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World J Gastroenterol. Oct 28, 2019; 25(40): 6053-6062
Published online Oct 28, 2019. doi: 10.3748/wjg.v25.i40.6053
Ultrasound-based techniques for the diagnosis of liver steatosis
Giovanna Ferraioli, Livia Beatriz Soares Monteiro
Giovanna Ferraioli, Dipartimento di Scienze Clinico-Chirurgiche, Diagnostiche e Pediatriche, Medical School University of Pavia, Pavia 27100, Italy
Giovanna Ferraioli, Clinical Sciences and Infectious Diseases Department, Fondazione IRCCS Policlinico S. Matteo, Pavia 27100, Italy
Livia Beatriz Soares Monteiro, Centro Universitário Barão de Mauá, Ramos de Azevedo, São Paulo 14090-180, Brazil
Author contributions: Ferraioli G designed the review outline; Ferraioli G and Soares Monteiro LB performed the literature research; Ferraioli G and Soares Monteiro LB extracted the data from the literature search; Ferraioli G wrote the paper. Both authors approved the final version of the manuscript.
Conflict-of-interest statement: All the Authors have no conflict of interest related to the manuscript.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Giovanna Ferraioli, MD, Academic Research, Doctor, Clinical Sciences and Infectious Diseases Department, Fondazione IRCCS Policlinico S. Matteo, University of Pavia, Viale Camillo Golgi 19, Pavia 27100, Italy. giovanna.ferraioli@unipv.it
Telephone: +39-382-501753
Received: August 27, 2019
Peer-review started: August 27, 2019
First decision: September 19, 2019
Revised: September 27, 2019
Accepted: October 17, 2019
Article in press: October 17, 2019
Published online: October 28, 2019
Processing time: 61 Days and 19.1 Hours
Abstract

Non-alcoholic fatty liver disease (NAFLD) is the leading cause of diffuse liver disease. An accurate estimate of the fat in the liver is important in the diagnostic work-up of patients with NAFLD because the degree of liver steatosis is linked to the metabolic syndrome and the cardiovascular risk. Ultrasound (US) B-mode imaging allows to subjectively estimate the fatty infiltration in the liver; however, it has a low performance for the detection of mild steatosis. Quantitative US is based on the analysis of the radiofrequency echoes detected by an US system, and it allows to calculate a backscatter coefficient or an attenuation coefficient or the sound speed. The estimation of the backscatter coefficient is rather cumbersome and requires the use of a phantom for addressing all sources of variability. Controlled attenuation parameter (CAP) available on the FibroScan® system (Echosens, France) measures the attenuation of the US beam. CAP is accurate in grading fatty infiltration-even though there is an overlap between consecutive grade of liver steatosis-and the values are not influenced by liver fibrosis. Several US manufacturers are developing or have already developed software for quantifying the attenuation of the US beam. Preliminary results show that proprietary technologies implemented in US systems seem more accurate than CAP for grading liver steatosis. Another available method for quantifying liver steatosis is based on the computation of the sound speed and the initial results appear promising.

Keywords: Non-alcoholic fatty liver disease; Chronic liver disease; Ultrasound; Controlled attenuation parameter; Quantitative ultrasound; Attenuation imaging

Core tip: An accurate estimation of the fat in the liver is important in the diagnostic work-up of patients with non-alcoholic fatty liver disease. Ultrasound B-mode imaging, which is widely used for the screening of liver disease, allows to subjectively estimate fatty infiltration in the liver; however, it has a low performance for the detection of mild steatosis. To partly overcome this limitation, some semi-quantitative scores have been proposed. Quantitative ultrasound is based on the analysis of the radiofrequency signals detected by an ultrasound system, and it allows to calculate objective parameters for quantifying the fat in the liver.