Normal liver stiffness in healthy adults assessed by real-time shear wave elastography and factors that influence this method

Macro-indentation testing of soft biological materials and assessment of hyper-elastic material models from inverse finite element analysis

Mechanical characterization of hydrogels and ultra-soft tissues is a challenging task both from an experimental and material parameter estimation perspective because they are much softer than many biological materials, ceramics, or polymers. The elastic modulus of such materials is within the 1 - 100 kPa range, behaving as a hyperelastic solid with strain hardening capability at large strains. In the current study, indentation experiments have been performed on agarose hydrogels, bovine liver, and bovine lymph node specimens. This work reports on the reliable determination of the elastic modulus by indentation experiments carried out at the macro-scale (mm) using a spherical indenter. However, parameter identification of the hyperelastic material properties usually requires an inverse finite element analysis due to the lack of an analytical contact model of the indentation test. Hence a comprehensive study on the spherical indentation of hyperelastic soft materials is carried out through robust computational analysis. Neo-Hookean and first-order Ogden hyperelastic material models were found to be most suitable. A case study on known anisotropic hyperelastic material showed the inability of the inverse finite element method to uniquely identify the whole material parameter set.

Feasibility and Measurement Value of Pancreatic 2-D Shear Wave Elastography in Healthy Adults: Evaluation, Influencing Factors, Reference Range, Measurement Stability and Reproducibility

OBJECTIVE

The present study was aimed at assessing the success rate and measurement value, determining the influencing factors and reference range and examining the intra-operator stability and inter-operator reproducibility of pancreatic 2-D shear wave elastography (SWE) measurement in healthy adults.

METHODS

In 2022, 387 healthy adults were prospectively recruited. Logistic regression and linear regression analyses were used to explore the factors influencing the success rate and the measurement value of pancreatic 2-D SWE measurement, respectively. A two-sided 95% reference range was estimated accordingly. The intraclass correlation coefficient was calculated to evaluate the intra-operator stability and inter-operator reproducibility of the pancreatic 2-D SWE measurement.

RESULTS

The pancreatic body (89.6%) bore the highest while the tail (72.8%) bore the lowest success rate of pancreatic 2-D SWE measurement. Sex and body mass index (BMI) were the independent factors influencing measurement success rate in all three parts of the pancreas. Mean measurement values (Emean) were not the same in the three parts of the pancreas of the same participant. BMI and image depth were the independent factors influencing Emean in the pancreatic body, while region of interest depth and BMI were the only independent factors influencing Emean in the pancreatic head and tail, respectively. The intra-operator stability of pancreatic 2-D SWE measurement was found to be excellent, whereas its inter-operator reproducibility was poor to good.

CONCLUSION

Pancreatic 2-D SWE is a reliable technique for evaluating pancreatic stiffness in healthy adults, but its success rate and measurement value are influenced by multiple factors.

Obesity and Body Composition in Relation to Liver and Kidney Ultrasound Elastography in Paediatric Patients with Either Hypertension or Chronic Kidney Disease

(1) Background: Ultrasound elastography is a novel ultrasound technique for evaluating tissue elasticity. One of the key factors influencing the measurement in children is excess weight. This study aimed to evaluate the effect of body composition, namely, fat mass, on liver and kidney ultrasound elastography in paediatric patients. (2) Methods: 114 participants, in whom bioimpedance, along with liver and kidney ultrasound elastography, were performed, were included (37 patients with chronic kidney disease, 46 patients with hypertension, and 31 healthy subjects). (3) Results: Bioimpedance analysis showed a significant correlation between liver elastography parameters and the phase angle (p = 0.002), fat-free mass (p = 0.001), body cell mass (p = 0.001), total body water (p = 0.001), extracellular water (p = 0.006), and, to lesser extent, fat mass (p = 0.041). On the contrary, kidney elastography parameters strongly correlated only with fat mass (p < 0.001 for both kidneys). (4) Conclusions: Liver and kidney stiffness increased in overweight participants and showed significant correlation with fat mass, particularly in the case of kidney elastography.

Evaluation of Liver and Spleen With Shear Wave Elastography in Adult Patients With Familial Mediterranean Fever

ABSTRACT

Familial Mediterranean fever (FMF) is an autoinflammatory disease and an important health problem in countries bordering the eastern Mediterranean, including Turkey. In this study, we aimed to evaluate possible tissue stiffness changes that may develop in the liver and spleen in adult FMF patients with shear wave elastography (SWE), and its usability as an auxiliary imaging method that will be able to provide additional advantage in clinical follow-up. Seventy-five adult FMF patients and 73 adult volunteer were included in the study. Examination was performed through an intercostal space where the liver and spleen were clearly visible. The parenchymal stiffness degrees of the liver and spleen were quantified by shear modulus values in kilopascals. Differences in stiffness values of the liver and spleen between the 2 groups were examined. Liver stiffness value (LSV) was found to be statistically significantly higher in the FMF group. Although the spleen stiffness value (SSV) was found higher in the FMF group, the difference between the groups was not statistically significant. Increased LSVs in patients with FMF can be quantitatively demonstrated by the 2-dimensional SWE method, and SWE may be useful as an auxiliary imaging method in the follow-up of patients with FMF for this purpose. The LSV and SSV obtained in this study may be useful as reference stiffness values for both healthy individuals and those with FMF.

Validation of attenuation imaging coefficient, shear wave elastography, and dispersion as emerging tools for non-invasive evaluation of liver tissue in children

Introduction

The number of children with acute and chronic liver disease is rising. Moreover, liver involvement may be limited to subtle changes in organ texture especially in early childhood and some syndromic conditions, such as ciliopathies. Attenuation imaging coefficient (ATI), shear wave elastography (SWE), and dispersion (SWD) are emerging ultrasound technologies providing data about attenuation, elasticity, and viscosity of liver tissue. This additional and qualitative information has been correlated with certain liver pathologies. However, limited data are available for healthy controls and have mainly been raised in adults.

Methods

This prospective monocentric study was conducted at a university hospital with a specialization in pediatric liver disease and transplantation. Between February and July 2021, 129 children aged 0-17.92 years were recruited. Study participants attended outpatient clinics due to minor illnesses excluding liver or cardiac diseases, acute (febrile) infections or other conditions affecting liver tissue and function. ATI, SWE, and SWD measurements were performed on an Aplio i800 (Canon Medical Systems) with an i8CX1 curved transducer by two different investigators with long-standing experience in pediatric ultrasound according to a standardized protocol.

Results

Considering multiple potential covariates, we derived percentile charts for all 3 devices relying on the Lambda-Mu-Sigma (LMS) approach. 112 children were considered for further analysis, excluding those with abnormal liver function and under-/overweight (BMI SDS<-1.96/> 1.96, respectively). Age range was 0-17.92 years (mean 6.89±0.50SD), 58% were male. The mean duration of the ultrasound examination (basic ultrasound plus SWE, SWD, and ATI) was 6.67±0.22 minutes and it was well tolerated in 83% (n=92) of cases. While ATI was related to age, SWD was found to depend on BMI SDS, and SWE on abdominal wall thickness and sex. ATI correlated with neither SWE nor SWD, but SWE was correlated with SWD.

Conclusions

Our study provides norm values and reference charts for ATI, SWE, and SWD considering important covariates including age, sex and, BMI. This may help to implement these promising tools into imaging diagnostics of liver disease and to improve the diagnostic relevance of liver ultrasound. In addition, these noninvasive techniques proved to be time-effective and highly reliable, which make them ideal for application in children.

Noninvasive Assessment of Liver Fibrosis and Inflammation in Chronic Hepatitis B: A Dual-task Convolutional Neural Network (DtCNN) Model Based on Ultrasound Shear Wave Elastography

BACKGROUND AND AIMS

Liver stiffness (LS) measured by shear wave elastography (SWE) is often influenced by hepatic inflammation. The aim was to develop a dual-task convolutional neural network (DtCNN) model for the simultaneous staging of liver fibrosis and inflammation activity using 2D-SWE.

METHODS

A total of 532 patients with chronic hepatitis B (CHB) were included to develop and validate the DtCNN model. An additional 180 consecutive patients between December 2019 and April 2021 were prospectively included for further validation. All patients underwent 2D-SWE examination and serum biomarker assessment. A DtCNN model containing two pathways for the staging of fibrosis and inflammation was used to improve the classification of significant fibrosis (≥F2), advanced fibrosis (≥F3) as well as cirrhosis (F4).

RESULTS

Both fibrosis and inflammation affected LS measurements by 2D-SWE. The proposed DtCNN performed the best among all the classification models for fibrosis stage [significant fibrosis AUC=0.89 (95% CI: 0.87-0.92), advanced fibrosis AUC=0.87 (95% CI: 0.84-0.90), liver cirrhosis AUC=0.85 (95% CI: 0.81-0.89)]. The DtCNN-based prediction of inflammation activity achieved AUCs of 0.82 (95% CI: 0.78-0.86) for grade ≥A1, 0.88 (95% CI: 0.85-0.90) grade ≥A2 and 0.78 (95% CI: 0.75-0.81) for grade ≥A3, which were significantly higher than the AUCs of the single-task groups. Similar findings were observed in the prospective study.

CONCLUSIONS

The proposed DtCNN improved diagnostic performance compared with existing fibrosis staging models by including inflammation in the model, which supports its potential clinical application.

Intestinal Elastography in the Diagnostics of Ulcerative Colitis: A Narrative Review

Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) that mainly affects developed countries, but the number of cases in developing countries is increasing. We conducted a narrative review on the potential application of ultrasound elastography in the diagnosis and monitoring of UC, as this newly emerging method has promising results in other gut diseases. This review fulfilled the PRISMA Statement criteria with a time cut-off of June 2022. At the end of the review, of the 1334 identified studies, only five fulfilled all the inclusion criteria. Due to the small number of studies in this field, a reliable assessment of the usefulness of ultrasound elastography is difficult. We can only conclude that the transabdominal elastography examination did not significantly differ from the standard gastrointestinal ultrasonography examination and that measurements of the frontal intestinal wall should be made in the longitudinal section. The reports suggest that it is impossible to estimate the clinical scales used in disease assessment solely on the basis of elastographic measurements. Due to the different inclusion criteria, measurement methodologies, and elastographic techniques used in the analysed studies, a reliable comparative evaluation was impossible. Further work is required to assess the validity of expanding gastrointestinal ultrasonography with elastography in the diagnosis and monitoring of UC.

The role of shear wave elastography in the assessment of placentas in healthy pregnancy women during third-trimester: A preliminary study

OBJECTIVE

The study aimed to analysis the elasticity value of placenta in healthy women during third trimester by shear wave elastography (SWE), and tried to investigate the relationship between clinical characteristics and placental elasticity.

METHODS

Singleton healthy pregnant women who had routine ultrasound examination between 28 and 37 weeks were enrolled. SWE of the frontier placentas were evaluated by transabdominal ultrasound elastography. Only placentas at front wall were enrolled. The placenta was divided into three areas for SWE examination: the central area (Area A), the periphery area (Area B) and the area between central and edge of placenta (Area C). Then, the subjects with normal delivery were evaluated and analyze the relationship between clinical features and placental elasticity.

RESULTS

A total of 43 pregnant women were included in this study. The mean value of SWE in the central area was 5.67±2.51 kPa. And it was 6.50±2.57 kPa in the periphery area, 5.17±2.25 kPa in the area C. There were no significant differences except area B and C. In different age group, there were no significant differences except area C. The history of childbearing and uterine operation and the gestational age were no significant correlation with the SWE value of placenta. There were also no significant differences between birth weight percentile and placental elasticity.

CONCLUSION

The placental elasticity is stable in healthy women during third trimester. Shear wave elastography is helpful to assess the placental elasticity and can be used as a supplemental technique to existing methods for monitoring the placental function. But the normal elasticity range in some certain areas of placenta should be confirmed by further study.

Liver stiffness and prediction of cardiac outcomes in patients with acute decompensated heart failure

BACKGROUND

In acute decompensated heart failure (ADHF), noninvasive markers that predict morbidity and mortality are limited. Liver stiffness measurement (LSM) increases with hepatic fibrosis; however, it may be falsely elevated in patients with ADHF in the absence of liver disease. We investigated whether elevated LSM predicts cardiac outcomes in ADHF.

METHODS

In a prospective study, we examined 52 ADHF patients without liver disease between 2016 and 2017. Patients underwent liver 2D shear wave elastography (SWE) and were followed for 12 months to assess the outcomes of left ventricular assist device (LVAD), heart transplant (HT) or death.

RESULTS

The median LSM was elevated in patients who received an LVAD or HT within 30-days compared to those who did not (median [IQR]: 55.6 [22.5 - 63.4] vs 13.8 [9.5 - 40.3] kPa, p = .049). Moreover, the risk of composite outcome was highest in the 3rd tertile (> 39.8 kPa compared to 1^st and 2^nd combined, HR 2.83, 95% CI 1.20- 6.67, p = .02). Each 1-kPa increase in LSM was associated with a 1%-increase in the incidence rate of readmissions (IRR 1.01, 95% CI 1.00-1.02, p = .01).

CONCLUSIONS

LSM may serve as a novel noninvasive tool to determine LVAD, HT, or death in patients with ADHF.

Effect of Q-Box size on liver stiffness measurement by two-dimensional shear wave elastography

PURPOSE

To investigate the effect of the Q-Box size on liver stiffness (LS) measurement by two-dimensional shear wave elastography (2D SWE).

METHODS

Ninety-eight patients with chronic liver disease were enrolled. Each patient was continuously measured five times. The Q-Box diameter was adjusted to 10, 20, and 30 mm each time. The liver stiffness values (LSVs) at different diameters were compared in the following groups: LSVs ≤6.2 kPa, 6.2 kPa < LSVs ≤11 kPa, LSVs >11 kPa. The reliability and repeatability of LS measurement at different diameters were evaluated.

RESULTS

The differences in LSVs at different Q-Box diameters were statistically significant only when LSV ≤6.2 kPa (p = 0.004). There were no statistically significant differences in standard deviation (SD), SD/median, coefficient of variation (CV), and interquartile range (IQR)/median at different Q-Box diameters (p > 0.05). There were statistical differences in minimum LSVs and percentage of minimum LSVs ≤0.2 kPa as well as in stability index (SI) and percentage of SI <90% at different Q-Box diameters (p < 0.05). The intraclass correlation coefficients (ICCs) were up to 0.98 at Q-Box diameters of 10, 20, and 30 mm.

CONCLUSIONS

Our study showed that Q-Box size may lead to significant differences in LSVs, especially when LSVs ≤6.2 kPa. The Q-Box size had a large effect on the reliability of a single LS measurement but did not affect the repeatability of multiple measurements.

The impact of body position and exercise on the measurement of liver Young's modulus by real-time shear wave elastography

BACKGROUND

In the past ten years, liver biopsies have been used as a method to accurately diagnose the stage of fibrosis.

OBJECTIVE

This study aimed to evaluate whether body position and exercise affect the measurement of liver Young's modulus of healthy volunteers by real-time shear wave elastography (RT-SWE).

METHODS

RT-SWE was used to measure liver Young's modulus in the supine and left lateral positions of 70 healthy volunteers at rest and measure the liver Young's modulus in the lying position before exercise, and at zero, five, and ten minutes of rest after exercise.

RESULTS

The liver Young's modulus in the left lateral position was significantly higher than in the supine position (P< 0.05), and the measured value in the supine position was more stable than the left lateral position. The liver Young's modulus measured at zero minutes after exercise was significantly higher than that measured before exercise (P< 0.05). The liver Young's modulus measured at five minutes after exercise was significantly higher than that measured at zero minutes after exercise (P<0.05) and was not statistically different from the measured value before exercise (P> 0.05). The liver Young's modulus measured at ten minutes after exercise was significantly higher from that measured at zero minutes after exercise (P< 0.05) and was not statistically different from the measured value at five minutes after exercise (P> 0.05).

CONCLUSION

Body position and exercise have a significant impact on the measurement of liver Young's modulus. It is recommended that the examinees take a supine position during the measurement, and measurement should be conducted at least ten minutes after exercise.

Utility of Hepatic 2D Shear-Wave Elastography in Monitoring Response to Image-Guided Intervention in Children With Chronic Budd-Chiari Syndrome: A Prospective Study

Background: Image-guided interventions for Budd-Chiari syndrome (BCS) reduce hepatic congestion, thereby reducing liver stiffness. Liver stiffness measurements (LSM) by ultrasound may provide a noninvasive marker for assessing treatment response. Objective: To assess the utility of 2D shear-wave elastography (SWE) for monitoring response to image-guided intervention in children with BCS, with attention to changes in LSM in patients with disease recurrence. Materials and Methods: This prospective study included children with chronic BCS and planned image-guided intervention. Color Doppler ultrasound (CDUS) and 2D SWE were performed at baseline; at 24 hours, one month, and three months after intervention; and thereafter every three months or at the time of clinically suspected recurrence. Eighteen children underwent liver biopsy at the time of intervention for fibrosis staging using METAVIR criteria. Disease recurrence was diagnosed by CDUS. Statistical evaluation was performed using non-parametric tests. Results: A total of 32 children (28 boys, 4 girls; mean age: 9.0 years; range: 3-14 years) were included. Median LSM was at baseline 43.7 kPa [interquartile range (IQR): 33.0-65.4), at 24 hours 22.5 kPa (IQR: 16.8-32.0), at one month 18.7 kPa (IQR: 14.2-32.0), and at three months 16.7 kPa (IQR: 11.5-22.5) (p<.05 for all post-intervention time points vs baseline). Nine (28.1%) patients developed recurrence after intervention at mean of 4.4 months. In one patient with recurrence, LSM was higher at 24 hours (52.3 kPa) than at baseline (44.2 kPa). In the remaining eight patients with recurrence, LSM increased at the time of recurrence compared with the prior post-intervention LSM measurement [median absolute increase of 11.0 kPa (IQR: 6.1-24.4 kPa)]. Fibrosis stage was not significantly correlated with baseline LSM (r=0.11, 95% CI: -0.37, 0.54; p=.51) or 24-hour post-intervention LSM (r=0.39, 95% CI: -0.11, 0.73; p=.11). Conclusion: LSM decreased significantly after image-guided intervention for chronic BCS in children, showing a maximal decrease at 24 hours post-intervention. Disease recurrence was typically associated with an increase in LSM compared with the patient's prior measurement. Clinical Impact: LSM obtained by 2D SWE may serve as a useful quantitative adjunct to CDUS in monitoring children with chronic BCS for disease recurrence after percutaneous interventional treatment.

Association of shear-wave elastography with clinical outcomes post-liver transplantation

PURPOSE

Two-dimensional shear-wave elastography (2D-SWE) assessment of liver stiffness has the advantage of being obtained during conventional ultrasound. Liver-stiffness values on 2D-SWE for grafted livers are unknown, as are their potential link to post-transplantation morbidity. This study was undertaken to determine liver-stiffness values on 2D-SWE for grafted livers without complications, and examine relationships between liver-stiffness values on 2D-SWE and early post-operative arterial or biliary complications.

METHODS

In our facility, all liver-transplant recipients are entered in a comprehensive surgical database, where donor, procedure and recipient characteristics are described. All patients underwent systematic 2D-SWE assessment. Potential relationships were analyzed between liver-stiffness findings and donor, procedure and recipient characteristics, and follow-up events, including death, arterial or biliary complications, graft removal and allograft-dysfunction scores.

RESULTS

Liver-stiffness values on 2D-SWE of 337 ultrasound examinations from 165 liver-transplant recipients were collected retrospectively. Median time from transplantation to 2D-SWE examination was 149 days, with median follow-up at 36 months. The mean±SD stiffness value for grafts without complications was 7.3±2.3kPa; it was significantly higher during the first 90 days (8.2±2.5kPa) post-transplant than after 1year (7.0±2.4kPa) (P=0.01). Patients with biliary complications during the first-year post-transplantation had significantly higher mean liver-stiffness values on 2D-SWE than those without, respectively: 9.8±7.0 vs 7.5±1.8kPa (P=0.01).

CONCLUSIONS

Post-transplantation patients without complications had stiffer livers than the general population, with higher values during the first 90 days after surgery. Liver-stiffness values on 2D-SWE were significantly higher for patients with biliary, but not arterial, complications.

Quantitative Ultrasound Elastography Methods in Focal Liver Lesions Including Hepatocellular Carcinoma: From Diagnosis to Prognosis

ABSTRACT

The ability of ultrasound elastography to diagnose focal liver lesions and determine their prognoses including hepatocellular carcinoma (HCC) is unclear. At present, radiofrequency ablation and liver resection are the most common treatments for HCC. However, the survival rate remains disappointing because of recurrences and postoperative liver failure, necessitating the development of noninvasive approaches. There is currently no systematic definition of an elastic technique for measuring liver stiffness to predict the recurrence of HCC after radiofrequency ablation and postoperative liver failure. In this review, recent advances in ultrasound elastography for the diagnosis and prognosis of focal liver lesions are discussed including HCC.

Intra-System Reliability Assessment of 2-Dimensional Shear Wave Elastography

The availability of 2-Dimensional Shear Wave Elastography (2D-SWE) technology on modern medical ultrasound systems is becoming increasingly common. The technology is now being used to investigate a range of soft tissues and related pathological conditions. This work investigated the reliability of a single commercial 2D-SWE system using a tissue-mimicking elastography phantom to understand the major causes of intra-system variability. Sources of shear wave velocity (SWV) measurement variability relates to imaging depth, target stiffness, sampling technique and the operator. Higher SWV measurement variability was evident with increasing depth and stiffness of the phantom targets. The influence of the operator was minimal, and variations in sampling technique had little impact on the SWV.

Normal values of combinational elastography in adult liver: the influence of age

PURPOSE

We aimed to clarify the normal values obtained by simultaneous use of shear wave imaging and strain imaging (combinational elastography) in liver and reveal how aging influences them.

METHODS

In our checkup center, 257 examinees were diagnosed with normal liver based on questionnaires about liver disease and their drinking history, liver function test results, and ultrasound B-mode study findings. We estimated the values of combinational elastography and considered the correlation between the values and age. A multivariate analysis was performed concerning several features and the liver fibrosis (LF) index. We divided examinees into a younger group (< 65 years old) and an older group (≥ 65 years old), and assessed the effect of age on the LF index.

RESULTS

The mean shear wave velocity (Vs) of shear wave measurement (SWM) was 1.10 ± 0.17 m/s (range 0.84-1.93), and the mean LF index of real-time tissue elastography (RTE) was 1.371 ± 0.458 (range 0.258-3.173). There was no significant correlation between Vs and age. However, the LF index increased significantly with age. The multivariate analysis showed that age (P < 0.001) and BMI (P < 0.05) significantly affected the LF index. Indeed, the LF index in the older group was significantly higher than that in the younger group (P < 0.001).

CONCLUSION

In adult liver, the normal Vs of SWM was 1.10 ± 0.17 m/s, and the normal LF index of RTE was 1.371 ± 0.458. The LF index increased significantly with age in contrast to Vs; therefore, the influence of age should be considered when using combinational elastography.

A review of physical and engineering factors potentially affecting shear wave elastography

It has been recognized that tissue stiffness provides useful diagnostic information, as with palpation as a screening for diseases such as cancer. In recent years, shear wave elastography (SWE), a technique for evaluating and imaging tissue elasticity quantitatively and objectively in diagnostic imaging, has been put into practical use, and the amount of clinical knowledge about SWE has increased. In addition, some guidelines and review papers regarding technology and clinical applications have been published, and the status as a diagnostic technology is in the process of being established. However, there are still unclear points about the interpretation of shear wave speed (SWS) and converted elastic modulus in SWE. To clarify these, it is important to investigate the factors that affect the SWS and elastic modulus. Therefore, physical and engineering factors that potentially affect the SWS and elastic modulus are discussed in this review paper, based on the principles of SWE and a literature review. The physical factors include the propagation properties of shear waves, mechanical properties (viscoelasticity, nonlinearity, and anisotropy), and size and shape of target tissues. The engineering factors include the region of interest depth and signal processing. The aim of this review paper is not to provide an answer to the interpretation of SWS. It is to provide information for readers to formulate and verify the hypothesis for the interpretation. Therefore, methods to verify the hypothesis for the interpretation are also reviewed. Finally, studies on the safety of SWE are discussed.

The Performance of a 2-Dimensional Shear-Wave Elastography Technique for Predicting Different Stages of Liver Fibrosis Using Transient Elastography as the Control Method

ABSTRACT

The aim was to evaluate the performance of 2-dimensional (2D) shear-wave elastography from general electric (2D SWE-GE), implemented on the new LOGIQ S8 system, for the noninvasive assessment of liver fibrosis, and to identify liver stiffness (LS) cutoff values for predicting different stages of fibrosis using transient elastography (TE) as the control method. We included 179 consecutive subjects, with or without chronic hepatopathies, in whom LS was evaluated in the same session using 2 elastographic techniques: TE (FibroScan, EchoSens) and 2D SWE-GE (LOGIQ S8; GE Healthcare, Chalfont St Giles, United Kingdom). Reliable LS measurements were defined for TE: the median value of 10 measurements with a success rate of 60% or greater and an interquartile range/median ratio (IQR/M) < 0.30; for 2D SWE-GE: the median value of 10 measurements acquired in a homogenous area and IQR/M < 0.30. To discriminate between fibrosis stages by TE, we used the following cutoffs: F2-7; F3-9.5 and F4-12 kPa. Reliable LS measurements were obtained in 97.2% subjects by 2D SWE-GE and in 98.3% by TE (P = 0.72), so that 171 subjects were included for the final analysis. A good correlation was found between the LS values obtained by the 2 methods (r = 0.72, P < 0.0001). The best 2D SWE-GE cutoff value for F ≥ 2 was 6.9 kPa (areas under receiver operating characteristic [AUROC], 0.93; sensitivity, 85.8%; specificity, 90.2%), for F of 3 or greater, it was 8.2 kPa (AUROC, 0.93; sensitivity, 87.5%; specificity, 86.8%) and for F value of 4, it was 9.3 kPa (AUROC, 0.91; sensitivity, 85.7%; specificity, 81.2%). In conclusion, the best 2D SWE-GE (S8) cutoff values for predicting F2, F ≥ 3 and F = 4 were 6.9, 8.2, and 9.3 kPa.

Ultrasound-based liver elastography: current results and future perspectives

Chronic liver disease affects 185 million population worldwide. It encompasses a heterogenous disease spectrum, but all can lead to the development of liver fibrosis. The degree of liver fibrosis is not only a prognosticator, but has also been used to guide the treatment strategy and to evaluate treatment response. Traditionally, staging of liver fibrosis is determined on histological analysis using samples obtained from an invasive liver biopsy. Ultrasound-based liver elastography is a non-invasive method of assessing diffuse liver disease in patients with known chronic liver disease. The use of liver elastography has led to a significant reduction in the number of liver biopsies performed to assess the severity of liver fibrosis and a liver biopsy is now reserved for only select sub-groups of patients. The aim of this review article is to discuss the key findings and current evidence for ultrasound-based elastography in diffuse liver disease as well as the technical challenges and to evaluate the potential research direction.

Liver Elastography in Primary Sclerosing Cholangitis Patients Using Three Different Scanner Systems

The aim of the study described here was to characterize three different liver elastography methods in primary sclerosing cholangitis (PSC) patients, for the first time exploring 2-D shear wave elastography (2-D-SWE) in PSC patients and its putative advantages over point shear wave elastography (pSWE). Sixty-six adult PSC patients (51 males, 77%) underwent liver elastography: Transient elastography (TE), pSWE and 2-D-SWE were applied head-to-head after B-mode ultrasonography and blood tests. Liver stiffness measurements (LSMs) by pSWE yielded lower values than those by TE; 2-D-SWE had less steep slope but was overall not significantly different from TE. Correlation between LSMs by pSWE and TE was excellent (intraclass correlation coefficient = 0.92); correlation for 2-D-SWE with either pSWE or TE was moderate but improved with exclusion of overweight individuals. LSMs correlated with the Enhanced Liver Fibrosis test (ELF) across all scanner systems. Our study indicates that LSM by different systems is feasible in PSC patients and that 2-D-SWE tends to underestimate stiffness compared with TE.

Does Operator Experience and the Q-Box Diameter Affect the Repeatability of Liver Stiffness Measurements Obtained by 2-Dimensional Shear Wave Elastography?

OBJECTIVES

The purpose of this research was to evaluate whether operator experience and the quantitative analysis system (Q-Box; SuperSonic Imagine, Aix-en-Provence, France) diameter affect the repeatability of liver stiffness measurements.

METHODS

We enrolled 417 outpatients. All measurements were performed by 2 operators, including an expert and a novice. Each patient was continuously measured 3 times by the 2 operators. The Q-Box diameter was adjusted to 10, 20, and 30 mm each time, and the mean elasticity values were recorded. Intraobserver repeatability was evaluated by the intraclass correlation coefficient (ICC). Interobserver repeatability was evaluated by the ICC, coefficient of variation (CV), and Bland-Altman plots.

RESULTS

The study group included 241 male and 176 female patients. The expert operator had higher ICCs than the novice operator at each Q-Box diameter. The overall interobserver agreement was excellent, and the results showed that compared to other groups, the ICC was the lowest and the CV was the largest for the 30-mm-diameter group. The ICC and CV values were similar between the 10- and 20 mm-diameter groups. The Bland-Altman plots showed that the mean difference was -0.2 kPa for the 10-, 20-, and 30 mm-diameter groups. However, the limits of agreement were the largest in the 30-mm-diameter group and were similar between the 10- and 20-mm-diameter groups.

CONCLUSIONS

The repeatability of liver stiffness measurements is affected not only by experience but also by the Q-Box diameter.

Shear-wave elastography of the liver in a healthy pediatric population

PURPOSE

The aim of this study was to determine the elastic modulus values of normal liver tissue in school-age children by shear wave elastography (SWE) and to study the factors that influence these stiffness measurements.

METHODS

Six hundred and four school-age children (295 girls and 309 boys) who were recruited at a hospital and had normal results of specific laboratory tests and imaging studies underwent SWE examinations. The elastic modulus values were obtained in segment V and VI for each subject and comparisons were made between age groups.

RESULTS

The mean elastic modulus values for school-age children were 6.3 ± 1.1 kPa for segment V and 6.2 ± 1.1 kPa for segment VI. A positive linear trend in liver stiffness was found for the 6 to 9-year-old age group in segments V and VI (R² = 0.076 vs R² = 0.085, respectively, P < .05). No statistically significant difference in liver stiffness was found between genders and between segment groups (P > .05).

CONCLUSION

SWE is a feasible method to measure liver stiffness in the school-age population. We established a normal range of liver elastic modulus values in school-age children, which will provide a basis for evaluating the changes in liver stiffness caused by various diseases.

Precise fibrosis staging with shear wave elastography in chronic hepatitis B depends on liver inflammation and steatosis

BACKGROUND

Two-dimensional shear wave elastography (2D-SWE) is the latest generation of ultrasound elastography for the non-invasive assessment of liver fibrosis in chronic hepatitis B (CHB). We aimed to identify confounders of 2D-SWE in fibrosis grading.

METHODS

A prospective cohort of 440 CHB patients (286 with liver biopsy and 154 with clinical decompensated cirrhosis) was consecutively enrolled from a clinical trial (registration number: ChiCTR-DCD-15006000) aimed at optimizing 2D-SWE assessments from 2015 to 2018. All patients underwent 2D-SWE examination, anthropometric measurement, and serum biomarker assessment. Steatosis was graded by the magnetic resonance imaging-derived proton density fat fraction (MRI-PDFF).

RESULTS

Overall, the prevalence of incorrect fibrosis staging by 2D-SWE was 26.1% (n = 115), with 43.5% of patients under-staged and 56.5% over-staged. In multivariate analysis, the steatosis degree was an independent predictor of 2D-SWE discordance in the overall cohort, with moderate-severe steatosis for underestimation (odds ratio, [OR] = 4.3, 95% confidence interval [CI] 1.2-18.2, p = 0.049) and overestimation (OR = 8.2, 95% CI 2.9-23.5, p < 0.001), and mild steatosis for overestimation (OR = 3.7, 95% CI 1.5-9.0, p = 0.004). In patients with liver biopsy, both histological inflammation activity over 2 (OR = 5.0, 95% CI 2.0-25.3, p = 0.048) and moderate-severe steatosis (OR = 5.2, 95% CI 2.1-13.4, p < 0.001) were independent factors associated with discordance. For the risk of 2D-SWE mis-staging, a nomogram that integrated these confounders was established and the area under the receiver operating characteristic curve of the model was 0.861.

CONCLUSIONS

Steatosis and inflammation activities were confounders for 2D-SWE. The combination of these confounders could predict mis-staging risks of CHB-related fibrosis with 2D-SWE and may be valuable to decision-making on liver biopsy for fibrosis staging.

Ultrasound-based liver elastography in the assessment of fibrosis

Ultrasound-based elastography has rapidly replaced the need for liver biopsy in most patients with chronic liver disease in recent years. The technique is now widely supported by many manufacturers. This review will introduce various current ultrasound-based elastography techniques, review the physics and scanning techniques, discuss potential cofounding factors as well as summarising the evidence for its use in staging liver fibrosis using shear-wave elastography among different disease aetiologies. Future challenges and directions will be also be discussed.

Performance of B-mode ratio and 2D shear wave elastography for the detection and quantification of hepatic steatosis and fibrosis after liver transplantation

OBJECTIVES

To evaluate the diagnostic performance of B-mode ratio and shear wave elastography (SWE) for the assessment of steatosis and liver fibrosis after liver transplantation.

MATERIALS AND METHODS

Patients hospitalized for a systematic check-up after liver transplantation underwent the same day hepatic ultrasound with B-mode ratio and SWE, followed by liver biopsy and biological examinations. Steatosis was measured using hepatorenal sonographic index of B-mode ratio and liver stiffness using SWE. Liver biopsy, used as gold standard, graded steatosis S0(<5%), S1(5-<33%), S2(33-<66%), or S3(≥66%) and liver fibrosis according to the Metavir score. The results were tested against two external validation cohorts.

RESULTS

Fifty-eight patients were included. Mean B-ratio value was significantly higher in patients with steatosis (0.95 ± 0.13 versus 1.39 ± 0.41, P < 0.001). A B-mode ratio cutoff values at least 0.985 was found optimal for steatosis' detection [area under the receiver operating characteristic curve (AUROC) 0.902 ± 0.05, sensitivity 95%, specificity 79%]. A B-mode ratio value below 0.9 ruled out steatosis and above 1.12 ruled in steatosis. Mean SWE value for patients without significant fibrosis (≤F1) was 15.90 ± 9.2 versus 19.27 ± 7.7 kPa for patients with fibrosis (P = 0.185). A 2D-SWE value below 7.85 kPa ruled out significant fibrosis and above 26.35 kPa ruled it in.

CONCLUSION

The B-mode ratio is an efficient and accurate tool for the noninvasive diagnostic of steatosis in postliver transplantation patients. Yet, because liver stiffness is higher in postliver transplantation patients, 2D-SWE is not reliable in the diagnosis of significant fibrosis after liver transplantation.

Methotrexate therapy is not associated with increased liver stiffness and significant liver fibrosis in rheumatoid arthritis patients: A cross-sectional controlled study with real-time two-dimensional shear wave elastography

OBJECTIVE

To explore the significance of the association between treatment with methotrexate (MTX) and liver stiffness in rheumatoid arthritis (RA) patients.

METHODS

We enrolled 140 consecutive RA patients under MTX treatment (MTX-treated RA; mean treatment duration: 6.2 years; mean MTX cumulative dose: 4.67 g), 33 RA patients naive to MTX (MTX-naive RA) and 100 age and sex-matched healthy blood donors (HD). Liver stiffness was assessed by real time two-dimensional shear wave elastography, with values ≥7.1 Kilopascals (kPa) defining significant liver fibrosis.

RESULTS

kPa values in HD (4.32 ± 0.7) were lower than that in MTX-naive RA (4.92 ± 0.8) and MTX-treated RA (4.85 ± 0.9, p < .0005 for trend). On the contrary, the difference in kPa between MTX-naive and MTX-treated RA was not significant (p = .89). Similarly, liver stiffness was not significantly different across strata of cumulative MTX dose (4.95 ± 0.7 kPa in MTX <1 g, 4.90 ± 1.1 kPa in MTX 1-3 g and 4.80 ± 0.9 in MTX >3 g, p = .610). Significant liver fibrosis was diagnosed in 4 patients in the MTX-treated RA (highest kPa value = 7.6; no liver function test abnormalities or clinical signs of hepatic failure) and in none in both the MTX-naive RA and HD groups (p = .145).

CONCLUSION

Liver stiffness values, although within the normal range, are significantly higher in RA patients vs. controls, irrespective of MTX treatment. RA patients taking MTX do not have a higher prevalence of significant liver fibrosis when compared to MTX naive RA patients and the general population.

How intrahepatic cholestasis affects liver stiffness in patients with chronic hepatitis B: a study of 1197 patients with liver biopsy

OBJECTIVES

To evaluate the impact of intrahepatic cholestasis on liver fibrosis staging using liver stiffness measurements (LSM).

METHODS

Between July 2011 and September 2016, a total of 1197 patients with chronic hepatitis B (CHB) infection were enrolled to collect clinical, biological, 2D shear wave elastography (SWE), and histological (METAVIR scoring system) data. LSM was compared in patients with normal total bilirubin (TB) versus abnormal TB for each group of fibrosis stage, alanine aminotransferase (ALT) levels, and inflammation grade. Logistic regression and ROC analyses were performed to assess the benefit of adding TB and to LSM for fibrosis staging.

RESULTS

Nine hundred and seventy-three patients were analyzed. Within the same fibrosis stage, LSMs showed significantly higher value in patients with abnormal TB than those with normal TB. Increased LSM for abnormal TB was generally found within different sub-groups of patients (≤ F2 or ≥ F3; ALT < 2 × upper limit of normal (ULN) or ALT ≥ 2 × ULN; METAVIR activity grade ≤ 1 or ≥ 2). Patients with abnormal TB level showed higher optimal cutoff values: 10.46 kPa for ≥ F2, 10.94 kPa for ≥ F3, and 15.88 kPa for F4, than those with normal TB (7.62 kPa, 8.26 kPa, and 11.01 kPa, respectively). LSM assessed fibrosis stage (≥ F2, ≥ F3, F4) showed higher false positive rate in patients with abnormal TB level (44.6%, 45.1%, 39.6%) than those with normal TB (20.7%, 17.1%, 14.4%). However, the area under the ROC curve did not change appreciably when adding TB to LSM for fibrosis stage.

CONCLUSION

Intrahepatic cholestasis showed slight effect on LSM in patients with CHB, also leading to overestimation of liver fibrosis stages. But adding TB level to LSM did not improve the overall diagnostic performance of liver fibrosis stage.

KEY POINTS

• Intrahepatic cholestasis showed slight effect on liver stiffness measurements (LSMs) in chronic HBV patients. • Patients with abnormal total bilirubin (TB) level showed higher optimal cutoff values and false positive rate. • When taking into account intrahepatic cholestasis, the diagnostic performance of LSM for liver fibrosis staging in patients with chronic HBV infection will not improve.

Liver Stiffness Measured by 2-Dimensional Shear Wave Elastography: Prospective Evaluation of Healthy Volunteers and Patients With Liver Cirrhosis

OBJECTIVES

We aimed to establish normal values for liver stiffness measurement, performed by 2-dimensional shear wave elastography (LOGIQ E9; GE Healthcare, Wauwatosa, WI), in healthy volunteers, patients with nonhepatic morbidities, and patients with histologically confirmed liver cirrhosis.

METHODS

A total of 175 participants were included between July 2016 and February 2018. Three cohorts were analyzed: healthy volunteers (n = 68), patients with healthy livers but nonhepatic morbidities (n = 57), and patients with liver cirrhosis (n = 50). Liver stiffness measurement was performed by 2 observers with different levels of experience to determine interobserver agreement.

RESULTS

Of the 175 participants included, 91 were male, and the mean age ± SD was 44.4 ± 19.4 years. The success rate for 175 liver stiffness measurements was 95.4%. The number of unsuccessful measurements was significantly higher in the liver cirrhosis cohort (P = .04). The interobserver agreement was excellent (intraclass correlation coefficient, 0.87). Liver stiffness in the healthy-liver patient cohort (4.93 ± 0.83 kPa) was not significantly different from that in the healthy-volunteer cohort (5.19 ± 1.03 kPa; P = .13). Apart from male sex in the healthy-volunteer cohort, age, body mass index, mild steatosis, and nonhepatic morbidities had no significant impact on liver stiffness. Liver stiffness values in participants without liver disease (healthy volunteers and healthy-liver patients; n = 125) ranged from 3.62 to 7.02 kPa (2.5th-97.5th percentiles). Notably, there was no overlap of liver stiffness measurements between the patients without liver disease and the cirrhosis cohort (13.29 ± 3.27 kPa [7.76-19.49 kPa]).

CONCLUSIONS

Liver stiffness values in healthy individuals vary widely and are not dependent on age, body mass index, or specific nonhepatic comorbidities. Liver stiffness values within the normal range can noninvasively rule out cirrhosis, as liver stiffness is significantly higher in cirrhotic patients (P < .001). Two-dimensional shear wave elastography has excellent interobserver agreement.

Normal Liver Stiffness Values in Children: A Comparison of Three Different Elastography Methods

OBJECTIVES

Noninvasive tests for the evaluation of liver fibrosis are particularly helpful in children to avoid general anesthesia and potential complications of invasive tests. We aimed to establish reference values for 2 different elastography methods in a head-to-head comparison for children and adolescents 4 to 17 years, using transient elastography as common reference in a subset.

METHODS

A total of 243 healthy participants aged 4 to 17 years were examined by a single observer with a full liver B-mode scan before elastography, following a minimum of 3 hours fasting. Liver stiffness measurements (LSMs) using 2-dimensional shear wave elastography (2D-SWE, GE Logiq E9) and point shear wave elastography (pSWE, Samsung RS80A with Prestige) were performed in all participants, and compared to transient elastography (TE, FibroScan) in a subset (n = 87). Interobserver agreement was evaluated in 50 children aged 4 to 17 years.

RESULTS

Valid measurements were obtained in 242 of 243 (99.6%) subjects for 2D-SWE, 238 of 243 (97.9%) for pSWE, and in 83 of 87 (95.4%) for TE. Median liver stiffness overall was 3.3 (interquartile range [IQR] 2.7-4.3), 4.1 (IQR 3.6-4.7), and 4.1 kPa (IQR 3.5-4.6) for 2D-SWE, pSWE, and TE, respectively. Intraclass correlation coefficients between observers were 0.84 and 0.83 for 2D-SWE and pSWE, respectively. LSM values were significantly lower for 2D-SWE compared to pSWE and TE, and increased with advancing age. Higher LSM values in males were observed in adolescents.

CONCLUSIONS

All methods showed excellent feasibility. 2D-SWE showed significantly lower LSM values than pSWE and TE, and lower failure rate compared to TE. Our results further indicate an age and sex effect on LSM values.

Influence of Probe Pressure on Ultrasound-Based Shear Wave Elastography of the Liver Using Comb-Push 2-D Technology

It has been postulated that in the liver, applying increased probe pressure during ultrasound-based shear wave elastography (SWE) might lead to a false increase in the SWE result. We aimed to determine the influence of increased intercostal probe pressure when performing SWE of the liver. We also investigated the number of measurements required to achieve technically successful and reliable SWE examinations. This prospective, clinical study included 112 patients and 2240 SWE measurements of the liver. We applied probe pressure intercostally, to reduce the skin-to-liver capsule distance (SCD), which could stabilize the SWE signal and thus increase the number of technically successful measurements. We performed 10 measurements with maximum probe pressure and 10 with normal pressure in each patient. Thus, two analysis groups were compared for differences. Compared with normal pressure, maximum probe pressure significantly reduced the SCD (p < 0.001) and significantly increased the number of technically successful measurements from 981 to 1098, respectively (p < 0.001). The SWE results with normal and maximum probe pressure were 5.96 kPa (interquartile range: 2.41) and 5.45 kPa (interquartile range: 1.96), respectively (p < 0.001). In obese patients, a large SCD poses a diagnostic challenge for ultrasound SWE. We found that maximum intercostal probe pressure could reduce the SCD and increase the number of technically successful measurements, without falsely increasing the SWE result. Only three measurements were required to achieve technically successful and reliable SWE examinations.

Liver elasticity in healthy individuals by two novel shear-wave elastography systems-Comparison by age, gender, BMI and number of measurements

OBJECTIVE

Establishing normal liver stiffness (LS) values in healthy livers is a prerequisite to differentiate normal from pathological LS values. Our aim was to define normal LS using two novel elastography methods head-to-head and to assess the number of measurements, variability and reproducibility.

MATERIALS AND METHODS

We evaluated shear wave elastography (SWE) methods integrated in Samsung RS80A and GE S8 by obtaining LS measurements (LSM) in 100 healthy subjects (20-70 years). Transient Elastography (TE) was used as reference method. Data were analyzed according to age, sex, BMI and 5 vs. 10 measurements. All subjects underwent B-mode ultrasound examination and lab tests to exclude liver pathology. Interobserver variation was evaluated in a subset (n = 24).

RESULTS

Both methods showed excellent feasibility, measuring LS in all subjects. LSM-mean for GE S8 2D-SWE was higher compared to TE (4.5±0.8 kPa vs. 4.2±1.1, p<0.001) and Samsung RS80A (4.1±0.8 kPa, p<0.001). Both methods showed low intra- and interobserver variation. LSM-mean was significantly higher in males than females using 2D-SWE, while a similar trend for Samsung SWE did not reach significance. No method demonstrated statistical significant difference in LSM across age and BMI groups nor between LSM-mean based on 5 vs. 10 measurements.

CONCLUSION

LSM was performed with high reproducibility in healthy adult livers. LSM-mean was significantly higher for GE S8 2D-SWE compared to Samsung RS80A and TE in healthy livers. Males had higher LSM than females. No method demonstrated statistical significant difference in LSM-mean across age- and non-obese BMI groups. Our results indicate that five LSM may be sufficient for reliable results.

Role of two-dimensional shear wave elastography in chronic liver diseases: A narrative review

Liver biopsy is the gold standard for evaluating the degree of liver fibrosis in patients with chronic liver disease. However, due to the many limitations of liver biopsy, there has been much interest in the use of noninvasive techniques for this purpose. Among these techniques real-time two-dimensional shear wave elastography (2D-SWE) has the advantage of measuring tissue elasticity with the guidance of B-mode images. Recently, many studies have been conducted on the application of 2D-SWE in patients with various liver diseases, and their validity has been confirmed. Here, we briefly discuss the role of 2D-SWE in patients with chronic liver diseases, particularly aspects of the examination techniques and clinical applications.

On Patient Related Factors and Their Impact on Ultrasound-Based Shear Wave Elastography of the Liver

The aim of the study was to investigate patient-related factors associated with either reliable or poorly reliable measurement results of ultrasound-based shear wave elastography (SWE) of the liver. A total of 188 patients were analyzed prospectively with binary logistic regression using the interquartile range/median as cutoff to define two groups based on reliable and poorly reliable SWE results. SWE results correlated significantly with liver biopsy. Factors associated with reliable SWE results (i.e., no negative impact on measurements) were age, sex, cirrhosis, antiviral and/or cardiovascular medication, smoking habits and body mass index. Factors associated with poorly reliable SWE results were increased skin-to-liver capsule distance (odds ratio = 3.08, 95% confidence interval: 1.70-5.60) and steatosis (odds ratio = 2.89, 95% confidence interval: 1.33-6.28). These findings indicate that the interquartile range/median as a quality parameter is useful in avoiding poorly reliable SWE results. How best to examine patients with increased skin-to-liver capsule distance is a matter of some controversy, as the incidences of obesity, diabetes and metabolic syndrome are increasing worldwide; however, our results indicate that reliable SWE results can be obtained in this group of patients by using ultrasound-based SWE.

Intra- and Inter-Observer Reproducibility of a 2-D Shear Wave Elastography Technique and the Impact of Ultrasound Experience in Achieving Reliable Data

The aim of the study described here was to evaluate the reproducibility of a new shear-wave elastography (SWE) technique, 2-D SWE.GE, and the impact of ultrasound experience in acquiring reliable measurements, as no official recommendations are available for this system. Elastographic measurements (EMs) were obtained in 60 patients using 2-D-SWE with the GE Logiq E9. Three examiners with different levels of experience in ultrasound-based elastography performed 10 valid EMs on each subject: a novice (C.P.) who had no experience in liver elastography and had performed fewer than 50 ultrasound examinations; an elastography expert (A.M.S.) who had more than 1 y of liver elastographic experience in four elastographic methods and had performed more than 1000 ultrasonography examinations; and an ultrasound expert (T.M.) who had no experience in liver elastography and had performed more than 1000 ultrasound examinations. Medians and interquartile ranges were calculated (m/s). We used the inter-class correlation coefficient and Bland-Altman plots with 95% lower and upper limits of agreement to assess the inter- and intra-observer reproducibility of 2-D-SWE.GE measurements. The final study group included 60 patients, 56.7% women and 43.3% men, with a mean age of 33.08 ± 13.83 y and mean body mass index of 22.85 ± 4.04 kg/m². In this group, 73.3% were healthy volunteers and 26.7% had compensated liver cirrhosis. We did not find significant differences between EMs taken by the examiners overall and across study groups. The overall agreement between examiners was excellent: 0.915 (95% confidence interval [CI]: 0.870-0.946). The agreement between the novice and the experienced examiners, respectively, was good to excellent (novice and ultrasound expert: 0.908, 95% CI: 0.846-0.945; novice and elastography expert: 0.885, 95% CI: 0.808-0.931). The intra-observer reproducibility for each of the examiners was excellent; however, the inter-class correlation coefficients were higher for the examiners more experienced in elastography: 0.936 (95% CI: 0.896-0.963) versus 0.966 (95% CI: 0.943-0.980) versus 0.984 (95% CI: 0. 973-0.991). The good ICCs for the median values indicate that 2-D-SWE.GE is a reproducible method. Ultrasound experience did not significantly influence the results.

2D shear wave elastography combined with MELD improved prognostic accuracy in patients with acute-on-chronic hepatitis B liver failure

OBJECTIVES

To evaluate accuracy of two-dimensional shear wave elastography (2D SWE) and develop and validate a new prognostic score in predicting prognosis of acute-on-chronic liver failure (ACLF) patients.

METHODS

From 1 October 2013 to 30 September 2015, we consecutively enrolled 290 patients, sequentially collected data (including 2D SWE, ultrasound parameters, laboratory data and prognostic scores) and recorded patients' outcome (recovering/steady or worsening) during a 90-day follow-up period. We evaluated ability of 2D SWE to predict outcomes of acute-on-chronic hepatitis B liver failure (ACLF-HBV) patients. We developed a new score (MELD-SWE, combining MELD and SWE values) for predicting mortality risk of ACLF-HBV in 179 patients in a derivation group, and validated in 111 patients.

RESULTS

2D SWE values were higher in worsening patients than recovering/steady ones (p < 0.001). Accuracy of 2D SWE in predicting outcomes of ACLF-HBV was comparable to that of the MELD score (p = 0.441). MELD-SWE showed a significantly higher prognostic value than MELD in both derivation (AUROC, 0.80 vs. 0.76, p = 0.040) and validation (AUROC, 0.87 vs. 0.82, p = 0.018) group.

CONCLUSIONS

The MELD-SWE score, combining MELD and SWE values, was superior to MELD alone for outcoming prediction in patients with ACLF-HBV.

KEY POINTS

• 2D SWE is a simple prognostic evaluation tool in patients with ACLF-HBV. • MELD-SWE was created in this study: 1.3×MELD + 0.3×2D SWE (kPa). • MELD-SWE score was superior to MELD alone for outcoming prediction in ACLF-HBV. • In this study, 46.8 was the optimal cut-off value of MELD-SWE score.

Influencing Factors of 2D Shear Wave Elastography of the Muscle - An Ex Vivo Animal Study

OBJECTIVE

To evaluate measurement confounders on 2D shear wave elastography (2D-SWE) elastography of muscle.

MATERIALS AND METHODS

Ex vivo , porcine muscle was examined with a GE LOGIQ E9 ultrasound machine with a 9 L linear (9 MHz) and C1-6 convex probe (operating at 2.5 or 6 MHz). The influence of different confounders on mean shear wave velocity (SWVmean) was analyzed: probes, pressure applied by probe, muscle orientation, together with the impact of different machine settings such as frequency, placement depth and size of region of interest (ROI). The mean of twelve repeated SWVmean measurements (m/s) and coefficient of variation (CV; standard deviation/mean in %) were assessed for each test configuration.

RESULTS

Reproducibility (CV) and maximum possible tissue depth of the linear probe were inferior to the convex probe. With the linear probe, there was a linear decrease of SWVmean with placement depth from 4.56 m/s to 1.81 m/s. A significant increase of SWVmean (p<0.001) was observed for larger ROI widths (range 3.96 m/s to 6.8 m/s). A change in the machine operation mode ('penetration' instead of 'general') led to a significant increase of SWVmean (p=0.04). SWVmean in the longitudinal direction of muscle was significantly higher than in cross section (p<0.001) (e. g. 4.56 m/s versus 3.42 m/s). An increase of linear probe pressure significantly increased muscle SWVmean from 5.29 m/s to 7.21 m/s (p<0.001).

CONCLUSIONS

2D-SWE of muscle is influenced by a wealth of parameters. Therefore, standardization of measurement is advisable before application in clinical research studies and routine patient assessment.

Quantitative and noninvasive assessment of chronic liver diseases using two-dimensional shear wave elastography

Two-dimensional shear wave elastography (2D-SWE) is a rapid, simple and novel noninvasive method that has been proposed for assessing hepatic fibrosis in patients with chronic liver diseases (CLDs) based on measurements of liver stiffness. 2D-SWE can be performed easily at the bedside or in an outpatient clinic and yields immediate results with good reproducibility. Furthermore, 2D-SWE was an efficient method for evaluating liver fibrosis in small to moderately sized clinical trials. However, the quality criteria for the staging of liver fibrosis are not yet well defined. Liver fibrosis is the main pathological basis of liver stiffness and a key step in the progression from CLD to cirrhosis; thus, the management of CLD largely depends on the extent and progression of liver fibrosis. 2D-SWE appears to be an excellent tool for the early detection of cirrhosis and may have prognostic value in this context. Because 2D-SWE has high patient acceptance, it could be useful for monitoring fibrosis progression and regression in individual cases. However, multicenter data are needed to support its use. This study reviews the current status and future perspectives of 2D-SWE for assessments of liver fibrosis and discusses the technical advantages and limitations that impact its effective and rational clinical use.

Assessing Liver Stiffness by 2-D Shear Wave Elastography in a Healthy Cohort

The aim of this study was to assess the normal ranges of liver stiffness measurements (LSMs) in participants with healthy livers, using General Electric 2-D shear wave elastography (2-D-SWE-GE) compared with transient elastography (TE). We included 80 participants with healthy livers and without known liver disease, in whom liver stiffness was evaluated in the same session using two elastographic methods, TE and 2-D-SWE-GE. Reliable LSMs were defined for TE as the median of 10 measurements with a success rate of ≥60% and an interquartile range (IQR) < 30%, and for 2-D-SWE-GE, as the median of 10 measurements acquired in a homogenous area and an IQR < 30%. Participants with LSMs > 6.5 kPa by TE were excluded. Reliable LSMs were obtained in 79 participants (98.7%) by means of 2-D-SWE-GE and in 80 participants (100%) by means of TE (p = 0.9). The mean LSM obtained by 2-D-SWE-GE in our cohort of participants with healthy livers was 5.1 ± 1.3 kPa, which was significantly higher than the LSM assessed by TE (4.3 ± 0.9 kPa, p < 0.0001). In 2-D SWE-GE, mean LSMs were significantly higher for men than for women, 5.9 ± 1.2 kPa versus 4.7 ± 1.2 kPa (p = 0.0005). In conclusion, 2-D-SWE-GE has very good feasibility (98.7%) in healthy persons. The mean LSM determined by 2-D-SWE-GE in healthy participants was 5.1 ± 1.3 kPa. LSMs obtained by means of 2-D-SWE-GE were higher than those obtained by TE in participants with healthy livers.

Systematic review and meta-analysis: non-invasive detection of non-alcoholic fatty liver disease related fibrosis in the obese

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a significant disease burden in obesity. Liver fibrosis is an important prognostic factor in NAFLD, and detection is vital. The pathophysiological changes of obesity can alter the accuracy of non-invasive NAFLD tests. We aimed to review current evidence for common non-invasive tests for NAFLD-related fibrosis in obesity.

METHODS

We systematically searched for studies assessing the diagnostic accuracy of 11 biomarker panels and elastography techniques for NAFLD-related fibrosis in obesity. Meta-analyses were performed where possible.

RESULTS

Thirty-eight studies were identified assessing the selected tests in obese populations. Simple biomarker panels (e.g. NAFLD fibrosis score) were the most validated. Evidence showed better accuracy of complex biomarker panels (NAFLD fibrosis score: summary receiver operator characteristic [SROC] 0.795-0.813 vs. enhanced liver fibrosis: SROC 0.962); however, these were poorly validated in obesity. Elastography techniques were better studied and had high diagnostic accuracy (transient elastography: SROC 0.859; magnetic resonance elastography: SROC 0.965) but were limited by BMI-dependent failure. Limited evidence was found to validate the accuracy of any test in exclusively obese populations.

CONCLUSION

In obese subjects, complex biomarker panels and elastography have been reasonable to good accuracy for NAFLD-related fibrosis; however, these methods have not been well validated. Further study in this high-risk population is needed.

Supersonic shear imaging for the diagnosis of liver fibrosis and portal hypertension in liver diseases: a meta-analysis

BACKGROUND AND AIMS

The meta-analysis aimed to summarize the technical success rate of supersonic shear imaging (SSI) and to evaluate the diagnostic performance of liver and spleen stiffness measurement (LSM and SSM) with SSI for the detection of liver fibrosis, portal hypertension, and gastroesophageal varices in liver diseases.

METHODS

PubMed, EMBASE, and Cochrane Library databases were searched. Technical success rate of SSI was pooled. Area under curve (AUC), sensitivity, and specificity with corresponding 95% confidence interval (CI) were calculated.

RESULTS

Included studies regarding the diagnostic performance of SSI for liver fibrosis, portal hypertension, and esophageal varices numbered 28, 4, and 4 respectively. The pooled technical success rates of LSM and SSM were 95.3% and 75.5%, respectively. The AUC, sensitivity, and specificity of LSM/SSM for different stages of liver fibrosis were 0.85-0.94, 0.7-0.89, and 0.82-0.92, respectively. The AUC, sensitivity, and specificity of LSM were 0.84 (95%CI = 0.8-0.86), 0.79 (95%CI = 0.7-0.85), and 0.82 (95%CI = 0.72-0.88) for clinically significant portal hypertension, 0.85 (95%CI = 0.82-0.88), 0.8 (95%CI = 0.68-0.88), and 0.8 (95%CI = 0.6-0.92) for any varices, and 0.86 (95%CI = 0.83-0.89), 0.86 (95%CI = 0.76-0.92), and 0.61 (95%CI = 0.35-0.83) for high-risk varices, respectively.

CONCLUSIONS

LSM with SSI had a high diagnostic accuracy for liver fibrosis, but a moderate diagnostic accuracy for portal hypertension and esophageal varices.

2D Shear Wave Elastography of Liver in Patients with Primary Extrahepatic Portal Vein Obstruction

AIMS

To evaluate liver stiffness (LS) in patients of primary extrahepatic portal vein obstruction (EHPVO) using 2D shear wave elastography (SWE) and compare it with healthy volunteers.

METHODS

Fifty patients (mean age: 22.4 years) of EHPVO and 25 healthy volunteers were included in the study. Liver function tests and viral markers were done in both groups and endoscopy in EHPVO group, followed by ultrasonography and SWE of liver. Liver elastography was done with patients/volunteers in supine position through right intercostal space. The LS for right lobe of liver was recorded in kilopascals. Three such measurements were taken and the mean of both groups were compared. The variables were also correlated with mean LS using Pearson's correlation coefficient in EHPVO group.

RESULTS

There was no significant difference in the mean LS in patients of EHPVO (5.96 kPa) and healthy volunteers (5.47 kPa) (P = 0.093). There was no significant correlation between LS with duration of symptoms, hematemesis, esophageal varices, total bilirubin, serum alkaline phosphatase and aspartate aminotranferase levels in EHPVO group.

CONCLUSION

SWE of liver may be used as a simple additional tool in the diagnosis of patients of EHPVO who show LS values similar to normal liver.

Guidelines for Finite-Element Modeling of Acoustic Radiation Force-Induced Shear Wave Propagation in Tissue-Mimicking Media

Ultrasound shear wave elastography is emerging as an important imaging modality for evaluating tissue material properties. In its practice, some systematic biases have been associated with ultrasound frequencies, focal depths and configuration, and transducer types (linear versus curvilinear), along with displacement estimation and shear wave speed estimation algorithms. Added to that, soft tissues are not purely elastic, so shear waves will travel at different speeds depending on their spectral content, which can be modulated by the acoustic radiation force (ARF) excitation focusing, duration, and the frequency-dependent stiffness of the tissue. To understand how these different acquisition and material property parameters may affect the measurements of shear wave velocity, the simulations of the propagation of shear waves generated by ARF excitations in viscoelastic media are a very important tool. This paper serves to provide an in-depth description of how these simulations are performed. The general scheme is broken into three components: 1) simulation of the 3-D ARF push beam; 2) applying that force distribution to a finite-element model; and 3) extraction of the motion data for post-processing. All three components will be described in detail and combined to create a simulation platform that is powerful for developing and testing algorithms for academic and industrial researchers involved in making quantitative shear-wave-based measurements of tissue material properties.

Does motion affect liver stiffness estimates in shear wave elastography? Phantom and clinical study

This study was undertaken to evaluate the impact of free-breathing (FB) vs. Apnea on Shear-wave elastography (SWE) measurements. Quantitative liver-stiffness measurements were obtained during FB and Apnea for 97 patients with various body-morphologies and liver textures. Quality indexes of FB and Apnea elasticity maps (percentage of non-filling (PNF), temporal (TV) and spatial (SV) variabilities) were computed. SWE measurements were also obtained from an homogeneous phantom at rest and during a mechanically-induced motion. Liver-stiffness values estimated from FB and Apnea acquisitions were correlated, particularly for homogeneous livers (r=0.76, P<0.001) and favorable body-morphologies (r=0.68, P<0.001). However FB values were consistently 20-25% lower than Apnea ones (P<0.001). FB also systematically resulted in degradation of TV (P<0.005) and PNF (P<0.001) compared to Apnea but had no impact on SV. With the phantom, no differences between SWE measurements at rest and during motion were observed. Apnea and FB measurements are highly correlated, although FB data quality is degraded compared to Apnea and estimated stiffness in FB is systematically lower than in Apnea. These discrepancies between rest and motion states were observed for patients but not for phantom data, suggesting that patient breath-holding impacts liver stiffness.

The Avaibility of Strain Elastography in a Hydatid Cyst - Interobserver Study

Background

To differentiate the hydatid cyst (HC) types by ultrasound elastography using two different sizes (4 mm and 8 mm) of the region of interest (ROI) and asking two different radiologists (interobserver) for their opinion.

Material/Methods

Patients with HC were evaluated by USG elastography. The statistical anayses were performed using Strain index (SI) which is the unit of strain elastography.

Results

A total of 26 out of 33 patients were female, and 7 were male. The mean age was 38.85±17.62 (range from 10 to 72 years). Type I: 6, Type 2: 6, Type III: 6, Type IV: 11, Type V: 4. There was no significant difference in HC SI (regardless of types) between O1 and O2, and 4-mm and 8-mm ROI (p>0.05). There was no statistically significant difference between SI of HC types of interobservers (O1–O2) and ROI sizes (4–8 mm) (p>0.05 for all parameters). The highest correlation between HC types and ROI sizes was in ROI size of 4 mm.

Conclusions

The correlation between SI and types was reliable in standard-applied 4-mm ROI. There was no statistically significant difference between interobservers in SI values. Thus, elastography tecnhnique is objective for HC but not appropriate to differentiate the types.

Sound speed measurement in the liver: Methodology and influencing factors

AIM: To investigate the methodology and influential factors of sound speed (SS) measurement in the liver.

METHODS: SS measurement was performed on 60 normal volunteers in different conditions (different liver lobes, breathing phases, probe positions, depth, and probe frequency).

RESULTS: The SS values of the left exterior lobe, the left interior lobe, the right anterior lobe and the right posterior lobe were 1531.94 m/s ± 46.57 m/s, 1560.89 m/s ± 38.03 m/s, 1568.89 m/s ± 20.34 m/s, and 1527.17 m/s ± 38.09 m/s, respectively. There were significant differences among the SS values in different lobes, except that between the left exterior lobe and right posterior lobe, and between the left interior lobe and right anterior lobe. The SS values at end-inspiration and end-expiration were 1570.15 m/s ± 15.58 m/s and 1567.33 m/s ± 19.52 m/s, respectively, and there was no significant difference between these values. The SS values in right inter-costal and sub-costal measurements were 1570.15 m/s ± 15.58 m/s and 1568.89 m/s ± 20.34 m/s, respectively, and there was no significant difference between them. The SS values measured 1 cm, 3 cm, and 7 cm under the liver capsule were 1570.15 m/s ± 15.58 m/s, 1556.78 m/s ± 18.25 m/s, and 1533.67 m/s ± 25.93 m/s, respectively, and there were significant differences in the SS values among different depth. The SS values measured with C6-2 probe and L14-5 probe were 1570.15 m/s ± 15.58 m/s and 1563 m/s ± 24.78 m/s, respectively, and there was no significant difference between them. The SS values of males and females were 1572.68 m/s ± 16.93 m/s and 1568.53 m/s ± 14.70 m/s, respectively, and there was no significant difference between them. SS measurement in the liver showed a good fit between inter- and intra-observer consistency.

CONCLUSION: Operators and gender do not affect the results in the measurement of SS in the liver. Different liver lobes and depth are the main influencing factors. Liver SS measurement performed at end-inspiration in the right anterior lobe about 1 cm under the capsule using an inter-costal approach may reveal liver SS more accurately.