Cross-excitation artifact (MRI)

Cross-excitation artifact is a type of MRI artifact and refers to the loss of signal within a slice due to pre-excitation from RF pulse meant for an adjacent slice.

The frequency profile of the RF pulse is imperfect; this means that during slice selection there is some degree of excitation of the adjacent slices as well. If that adjacent slice is imaged during the same TR (i.e., multi-slice imaging) or soon after (i.e., imaging without leaving a gap), it will be partially saturated, to begin with, and the resulting signal will be reduced. This phenomenon is more conspicuous in inversion recovery (180°) sequences.

Remedy

• leaving a minimum gap of 1/3 slice thickness when imaging contiguous slices
• interleaving between slices
• employing 3D imaging if volume imaging is required
• using optimized pulse sequences that have a time penalty of a higher minimum TE and reduced number of slices for a given TR

See also

• cross-talk artifact
  • similar in causation but it is due to angled images, e.g. lumbar spine imaging