Comparative MR study of hepatic fat quantification using single-voxel proton spectroscopy, two-point dixon and three-point IDEAL



Hepatic fat fraction (HFF) was measured in 28 lean/obese humans by single-voxel proton spectroscopy (MRS), a two-point Dixon (2PD), and a three-point iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) method (3PI). For the lean, obese, and total subject groups, the range of HFF measured by MRS was 0.3–3.5% (1.1 ± 1.4%), 0.3–41.5% (11.7 ± 12.1), and 0.3–41.5% (10.1 ± 11.6%), respectively. For the same groups, the HFF measured by 2PD was −6.3–2.2% (−2.0 ± 3.7%), −2.4–42.9% (12.9 ± 13.8%), and −6.3–42.9% (10.5 ± 13.7%), respectively, and for 3PI they were 7.9–12.8% (10.1 ± 2.0%), 11.1–49.3% (22.0 ± 12.2%), and 7.9–49.3% (20.0 ± 11.8%), respectively. The HFF measured by MRS was highly correlated with those measured by 2PD (r = 0.954, P < 0.001) and 3PI (r = 0.973, P < 0.001). With the MRS data as a reference, the percentages of correct differentiation between normal and fatty liver with the MRI methods ranged from 68–93% for 2PD and 64–89% for 3PI. Our study demonstrates that the apparent HFF measured by the MRI methods can significantly vary depending on the choice of water–fat separation methods and sequences. Such variability may limit the clinical application of the MRI methods, particularly when a diagnosis of early fatty liver needs to be performed. Therefore, protocol-specific establishment of cutoffs for liver fat content may be necessary. Magn Reson Med 59:521–527, 2008. © 2008 Wiley-Liss, Inc.