Radiology, Vol 171, 525-529, Copyright © 1989 by Radiological Society of North America
Variable-flip-angle spin-echo MR imaging of the pelvis: more versatile T2-weighted images
DG Mitchell, S Vinitski, DL Burk Jr, D Levy and MD Rifkin
Department of Radiology, Thomas Jefferson University Hosptial, Philadelphia, PA.
Dependence on T1 contrast can be reduced by changing the excitation flip
angle. The authors compared T2-weighted spin-echo images (with 30 degrees
and 90 degrees flip angles) of the male and female pelvis in 22
individuals. In six women imaged with a 1,000/80 sequence (repetition time
msec/echo time msec), signal difference-to-noise ratios (SD/Ns) were higher
with a 30 degree flip angle than with a 90 degree angle for urine/fat
(mean, 15.2 vs -6.2; P less than .05) and endometrium/myometrium (13.8 vs
9.0, P less than .05). In eight additional examinations, a 1,000/80
sequence with a 30 degree flip angle and two signal averages had less
motion artifact (1.2 vs 2.7, P less than .01) than a 2,000/80 sequence with
a 90 degree angle and one signal average (4.5 minutes each); SD/Ns were
similar. In a third series of experiments, contiguous sections without
cross talk, obtained by interleaving two 1,000/100, 30 degrees-flip-angle
acquisitions, had better contrast than contiguous sections obtained at
2,400/100 with a 90 degree flip angle (10 minutes each), with SD/Ns of
urine/fat of 28.5 versus 16.1 (P less than .01) and SD/Ns of
endometrium/myometrium of 15.5 versus 7.8 (P less than .05). Reducing the
flip angle can improve examination time, contrast, or motion artifact
suppression or eliminate cross talk in T2-weighted spin-echo MR imaging of
the pelvis.
