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QUESTIONS
» Image Artefacts

These questions are concerned with MRI image features which do not represent the object in the field-of-view.

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Reducing Chemical Shift Artefact

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How is chemical shift artefact reduced?

  • Fat suppression techniques. E.g. STIR / SPIR (frequency selective fat suppression).
  • Increase bandwidth (but SNR decreases). This reduces the size of the artefact. Increasing the magnitude of the read-out gradient is equivalent.
  • Swap the frequency-encode and phase-encoding directions. This will not eliminate the chemical shift artefact but will rotate it to another anatomical area. This may also cause phase wraparound or flow-related artefacts to be shifted over the region of interest too.
  • (Lower the external magnetic field strength....this is not a realistic option!)

Further reading on this topic:
Books: 1 p89, 2 p177-181, 3 p123-127
Online: Basics of MRI, MRItutor, St Paul's, Chickscope

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