Magnetic resonance imaging (MRI) allows accurate measurement of the extent and severity of hepatic steatosis in patients with nonalcoholic fatty liver disease (NAFLD), demonstrate the results of two studies published in Radiology.
The first study, by Musturay Karcaaltincaba (Hacettepe University, Ankara, Turkey) and colleagues, showed that steatosis could be calculated from the protein density fat fraction (PDFF) of three-dimensional, whole-liver imaging taken in a single breath.
In all, 70 NAFLD patients, aged an average of 44.7 years, underwent volumetric multi-echo gradient-echo imaging a median of 14.5 days of liver biopsy, and the results were compared.
Analysis showed a significant and close correlation on the quantification of hepatic steatosis between PDFF results and liver biopsy, although the relationship was stronger for patients with mild disease than for those with moderate or severe steatosis.
Nevertheless, using a PDFF cutoff of 15.03%, the researchers were able to discriminate between the presence of no or mild steatosis and moderate or severe disease with 93% sensitivity and 85% specificity, and an area under the curve (AUC) of 0.95.
The technique underestimated steatosis in patients with fibrosis compared with those without, but the AUC did not significantly differ, at 0.86 versus 0.97.
Furthermore, the PDFF value did not significantly differ between different segments of the liver. "This result suggested that PDFF measurement can assess the presence and severity of hepatic steatosis in all liver segments," Karcaaltincaba et al say.
Findings by Claude Sirlin (University of San Diego, California, USA) and colleagues also support the use of MRI to assess hepatic steatosis in patients with NAFLD, using PDFF with a magnitude-based chemical shift imaging.
Results for 77 patients, the majority (84%) of whom were children, indicate that PDFF results significantly correlated with histologic steatosis grade, regardless of age or gender, or the presence of lobular inflammation, fibrosis, hepatocellular ballooning, or nonalcoholic steatohepatitis.
Their study gave an AUC value of 0.99 for discriminating between patients with steatosis grade 0 and grade 1 or higher disease, 0.83 for distinguishing between grade 1 or below versus grade 2 or above, and 0.89 for between grade 2 or below versus grade 3 steatosis.
"These findings suggested that MR imaging–PDFF may be useful for noninvasive grading of steatosis," write Sirlin et al.
Nevertheless, they caution that "larger studies that use alternative cohorts are needed to confirm MR imaging-PDFF as an alternative to biopsy for grading hepatic steatosis in clinical care and clinical trials."
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