Ultrasound Attenuation Imaging Research Articles

Comparison of Ultrasound Attenuation Imaging Using a Linear versus a Conventional Convex Probe: A Volunteer Study.

The study aimed to investigate the feasibility of attenuation imaging (ATI) measurements using a linear probe on healthy volunteers and compare measurements with the conventional convex probe. Attenuation imaging measurements of the liver tissue were taken using ultrasound with a convex and a linear probe in 33 volunteers by two examining doctors, and the measurements were repeated 4-5 weeks later by one of them. The ATI values for the linear probe were in the range of the values for the convex probe for both examiners. Measurements did not change significantly for 32 out of 33 volunteers after 4-5 weeks when using the linear probe. The size of the region of interest (ROI) only impacted the ATI values for the convex probe; it did not affect the values taken with the linear probe. Healthy volunteers were measured, and their attenuation values were compared to those from a convex probe, commonly used in steatosis evaluation. When both probes were positioned in the same liver area, they showed good agreement in attenuation values, though depth significantly affected the measurements, with both probes providing different values at different depths. The study's results aligned with previous research using the same system. Operator A and B's results were compared, demonstrating similar ranges of values for both probes. The linear probe has been demonstrated to allow for superficial measurements and attain ATI values in line with that of the convex probe in the liver.

Confounders of Ultrasound Attenuation Imaging in a Linear Probe Using the Canon Aplio i800 System: A Phantom Study.

There have been studies showing attenuation imaging (ATI) with ultrasound as an approach to diagnose liver diseases such as steatosis or cirrhosis. So far, this technique has only been used on a convex probe. The goal of the study was to investigate the feasibility of ATI measurements using the linear array on a canon Aplio i800 scanner on certified phantoms. Three certified liver tissue attenuation phantoms were measured in five different positions using a linear probe. The effects of positioning and depth were explored and compared. The values were compared to the certified expected value for each phantom as well as the different measurement values for each measurement position. The ATI measurements on phantoms showed significant effect for the different probe positions and region of interest (ROI) depths. Values taken in the center with the probe perpendicular to the phantom were closest to certified values. Median values at 2.5-4.5 cm depth for phantoms 1 and 2 and 0.5-2.5 cm for phantom 3 were comparable with certified values. Measurements taken at a depth greater than 6 cm in any position were the least representative of the certified values (p-value < 0.01) and had the widest range throughout the different sessions. ATI measurements can be performed with the linear probe in phantoms; however, careful consideration should be given to depth dependency, as it can significantly affect measurement values. Remaining measurements at various depths within the 0.5-6.0 cm range showed deviation from the certified values of approximately 25%.

Ultrasound Attenuation Imaging vs MRI-PDFF, Echogenicity and Liver Function for Assessing Degree of Steatosis in NAFLD and Non-NAFLD Patients.

Nonalcoholic fatty liver disease (NAFLD) is a primary cause of parenchymal liver disease globally. There are currently several methods available to test the degree of steatosis in NAFLD patients, but all have drawbacks that limit their use.The objective of this study is to determine if a new technique, ultrasound (US) attenuation imaging (ATI), correlates with magnetic resonance proton density fat fraction imaging and hepatic echogenicity as seen on gray scale US imaging.Fifty-four patients were recruited at the University of Washington Medical Center from individuals who had already been scheduled for hepatic US or magnetic resonance imaging (MRI). All participants then underwent both hepatic MRI proton density fat fraction and US. Ultrasound images were then evaluated using ATI with 2 observers who individually determined relative grayscale echogenicity.Analysis showed positive correlation between ATI- and MRI-determined fat percentage in the case group (Spearman correlation: 0.50; P = 0.015). Furthermore, participants with NAFLD tended to have a higher ATI than controls (median: 0.70 vs 0.54 dB/cm/MHz; P < 0.001).This study demonstrates that US ATI combined with grayscale imaging is an effective way of assessing the degree of steatosis in patients with moderate to severe NAFLD.

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

To evaluate the performance of attenuation imaging (ATI) based on ultrasound for detection of hepatic steatosis in patients with nonalcoholic fatty liver disease (NAFLD). This prospective study was approved by our institutional review board (B2021-092R). Written informed consent was obtained from all patients. This study included 60 patients who had clinical suspicion of NAFLD and were referred for liver biopsy after ATI and controlled attenuation parameter (CAP) examinations between September 2020 and December 2021. The histologic hepatic steatosis was graded. The area under curve (AUC) analysis was performed. The success rate of the ATI examination was 100%. The intraobserver reproducibility of ATI was 0.981. The AUCs of ATI for detecting ≥S1, ≥S2, and S3 were 0.968 (cut-off value of 0.671dB/cm/MHz), 0.911 (cut-off value of 0.726dB/cm/MHz), and 0.766 (cut-off value of 0.757dB/cm/MHz), respectively. The AUCs of CAP for detecting ≥S1, ≥S2, and S3 were 0.916 (cut-off value of 258.5dB/m), 0.872 (cut-off value of 300.0dB/m), and 0.807 (cut-off value of 315.0dB/m), respectively. The diagnostic values showed no significant difference between ATI and CAP in detecting ≥S1, ≥S2, and S3 (P=.281, P=.254, and P=.330, respectively). The ATI had significant correlations with high-density lipoprotein cholesterol (P<.001), and with triglycerides (P=.015). ATI showed good feasibility and diagnostic performance in the detection of varying degrees of hepatic steatosis in NAFLD patients.

Application of ultrasound attenuation imaging and shear wave elastography in the diagnosis of metabolic fatty liver disease

ABSTRACT This study aimed to investigate the application of ultrasound attenuation imaging (ATI) and shear wave elastography (SWE) in the examination of patients with metabolism-related fatty liver disease (MAFLD). A total of 210 patients were retrospectively selected and divided into MAFLD group (n=84) and no MAFLD group (n=126). ROC curve was used to analyze the diagnostic efficacy of ATI value and SWE value for MAFLD. The MAFLD groups were divided into mild group (n=39), moderate group (n=28) and severe group (n=17). Spearman correlation was used to analyze the relationship between ATI values, SWE values and the severity of MAFLD. Waist circumference, BMI, ALT, AST, TG, CHOL, ATI and SWE in MAFLD group were higher than those in non-MAFLD group (P<0.05). ROC analysis showed that the AUC of ATI value in the diagnosis of MAFLD was 0.837 and the sensitivity, specificity and cutoff values were 83.46%, 70.35% and 0.63 dB/cm/MHZ. Waist circumference and BMI were significantly lower in the mild MAFLD group than in the moderate MAFLD group (P<0.05) and ALT, AST, TG, CHOL, ATI and SWE levels gradually increased with the severity of MAFLD (P<0.05). Correlation analysis showed that ATI was positively correlated with MAFLD severity (r=0.553, P<0.001, 95% CI=0.384~0.686) and SWE was significantly positively correlated with MAFLD severity (r=0.606, P<0.001, 95% CI=0.450~0.726). Both ATI and SWE are effective in the diagnosis and evaluation of MAFLD, but ATI is more effective in the diagnosis and SWE.

Different Ultrasound Shear Wave Elastography Techniques as Novel Imaging-Based Approaches for Quantitative Evaluation of Hepatic Steatosis—Preliminary Findings

Modern ultrasound (US) shear-wave dispersion (SWD) and attenuation imaging (ATI) can be used to quantify changes in the viscosity and signal attenuation of the liver parenchyma, which are altered in hepatic steatosis. We aimed to evaluate modern shear-wave elastography (SWE), SWD and ATI for the assessment of hepatic steatosis. We retrospectively analyzed the US data of 15 patients who underwent liver USs and MRIs for the evaluation of parenchymal disease/liver lesions. The USs were performed using a multifrequency convex probe (1-8 MHz). The quantitative US measurements for the SWE (m/s/kPa), the SWD (kPa-m/s/kHz) and the ATI (dB/cm/MHz) were acquired after the mean value of five regions of interest (ROIs) was calculated. The liver MRI (3T) quantification of hepatic steatosis was performed by acquiring proton density fat fraction (PDFF) mapping sequences and placing five ROIs in artifact-free areas of the PDFF scan, measuring the fat-signal fraction. We correlated the SWE, SWD and ATI measurements to the PDFF results. Three patients showed mild steatosis, one showed moderate steatosis and eleven showed no steatosis in the PDFF sequences. The calculated SWE cut-off (2.5 m/s, 20.4 kPa) value identified 3/4 of patients correctly (AUC = 0.73, p > 0.05). The SWD cut-off of 18.5 m/s/kHz, which had a significant correlation (r = 0.55, p = 0.034) with the PDFF results (AUC = 0.73), identified four patients correctly (p < 0.001). The ideal ATI (AUC = 0.53 (p < 0.05)) cut-off was 0.59 dB/cm/MHz, which showed a significantly good correlation with the PDFF results (p = 0.024). Hepatic steatosis can be accurately detected using all the US-elastography techniques applied in this study, although the SWD and the SWE showed to be more sensitive than the PDFF.

Quantitative evaluation of hepatic steatosis using attenuation imaging in a pediatric population: a prospective study.

Obesity and fatty-liver disease are increasingly common in children. Hepatic steatosis is becoming the most common cause of chronic liver disease during childhood. There is a need for noninvasive imaging methods that are easily accessible, safe and do not require sedation in the diagnosis and follow-up of the disease. In this study, the diagnostic role of ultrasound attenuation imaging (ATI) in the detection and staging of fatty liver in the pediatric age group was investigated using the magnetic resonance imaging(MRI)-proton density fat fraction as the reference. A total of 140 children with both ATI and MRI constituted the study group. Fatty liver was classified as mild (S1, defined as ≥ 5% steatosis), moderate (S2, defined as ≥ 10% steatosis), or severe (S3, defined as ≥ 20% steatosis) according to MRI-proton density fat fraction values. MRI studies were performed on the same 1.5-tesla (T) MR device without sedation and contrast agent. Ultrasound examinations were performed independently by two radiology residents blinded to the MRI data. While no steatosis was detected in half of the cases, S1 steatosis was found in 31 patients (22.1%), S2 in 29 patients (20.7%) and S3 in 10 patients (7.1%). A strong correlation was found between attenuation coefficient and MRI-proton density fat fraction values (r = 0.88, 95% CI 0.84-0.92; P < 0.001). The area under the receiver operating characteristic curve values of ATI were calculated as 0.944 for S > 0, 0.976 for S > 1 and 0.970 for S > 2, based on 0.65, 0.74 and 0.91dB/cm/MHz cut-off values, respectively. The intraclass correlation coefficient values for the inter-observer agreement and test-retest reproducibility were calculated as 0.90 and 0.91, respectively. Ultrasound attenuation imaging is a promising noninvasive method for the quantitative evaluation of fatty liver disease.

Ultrasound attenuation imaging: a reproducible alternative for the noninvasive quantitative assessment of hepatic steatosis in children.

Pediatric hepatic steatosis is a global public health concern, as an increasing number of children are affected by this condition. Liver biopsy is the gold standard diagnostic method; however, this procedure is invasive. Magnetic resonance imaging (MRI)-derived proton density fat fraction has been accepted as an alternative to biopsy. However, this method is limited by cost and availability. Ultrasound (US) attenuation imaging is an upcoming tool for noninvasive quantitative assessment of hepatic steatosis in children. A limited number of publications have focused on US attenuation imaging and the stages of hepatic steatosis in children. To analyze the usefulness of ultrasound attenuation imaging for the diagnosis and quantification of hepatic steatosis in children. Between July and November 2021, 174 patients were included and divided into two groups: group 1, patients with risk factors for steatosis (n = 147), and group 2, patients without risk factors for steatosis (n = 27). In all cases, age, sex, weight, body mass index (BMI), and BMI percentile were determined. B-mode US (two observers) and US attenuation imaging with attenuation coefficient acquisition (two independent sessions, two different observers) were performed in both groups. Steatosis was classified into four grades (0: absent, 1: mild, 2: moderate and 3: severe) using B-mode US. Attenuation coefficient acquisition was correlated with steatosis score according to Spearman's correlation. Attenuation coefficient acquisition measurements' interobserver agreement was assessed using intraclass correlation coefficients (ICC). All attenuation coefficient acquisition measurements were satisfactory without technical failures. The median values for group 1 for the first session were 0.64 (0.57-0.69) dB/cm/MHz and 0.64 (0.60-0.70) dB/cm/MHz for the second session. The median values for group 2 for the first session were 0.54 (0.51-0.56) dB/cm/MHz and 0.54 (0.51-0.56) dB/cm/MHz for the second. The average attenuation coefficient acquisition was 0.65 (0.59-0.69) dB/cm/MHz for group 1 and 0.54 (0.52-0.56) dB/cm/MHz for group 2. There was excellent interobserver agreement at 0.94 (95% CI 0.92-0.96). There was substantial agreement between both observers (κ = 0.77, with a P < 0.001). There was a positive correlation between ultrasound attenuation imaging and B-mode scores for both observers (r = 0.87, P < 0.001 for observer 1; r = 0.86, P < 0.001 for observer 2). Attenuation coefficient acquisition median values were significantly different for each steatosis grade (P < 0.001). In the assessment of steatosis by B-mode US, the agreement between the two observers was moderate (κ = 0.49 and κ = 0.55, respectively, with a P < 0.001 in both cases). US attenuation imaging is a promising tool for the diagnosis and follow-up of pediatric steatosis, which provides a more repeatable form of classification, especially at low levels of steatosis detectable in B-mode US.

Current aspects of multimodal ultrasound liver diagnostics using contrast-enhanced ultrasonography (CEUS), fat evaluation, fibrosis assessment, and perfusion analysis - An update.

Current ultrasound multifrequency probes allow both improved detail resolution and depth of penetration when examining the liver. Also, new developments in vascular diagnostics, elastography with fibrosis assessment, evaluation of possible steatosis, and parametric and time intensity curve (TIC) analysis of dynamic microvascularization of the liver with contrast-enhanced ultrasound sonography (CEUS) complement ultrasound-guided diagnostics. State-of-the-art high-resolution technology includes a high frame rate (HiFR) mode for CEUS, fast shear wave measurements with the sound touch quantify (STQ) mode, artifact-free flow detection using HR flow and glazing flow in combination with a special flow-adapted imaging (Ultra Micro Angiography, UMA) and additionally different assessments of possible fatty liver (UltraSound ATtenuation Imaging Technology, USAT). In 50 cases with focal liver lesions, a multimodal liver diagnosis was performed with a still new high-performance ultrasound system as part of the clarification of questions from the university liver consultation and tumor outpatient clinic.

The diagnostic value of novel ultrasound attenuation analysis in detecting liver steatosis identified by the controlled attenuation parameter: a diagnostic accuracy study.

Ultrasound attenuation analysis (USAT) is a type of novel ultrasound attenuation imaging that can be used to detect hepatic steatosis based on the attenuation coefficient. We sought to evaluate the diagnostic accuracy for assessing the severity of liver steatosis by USAT using the controlled attenuation parameter (CAP) as a reference in patients with non-alcoholic fatty liver diseases (NAFLD) and chronic hepatitis B (CHB) infections. In total, 326 consecutive subjects with or without chronic liver diseases were enrolled in this study who underwent CAP examination and USAT to evaluate hepatic steatosis from October 2022 to November 2022 at The Fourth Affiliated Hospital of Zhejiang University School of Medicine. Hepatic steatosis stage (S) was determined by CAP according to the following cut-off values recommended by the manufacturer: S ≥ S1 (≥11%, mild): 238 dB/m; S ≥ S2 (≥34%, moderate): 259 dB/m; and S ≥ S3 (≥67%, severe): 292 dB/m, and thus the optimal cut-off values for the USAT were acquired. The area under the receiver operating characteristic curves (AUROCs) for the categories of steatosis were used to measure the diagnostic accuracy of USAT. A total of 296 patients were recruited, including 101 (34.1%) patients with NAFLD, 172 (58.1%) with CHB and the remainder were healthy control subjects (7.8%). We used the CAP as the reference standard and found that the USAT increased gradually as the stage of steatosis increased (P<0.001). A strong positive correlation was found between USAT and CAP (r=0.787, P<0.001). In the whole population, the AUROCs of the USAT for S ≥ S1, S ≥ S2 and S ≥ 3 were 0.89, 0.90, and 0.90, respectively, and the cut-off values according to the Youden index for S ≥ S1, S ≥ S2, and S ≥ 3 were 0.62, 0.66, and 0.72 dB/cm/MHz, respectively. Our study showed that the USAT had a good ability to detect hepatic steatosis in NAFLD and CHB patients. USAT had a strong association with CAP and a good diagnostic capability in the detection of hepatic steatosis, which appears to be a promising tool for the non-invasive detection and quantification of hepatic steatosis.

Novel Ultrasound Liver Attenuation Imaging for Detection of Liver Steatosis: Comparison with MRI Based Imaging Methods with Liver Biopsy as A Reference Standard

Novel Ultrasound Liver Attenuation Imaging for Detection of Liver Steatosis: Comparison with MRI Based Imaging Methods with Liver Biopsy as A Reference Standard

Correlation of ultrasound attenuation imaging versus MRI proton density fat fraction in non-alcoholic fatty liver

Background: Attenuation Imaging (ATI) is a novel method for assessment of hepatic steatosis, based on ultrasound attenuation by calculating attenuation coefficient which increases in the fatty liver condition. The previous published data comparing ATI and Magnetic Resonance Proton Density Fat Fraction (MR-PDFF) has moderate to high correlation coefficient (r=0.66-0.81). However, fatty liver is commonly associated with obesity which may be an influencing factor of the ATI measurement. Objective: The purpose of this study was to evaluate diagnostic accuracy of ATI in non-alcoholic fatty liver disease (NAFLD) compared to MRI-PDFF Materials and Methods: The 62 non-alcoholic fatty liver disease (NAFLD) patients with available ATI, MRI-PDFF, and MRE examination, excluding cirrhosis, history of significant alcohol drinking, and chronic liver condition were retrospectively evaluated. Results: The correlation coefficient (r) of ATI vs MRI-PDFF were in good correlation (r = 0.63-0.69, p&lt;0.001). The inter-observer reliability of two observers was 100% with the Cohen kappa coefficient of 1.00 (p &lt; 0.001).Area under the receiver operating characteristics of ATI for diagnosis of steatosis grade &gt; 0 was 0.96 and for diagnosis of steatosis grade &gt; 1 was 0.83. Conclusions: ATI is a novel ultrasound method to quantify the degree of fat deposition with a good correlation to MRI-PDFF with high interobserver’ reliability. Obesity commonly associated with fatty liver may be an interfering factor of ATI measurement.

A Comparative Study of Ultrasound Attenuation Imaging, Controlled Attenuation Parameters, and Magnetic Resonance Spectroscopy for the Detection of Hepatic Steatosis.

To investigate the methodology and clinical application of ultrasound attenuation imaging (ATI) and comparative analyze the diagnostic performance of ATI and controlled attenuation parameters (CAP) for detecting and grading hepatic steatosis. A total of 159 patients with NAFLD were prospectively enrolled. CAP and ATI examinations were performed within a week before proton magnetic resonance spectroscopy (1 H-MRS). Ten liver attenuation coefficient (AC) measurements by ATI were obtained in each patient. The interclass correlation coefficients (ICCs) of the intraobserver consistencies and the ICCs between the median of the first two through the first nine measurements and all 10 measurements were calculated. The correlations between 1 H-MRS, CAP, biological data, and ATI were evaluated. The significant factors associated with ATI and the diagnostic performance of ATI and CAP for detecting hepatic steatosis was evaluated. The median value of AC for detecting hepatic steatosis was 0.831 dB/cm/MHz. For the intraobserver consistency of ATI, the ICC was 0.931. Compared with 10 measurements, a minimum of four ATI measurements was required. The correlation of AC with hepatic fat fraction (HFF) was significantly higher than that of CAP (0.603 vs 0.326, P=.0015). The HFF and triglyceride (TG) were the significant factors for the ATI. The area under the receiver operating characteristics (ROC) curves of ATI and CAP were 0.939 and 0.788 for detecting ≥10% hepatic steatosis; 0.751 and 0.572 for detecting >33% hepatic steatosis. The cutoff values of ATI and CAP were 0.697 dB/cm/MHz and 310 dB/m for detecting ≥10% hepatic steatosis; 0.793 dB/cm/MHz and 328 dB/m for detecting >33% hepatic steatosis. The sensitivity of ATI and CAP were 85.92% and 52.11% for detecting ≥10% hepatic steatosis; 87.50% and 82.14% for detecting >33% hepatic steatosis. The specificity of ATI and CAP were 94.12% and 100% for detecting ≥10% hepatic steatosis; 54.37% and 43.69% for detecting >33% hepatic steatosis. ATI technology showed excellent intraobserver consistency and the optimal minimum number of ATI measurements was 4. ATI is a promising noninvasive, quantitative and convenient tool for assessing hepatic steatosis.

Diagnosis of hepatic steatosis based on ultrasound attenuation imaging is not influenced by liver fibrosis.

Recently, a new technique using attenuation imaging (ATI) was developed to diagnose hepatic steatosis. The aim of this study was to investigate whether ATI for the evaluation of hepatic steatosis is influenced by liver fibrosis. A total of 328 patients with chronic liver disease were enrolled to study the associations between histological hepatic steatosis or liver fibrosis and ATI findings. The interaction between liver fibrosis and ATI was also analyzed. Median ATI values according to steatosis grade and fibrosis stage increased in line with the progression of liver steatosis (p<0.001) and fibrosis (p<0.05). However, in each steatosis grade, ATI values according to fibrosis stage were not significantly increased. In multiple regression analyses for assessment of the effect of their interaction, the p values for fibrosis stage, steatosis grade, and fibrosis stage×steatosis grade were 0.096, <0.001, and 0.077, respectively. Variance inflation factor values for fibrosis stage, steatosis grade, and fibrosis stage×steatosis grade were 1.079, 1.094, and 1.074, respectively. Attenuation imaging values are not influenced by liver fibrosis.

Feasibility of Ultrasound Attenuation Imaging for Assessing Pediatric Hepatic Steatosis.

Simple SummaryHepatic steatosis is associated with cardiovascular disease, diabetes mellitus, and liver cirrhosis. The increasing prevalence of hepatic steatosis among children has become a public health concern. Although liver biopsy is the gold standard for the diagnosis of hepatic steatosis, it has limited value because of invasiveness. Among imaging studies, ultrasonography is readily accessible and can be used to exclude other pathology, but its accuracy is limited by low sensitivity and specificity. Although magnetic resonance imaging is highly accurate for liver steatosis and fibrosis, its application is curbed in children as it requires sedation and longer scan time. Recently, attenuation imaging (ATI) has emerged as a new modality for quantifying fat deposition in the liver in real time. However, investigations of ATI for pediatric hepatic steatosis are still in their preliminary stages. Thus, we investigated the feasibility of ultrasound attenuation imaging (ATI) for assessing pediatric hepatic steatosis. This study demonstrated that ATI can differentiate fatty liver from normal liver as well as moderate to severe fatty liver from mild fatty liver. Thus, ATI may be useful for identifying children who require liver biopsy and early treatment.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.

Diagnostic performance of ultrasound attenuation imaging for assessing low-grade hepatic steatosis.

To investigate the diagnostic performance of attenuation imaging (ATI) for the assessment of low-grade hepatic steatosis using liver biopsy as the reference standard. The study included 57 potential donor candidates for living liver transplantation who underwent ATI, transient elastography (TE), and liver biopsy for evaluation of hepatic steatosis between February 2020 and April 2020. The attenuation coefficient (AC) from ATI and the controlled attenuation parameter (CAP) from TE were measured for each participant in a random and blind manner. The histologic hepatic fat fraction (HFF) was graded (S0, < 5%; S1, 5-33%; S2, 33-66%; S3, > 66%). The accuracy of ATI for diagnosing hepatic steatosis was compared with that of CAP using ROC analysis. Correlations between AC and HFF were evaluated, and factors affecting AC were determined by linear regression analysis. The median HFF was 3% (range: 0-35%), with 31 (54.4%), 24 (42.0%), and 2 (3.5%) participants being graded as S0, S1, and S2, respectively. The AUCs for the ROCs of AC and CAP for the detection of hepatic steatosis were 0.808 (95% CI: 0.682-0.900) and 0.829 (95% CI: 0.706-0.916), respectively, with the difference not being statistically significant (p = 0.762). AC showed 61.5% of sensitivity and 90.3% of specificity. AC was positively correlated with HFF (p < 0.001). HFF was the only factor significantly affecting AC. ATI showed moderate sensitivity and high specificity in the diagnosis and quantification of hepatic steatosis in low-grade steatosis without fibrosis. Only HFF significantly affected AC. • Attenuation imaging showed moderate sensitivity and high specificity performance in the diagnosis and quantification of hepatic steatosis in low-grade steatosis without fibrosis. • The diagnostic performance of the attenuation coefficient by attenuation imaging did not significantly differ from that of the controlled attenuation parameter by transient elastography in quantifying low-grade steatosis. • The histopathologically determined hepatic fat fraction was the only factor significantly affecting the attenuation coefficient.

Quantitative assessment of fatty liver using ultrasound attenuation imaging.

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease, with an incidence of 20-40% worldwide, making it a major healthcare problem. Because NAFLD can progress to liver fibrosis and cirrhosis through non-alcoholic steatohepatitis, early detection and monitoring of hepatic steatosis are essential for management of NAFLD patients. Even though conventional B-mode ultrasound (US) has been widely used for the evaluation of NAFLD owing to its safety and easy accessibility, its subjective nature and limited accuracy in detecting mild steatosis are major limitations. To overcome the current limitations of conventional B-mode US, attenuation imaging (ATI) based on two-dimensional B-mode US has been developed. ATI can quantitatively assess the degree of hepatic steatosis by calculating the attenuation coefficient, which reflects the degree of US beam attenuation transmitted into the liver tissue. After the first study was published in 2019, several clinical studies using ATI to evaluate hepatic steatosis have reported promising results. In this review, the basic physics, measurement protocol, and reported diagnostic accuracy of ATI in evaluating hepatic steatosis will be discussed.

Attenuation Imaging with Ultrasound as a Novel Evaluation Method for Liver Steatosis.

In recent years, ultrasound attenuation imaging (ATI) has emerged as a new method to detect liver steatosis. However, thus far, no studies have confirmed the clinical utility of this technology. Using a retrospective database analysis of 28 patients with chronic liver disease who underwent ultrasound liver biopsy and ATI, we compared the presence and degree of steatosis measured by ATI with the results obtained through liver biopsy. The area under the receiver operating characteristic curve (AUROC) of the ATI for differentiating between normal and hepatic steatosis was 0.97 (95% confidence interval: 0.83–1.00). The AUROC of the ATI was 0.99 (95% confidence interval: 0.86–1.00) in grade ≥2 liver steatosis and 0.97 (95% confidence interval: 0.82–1.00) in grade 3. ATI showed good consistency and accuracy for the steatosis grading of liver biopsy. Therefore, ATI represents a novel diagnostic measurement to support the diagnosis of liver steatosis in non-invasive clinical practice.

Usefulness of US attenuation imaging for the detection and severity grading of hepatic steatosis in routine abdominal ultrasonography

PurposeTo assess the diagnostic performance of ultrasound (US) attenuation imaging (ATI) for diagnosis and grading of hepatic steatosis with comparison to magnetic resonance imaging-proton density fat fraction (MRI-PDFF) using mDIXON-Quant sequence. MethodsTotal 100 patients who underwent abdominal US ATI and MRI-PDFF within one month were included. Subjects were divided into three groups according to MRI-PDFF; Group 1 (no fatty liver), Q < 5.1%; Group 2 (mild fatty liver), 5.1% ≤ Q < 14.1%; and Group 3 (moderate fatty liver), Q ≥ 14.1%. US attenuation coefficients (AC) of enrolled patients were measured and correlated with MRI-PDFF. And their diagnostic performances were assessed. AC, MRI-PDFF, and liver function tests were compared among all groups. ResultsMean AC value of each group was as follows: Group 1 = 0.58 ± 0.11 dB/cm/MHz, Group 2 = 0.68 ± 0.08 dB/cm/MHz, and Group 3 = 0.77 ± 0.06 dB/cm/MHz. Mean AC value of each group of hepatic steatosis showed statistically significant difference (p < 0.001). There was a significant correlation between AC and MRI-PDFF in Pearson correlation (r = 0.751, p < 0.001). The area under the ROC curve (AUROC) of AC was 0.914 with sensitivity of 91.5%, and specificity of 80.0% for detection of mild fatty liver, and 0.935 for detection of moderate fatty liver with sensitivity of 93.3%, and specificity of 87.1%. ConclusionAC using ultrasound ATI showed high diagnostic performance and provided discriminative values for severity grading of fatty liver disease.

The effect of water intake on ultrasound tissue characteristics and hemodynamics of adult livers.

Aim of the studyTo assess the effect of water intake on ultrasound tissue characteristics and hemodynamics of adult livers.Material and methodsIn February 2020, we prospectively performed ultrasound shear wave elastography and attenuation imaging (ATI) of the liver parenchyma, and spectral Doppler sonography of the portal vein and hepatic artery in 19 adult healthy volunteers (10 men and 9 women, mean age 27 years, mean body mass index 24.65 kg/m2). We measured liver shear wave velocity (SWV, m/s), shear wave dispersion (SWD, m/s/kHz), attenuation coefficient (dB/cm/MHz), main portal vein velocity (PVV, cm/s), hepatic artery peak systolic velocity (PSV, cm/s), and end diastolic velocity (EDV, cm/s) immediately before and at different time points (15, 30, 45, and 60 minutes) after water intake (1.0 l water and 1.5 l water for body weight < 150 lbs. and ≥ 150 lbs., respectively).ResultsThe differences in SWV, PVV, hepatic artery PSV and EDV before and after water intake were significant (p < 0.01) whereas the differences in SWD and ATI were not (p > 0.05) based on repeated measures ANOVA tests. The values of SWV, PVV, PSV, and EDV reached a peak at 30-45 minutes and returned to baseline 60 minutes after water intake. We observed positive correlations of SWV with PVV, PSV, and EDV in linear regression analyses (r2 > 0.73).ConclusionsWater intake affects the liver stiffness and hemodynamics. No water intake at least one hour prior to liver ultrasound elastography and Doppler sonography is recommended.