Liver Elastography in Healthy Children Using Three Different Systems - How Many Measurements Are Necessary?

PURPOSE: Liver elastography is increasingly being applied in screening for and follow-up of pediatric liver disease, and has been shown to correlate well with fibrosis staging through liver biopsy. Because time is of the essence when examining children, we wanted to evaluate if a reliable result can be achieved with fewer acquisitions. MATERIALS AND METHODS: 243 healthy children aged 4-17 years were examined after three hours of fasting. Participants were divided into four age groups: 4-7 years; 8-11 years; 12-14 years and 15-17 years. Both two-dimensional shear wave elastography (2D-SWE; GE Logiq E9) and point shear wave elastography (pSWE; Samsung RS80A with Prestige) were performed in all participants, while transient elastography (TE, Fibroscan) was performed in a subset of 87 children aged 8-17 years. Median liver stiffness measurement (LSM) values of 3, 4, 5, 6, 7, and 8 acquisitions were compared with the median value of 10 acquisitions (reference standard). Comparison was performed for all participants together as well as within every specific age group. We investigated both the intraclass correlation coefficient (ICC) with absolute agreement and all outliers more than 10 %, 20 % or ≥ 0.5 or 1.0 kPa from the median of 10 acquisitions. RESULTS: For all three systems there was no significant difference between three and ten acquisitions, with ICCs ≥ 0.97. All systems needed 4 acquisitions to achieve no LSM deviating ≥ 1.0 kPa of a median of ten. To achieve no LSM deviating ≥ 20 % of a median of ten acquisitions, pSWE and TE needed 4 acquisitions, while 2D-SWE required 6 acquisitions. CONCLUSION: Our results contradict recommendations of 10 acquisitions for pSWE and TE and only 3 for 2D-SWE.

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.

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.

Repeatability of shear wave elastography in liver fibrosis phantoms-Evaluation of five different systems.

This study aimed to assess and validate the repeatability and agreement of quantitative elastography of novel shear wave methods on four individual tissue-mimicking liver fibrosis phantoms with different known Young's modulus. We used GE Logiq E9 2D-SWE, Philips iU22 ARFI (pSWE), Samsung TS80A SWE (pSWE), Hitachi Ascendus (SWM) and Transient Elastography (TE). Two individual investigators performed all measurements non-continued and in parallel. The methods were evaluated for inter- and intraobserver variability by intraclass correlation, coefficient of variation and limits of agreement using the median elastography value. All systems used in this study provided high repeatability in quantitative measurements in a liver fibrosis phantom and excellent inter- and intraclass correlations. All four elastography platforms showed excellent intra-and interobserver agreement (interclass correlation 0.981-1.000 and intraclass correlation 0.987-1.000) and no significant difference in mean elasticity measurements for all systems, except for TE on phantom 4. All four liver fibrosis phantoms could be differentiated by quantitative elastography, by all platforms (p<0.001). In the Bland-Altman analysis the differences in measurements were larger for the phantoms with higher Young's modulus. All platforms had a coefficient of variation in the range 0.00-0.21 for all four phantoms, equivalent to low variance and high repeatability.

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.

In Vitro Comparison of Five Different Elastography Systems for Clinical Applications, Using Strain and Shear Wave Technology.

Several different platforms providing ultrasound elastography have emerged in recent years. In this in vitro study on a single tissue-mimicking phantom (CIRS Model 49), we aimed to compare the performance of quantitative elastography measurements from platforms running strain elastography and others running shear wave elastography. We evaluated five different elastography platforms using both linear and curvilinear probes. All measurements were performed in parallel by two independent investigators who recorded the elasticity quantitatively. We investigated intra- and inter-observer agreement by intra-class correlation analysis and coefficient of variation, by correlation and limits of agreement. The reproducibility of elasticity measurements was good to excellent for shear wave and strain elastography. All five elastography platforms had high intra-observer (intra-class correlation coefficient: 0.932-1.0) and inter-observer correlation (intra-class correlation coefficient: 0.845-0.996). All inclusions could be differentiated by quantitative elastography by all systems (p < 0.001). The use of a linear probe yielded more reproducible measurements compared with use of a convex probe in 3/4 platforms.

Ultrasound and Point Shear Wave Elastography in Livers of Patients with Primary Sclerosing Cholangitis.

Point shear wave elastography (pSWE) is an ultrasound-based method for non-invasive quantification of liver fibrosis. The objective of this study was to explore liver pSWE in patients with primary sclerosing cholangitis (PSC) for assessment of fibrosis. Fifty-five non-transplant patients with PSC (38 males, 17 females; mean age: 46.4 y) were included and compared with 24 matched controls. Median (range) PSC duration was 8.1 (0-33) y. Ultrasonographic scanning followed by liver stiffness measurement by pSWE was performed using a conventional ultrasound system (Philips iU22). Signs of liver fibrosis on B-mode were identified in 21 patients (38%). Splenomegaly was found in 19 patients (35%) and ascites in two patients (4%). Successful pSWE measurements were achieved in the right liver lobe of all individuals and in the left liver lobe of 36 patients (65.5%). PSC patients had significantly higher median shear wave velocity (SWV) than controls in the right liver (median [range] SWV 1.26 [0.73-2.57] m/s vs. 1.09 [0.88-1.25] m/s, p < 0.001). SWV measured in the left liver lobe and spleen did not differ between PSC patients and controls. Our findings indicate that PSC patients have increased median SWV, indicating more fibrosis compared with controls; however, a wide range of SWV values were obtained among PSC patients, possibly reflecting the various stages in disease development.