Optimization of scanning parameters for MR elastography at 3.0 T clinical unit: volunteer study.
OBJECTIVE
We sought to optimize scanning parameters for MR elastography at 3.0 T clinical unit.


METHODS
10 volunteers were scanned with various magnetization encoding gradient (MEG) frequencies from 60 to 120 Hz at every 10 Hz, with otherwise fixed parameters (external driver frequency/amplitude = 60 Hz/50 %, 10 mm slice thickness, etc.). Images were qualitatively assessed for the degree of image defects, and also quantitatively for the areas without cross-hatching. After determining optimal MEG frequency, external driver amplitudes of 70 % (vs 50 %) and slice thickness of 8 mm (vs 10 mm) were also tested. With the optimized parameters, scans were repeated 1 week after the initial scan, and the repeatability of the liver stiffness measurement was validated.


RESULTS
80 or 90 Hz was shown to be the best MEG frequency. There were no significant differences in the qualitative and quantitative assessment between the two amplitudes and two slice thicknesses; however, 70 % amplitude resulted in discomfort at the chest wall beneath the external acoustic driver. Thus, MEG 80 (or 90) Hz, amplitude 50 %, and thickness 10 (or 8) mm were considered optimal. Repeatability of the liver stiffness measurement was ±10 % (95 % confidence interval).


CONCLUSIONS
With the optimized parameters, repeatability of ±10 % in liver stiffness measurement was obtained.
Department of Radiology, Faculty of Medicine, Fukuoka University Hospital, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka, 814-0180, Japan, yoshinobushinagawa@yahoo.co.jp.
Yoshinobu
Y
Shinagawa
Toshimichi
T
Mitsufuji
Shoichi
S
Morimoto
Ryuji
R
Nakamuta
Hiroshi
H
Urakawa
Ayako
A
Morita
Ritsuko
R
Fujimitsu
Koichi
K
Takano
Kengo
K
Yoshimitsu
D000328:Adult; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000033:anatomy & histology*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity