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Chemical misregistration


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Chemical misregistration

  1. 1. CHEMICAL MISREGISTRATION ARTIFACT<br /><ul><li>This artefact occurs as a ring of dark signal around certain organs where fat and water interfaces occur within the same voxel.
  2. 2. It mainly occurs in the phase direction as it is produced due to the phase difference between the fat an water
  3. 3. It is more pronounced in gradient imaging</li></li></ul><li>CHEMICAL MISREGISTRATION ARTIFACT<br />Chemical misregistration artefact causing overlying shadows in breast images<br />
  4. 4. CAUSE<br /><ul><li>The artefact is caused because their fat and water are in phase and out of phase at others, due to their different recessional frequencies.
  5. 5. As they travel at different speeds around their processional paths they are at various positions on the path but periodically they are at same position and therefore in phase.</li></li></ul><li>REMEDY<br /><ul><li>SELECT A TE THAT MATCHES THE PERIODICITY OF FAT AND WATER
  6. 6. IP misregistrationyour field strength Fro e.g. at 1.5 T this is a multiple of 4.5 ms educes chemical misregistration artefact
  7. 7. Using spin echo sequences rather than gradient echo sequence will reduce this artefact since 1500 RF pulse is very effective in compensating for phase differences.</li>