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

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.

Impact of probe-induced abdominal compression on two-dimensional shear wave elastography measurement of split liver transplants in children

PURPOSE

To evaluate the effect of probe-induced abdominal compression of split liver transplants (SLT) in children on 2D-shear wave elastography (SWE) values.

MATERIALS AND METHODS

Data from 11 children (4.7 ± 4.8 years) who had undergone SLT and SWE were evaluated retrospectively. Elastograms were obtained with probes placed in an epigastric, midline position on the abdominal wall, with no and slight compression, using convex and linear transducers. For each identically positioned probe and condition, 12 serial elastograms were obtained and the SLT diameter was measured. Liver stiffness and degree of SLT compression were compared.

RESULTS

Slight probe pressure resulted in SLT compression, with a shorter distance between the cutis and the posterior margin of the liver transplant than in the measurement with no pressure (curved array, 5.0 ± 1.1 vs. 5.9 ± 1.3 cm, mean compression 15 %± 8 %; linear array, 4.7 ± 0.9 vs. 5.3 ± 1.0 cm, mean compression 12 %± 8 %; both p < 0.0001). The median liver stiffness was significantly greater with slight pressure than with no pressure (curved transducer, 13.38 ± 3.0 vs. 7.02 ± 1.7 kPa, p < 0.0001; linear transducer, 18.53 ± 7.1 vs. 9.03 ± 1.5 kPa, p = 0.0003).

CONCLUSION

Slight abdominal compression can significantly increase SWE values in children with left-lateral SLT. To obtain meaningful results and reduce operator dependency in free-hand examinations, probe pressure must be controlled carefully.

KEY POINTS

· Probe-induced compression can increase elastography values in split liver transplants in children. · In free-hand examination, probe pressure must be controlled carefully. · Pressure loading can be determined indirectly by the anteroposterior transplant diameter.

CITATION FORMAT

· Groth M, Fischer L, Herden U et al. Impact of probe-induced abdominal compression on two-dimensional shear wave elastography measurement of split liver transplants in children. Fortschr Röntgenstr 2023; 195: 905 - 912.

Diagnostic Efficacy of Renal 2-D Shear Wave Elastography in Familial Mediterranean Fever Disease

ABSTRACT

The aims of this study were to evaluate the kidneys of patients with familial Mediterranean fever (FMF) noninvasively and quantitatively using 2-D shear wave elastography (SWE) and to reveal the diagnostic efficacy of SWE in FMF-induced renal involvement. Healthy controls, FMF patients, and FMF patients with proteinuria were included in the study, and differences in renal stiffness values between the groups were examined. In addition, a relationship between age, sex, height, weight, body mass index, serum erythrocyte sedimentation rate, C-reactive protein, glomerular filtration rate, and renal stiffness values was evaluated. A total of 120 subjects, including 60 controls, 41 FMF patients without proteinuria, and 19 FMF patients with proteinuria, were enrolled in the study. Renal stiffness values were found to be significantly higher in the group with FMF compared with the control group. In addition, the values in the proteinuria group were higher than both the control group and FMF patients without proteinuria ( P < 0.001). A significant positive correlation was found between the renal stiffness value and C-reactive protein. According to receiver operating characteristic analysis, the mean renal stiffness value was 7.905 kPa or greater to determine FMF-induced proteinuria. The current study shows that renal stiffness values were higher in FMF patients compared with the normal population and the values showed further increase in the presence of proteinuria, which indicates a more advanced stage of renal involvement of the disease. These findings reveal that SWE can be used as a noninvasive diagnostic tool in the diagnosis, follow-up, and evaluating the severity of FMF.

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.

Hepatic Function and Fibrosis Assessment Via 2D-Shear Wave Elastography and Related Biochemical Markers Pre- and Post-Gastric Bypass Surgery

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) exhibits a worldwide distribution and encompasses a wider range of hepatic abnormalities that can culminate in serious clinical outcomes. The growing incidence of NAFLD necessitates more efficient management strategies particularly in clinically severe obese patients. Weight reduction is the cornerstone of NAFLD treatment; therefore, bariatric surgery could be a therapeutic approach in selected obese patients afflicted with NAFLD and other cardiometabolic comorbidities.

OBJECTIVE

The present study focused on the potential role of bariatric surgery on hepatic function and NAFLD-related histopathological features measured through a noninvasive method.

METHOD

Ninety patients entered to this study and underwent initial preoperative assessments including demographic profile, anthropometric measurements, standard laboratory tests, and hepatic biopsy. Liver stiffness was also evaluated via two-dimensional shear wave elastography (2D-SWE). All assessments were repeated over the subsequent 6 months following surgery except for liver biopsy.

RESULTS

Postoperative hepatic elasticity was lessened after 6 months (p = 0/002).The levels of alanine aminotransferase, gamma-glutamyl transferase, total protein, lipid indices, glucose, and platelet count were also improved following surgery (p < 0/001). Further progression of fibrosis was observed in 25% of patients after surgery.

CONCLUSION

Bariatric surgery was associated with a favorable impact on anthropometric and hepatic elasticity indices as well as metabolic parameters. The ideal target population for bariatric surgery should be thoroughly addressed, and the underlying risk factors for fibrosis progression need to be controlled before surgery. However, expanded research designed as comprehensive randomized controlled trials are recommended to confirm these findings.

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.

Elastography in the evaluation of liver allograft

Elastography is an established technique in the evaluation of chronic liver diseases. While there is a large clinical experience and data available regarding the performance of elastography in native liver, elastography experience with liver grafts is limited and still growing. Both ultrasound-based elastography techniques and MR Elastography (MRE) are useful in the assessment of liver fibrosis in liver transplants. Technical modifications for performing elastography will be required for optimum evaluation of the graft. In general, caution needs to be exercised regarding the use of elastography immediately following transplantation as post-operative changes, perioperative conditions/complications, inflammation, and rejection can cause increased stiffness in the graft. In the follow-up, detection of increased stiffness with elastography is useful for predicting development of fibrosis in the graft. Adjunctive MRI or ultrasound with Doppler also provides comprehensive evaluation of anatomy, vascular anastomosis and patency, biliary tree, and stiffness for fibrosis. In this review, we provide a brief overview of elastography techniques available followed by the literature review of elastography in the evaluation of grafts and illustration with clinical examples.

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.

A digital viscoelastic liver phantom for investigation of elastographic measurements

To develop elastography imaging technologies and implement image reconstruction algorithms, testing is done with phantoms. Although the validation step is usually taken using real data and physical phantoms, their geometry as well as composition, biomechanical parameters, and details of applying stress cannot be modified readily. Such considerations have gained increasing importance with the growth of elastography techniques as one of the non-invasive medical imaging modalities, which can map the elastic properties and stiffness of soft tissues. In this article, we develop a digital viscoelastic phantom using computed tomography (CT) imaging data and several application software tools based on illustrations of normal liver anatomy so as to investigate the biomechanics of elastography via finite element modeling (FEM). Here we discuss how to create this phantom step by step, demonstrate typical shear wave elastography (SWE) experiments of applying transient stress to the liver model, and calculate quantitative measurements. In particular, shear wave velocities are investigated through a parametric study designed based on tissue stiffness and distance from the applied stress. According to the results of FEM analysis, low errors were obtained for shear wave velocity estimation for both mechanical stress (~2-5%) and acoustic radiation force (~3-7%). Results show that our model is a powerful framework and benchmark for simulating and implementing different algorithms in shear wave elastography, which can serve as a guide for upcoming researches and assist scientists to optimize their subsequent experiments in terms of design.

Liver Stiffness Assessed by Ultrasound Shear Wave Elastography from General Electric Accurately Predicts Clinically Significant Portal Hypertension in Patients with Advanced Chronic Liver Disease

PURPOSE

 Clinically significant portal hypertension (CSPH) is responsible for most of the complications in patients with cirrhosis. Liver stiffness (LS) measurement by vibration-controlled transient elastography (VCTE) is currently used to evaluate CSPH. Bi-dimensional shear wave elastography from General Electric (2D-SWE.GE) has not yet been validated for the diagnosis of PHT. Our aims were to test whether 2D-SWE.GE-LS is able to evaluate CSPH, to determine the reliability criteria of the method and to compare its accuracy with that of VCTE-LS in this clinical setting.

MATERIALS AND METHODS

 Patients with chronic liver disease referred to hepatic catheterization (HVPG) were consecutively enrolled. HVPG and LS by both VCTE and 2D-SWE.GE were performed on the same day. The diagnostic performance of each LS method was compared against HVPG and between each other.

RESULTS

 2D-SWE.GE-LS was possible in 123/127 (96.90 %) patients. The ability to record at least 5 LS measurements by 2D-SWE.GE and IQR < 30 % were the only features associated with reliable results. 2D-SWE.GE-LS was highly correlated with HVPG (r = 0.704; p < 0.0001), especially if HVPG < 10 mmHg and was significantly higher in patients with CSPH (15.52 vs. 8.14 kPa; p < 0.0001). For a cut-off value of 11.3 kPa, the AUROC of 2D-SWE.GE-LS to detect CSPH was 0.91, which was not inferior to VCTE-LS (0.92; p = 0.79). The diagnostic accuracy of LS by 2D-SWE.GE-LS to detect CSPH was similar with the one of VCTE-LS (83.74 % vs. 85.37 %; p = 0.238). The diagnostic accuracy was not enhanced by using different cut-off values which enhanced the sensitivity or the specificity. However, in the subgroup of compensated patients with alcoholic liver disease, 2D-SWE.GE-LS classified CSPH better than VCTE-LS (93.33 % vs. 85.71 %, p = 0.039).

CONCLUSION

 2D-SWE.GE-LS has good accuracy, not inferior to VCTE-LS, for the diagnosis of CSPH.

Shear wave elastography may be sensitive and more precise than transient elastography in predicting significant fibrosis

BACKGROUND

Noninvasive measurements including transient elastography (TE) and two-dimensional shear wave elastography (SWE) have been used clinically instead of liver biopsy for regular assessment of liver fibrosis in chronic hepatitis B (CHB) patients.

AIM

To investigate the diagnostic efficiency of SWE compared to TE by assessing independent influencing factors and performance for diagnosing significant fibrosis based on our cohort of treatment-naive CHB patients.

METHODS

Fifty-four treatment-naive CHB patients who underwent liver biopsy to determine whether to initiate antiviral therapy were enrolled. SWE, TE, serum tests and liver biopsy were performed for all participants. The fibrosis-4 and aspartate aminotransferase to platelet ratio index scores were also calculated. Potential independent influencing factors on SWE and TE values were analyzed. Based on liver pathology results, the agreement and correlation were determined, and a comparison of the two methods was performed.

RESULTS

There were 27 cases (50%) of mild fibrosis (F0-F2) and 27 (50%) cases of significant fibrosis (F3-F6); fibrosis was assessed with the Ishak scoring system. Multivariate linear regression analyses revealed that the fibrosis stage was the only factor that affected the SWE values (P < 0.001), whereas the total bilirubin level (P = 0.013) and fibrosis stage (P = 0.037) were independent factors that affected TE values. Orthogonal partial least squares discriminant analysis showed that the number of independent factors (VIP > 1) was higher for TE than SWE. Bland-Altman analysis showed satisfactory agreement between liver stiffness measurements (LSMs) of SWE and TE. Both SWE and TE could significantly discriminate significant fibrosis from mild fibrosis (P < 0.001). SWE exhibited a higher correlation with LSMs of liver fibrosis than TE (r = 0.65 and 0.50, P < 0.001). The diagnostic performance of SWE was better than that of TE for significant fibrosis (F > 2). The areas under the receiver operating characteristic curves of SWE and TE were 0.786 and 0.714, respectively. The optimal LSM cutoff values of SWE and TE were 9.05 kPa and 8.15 kPa, respectively.

CONCLUSION

Compared to the TE value, the SWE value was less affected by other factors. SWE may be more sensitive and precise than TE in predicting significant fibrosis (> F2) in CHB patients.

Early development of hepatic fibrosis after Fontan procedure: A non-invasive study of a subclinical liver disease

BACKGROUND

To evaluate subclinical liver fibrosis after Fontan procedure using a comprehensive method that reflects the overall liver status rather than the focal biopsy lesion.

METHOD

This cross-sectional study included 66 patients without symptoms of liver disease who had at least 5 years of elapsed time since the Fontan procedure (time since Fontan procedure 17.5 ± 7.3 years). Serum enhanced liver fibrosis (ELF) scores and 2D shear wave elastography (SWE), which are expected to detect liver fibrosis earlier than liver enzyme tests and ultrasonography, were evaluated along with general examinations.

RESULTS

Liver cirrhosis diagnosed by ultrasonography showed a marked increase 16 years after surgery (elapsed time: 6-15 years since Fontan, 43.8%; 16-25 years, 70.8%; 26-35 years, 90.0%). The age-adjusted ELF score and liver stiffness according to SWE were elevated during the early postoperative period (6-15 years since Fontan). In adulthood (elapsed time > 16 years), the adjusted ELF score was correlated with liver stiffness (r = 0.514, p = .009) and liver enzyme levels. There was no correlation between liver fibrosis and the Fontan palliation type. AST to platelet count ratio and FIB-4, which are non-invasive fibrosis markers, presumed absence of fibrosis in approximately 90% of patients.

CONCLUSIONS

In the evaluation of early liver fibrosis after the Fontan procedure, abnormal findings of 2D SWE and ELF scores were observed before abnormal ultrasound and liver enzyme results. Therefore, these indicators may be helpful for the diagnosis of early liver fibrosis, and further longitudinal study might be needed.

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

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

Impact of hemodialysis on liver stiffness measured with real-time two-dimensional shear wave elastography

BACKGROUND AND AIMS

The impact of hemodialysis on liver stiffness is still unclear. The aim of the study was to assess liver fibrosis by real-time two-dimensional shear wave elastography (RT 2D-SWE) and to quantify the influence of net fluid withdrawal on liver stiffness during one hemodialysis session. The second aim was to investigate the influence of systolic blood pressure and time spent on dialysis (in years) on liver stiffness measurements.

METHODS

This before/after hemodialysis (HD) study in a group of end stage renal disease (ESRD) patients was carried out with patients on regular HD. Measurements of liver stiffness were done using RT 2D-SWE directly before and after a hemodialysis session.

RESULTS

In this study 27 patients with mean age 69.4 ± 14.75 years were included. Mean net fluid withdrawal volume per session was 2874.07 ± 778.35 ml. Mean pre-HD and post-HD liver stiffness measurements were 8.15 kPa (95% confidence interval, CI 7.61-8.68) and 6.70 kPa (95% CI 6.10-7.30 kPa), respectively. Mean liver stiffness reduction was 1.448 ± 1.14 kPa. The amount of fluid removed correlated with the decline in liver stiffness values after HD (ρ = 0.523, P = 0.003). There was a positive but statistically not significant correlation between time spent in HD and liver stiffness (ρ = 0.151, P = 0.623) CONCLUSION: Liver stiffness significantly declined after one session of HD. The change in liver stiffness was strongly correlated with the amount of net fluid withdrawal. Random liver stiffness measurements (LSM) by RT 2D-SWE does not precisely show the degree of fibrosis, Furthermore, it is presumed that postdialysis liver stiffness values likely reflect the real degree of liver fibrosis.

Prospective comparison of 2D-shearwave elastography in both liver lobes in healthy subjects and in patients with chronic liver disease

Background/aims: 2D-shearwave elastography is an established method for liver stiffness measurement (LSM). However, the success rate of LSM using the recommended standard technique in the right lobe is limited by several factors. We aimed to compare LSM in the right and left liver lobe in order to evaluate whether LSM in the left lobe could be an alternative if measurements in the right lobe are not feasible. Methods: A total of 116 subjects, 58 healthy volunteers and 58 patients with chronic liver disease (CLD), were prospectively included. LSM were performed in the right lobe and in the left lobe, both in neutral and in inspiration position. Results: LSM in the left lobe (8.39(±4.83)kPa) was significantly (p < .001) higher than LSM in the right lobe (6.27(±2.45)kPa). LSM in inspiration position (8.60(±4.33) kPa) was significantly (p = .009) higher than LSM in neutral position (7.70(±3.01)kPa). LSM in the left lobe overestimated the grade of fibrosis in 50.0% of the patients with CLD. However, correlation between LSM values right and left was strong (r = 0.856) and additional use of LSM in the left lobe increased the success rate from 106/116 (91.4%) to 112/116 (96.6%; p = .098). High skin-to-liver-capsule-distance and presence of ascites were independent risk factors for non-successful LSM. Conclusions: Despite significantly higher values, LSM in the left lobe may be an alternative if LSM in the right lobe is not feasible, and cirrhosis can be ruled out with high probability if LSM is within the normal range.

Liver Graft and Spleen Elastography After Living Liver Transplantation: Our First Results

AIM OF THE STUDY

Liver transplantation is widely applied as a standard and effective management of end-stage liver diseases, hepatocellular carcinoma, and acute liver failure. Investigation of morphologic and functional changes in the transplanted graft, gastrointestinal system, and spleen after transplantation is an important ground for assessment of post-transplantation results, early changes related to complications, and evaluation of response to treatment modalities. The aim of this study was to investigate the dynamics of changes in elastography of the liver graft and spleen after living-related liver transplantation.

MATERIAL AND METHODS

The study included 14 cirrhotic patients after living-related liver graft transplantation. Stiffness of the spleen and liver was evaluated before transplantation and at 1, 3, and 6 months after transplantation with a Supersonic Aixplorer Multi Wave device. Each procedure consisted of measuring the density in 10 points (spots) of the organ. The final result was calculated as the mean value of successful measurements (must have been > 60% of all measurements) and expressed in kilopascals.

RESULTS

The mean value of the liver and spleen stiffness before transplantation was 27 kPa (14-31 kPa) and 51 kPa (38-92 kPa), respectively. The stiffness of the spleen gradually reduced after transplantation to 40.3, 35.4, and 24.1 kPa (P = .001) at 1, 3, and 6 months. The stiffness of the liver graft in patients without complications was stable at 4-5 kPa, whereas the same value in patients with complications was increased (≥ 7.5 kPa). In 5 patients, endoscopic investigation confirmed the significant reduction of varicose veins after surgery.

CONCLUSION

Elastography of the liver graft and spleen after liver transplantation can be recommended as a useful-for-patient 1-off method of investigation.

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.

Impact of Food Intake on Liver Stiffness Determined by 2-D Shear Wave Elastography: Prospective Interventional Study in 100 Healthy Patients

The aim was to evaluate the influence of food intake on liver stiffness measurement (LSM), performed with 2-D shear wave elastography (Logiq E9, GE Medical Systems, Wauwatosa, WI, USA). One hundred healthy volunteers were prospectively enrolled. Mean age was 25.8 (19-55) y, and mean body mass index was 22.43 (17.3-30.8) kg/m². Patients fasted for at least 3 h and subsequently ingested a liquid meal of 800 kcal. Liver stiffness and portal vein velocity were measured before and after food intake. Food intake resulted in significantly higher LSM values compared with baseline LSM (5.74 ± 0.94 kPa vs. 4.80 ± 0.94 kPa, p < 0.001). On multiple linear regression analysis, body mass index was significantly positively correlated with the LSM increase after food intake (p = 0.01). No correlation between the increase in LSM and the increase in post-prandial portal vein velocity was observed (r = 0.09). In summary, food intake has a significant influence on LSM. There is an 11% risk of misclassifying non-fasting, healthy patients as having significant fibrosis.

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.

Point Shear Wave Elastography for Grading Liver Fibrosis: Can the Number of Measurements Be Reduced?

The aim of this study was to assess whether the number of liver point shear wave elastography (pSWE) measurements could be reduced compared with the currently recommended 10 valid measurements. Three thousand four hundred one pSWE examinations in patients with liver disease were performed with 10 consecutive valid measurements in liver segment 8. Liver fibrosis grading using published cutoff values were compared retrospectively using the median of 10 versus the first 1-9 measurements with Kendall's τ coefficient. Overall and binary (clinically significant [≥F2] versus non-significant [F0/F1]) fibrosis grading highly correlated when using 5-9 versus 10 valid measurements (τ = 0.96/0.95, p < 0.001). With the use of 5 valid measurements, a change in binary grading was observed in 87 of 3401 (2.6%) exams and only when velocities measured between 1.1 and 1.5 m/s. Therefore, using 5-9 valid measurements in pSWE of the liver results in a small portion of liver fibrosis grading misclassifications compared with use of 10 measurements and could help decrease scanning time, cost and discomfort in sonographers and patients.

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.

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.