Attenuation coefficient (ATT) measurement for liver fat quantification in chronic liver disease

Compensated Advanced Chronic Liver Disease and Steatosis in Patients with Type 2 Diabetes as Assessed through Shear Wave Measurements and Attenuation Measurements

Patients with type 2 diabetes (T2D) are at risk of developing metabolic dysfunction-associated steatotic liver disease (MASLD). We investigated the prevalence of compensated advanced chronic liver disease (cACLD) and steatosis in patients with T2D using the new non-invasive diagnostic methods of shear wave measurements (SWMs) and attenuation (ATT) measurements in comparison with those of vibration-controlled transient elastography (VCTE) and the controlled attenuation parameter (CAP), which served as the reference methods. Among 214 T2D patients, steatosis at any grade and cACLD were revealed in 134 (62.6%) and 19 (8.9%) patients, respectively. SWMs showed a high correlation with VCTE (Spearman's ρ = 0.641), whereas SWMs produced lower (mean of -0.7 kPa) liver stiffness measurements (LSMs) overall. At a LSM of >11.0 kPa (Youden), SWMs had an AUROC of 0.951 that was used to diagnose cACLD (defined as a LSM of >15 kPa through VCTE) with 84.2% sensitivity and 96.4% specificity. The performance of ATT measurements in diagnosing liver steatosis at any grade (defined as the CAP of ≥274 dB/m) was suboptimal (AUROC of 0.744 at the ATT measurement cut-off of >0.63 dB/cm/MHz (Youden) with 59% sensitivity and 81.2% specificity). In conclusion, the prevalence of liver steatosis and previously unrecognized cACLD in patients with T2D is high and SWMs appear to be a reliable diagnostic method for this purpose, whereas further investigation is needed to optimize the diagnostic performance of ATT measurements.

Elastography of the Liver in Wilson's Disease

Staging of liver fibrosis is of special significance in Wilson's disease as it determines the patient's prognosis and treatment. Histopathological examination is a standard method for fibrosis assessment; however, non-invasive methods like transient elastography and share wave elastography are believed to be reliable and repetitive and are expected to replace liver biopsy in Wilson's disease. This article presents a short description of available elastography techniques and the results of the most recent studies on elastography of the liver in patients with Wilson's disease.

Non-invasive evaluation of liver steatosis with imaging modalities: New techniques and applications

In the world, nonalcoholic fatty liver disease (NAFLD) accounts for majority of diffuse hepatic diseases. Notably, substantial liver fat accumulation can trigger and accelerate hepatic fibrosis, thus contributing to disease progression. Moreover, the presence of NAFLD not only puts adverse influences for liver but is also associated with an increased risk of type 2 diabetes and cardiovascular diseases. Therefore, early detection and quantified measurement of hepatic fat content are of great importance. Liver biopsy is currently the most accurate method for the evaluation of hepatic steatosis. However, liver biopsy has several limitations, namely, its invasiveness, sampling error, high cost and moderate intraobserver and interobserver reproducibility. Recently, various quantitative imaging techniques have been developed for the diagnosis and quantified measurement of hepatic fat content, including ultrasound- or magnetic resonance-based methods. These quantitative imaging techniques can provide objective continuous metrics associated with liver fat content and be recorded for comparison when patients receive check-ups to evaluate changes in liver fat content, which is useful for longitudinal follow-up. In this review, we introduce several imaging techniques and describe their diagnostic performance for the diagnosis and quantified measurement of hepatic fat content.

Application of attenuation coefficient in the assessment of hepatic involvement in children and adolescents with Wilson's disease

BACKGROUND

To investigate whether the attenuation coefficient (ATT) can be used as a noninvasive index to assess liver involvement in children and adolescents with Wilson's disease (WD).

METHODS

Children and adolescents diagnosed with WD were retrospectively collected from the First Affiliated Hospital of the Anhui University of Traditional Chinese Medicine between May 2022 and August 2022. The findings on ATT, Shear Wave Measurement (SWM), AST to platelet ratio index (APRI), and fibrosis 4 (FIB-4) score were obtained. The liver involvement of WD was classified into 3 groups based on serum levels of collagen type IV (CIV), hyaluronic acid (HA), laminin (LN) and precollagen type III N-terminal peptide (PIIINP): (1) Group1 (n = 25), no abnormalities in CIV, HA, LN and PIIINP; (2) Group2 (n = 19), elevation of 1 or 2 indexes in CIV, HA, LN, and PIIINP; Group3 (n = 18), elevation of 3 or 4 indicators in CIV, HA, LN, and PIIINP. The levels of ATT, SWM, APRI and FIB-4 were compared between the 3 groups; and correlation of ATT with SWM and triglyceride (TG) was performed using Spearman's correlation analysis. The Receiver operating characteristic (ROC) curve was used to analyze the diagnostic efficacy of ATT alone and its combination with SWM, APRI, and FIB-4 in children and adolescents with WD.

RESULTS

A total of 62 children and adolescents with WD were retrospectively retrieved. ATT levels were significantly different in intergroup comparisons (P < 0.001). The ROC curve showed that the area under the curve (AUC) for the diagnosis of hepatic steatosis using ATT was 0.714, 0.712 and 0.867 in Group 1 versus Group 2, Group 2 versus Group 3, and Group 1 versus Group 3, respectively; the sensitivity for the diagnosis of hepatic steatosis in Group 1 versus Group 2 was 89.47% with the cutoff value of ATT of 0.73 dB/cm/MHz. No significant correlation found between ATT and TG (ρ = 0.154, P = 0.231). Compared to ATT alone, the combination of ATT with APRI and FIB-4 or the combination of ATT with SWM, APRI, and FIB-4 showed a better diagnostic efficacy in Group 1 versus Group 2 (both P = 0.038).

CONCLUSION

ATT could be used as a non-invasive index for the evaluation of liver steatosis in children and adolescents with WD, with a good clinical applicative value. Furthermore, ATT in combination with APRI, FIB-4, and SWM might have better diagnostic efficacy than ATT alone.

Ultrasound Methods for the Assessment of Liver Steatosis: A Critical Appraisal

The prevalence of the non-alcoholic fatty liver disease has reached major proportions, being estimated to affect one-quarter of the global population. The reference techniques, which include liver biopsy and the magnetic resonance imaging proton density fat fraction, have objective practical and financial limitations to their routine use in the detection and quantification of liver steatosis. Therefore, there has been a rising necessity for the development of new inexpensive, widely applicable and reliable non-invasive diagnostic tools. The controlled attenuation parameter has been considered the point-of-care technique for the assessment of liver steatosis for a long period of time. Recently, many ultrasound (US) system manufacturers have developed proprietary software solutions for the quantification of liver steatosis. Some of these methods have already been extensively tested with very good performance results reported, while others are still under evaluation. This manuscript reviews the currently available US-based methods for diagnosing and grading liver steatosis, including their classification and performance results, with an appraisal of the importance of this armamentarium in daily clinical practice.

Intra-individual Comparisons of the Ultrasound-Guided Attenuation Parameter and the Magnetic Resonance Imaging-Based Proton Density Fat Fraction Using Bias and Precision Statistics

Ultrasound-based techniques using the attenuation coefficient, including the ultrasound-guided attenuation parameter (UGAP), have been developed for the quantification of hepatic steatosis. The magnetic resonance imaging-based proton density fat fraction (MRI-PDFF) is considered to be more accurate than liver biopsy for liver fat quantification. The aim of this study was to perform intra-individual comparisons of UGAP and MRI-PDFF for determining hepatic steatosis grade. The study enrolled 309 patients who underwent UGAP and MRI-PDFF measurements. Bland-Altman analysis was conducted after transforming MRI-PDFF values to a normal distribution and converted to a common set of units using linear regression analysis for differing scales. The expected limits of agreement (LOA) was defined as the square root of the sum of the squares of UGAP and MRI-PDFF precision. A Bland-Altman plot revealed that the bias and upper and lower LOAs (ULOA and LLOA) were -0.0047, 0.1160 and -0.1255, respectively. The percentage difference indicated that the mean, ULOA and LLOA were -1.1434%, 18.1723% and -20.4590%, respectively. The calculated expected LOA was 18.5449%, and 283 of 309 patients (91.6%) had a percentage difference within 18.5449%. Bland-Altman analysis revealed that UGAP and MRI-PDFF were interchangeable within a clinically acceptable range.

Feasibility of Ultrasound Attenuation Imaging for Assessing Pediatric Hepatic Steatosis

We investigated the feasibility of ultrasound attenuation imaging (ATI) for assessing pediatric hepatic steatosis. A total of 111 children and adolescents who underwent liver ultrasonography with ATI for suspected hepatic steatosis were included. Participants were classified into the normal, mild, or moderate−severe fatty liver group according to grayscale US findings. Associations between clinical factors, magnetic resonance imaging proton density fat fraction, steatosis stage and ATI values were evaluated. To determine the cutoff values of ATI for staging hepatic steatosis, areas under the curve (AUCs) were analyzed. Factors that could cause measurement failure with ATI were assessed. Of 111 participants, 88 had successful measurement results. Median ATI values were significantly increased according to steatosis stage (p < 0.001). Body mass index (BMI) was a significant factor for increased ATI values (p = 0.047). To differentiate fatty liver from normal liver, a cutoff value of 0.59 dB/cm/MHz could be used with an AUC value of 0.853. To differentiate moderate to severe fatty liver from mild fatty liver, a cutoff value of 0.69 dB/cm/MHz could be used with an AUC value up to 0.91. ATI can be used in children as an effective ultrasonography technique for quantifying and staging pediatric hepatic steatosis.

Attenuation Coefficient Measurement Using a High-Frequency (2-9 MHz) Convex Transducer for Children Including Fatty Liver

We evaluated the measurement feasibility and diagnostic ability of an ultrasound-guided attenuation parameter (UGAP) using a high-frequency convex transducer in children. This retrospective study included all consecutive children who underwent abdomen ultrasonography from July to December 2020. Attenuation coefficients (ACs) of the liver were measured using both 1- to 6-MHz (AC1-6) and 2- to 9-MHz (AC2-9) probes of the LOGIQ E10 system (GE Healthcare). t-Tests and Pearson's or partial correlation analyses were performed, and AC cutoff values for diagnosing fatty liver were obtained from receiver operating characteristic curve analyses. Finally, 118 patients (M:F = 83:35, mean age: 10.2 ± 4.1 y) were evaluated, and the measurement success rate was 98.3% (116/118) for AC2-9. AC1-6 was available in children with a liver depth greater than 9 cm. The ratio of interquartile range to median of the AC2-9 was lower than that of the AC1-6 (4.3 vs. 8.5, p < 0.001). In the normal group (n = 41), the AC2-9 values were not associated with age, sex or body mass index. For the evaluation of steatosis, the AC2-9 values exhibited a positive correlation with the MR fat fraction (coefficient = 0.498, p < 0.001). The cutoff value of 0.699 dB/cm/MHz had 90.2% sensitivity and 100% specificity for diagnosing fatty liver. In conclusion, measurements of ACs using a high-frequency convex transducer are feasible even in small children, with lower measurement variability. The AC2-9 values also had good diagnostic performance for pediatric fatty liver.

Noninvasive assessment of liver fibrosis and its clinical significance in nonalcoholic fatty liver disease

Liver fibrosis is the most important prognostic factor in patients with nonalcoholic fatty liver disease (NAFLD). Several noninvasive markers for fibrosis, including blood-based markers and imaging based-markers have been developed. Indirect fibrosis markers (e.g., fibrosis-4 index and NAFLD fibrosis score) consist of standard laboratory data and clinical parameters. Given its availability and high negative predictive value for advanced fibrosis, these markers are suitable for screening at primary care. Blood-based fibrogenesis markers (enhanced liver fibrosis and N-terminal propeptide of type 3 collagen), ultrasound-based modalities (vibration-controlled transient elastography, point shear wave elastography [SWE], and two-dimensional SWE), and magnetic resonance elastography have high diagnostic accuracy for liver fibrosis and are suitable for diagnosing liver fibrosis at secondary care centers. Sequential use of these markers can increase diagnostic accuracy and reduce health care costs. Furthermore, combining noninvasive makers may assist in identifying candidates for pharmacological trials and reducing screening failure. Emerging data suggest that these noninvasive markers are associated with liver-related events (hepatocellular carcinoma and decompensation) and mortality. Furthermore, delta change in noninvasive markers over time is also associated with time-course change in fibrosis, liver-related event risk, and mortality risk. However, the association between liver fibrosis and cardiovascular disease (CVD) risk is still controversial. CVD risk may decrease in patients with decompensated liver disease and noninvasive markers may be useful for assessing CVD risk in these patients. Therefore, noninvasive markers may be utilized as measures of fibrosis as well as real-time prognostic tools, in place of liver biopsy.