Accuracy of Two-Dimensional Shear Wave Elastography and Attenuation Imaging for Evaluation of Patients With Nonalcoholic Steatohepatitis

Relationship Between Greyscale Ultrasound Grading of Hepatic Steatosis and Attenuation Imaging

Background

Non-alcoholic fatty liver disease (NAFLD) has been rising worldwide due to the rising public health threat of metabolic syndrome. Because non-alcoholic steatohepatitis can proceed to liver fibrosis and cirrhosis, early identification and monitoring are critical for management. For the examination of NAFLD, greyscale ultrasound has been frequently employed. A relatively new technique, attenuation imaging (ATI), can quantitatively evaluate and compute the attenuation coefficient (AC). Our goal was to evaluate the performance and cutoff values of attenuation imaging to identify hepatic steatosis. As a reference standard, greyscale ultrasound was employed.

Method

A total of 207 patients were assessed from June to November 2021 after getting informed consent. The association between ATI values and greyscale grading to diagnose hepatic steatosis was investigated, and the Statistical Package for the Social Sciences (SPSS) version 21 (IBM Corp., Armonk, NY, USA) was used to analyze the data. In the analysis, the Spearman correlation and area under the receiver operating characteristic curve (AUROC) tests were performed. Receiver operating characteristic curve analysis was also used to assess ATI’s diagnostic capability and cutoff values.

Result

The correlation between ATI values and hepatic steatosis grades on greyscale was statistically significant (p < 0.05). Greyscale grading and ATI levels have a correlation coefficient (r) of 0.85, indicating a strong association. Steatosis grades 1, 2, and 3 had threshold ATI values of 0.65, 0.73, and 0.96 dB/cm/MHz, respectively. According to greyscale, the diagnostic ability of ATI for steatosis grades 1, 2, and 3 were 0.948 (95% CI: 0.917-0.979), 0.978 (95% CI: 0.961-0.995), and 1.000 (95% CI: 1.000-1.000), respectively.

Conclusions

Attenuation imaging is a reliable method for identifying liver steatosis, with great performance and a strong association with the greyscale ultrasound.

Efficacy of B-mode ultrasound-based attenuation for the diagnosis of hepatic steatosis: a systematic review/meta-analysis

The accuracy of attenuation coefficients and B-mode ultrasound for distinguishing between S0 (healthy, < 5% fat) and S1-3 (steatosis ≥ 5%) livers compared to a controlled attenuation parameter is unclear. This meta-analysis aimed to comprehensively assess the diagnostic performance of B-mode ultrasound imaging for evaluating steatosis of ≥ 5%. We searched the PubMed, Embase, and Web of Science databases for studies on the accuracy of B-mode ultrasound for differentiating S0 from S1-3 in adults with chronic liver disease. A bivariate random-effects model was performed to estimate the pooled sensitivity, specificity, positive (PLR) and negative likelihood ratios (NLR), and diagnostic odds ratios (DORs). Subgroup analyses by attenuation coefficient, conventional B-mode ultrasound findings, and B-mode ultrasound findings without semi-quantification methods were performed. Liver steatosis was scored as follows: S0, < 5%; S1, 5-33%; S2, 33-66%; and S3, > 66%. Nineteen studies involving 3240 patients were analyzed. The pooled sensitivity and specificity of B-mode ultrasound for detecting S1 were 0.70 (95% confidence interval [CI], 0.63-0.77) and 0.86 (95% CI 0.82-0.89), respectively. The pooled PLR, NLR, and DOR were 4.90 (95% CI 3.69-6.51), 0.35 (95% CI 0.27- 0.44), and 14.1 (95% CI 8.7-23.0), respectively. The diagnostic accuracy was better in patients with attenuation coefficients (area under the curve [AUC], 0.89; sensitivity, 0.75; specificity, 0.86) than in those with conventional B-mode findings (AUC, 0.80; sensitivity, 0.59; specificity, 0.83). In particular, the diagnostic value was better when the attenuation coefficient guided by B-mode ultrasound was utilized. To screen patients with steatosis of ≥ 5%, attenuation coefficient should be used.

Superb Microvascular Imaging-Based Vascular Index to Assess Adult Hepatic Steatosis: A Feasibility Study

The aim of the study was to assess the feasibility of using a superb microvascular imaging-based vascular index (SMI-VI) for evaluating adult hepatic steatosis. We prospectively compared liver parenchyma SMI-VI (color pixels/total pixels in the region of interest), portal vein velocity, hepatic artery Doppler parameters (peak systolic velocity, end diastolic velocity, resistive index) and serum lipid and alanine aminotransferase (ALT) levels between 16 normal livers and 34 steatotic livers using magnetic resonance imaging-proton density fat fraction (MRI-PDFF) as the reference. On the basis of a two-tailed t-test, differences in SMI-VI, portal vein velocity, MRI-PDFF and ALT between normal (MRI-PDFF <5%) and steatotic (MRI-PDFF ≥5%) livers were statistically significant (p < 0.02), whereas hepatic artery Doppler parameters and triglyceride levels were not (p > 0.05). We observed an inverse correlation of SMI-VI with MRI-PDFF (r = -0.88). With 0.19 as the best cutoff value, the area under the receiver operating characteristic curve, sensitivity and specificity of SMI-VI for determining ≥mild (MRI-PDFF ≥5%) non-alcoholic fatty liver disease (NAFLD) were 0.95, 96% and 94%, respectively. Our results indicate the feasibility of using SMI-VI to assess adult hepatic steatosis. SMI-VI is a potential surrogate marker in the screening for NAFLD.

Reliability of Performing Multiparametric Ultrasound in Adult Livers

PURPOSE

The aim of the study was to test inter-observer and intra-observer reliability of measuring multiparametric ultrasound in adult livers.

METHODS

We prospectively measured shear wave velocity (SWV, m/s), shear wave dispersion slope (SWD, m/s/kHz), attenuation coefficient (ATI, dB/cm/MHz), normalized local variance (NLV), and echo intensity ratio of liver to kidney (L/K ratio) in 21 adults who underwent liver magnetic resonance imaging-proton density fat fraction (MRI-PDFF). Intraclass correlation coefficient and 95% Bland-Altman limits of agreement (95% LOA) were used to analyze intra- and inter-observer reproducibility.

RESULTS

Based on liver MRI-PDFF, 21 participants (8 men and 13 women, mean age 55 years) were divided into group 1 (11 normal livers, MRI-PDFF <5%) and group 2 (10 steatotic livers, MRI-PDFF ≥5%). ICCs for intra-observer repeatability and inter-observer reproducibility in measuring multiple ultrasound parameters in both normal and steatotic livers were above 0.75. However, 95% confidence interval for measuring SWD in all livers and L/K ratio in normal livers was 0.38-0.90 and 0.47-0.91, respectively. Differences in SWV, SWD, ATI, NLV, L/K ratio, and MRI-PDFF between participants with and without hepatic steatosis were significant (p < .05), whereas serum biomarkers and body mass index were not (p > .05), based on a two-tailed t-test.

CONCLUSIONS

The results suggest that the repeatability and reproducibility for measuring liver SWV, ATI, and NLV are moderate to excellent, while those for SWD and L/K ratio are poor. Standardized machine settings, scanning protocols, and operator training are suggested in performing multiparametric ultrasound of the liver.

Non-invasive tests of non-alcoholic fatty liver disease

ABSTRACT

For the detection of steatosis, quantitative ultrasound imaging techniques have achieved great progress in past years. Magnetic resonance imaging proton density fat fraction is currently the most accurate test to detect hepatic steatosis. Some blood biomarkers correlate with non-alcoholic steatohepatitis, but the accuracy is modest. Regarding liver fibrosis, liver stiffness measurement by transient elastography (TE) has high accuracy and is widely used across the world. Magnetic resonance elastography is marginally better than TE but is limited by its cost and availability. Several blood biomarkers of fibrosis have been used in clinical trials and hold promise for selecting patients for treatment and monitoring treatment response. This article reviews new developments in the non-invasive assessment of non-alcoholic fatty liver disease (NAFLD). Accumulating evidence suggests that various non-invasive tests can be used to diagnose NAFLD, assess its severity, and predict the prognosis. Further studies are needed to determine the role of the tests as monitoring tools. We cannot overemphasize the importance of context in selecting appropriate tests.

US Attenuation for Liver Fat Quantification: An AIUM-RSNA QIBA Pulse-Echo Quantitative Ultrasound Initiative

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide, with an estimated prevalence of up to 30% in the general population and higher in people with type 2 diabetes. The assessment of liver fat content is essential to help identify patients with or who are at risk for NAFLD and to follow their disease over time. The American Institute of Ultrasound in Medicine-RSNA Quantitative Imaging Biomarkers Alliance Pulse-Echo Quantitative Ultrasound Initiative was formed to help develop and standardize acquisition protocols and to better understand confounding factors of US-based fat quantification. The three quantitative US parameters explored by the initiative are attenuation, backscatter coefficient, and speed of sound. The purpose of this review is to present the current state of attenuation imaging for fat quantification and to provide expert opinion on examination performance and interpretation. US attenuation methods that need further study are outlined.

Shear-Wave Dispersion Slope of the Liver: Effect of Study Protocol and Ascites on the Measurement Applicability

This study aimed to evaluate the shear-wave dispersion (SWD) scanning protocol including the minimum number of measurements and better size of the region of interest (ROI), as well as the influence of ascites on the measurement applicability. Patients who had undergone serial SWD examinations between July 2019 and December 2020 were included. In patients with chronic liver disease (group A), two different ROI sizes were applied, and at least 10 measurements were repeated to determine the minimum number of measurements and better ROI size. In patients with liver failure (group B), failure and unreliable results were compared between patients with and without ascites. A minimum of five measurements when using a 20-mm ROI and six measurements when using a 10-mm ROI were required. Compared with using a 20-mm ROI, a 10-mm ROI showed a higher unreliable rate. The failure and unreliable rates of SWD in patients with ascites were significantly higher than those in patients without ascites. SWD examination required at least five measurements when using a 20-mm ROI and six measurements when using a 10-mm ROI. A larger ROI was associated with higher reliability, and ascites influenced the failure and reliability of the SWD measurement.

Sources of Variability in Shear Wave Speed and Dispersion Quantification with Ultrasound Elastography: A Phantom Study

There is a growing interest in quantifying shear-wave dispersion (SWD) with ultrasound shear-wave elastography (SWE). Recent studies suggest that SWD complements shear-wave speed (SWS) in diffuse liver disease diagnosis. To accurately interpret these metrics in clinical practice, we analyzed the impact of operator-dependent acquisition parameters on SWD and SWS measurements. Considered parameters were the acquisition depth, lateral position and size of the region of interest (ROI), as well as the size of the SWE acquisition box. Measurements were performed using the Canon Aplio i800 system (Canon Medical Systems, Otawara, Tochigi, Japan) and four homogeneous elasticity phantoms with certified stiffness values ranging from 3.7 to 44 kPa. In general, SWD exhibited two to three times greater variability than SWS. The acquisition depth was the main variance-contributing factor for both SWS and SWD, which decayed significantly with depth. The lateral ROI position contributed as much as the acquisition depth to the total variance in SWD. Locations close to the initial shear-wave excitation pulse were more robust to biases because of inaccurate probe-phantom coupling. The size of the ROI and acquisition box did not introduce significant variations. These results suggest that future guidelines on multiparametric elastography should account for the depth- and lateral-dependent variability of measurements.

Assessment of chronic liver disease by multiparametric ultrasound: results from a private practice outpatient facility

PURPOSE

To assess chronic liver disease (CLD) using multiparametric US in a private practice setting in a cohort of patients with increased skin-to-liver distance.

METHODS

110 consecutive patients with increased skin-to-liver distance scheduled for US assessment of CLD were reviewed for study completion time, liver stiffness values (LS), attenuation imaging, and shear wave dispersion slope. The ROI was placed 2 cm below the liver capsule. The study included patients with NAFLD/NASH (68), hepatitis C (30), prior Fontan surgery (1), elevated liver function tests (5), alcohol abuse (3), hepatitis B (2), and primary biliary cirrhosis (1). IQR/M values were obtained. Comparison of less experienced sonographers (LES) and more experienced sonographers (MES) were evaluated through Student's t test for independent data. Pearson coefficient r of correlation among quantitative variables was calculated.

RESULTS

The mean time to perform the exam was 129.7 ± 62.1 s. There was a statistically significant difference between LES and MES. The mean IQR/M for LS was 12.3 ± 5.5% m/s. Overall, in a cohort of difficult patients, 4.5% of LS values were not reliable. Fat quantification using attenuation imaging had a mean value of 0.60 ± 0.15 dB/cm/MHz (range 0.35-0.98 cm/dB/MHz) with an IQR/M of 14.7 ± 9.2%. Less reliable measurements of steatosis were obtained in 4.5% of patients. The mean shear wave dispersion slope was 12.74 ± 4.05 (m/s)/kHz (range 7.7-27.5 (m/s)/kHz) with an IQR/M of 38.7 ± 20.2% (range 3-131%). 20.9% of patients had values suggestive of compensated advanced chronic liver disease (cACLD).

CONCLUSION

Multiparametric US can provide assessment of CLD in less than 3 min in most patients and identify patients at risk for cACLD.

Noninvasive assessment of hepatic steatosis using a pathologic reference standard: comparison of CT, MRI, and US-based techniques

Purpose

The present study compared the performance of computed tomography (CT), magnetic resonance imaging-derived proton density fat fraction (MRI-PDFF), controlled attenuation parameter (CAP), grayscale ultrasonography (US), and attenuation imaging (ATI) for the diagnosis of hepatic steatosis (HS).

Methods

In total, 120 prospectively recruited patients who underwent hepatic resection between June 2018 and June 2020 were retrospectively analyzed. CT, MRI-PDFF, CAP, grayscale US, and ATI were performed within 3 months before surgery. Diagnostic performance for HS ≥5% and HS >33% was compared using the area under the curve (AUC) of receiver operating characteristic curves. Histopathologic examinations served as the reference standard for the degree of HS.

Results

For detecting HS ≥5%, MRI-PDFF (AUC, 0.946) significantly outperformed CT, CAP and grayscale US (AUC, 0.807, 0.829, and 0.761, respectively) (P<0.01 for all). ATI (AUC, 0.892) was the second-best modality and significantly outperformed grayscale US (P=0.001). In pairwise comparisons, there were no significant differences between the AUC of ATI and the values of MRI-PDFF, CT, or CAP (P=0.133, P=0.063, and P=0.150, respectively). For detecting HS >33%, all the modalities provided good diagnostic performance without significant differences (AUC, 0.887-0.947; P>0.05 for all).

Conclusion

For detecting HS ≥5%, MRI-PDFF was the best imaging modality, while ATI outperformed grayscale US. For detecting HS >33%, all five imaging tools demonstrated good diagnostic performance.

Diagnostic accuracy of two-dimensional shear wave elastography and transient elastography in nonalcoholic fatty liver disease

INTRODUCTION

Two-dimensional shear wave elastography (2D-SWE) and vibration-controlled transient elastography (VCTE) provide noninvasive assessment of hepatic fibrosis. We compared performance of 2D-SWE and VCTE for fibrosis detection in nonalcoholic fatty liver disease (NAFLD).

METHODS

We performed a prospective study of adults with NAFLD who underwent 2D-SWE, VCTE, and liver biopsy analysis (using Nonalcoholic Steatohepatitis Clinical Research Network scoring system). The primary outcome was hepatic fibrosis (stage ⩾ 1); secondary outcomes included dichotomized fibrosis stages. Area under receiver operating characteristic curve (AUROC) analyses were used to compare 2D-SWE and VCTE performance.

RESULTS

A total of 114 adults with a median BMI of 31.2 kg/m² were included. The VCTE was better than 2D-SWE for the detection of fibrosis (AUROC: 0.81 versus 0.72, p = 0.03). The VCTE detected fibrosis stage 2, 3, or 4 with AUROCs of 0.86 (95% CI, 0.80-0.93), 0.91 (95% CI, 0.82-0.99), and 0.96 (95% CI, 0.91-1.00). The 2D-SWE detected fibrosis stage 2, 3, or 4 with AUROCs of 0.84 (95% CI, 0.76-0.92), 0.88 (95% CI, 0.81-0.96), and 0.93 (95% CI, 0.86-0.99).

CONCLUSION

In a prospective study including more than 100 adults with NAFLD, we found VCTE to be more accurate than 2D-SWE in detecting fibrosis; these modalities, however, are comparable in assessing for higher stages of fibrosis.

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

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.

Multiparametric US for Identifying Patients with High-Risk NASH: A Derivation and Validation Study

Background Nonalcoholic fatty liver disease (NAFLD) is common in the general population but identifying patients with high-risk nonalcoholic steatohepatitis (NASH) who are candidates for pharmacologic therapy remains a challenge. Purpose To develop a score to identify patients with high-risk NASH, defined as NASH with an NAFLD activity score (NAS) of 4 or greater and clinically significant fibrosis (stage 2 [F2] or higher). Materials and Methods This was a cross-sectional secondary analysis of data prospectively collected between April 2017 and March 2019 for a group of patients with NAFLD in Japan (Japan NAFLD, the derivation data set) with contemporaneous two-dimensional shear-wave elastography and biopsy-proven NAFLD (age range, 20-89 years). Three US markers (liver stiffness [LS, measured in kilopascals], attenuation coefficient [AC, measured in decibels per centimeter per megahertz], and dispersion slope [DS, measured in meters per second per kilohertz]) were determined, together with aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and the AST-to-ALT ratio. The best-fit multivariate logistic regression model for identifying patients with high-risk NASH was determined. Diagnostic performance was assessed by using the area under the receiver operating characteristic curve (AUC). The findings were validated in an independent data set (Korea NAFLD; age range, 20-78 years). Results The Japan NAFLD data set included 111 patients (mean age, 53 years ± 18 [standard deviation]; 57 men), 84 (76%) with NASH. The Korea NAFLD data set included 102 patients (mean age, 48 years ± 18; 43 men), 55 (36%) with NASH. The most predictive model (LAD NASH score) combined LS, AC, and DS. Performance was satisfactory in both the derivation sample (AUC, 0.86; 95% CI: 0.79, 0.93) and the validation sample (AUC, 0.88; 95% CI: 0.80, 0.95). The LAD NASH score showed a positive predictive value of 86.5% and a negative predictive value of 87.5% for high-risk NASH in the derivation sample. Conclusion A score combining three US markers may be useful for noninvasive identification of patients with high-risk nonalcoholic steatohepatitis for inclusion in clinical trials and pharmacologic therapy. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Lockhart in this issue.

The most appropriate region-of-interest position for attenuation coefficient measurement in the evaluation of liver steatosis

PURPOSE

Attenuation imaging (ATI) is a new noninvasive ultrasound technique for assessing steatosis grade (S). However, validated region-of-interest (ROI) sampling strategies are not currently available. We investigated the diagnostic performance of various ATI-ROI positions for determining histopathologic S in patients with nonalcoholic fatty liver disease (NAFLD).

METHODS

This retrospective study included 105 patients with biopsy-proven NAFLD. All attenuation coefficient (AC, dB/cm/MHz) measurements were obtained by the same hepatologist using a commercially available ultrasound system on the same day as liver biopsy. Mean (± standard deviation) age and body mass index of the patients were 53 (± 18) years and 27.1 (± 4.1) kg/m², respectively. The numbers of patients with steatosis affecting < 5%, 5-33%, 33-66%, and > 66% of hepatocytes were 8, 50, 29, and 18, respectively. The ATI-ROI was placed at three different positions for AC measurement using a dedicated workstation: the upper edge of the area ROI, twice the depth of the liver capsule, and the lower edge of the area ROI. Diagnostic performance was evaluated using the area under the receiver-operating characteristic curve (AUC).

RESULTS

The AUCs of AC at the three ATI-ROI positions were 0.734 (95% confidence interval [CI]: 0.470-0.998), 0.750 (0.639-0.861), and 0.878 (0.788-0.968) for S ≥ 1; 0.503 (0.392-0.615), 0.824 (0.741-0.907), and 0.809 (0.724-0.895) for S ≥ 2; and 0.606 (0.486-0.726), 0.849 (0.767-0.932), and 0.737 (0.626-0.848) for S = 3, respectively.

CONCLUSION

For accurate steatosis grade assessment, the ATI-ROI should not be placed at the upper edge of the area ROI.

Quantitative assessment of fatty liver using ultrasound attenuation imaging

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease, with an incidence of 20-40% worldwide, making it a major healthcare problem. Because NAFLD can progress to liver fibrosis and cirrhosis through non-alcoholic steatohepatitis, early detection and monitoring of hepatic steatosis are essential for management of NAFLD patients. Even though conventional B-mode ultrasound (US) has been widely used for the evaluation of NAFLD owing to its safety and easy accessibility, its subjective nature and limited accuracy in detecting mild steatosis are major limitations. To overcome the current limitations of conventional B-mode US, attenuation imaging (ATI) based on two-dimensional B-mode US has been developed. ATI can quantitatively assess the degree of hepatic steatosis by calculating the attenuation coefficient, which reflects the degree of US beam attenuation transmitted into the liver tissue. After the first study was published in 2019, several clinical studies using ATI to evaluate hepatic steatosis have reported promising results. In this review, the basic physics, measurement protocol, and reported diagnostic accuracy of ATI in evaluating hepatic steatosis will be discussed.

Diagnostic accuracy of ultrasound-guided attenuation parameter as a noninvasive test for steatosis in non-alcoholic fatty liver disease

The purpose of this study was to evaluate the diagnostic accuracy of the ultrasound-guided attenuation parameter (UGAP) using the LOGEQ E10 for hepatic steatosis in non-alcoholic fatty liver disease (NAFLD) patients and directly compare UGAP with attenuation imaging (ATI) and controlled attenuation parameter (CAP). We prospectively analyzed 105 consecutive patients with NAFLD who underwent UGAP, ATI, CAP, and liver biopsy on the same day between October 2019 and April 2021. The diagnostic ability of the UGAP-determined attenuation coefficient (AC) was evaluated using receiver operating characteristic (ROC) curve analysis, and its correlation with ATI-determined AC values or CAP values was investigated. The success rate of UGAP was 100%. The median IQR/med obtained by UGAP was 4.0%, which was lower than that of ATI and CAP (P < 0.0001). The median ACs obtained by UGAP for grades S0 (control), S1, S2, and S3 were 0.590, 0.670, 0.750, and 0.845 dB/cm/MHz, respectively, demonstrating a stepwise increase with increasing hepatic steatosis severity (P < 0.0001). The areas under the ROC curve of UGAP for identifying ≥ S1, ≥ S2, and S3 were 0.890, 0.906, and 0.912, respectively, which were significantly better than the results obtained with CAP for identifying S3. Furthermore, the correlation coefficient between UGAP-AC and ATI-AC values was 0.803 (P < 0.0001), indicating a strong relationship. Our results indicate that UGAP has high diagnostic accuracy for detecting and grading hepatic steatosis in patients with NAFLD.

Performance of the Attenuation Imaging Technology in the Detection of Liver Steatosis

OBJECTIVES

The main aim was to assess the performance and cutoff value for the detection of liver steatosis (grade S > 0) with the Attenuation Imaging-Penetration (ATI-Pen) algorithm available on the Aplio i-series ultrasound systems (Canon Medical Systems, Otawara, Japan). The magnetic resonance imaging-derived proton density fat fraction (MRI-PDFF) was used as the reference standard. Secondary aims were to compare the results to those obtained with the previous ATI algorithm (Attenuation Imaging-General [ATI-Gen]) and with the controlled attenuation parameter (CAP) and to generate a regression equation between ATI-Pen and ATI-Gen values.

METHODS

Consecutive adult patients potentially at risk of liver steatosis were prospectively enrolled. Each patient underwent ultrasound quantification of liver steatosis with ATI-Pen and ATI-Gen and a CAP assessment with the FibroScan system (Echosens, Paris, France). The MRI-PDFF evaluation was performed within a week. The correlations between ATI-Pen, ATI-Gen, the CAP, and the MRI-PDFF were analyzed with the Pearson rank correlation coefficient. The diagnostic performance of ATI-Pen, ATI-Gen, and the CAP was assessed with receiver operating characteristic curves and an area under the receiver operating characteristic curve (AUROC) analysis.

RESULTS

Seventy-two individuals (31 male and 41 female) were enrolled. Correlation coefficients of ATI-Pen, ATI-Gen, and the CAP with the MRI-PDFF were 0.78, 0.83, and 0.58, respectively. The AUROCs of ATI-Pen, ATI-Gen, and the CAP for detecting steatosis (S > 0) were 0.90 (95% confidence interval, 0.81-0.96), 0.92 (0.82-0.98), and 0.85 (0.74-0.92), and the cutoffs were greater than 0.69 dB/cm/MHz, greater than 0.62 dB/cm/MHz, and greater than 273 dB/m. The regression equation between ATI-Pen and ATI-Gen was ATI-Pen = 0.88 ATI-Gen + 0.13.

CONCLUSIONS

Attenuation Imaging is a reliable tool for detecting liver steatosis, showing an excellent correlation with the MRI-PDFF and high performance with AUROCs of 0.90 or higher.

The effect of water intake on ultrasound tissue characteristics and hemodynamics of adult livers

Aim of the study

To assess the effect of water intake on ultrasound tissue characteristics and hemodynamics of adult livers.

Material and methods

In February 2020, we prospectively performed ultrasound shear wave elastography and attenuation imaging (ATI) of the liver parenchyma, and spectral Doppler sonography of the portal vein and hepatic artery in 19 adult healthy volunteers (10 men and 9 women, mean age 27 years, mean body mass index 24.65 kg/m²). We measured liver shear wave velocity (SWV, m/s), shear wave dispersion (SWD, m/s/kHz), attenuation coefficient (dB/cm/MHz), main portal vein velocity (PVV, cm/s), hepatic artery peak systolic velocity (PSV, cm/s), and end diastolic velocity (EDV, cm/s) immediately before and at different time points (15, 30, 45, and 60 minutes) after water intake (1.0 l water and 1.5 l water for body weight < 150 lbs. and ≥ 150 lbs., respectively).

Results

The differences in SWV, PVV, hepatic artery PSV and EDV before and after water intake were significant (p < 0.01) whereas the differences in SWD and ATI were not (p > 0.05) based on repeated measures ANOVA tests. The values of SWV, PVV, PSV, and EDV reached a peak at 30-45 minutes and returned to baseline 60 minutes after water intake. We observed positive correlations of SWV with PVV, PSV, and EDV in linear regression analyses (r² > 0.73).

Conclusions

Water intake affects the liver stiffness and hemodynamics. No water intake at least one hour prior to liver ultrasound elastography and Doppler sonography is recommended.

Determination of Non-Invasive Biomarkers for the Assessment of Fibrosis, Steatosis and Hepatic Iron Overload by MR Image Analysis. A Pilot Study

The reference diagnostic test of fibrosis, steatosis, and hepatic iron overload is liver biopsy, a clear invasive procedure. The main objective of this work was to propose HSA, or human serum albumin, as a biomarker for the assessment of fibrosis and to study non-invasive biomarkers for the assessment of steatosis and hepatic iron overload by means of an MR image acquisition protocol. It was performed on a set of eight subjects to determine fibrosis, steatosis, and hepatic iron overload with four different MRI sequences. We calibrated longitudinal relaxation times (T1 [ms]) with seven human serum albumin (HSA [%]) phantoms, and we studied the relationship between them as this protein is synthesized by the liver, and its concentration decreases in advanced fibrosis. Steatosis was calculated by means of the fat fraction (FF [%]) between fat and water liver signals in “fat-only images” (the subtraction of in-phase [IP] images and out-of-phase [OOP] images) and in “water-only images” (the addition of IP and OOP images). Liver iron concentration (LIC [µmol/g]) was obtained by the transverse relaxation time (T2* [ms]) using Gandon’s method with multiple echo times (TE) in T2-weighted IP and OOP images. The preliminary results showed that there is an inverse relationship (r = −0.9662) between the T1 relaxation times (ms) and HSA concentrations (%). Steatosis was determined with FF > 6.4% and when the liver signal was greater than the paravertebral muscles signal, and thus, the liver appeared hyperintense in fat-only images. Hepatic iron overload was detected with LIC > 36 µmol/g, and in these cases, the liver signal was smaller than the paravertebral muscles signal, and thus, the liver behaved as hypointense in IP images.

Conventional ultrasound for diagnosis of hepatic steatosis is better than believed

BACKGROUND

Hepatic steatosis is a condition frequently encountered in clinical practice, with potential progression towards fibrosis, cirrhosis, and hepatocellular carcinoma. Detection and staging of hepatic steatosis are of most importance in nonalcoholic fatty liver disease (NAFLD), a disease with a high prevalence of more than 1 billion individuals affected. Ultrasound (US) is one of the most used noninvasive imaging techniques used in the diagnosis of hepatic steatosis. Detection of hepatic steatosis with US relies on several conventional US parameters, which will be described. US is the first-choice imaging in adults at risk for hepatic steatosis. The use of some scoring systems may add additional accuracy especially in assessing the severity of hepatic steatosis.

SUMMARY

In the presented paper, we discuss screening and risk stratification, ultrasound features for diagnosing hepatic steatosis, B-mode criteria, focal fatty patterns and Doppler features of the hepatic vessels, and the value of the different US signs for the diagnosis of liver steatosis including classifying the severity of steatosis using different US scores. Limitations of conventional B-mode and Doppler features in the evaluation of hepatic steatosis are also discussed, including those in grading and assessing the complications of steatosis, namely fibrosis and nonalcoholic steatohepatitis.

KEY MESSAGES

Ultrasound is the first-line imaging examination for the screening and follow-up of patients with liver steatosis. The use of some scoring systems may add additional accuracy in assessing the severity of steatosis. Conventional B-mode and Doppler ultrasound have limitations in grading and assessing the complications of steatosis.

Accuracy of the ultrasound attenuation coefficient for the evaluation of hepatic steatosis: a systematic review and meta-analysis of prospective studies

PURPOSE

The accurate detection and quantification of hepatic steatosis using a noninvasive method are important for the management of nonalcoholic fatty liver disease. We performed a systematic review and meta-analysis of the accuracy of the ultrasound-measured attenuation coefficient (AC) in the evaluation of hepatic steatosis.

METHODS

The PubMed, Embase, and Cochrane databases were searched for prospective studies reporting the diagnostic accuracy of AC for assessing hepatic steatosis. The meta-analytic pooled sensitivity and specificity of AC for any grade of steatosis (S≥1) and advanced steatosis (S≥2) were estimated using a bivariate random-effects model. Meta-regression analysis was conducted to investigate the causes of heterogeneity among studies.

RESULTS

Thirteen studies including 1,509 patients were identified. The pooled sensitivity and specificity of AC for S≥1 were 76% (95% confidence interval [CI], 73% to 80%; I2=43%) and 84% (95% CI, 77% to 89%; I2=74%), respectively, while for S≥2 they were 87% (95% CI, 83% to 91%; I2=0%) and 79% (95% CI, 75% to 83%; I2=59%), respectively. Study heterogeneity was associated with body mass index (BMI) and the prevalence of steatosis or significant fibrosis.

CONCLUSION

AC can be clinically useful for assessing hepatic steatosis, with good overall diagnostic performance. The data reported in the published literature differed according to BMI and the prevalence of steatosis or significant fibrosis, and careful interpretation with consideration of these factors might be needed.

Perspectives on Precision Medicine Approaches to NAFLD Diagnosis and Management

Precision medicine defines the attempt to identify the most effective approaches for specific subsets of patients based on their genetic background, clinical features, and environmental factors. Nonalcoholic fatty liver disease (NAFLD) encompasses the alcohol-like spectrum of liver disorders (steatosis, steatohepatitis with/without fibrosis, and cirrhosis and hepatocellular carcinoma) in the nonalcoholic patient. Recently, disease renaming to MAFLD [metabolic (dysfunction)-associated fatty liver disease] and positive criteria for diagnosis have been proposed. This review article is specifically devoted to envisaging some clues that may be useful to implementing a precision medicine-oriented approach in research and clinical practice. To this end, we focus on how sex and reproductive status, genetics, intestinal microbiota diversity, endocrine and metabolic status, as well as physical activity may interact in determining NAFLD/MAFLD heterogeneity. All these factors should be considered in the individual patient with the aim of implementing an individualized therapeutic plan. The impact of considering NAFLD heterogeneity on the development of targeted therapies for NAFLD subgroups is also extensively discussed.

Diagnostic Value of Ultrasound in Fatty Liver Disease

Hepatic steatosis is a commonly seen phenomenon in clinical practice and is the result of the accumulation of lipids in the hepatocytes. In most cases steatosis refers to nonalcoholic fatty liver disease (NAFLD), but it also occurs in other diseases of the liver parenchyma of a different etiology and is the result of the dysregulation of metabolic processes. Consequently, inflammatory processes can induce progressive fibrosis. Due to the high prevalence of fatty liver disease, a further increase in metabolic liver cirrhosis with corresponding complications can be expected in the near future. Due to its broad availability, ultrasound is particularly important, especially for the management of NAFLD. In addition to diagnosis and risk stratification, the monitoring of high-risk patients in NAFLD is becoming increasingly clinically important. Multimodality ultrasound includes B-mode and duplex methods, analysis of tissue stiffness (elastography), contrast-enhanced imaging (CEUS), and steatosis quantification. When using ultrasound in fatty liver disease, a standardized approach that takes into account the limitations of the method is essential.

The Use of Two-Dimensional Shear Wave Elastography in People with Obesity for the Assessment of Liver Fibrosis in Non-Alcoholic Fatty Liver Disease

Obesity is associated with significant comorbidities, including non-alcoholic fatty liver disease (NAFLD). Given its potential to progress to advanced liver disease, monitoring the extent and progress of liver fibrosis and assessing its fibrosis stage are essential. Although liver biopsy is considered to be the gold standard for liver fibrosis staging, it is an invasive procedure with risk of complications. Considering the rising prevalence of obesity and NAFLD globally, developing non-invasive diagnostic methods is a priority. Transient elastography (TE) is increasingly being used to assess the severity of liver disease. However, in the presence of severe obesity, the increased thickness of subcutaneous adipose tissue and changes in anatomy may affect its diagnostic accuracy. Two-dimensional shear wave elastography (2D-SWE) assesses the liver stiffness in real time along with simultaneous anatomic B-mode ultrasound imaging and allows selection of the region of interest. This would suggest that 2D-SWE has several advantages over TE in patients with severe obesity. The purpose of this review is to examine the current literature addressing the use of 2D-SWE in the assessment of liver fibrosis in patients with NAFLD. This review also examines the evidence on the use of 2D-SWE in patients with obesity and NAFLD and compares it to TE as a novel and non-invasive method of assessing liver fibrosis.

Hepatocellular Carcinoma and Non-Alcoholic Fatty Liver Disease: A Step Forward for Better Evaluation Using Ultrasound Elastography

Simple Summary

Non-alcoholic fatty liver disease (NAFLD) attracts a lot of attention, due to the increasing prevalence and progression to fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Consequently, new non-invasive, cost-effective diagnostic methods are needed. This review aims to explore the diagnostic performance of ultrasound (US) elastography in NAFLD and NAFLD-related HCC, adding a new dimension to the conventional US examination—the liver stiffness quantification. The vibration controlled transient elastography (VCTE), and 2D-Shear wave elastography (2D-SWE) are effective in staging liver fibrosis in NAFLD. VCTE presents the upside of assessing steatosis through the controlled attenuation parameter. Hereby, we critically reviewed the elastography techniques for the quantitative characterization of focal liver lesions (FLLs), focusing on HCC: Point shear wave elastography and 2D-SWE. 2D-SWE presents a great potential to differentiate malignant from benign FLLs, guiding the clinician towards the next diagnostic steps. As a disease-specific surveillance tool, US elastography presents prognostic capability, improving the NAFLD-related HCC monitoring.

Abstract

The increasing prevalence of non-alcoholic fatty liver disease (NAFLD) in the general population prompts for a quick response from physicians. As NAFLD can progress to liver fibrosis, cirrhosis, and even hepatocellular carcinoma (HCC), new non-invasive, rapid, cost-effective diagnostic methods are needed. In this review, we explore the diagnostic performance of ultrasound elastography for non-invasive assessment of NAFLD and NAFLD-related HCC. Elastography provides a new dimension to the conventional ultrasound examination, by adding the liver stiffness quantification in the diagnostic algorithm. Whilst the most efficient elastographic techniques in staging liver fibrosis in NAFLD are vibration controlled transient elastography (VCTE) and 2D-Shear wave elastography (2D-SWE), VCTE presents the upside of assessing steatosis through the controlled attenuation parameter (CAP). Hereby, we have also critically reviewed the most important elastographic techniques for the quantitative characterization of focal liver lesions (FLLs), focusing on HCC: Point shear wave elastography (pSWE) and 2D-SWE. As our paper shows, elastography should not be considered as a substitute for FLL biopsy because of the stiffness values overlap. Furthermore, by using non-invasive, disease-specific surveillance tools, such as US elastography, a subset of the non-cirrhotic NAFLD patients at risk for developing HCC can be detected early, leading to a better outcome. A recent ultrasomics study exemplified the wide potential of 2D-SWE to differentiate benign FLLs from malignant ones, guiding the clinician towards the next steps of diagnosis and contributing to better long-term disease surveillance.