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

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.