Quantifying non-alcoholic fatty liver: liver-spleen CT ratio and fat concentration in dual-energy spectral CT : Accuracy comparison with proton density fat fraction MRI.

OBJECTIVES

This study compared the accuracy of liver-spleen (LS) CT ratio and fat concentration (FC) from unenhanced spectral CT for quantifying non-alcoholic fatty liver (NAFL) against proton density fat fraction (PDFF) from magnetic resonance (MR) multi-echo (ME) Dixon.

METHODS

In this prospective study, 80 participants underwent same-day MR ME Dixon and unenhanced spectral CT, divided into normal and fatty liver groups according to PDFF. We measured FC and LS CT ratio on lipid-based material decomposition images and 70-keV images from unenhanced spectral CT, respectively. The correlations between MR and CT results were analyzed. The diagnostic efficacy of FC from unenhanced spectral CT for differentiating between normal and fatty liver was tested by ROC curve analysis.

RESULTS

As PDFF increased, FC increased and the LS CT ratio decreased. There were statistically significant differences in FC among the normal, mild fatty liver, moderate fatty liver, and severe fatty liver groups (P < 0.05), while there was no statistically significant difference in LS CT ratio between the normal and mild fatty liver groups (P > 0.05). Results of ROC curve analysis showed that with an FC cut-off of 351.19 mg/mL, the sensitivity, specificity, and area under the curve were 95%, 100%, and 0.990, respectively, in differentiating the normal and fatty liver group.

CONCLUSION

Fat concentration from unenhanced spectral CT shows excellent correlation with PDFF from MR ME Dixon, which outperforms the LS CT ratio. It also offers high accuracy in differentiating normal from fatty livers in patients with NAFL.