Quantitative Hepatic Fat Quantification in Non-alcoholic Fatty Liver Disease Using Ultrasound-Based Techniques: A Review of Literature and Their Diagnostic Performance

Abstract

Non-alcoholic fatty liver disease is a condition that is characterized by the presence of >5% fat in the liver and affects more than one billion people worldwide. If adequate and early precautions are not taken, non-alcoholic fatty liver disease can progress to cirrhosis and death. The current reference standard for detecting hepatic steatosis is a liver biopsy. However, because of the potential morbidity associated with liver biopsies, non-invasive imaging biomarkers have been extensively investigated. Magnetic resonance imaging-based methods have proven accuracy in quantifying liver steatosis; however, these techniques are costly and have limited availability. Ultrasound-based quantitative imaging techniques are increasingly utilized because of their widespread availability, ease of use and relative cost-effectiveness. Several ultrasound-based liver fat quantification techniques have been investigated, including techniques that measure changes in the acoustic properties of the liver caused by the presence of fat. In this review, we focus on quantitative ultrasound approaches and their diagnostic performance in the realm of non-alcoholic fatty liver disease.

Keywords: Attenuation; Backscatter; Controlled-attenuation parameter; Non-alcoholic fatty liver disease; Quantitative; Speed of sound; Ultrasound.

Figure1.

MR-PDFF image with multiple region of interest (ROI) showing 6%, 6.9% and 4.8% fat accumulation (Courtesy of Amirkasra Mojtahed, MD).

Figure2.

Difference between healthy liver and fatty liver. Increased echogenicity and poor beam attenuation are visible in figure on the right.

Figure2.

Difference between healthy liver and fatty liver. Increased echogenicity and poor beam attenuation are visible in figure on the right.

Figure3.

Time-motion(TM) mode, Amplitude(A) mode and shear wave propagation map, respectively. TM and A modes are used to locate ideal liver part for reliable acquisitions. Shear wave propagation image.y-axis is distance from skin, x-axis is time. Slope of the dashed line is shear wave speed(V_s). Median CAP shows 289dB/m, and median stiffness value shows 7.1kPa.

Figure4.

Spagetti plot of mean/median of attenuation values from multiple research groups using controlled attenuation parameter. X axis represents steatosis stage (S1–3). Y axis represents controlled attenuation parameter in dB/m units. Attenuation value increases at higher steatosis stages (Sasso et al. 2010, Myers et al. 2012, Kumar et al. 2013, Wang et al. 2014, Ferraioli et al. 2014, Chan et al. 2014, Shen et al. 2014, Chon et al. 2014, Mi et al. 2014, Karlas et al. 2014, Lupsor-Platon et al. 2015, Shen et al. 2015, Imajo et al. 2016, de Ledinghen et al. 2016, Ahn et al. 2016, Kwok et al. 2016, Andrade et al. 2017, Thiele et al. 2018).