Ultrasound-based Classification Of Fatty Liver Disease: A Review

fatty liver ultrasound grading

Liver biopsy is currently the reference standard for disease assessment in NAFLD and NASH. However, it is observer dependent and invasive, and it carries non-negligible risks. Imaging techniques for assessing steatosis range from qualitative tools available at the bedside to highly accurate and precise metrics. Table 4 lists the navigate to these guys strengths, weaknesses, and clinical care recommendations for these techniques. Ultrasound is a safe and widely available technique that may serve in certain clinical scenarios as an initial screen. Its main drawbacks are machine and operator dependencies, qualitative assessment, and inaccuracy at detecting mild steatosis.

Further, QUS cannot simultaneously quantify fat in other organs as can be done with MRI based techniques. Finally, multiple simultaneously emerging QUS techniques from different vendors may prohibit widespread-buy in via and may limit inter-vendor comparisons. Hepatic fat fraction estimated by MRS has proven to be an accurate substitute for liver biopsy and noninvasive imaging standard reference for liver fat quantification 103,104.

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These include controlled attenuation parameter (CAP) measured by transient elastography (TE) device; attenuation (AC) and backscatter coefficients (BSC); computerized calculation of hepatorenal index (HRI); and ultrasound envelope statistic parametric imaging (also known as speckle statistics). Speckle statistics include acoustic structure quantification (ASQ) and Nakagami imaging; QUS spectroscopy; speed of sound (SoS); and shear wave elastography (SWE) metrics such as dispersion and viscosity. Emerging QUS techniques, integrating statistical methods most notably attenuation-based Nakagami imaging and backscatter-derived quantitative ultrasound spectroscopy show promise and could potentially become the noninvasive imaging method of choice in screening, grading, and monitoring NAFLD patients on therapy. These techniques compared to liver biopsy, could be implemented for screening purposes, compared to an ordinal scale, or provide an accurate continuous measurement of liver fat; the latter two would be most useful for the longitudinal follow-up of NAFLD patients to assess treatment response. Limitations of QUS techniques include confounding effects of body habitus and ascites.

Finally, we provide a brief overview of alternative non-ultrasound based imaging techniques, which are clinically available for detection and characterization of hepatic steatosis, particularly in NAFLD. As a non-invasive alternative to liver biopsy, imaging is increasingly utilised in the diagnosis and management of NAFLD. Imaging and related non-imaging techniques can accurately assess the important disease markers of liver steatosis and advanced liver fibrosis.

fatty liver ultrasound grading

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Since commercial variants of PDFF technique may not be available at all sites, trials may be done in partnership with radiology coordinating centres that can standardise the appropriate PDFF technique across all sites participating in a trial. Due to exposure to ionising radiation and low sensitivity for mild steatosis, we would not recommend CT as a primary modality for measuring liver steatosis. If CT is done for other purposes, then we recommend that radiologists assess for steatosis using conservative thresholds. In addition, the widespread availability and quantitative metric of CT make it potentially useful for identifying patients with steatosis in retrospective studies. Other possibilities for improvement include examining the effect of variable operator expertise and acquisition parameters on the accuracy of ultrasound evaluation of steatosis. Development of methods to improve agreement between readers, such as a training atlas, is another area under investigation.

In addition, MRS is limited by small sample volume, which could affect its accuracy in evaluation of patients with uneven fatty liver. Acquiring several MRS scans in different segments of the liver could potentially improve this limitation, but may be time-consuming to perform 105. Furthermore, this technique is limited to centers with MR spectroscopy expertise, which further limits its widespread clinical use. In conclusion, nonalcoholic fatty lowest price liver disease is a major health issue with a worldwide increase in prevalence, paralleling the global obesity epidemic. Accurate noninvasive alternatives to liver biopsy in evaluating and monitoring levels of hepatic steatosis are have evolved significantly in the past decade. Emerging quantitative ultrasound-based approaches, integrating innovative statistical methods are promising new technologies to non-invasively assess hepatic steatosis.

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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. Conventional unenhanced CT and DECT at steatosis adapted from Kramer et al.50 Conventional unenhanced CT acquired at 120 kVp (first row) and DECT acquired by rapidly switching tube voltages between 80 and 140 kVp, then post-processed into fat-density images (second row) are shown for three patients with varying degrees of steatosis. Patients A, B, and C have 0, 10, and 40% liver fat fraction, respectively, as determined by MRS PDFF (not shown). As liver fat fraction increases across the rows, liver attenuation at conventional unenhanced CT visibly decreases and liver fat density on DECT visibly increases. Ultrasound yields relatively imprecise qualitative classifications of mild, moderate, and severe steatosis. Additionally, conventional ultrasound is operator- and reader-dependent, resulting in variable results and reproducibility.

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