Dual-energy CT in the diagnosis and quantification of fatty liver: limited clinical value in comparison to ultrasound scan and single-energy CT, with special reference to iron overload.

BACKGROUND/AIMS: It has been suggested that dual-energy CT could differentiate irregular fatty liver from other hypodense lesions. We compared dual-energy CT to ultrasound scan and single-energy CT in the diagnosis and quantification of fatty liver, with special reference to iron overload.
METHODS: Twenty-seven patients were included according to ultrasound: fatty liver (n=16) and normal liver (n=11). Single and dual-energy CT were performed. Attenuation measurements of hepatic lobes and control tissues were taken at 140 kV and 80 kV CT-guided liver biopsy was done in fatty liver patients, the degree of infiltration was estimated, and the histologic iron overload determined (iron overload, n=11; iron-free, n=5).
RESULTS: The mean changes in attenuation for the right hepatic lobe were: normal liver: -0.8 (ns); iron overloaded fatty liver: 1.5 (ns); and iron-free fatty liver: 7.7 (p<0.0053). A spleen-liver attenuation differential threshold of 12H (140 kV, single-energy CT) and a right hepatic lobe 140 kV to 80 kV attenuation differential threshold of 9 H (dual-energy CT) were specific for fatty liver. Histology confirmed all cases of fatty liver diagnosed by ultrasound, independently of iron overload. Ultrasound did not differentiate cases of irregular from diffuse fatty liver detected on CT. Iron overload produced a masking effect in CT, decreasing its sensitivity: fatty liver was diagnosed in 67% of cases by single-energy CT and in 20% by dual-energy CT. Degree of fatty infiltration correlated with single-energy CT.
CONCLUSIONS: Ultrasound diagnosed fatty liver best. Single-energy CT quantifies fatty infiltration, and best differentiates the irregular from the diffuse forms. Dual-energy CT is limited by poor sensitivity, especially in iron overload.