Abstract: Objective The study was conducted to investigate the optimal flip angle (FA) for image quality of the biliary system under disodium zocerate (Gd-EOB-DTPA) enhanced magnetic resonance imaging (MRI) in patients with space-occupying lesions (SOL). Methods Sixty patients with SOL were admitted to our hospital between July 2019 and July 2023, and all underwent Gd-EOB-DTPA-enhanced MRI by using a Philips Elition 3.0 scanner with five different sets of FA at 9°, 20°, 30°, 45° and 60°. The bile duct, artifacts, signal-to-noise ratio and contrast-to-noise ratio of the biliary system with different FA were compared. Results At FA=45° and 60°, the estimated scores of cholangiography were (3.4±0.9) and (3.6±1.0), both significantly higher than at 9°, 20° and 30° [(2.7±0.5), (2.9±0.8) and (3.2±0.8), respectively, P<0.05], suggesting with the increase of FA, the score of biliary duct imaging were getting greater and greater, that is, the image quality was getting better and better; as respect to the Objective evaluation of biliary system, the differences of signal-to-noise ratio of gallbladder, common hepatic duct and common bile duct at each FA were statistically significant (P<0.05); at FA=30°, 45° and 60°, the signal-to-noise ratios of gallbladder, left hepatic duct, right hepatic duct, common hepatic duct and common bile duct were significantly higher than those at FA = 9° (P<0.05); the average signal-to-noise ratio of gallbladder, right hepatic duct and common hepatic duct were the best at FA = 45°, while the average signal-to-noise ratio of left hepatic duct and common bile duct was the best at FA = 30°; there were statistically significant differences in the signal-to-noise ratio of gallbladder, common hepatic duct and common bile duct at different FA (P<0.05); at FA=30°, 45° and 60°, the signal-to-noise ratio of gallbladder, left hepatic duct, right hepatic duct, common hepatic duct and common bile duct were significantly higher than that at FA=9° (P < 0.05); in addition, the average contrast signal-to-noise ratio of gallbladder, right hepatic duct, common hepatic duct and common bile duct were the best at FA=45°, while the average contrast signal-to-noise ratio of left hepatic duct was the best at FA=30°. Conclusions In 3T delayed imaging, the optimal FA of GdEOB-DTPA enhanced T1 weighted imaging of the liver and bile duct is 45 °, which could be used as a parameter setting basis for MR biliary imaging to improve the imaging quality.

Key words: Liver space-occupying lesions, Disodium zocerate, Magnetic resonance imaging, Biliary system, Flip angle