405.Fatty Liver Disease (Liver Steatosis)（二）

每天朗读一段医学影像学英语文章

Signs on CT

Hepatic steatosis is detected as diffuse or focal reduction of the liver normal density on noncontrast-enhanced scan. The normal liver density is 8 HU (Hounsfield unit) above that of the spleen (60 HU). Fatty liver density is 10 HU below spleen density on noncontrast-enhanced scan (if the normal spleen is 52 HU, then the fatty liver is <42 HU).

Focal fatty infiltration is seen as a hypodense area with nonspherical margins (metastases usually have round edge). The hypodense area or the mass does not show mass effect over the parenchyma around it and shows change over time (seen in films before the current scan or after few months’ scan). The same criteria are applied to the focal sparring, but the mass will be isodense within a hypodense liver on noncontrast-enhanced scan.

In both focal sparring and focal fatty infiltration, hepatic vessels course within the fatty infiltration or focal sparring undisturbed. In contrast, metastases or other hepatic lesions will be cutting off the hepatic vessels when they reach them.

Fig. 1.2.3 Axial precontrast (a) and postcontrast (b) abdominal CT images show diffuse hepatic steatosis. Notice the density of the liver compared to the spleen in pre- and post-contrast images.

Signs on MRI

Liver steatosis is diagnosed on MRI when the liver intensity drops to >30 % difference on both T1W in-phase and T1W out-of-phase images.

Fig. 1.2.4 Axial T1W in-phase (a) and T1W out-of-phase (b) MRI in a patient with liver steatosis shows drop in the liver signal intensity >44 % in the T1W out-of-phase image (b), diagnostic of hepatic steatosis.

来源：每天朗读一段医学影像学英语文章

圈主

深圳市人民医院放射科副主任医师杨敏洁

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