Non-invasive imaging techniques in assessing non-alcoholic fatty liver disease: a current status of available methods

Abstract

Non-alcoholic fatty liver disease (NAFLD) is an ailment affecting and increasing a number of people worldwide diagnosed via non-invasive imaging techniques, at a time when a minimum harm caused by medical procedures is rightfully emphasized, more sought after, than ever before. Liver steatosis should not be taken lightly even if its evolution is largely benign as it has the potential to develop into non-alcoholic steatohepatitis (NASH) or even more concerning, hepatic cirrhosis, and hepatocellular carcinoma (HCC). Traditionally, liver biopsy has been the standard for diagnosing this particular liver disease, but nowadays, a consistent number of imagistic methods are available for diagnosing hepatosteatosis and choosing the one appropriate to the clinical context is the key. Although different in sensitivity and specificity when it comes to determining the hepatic fat fraction (FF), these imaging techniques possessing a diverse availability, operating difficulty, cost, and reproducibility are invaluable to any modern physician. Ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), elastography, and spectroscopy will be discussed in order to lay out the advantages and disadvantages of their diagnostic potential and application. Although imagistics has given physicians a valuable insight into the means of managing NAFLD, the current methods are far from perfect, but given the time, they will surely be improved and the use of liver biopsy will be completely removed.

Keywords: hepatosteatosis; non-alcoholic fatty liver disease; non-invasive imaging techniques.

Fig. 1

B-mode ultrasound showing hyperechoic liver comparing with the kidney parenchyma and posterior attenuation of the deep liver parenchyma in the context of hepatic steatosis

Fig. 2

Quantitative (mean hue histogram = 115) and qualitative (soft appearance of the liver parenchyma) real-time elastography revealing hepatic steatosis

Fig. 3

16 slices-unenhanced CT, which depicts lower attenuation values of liver tissue comparing with spleen

Fig. 4

Liver steatosis semi-quantitative assessment with Siemens 16-slices-unenhanced CT with the region of interest (ROI) placement in the liver and spleen parenchyma

Fig. 5

3T MRI, multi-echo DIXON-All breath hold sequences consisting in T1-weighted sequence, in-phase T1 weighted sequence, out-of-phase T1 weighted sequence and fat specific sequence qualitatively assessing liver steatosis

Fig. 6

3T single voxel MR spectroscopy quantitatively evaluating liver steatosis with a manually calculated fat-fraction of 42,21% representing moderate steatosis