered include artifacts from aliasing, motion and pulsation, chemical shift, Gibbs ringing, magnetic susceptibility effects, parallel imaging, B0 and B1 inhomogeneities, and artifacts accounted to hardware issues.
Artifacts in general:
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Artifacts in body imaging:
3. Huang SY et al. Body MR Imaging: Artifacts, k-Space, and Solutions. Radiographics 2015;35:1439-60. 4. Graves M et al. Body MRI Artifacts in Clinical Practice: A Physicist’s and Radiologist’s Perspective. J Magn Reson Imaging 2013;38:269–287.
Artifacts in neuro imaging:
5. Viallon M et al. State-of-the-art MRI techniques in neuroradiology: principles, pitfalls, and clinical applications. Neuroradiology 2015;57:441-67.
Artifacts in image reconstruction:
6. Tsao J et al. MR Image Reconstruction, in Bammer R (Editor), MR and CT Perfusion Imaging, Williams and Wilkins, 2016.
Artifacts in parallel imaging:
7. Deshmane A et al. Parallel MR Imaging. J Magn Reson Imaging 2012;36:55-72.