Quantitative Diagnosis of Nonalcoholic Fatty Liver Disease with Ultrasound Attenuation Imaging in a Biopsy-Proven Cohort

Performance of Magnetic Resonance Imaging and Ultrasound for Identifying the Different Degrees of Hepatic Steatosis: A Systematic Review and Meta-analysis

BACKGROUND

MRI proton density fat fraction (MRI-PDFF), controlled attenuation parameters (CAP), and attenuation coefficients (AC) are capable of steatosis characterization and may be useful as noninvasive alternatives for diagnosing hepatic steatosis.

PURPOSE

This meta-analysis aimed to evaluate the performance of MRI-PDFF, CAP, and AC in grading hepatic steatosis, using histology as the reference standard.

METHODS

We conducted a comprehensive search of the PubMed, Cochrane Library, Embase, and Web of Science databases until June 2024. The quality of eligible studies was assessed. Pooled sensitivity, specificity, and area under receiver operating characteristic (AUC) curves were calculated using a bivariate random-effects model. Meta-regression analysis, subgroup analysis, and Deeks' test were performed to explore heterogeneity and assess publication bias.

RESULTS

This meta-analysis included 38 studies with 5056 patients with metabolic dysfunction-associated steatotic liver disease. The AUC values for grading steatosis ≥S1, ≥S2, and ≥S3 were 0.99, 0.89, and 0.90 for MRI-PDFF, 0.95, 0.84, and 0.77 for CAP, and 0.97, 0.90, and 0.89 for AC, respectively. CAP demonstrated lower accuracy for detecting steatosis grades ≥S2 and ≥S3 compared to MRI-PDFF (0.89 vs. 0.84, p<0.001; 0.90 vs. 0.77, p<0.001) and AC (0.90 vs. 0.84, p<0.001; 0.89 vs. 0.77, p<0.001). Subgroup analyses revealed that MRI-PDFF and CAP exhibited superior diagnostic performance in diagnosing ≥S2 and ≥S3 steatosis among individuals in Asia, with a body mass index ≤30 kg/m2, and age <51 years.

CONCLUSION

A direct comparison with CAP showed greater accuracy for MRI-PDFF and AC in diagnosing moderate and severe steatosis, and similar diagnostic performance for MRI-PDFF and AC. For patients with steatosis, AC should be incorporated into routine ultrasound screening.

Preliminary study on determining the optimal position of region of interest for evaluating hepatic steatosis using ultrasound Attenuation imaging

PURPOSE

To find the optimal position of region of interest (ROI) for evaluating hepatic steatosis using attenuation imaging (ATI) in patients with metabolic dysfunction-associated fatty liver disease (MAFLD).

METHODS

We retrospectively enrolled 143 consecutive patients who underwent percutaneous liver biopsy for the evaluation of MAFLD between October 2020 and October 2022. All ATI measurements were performed by the same radiologist. The ATI-ROI was placed at four different positions using a specialized workstation: the top edge of the sampling box (P1), the lower edge of the dark orange region (P2), 0.5 cm and 1 cm below the lower edge of the dark orange region (P3 and P4). Multivariate linear regression analysis and the area under the curve (AUC) analysis were performed.

RESULTS

The AUCs of ATI at the four different ATI-ROI positions were 0.472 (95% confidence interval [CI]: 0.362-0.581), 0.693(0.611-0.768), 0.757(0.611-0.768), and 0.809 (0.735-0.870) for ≥ S1; 0.544 (0.459-0.628), 0.779 (0.702-0.844), 0.842 (0.772-0.898), and 0.865 (0.798-0.916) for ≥ S2; and 0.655 (0.571-0.733), 0.904 (0.843-0.947), 0.95 (0.9-0.979), and 0.949 (0.9-0.979) for S3, respectively. The factor that most significantly affected ATI was steatosis grade(P<0.001), when ATI-ROI was placed at the position of P2, P3, and P4.

CONCLUSION

Hepatic steatosis grade was the most significant determinant factor for ATI value at multivariate analysis. When clinicians conduct ATI measurement, the dark orange region indicating the area of reverberation artifact should be avoided, and placing the ATI-ROI 1 cm below the lower edge of the dark orange region may be a better choice.

Added Value of Dynamic Contrast-Enhanced Ultrasound Analysis for Differential Diagnosis of Small (≤20 mm) Solid Pancreatic Lesions

OBJECTIVE

To evaluate the added value of dynamic contrast-enhanced ultrasound (DCE-US) analysis in pre-operative differential diagnosis of small (≤20 mm) solid pancreatic lesions (SPLs).

METHODS

In this retrospective study, patients with biopsy or surgerical resection and histopathologically confirmed small (≤20 mm) SPLs were included. One wk before biopsy/surgery, pre-operative B-mode ultrasound and contrast-enhanced ultrasound were performed. An ultrasonic system (ACUSON Sequoia, Siemens Medical Solutions, PA, USA) equipped with a 5C1 MHz convex array transducer was utilized. A dose of 1.5 ml SonoVue (Bracco, Italy) was injected as the contrast agent. Time-intensity curves were generated using VueBox software (Bracco) and various DCE-US quantitative parameters were subsequently calculated after curve fitting. Univariate and multivariate logistic regression analysis were utilized.

RESULTS

From August 2020 to November 2023, a total of 76 patients (31 males and 45 females; mean age: 61.9 ± 10.5 y) with 76 small (≤20 mm) SPLs were included. Mean size of the lesions was 16.4 ± 0.4 mm (range: 7-20 mm). Final diagnosis included 37 benign and 39 malignant small SPLs. On B-mode ultrasound, the majority of malignant (37/39, 94.9%) and benign SPLs (30/37, 81.1%) were hypo-echoic lesions with ill-defined borders and irregular shapes (p > 0.05). During the arterial phase of contrast-enhanced ultrasound, most SPLs (59/76, 77.6%) exhibited iso-enhancement when compared with surrounding pancreatic parenchyma. Subsequently, 82.1% (32/39) of malignant SPLs and 35.1% (13/37) of benign SPLs demonstrated wash-out in the venous phase and showed hypo-enhancement in venous and late phases (p > 0.05). Compared with benign SPLs, the time-intensity curves of small malignant SPLs revealed earlier and lower enhancement in the arterial phase, and a faster decline during the venous phase with a decreased area under the curve. Among the quantitative parameters, a lower peak enhancement ratio and higher fall time ratio were more common in small malignant SPLs (p < 0.05). For DCE-US analysis, the combined areas under the curve of significant quantitative parameters was 0.919, with 87.2% sensitivity and 86.5% specificity when differentiating between small malignant and benign SPLs. This result was better than contrast-enhanced computed tomography, which has a sensitivity of 74.4% and a specificity of 75.7%.

CONCLUSION

DCE-US analysis provides added value for the pre-operative differential diagnosis of small malignant SPLs.

Quantitative ultrasound analysis for non-invasive assessment of hepatic steatosis in metabolic dysfunction-associated steatotic liver disease

ObjectiveTo evaluate the diagnostic performance of novel tissue attenuation imaging (TAI) and tissue scatter distribution imaging (TSI) tools in detecting and grading hepatic steatosis using controlled attenuation parameter (CAP) as reference standard.MethodsA total of 185 participants with suspected metabolic dysfunction-associated steatotic liver disease (MASLD) were prospectively enrolled, and all underwent CAP and quantitative ultrasound (QUS) testing. Correlations between CAP, biological data, TAI and TSI were assessed. The influence factors of TAI and TSI as well as the diagnostic performance of TAI and TSI in detecting hepatic steatosis were evaluated.ResultsThe QUS parameters (TAI and TSI) showed good intra-observer reliability with ICC of 0.972 and 0.777, respectively. The correlation of CAP with TAI was higher than that of TSI (0.724 vs 0.360, P < 0.05). Multivariate Regression analysis showed that CAP was an important influence factor of TAI and TSI (P < 0.001). The area under the ROC curve (CAP > 250 dB/m) of TAI and TSI tools for detecting hepatic steatosis was 0.876 (95% CI: 0.813-0.923; P < 0.0001) and 0.797(95% CI: 0.724-0.857; P < 0.001), respectively; the sensitivity was 67.18% and 83.21%, the specificity was 95.65% and 69.57%, and the cut-off values were 0.93 dB/cm/MHz and 91.28, respectively. When TAI and TSI were combined, the area under the ROC curve was 0.881, with a sensitivity of 80.92% and a specificity of 82.61%. The Delong test showed that the combined diagnosis of TAI and TSI was equivalent to the use of TAI alone (P > 0.05).ConclusionTAI and TSI provided good intra-observer reliability, correlated well with CAP, and helped to detect and stage hepatic steatosis.

Quantitative Ultrasound and Ultrasound-Based Elastography for Chronic Liver Disease: Practical Guidance, From the AJR Special Series on Quantitative Imaging

Quantitative ultrasound (QUS) and ultrasound-based elastography techniques are emerging as non-invasive effective methods for assessing chronic liver disease. They are more accurate than B-mode imaging alone and more accessible than MRI as alternatives to liver biopsy. Early detection and monitoring of diffuse liver processes such as steatosis, inflammation, and fibrosis play an important role in guiding patient management. The most widely available and validated techniques are attenuation-based QUS techniques and shear-wave elastography techniques that measure shear-wave speed. Other techniques are supported by a growing body of evidence and are increasingly commercialized. This review explains general physical concepts of QUS and ultrasound-based elastography techniques for evaluating chronic liver disease. The first section describes QUS techniques relying on attenuation, backscatter, and speed of sound. The second section discusses ultrasound-based elastography techniques analyzing shear-wave speed, shear-wave dispersion, and shear-wave attenuation. With an emphasis on clinical implementation, each technique's diagnostic performance along with thresholds for various clinical applications are summarized, to provide guidance on analysis and reporting for radiologists. Measurement methods, advantages, and limitations are also discussed. The third section explores developments in quantitative contrast-enhanced and vascular ultrasound that are relevant to chronic liver disease evaluation.

Associations Between Multiparametric US-Based Indicators and Pathological Status in Patients with Metabolic Associated Fatty Liver Disease

OBJECTIVE

Noninvasive evaluation of metabolic dysfunction-associated fatty liver disease (MAFLD) using ultrasonography holds significant clinical value. The associations between ultrasound (US)-based parameters and the pathological spectra remain unclear and controversial. This study aims to investigate the associations thoroughly.

METHODS

The participants with MAFLD undergoing liver biopsy and multiparametric ultrasonography were prospectively recruited from December 2020 to September 2022. Three US-based parameters, namely attenuation coefficient (AC), liver stiffness (LS) and dispersion slope (DS) were obtained. The relationship between these parameters and steatosis grades, inflammation grades and fibrosis stages was examined.

RESULTS

In this study with 116 participants, AC values significantly differed across distinct steatosis grades (p < 0.001), while DS and LS values varied among inflammation grades (p < 0.001) and fibrosis stages (p < 0.001). The area under the receiver operating characteristic curves (AUCs) of AC ranged from 0.82 to 0.84 for differentiating steatosis grades, while AUCs of LS ranged from 0.62 to 0.76 for distinguishing inflammation grades and 0.83-0.95 for discerning fibrosis stages. AUCs for DS ranged from 0.79 to 0.81 in discriminating inflammation grades and 0.80-0.88 for differentiating fibrosis stages. Subgroup analysis revealed that LS demonstrated different trends in inflammation grade but consistent trends in fibrosis stage across subgroups, whereas DS showed consistent trends for both inflammation grade and fibrosis stage across all subgroups.

CONCLUSION

AC values indicate the degree of hepatic steatosis but not inflammation or fibrosis. LS values are determined only by fibrosis stage and are not associated with inflammation grades. DS values are associated with both fibrosis and inflammation grades.

WFUMB Guidelines/Guidance on Liver Multiparametric Ultrasound. Part 2: Guidance on Liver Fat Quantification

The World Federation for Ultrasound in Medicine and Biology (WFUMB) has promoted the development of this document on multiparametric ultrasound. Part 2 is a guidance on the use of the available tools for the quantification of liver fat content with ultrasound. These are attenuation coefficient, backscatter coefficient, and speed of sound. All of them use the raw data of the ultrasound beam to estimate liver fat content. This guidance has the aim of helping the reader in understanding how they work and interpret the results. Confounding factors are discussed and a standardized protocol for measurement acquisition is suggested to mitigate them. The recommendations were based on published studies and experts' opinion but were not formally graded because the body of evidence remained low at the time of drafting this document.

Hepatic steatosis: Qualitative and quantitative sonographic assessment in comparison to histology

Introduction

Globally, B-mode ultrasound is the most common modality used for the diagnosis of hepatic steatosis. We aimed to assess the correlation between qualitative liver ultrasound parameters, attenuation imaging (ATI) and histopathology-diagnosed steatosis grade obtained from liver biopsy. Our secondary aim was to examine the interobserver variability of qualitative ultrasound features.

Methods

A retrospective cohort study was performed which included adult patients (age ≥ 18 years) who had same-day liver ultrasound, ATI and liver biopsy for grading hepatic steatosis severity between 2018 and 2022. The qualitative US features for hepatic steatosis were independently scored by three radiologists and interobserver variability was examined. Histologic steatosis grade, ATI and qualitative ultrasound parameters were compared.

Results

Ninety patients were included; 67% female with a median age of 54 (IQR 39-65) years. The radiologist's overall impression had the highest correlation (very strongly correlated) with histologic steatosis grade (r = 0.82, P < 0.001). ATI coefficient and all qualitative ultrasound B-mode features except for liver echotexture and focal fat sparing were strongly correlated with histologic steatosis grade (r ≥ 0.70, P < 0.001). Most qualitative ultrasound features had good agreement between observers (Kappa statistic 0.61-1.0, P < 0.001), (Kendall coefficient 0.92, P < 0.001).

Conclusion

The examined qualitative ultrasound parameters and ATI had good-excellent performance for diagnosing clinically significant hepatic steatosis; however, the radiologist's overall impression had the best correlation with histologic steatosis grade. Our findings suggest an ongoing role for qualitative liver ultrasound assessment of hepatic steatosis despite the emergence of newer quantitative measures.

Methodology exploration and reproducibility evaluation of TAI and TSI for quantitative ultrasound assessment of hepatic steatosis

BACKGROUND AND AIM

New quantitative ultrasound techniques can be used to quantify hepatic steatosis, including tissue attenuation imaging (TAI), tissue scatter -distribution imaging (TSI), and the hepatorenal index (HRI). However, the measurement norms and the effects of fasting on these measurements remain unclear. The present study performed a methodological exploration and investigated the reliability of these measurements.

METHODS

In total, 103 participants were prospectively recruited for ultrasonography and magnetic resonance imaging (MRI) scans. For the TAI and TSI data, the upper (2 cm), middle (4 cm) and lower (6 cm) areas determined according to the depth of the region of interest from the liver capsule, were sampled three times. Correlation analyses were performed to compare the measurements of TAI, TSI, and HRI with the controlled attenuation parameter (CAP) or MRI-proton density fat fraction (MRI-PDFF). Intra- and inter-operator repeatability was assessed using intraclass correlation coefficients. The effects of fasting on these measurements were then compared.

RESULTS

The TAI and TSI measurements obtained from the upper and middle depths exhibited stronger correlations with the CAP measurements than those obtained from the lower depth. Specifically, the mean TAI had a significant positive correlation with MRI-PDFF (r = 0.753, P < 0.0001). TAI and TSI measurements exhibited excellent intra- (0.933 and 0.925, respectively) and inter- (0.896 and 0.766, respectively) examiner reliability. However, the correlation between HRI and CAP measurements was only 0.281, with no significant correlation with MRI-PDFF, and intra- and inter-examiner reproducibility of 0.458 and 0.343, respectively. Fasting did not affect these measurements.

CONCLUSIONS

TAI and TSI measurements demonstrated good intra- and interobserver reliability and correlated well with CAP and MRI-PDFF measurements. However, in practice-based clinical applications, the sampling depth should be controlled within 2-4 cm of the hepatic capsule; no fasting is required before the examination.