Quantitative assessment of liver steatosis using ultrasound: dual-energy CT

Reflecting the growing interest in early diagnosis of non-alcoholic fatty liver disease in recent years, the development of noninvasive and reliable fat quantification methods is needed. Dual-energy computed tomography (DE-CT) is a quantitative diagnostic imaging method that estimates the composition of the imaging target using a material decomposition technique based on the X-ray absorption characteristics peculiar to substances from DE-CT scanning using X-rays generated with different energies (tube voltage). In this review article, we first explain the basic principles and technical aspects of DE-CT. Then, we will present the current diagnostic ability of DE-CT and the factors influencing the quantitative evaluation of liver steatosis using DE-CT as compared to multi-modal methods including ultrasound and magnetic resonance imaging-based methods. In brief, DE-CT may have comparable diagnostic performance to the modern US-based liver fat measurement methods. However, the current material decomposition technique using DE-CT does not seem to have added value to the simple quantitative assessment of liver steatosis, because DE-CT measurement does not improve the accuracy of fat quantification over conventional single-energy computed tomography (SE-CT) attenuation. The most significant influencing factor for the quantitative assessment of liver steatosis using DE-CT can be hepatic iron deposition. An iron-specific multi-material decomposition algorithm correcting for the influences of iron in the liver has been under development. The current material decomposition algorithm can still have added value in a specific situation such as the quantitative assessment of liver steatosis using contrast-enhanced DE-CT. However, there is a lack of evidence for the influence of liver fibrosis in the quantitative assessment of liver steatosis using DE-CT.