Quantitative ultrasound approaches for diagnosis and monitoring hepatic steatosis in nonalcoholic fatty liver disease - PubMed (original) (raw)

Review

. 2020 Mar 4;10(9):4277-4289.

doi: 10.7150/thno.40249. eCollection 2020.

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Review

Quantitative ultrasound approaches for diagnosis and monitoring hepatic steatosis in nonalcoholic fatty liver disease

Amir M Pirmoazen et al. Theranostics. 2020.

Abstract

Nonalcoholic fatty liver disease is a major global health concern with increasing prevalence, associated with obesity and metabolic syndrome. Recently, quantitative ultrasound-based imaging techniques have dramatically improved the ability of ultrasound to detect and quantify hepatic steatosis. These newer ultrasound techniques possess many inherent advantages similar to conventional ultrasound such as universal availability, real-time capability, and relatively low cost along with quantitative rather than a qualitative assessment of liver fat. In addition, quantitative ultrasound-based imaging techniques are less operator dependent than traditional ultrasound. Here we review several different emerging quantitative ultrasound-based approaches used for detection and quantification of hepatic steatosis in patients at risk for nonalcoholic fatty liver disease. We also briefly summarize other clinically available imaging modalities for evaluating hepatic steatosis such as MRI, CT, and serum analysis.

Keywords: hepatic steatosis; nonalcoholic fatty liver disease; nonalcoholic steatohepatitis; noninvasive assessment; quantitative ultrasound.

© The author(s).

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Conflict of interest statement

Competing Interests: Dr. Kamaya receives royalties from Amirsys/ Elsevier, has research agreements with Philips/ Siemens, and is supported by National Institutes of Health grants R01 CA195443, R01 CA215520-01A1, and U01 CA210020-01A1. Dr. El Kaffas is a co-founder at Oncousics Inc., has research agreements with Philips/Siemens, and is supported by National Institutes of Health grants R01 CA211932, R01 CA215520-01A1, and U01 CA210020-01A1. All other authors declare that no competing interest exists.

Figures

Figure 1

Figure 1

Qualitative assessment of liver fat with conventional ultrasound. (A) Schematic showing classic qualitative features of fatty liver - increased echogenicity compared to right kidney, blurring of intrahepatic vessels and posterior beam attenuation. Clinical ultrasound images demonstrating (B) normal, (C) mild, (D) moderate, and (E) severe fatty liver.

Figure 2

Figure 2

Attenuation Coefficient quantitative ultrasound method. Schematic (A) and clinical image (B) of a 55 year old female (BMI 43.5) with fatty liver demonstrating greater ultrasound beam attenuation within the deep aspects of the liver (arrow) and high attenuation coefficient of 0.87 dB/cm/MHz. Schematic (C) and clinical image (D) of 60 year old male (BMI 28.41) with normal liver demonstrating homogenous attenuation throughout the liver with a low attenuation coefficient of 0.49 dB/cm/MHz.

Figure 3

Figure 3

Computerized hepatorenal ratio quantitative ultrasound method. Schematic (A) and clinical image (B) of a 55 year old female (BMI 43.56) with fatty liver demonstrating increased echogenicity of the liver compared to the right kidney with the H/R ratio of 3.59. Schematic (C) and clinical image (D) of a 60 year old female (BMI 28.2) with normal liver demonstrating similar echogenicity of the liver compared to the right kidney with the H/R ratio of 1.01.

Figure 4

Figure 4

Shear wave elastography quantitative ultrasound method with calculated SWE measurements shown as color-coded scale superimposed on grayscale clinical images. (A) 55 year old female patient with NAFLD and MRI calculated fat fraction of 43 % with SWE measurement of 6.15 kPa and (B) a 60 year old male without history of NAFLD and MRI calculated fat fraction of 1.4 % with SWE measurement of 4.55 kPa. These SWE measurements show no significant differences (6.15 vs 4.55 kPa) despite marked variability in MR calculated fat fractions (43 % vs 1.4 %).”

Figure 5

Figure 5

MR methods of hepatic fat assessment. A) MR spectroscopy calculates the hepatic fat fraction by separating out the number of water and fat protons in a small sample volume within the liver, which are demonstrated here as separate spectroscopy peaks. B-D) Chemical shift based MRI fat fraction, which is calculated by assessing signal loss on the Out-of-Phase (C) sequences when compared to In-Phase (B) sequences. D) Proton Density Fat Fraction percentage (PDFF) map is used to accurately calculate fat fraction by drawing ROIs on different areas of the liver as shown here.

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