American Journal of Roentgenology, Vol 163, 335-337, Copyright © 1994 by American Roentgen Ray Society
MR imaging of the liver at 1.5 T: value of signal averaging in suppressing motion artifacts
GS Gazelle, S Saini, PF Hahn, MA Goldberg and EF Halpern
Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston 02114.
OBJECTIVE. Prior reports have suggested that signal averaging is not as
effective as phase reordering for suppressing motion-related artifacts on
T1-weighted spin-echo MR imaging of the liver at high field strengths. We
hypothesized that with shorter TEs, signal averaging could be effective,
and therefore undertook this study to compare signal averaging with phase
reordering at 1.5T. SUBJECTS AND METHODS. Thirty consecutive patients
underwent MR imaging of the liver at 1.5 T with two T1-weighted spin-echo
pulse sequences. In one sequence we used signal averaging and in the other
we used phase reordering as the primary motion suppression techniques. For
each patient, the order in which these sequences were performed was
randomized; TR (400-500 msec), TE (11-12 msec), and field of view (32-34
cm) remained constant. Images were analyzed quantitatively for liver
signal-to-noise ratio (SNR), liver-spleen contrast-to-noise ratio (CNR),
and liver-lesion CNR (in 16 patients with focal liver lesions), as well as
qualitatively (three observers, blinded to technique) for overall image
quality. RESULTS. Signal averaging resulted in images with significantly
greater liver SNR, liver-spleen CNR, and liver-lesion CNR than did phase
reordering (p = .0001, .002, and .02, respectively). All observers showed a
preference for the signal-averaged images. For one observer, this
preference was statistically significant; for the others, it was not.
CONCLUSION. Signal averaging can be an effective means of suppressing
motion-related artifacts on T1-weighted MR images of the liver obtained at
1.5 T.
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