[Optimization of flip angle for 3D-VIBE technique in liver dynamic MRI].
The aim of this study was to determine a moderate flip angle (FA) for dynamic liver MR imaging (MRI) with the three-dimensional volumetric interpolated breath-hold examination (3D-VIBE) technique. Images of phantoms with various T(1) values (44-560 msec) were acquired with the 3D-VIBE sequence (TR/TE=5.2/2.6 msec) using different FA (5-50 degree). We estimated signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), considered to indicate tumor-to-liver contrast, as a function of FA. In phantoms, in which T(1) values (44-191 msec) were assumed to be shortened by the effect of Gd-DTPA in hepatocellular carcinoma (HCC), the highest SNR in each phantom was observed at FA ranging from 15 to 30 degrees. SNRs in other phantoms, in which T(1) values (298-560 msec) were assumed to be normal liver-tissue pre- or post-enhancement, were high with FA of 10-12 degrees, and were remarkably decreased with FA of more than 30 degrees. CNR increased as FA increased in every phantom, especially in the phantom with shortened T(1) values (44-191 msec), suggesting that enlarging FA improved the tumor-to-liver contrast. Taking both results of SNR and CNR into account, we concluded that a moderate FA was approximately 25 degrees. The advantage with an FA of 25 degrees was confirmed in a clinical study of a patient with hypervascular HCC, in which we could observe coronal enhancement surrounding the lesion in the late phase of the double arterial phase by dynamic MRI using the 3D-VIBE technique.
Naito
Kenichi
K
Department of Radiology, Niigata University Medical and Dental Hospital.
Ohgoshi
Yukio
Y
Ohkubo
Masaki
M
Yagishita
Yuhko
Y
Oka
Junko
J
Ohta
Ayako
A
Yamamoto
Satoshi
S
Komazawa
Emi
E
D006528:Carcinoma, Hepatocellular / Q000175:diagnosis; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008099:Liver / Q000033:anatomy & histology*; D008113:Liver Neoplasms / Q000175:diagnosis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging