The B-Mode Image-Guided Ultrasound Attenuation Parameter Accurately Detects Hepatic Steatosis in Chronic Liver Disease

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.

Steatosis grading consistency between controlled attenuation parameter and MRI-PDFF in monitoring metabolic associated fatty liver disease

Background

The consistency in steatosis grading between magnetic resonance imaging-based proton density fat fraction (MRI-PDFF) and controlled attenuation parameter (CAP) before and after treatment remains unclear. This study aimed to compare the diagnostic accuracy of steatosis grading between MRI-PDFF and CAP using liver biopsy as standard and to evaluate the value of monitoring changes in steatosis grading with CAP during follow-up utilizing MRI-PDFF as a reference.

Methods

Consecutive patients from a biopsy cohort and a randomized controlled trial were included in this study and classified into 3 groups (the biopsy, orlistat treatment, and routine treatment subgroups). Hepatic steatosis was measured via MRI-PDFF and CAP at baseline and at the 6th month; the accuracy and cutoffs were assessed in the liver biopsy cohort at baseline.

Results

A total of 209 consecutive patients were enrolled. MRI-PDFF and CAP showed comparable diagnostic accuracy for detecting pathological steatosis [⩾S1, area under the receiver operating characteristic curve (AUC) = 0.984 and 0.972, respectively]; in contrast, CAP presented significantly lower AUCs in grades S2-3 and S3 (0.820 and 0.815, respectively). The CAP values correlated well with the MRI-PDFF values at baseline and at the 6th month (r = 0.809 and 0.762, respectively, both p < 0.001), whereas a moderate correlation in their changes (r = 0.612 and 0.524 for moderate-severe and mild steatosis, respectively; both p < 0.001) was observed. The AUC of CAP change was obtained to predict MRI-PDFF changes of ⩾5% and ⩾10% (0.685 and 0.704, p < 0.001 and p = 0.001, respectively). The diagnostic agreement of steatosis grade changes between MRI-PDFF and CAP was weak (κ = 0.181, p = 0.001).

Conclusions

CAP has decreased value for the initial screening of moderate-severe steatosis and is limited in monitoring changes in steatosis during treatment. The confirmation of steatosis grading with MRI-PDFF remains necessary.

The ultrasound-guided attenuation parameter is useful in quantification of hepatic steatosis in non-alcoholic fatty liver disease

Aim

To determine the utility of the ultrasound‐guided attenuation parameter (UGAP) for quantifying hepatic steatosis in non‐alcoholic fatty liver disease (NAFLD).

Methods

Subjects were 84 patients with NAFLD (53 men, 31 women; mean age 54 [20–81] years) who underwent liver biopsy and ultrasonography using a GE LOGIQ E9 system and C1‐6 probe at our hospital between 2017 and 2020. B‐Mode imaging of segment V in the liver was acquired and echo attenuation was assessed using UGAP. Steatosis score (S0: <5%; S1: 5%–33%; S2: 34%–66%; S3: ≥67%) from liver specimens was compared with the attenuation coefficient (AC; dB/cm/MHz) using UGAP.

Results

Steatosis score was S0 for 9 patients, S1 for 40, S2 for 21, and S3 for 14. AC by steatosis score was 0.52 ± 0.07, 0.63 ± 0.07, 0.74 ± 0.06, and 0.78 ± 0.06 dB/cm/MHz for S0, S1, S2, and S3, respectively. AC by UGAP differed significantly between S0 and S1, S0 and S2, S0 and S3, S1 and S2, and S1 and S3 (all P < 0.01), demonstrating a significant increase with steatosis score. Receiver operating characteristic analysis showed good diagnostic performance of UGAP for patients with steatosis score ≥1, ≥2, and ≥3 (AUROC = 0.94, 0.95, and 0.88, respectively). Liver fat content (%) from liver specimens and AC (r = 0.81, P < 0.01) showed a significant positive correlation.

Conclusion

UGAP is useful for quantifying hepatic steatosis in patients with NAFLD.

Ultrasound-Based Quantification of Fibrosis and Steatosis with a New Software Considering Transient Elastography as Reference in Patients with Chronic Liver Diseases

The goal of this study was to evaluate the performance of two new ultrasound-based techniques (ShearWave PLUS elastography [2-D-SWE PLUS], SSp PLUS Imaging [SSp PLUS]) implemented on the Aixplorer Mach 30 ultrasound system (Supersonic Imagine, Aix-en-Provence, France) for the non-invasive assessment of liver steatosis and fibrosis, using transient elastography (TE) with the controlled attenuation parameter (CAP) as reference. This monocentric cross-sectional study included 133 consecutive adult patients with chronic hepatopathies. Liver stiffness and steatosis were evaluated in the same session using the techniques mentioned above. An excellent correlation was observed between liver stiffness measurements obtained with 2-D-SWE PLUS and TE (r = 0.92, p < 0.0001). The best cutoff value of 2-D-SWE PLUS for predicting F≥2 was 6.8 kPa; for F≥3, 8.4 kPa; and for F4, 11 kPa. With respect to steatosis evaluation, a strong negative correlation between CAP and SSp PLUS values (r = -0.70, p < 0.0001) was obtained. The best SSp PLUS cutoff value for predicting steatosis was 1537 m/s.

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.

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

Liver fat is one of the main clinical features in chronic liver disease, and the number of fatty liver patients is increasing as the prevalence of obesity and metabolic syndrome increases globally. Noninvasive and quantitative assessment of liver fat content was made possible by recent technological advances. Attenuation coefficient (ATT) measurement is a noninvasive and quantitative liver fat measurement method used in clinical practice. The ATT value is significantly associated with histological steatosis grade. The diagnostic accuracy of ATT for histological steatosis grade is equivalent to controlled attenuation parameter (CAP), and ATT has a lower measurement failure rate than CAP because ATT can be measured on a B-mode image with the exact location of the region of interest. Furthermore, ATT measurement has high interobserver reproducibility. Since ATT measurement and other ultrasound-based modalities for liver fat quantification are easy to perform and inexpensive, these modalities are suitable for point-of-care and screening. Although emerging data suggest that quantitative liver fat content and its changes over time may be associated with disease progression in nonalcoholic fatty liver disease, the association between ATT and disease progression has not been evaluated yet. Therefore, further investigation and validation studies are necessary to strengthen the clinical significance of ATT measurement in chronic liver disease.

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.

Quantification of Liver Fibrosis, Steatosis, and Viscosity Using Multiparametric Ultrasound in Patients with Non-Alcoholic Liver Disease: A "Real-Life" Cohort Study

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. This study aimed to evaluate the performance of four ultrasound-based techniques for the non-invasive multiparametric (MPUS) assessment of liver fibrosis (LF), steatosis (HS), and inflammation in patients with NAFLD. We included 215 consecutive adult patients with NAFLD (mean age: 54.9 ± 11.7; 54.5% were male), in whom LF, HS, and viscosity were evaluated in the same session using four new ultrasound-based techniques embedded on the Aixplorer MACH 30 system: ShearWave Elastography (2D-SWE.PLUS), Sound Speed Plane-wave UltraSound (SSp.PLUS), Attenuation Plane-wave UltraSound (Att.PLUS), and Viscosity Plane-wave UltraSound (Vi.PLUS). Transient Elastography (TE) with Controlled Attenuation Parameter (CAP) (FibroScan) were considered as control. All elastographic measurements were performed according to guidelines. Valid liver stiffness measurements (LSM) were obtained in 98.6% of patients by TE, in 95.8% of patients by 2D-SWE.PLUS/Vi.PLUS, and in 98.1% of patients by Att.PLUS/SSp.PLUS, respectively. Therefore, 204 subjects were included in the final analysis. A strong correlation between LSMs by 2D-SWE.PLUS and TE (r = 0.89) was found. The best 2D-SWE.PLUS cut-off value for the presence of significant fibrosis (F ≥ 2) was 7 kPa. Regarding steatosis, SSp.PLUS correlated better than Att.PLUS with CAP values: (r = −0.74) vs. (r = 0.45). The best SSp.PLUS cut-off value for predicting the presence of significant steatosis was 1524 m/s. The multivariate regression analysis showed that Vi.PLUS values were associated with BMI and LSM by 2D-SWE.PLUS. In conclusion, MPUS was useful for assessing fibrosis, steatosis, and inflammation in a single examination in patients with NAFLD.

Two-dimensional shear wave elastography and ultrasound-guided attenuation parameter for progressive non-alcoholic steatohepatitis

Background and aims

We investigated the usefulness of combining two-dimensional shear wave elastography and the ultrasound-guided attenuation parameter for assessing the risk of progressive non-alcoholic steatohepatitis, defined as non-alcoholic steatohepatitis with a non-alcoholic fatty liver disease activity score of ≥4 and a fibrosis stage of ≥2.

Methods

This prospective study included 202 patients with non-alcoholic fatty liver disease who underwent two-dimensional shear wave elastography, ultrasound-guided attenuation parameter, vibration-controlled transient elastography, the controlled attenuation parameter, and liver biopsy on the same day. Patients were grouped according to liver stiffness measurement using two-dimensional shear wave elastography and the attenuation coefficient, assessed using the ultrasound-guided attenuation parameter: A, low liver stiffness measurement/low attenuation coefficient; B, low liver stiffness measurement/high attenuation coefficient; C, high liver stiffness measurement/low attenuation coefficient; and D, high liver stiffness measurement/high attenuation coefficient.

Results

Two-dimensional shear wave elastography and vibration-controlled transient elastography had equivalent diagnostic performance for fibrosis. The areas under the curve of the ultrasound-guided attenuation parameter for identifying steatosis grades ≥S1, ≥S2, and S3 were 0.89, 0.91, and 0.92, respectively, which were significantly better than those of the controlled attenuation parameter (P<0.05). The percentages of progressive non-alcoholic steatohepatitis in Groups A, B, C, and D were 0.0%, 7.7%, 35.7%, and 50.0%, respectively (P<0.001). The prediction model was established as logit (p) = 0.5414 × liver stiffness measurement (kPa) + 7.791 × attenuation coefficient (dB/cm/MHz)—8.401, with area under the receiver operating characteristic curve, sensitivity, and specificity values of 0.832, 80.9%, and 74.6%, respectively; there was no significant difference from the FibroScan-aspartate aminotransferase score.

Conclusion

Combined assessment by two-dimensional shear wave elastography and the ultrasound-guided attenuation parameter is useful for risk stratification of progressive non-alcoholic steatohepatitis and may be convenient for evaluating the necessity of specialist referral and liver biopsy.

Clinical Feasibility of Quantitative Ultrasound Imaging for Suspected Hepatic Steatosis: Intra- and Inter-examiner Reliability and Correlation with Controlled Attenuation Parameter

This study was aimed at investigating the clinical feasibility of quantitative ultrasound (QUS) imaging in the evaluation of suspected hepatic steatosis through assessment of the reliability of measurements and its correlation with the controlled attenuation parameter (CAP). This retrospective study included 117 patients who underwent liver B-mode ultrasound (US) with QUS imaging with a clinical US machine (RS85, Samsung Medison, Seoul, Korea) and CAP measurements between December 2019 and March 2020. For QUS examination, tissue attenuation imaging (TAI) and tissue scatter-distribution imaging (TSI) parameters were obtained. Intra- and inter-examiner reliability were assessed using intra-class correlation coefficients (ICCs), and QUS imaging parameters were correlated with CAP measurements using Spearman's correlation analysis. TAI and TSI revealed excellent intra- and inter-examiner reliability with ICCs of 0.994 and 0.975 and 0.991 and 0.947, respectively. Both TAI and TSI were significantly positively correlated with CAP values. QUS imaging provided good intra-and inter-observer reliability and correlated well with CAP in assessing suspected hepatic steatosis.

Analysis of liver steatosis analysis and controlled attenuation parameter for grading liver steatosis in patients with chronic hepatitis B

Background

Chronic hepatitis B is the most common chronic liver disease in China. For patients with chronic hepatitis B, steatosis increases the risk of cirrhosis and hepatocellular carcinoma. This study aimed to analyze and compare the clinical value of a newly developed ultrasound attenuation parameter, liver steatosis analysis (LiSA), acquired by Hepatus (Mindray, China), and controlled attenuation parameter (CAP), a widely used ultrasound attenuation parameter acquired by FibroScan (Echosens, France), for grading liver steatosis in patients with chronic hepatitis B infection.

Methods

A total of 203 patients were divided into two groups according to liver fat content validated by liver biopsy: group 1 (liver fat content <10%) and group 2 (liver fat content ≥10%). All patients underwent LiSA and CAP examinations. Receiver operating characteristic (ROC) curves were calculated for the two ultrasound attenuation tools.

Results

Both LiSA and CAP successfully discriminated between patients in group 1 and group 2. ROC curves showed that both tools had good diagnostic ability (AUC: >0.7) for steatosis ≥10%, and the performance of LiSA was significantly better than CAP (AUC: 0.859 vs. 0.801, P=0.048). Using optimal cut-off points, LiSA had specificity and sensitivity of 96.23% and 76.08%, respectively, for the diagnosis of steatosis ≥10%, compared to 91.53% and 72.10%, respectively, for CAP.

Conclusions

LiSA and CAP are extremely efficient tools for assessing liver steatosis, even at a low grade. Both parameters are non-invasive, inexpensive, and easy to use, and can provide immediate results with high sensitivity.

Assessment of hepatic steatosis by controlled attenuation parameter using the M and XL probes: an individual patient data meta-analysis

BACKGROUND

Diagnostic tools for liver disease can now include estimation of the grade of hepatic steatosis (S0 to S3). Controlled attenuation parameter (CAP) is a non-invasive method for assessing hepatic steatosis that has become available for patients who are obese (FibroScan XL probe), but a consensus has not yet been reached regarding cutoffs and its diagnostic performance. We aimed to assess diagnostic properties and identify relevant covariates with use of an individual patient data meta-analysis.

METHODS

We did an individual patient data meta-analysis, in which we searched PubMed and Web of Science for studies published from database inception until April 30, 2019. Studies reporting original biopsy-controlled data of CAP for non-invasive grading of steatosis were eligible. Probe recommendation was based on automated selection, manual assessment of skin-to-liver-capsule distance, and a body-mass index (BMI) criterion. Receiver operating characteristic methods and mixed models were used to assess diagnostic properties and covariates. Patients with non-alcoholic fatty liver disease (NAFLD) were analysed separately because they are the predominant patient group when using the XL probe. This study is registered with PROSPERO, CRD42018099284.

FINDINGS

16 studies reported histology-controlled CAP including the XL probe, and individual data from 13 papers and 2346 patients were included. Patients with a mean age of 46·5 years (SD 14·5) were recruited from 20 centres in nine countries. 2283 patients had data for BMI; 673 (29%) were normal weight (BMI <25 kg/m²), 530 (23%) were overweight (BMI ≥25 to <30 kg/m²), and 1080 (47%) were obese (BMI ≥30 kg/m²). 1277 (54%) patients had NAFLD, 474 (20%) had viral hepatitis, 285 (12%) had alcohol-associated liver disease, and 310 (13%) had other liver disease aetiologies. The XL probe was recommended in 1050 patients, 930 (89%) of whom had NAFLD; among the patients with NAFLD, the areas under the curve were 0·819 (95% CI 0·769-0·869) for S0 versus S1 to S3 and 0·754 (0·720-0·787) for S0 to S1 versus S2 to S3. CAP values were independently affected by aetiology, diabetes, BMI, aspartate aminotransferase, and sex. Optimal cutoffs differed substantially across aetiologies. Risk of bias according to QUADAS-2 was low.

INTERPRETATION

CAP cutoffs varied according to cause, and can effectively recognise significant steatosis in patients with viral hepatitis. CAP cannot grade steatosis in patients with NAFLD adequately, but its value in a NAFLD screening setting needs to be studied, ideally with methods beyond the traditional histological reference standard.

FUNDING

The German Federal Ministry of Education and Research and Echosens.

Liver Fat Quantification by Ultrasound in Children: A Prospective Study

BACKGROUND. Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in children in certain regions and is rising in prevalence with increasing obesity. Accurate noninvasive imaging methods for diagnosing and quantifying liver fat are needed to guide NAFLD management. OBJECTIVE. The purpose of this article is to evaluate four ultrasound technologies for quantitative assessment of liver fat content in children using MRI proton density fat fraction (PDFF) as a reference standard. METHODS. This prospective study enrolled children who underwent clinical abdominal MRI without general anesthesia between November 2018 and July 2019. Patients underwent investigational liver ultrasound within a day of 1.5-T or 3-T MRI. Acquired ultrasound radiofrequency data were processed offline to compute the acoustic attenuation coefficient, hepatorenal index (HRI), Nakagami parameter, and shear-wave elastography (SWE) parameters (elasticity, viscosity, and dispersion). Ultrasound parameters were compared with MRI PDFF obtained using a multiecho sequence. A second observer independently performed offline attenuation coefficient and HRI measurements in all patients. RESULTS. A total of 48 patients were enrolled: 22 girls, 26 boys; mean age of 13 years (range, 7-17 years); mean body mass index (weight in kilograms divided by the square of height in meters) of 22.25 (range, 14.5-48.1). A total of 21% (10/48) had steatosis (PDFF ≥ 5%). PDFF was correlated with attenuation coefficient (r = 0.76; 95% CI, 0.60-0.86; p < .001), HRI (r = 0.84; 95% CI, 0.74-0.91; p < .001), and Nakagami parameter (r = 0.55, 95% CI, 0.32-0.72, p < .001), but not SWE parameters (r = 0.05-0.25; p > .05). In patients with no, mild, moderate, and severe steatosis according to PDFF, the mean (± SD) attenuation coefficient was 0.48 ± 0.08, 0.54 ± 0.03, 0.57 ± 0.04, and 0.86 ± 0.07 dB/cm/MHz, respectively, and the mean HRI was 1.28 ± 0.30, 1.59 ± 0.23, 2.25 ± 0.04, and 3.06 ± 0.49, respectively. For the attenuation coefficient, the threshold of 0.54 dB/cm/MHz achieved a sensitivity of 80% and a specificity of 82% for steatosis, and 0.60 dB/cm/MHz achieved a sensitivity of 80% and a specificity of 98% for moderate steatosis. For HRI, the threshold of 1.48 achieved sensitivity of 90% and specificity of 76% for steatosis, and 2.11 achieved sensitivity of 100% and specificity of 100% for moderate steatosis. The interobserver concordance coefficient was 0.92 for attenuation coefficient and 0.91 for HRI. CONCLUSION. Attenuation coefficient and HRI accurately detected and quantified liver fat in this small sample of children. CLINICAL IMPACT. Quantitative ultrasound parameters may guide NAFLD diagnosis and management in children.

Quantitative assessment of liver steatosis using ultrasound controlled attenuation parameter (Echosens)

Controlled attenuation parameter (CAP) is the algorithm available on the FibroScan system (Echosens, France) for quantification of liver steatosis. It assesses the ultrasound beam attenuation, which is directly related to liver fat content. The inter-observer reproducibility of the technique is high, with a reported concordance correlation coefficient of 0.82. Specific quality criteria for CAP measurements are not clearly defined yet, and there are conflicting results in the literature. Using liver biopsy as the reference standard, several studies have assessed the CAP performance in grading liver steatosis, and have reported that values are not affected by liver fibrosis. The cutoff for detection of liver steatosis reported in the literature ranges from 222 decibels per meter (dB/m) in a cohort of patients with chronic hepatitis C to 294 dB/m in a meta-analysis of nonalcoholic fatty liver disease (NAFLD) patients. CAP has been used as a tool to noninvasively evaluate the prevalence of NAFLD in groups at risk or in the general population; however, it should be underscored that different CAP cutoffs for steatosis detection (S > 0) were used in different studies, and this limits the robustness of the findings. CAP, alone or combined with other noninvasive indices or biomarkers, has been proposed as a tool for assessing nonalcoholic steatohepatitis or as a noninvasive predictor of prognosis in patients with chronic liver disease. CAP is easy to perform and has become a point-of-care technique. However, there is a large overlap of values between consecutive grades of liver steatosis, and cutoffs are not clearly defined.

Basic concept and clinical applications of quantitative ultrasound (QUS) technologies

In the field of clinical ultrasound, the full digitalization of diagnostic equipment in the 2000s enabled the technological development of quantitative ultrasound (QUS), followed by multiple diagnostic technologies that have been put into practical use in recent years. In QUS, tissue characteristics are quantified and parameters are calculated by analyzing the radiofrequency (RF) echo signals returning to the transducer. However, the physical properties (and pathological level structure) of the biological tissues responsible for the imaging features and QUS parameters have not been sufficiently verified as there are various conditions for observing living tissue with ultrasound and inevitable discrepancies between theoretical and actual measurements. A major issue of QUS in clinical application is that the evaluation results depend on the acquisition conditions of the RF echo signal as the source of the image information, and also vary according to the model of the diagnostic device. In this paper, typical examples of QUS techniques for evaluating attenuation, speed of sound, amplitude envelope characteristics, and backscatter coefficient in living tissues are introduced. Exemplary basic research and clinical applications related to these technologies, and initiatives currently being undertaken to establish the QUS method as a true tissue characterization technology, are also discussed.

The Echogenic Liver: Steatosis and Beyond

ABSTRACT

Ultrasound is the most common modality used to evaluate the liver. An echogenic liver is defined as increased echogenicity of the liver parenchyma compared with the renal cortex. The prevalence of echogenic liver is approximately 13% to 20%. In most clinical settings, increased liver echogenicity is simply attributed to hepatic steatosis. It is important to recognize other hepatic and systemic diseases including cirrhosis, viral hepatitis, glycogen storage disease, and hemochromatosis that may also cause an echogenic liver and to identify the associated findings to distinguish them from hepatic steatosis.

Advances in ultrasound elastography for nonalcoholic fatty liver disease

The prevalence of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) has increased rapidly worldwide, making NAFLD/NASH an important global health problem from both a medical and socioeconomic standpoint. NAFLD is also regarded as a liver component of metabolic syndrome and is reported to be associated with the risk factors for metabolic syndrome. It has been suggested that NAFLD/NASH be recognized both as a liver-specific disease and as an early mediator of systemic diseases. Liver biopsy is recommended as the gold standard method for the diagnosis of NASH and for the staging of liver fibrosis in patients with NAFLD. However, because of its high cost, high risk, and high weightage as a healthcare resource, invasive liver biopsy is a poorly suited diagnostic test for such a highly prevalent condition. Therefore, the development of reliable noninvasive methods for the assessment of liver fibrosis has been sought to estimate the risk of progression of NASH to cirrhosis, estimate the risk of cardiovascular events, aid in the surveillance for HCC, and guide therapy in patients with NAFLD/NASH. In this review, we highlight the principles and recent advances in ultrasound elastography techniques (Real-time Tissue Elastography^®, vibration-controlled transient elastography, point shear wave elastography, and two-dimensional shear wave elastography) used to evaluate the liver fibrosis stage and steatosis grade in patients with NAFLD.

Quantitative ultrasound radiofrequency data analysis for the assessment of hepatic steatosis using the controlled attenuation parameter as a reference standard

Purpose

This study was aimed to investigate the value of quantitative ultrasound (US) parameters from radiofrequency (RF) data analysis for assessing hepatic steatosis, using controlled attenuation parameter (CAP)-based steatosis grades as the reference standard.

Methods

We analyzed 243 participants with both B-mode liver US with RF data acquisition and CAP measurements. On B-mode US images, hepatic steatosis was visually scored (0/1/2/3, none/mild/moderate/severe), and the hepatorenal index (HRI) was calculated. From the RF data analysis, the tissue scatter-distribution imaging parameter (TSI-p) and tissue attenuation imaging parameter (TAI-p) of the liver parenchyma were measured. US parameters were correlated with CAP-based steatosis grades (S0/1/2/3, none/mild/moderate/severe) and their diagnostic performance was evaluated using receiver operating characteristic (ROC) curve analysis. Multivariate linear regression analysis was performed to identify determinants of TSI-p and TAI-p.

Results

Participants were classified as having S0 (n=152), S1 (n=54), S2 (n=14), and S3 (n=23) on CAP measurements. TSI-p and TAI-p were significantly correlated with steatosis grades (ρ =0.593 and ρ=-0.617, P<0.001 for both). For predicting ≥S1, ≥S2, and S3, the areas under the ROC curves (AUCs) of TSI-p were 0.827/0.914/0.917; TAI-p, 0.844/0.914/0.909; visual scores, 0.659/0.778/0.794; and HRI, 0.629/0.751/0.759, respectively. TSI-p and TAI-p had significantly higher AUCs than did visual scores or HRI for ≥S1 or ≥S2 (P≤0.003). In the multivariate analysis, the transient elastography-based fibrosis grade (P=0.034) and steatosis grade (P<0.001) were independent determinants of TSI-p, while steatosis grade (P<0.001) was an independent determinant of TAI-p.

Conclusion

TSI-p and TAI-p derived from US RF data may be useful for detecting hepatic steatosis and assessing its severity.

Quantification of liver fat content with ultrasonographic attenuation measurement function: Correlation with unenhanced multidimensional computerized tomography

PURPOSE

To evaluate the efficacy of attenuation measurement function (ATT), a newly developed quantitative ultrasonography(US) method based on measurement of the attenuation coefficient, using unenhanced computerized tomography(CT) attenuation values as a reference standard, for the detection and measurement of hepatosteatosis.

MATERIAL AND METHODS

A total of 98 patients were analyzed. The diagnostic ability of ATT was evaluated using receiver operating characteristic (ROC) curve analysis, and the correlation between liver attenuation index (LAI), the liver-to-spleen attenuation ratio (CT^L/S), liver attenuation value (CT^L), and ATT was determined.

RESULTS

ATT is negatively correlated with LAI (r = -0.571, p < 0.001), CT^L/S (r = -0.532, p < 0.001), and mean CT^L (r = -0.50, p < 0.001). A significant difference was found between ATT values of patients with different grades of hepatosteatosis (p < 0.001). A significant difference was found between ATT values of patients with LAI < -10 and LAI > -10, CT^L < 40 and CT^L > 40, and CT^L/S < 1 and CT^L/S > 1 (p < 0.001). An ATT ≥ 0.665 showed a sensitivity of 100% and a specificity of 90% in diagnosing moderate-severe steatosis. The corresponding area under the ROC curve(AUROC) was 0.935. The intraclass correlation coefficient for the interobserver variability of ATT was 0.907 (95% CI, 0.85-0.95).

CONCLUSION

In conclusion, ATT values for evaluation of hepatosteatosis was closely correlated with the degree of hepatosteatosis and liver fat content. It can be used as a noninvasive method in the diagnosis and follow-up.

Screening for Liver Fibrosis and Steatosis in a Large Cohort of Patients with Type 2 Diabetes Using Vibration Controlled Transient Elastography and Controlled Attenuation Parameter in a Single-Center Real-Life Experience

BACKGROUND

Type 2 diabetes mellitus (T2DM), obesity, hyperlipidemia, and hypertension are considered risk factors for developing non-alcoholic fatty liver disease (NAFLD). This study aims to assess steatosis and fibrosis severity in a cohort of T2DM patients, using vibration controlled transient elastography (VCTE) and controlled attenuation parameter (CAP).

MATERIAL AND METHOD

We performed a prospective study in which, in each patient, we aimed for 10 valid CAP and liver stiffness measurements (LSM). To discriminate between fibrosis stages, we used the following VCTE cut-offs: F ≥ 2-8.2 kPa, F ≥ 3-9.7 kPa, and F4 - 13.6 kPa. To discriminate between steatosis stages, we used the following CAP cut-offs: S1 (mild) - 274 dB/m, S2 (moderate) - 290dB/m, S3 (severe) - 302dB/m.

RESULTS

During the study period, we screened 776 patients; 60.3% had severe steatosis, while 19.4% had advanced fibrosis. Female gender, BMI, waist circumference, elevated levels of AST, total cholesterol, triglycerides, blood glucose, and high LSM were associated with severe steatosis (all p-value < 0.05). BMI, waist circumference, elevated levels of AST, HbA1c, and CAP were associated with advanced fibrosis (all p-values < 0.05).

CONCLUSION

Higher BMI (obesity) comprises a higher risk of developing severe steatosis and fibrosis. Individualized screening strategies should be established for NAFLD according to different BMI.

Liver stiffness does not affect ultrasound-guided attenuation coefficient measurement in the evaluation of hepatic steatosis

AIM

Recently, a new method has been developed to diagnose hepatic steatosis with attenuation coefficients based on the ultrasound-guided attenuation parameter (UGAP). We investigated whether fibrosis identified by hepatic stiffness measurements based on magnetic resonance elastography (MRE) affects attenuation coefficient measurement using UGAP for the evaluation of hepatic steatosis.

METHODS

A total of 608 patients with chronic liver disease were analyzed. Correlations between magnetic resonance imaging-determined proton density fat fraction (PDFF) or MRE value and attenuation coefficients were evaluated. In addition, the interaction between hepatic fibrosis and the attenuation coefficient was analyzed.

RESULTS

The correlation coefficient (r) between PDFF values and attenuation coefficient values was 0.724, indicating a strong relationship. Conversely, the r between MRE values and attenuation coefficient values was -0.187, indicating almost no relationship. In the multiple regression assessment of the effect of PDFF and MRE on the attenuation coefficient based on UGAP, the P-values for PDFF, MRE, and PDFF × MRE were < 0.001, 0.277, and 0.903, respectively. In patients with non-alcoholic fatty liver disease (n = 169), the r between PDFF values and attenuation coefficient values was 0.695, indicating a moderate relationship. Conversely, the r between MRE values and attenuation coefficient values was -0.068, indicating almost no relationship. In the multiple regression assessment of the effect of PDFF and MRE on the attenuation coefficient based on UGAP, the P-values for PDFF, MRE, and PDFF × MRE were <0.001, 0.948, and 0.706, respectively.

CONCLUSION

UGAP-determined attenuation coefficient was weakly affected by liver stiffness, an indicator of hepatic fibrosis.

Hepatic steatosis assessment using ultrasound homodyned-K parametric imaging: the effects of estimators

BACKGROUND

The homodyned-K (HK) distribution is an important statistical model for describing ultrasound backscatter envelope statistics. HK parametric imaging has shown potential for characterizing hepatic steatosis. However, the feasibility of HK parametric imaging in assessing human hepatic steatosis in vivo remains unclear.

METHODS

In this paper, ultrasound HK μ parametric imaging was proposed for assessing human hepatic steatosis in vivo. Two recent estimators for the HK model, RSK (the level-curve method that uses the signal-to-noise ratio (SNR), skewness, and kurtosis based on the fractional moments of the envelope) and XU (the estimation method based on the first moment of the intensity and two log-moments, namely X- and U-statistics), were investigated. Liver donors (n=72) and patients (n=204) were recruited to evaluate hepatic fat fractions (HFFs) using magnetic resonance spectroscopy and to evaluate the stages of fatty liver disease (normal, mild, moderate, and severe) using liver biopsy with histopathology. Livers were scanned using a 3-MHz ultrasound to construct μ _RSK and μ _XU images to correlate with HFF analyses and fatty liver stages. The μ _RSK and μ _XU parametric images were constructed using the sliding window technique with the window side length (WSL) =1-9 pulse lengths (PLs). The diagnostic values of the μ _RSK and μ _XU parametric imaging methods were evaluated using receiver operating characteristic (ROC) curves.

RESULTS

For the 72 participants in Group A, the μ _RSK parametric imaging with WSL =2-9 PLs exhibited similar correlation with log₁₀(HFF), and the μ _RSK parametric imaging with WSL = 3 PLs had the highest correlation with log₁₀(HFF) (r=0.592); the μ _XU parametric imaging with WSL =1-9 PLs exhibited similar correlation with log₁₀(HFF), and the μ _XU parametric imaging with WSL =1 PL had the highest correlation with log₁₀(HFF) (r=0.628). For the 204 patients in Group B, the areas under the ROC (AUROCs) obtained using μ _RSK for fatty stages ≥ mild (AUROC₁), ≥ moderate (AUROC₂), and ≥ severe (AUROC₃) were (AUROC₁, AUROC₂, AUROC₃) = (0.56, 0.57, 0.53), (0.68, 0.72, 0.75), (0.73, 0.78, 0.80), (0.74, 0.77, 0.79), (0.74, 0.78, 0.79), (0.75, 0.80, 0.82), (0.74, 0.77, 0.83), (0.74, 0.78, 0.84) and (0.73, 0.76, 0.83) for WSL =1, 2, 3, 4, 5, 6, 7, 8 and 9 PLs, respectively. The AUROCs obtained using μ _XU for fatty stages ≥ mild, ≥ moderate, and ≥ severe were (AUROC₁, AUROC₂, AUROC₃) = (0.75, 0.83, 0.81), (0.74, 0.80, 0.80), (0.76, 0.82, 0.82), (0.74, 0.80, 0.84), (0.76, 0.80, 0.83), (0.75, 0.80, 0.84), (0.75, 0.79, 0.85), (0.75, 0.80, 0.85) and (0.73, 0.77, 0.83) for WSL = 1, 2, 3, 4, 5, 6, 7, 8 and 9 PLs, respectively.

CONCLUSIONS

Both the μ _RSK and μ _XU parametric images are feasible for evaluating human hepatic steatosis. The WSL exhibits little impact on the diagnosing performance of the μ _RSK and μ _XU parametric imaging. The μ _XU parametric imaging provided improved performance compared to the μ _RSK parametric imaging in characterizing human hepatic steatosis in vivo.

Ultrasound-based techniques for the diagnosis of liver steatosis

Non-alcoholic fatty liver disease (NAFLD) is the leading cause of diffuse liver disease. An accurate estimate of the fat in the liver is important in the diagnostic work-up of patients with NAFLD because the degree of liver steatosis is linked to the metabolic syndrome and the cardiovascular risk. Ultrasound (US) B-mode imaging allows to subjectively estimate the fatty infiltration in the liver; however, it has a low performance for the detection of mild steatosis. Quantitative US is based on the analysis of the radiofrequency echoes detected by an US system, and it allows to calculate a backscatter coefficient or an attenuation coefficient or the sound speed. The estimation of the backscatter coefficient is rather cumbersome and requires the use of a phantom for addressing all sources of variability. Controlled attenuation parameter (CAP) available on the FibroScan^® system (Echosens, France) measures the attenuation of the US beam. CAP is accurate in grading fatty infiltration-even though there is an overlap between consecutive grade of liver steatosis-and the values are not influenced by liver fibrosis. Several US manufacturers are developing or have already developed software for quantifying the attenuation of the US beam. Preliminary results show that proprietary technologies implemented in US systems seem more accurate than CAP for grading liver steatosis. Another available method for quantifying liver steatosis is based on the computation of the sound speed and the initial results appear promising.

The combination of fatty liver and increased gamma-glutamyl transpeptidase levels as a risk factor for atherosclerotic plaque development in apparently healthy people

Background/aim

To elucidate how the combination of fatty liver and increased serum gamma-glutamyl transpeptidase (GGT) levels influences atherosclerotic plaque development in apparently healthy people.

Materials and methods

The study population included people who had received an annual health checkup for more than 7 years and had no evidence of carotid plaque at baseline. We investigated the risk factors for carotid plaque occurrence using the Cox proportional hazards model.

Results

A total of 107 people (76 men and 31 women; median age, 49 years) were enrolled. At baseline, fatty liver and a serum GGT level ≥50 U/L were observed in 13 and 38 people, respectively. During a median follow-up period of 13.3 years, carotid plaques appeared in 34 people. Multivariate analysis revealed that the combination of fatty liver and a serum GGT level ≥50 U/L was the only significant risk factor for carotid plaque occurrence (age- and sex-adjusted hazard ratio: 5.55; 95% confidence interval 1.70–18.14; P = 0.005).

Conclusion

The combination of fatty liver and increased serum GGT levels raises the risk for atherosclerotic plaque development in apparently healthy people.

A New Method to Quantify Concentration of Microbubbles in Attenuating Media Using Bubble Destruction Curve Analysis of the Contrast-Enhanced Ultrasound

It is known that the microbubbles of Sonazoid are accumulated in the liver parenchyma due to the phagocytosis of Kupffer cells in the sinusoid. Because this phagocytic function decreases due to the progression of fibrosis in chronic liver disease, the deterioration of the liver function may be quantified by measuring the concentration of the accumulated Sonazoid microbubbles. In this article, a new method to quantify the concentration of microbubbles accumulated in attenuating media is proposed. This method utilizes the contrast-enhanced imaging with high mechanical index, measures the depth of the bubble destruction for each frame and analyze the shape of the destruction curve to estimate the concentration of the bubbles. A phantom experiment was performed with various concentrations of the contrast agent Sonazoid solution as well as various attenuation coefficients of the viscous media. Because of the theoretical model proposed, the estimated attenuation indexes, related to the concentration of Sonazoid microbubbles, were independent of the background attenuation of the propagating medium. The result suggest it has a potential to quantify Sonazoid concentration in the liver parenchyma more precisely against different liver attenuation conditions.

A critical appraisal of the use of ultrasound in hepatic steatosis

Introduction: Nonalcoholic fatty liver disease (NAFLD) spans steatosis through nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). NAFLD carries an increased risk of cardio-metabolic and liver-related events accounting for a substantial economic burden. Given that the natural history of NAFLD is critically dependent on the stage of fibrosis, non-invasively identifying the subgroup of patients at a higher risk of progressive disease is key. Areas covered: This review highlights the recent developments in the use of ultrasound-based techniques in NAFLD and their performance in predicting metabolic derangements, cardiovascular risk, and progression of liver disease, notably including diagnosis of fibrosing NASH, identification, and treatment of HCC. Expert opinion: Our ability to identify NAFLD patients and to estimate steatofibrosis with various ultrasound-based techniques has undergone tremendous progress over the last few years. However, it is more difficult to capture the inflammatory component of NASH with such ultrasound-assisted techniques. Moreover, semi-quantitative, quantitative, elastographic, and contrast-enhanced ultrasound techniques are increasingly being appreciated and made available but not all such techniques will gain success in the clinical and research area. Therefore, further research will precisely define the role of the most innovative ultrasonographic techniques, while reducing costs and increasing feasibility.

Prospective Evaluation of Hepatic Steatosis Using Ultrasound Attenuation Imaging in Patients with Chronic Liver Disease with Magnetic Resonance Imaging Proton Density Fat Fraction as the Reference Standard

The purpose of our study was to investigate the diagnostic performance of 2-D ultrasound attenuation imaging (ATI) for the assessment of hepatic steatosis in patients with chronic liver disease using magnetic resonance imaging proton density fat fraction (MRI-PDFF) as the reference standard. We prospectively analyzed 87 patients with chronic liver disease who had reliable measurements at both ATI and MRI-PDFF. For the detection of hepatic steatosis of MRI-PDFF ≥5% and MRI-PDFF ≥10%, ATI measurements yielded areas under the receiver operating characteristic curve of 0.76 and 0.88, respectively (95% confidence intervals: 0.66-0.85 and 0.79-0.94). Attenuation coefficients at ATI were moderately correlated with MRI-PDFF (ρ = 0.66). In conclusion, attenuation coefficients at ultrasound ATI were well correlated with MRI-PDFF and, thus, may provide good diagnostic performance in the assessment of hepatic steatosis, making these coefficients a promising tool for the non-invasive assessment and quantification of hepatic steatosis.

Multiphysics modeling toward enhanced guidance in hepatic microwave ablation: a preliminary framework

We compare a surface-driven, model-based deformation correction method to a clinically relevant rigid registration approach within the application of image-guided microwave ablation for the purpose of demonstrating improved localization and antenna placement in a deformable hepatic phantom. Furthermore, we present preliminary computational modeling of microwave ablation integrated within the navigational environment to lay the groundwork for a more comprehensive procedural planning and guidance framework. To achieve this, we employ a simple, retrospective model of microwave ablation after registration, which allows a preliminary evaluation of the combined therapeutic and navigational framework. When driving registrations with full organ surface data (i.e., as could be available in a percutaneous procedure suite), the deformation correction method improved average ablation antenna registration error by 58.9% compared to rigid registration (i.e., 2.5 ± 1.1    mm , 5.6 ± 2.3    mm of average target error for corrected and rigid registration, respectively) and on average improved volumetric overlap between the modeled and ground-truth ablation zones from 67.0 ± 11.8 % to 85.6 ± 5.0 % for rigid and corrected, respectively. Furthermore, when using sparse-surface data (i.e., as is available in an open surgical procedure), the deformation correction improved registration error by 38.3% and volumetric overlap from 64.8 ± 12.4 % to 77.1 ± 8.0 % for rigid and corrected, respectively. We demonstrate, in an initial phantom experiment, enhanced navigation in image-guided hepatic ablation procedures and identify a clear multiphysics pathway toward a more comprehensive thermal dose planning and deformation-corrected guidance framework.

Hepatic Steatosis Assessment Using Quantitative Ultrasound Parametric Imaging Based on Backscatter Envelope Statistics

Hepatic steatosis is a key manifestation of non-alcoholic fatty liver disease (NAFLD). Early detection of hepatic steatosis is of critical importance. Currently, liver biopsy is the clinical golden standard for hepatic steatosis assessment. However, liver biopsy is invasive and associated with sampling errors. Ultrasound has been recommended as a first-line diagnostic test for the management of NAFLD. However, B-mode ultrasound is qualitative and can be affected by factors including image post-processing parameters. Quantitative ultrasound (QUS) aims to extract quantified acoustic parameters from the ultrasound backscattered signals for ultrasound tissue characterization and can be a complement to conventional B-mode ultrasound. QUS envelope statistics techniques, both statistical model-based and non-model-based, have shown potential for hepatic steatosis characterization. However, a state-of-the-art review of hepatic steatosis assessment using envelope statistics techniques is still lacking. In this paper, envelope statistics-based QUS parametric imaging techniques for characterizing hepatic steatosis are reviewed and discussed. The reviewed ultrasound envelope statistics parametric imaging techniques include acoustic structure quantification imaging, ultrasound Nakagami imaging, homodyned-K imaging, kurtosis imaging, and entropy imaging. Future developments are suggested.

Resection for Klatskin tumors: technical complexities and results

Klatskin's tumors, actually-redefined as perihilar cholangiocarcinoma (phCCA) do represent 50-70% of all CCAs and develop in a context of chronic inflammation and cholestasis of bile ducts. Surgical resection provides the only chance of cure for this disease but is technically challenging because of the complex, intimate and variable relationship between biliary and vascular structures at this location. Five years survival rates range between 25-45% (median 27-58 months) in case of R0 resection and 0-23% (median 12-21 months) in case of R1 resection respectively. It should be noted that the major costs of high radicality are represented by relative high morbidity and mortality rates (i.e., 20-66% and 0-9% respectively). Considering the fact that radical resection may represent the only curative treatment of phCCA, we focused our review on surgical planning and techniques that may improve resectability rates and outcomes for locally advanced phCCA. The surgical treatment of phCCA can be successful when following aspects have been fulfilled: (I) accurate preoperative diagnostic aimed to identify the tumor in all its details (localization and extension) and to study all the risk factors influencing a posthepatectomy liver failure (PHLF): i.e., liver volume, liver function, liver quality, haemodynamics and patient characteristics; (II) High end surgical skills taking in consideration the local extension of the tumor and the vascular invasion which usually require an extended hepatic resection and often a vascular resection; (III) adequate postoperative management aimed to avoid major complications (i.e., PHLF and biliary complications). These are technically challenging operations and must be performed in a high volume centres by hepato-biliary-pancreas (HBP)-surgeons with experience in microsurgical vascular techniques.