Liver MRI at 3 T using a respiratory-triggered time-efficient 3D T2-weighted technique: impact on artifacts and image quality.

摘要

OBJECTIVE: The purpose of this retrospective study was to qualitatively and quantitatively compare image quality of a time-efficient 3D T2-weighted sequence-the sampling perfection with application-optimized contrasts using different flip angle evolutions (SPACE) sequence-with a standard 2D T2-weighted turbo spin-echo (TSE) sequence for liver imaging at 3 T. MATERIALS AND METHODS: Twenty patients underwent liver MRI at 3 T using T2-weighted breath-hold 2D TSE and respiratory-triggered SPACE sequences. Two radiologists independently assessed image quality for both sequences during separate sessions, followed by a side-by-side comparison. One reader performed a quantitative analysis of the estimated signal-to-noise ratio (SNR) and the relative contrast between the liver and other tissues. RESULTS: Image quality scores for the SPACE sequence were significantly better than those for the 2D TSE sequence for motion (p < 0.0001) and pulsation (p < 0.0001) artifact, flow signal suppression (p = 0.0015), sharpness of intrahepatic vessels (p < 0.0001), and sharpness of liver edge (p = 0.0015), with motion and pulsation artifacts being nearly eliminated using the SPACE sequence. However, the scores for B(1) inhomogeneity artifact were significantly worse for the SPACE sequence (p = 0.0117). Overall, both readers preferred SPACE sequence, although this difference was significant for only one reader (p = 0.025, p = 0.275). There was no significant difference between the sequences for estimated liver SNR (p = 0.1564), but the SPACE sequence showed significantly higher relative contrast between the liver and the kidney (p < 0.0001), gallbladder (p = 0.0476), and spleen (p < 0.0001). Relative contrast between the liver and parenchymal lesions was higher with the SPACE sequence than with the TSE sequence, although this difference was not statistically significant (p = 0.125). CONCLUSION: For T2-weighted liver imaging at 3 T, the respiratory-triggered SPACE sequence shows better image quality with near elimination of motion and pulsation artifacts and improved tissue contrast than the breath-hold 2D TSE sequence, but suffers from increased B(1) inhomogeneity artifact and longer scanning time.