Shear Wave Liver Elastography with a Propagation Map: Diagnostic Performance and Inter-Observer Correlation for Hepatic Fibrosis in Chronic Hepatitis

Shear wave elastography primer for the abdominal radiologist

PURPOSE

Shear wave elastography (SWE) provides a means for adding information about the mechanical properties of tissues to a diagnostic ultrasound examination. It is important to understand the physics and methods by which the measurements are made to aid interpretation of the results as they relate to disease processes.

METHODS

The components of how ultrasound is used to generate shear waves and make measurements of the induced motion are reviewed. The physics of shear wave propagation are briefly described for elastic and viscoelastic tissues. Additionally, shear wave propagation in homogeneous and inhomogeneous cases is addressed.

RESULTS

SWE technology has been implemented by many clinical vendors with different capabilities. Various quality metrics are used to define valid measurements based on aspects of the shear wave signals or wave velocity estimates.

CONCLUSION

There are many uses for SWE in abdominal imaging, but it is important to understand how the measurements are performed to gauge their utility for diagnosis of different conditions. Continued efforts to make the technology robust in complex clinical situations are ongoing, but many applications actively benefit from added information about tissue mechanical properties for a more holistic view of the patient for diagnosis or assessment of prognosis and treatment management.

Diagnostic performance of two-dimensional shear wave elastography and attenuation imaging for fibrosis and steatosis assessment in chronic liver disease

PURPOSE

We investigated the diagnostic performance of two-dimensional shear wave elastography (2D-SWE) and attenuation imaging (ATI) in detecting fibrosis and steatosis in patients with chronic liver disease (CLD), comparing them with established methods.

METHODS

In 190 patients with CLD, 2D-SWE and vibration-controlled transient elastography (VCTE) were used for liver stiffness measurement (LSM), and ATI and controlled attenuation parameter (CAP) were used for steatosis quantification. The correlations between these new and established methods were analyzed.

RESULTS

Significant correlations were found between 2D-SWE and VCTE (r = 0.78, P < 0.001), and between ATI and CAP (r = 0.70, P < 0.001). Liver stiffness tended to be lower with 2D-SWE compared with that with VCTE, especially in cases with higher LSM, and ATI was less influenced by skin-capsular distance than CAP. Area under the receiver-operating characteristics curves (AUCs) and optimal cut-offs of 2D-SWE for diagnosing liver fibrosis stages F2, F3, and F4 were 0.73 (8.7 kPa), 0.79 (9.1 kPa), and 0.88 (11.6 kPa), respectively. The AUCs and optimal cut-offs of ATI for diagnosing hepatic steatosis grades S1, S2, and S3 were 0.91 (0.66 dB/cm/MHz), 0.80 (0.79 dB/cm/MHz), and 0.88 (0.86 dB/cm/MHz), respectively. A subgroup analysis of 86 patients with metabolic dysfunction-associated steatotic liver disease also demonstrated good performance for 2D-SWE and ATI.

CONCLUSION

2D-SWE and ATI performed comparably with conventional VCTE and CAP in evaluating CLD, offering reliable alternatives for diagnosing liver fibrosis and steatosis.

Prediction of acute rejection in renal allografts using shear-wave dispersion slope

OBJECTIVES

To evaluate the role of shear-wave dispersion slope for predicting renal allograft dysfunction.

METHODS

We retrospectively reviewed 128 kidney transplant recipients (median age, 55 years [interquartile range, 43-62 years]; male, 68) who underwent biopsy for allograft evaluation from November 2022 to February 2023. Cortex and renal sinus fat stiffness and shear-wave dispersion slope were obtained at shear-wave elastography (SWE). Cortex-to-sinus stiffness ratio (SR) and dispersion slope ratio (DSR)-related clinical and pathologic factors were evaluated using multivariable linear regression analysis. We conducted univariate and multivariate analyses for multiparametric ultrasound (US) parameters for identifying acute rejection and calculated the area under the receiver operating curve (AUC) values.

RESULTS

Of 128 patients, 31 (24.2%) demonstrated acute rejection. The SR value did not differ between patient groups (1.21 vs. 1.20, p = 0.47). Patients with acute rejection demonstrated a higher DSR than those without rejection (1.4 vs. 1.21, p < 0.01). Interstitial fibrosis and tubular atrophy grade (IFTA; coefficient, 0.11/grade; p = 0.04) and renal transplant and biopsy interval (coefficient, 0.00007/day; p = 0.03) were SR determinant factors, whereas only IFTA grade (coefficient, 0.10/grade; p = 0.01) for DSR. Multivariate analysis revealed mean resistive index (odds ratio [OR] 1.08, 95% confidence interval [CI] 1.02-1.14, p = 0.01) and DSR value (OR 16.0, 95% CI 3.0-85.8, p = 0.001) as independent factors for predicting acute rejection. An AUC of 0.74 for detecting acute rejection was achieved by combining the resistive index and DSR value.

CONCLUSION

Shear-wave dispersion slope obtained at SWE may help identify renal allograft dysfunction.

CLINICAL RELEVANCE STATEMENT

Acute rejection in renal allografts is a major cause of allograft failure, but noninvasive diagnosis is a challenge. Shear-wave dispersion slope can identify acute rejection non-invasively.

KEY POINTS

• The interstitial fibrosis and tubular atrophy grade was a determinant factor for stiffness ratio and shear-wave dispersion slope ratio between cortex and renal sinus fat. • Shear-wave dispersion slope ratio between cortex and renal sinus fat could identify acute rejection in renal allografts. • A shear-wave dispersion slope has a potential to reduce unnecessary renal biopsy for evaluating renal allografts.

Validating the Baveno Elastography Criteria of Advanced Liver Fibrosis in Two-Dimensional Shear Wave Elastography: A Prospective Pathology-Based Study

INTRODUCTION

The Baveno criteria for assessing advanced liver fibrosis were mainly determined by transient elastography (TE), and its pathology-based validation studies in two-dimensional shear wave elastography (2D-SWE) remain limited. We aimed to validate the Baveno criteria through use of 2D-SWE.

METHOD

Consecutive patients who underwent liver biopsies for various benign liver diseases were prospectively recruited. Liver stiffness measurement (LSM) was simultaneously evaluated by TE and 2D-SWE. The optimal cutoff value to predict advanced liver fibrosis was determined by the Youden Index, and the diagnostic performance was estimated using area under the receiver operating characteristic (AUROC) analysis.

RESULTS

A total of 101 patients were enrolled having a median age of 55.0 (IQR: 46.0-63.5) years, with 53 (52.48%) of them being male. Using <9 and >14 kPa as the optimal dual cutoffs, the AUROC values in TE and 2D-SWE were 0.92 (95% CI: 0.83-0.97) and 0.93 (95% CI: 0.84-0.98), respectively (p = 0.61). The sensitivity and specificity of LSM by TE/2D-SWE achieved rates of 94.44%/94.44% and 86.00%/88.00%, respectively. However, using the Baveno criteria, the AUROC values in TE and 2D-SWE could remain achieving 0.91 (95% CI: 0.82-0.97) and 0.93 (95% CI: 0.84-0.98), respectively (p = 0.36). The sensitivity and specificity in TE/2D-SWE were 88.24%/88.24% and 86.79%/90.57%, respectively.

CONCLUSION

This study establishes the compatibility of the Baveno dual cutoff criteria with 2D-SWE, positioning it as an easily used criteria in clinical practice and research.

Quantitative Evaluation of the Lumbar Multifidus Muscle by Shear Wave Dispersion in Healthy Adults: A Preliminary Study

OBJECTIVES

To investigate the application value of shear wave dispersion (SWD) in healthy adults with the lumbar multifidus muscle (LMM), to determine the range of normal reference values, and to analyze the influences of factors on the parameter.

METHODS

Ninety-five healthy volunteers participated in the study, from whom 2-dimensional, shear wave elastography (SWE), and SWD images of the bilateral LMM were acquired in three positions (prone, standing, and anterior flexion). Subcutaneous fat thickness (SFH), SWE velocity, and SWD slope were measured accordingly for analyses.

RESULTS

The mean SWD slope of the bilateral LMM in the prone position was as follows: left: 14.8 ± 3.1 (m/second)/kHz (female) and 13.0 ± 2.5 (m/second)/kHz (male); right: 14.8 ± 3.7 (m/second)/kHz (female) and 14.2 ± 3.4 (m/second)/kHz (male). In the prone position, there was a weak negative correlation between the bilateral LMM SWD slope of activity level 2 and level 1 (β = -1.5 (2 versus 1, left), -1.9 (2 versus 1, right), all P < .05), and between the left SWD slope of activity level 3 and level 1 (β = -2.3 [3 versus 1, left], P < .05). The correlation between SWE velocity and SWD slope value changed with the position: there was a weak positive correlation in the prone position (r = 0.3 [left], 0.37 [right], both P < .05), and a moderate positive correlation in the standing and anterior flexed positions (r = 0.49-0.74, both P < .001). SFH was moderately negatively correlated with bilateral SWD slope values in the anterior flexion (left: r = -0.4, P = .01; right: r = -0.7, P < .01).

CONCLUSIONS

SWD imaging can be used as an adjunct tool to aid in the assessment of viscosity in LMM. Further, activity level, and position are influencing factors that should be considered in clinical practice.

Ultrasound shear wave elastography for the evaluation of renal pathological changes in adult patients

OBJECTIVE

Many studies have conflicting findings in using shear wave elastography (SWE) to assess renal fibrosis. This study reviews the use of SWE to evaluate pathological changes in native kidneys and renal allografts. It also tries to elucidate the confounding factors and care taken to ensure the results are consistent and reliable.

METHODS

The review was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Literature search was conducted in Pubmed, Web of Science and Scopus database up to 23 October 2021. To evaluate risk and bias applicability, the Cochrane risk-of bias tool and GRADE was used. The review was registered under PROSPERO CRD42021265303.

RESULTS

A total of 2921 articles were identified. 104 full texts were examined and 26 studies included in systematic review. 11 studies performed on native kidneys and 15 studies on transplanted kidney. A wide range of impact factors was found that affect the accuracy of SWE of renal fibrosis in adult patients.

CONCLUSIONS

Compared to point SWE, two-dimensional SWE with elastogram could enable better selection of the region of interest in kidneys, leading to reproducible results. Tracking waves were attenuated as the depth from skin to region of interest increased, therefore, SWE is not recommended for overweight or obese patients. Variable transducer forces might also affect SWE reproducibility, thus, training of operators to ensure consistent operator-dependent transducer forces may be helpful.

ADVANCES IN KNOWLEDGE

This review provides a holistic insight on the efficiency of using SWE in evaluating pathological changes in native and transplanted kidneys, thereby contributing to the knowledge of its utilisation in clinical practice.

Clinical application of two dimensional shear wave elastography with a propagation map in evaluating liver fibrosis in patients with liver tumors

OBJECTIVE

This study aimed to evaluate the diagnostic performance of two-dimensional shear wave elastography (2D-SWE) with a propagation map in evaluating the degree of hepatic fibrosis in patients with liver tumors before resection.

METHODS AND MATERIALS

From January 2020 to April 2021, 128 patients with liver tumors were prospectively enrolled, including 20 benign liver tumors and 108 malignant liver tumors. 2D-SWE with a propagation map technology was used to measure the stiffness of liver parenchyma 2 cm away from the tumor. The median value of five measurements was used in this study. The stage of hepatic fibrosis was graded in accordance with Scheuer standard. Spearman correlation was used to analyze the correlation between liver fibrosis stage and the liver stiffness. Univariate and multivariate linear regression analyses were used to determine significant affecting factors for liver stiffness value. The diagnostic performance of 2D-SWE with a propagation map in predicting fibrosis stage was evaluated by receiver operating characteristic curve analysis.

RESULTS

The median liver stiffness value in patients with benign liver tumors was lower than that in patients with malignant liver tumors (6.0 kPa vs. 9.4 kPa, p < 0.05). The median liver stiffness values in patients with primary liver cancer were higher than that in patients with benign liver tumors and other types of malignant liver tumors (9.6 kPa vs. 6.0 kPa, p < 0.05). The liver stiffness measured by 2D-SWE was highly correlated with the fibrosis stage confirmed by postoperative pathology (r = 0.834, p < 0.05). For the liver stiffness value, PLT,TB,ALB and fibrosis stage are significantly associated with liver stiffness. The median liver stiffness values in stages S0-S4 of fibrosis were 6.0, 7.2, 8.0, 9.4, and 12.6 kPa, respectively. The areas under the ROC curve of S≥1, S≥2, S≥3, and S = 4 as predicted by SWE were 0.932, 0.945, 0.945, and 0.916, respectively. According to the Youden index, the optimal critical values for predicting fibrosis S≥1, S≥2, S≥3, and S = 4 were 6.8 (sensitivity of 89.69% and specificity of 93.55%), 7.5 (sensitivity of 87.50 % and specificity of 95.00 %), 8.3 (sensitivity of 87.14 % and specificity of 87.93 %) and 9.8 (sensitivity of 79.55 % and specificity of 86.90 %) kPa.

CONCLUSION

2D-SWE with a propagation map could noninvasively and accurately predict the staging of liver fibrosis in patients with liver tumors before resection.

Two-dimensional Shear-Wave Elastography and US Attenuation Imaging for Nonalcoholic Steatohepatitis Diagnosis: A Cross-sectional, Multicenter Study

Background Multiparametric US examination may have potential in the comprehensive evaluation of nonalcoholic fatty liver disease (NAFLD), but multicenter studies are lacking. Purpose To evaluate the diagnostic performance of multiparametric US with the attenuation coefficient (AC) from attenuation imaging (ATI) and liver stiffness (LS) and dispersion slope (DS) from two-dimensional (2D) shear-wave elastography (SWE) in a multicenter study of patients with NAFLD. Materials and Methods This prospective study enrolled consecutive participants between December 2019 and June 2021 with suspected nonalcoholic steatohepatitis (NASH) who were scheduled to undergo liver biopsy in five tertiary hospitals. Before the procedure, all participants underwent US with ATI and 2D SWE according to the study protocol. Multivariable linear regression analyses were performed to determine the significant determinant factors for AC, LS, and DS. Diagnostic performance was decided based on the areas under the receiver operating characteristic curve (AUCs). Results A total of 132 participants (median age, 38 years; IQR, 27-54 years; 69 women) were evaluated. Among the participant characteristics, including pathologic findings, demographic characteristics, body mass index, and serum markers, hepatic steatosis for AC (P < .001), lobular inflammatory activity for DS (P = .007), and both fibrosis (P = .01) and lobular inflammatory activity (P = .04) for LS were significant determinant factors. At histopathologic examination, 53 of the 132 participants (40.2%) had NASH. The risk score system obtained using unweighted sum of scores from AC and DS showed the best diagnostic performance in the detection of NASH (AUC = 0.94; 95% CI: 0.89, 0.98; P < .05 for all), as compared with serum markers or other US parameters alone (AUC ≤ 0.88). Conclusion US attenuation imaging and two-dimensional shear-wave elastography were useful for assessing hepatic steatosis, lobular inflammation, and fibrosis. The risk score system obtained using the attenuation coefficient and dispersion slope showed the best diagnostic performance fo r nonalcoholic steatohepatitis. cris.nih.go.kr no. KCT0004326 © RSNA, 2022 Online supplemental material is available for this article.

Evaluation of liver fibrosis in chronic hepatitis B patients with 2D shear wave elastography with propagation map guidance: a single-centre study

Background

The aims of this study were to evaluate liver fibrosis with two-dimensional (2D) shear wave elastography (SWE) in patients with chronic hepatitis B (CHB), to compare 2D-SWE with histopathology and to determine the change in liver stiffness values after antiviral therapy.

Material and methods

A total of 253 patients with CHB were included in this prospective study. 2D-SWE with propagation map guidance to measure liver stiffness, fibrosis-4 index (FIB-4) and aspartate aminotransferase to platelet ratio index (APRI) scoring and additional liver biopsy were performed in patients with CHB. Liver stiffness was measured again at 24 and 48 weeks in all patients. The Spearman rank correlation test was used to analyse the correlation between variables, and receiver operating curve analysis was used to evaluate the diagnostic performance in terms of fibrosis.

Results

Liver stiffness measurements made with 2D-SWE demonstrated a significant positive correlation with the fibrosis stage and FIB-4 score (r_s = 0.774 and 0.337, respectively, p < 0.001 for both). The area under the curve value for kPa for the prediction of significant fibrosis was 0.956 (95% CI_s) (0.920–0.991), and the optimal cut-off value was 8.2 kPa (sensitivity: 92.7% and specificity: 78.9%); these values were 0.978 (95% CI_s, 0.945–1.000) and 10.1 kPa (sensitivity: 92.9% and specificity: 96.4%) for the prediction of severe fibrosis. After antiviral treatment, a decrease in liver stiffness values measured by 2D-SWE was detected (mean kPa values at 0 and 48 weeks; 9.24 and 7.36, respectively, p < 0.001).

Conclusion

In conclusion, the measurement of liver stiffness with 2D-SWE has high diagnostic performance in the determination of hepatic fibrosis and can be used to evaluate the response to treatment in patients receiving antiviral therapy.

Quality criteria for the measurement of liver stiffness

Liver elastography offers the possibility of a quick, non-invasive, and painless evaluation of the liver with immediate results at bedside. Transient elastography is the most validated technology, and many others such as point shear wave elastography, 2D-shear wave elastography, or magnetic resonance elastography have been developed. To ensure the best evaluation, several conditions of examination must be respected for liver stiffness measurement. Indeed, patient, operator and examination characteristics have all been shown to influence the result of liver stiffness measurement. Food intake increases liver stiffness, whereas withdrawal in alcoholics is associated with a decrease in elastography results. Inter-observer reproducibility of the measurement seems suboptimal, and the influence of the operator experience is still being debated. The measurement site and the FibroScan® probe must be correctly chosen. Finally, the intrinsic characteristics and quality criteria of the measurement, especially the interquartile range/median ratio, must be carefully checked to avoid overestimation of liver stiffness. Most of the results come from studies which have evaluated transient elastography, with less data available for the other technologies. Liver stiffness measurement could appear as a simple way to explore the liver, but several conditions must be met before deciding the patient management according to its result.

Shear-Wave Dispersion Slope of the Liver: Effect of Study Protocol and Ascites on the Measurement Applicability

This study aimed to evaluate the shear-wave dispersion (SWD) scanning protocol including the minimum number of measurements and better size of the region of interest (ROI), as well as the influence of ascites on the measurement applicability. Patients who had undergone serial SWD examinations between July 2019 and December 2020 were included. In patients with chronic liver disease (group A), two different ROI sizes were applied, and at least 10 measurements were repeated to determine the minimum number of measurements and better ROI size. In patients with liver failure (group B), failure and unreliable results were compared between patients with and without ascites. A minimum of five measurements when using a 20-mm ROI and six measurements when using a 10-mm ROI were required. Compared with using a 20-mm ROI, a 10-mm ROI showed a higher unreliable rate. The failure and unreliable rates of SWD in patients with ascites were significantly higher than those in patients without ascites. SWD examination required at least five measurements when using a 20-mm ROI and six measurements when using a 10-mm ROI. A larger ROI was associated with higher reliability, and ascites influenced the failure and reliability of the SWD measurement.

Does Early Diabetic Kidney Damage Alter Renal Elasticity? An Ultrasound-Based, Two-Dimensional Shear Wave Elastography Study

Objective

Kidney damage caused by type 2 diabetes mellitus (T2DM) can reduce renal elasticity. Limited number of data exist indicating whether early kidney damage causes stiffening of renal tissue. This comparative study aims to assess kidney elasticity in T2DM patients with or without moderate albuminuria, using ultrasound-based two-dimensional shear wave velocity (2D-SWV) measurements.

Methods

Fifty-seven cases (40 T2D patients with stage 1 or 2 chronic kidney disease and 17 age- and sex-matched healthy controls) were included in this single-center prospective study. The T2DM patients were divided into those with moderate albuminuria (n=22) and those without albuminuria (n=18). Bilateral renal parenchymal 2D-SWV values were measured (separately) in the upper, middle, and lower kidney regions. Group data were compared using the t-test or Mann-Whitney-U test (whichever appropriate). Inter-observer agreement was assessed by deriving the intra-class correlation coefficient.

Results

There was no difference between the T2DM and control groups in terms of the median age [55.5 (50-62) vs. 55 (48.5-59.5) years, p=0.48] and sex ratio [18 (45%) males vs. 10 (58.8%) females, p=0.34]. The average regional 2D-SWV values were all similar between the groups (all p>0.05). The average 2D-SWV values were similar between the subgroups with and without albuminuria. The inter-observer agreement was good (intra-class correlation coefficient=0.66, 95% CI 0.19-0.88, p=0.006).

Conclusion

Kidney elasticity does not seem to be compromised in patients with diabetes and preserved estimated glomerular filtration rate with or without moderate albuminuria.

Diagnosis of Carpal Tunnel Syndrome using Shear Wave Elastography and High-frequency Ultrasound Imaging

OBJECTIVES

The performance of ultrasound features from shear wave elastography (SWE) and high-frequency ultrasound imaging was evaluated independently and in combination to diagnose carpal tunnel syndrome (CTS).

MATERIALS AND METHODS

Twenty-five subjects were imaged in a sitting position with an arm extended and palm facing up. SWE of the medial nerve (MN) was acquired at the wrist level (site 1) and proximal to the pronator quadratus muscle (site 2). Cross-sectional area (CSA) and vascularity of the MN were assessed at the wrist using a 24 MHz probe. Color and power Doppler imaging (CDI and PDI), monochrome and color-coded Superb Microvascular Imaging (SMI) were performed for vascularity assessments. The diagnosis and severity of CTS was determined by clinical and electrodiagnostic tests. Diagnostic performance of the ultrasound features was assessed by t-tests, ANOVAs, and ROC analysis.

RESULTS

The study included 20 control hands and 27 hands with CTS. All ultrasound features except for the stiffness ratio were significantly different between the CTS and control wrists (p<0.04). The stiffness of MN at site 1 showed a higher accuracy than at site 2. The combination of CSA and MN stiffness from site 2 showed an overall accuracy of 95% with a specificity and sensitivity of 100% and 93%, respectively. The CSA, MN stiffness from site 2, and CDI combination improved the accuracy to 96% with specificity and sensitivity of 100% and 93%, respectively. However, no ultrasound features (independently or in combination) differentiated all stages of CTS severity.

CONCLUSIONS

SWE with high-frequency ultrasound imaging showed potential for the diagnosis of CTS.

Diagnostic Performance of 2-D Shear-Wave Elastography with Propagation Maps and Attenuation Imaging in Patients with Non-Alcoholic Fatty Liver Disease

We aimed to investigate the diagnostic performance of new 2-D shear-wave elastography (SWE) with propagation maps and attenuation imaging (ATI) for quantification of fibrosis and steatosis in non-alcoholic fatty liver disease (NAFLD). Consecutive patients with NAFLD and healthy volunteers underwent liver stiffness measurement and steatosis quantification by means of vibration-controlled transient elastography coupled with the controlled attenuation parameter as the reference and by 2-D shear-wave elastography (2-D-SWE) with propagation maps and ATI as the investigational methods. We included 232 participants (164 in the NAFLD group and 68 in the healthy control group): 51.7%/49.3% women/men; mean age, 54.2 ± 15.2 y; mean body mass index, 29.4 ± 6.5 kg/m2. Significant correlations were found between 2-D-SWE and vibration-controlled transient elastography (r = 0.71, p < 0.0001) and between ATI and the controlled attenuation parameter (r = 0.72, p < 0.0001). NAFLD-specific 2-D-SWE liver stiffness measurement cutoffs were as follows-F ≥ 2: 7.9 kPa (area under the curve [AUC] = 0.91); F ≥ 3: 10 kPa (AUC = 0.92); and F = 4: 11.4 kPa (AUC = 0.95). For steatosis, the best cutoffs by ATI were as follows-S1 = 0.73 dB/cm/MHz (AUC = 0.86); S2 = 0.76 dB/cm/MHz (AUC = 0.86); and S3 = 0.80 dB/cm/MHz (AUC = 0.83). According to Baveno VI criteria, the optimal 2-D-SWE liver stiffness measurement for diagnosing liver cirrhosis is 15.5 kPa (AUC = 0.94), and for ruling out compensated advanced chronic liver disease it is 9.2 kPa (AUC = 0.92). To conclude, 2-D-SWE with propagation maps and ATI is reliable for quantification of liver fibrosis and steatosis in patients with NAFLD.

2D shear wave elastography is better than transient elastography in predicting post-hepatectomy complication after resection

OBJECTIVES

Both transient elastography (TE) and 2D shear wave elastography (SWE) are accurate methods to evaluate liver fibrosis. We aimed to evaluate the diagnostic performance of 2D-SWE in predicting post-hepatectomy complication and to compare it with TE.

METHODS

We prospectively enrolled 125 patients with liver tumors. Liver stiffness (LS) (kilopascal [kPa]) was measured using both TE and 2D-SWE before surgery. All post-operative complication was evaluated using the comprehensive complication index (CCI), and CCI ≥ 26.2 was defined as severe complication. Logistic regression analysis was performed to identify predictive factors for severe complication. Receiver operating characteristic analysis was used to evaluate the diagnostic performance of TE/2D-SWE in detecting liver fibrosis and severe complication.

RESULTS

Severe complication developed in 18 patients. The median LS in patients with severe complication was significantly higher for both 2D-SWE (11.4 kPa vs. 7.0 kPa, p < 0.001) and TE (8.9 kPa vs. 6.2 kPa, p = 0.009). LS obtained from 2D-SWE was a significant factor correlated with severe complication (odds ratio: 1.27 per kPa [1.10-1.46], p = 0.001). The diagnostic performance of 2D-SWE was significantly higher than that of TE in detecting both ≥F3 (p = 0.024) and F4 (p = 0.048). The area under the curve of 2D-SWE to predict severe complication was 0.854, significantly higher than 0.692 of TE (p = 0.004). The optimal cut-off LS from 2D-SWE to predict severe complication was 8.6 kPa, with sensitivity of 88.9% (16/18) and specificity of 73.8% (79/107).

CONCLUSION

LS obtained from 2D-SWE was a significant predictive factor for severe complication, and 2D-SWE showed significantly a better diagnostic performance than TE in detecting liver fibrosis and severe complication.

KEY POINTS

• The diagnostic performance of 2D-SWE was significantly higher than that of TE in detecting both ≥ F3 (AUC: 0.853 vs. 0.779, p = 0.024) and F4 (AUC: 0.929 vs. 0.872, p = 0.048). • Liver stiffness value obtained from 2D-SWE was a significant factor correlated with the development of severe complication defined as CCI ≥ 26.2 after hepatic resection for liver tumors (odds ratio: 1.27 per kPa [1.10-1.46], p = 0.001). • 2D-SWE provided significantly a better diagnostic performance in predicting severe complication after hepatic resection than TE (AUC for 2D-SWE: 0.853 vs. AUC for TE: 0.692, p = 0.004).

Added value of 2D shear wave imaging of the gallbladder bed of the liver for acute cholecystitis

PURPOSE

The purpose of this study was to evaluate whether shear wave elastography (SWE) and the shear wave dispersion slope (SWD) obtained from 2-dimensional shear wave imaging (2D-SWI) of the gallbladder (GB) bed of the liver could be helpful in the diagnosis of acute cholecystitis.

METHODS

We included 44 patients referred for abdominal ultrasonography (US) under the impression of acute cholecystitis from April 2018 to March 2019. Patients with chronic liver disease were excluded from this study. In addition to routine upper abdominal US, we performed 2D-SWI including liver stiffness measurements by SWE and SWD, which reflects tissue viscosity. 2D-SWI was performed at the GB bed of the liver through the right intercostal approach at least 3 times with different frames. We assessed typical US findings and the added value of 2D-SWI in diagnosing acute cholecystitis. Histopathologic results of surgical specimens were used as the standard of reference. If a surgical specimen was unavailable, a bile fluid test or clinical follow-up for more than 3 months served as the reference standard.

RESULTS

The optimal cutoff values for SWE and SWD were 8 kPa and 10.9 (m/sec)/kHz, respectively. In the univariate analysis, SWE, GB distension, and sludge were predictive factors of acute cholecystitis. In the multivariate analysis, categorized SWE was the only significant predictor (P<0.01). By using 2D-SWI, the diagnostic performance of two readers did not significantly increase, although the inter-reader agreement improved (k=0.654-0.778).

CONCLUSION

2D-SWI of the GB bed of the liver could be helpful for diagnosing acute cholecystitis.

Two-Dimensional-Shear Wave Elastography with a Propagation Map: Prospective Evaluation of Liver Fibrosis Using Histopathology as the Reference Standard

Objective

The aim of this study was to prospectively evaluate whether liver stiffness (LS) assessments, obtained by two-dimensional (2D)-shear wave elastography (SWE) with a propagation map, can evaluate liver fibrosis stage using histopathology as the reference standard.

Materials and Methods

We prospectively enrolled 123 patients who had undergone percutaneous liver biopsy from two tertiary referral hospitals. All patients underwent 2D-SWE examination prior to biopsy, and LS values (kilopascal [kPa]) were obtained. On histopathologic examination, fibrosis stage (F0–F4) and necroinflammatory activity grade (A0–A4) were assessed. Multivariate linear regression analysis was performed to determine the significant factors affecting the LS value. The diagnostic performance of the LS value for staging fibrosis was assessed using receiver operating characteristic (ROC) analysis, and the optimal cut-off value was determined by the Youden index.

Results

Reliable measurements of LS values were obtained in 114 patients (92.7%, 114/123). LS values obtained from 2D-SWE with the propagation map positively correlated with the progression of liver fibrosis reported from histopathology (p < 0.001). According to the multivariate linear regression analysis, fibrosis stage was the only factor significantly associated with LS (p < 0.001). The area under the ROC curve of LS from 2D-SWE with the propagation map was 0.773, 0.865, 0.946, and 0.950 for detecting F ≥ 1, F ≥ 2, F ≥ 3, and F = 4, respectively. The optimal cut-off LS values were 5.4, 7.8, 9.4, and 12.2 kPa for F ≥ 1, F ≥ 2, F ≥ 3, and F = 4, respectively. The corresponding sensitivity and specificity of the LS value for detecting cirrhosis were 90.9% and 88.4%, respectively.

Conclusion

The LS value obtained from 2D-SWE with a propagation map provides excellent diagnostic performance in evaluating liver fibrosis stage, determined by histopathology.

Technical Performance of Two-Dimensional Shear Wave Elastography for Measuring Liver Stiffness: A Systematic Review and Meta-Analysis

Objective

To assess the technical performance of two-dimensional shear wave elastography (2D-SWE) for measuring liver stiffness.

Materials and Methods

The Ovid-MEDLINE and EMBASE databases were searched for studies reporting the technical performance of 2D-SWE, including concerns with technical failures, unreliable measurements, interobserver reliability, and/or intraobserver reliability, published until June 30, 2018. The pooled proportion of technical failure and unreliable measurements was calculated using meta-analytic pooling via the random-effects model and inverse variance method for calculating weights. Subgroup analyses were performed to explore potential causes of heterogeneity. The pooled intraclass correlation coefficients (ICCs) for interobserver and intraobserver reliability were calculated using the Hedges-Olkin method with Fisher's Z transformation of the correlation coefficient.

Results

The search yielded 34 articles. From 20 2D-SWE studies including 6196 patients, the pooled proportion of technical failure was 2.3% (95% confidence interval [CI], 1.3–3.9%). The pooled proportion of unreliable measurements from 20 studies including 6961 patients was 7.5% (95% CI, 4.7–11.7%). In the subgroup analyses, studies conducting more than three measurements showed fewer unreliable measurements than did those with three measurements or less, but no intergroup difference was found in technical failure. The pooled ICCs for interobserver reliability (from 10 studies including 517 patients) and intraobserver reliability (from 7 studies including 679 patients) were 0.87 (95% CI, 0.82–0.90) and 0.93 (95% CI, 0.89–0.95), respectively, suggesting good to excellent reliability.

Conclusion

2D-SWE shows good technical performance for assessing liver stiffness, with high technical success and reliability. Future studies should establish the quality criteria and optimal number of measurements.

Two-dimensional Shear Wave Elastography with Propagation Maps for the Assessment of Liver Fibrosis and Clinically Significant Portal Hypertension in Patients with Chronic Liver Disease: A Prospective Study

OBJECTIVES

To investigate the diagnostic performance of liver stiffness (LS) measurements on two-dimensional (2D) shear wave elastography (SWE) for the assessment of hepatic fibrosis using LS measurements on MR elastography (MRE) as the reference standard and the prediction of clinically significant portal hypertension (CSPH).

METHODS

In this prospective study, 101 patients with chronic liver disease or cirrhosis underwent both MRE and SWE. After exclusion of technical failure on MRE (n = 5), technical failure/unreliable measurement on SWE (n = 4), LS measurements obtained on SWE with the aid of propagation maps were correlated with those of the MRE using Pearson's correlation analysis. Diagnostic performances for significant fibrosis (≥F2: MRE of ≥2.99 kPa) or cirrhosis (F4: MRE of ≥3.63 kPa) and for the prediction of CSPH were assessed using receiver operating characteristics (ROC) curve analysis.

RESULTS

LS values on SWE showed a strong correlation with those on MRE (r = 0.846, P < 0.001). For the diagnosis of significant fibrosis or cirrhosis in patients with hepatitis B virus-related liver disease (n = 75), SWE showed areas under the ROC curves (AUC) of 0.975 and 0.912, respectively (95% confidence interval [CI], 0.910-997, and 0.824-0.965). For the prediction of CSPH, the AUC of SWE was 0.818 (95% CI, 0.712-0.898), and when an LS value of 11.5 kPa was applied as a cut-off, SWE showed a sensitivity of 81.5% and a specificity of 72.9%.

CONCLUSION

LS measurements on 2D SWE were demonstrated to be well correlated with those obtained with MRE, and thus, may provide good diagnostic performance for the prediction of hepatic fibrosis and the presence of CSPH.

Diagnostic problems in two-dimensional shear wave elastography of the liver

Two-dimensional shear wave elastography (2D-SWE) is used in the clinical setting for observation of the liver. Unfortunately, a wide spectrum of artifactual images are frequently encountered in 2D-SWE, the precise mechanisms of which remain incompletely understood. This review was designed to present many of the artifactual images seen in 2D-SWE of the liver and to analyze them by computer simulation models that support clinical observations. Our computer simulations yielded the following suggestions: (1) When performing 2D-SWE in patients with chronic hepatic disease, especially liver cirrhosis, it is recommended to measure shear wave values through the least irregular hepatic surface; (2) The most useful 2D-SWE in patients with focal lesion will detect lesions that are poorly visible on B-mode ultrasound and will differentiate true tumors from pseudo-tumors (e.g., irregular fatty change); and (3) Measurement of shear wave values in the area posterior to a focal lesion must be avoided.

Reproducibility of ultrasound attenuation imaging for the noninvasive evaluation of hepatic steatosis

PURPOSE

The purpose of this study was to evaluate the intra-observer reproducibility of ultrasound attenuation imaging (ATI) for the noninvasive assessment of hepatic steatosis in patients with suspected hepatic steatosis and the inter-observer reproducibility in asymptomatic volunteers.

METHODS

This prospective study was approved by our institutional review board and informed consent was obtained from all patients. In group 1, composed of patients with suspected hepatic steatosis (n=143), one abdominal radiologist performed gray-scale ultrasonography and two sessions of ATI. In group 2, composed of healthy volunteers (n=18), three independent sessions of ATI were performed by three abdominal radiologists. The visual degree of hepatic steatosis in all study subjects was graded on a 4-point scale by two independent reviewers using gray-scale ultrasonography. Thereafter, the attenuation coefficient (AC) was correlated with the degree of hepatic steatosis using Spearman rank correlation analysis. Intra-class correlation coefficients (ICCs) were used to assess the intra-observer (group 1) and inter-observer reproducibility (group 2) of ATI measurements.

RESULTS

For the intra-observer reproducibility of ATI, the ICC was 0.929 (95% confidence interval [CI], 0.901 to 0.949), and the coefficient of variation was 7.1%. Inter-observer reproducibility of ATI measurements showed an ICC of 0.792 (95% CI, 0.549 to 0.916). The AC showed a significant correlation with the visual grade of hepatic steatosis for both reviewers (rho, 0.780 and 0.695; P<0.001, respectively).

CONCLUSION

ATI showed high intra- and inter-observer reproducibility in the assessment of hepatic steatosis.

Comparison of point and 2-dimensional shear wave elastography for the evaluation of liver fibrosis

PURPOSE

This study aimed to assess the technical performance of ElastQ Imaging compared with ElastPQ and to investigate the correlation between liver stiffness (LS) values obtained using these two techniques.

METHODS

This retrospective study included 249 patients who underwent LS measurements using both ElastPQ and ElastQ Imaging equipped on the same machine. The applicability, repeatability (coefficient of variation [CV]), acquisition time, and LS values were compared using the chi-square or Wilcoxon signed-rank tests. In the development group, the correlation between the LS values obtained by the two techniques was assessed with Spearman correlation coefficients and linear regression analysis. In the validation group, the agreement between the estimated and real LS values was evaluated using a Bland-Altman plot.

RESULTS

ElastQ Imaging had higher applicability (94.0% vs. 78.3%, P<0.001) and higher repeatability, with a lower median CV (0.127 vs. 0.164, P<0.001) than did ElastPQ. The median acquisition time of ElastQ Imaging was significantly shorter than that of ElastPQ (45.5 seconds vs. 96.5 seconds, P<0.001). The median LS value obtained using ElastQ Imaging was significantly higher than that obtained using ElastPQ (5.60 kPa vs. 5.23 kPa, P<0.001). The LS values between the two techniques exhibited a strong positive correlation (r=0.851, P<0.001) in the development group. The mean difference and 95% limits of agreement were 0.0 kPa (-3.9 to 3.9 kPa) in the validation group.

CONCLUSION

ElastQ Imaging may be more reliable and faster than ElastPQ, with strongly correlated LS measurements.

Shear-Wave Dispersion Slope from US Shear-Wave Elastography: Detection of Allograft Damage after Liver Transplantation

Background Allograft damage (hepatic parenchymal damage) after liver transplant is associated with the degree of necroinflammation in graft liver. According to a recent animal study, shear-wave dispersion slope obtained at US shear-wave elastography (SWE) is associated with necroinflammatory activity in the liver. Purpose To evaluate the role of shear-wave dispersion slope in detecting allograft damage after liver transplant. Materials and Methods In this prospective study, 104 liver transplant recipients underwent percutaneous liver biopsy for allograft evaluation from December 2017 to November 2018. All participants underwent allograft SWE examination just before liver biopsy, and liver stiffness and shear-wave dispersion slope were obtained. Allograft damage was diagnosed by histopathologic analysis. Clinical and imaging factors related to liver stiffness and shear-wave dispersion slope were determined by multivariable linear regression analysis. Diagnostic performance of each variable in detecting allograft damage was evaluated by comparing area under the receiver operating curve (AUC) values. Results There were 104 study participants (35 women); median age was 56 years (interquartile range, 50-62 years). Allograft damage was found in 46 of 104 (44.2%) of participants. The median liver stiffness (8.2 kPa vs 6.3 kPa; P < .01) and shear-wave dispersion slope (14.4 [m/sec]/kHz vs 10.4 [m/sec]/kHz; P < .01) were higher in participants with allograft damage than in those without damage, respectively. Fibrosis stage was the only determinant factor for liver stiffness (coefficient, 1.8 kPa per fibrosis stage; 95% confidence interval: 0.1, 3.5; P = .03), whereas both fibrosis stage (coefficient, 1.4 [m/sec]/kHz per fibrosis stage; 95% confidence interval: 0.3, 2.6; P = .02) and necroinflammatory activity (coefficient, 1.6 [m/sec]/kHz per necroinflammatory activity grade; 95% confidence interval: 0.5, 2.7; P < .01) affected shear-wave dispersion slope. The AUC for shear-wave dispersion slope in detecting allograft damage was 0.86, which was higher than that of liver stiffness (AUC, 0.75; P < .01). Conclusion Shear-wave dispersion slope determined at US shear-wave elastography may help in detecting allograft damage after liver transplant. © RSNA, 2019 Online supplemental material is available for this article.

Propagation Imaging in the Demonstration of Common Shear Wave Artifacts

In this article, we describe our experience with shear wave propagation imaging (SWPI) as an adjunct to 2-dimensional (2D) shear wave elastography (SWE) in a cohort of patients being evaluated for diffuse liver disease. Two-dimensional SWE has been extensively studied in previous publications; however, 2D SWE using propagation images has not been widely described in the literature to date. We observed that when certain artifacts occurred on the color elastograms, highly characteristic changes to shear wave propagation contours were seen, which can help clarify the cause of the artifacts. To our knowledge, the use of SWPI to explain the etiology of artifacts has never been published before. The artifacts described in this article include the capsule reverberation artifact, penetration limitation or dropout artifact, artifact due to blood vessels, shadowing artifact, tissue motion artifact, and near-field distortion/precompression artifact. Hence, the purpose of this article is to show examples of common artifacts seen on 2D SWE as depicted on corresponding SWPI to demonstrate that both types of image displays are complementary to each other.

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.

Evaluation of liver lesions by use of shear wave elastography and computed tomography perfusion imaging after radiofrequency ablation in clinically normal dogs

OBJECTIVE To evaluate acute changes of the liver by use of shear wave elastography (SWE) and CT perfusion after radiofrequency ablation (RFA). ANIMALS 7 healthy Beagles. PROCEDURES RFA was performed on the liver (day 0). Stiffness of the ablation lesion, transitional zone, and normal parenchyma were evaluated by use of SWE, and blood flow, blood volume, and arterial liver perfusion of those regions were evaluated by use of CT perfusion on days 0 and 4. All RFA lesions were histologically examined on day 4. RESULTS Examination of the SWE color-coded map distinctly revealed stiffness of the liver tissue, which increased from the normal parenchyma to the transitional zone and then to the ablation zone. For CT perfusion, blood flow, blood volume, and arterial liver perfusion decreased from the transitional zone to the normal parenchyma and then to the ablation zone. Tissue stiffness and CT perfusion variables did not differ significantly between days 0 and 4. Histologic examination revealed central diffuse necrosis and peripheral hyperemia with infiltration of lymphoid cells and macrophages. CONCLUSIONS AND CLINICAL RELEVANCE Coagulation necrosis induced a loss of blood perfusion and caused tissue hardening (stiffness) in the ablation zone. Hyperemic and inflammatory changes of the transitional zone resulted in increased blood perfusion. Acute changes in stiffness and perfusion of liver tissue after RFA could be determined by use of SWE and CT perfusion. These results can be used to predict the clinical efficacy of RFA and to support further studies, including those involving hepatic neoplasia.