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Purpose: Steatotic liver disease (SLD) has become the most common cause of chronic liver disease. Nevertheless, the non-invasive quantitative diagnosis of steatosis is still lacking in clinical practice. This study aimed to evaluate the reproducibility of the new parameter for steatosis quantification named ultrasound-derived fat fraction (UDFF). Materials and methods: The UDFF values were independently executed by two operators in two periods. In the process, repeated measurements of the same patient were performed by the same operator under different conditions (liver segments, respiration, positions, and dietary). Finally, the results of some subjects (28) were compared with the MRI-derived proton density fat fraction (PDFF). The concordance analysis was mainly achieved by the intraclass correlation coefficient (ICC) and Bland–Altman. Results: One hundred-five participants were included in the study. UDFF had good reliability in measuring the adult liver (ICCintra-observer = 0.96, ICCinter-observer = 0.94). Meanwhile, the ICC of the two operators increased over time. The variable measurement states did not influence the UDFF values on the surface, but they affected the coefficient of variation (Cov) of the results. Segment 8 (S8), end-expiratory, supine, and fasting images had the most minor variability. On the other hand, the UDFF value of S8 displayed satisfied consistency with PDFF (mean difference, −0.24 ± 1.44), and the results of both S5 (mean difference: −0.56 ± 3.95) and S8 (mean difference: 0.73 ± 1.87) agreed well with the whole-liver PDFF. Conclusion: UDFF measurements had good reproducibility. Furthermore, the state of S8, end-expiration, supine, and fasting might be the more stable measurement approach. Critical relevance statement: UDFF is the quantitative ultrasound parameter of hepatic steatosis and has good reproducibility. It can show more robust performance under specific measurement conditions (S8, end-expiratory, supine, and fasting). Trial registration: The research protocol was registered at the Chinese Clinical Trial Registry on October 9, 2023 (http://www.chictr.org.cn/). The registration number is ChiCTR 2300076457. Key Points: There is a lack of non-invasive quantitative measurement options for hepatic steatosis. UDFF demonstrated excellent reproducibility in measuring hepatic steatosis. S8, end-expiratory, supine, and fasting may be the more stable measuring condition. Training could improve the operators' measurement stability. Variable measurement state affects the repeatability of the UDFF values (Cov). [ABSTRACT FROM AUTHOR]

Abstract Purpose Steatotic liver disease (SLD) has become the most common cause of chronic liver disease. Nevertheless, the non-invasive quantitative diagnosis of steatosis is still lacking in clinical practice. This study aimed to evaluate the reproducibility of the new parameter for steatosis quantification named ultrasound-derived fat fraction (UDFF). Materials and methods The UDFF values were independently executed by two operators in two periods. In the process, repeated measurements of the same patient were performed by the same operator under different conditions (liver segments, respiration, positions, and dietary). Finally, the results of some subjects (28) were compared with the MRI-derived proton density fat fraction (PDFF). The concordance analysis was mainly achieved by the intraclass correlation coefficient (ICC) and Bland–Altman. Results One hundred-five participants were included in the study. UDFF had good reliability in measuring the adult liver (ICCintra-observer = 0.96, ICCinter-observer = 0.94). Meanwhile, the ICC of the two operators increased over time. The variable measurement states did not influence the UDFF values on the surface, but they affected the coefficient of variation (Cov) of the results. Segment 8 (S8), end-expiratory, supine, and fasting images had the most minor variability. On the other hand, the UDFF value of S8 displayed satisfied consistency with PDFF (mean difference, −0.24 ± 1.44), and the results of both S5 (mean difference: −0.56 ± 3.95) and S8 (mean difference: 0.73 ± 1.87) agreed well with the whole-liver PDFF. Conclusion UDFF measurements had good reproducibility. Furthermore, the state of S8, end-expiration, supine, and fasting might be the more stable measurement approach. Critical relevance statement UDFF is the quantitative ultrasound parameter of hepatic steatosis and has good reproducibility. It can show more robust performance under specific measurement conditions (S8, end-expiratory, supine, and fasting). Trial registration The research protocol was registered at the Chinese Clinical Trial Registry on October 9, 2023 ( http://www.chictr.org.cn/ ). The registration number is ChiCTR 2300076457. Key Points There is a lack of non-invasive quantitative measurement options for hepatic steatosis. UDFF demonstrated excellent reproducibility in measuring hepatic steatosis. S8, end-expiratory, supine, and fasting may be the more stable measuring condition. Training could improve the operators’ measurement stability. Variable measurement state affects the repeatability of the UDFF values (Cov). Graphical Abstract

Background: Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in children. To avoid limitations of liver biopsy and MRI, quantitative ultrasound has become a research focus. Ultrasound-derived fat fraction (UDFF) is based on a combination of backscatter coefficient and attenuation parameter. Objective: The objectives of the study were to determine (1) agreement between UDFF/MRI proton density fat fraction (MR-PDFF) and (2) whether BMI and age are predictive for UDFF. Materials and methods: This cross-sectional prospective study included a convenience sample of 46 children referred for clinically indicated abdominal MRI. MR-PDFF and five acquisitions of UDFF were collected. Intraclass correlation coefficient (ICC) and Bland-Altman analysis were used to assess agreement between MR-PDFF and UDFF. Receiver operating characteristic curves were calculated for UDFF prediction of liver steatosis (MR-PDFF ≥ 6%). Multivariable regression was performed to assess BMI and age as predictors for UDFF. Results: Twenty-two participants were male, 24 were female, and the mean age was 14 ± 3 (range: 7-18) years. Thirty-six out of 46 participants had normal liver fat fraction <6%, and 10/46 had liver steatosis. UDFF was positively associated with MR-PDFF (ICC 0.92 (95% CI, 0.89-0.96). The mean bias between UDFF and MR-PDFF was 0.64% (95% LOA, -5.3-6.6%). AUROC of UDFF for steatosis was of 0.95 (95% CI, 0.89-0.99). UDFF cutoff of 6% had a sensitivity of 90% (95% CI, 55-99%) and a specificity of 94% (95% CI, 81-0.99%). BMI was an independent predictor of UDFF (correlation: 0.55 (95% CI, 0.35-0.95)). Conclusions: UDFF shows strong agreement with MR-PDFF in children. A UDFF cutoff of 6% provides good sensitivity and specificity for detection of MR-PDFF of ≥ 6%. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this study was to demonstrate the clinical feasibility of an integrated reference phantom method for quantitative ultrasound by creating an ultrasound‐derived fat fraction (UDFF) tool. This tool was evaluated with respect to its diagnostic performance as a biomarker for assessing histologic hepatic steatosis and its agreement with the magnetic resonance imaging (MRI) proton density fat fraction (PDFF). Methods: Adults (n = 101) with known or suspected nonalcoholic fatty liver disease consented to participate in this prospective cross‐sectional study. All patients underwent MRI‐PDFF and ultrasound scans, whereas 90 underwent liver biopsy. A linear least‐squares analysis used the attenuation coefficient and backscatter coefficient to create the UDFF model for predicting MRI‐PDFF. Results: The area under the receiver operating characteristic curve values were 0.94 (95% confidence interval [CI], 0.85–0.98) for histologic steatosis grade 0 (n = 6) versus 1 or higher (n = 84), 0.88 (95% CI, 0.8–0.94) for grade 1 or lower (n = 45) versus 2 or higher (n = 45), and 0.83 (95% CI, 0.73–0.9) for grade 2 or lower (n = 78) versus 3 (n = 12). The Pearson correlation coefficient between UDFF and PDFF was ρ = 0.87 with 95% limits of agreement of ±8.5%. Additionally, the diagnosis of steatosis, defined as MRI‐PDFF higher than 5% and 10%, had area under the receiver operating characteristic curve values of 0.97 (95% CI, 0.93–0.99) and 0.95 (95% CI, 0.9–0.98), respectively. The body mass index was not correlated with either UDFF or PDFF. Conclusions: An on‐system, integrated UDFF tool provides a simple, noninvasive, accessible, low‐cost, and commercially viable clinical tool for quantifying the hepatic fat fraction with a high degree of agreement with histologic biopsy or the MRI‐PDFF biomarker. [ABSTRACT FROM AUTHOR]