Quantification of liver fat with respiratory‐gated quantitative chemical shift encoded MRI

Purpose To evaluate free‐breathing chemical shift‐encoded (CSE) magnetic resonance imaging (MRI) for quantification of hepatic proton density fat‐fraction (PDFF). A secondary purpose was to evaluate hepatic R2* values measured using free‐breathing quantitative CSE‐MRI. Materials and Methods Fifty patients (mean age, 56 years) were prospectively recruited and underwent the following four acquisitions to measure PDFF and R2*; 1) conventional breath‐hold CSE‐MRI (BH‐CSE); 2) respiratory‐gated CSE‐MRI using respiratory bellows (BL‐CSE); 3) respiratory‐gated CSE‐MRI using navigator echoes (NV‐CSE); and 4) single voxel MR spectroscopy (MRS) as the reference standard for PDFF. Image quality was evaluated by two radiologists. MRI‐PDFF measured from the three CSE‐MRI methods were compared with MRS‐PDFF using linear regression. The PDFF and R2* values were compared using two one‐sided t ‐test to evaluate statistical equivalence. Results There was no significant difference in the image quality scores among the three CSE‐MRI methods for either PDFF ( P  = 1.000) or R2* maps ( P  = 0.359–1.000). Correlation coefficients (95% confidence interval [CI]) for the PDFF comparisons were 0.98 (0.96–0.99) for BH‐, 0.99 (0.97–0.99) for BL‐, and 0.99 (0.98–0.99) for NV‐CSE. The statistical equivalence test revealed that the mean difference in PDFF and R2* between any two of the three CSE‐MRI methods was less than ±1 percentage point (pp) and ±5 s −1 , respectively ( P  < 0.046). Conclusion Respiratory‐gated CSE‐MRI with respiratory bellows or navigator echo are feasible methods to quantify liver PDFF and R2* and are as valid as the standard breath‐hold technique. J. Magn. Reson. Imaging 2015;42:1241–1248.