Quantification of Liver Fat Content with Ultrasound: A WFUMB Position Paper

Abstract

New ultrasound methods that can be used to quantitatively assess liver fat content have recently been developed. These quantitative ultrasound (QUS) methods are based on the analysis of radiofrequency echoes detected by the transducer, allowing calculation of parameters for quantifying the fat in the liver. In this position paper, after a section dedicated to the importance of quantifying liver steatosis in patients with non-alcoholic fatty liver disease and another section dedicated to the assessment of liver fat with magnetic resonance, the current clinical studies performed using QUS are summarized. These new methods include spectral-based techniques and techniques based on envelope statistics. The spectral-based techniques that have been used in clinical studies are those estimating the attenuation coefficient and those estimating the backscatter coefficient. Clinical studies that have used tools based on the envelope statistics of the backscattered ultrasound are those performed by using the acoustic structure quantification or other parameters derived from it, such as the normalized local variance, and that performed by estimating the speed of sound. Experts' opinions are reported.

Non-invasive tests of non-alcoholic fatty liver disease

“…In conventional ultrasound examination, most information of RF is lost, but in QUS, RF data can be used by back scattered US signals and attenuation coefficient (ATT) calculator. [ 19 ] According to this mechanism, techniques based on calculation of the ATT include CAP, attenuation imaging (ATI), and ATT. Among these methods, CAP has been already widely used in clinical practice (see the next section).…”

Diagnostic Modalities of Non-Alcoholic Fatty Liver Disease: From Biochemical Biomarkers to Multi-Omics Non-Invasive Approaches

“…The European Association for the Study of the Liver (EASL), the European Association for the Study of Diabetes (EASD) and the European Association for the Study of Obesity (EASO) released a joint statement strongly recommending ultrasound as first-line imaging for NAFLD, based on high-quality Level 1 evidence [ 3 ]. Ultrasound is also the most frequently used technique when evaluating patients for hepatic steatosis, which is characterised by a hyperechoic appearance, often referred to as a bright liver [ 136 ]. It is reliable when >33% of hepatocytes are steatotic and produces an appearance of diffuse, smooth, tightly packed echo pattern that is quite distinctive of a steatotic liver and is reproducible on ultrasound [ 136 , 137 , 138 ].…”

“…Ultrasound is also the most frequently used technique when evaluating patients for hepatic steatosis, which is characterised by a hyperechoic appearance, often referred to as a bright liver [ 136 ]. It is reliable when >33% of hepatocytes are steatotic and produces an appearance of diffuse, smooth, tightly packed echo pattern that is quite distinctive of a steatotic liver and is reproducible on ultrasound [ 136 , 137 , 138 ].…”

Ultrasound, the handyman serving our whole populations in the post COVID-19 pandemic

“…Similar ranges of scanners size, capabilities and costs are not present for CT or MR. Furthermore, ultrasound has become capable not only to display morphological information, but also functional findings: for instance presence and velocity of blood flow in large vessels with Doppler, tissue stiffness with elastography [7], tissue perfusion with quantification of contrast ultrasound [8] and very recently measurement of tissue ultrasound dispersione/viscosity or quantification of liver fat content [3,[9][10][11] are almost all become potentially available in the same equipment. Beside the extension in terms of life time and types of equipments, the COVID-19 pandemic has made a reality also a larger use of ultrasound in body districts and enviromental settings.…”

“…Ähnliche Unterschiede zwischen den Scannern bezüglich Größe, Leistung und Preis gibt es bei den CT-oder MRT-Geräten nicht. Außerdem ist die Sonografie zwischenzeitlich in der Lage, nicht nur morphologische Informationen, sondern auch funktionelle Befunde darzustellen: Zum Beispiel sind die Bestimmung des Vorhandenseins und der Geschwindigkeit des Blutflusses in großen Gefäßen mittels Doppler, der Gewebesteifigkeit mittels Elastografie [7], der Quantifizierung der Gewebeperfusion im kontrastverstärkten Ultraschall [8] und seit kurzem die Messung der Gewebe-Ultraschalldispersion/-Viskosität oder die Quantifizierung des Leberfettgehalts [3,[9][10][11]fast allesamt mit derselben Ausstattung möglich. Durch die COVID-19-Pandemie wurde neben der Verlängerung der Lebensdauer und der Erweiterung der Geräteausstattungen auch eine breitere Anwendung der Sonografie in den verschiedenen Körperregionen und unterschiedlichen Umfeldern ermöglicht.…”