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

Abstract

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.