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
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