Quantitative Ultrasound Radiofrequency Data Analysis for the Assessment of Hepatic Steatosis in Nonalcoholic Fatty Liver Disease Using Magnetic Resonance Imaging Proton Density Fat Fraction as the Reference Standard

Abstract

Objective To investigate the diagnostic performance of quantitative ultrasound (US) parameters for the assessment of hepatic steatosis in patients with nonalcoholic fatty liver disease (NAFLD) using magnetic resonance imaging proton density fat fraction (MRI-PDFF) as the reference standard. Materials and Methods In this single-center prospective study, 120 patients with clinically suspected NAFLD were enrolled between March 2019 and January 2020. The participants underwent US examination for radiofrequency (RF) data acquisition and chemical shift-encoded liver MRI for PDFF measurement. Using the RF data analysis, the attenuation coefficient (AC) based on tissue attenuation imaging (TAI) (AC-TAI) and scatter-distribution coefficient (SC) based on tissue scatter-distribution imaging (TSI) (SC-TSI) were measured. The correlations between the quantitative US parameters (AC and SC) and MRI-PDFF were evaluated using Pearson correlation coefficients. The diagnostic performance of AC-TAI and SC-TSI for detecting hepatic fat contents of ≥ 5% (MRI-PDFF ≥ 5%) and ≥ 10% (MRI-PDFF ≥ 10%) were assessed using receiver operating characteristic (ROC) analysis. The significant clinical or imaging factors associated with AC and SC were analyzed using linear regression analysis. Results The participants were classified based on MRI-PDFF: < 5% (n = 38), 5–10% (n = 23), and ≥ 10% (n = 59). AC-TAI and SC-TSI were significantly correlated with MRI-PDFF ( r = 0.659 and 0.727, p < 0.001 for both). For detecting hepatic fat contents of ≥ 5% and ≥ 10%, the areas under the ROC curves of AC-TAI were 0.861 (95% confidence interval [CI]: 0.786–0.918) and 0.835 (95% CI: 0.757–0.897), and those of SC-TSI were 0.964 (95% CI: 0.913–0.989) and 0.935 (95% CI: 0.875–0.972), respectively. Multivariable linear regression analysis showed that MRI-PDFF was an independent determinant of AC-TAI and SC-TSI. Conclusion AC-TAI and SC-TSI derived from quantitative US RF data analysis yielded a good correlation with MRI-PDFF and provided good performance for detecting hepatic steatosis and assessing its severity in NAFLD.

Quantitative Evaluation of Hepatic Steatosis Using Advanced Imaging Techniques: Focusing on New Quantitative Ultrasound Techniques

“…In several recent studies, AC calculated with these techniques generally showed a good diagnostic performance for hepatic steatosis, with liver biopsy or MRI-PDFF as reference standards (AUROC, 0.76–0.98 with different techniques, reference standards, and target degree of steatosis) [ 20 21 22 91 92 93 94 95 96 97 98 ]. In addition, AC has been shown to correlate well with the degree of steatosis evaluated by histology or MRI-PDFF ( r = 0.47–0.78) [ 20 21 22 91 92 93 94 95 96 97 ]. The detailed results of the studies on ATI, UGAP, ATT, and TAI are summarized in Table 3 and Figure 4B .…”

“…However, AC can also theoretically be affected by fibrosis, although the effect of fibrosis is less pronounced than steatosis [ 20 ]. Different results have been reported on the effects of hepatic fibrosis on AC measured with ATI, UGAP, or TAI [ 92 93 97 100 101 ]. Therefore, further studies and standardization of AC, with consideration of concurrent hepatic fibrosis, are warranted.…”

Assessment of the inter-platform reproducibility of ultrasound attenuation examination in nonalcoholic fatty liver disease

“…However, the 95% LOAs of the absolute difference in mean AC values were quite large and were thought to be clinically unacceptable (-0.22 to 0.11 for ATI and TAI, from -0.17 to 0.18 for ATI and UGAP, and from -0.08 to 0.20 for TAI and UGAP). Many previous studies have reported the high diagnostic performance of ultrasound attenuation imaging for diagnosing hepatic steatosis and grading severity, but there is a wide variation in optimal cut-off values for diagnosing hepatic steatosis reported in each study, ranging from 0.59 to 0.69 for ATI (0.59 to 0.69 for MRI-PDFF as reference standard; 0.64 to 0.69 for histopathology as reference standard); for 0.88 for TAI (MRI-PDFF as reference standard), and from 0.53 to 0.60 for UGAP (0.53 for histopathology as reference standard; 0.60 for MRI-PDFF as reference standard [20][21][22]30]. Moreover, the optimal cut-off values for discriminating each grade of hepatic steatosis (mild [S1], moderate [S2], and severe [S3]) showed minimal gaps (range, 0.02-0.10) [20][21][22]30].…”

“…Many previous studies have reported the high diagnostic performance of ultrasound attenuation imaging for diagnosing hepatic steatosis and grading severity, but there is a wide variation in optimal cut-off values for diagnosing hepatic steatosis reported in each study, ranging from 0.59 to 0.69 for ATI (0.59 to 0.69 for MRI-PDFF as reference standard; 0.64 to 0.69 for histopathology as reference standard); for 0.88 for TAI (MRI-PDFF as reference standard), and from 0.53 to 0.60 for UGAP (0.53 for histopathology as reference standard; 0.60 for MRI-PDFF as reference standard [20][21][22]30]. Moreover, the optimal cut-off values for discriminating each grade of hepatic steatosis (mild [S1], moderate [S2], and severe [S3]) showed minimal gaps (range, 0.02-0.10) [20][21][22]30]. Considering the minimal gradual change in AC values according to the grade of hepatic steatosis, the calculated 95% LOAs of the absolute difference in AC values in our study were thought to be too large to be clinically acceptable.…”

“…Recently, several ultrasound manufacturers have developed B-mode ultrasound-guided attenuation imaging techniques, and compared to conventional ultrasound, attenuation imaging is less operator dependent and still has the inherent advantages of ultrasound, such as wide availability, realtime capability, and relatively low cost [19]. In previous studies, ultrasound attenuation imaging techniques have demonstrated good accuracy in the diagnosis and grading of hepatic steatosis with excellent inter-examiner or intra-examiner reliability [20][21][22][23].…”