page_title: MRI artifact
section_title: Motion artifacts
hierarchical_section_title: MRI artifact / Patient-related MR artifacts / Motion artifacts
caption_attribution_description: English: MRI with motion artifacts. For context, see: MRI artifact
context_page_description: An MRI artifact is a visual artifact in magnetic resonance imaging. It is a feature appearing in an image that is not present in the original object. Many different artifacts can occur
  during MRI, some affecting the diagnostic quality, while others may be confused with pathology. Artifacts can be classified as patient-related, signal processing-dependent and hardware-related.
context_section_description: A motion artifact is one of the most common
  artifacts in MR imaging. Motion can cause
  either ghost images or diffuse image
  noise in the phase-encoding direction.
  The reason for mainly affecting data
  sampling in the phase-encoding
  direction is the significant difference
  in the time of acquisition in the frequency-
  and phase-encoding directions.
  Frequency-encoding sampling
  in all the rows of the matrix (128, 256
  or 512) takes place during a single
  echo (milliseconds). Phase-encoded
  sampling takes several seconds, or
  even minutes, owing to the collection
  of all the k-space lines to enable
  Fourier analysis. Major physiological
  movements are of millisecond to seconds
  duration and thus too slow to
  affect frequency-encoded sampling,
  but they have a pronounced effect in
  the phase-encoding direction.
  Periodic movements such as cardiac
  movement and blood vessel or
  CSF pulsation cause ghost images,
  while non-periodic movement causes
  diffuse image noise (Fig. 1). Ghost
  image intensity increases with amplitude
  of movement and the signal
  intensity from the moving tissue.
  Several methods can be used to
  reduce motion artifacts, including
  patient immobilisation, cardiac and
  respiratory gating, signal suppression
  of the tissue causing the artifact,
  choosing the shorter dimension of the
  matrix as the phase-encoding direction,
  view-ordering or phase-reordering
  methods and swapping phase and
  frequency-encoding directions to
  move the artifact out of the field of
  interest.
caption: Fig. 1. Motion artifact (T1 coronal study of cervical vertebrae).[1]
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