[Optimization of flip angle for 3D-VIBE technique in liver dynamic MRI].

Abstract

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.

• Authors: Kenichi Naito, Yukio Ohgoshi, Masaki Ohkubo, Yuhko Yagishita, Junko Oka, Ayako Ohta, Satoshi Yamamoto, Emi Komazawa
• Journal: Nihon Hoshasen Gijutsu Gakkai zasshi (Nihon Hoshasen Gijutsu Gakkai Zasshi) Vol. 61 Issue 10 Pg. 1441-6 (Oct 20 2005) ISSN: 0369-4305 [Print] Japan
• PMID: 16270023 (Publication Type: English Abstract, Journal Article)

Topics

• Carcinoma, Hepatocellular (diagnosis)
• Female
• Humans
• Imaging, Three-Dimensional
• Liver (anatomy & histology)
• Liver Neoplasms (diagnosis)
• Magnetic Resonance Imaging (methods)
• Phantoms, Imaging