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MRI artifacts

MRI artifacts are varied and numerous and give you an insight into the physics behind each sequence. Some effect the quality of the MRI exam while others do not affect the diagnostic quality but may be confused with pathology.

When encountering an unfamiliar artefact, it is useful to systematically examine general features of the artefact to try and understand the type of artefact and how to negate it if needed. These features include:

  1. type of sequence (e.g. fast spin echo, or gradient or volumetric acquisition) 
  2. direction of phase and frequency
  3. fat or fluid attenuation
  4. presence of anatomy outside the image field
  5. presence of metallic foreign bodies

The artifacts

Many artefacts have a characteristic appearance and with experience they can be readily identified.

MR hardware and room shielding
MR software
Patient and physiologic motion
Tissue heterogeneity and foreign bodies
Fourier transform and Nyquist sampling therom

Artifacts are caused by a variety of factors that may be patient related such as voluntary and physiologic motion, metallic implants or foreign bodies. Finite sampling or encoding and Fourier transformation may cause aliasing and Gibbs artifact. Characteristics of pulse sequences may cause black boundary, Moire and phase-encoding artifacts. Hardware issues may cause central point and RF overflow artifacts.


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MRI physics

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