[An experimental study of the optimal flip angle for hepatocellular magnetic resonance imaging with Gd-EOB-DTPA]

Gadoxetate Sodium (Gd-EOB-DTPA) is a relatively new contrast agent used for liver examination by magnetic resonance (MR) imaging. The setting of the flip angle (FA) is very important to obtain images with high contrast in hepatocellular MR imaging. The aim of this study was to determine the optimal FA for hepatocellular MR imaging. Optimal FA was estimated using a visual evaluation by observers. We made the visual evaluation with a paired comparison test. When the overall characteristic showed a significant difference, we then evaluated the optimal FA using a yardstick analysis. The visual evaluation by observers indicated that the FA was best at 22 degrees for the overall characteristic, the contrast characteristic, and the sharpness characteristic, and for the noise characteristic, the best FA was 18 degrees. All characteristics showed a significant difference between 18 and 22 degrees. Based on our results, the most important factor was the contrast characteristic for the visual evaluation, and we concluded that the optimal FA in hepatocelluar MR imaging was 22 degrees.