Black boundary artifact

Black boundary artifact or india ink artifact is an artificially created black line located at fat-water interfaces such as those between muscle and fat. This results in a sharp delineation of the muscle-fat boundary that is sometimes visually appealing but not an anatomical structure. 

Case 1 is a coronal image through the upper body with an echo time of 7 ms. A black line is seen surrounding the muscles of the shoulder girdle as well as around the liver.

This artifact occurs in gradient echo sequences as a result of selecting an echo time (TE) in which the fat and water spins (located in the same pixel at an interface) are out of phase, cancelling each other. At 1.5 T, the 3.5 PPM difference in frequency between water and saturated fat results in cancellation of spins at 4.5 ms multiples, starting at about 2.3 ms; for example at 6.8 ms, 11.3 ms, and 15.9 ms. This artifact does not occur with spin echo sequence as the spins are rephased by the 180o refocusing gradient.

Remedy

To avoid this artifact:

  • TE's close to 4.5 ms, 9 ms, 13.6 ms, should be chosen
  • fat suppression can be used
  • a SE sequence instead of GE will also eliminate the artifact
MRI physics
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Article Information

rID: 21766
Section: Physics
Synonyms or Alternate Spellings:
  • Boundary effect

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Cases and Figures

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    Case 1: black boundary artifact
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