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

Renal transplant ultrasound: assessment of complications and advanced applications

Renal transplantation is the most commonly performed solid organ transplant procedure. Monitoring renal transplants with ultrasound is a critical component in the management of transplant patients both in the immediate aftermath of surgery and longitudinally. Many complications are detectable via ultrasound evaluation with relative prevalence dependent on the time since surgery. It is critical for the practicing radiologist to recognize these complications to help guide appropriate treatment. Fundamental understanding of the procedure, including various surgical techniques is of great importance. In this article, the sonographic findings of the most common postoperative and long-term complications of renal transplantation are reviewed. As complications are highly related to surgical technique, the most common surgical techniques are presented first. Comprehensive ultrasound evaluation of the allograft is discussed next, followed by extensive review of the ultrasound findings of common complications. Finally, select recent advances in ultrasound are presented with their current and potential applications to renal transplant evaluation.

Application of a quality threshold to improve liver shear wave elastography measurements in free-breathing pediatric patients

PURPOSE

This study assessed the benefits of quality threshold (QT) implementation for liver shear wave elastography (SWE) in children during free breathing.

METHODS

The QT, which adjusts the SWE map display based on shear wave quality, was set at 55%. Phantom measurements (PMs) were taken with a fixed probe using QT (termed PM-1); a moving probe without QT (PM-2); and a moving probe with QT (PM-3). Each measurement was subjected to random samplings of various sizes. Clinical measurements (CMs) were obtained from children with biliary atresia using following protocols: CM-1, manually defined regions of interest (ROIs); CM-2, default ROIs without QT; and CM-3, default ROIs with QT. Elasticity measurements were compared across fibrosis grades, and color patterns on the SWE maps were analyzed.

RESULTS

In the phantom experiments, the moving probe produced lower elasticity measurements; this difference decreased upon QT application. With the moving probe, random sampling indicated fewer interquartile range-to-median ratios exceeding 30% upon QT application (4% vs. 14% when five values were sampled, P=0.004). In clinical experiments, QT improved the differentiation of fibrosis grade in patients over 5 years old, with a significant difference between moderate and severe fibrosis (P=0.004). Elasticity variability was positively correlated with fibrosis grade (τ=0.376, P<0.001). Certain apparent errors, termed artificial stripe patterns, were not eliminated by QT.

CONCLUSION

Applying QT to exclude low-quality pixels can minimize measurement error and improve differentiation of liver fibrosis grades. The presence of an artificial stripe pattern on the SWE map may indicate images requiring exclusion.

2D shear wave elastography for the assessment of quadriceps entheses-a methodological study

OBJECTIVE

To establish the scanning protocol for 2-dimensional shear wave elastography (SWE) on normal entheses by investigating the possible confounding factors that may increase the variability of measured elasticity.

MATERIAL AND METHODS

30 normal quadriceps entheses were scanned using SWE to compare the stiffness and coefficient variation by changing the ultrasonic coupling gel thickness, knee position, region of interest size, and scanning plane.

RESULTS

No significant difference in median shear wave velocity (SWV) was observed in different coupling gel thicknesses. The median SWV was higher in the knee flexion position than in the extended position (p < 0.001). Increased knee flexion led to stiffer quadriceps enthesis and higher SWV (ρ = 0.8, p < 0.001). The median SWV was higher when the diameter region of interest was 4.0 mm than 2.0 mm (p = 0.001). The median SWV was higher in the transverse plane than in the longitudinal plane (p < 0.001). Strong correlation was found between SWV and the degree of the shear wave to muscle fiber direction (ρ = 0.8, p < 0.001). The coefficient variation was lower in a gel thickness of 2.5 cm, with an extended knee, a region of interest of 2.0 mm, and a longitudinal plane (p > 0.05). For interobserver reliability for the proposed protocol, the intraclass correlation coefficients was 0.763.

CONCLUSION

In this study, we determined supine position with the knee extended; using 2.0 mm diameter region of interest and image acquisition at the longitudinal plane with thicker layer coupling gel seems most appropriate to reliably image healthy quadriceps entheses with SWE.

Ultrasound elastography in chronic kidney disease: a systematic review and meta-analysis

Ultrasound elastography (USE) is a noninvasive technique for assessing tissue elasticity, and its application in nephrology has aroused growing interest in recent years. The purpose of this article is to systematically review the clinical application of USE in patients with chronic kidney disease (CKD), including native and transplanted kidneys, and quantitatively investigate differences in elasticity values between healthy individuals and CKD patients. Furthermore, we provide a qualitative analysis of the studies included, discussing the potential interplay between renal stiffness, estimated glomerular filtration rate, and fibrosis. In January 2022, a systematic search was carried out on the MEDLINE (PubMed) database, concerning studies on the application of USE in patients with CKD, including patients with transplanted kidneys. The results of the included studies were extracted by two independent researchers and presented mainly through a formal narrative summary. A meta-analysis of nine study parts from six studies was performed. A total of 647 studies were screened for eligibility and, after applying the exclusion and inclusion criteria, 69 studies were included, for a total of 6728 patients. The studies proved very heterogeneous in terms of design and results. The shear wave velocity difference of - 0.82 m/s (95% CI: - 1.72-0.07) between CKD patients and controls was not significant. This result agrees with the qualitative evaluation of included studies that found controversial results for the relationship between renal stiffness and glomerular filtration rate. On the contrary, a clear relationship seems to emerge between USE values and the degree of fibrosis. At present, due to the heterogeneity of results and technical challenges, large-scale application in the monitoring of CKD patients remains controversial.

Comparison between Two-Dimensional and Point Shear Wave Elastography Techniques in Evaluating Liver Fibrosis Using Histological Staging as the Reference Standard: A Prospective Pilot Study

Evaluation of hepatic fibrosis is essential to prevent liver-related morbidity and mortality. Although various types of ultrasound shear wave elastography (SWE) have been used and validated, there are limited studies on the relatively newer technique, two-dimensional SWE (2D-SWE). Therefore, this study aimed to compare the diagnostic performances of 2D-SWE and point SWE (p-SWE) for evaluating liver fibrosis using histology as the reference standard. To measure liver stiffness (LS) values, 87 patients underwent 2D-SWE and p-SWE using the same machine. Technical failures and unreliable measurements were also evaluated. The diagnostic performances of 2D-SWE and p-SWE were compared using area under the receiver operating characteristic (AUROC) curve analysis. No technical failures were observed in either method; however, unreliable measurements were less frequent in 2D-SWE (1/87 [1.1%]) than in p-SWE (8/87 [9.2%]) (p < 0.001). The AUROC of the LS values of 2D-SWE were significantly higher than those of p-SWE for diagnosing significant fibrosis (0.965 vs. 0.872, p = 0.022) and cirrhosis (0.994 vs. 0.886, p = 0.042). In conclusion, 2D-SWE is more reliable and accurate than p-SWE for diagnosing hepatic fibrosis.

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.

Comparison Between Different Manufacturers' 2-D and Point Shear Wave Elastography Techniques in Staging Liver Fibrosis in Chronic Liver Disease Using Liver Biopsy as the Reference Standard: A Prospective Study

The purpose of this study was to assess the utility of 2-D shear wave elastography (SWE) in assessing liver fibrosis in patients with chronic liver disease by comparing its performance with that of point shear wave elastography (pSWE) using liver histological staging as the reference standard. In this ethics committee-approved, single-institution prospective study, pSWE and 2-D SWE velocity measurements were obtained in 121 adult patients (age: 18-70 y, median: 45 y) immediately before a liver biopsy for chronic liver disease. Shear wave velocity (SWV) and Ishak scores were compared using the Kruskal-Wallis test, Spearman's correlation and receiver operating characteristic (ROC) curve analysis. Youden's index was used to determine the optimal cutoff point. There was no technical failure using pSWE and 2-D SWE. The mean difference for SWV between pSWE and 2-D SWE was 0.0223 (limits of agreement: -1.1009, 1.1145). Values for both pSWE and 2-D SWE were significantly correlated with fibrosis stage (Spearman's ρ = 0.606, p < 0.0001; ρ = 0.722, p < 0.001 respectively). The area under the ROC curve differentiating F ≥3 was 0.855 (95% confidence interval: 0.778-0.932) for pSWE and 0.884 (95% CI: 0.817-0.951) for 2-D SWE. The AUC for differentiating F ≥5 was 0.890 (95% CI: 0.826-0.954) for pSWE and 0.926 (95% CI: 0.88-0.973) for 2-D SWE. This study indicates that 2-D SWE provides feasible and accurate assessment of liver fibrosis, comparable to that provided by pSWE from two different manufacturers' machines.

Evaluation of ultrasound point shear wave elastography reliability in an elasticity phantom

PURPOSE

To date, limited studies have specifically addressed the reliability of ultrasound point shear-wave elastography (pSWE). Therefore, the aim of the present study was to assess the reproducibility of ultrasound pSWE within and between operators using two ultrasound scanners.

METHODS

iU22 and EPIQ7 ultrasound scanners were used to assess the reliability of pSWE measurements of four inclusions [L I (8 kPa), L II (14 kPa), L III (48 kPa), and L IV (80 kPa)] at a depth of 3.5 cm in an elasticity phantom using a curvilinear 5-1 MHz transducer. The intraoperator, inter-operator, and inter-scanner reproducibility of pSWE was assessed using intraclass correlation coefficients (ICCs). Bland-Altman plots were used to establish bias and limits of agreement (LoA) between measurements. The accuracy of pSWE from manufacturer values was determined using the one-sample t-test.

RESULTS

Intra-operator agreement was excellent, with an ICC >0.90. The bias in measurements for operator A was -0.36±3.13 kPa (LoA, -6.47 to 5.75), and for operator B it was 1.97±6.29 kPa (LoA, -10.25 to 14.21). Inter-operator agreement was excellent, with an ICC of 0.95. The bias in measurements between operators was -0.42±5.00 kPa (LoA, -10.24 to 9.38). The inter-scanner agreement between EPIQ7 and iU22 was excellent, with an ICC of 0.96. The bias in measurements between scanners was 1.74±4.44 kPa (LoA, -6.95 to 10.45). There was significant overestimation for L I (17.75%) and L II (31.14%) and underestimation for L III (-15.28%) and L VI (-98.00%) relative to the manufacturer-reported values.

CONCLUSION

Phantom ultrasound pSWE was reproducible within and between operators, and between Philips ultrasound scanners; further studies using different ultrasound systems and transducers are required.

Comparison of superb microvascular imaging and shear wave elastography for assessing liver fibrosis in chronic hepatitis B

Purpose

The present study investigated the effectiveness and applicability of superb microvascular imaging (SMI) in determining the degree of liver fibrosis noninvasively in comparison with shear wave elastography (SWE).

Methods

Ninety-eight consecutive patients with chronic hepatitis B who underwent ultrasound (US)-guided needle biopsy were examined using US combined with SMI and SWE. The predictive performance of the two US techniques in staging liver fibrosis and inflammation was compared with reference to the histological findings obtained from liver biopsy. The intraobserver and interobserver reproducibility of SMI in vascularity scores were evaluated.

Results

SWE values and SMI vascular scores were statistically significantly different among fibrosis stages (χ²(3)=76.3, χ²(3)=81.5, P<0.001). The SWE and SMI models significantly predicted fibrosis stages separately, and SMI scores alone predicted fibrosis stages better than SWE values (50.1% for SWE, 63.5% for SMI, P<0.001). A model with both SMI scores and SWE values together explained 73.2% of variance in fibrosis stages. When other clinical and laboratory predictors were added to the model (81.5%, P<0.001), SWE values and SMI scores remained the main predictors of fibrosis stages. SWE and SMI were also applicable in predicting inflammatory grades, explaining 31% and 34% of variance, respectively, and 37.7% when used together (P<0.001).

Conclusion

Both SWE and SMI had good diagnostic performance in determining the degree of liver fibrosis in chronic hepatitis B patients. The efficacy of SMI was better than that of SWE. SMI can improve diagnostic performance for staging liver fibrosis and shows potential for estimating necroinflammation of the liver.

Diagnostic Performance of 2-D Shear Wave Elastography on the Evaluation of Hepatic Fibrosis with Emphasis on Impact of the Different Region-of-Interest Methods

The purpose of this study was to evaluate the impact of the different region-of-interest (ROI) methods of 2-D shear wave elastography (2-D SWE) on hepatic fibrosis diagnosis. In this retrospective study, 83 patients who underwent 2-D SWE with three ROI methods (a circle ROI, a box ROI and multiple ROIs in an elastogram) and transient elastography (TE) were included. Liver stiffness (LS) was measured five times with each ROI method. These LS values were compared, and their correlation with those obtained from TE was evaluated. The LS values obtained using the three different ROI methods differed statistically (p < 0.001). However, the LS values obtained using each ROI method of 2-D SWE were highly correlated with those obtained using TE (r > 0.7, p < 0.001). All three ROI methods of 2-D SWE had high areas under the receiver operating characteristic curve in diagnosing significant fibrosis and cirrhosis (0.841, 0.820 and 0.840, respectively; 0.962, 0.946 and 0.945, respectively). There were no significant differences in area under the receiver operating characteristic curve among the ROI methods of 2-D SWE. Regardless of the ROI method, 2-D SWE had high performance in diagnosing hepatic fibrosis.

Effects of Confounding Factors on Liver Stiffness in Two-Dimensional Shear Wave Elastography in Beagle Dogs

Background

Two-dimensional shear wave elastography (2D-SWE) is a powerful technique that can non-invasively measure liver stiffness to assess hepatic fibrosis.

Purpose

This study aimed to identify the effects of confounding factors, including anesthesia, breathing, and scanning approach, on liver stiffness when performing 2D-SWE in dogs.

Materials and Methods

Nine healthy Beagle dogs were included in this study. Hepatic 2D-SWE was performed, and liver stiffness was compared between conscious and anesthetized states, free-breathing and breath-holding conditions, and intercostal and subcostal approaches. For the anesthetized state, the breath-holding condition was subdivided into seven phases, which included forced-expiration (5 and 10 mL/kg), end-expiration (0 cm H₂O), and forced-inspiration (5, 10, 15, and 20 cm H₂O), and liver stiffness was compared among these phases. Changes in liver stiffness were compared between intercostal and subcostal approaches according to breathing phases.

Results

No significant difference was observed in liver stiffness between the conscious and anesthetized states or between the free-breathing and breath-holding conditions. No significant difference was noted in liver stiffness among the breathing phases, except for forced-inspiration with high airway pressure (15 and 20 cm H₂O in the intercostal approach and 10, 15, and 20 cm H₂O in the subcostal approach), which was associated with significantly higher liver stiffness (p < 0.05). Liver stiffness was significantly higher in the subcostal approach than in the intercostal approach (p < 0.05). Changes in liver stiffness were significantly higher in the subcostal approach than in the intercostal approach in all forced-inspiratory phases (p < 0.05).

Conclusion

In conclusion, when performing 2D-SWE in dogs, liver stiffness is unaffected by anesthesia and free-breathing. To avoid inadvertent increases in liver stiffness, the deep inspiratory phase and subcostal approach are not recommended. Thus, liver stiffness should be interpreted considering these confounding factors.

Non-invasive tools for detection of liver disease in children and adolescents with cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is a multi-organ genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene which encodes the CFTR protein. CF-associated liver disease (CFLD) is a common complication; diagnosis is based on clinical, laboratory findings and abdominal imaging. However, non-invasive diagnostic approaches are needed to early detect CFLD, its progression and severity. Recent studies demonstrate a possible role of point shear wave elastography (p-SWE) with liver stiffness measurement (LSM) as a tool for CFLD diagnosis also in children. This non-invasive technique measures liver stiffness to assess liver fibrosis and is suggested to be less operator-dependent compared to ultrasonography. Aim of our prospective observational study is to investigate the role of p-SWE with LSM for CFLD diagnosis in children and adolescents with CF and to compare this finding with aspartate aminotransferase to platelet ratio index (APRI), fibrosis index based on four factors (FIB-4) and gamma-glutamyl-transpeptidase to platelet ratio (GPR) indices.

METHODS

Fifty-nine children with CF, who had routinely undergone abdominal imaging, were consecutively enrolled. Laboratory findings and clinical data were recorded, as abdominal ultrasound and shear wave elastography at baseline. The cases were divided into two groups based on collected data and classified as CFLD and CFnoLD (without liver disease) according to Debray criteria. APRI, FIB-4 and GPR fibrosis indices were also evaluated.

RESULTS

Twenty-four/59 (40.7%) were defined as CFLD. LSM test is superior to the APRI (P<0.001), the FIB-4 test (P=0.001) and the GPR test for early detection of liver fibrosis. LSM had an area under receiver operating characteristic (ROC) curve =0.818 (95% CI: 0.702-0.934) compared with APRI (0.571, 95% CI: 0.421-0.722), FIB-4 (0.656, 95% CI: 0.511-0.801) and GPR (0.632, 95% CI: 0.485-0.779). At a cut-off of ≥6.2 LSM show a sensitivity of 75.0% and a specificity of 88.6%.

CONCLUSIONS

LSM by transient p-SWE is a non-invasive, highly accessible, reliable, and reproducible test that can be used to assess early detection of liver fibrosis and its severity in children and adolescents with CF, limiting the use of liver biopsy. These preliminary observations point to the need of larger study population to confirm our data.

Liver stiffness quantification in biopsy-proven nonalcoholic fatty liver disease patients using shear wave elastography in comparison with transient elastography

Purpose

This study prospectively assessed the performance of liver stiffness measurements using point shear-wave elastography (p-SWE) in comparison with transient elastography (TE) in patients with biopsy-proven nonalcoholic fatty liver disease (NAFLD).

Methods

Fifty-six consecutive adult patients with a histological diagnosis of NAFLD prospectively underwent TE and p-SWE on the same day. The median of 10 measurements (SWE-10), the first five (SWE-5), and the first three (SWE-3) measurements were analyzed for p-SWE. Liver biopsy was considered as the reference standard for liver fibrosis grade. Receiver operating characteristic (ROC) curves and areas under the ROC curves (AUROCs) were calculated to assess the performance of TE and p-SWE for the diagnosis of significant (F2-F4) and advanced fibrosis (F3-F4).

Results

Forty-six patients (27 men, 19 women; mean age, 54.7±9.1 years) had valid p-SWE and TE measurements. Twenty-seven patients (58.7%) had significant fibrosis and 18 (39.1%) had advanced fibrosis. For significant fibrosis, both SWE-10 (AUROC, 0.787; P=0.002) and SWE-5 (AUROC, 0.809; P=0.001) provided higher diagnostic performance than TE (AUROC, 0.719; P=0.016) and SWE-3 (AUROC, 0.714; P=0.021), albeit without statistical significance (P=0.301). For advanced fibrosis, SWE-5 showed higher diagnostic performance (AUROC, 0.809; P<0.001) than TE (AUROC, 0.799; P<0.001), SWE-10 (AUROC, 0.797; P<0.001), and SWE-3 (AUROC, 0.736; P=0.003), although the differences were not statistically significant (P=0.496). The optimal SWE-10 and SWE-5 cutoff values were ≥8.4 and ≥7.8 for significant fibrosis, and ≥9.1 and ≥8.8 for advanced fibrosis, respectively.

Conclusion

TE and p-SWE showed similar performance for the diagnosis of significant and advanced fibrosis in NAFLD patients.