Normal values of liver shear wave velocity in healthy children assessed by acoustic radiation force impulse imaging using a convex probe and a linear probe

Technical Notes on Liver Elastography: A Guide for Use in Neonates in Intensive Care Units

Background/Objectives: Liver elastography is increasingly used in neonatal intensive care units (NICUs) as a non-invasive, radiation-free, reproducible technique for assessing liver stiffness. This technique demonstrates substantial advantages over conventional ultrasound in diagnosing diffuse liver diseases by providing quantitative measures of tissue elasticity. This article aims to describe the most critical milestones for performing liver elastography ultrasound point-of-care, a tool increasingly used to complement traditional ultrasound in the study of the liver in intensive care units where the population is very susceptible to manipulation. Methods: Techniques such as point-shear wave elastography (pSWE) and two-dimensional shear wave elastography (2D-SWE) have become key in evaluating conditions such as hypoxic-ischemic liver disease, cholestatic diseases, storage and metabolic disorders, or infectious liver conditions. However, despite its usefulness, performing elastography in neonates, particularly in those weighing less than 1000 g or in high-frequency oscillatory ventilation, presents notable challenges, including the extreme sensitivity of neonates to touch, noise, and temperature changes and the difficulty in obtaining accurate measurements due to limited hepatic depth. Results: Key factors for the success of sonoelastography in this population include minimizing contact time, adjusting mechanical and thermal indices to meet biosecurity guidelines, and ensuring patient comfort and stability during the procedure. Despite these challenges, elastography has proven helpful in routine clinical practice. Conclusions: The growing evidence on elastography has provided standardized reference values, further enhancing its clinical applicability in NICU settings.

Two-dimensional shear wave elastography for assessing liver, spleen, and kidneys in healthy newborns

Aim

The aim of the study was to obtain two-dimensional shear wave elastography measurements of the liver, spleen and kidneys in healthy full-term newborns, as well as to assess its feasibility in this age group.

Materials and methods

We performed two-dimensional shear wave elastography of the liver, spleen and kidneys using a linear transducer at least 60 minutes after food intake in a group of 58 healthy, full-term, spontaneously breathing newborns. A series of 5 measurements using 5-mm-diameter regions of interest were performed, with the results expressed in m/s and kPa. Exam feasibility was assessed using the IQR/Median ratio as ≤30% for kPa, and ≤15% for m/s. Descriptive statistics, Shapiro-Wilk W, Levene's, Mann-Whitney U tests and Spearman correlation analysis were used for statistical assessment.

Results

The feasibility of the exam was 68.97% for the right liver lobe, 67.24% for the left lobe, 91.07% for the spleen, 89.29% for the right kidney, 85.71% for the left kidney. Mean results: right liver lobe: 1.43 m/s, SD ±0.11, 6.04 kPa, SD ±0.97, left liver lobe: 1.41 m/s, SD ±0.12, 5.86 kPa, SD ±1.02, spleen: 2.36 m/s, SD ±0.21, 16.99 kPa, SD ±3.21, right kidney: 1.92 m/s, SD ±0.18, 11.34 kPa, SD ±3.21, left kidney: 1.88 m/s, SD ±0.16, 10.81 kPa, SD ±1.80. The splenic-hepatic elastography index for m/s and kPa results was as follows: mean 1.65, SD ±0.20, mean 2.82, SD ±0.73, respectively. No differences were found between the right vs left lobe of the liver, or the right vs left kidney; there was no correlation between the measurements and gender or food intake interval >60 minutes. A positive correlation was found between the results for the right and left lobe of the liver and age, and the results for the left lobe of the liver and body weight.

Conclusions

Two-dimensional shear wave elastography of the liver, spleen and kidneys can be successfully performed in healthy neonates. We obtained reliable mean shear wave elastography values for the examined organs.

Liver fibrosis assessment in pediatric population - can ultrasound elastography be an alternative method to liver biopsy? A systematic review

Liver diseases of various etiologies are becoming increasingly common in the pediatric population. So far, the gold diagnostic standard in these disorders is liver biopsy. This procedure is invasive, painful and requires general anesthesia in this group of patients. Due to the continuous development of new research techniques, such as liver elastography, it is necessary to evaluate them in the context of their diagnostic usefulness. Ultrasound elastography, as a quick and effective method, is being used more and more often in the assessment and monitoring of liver dysfunction in both adults and children. There are several techniques of liver elastography, such as transient elastography, shear wave elastography consisting of various subtypes such as two-dimensional shear wave elastography, acoustic radiation force impulse and point shear wave elastography, which differ in terms of the measurement technique and the achieved results. The purpose of our review was to determine whether techniques of liver elastography could replace liver biopsy. Although now, based on the analyzed papers, elastography cannot replace liver biopsy, in our opinion, the role of this tool in monitoring pediatric patients with liver diseases will grow in the coming years.

Use of Virtual Touch Tissue Quantification Elastography Technique in Fetal Lung Maturation: A Preliminary Study

ABSTRACT

This study is an analysis of fetal lung stiffness by virtual touch tissue quantification (VTTQ) elastography to predict fetal lung maturation. Evaluation of fetal lungs was first performed in B mode, and fetal lungs were analyzed at 3 different periods at third trimester in each pregnant woman, at 28 to 31, 32 to 36, and 37 to 41 weeks. Fetal lung elastography was performed at regions with the least acoustic shadow and far from ribs and heart. Each fetal lung assessment were done by taking mean lung stiffness obtained by measuring stiffness of both left and right fetal lungs. T test analysis showed no significant difference in fetal lung stiffness between male and female fetuses among 3 gestational periods. Analysis of variance was performed to evaluate fetal lung stiffness of the fetuses at 3 different gestational periods (28-31, 32-36, and 37-41 weeks). This analysis showed significant difference ( P < 0.01). Duncan multiple comparison analysis did not show significant difference in fetal lung stiffness between 28 and 31 weeks and 32 and 36 weeks, whereas fetal lung stiffness of fetuses at 37 to 41 weeks were significantly greater ( P < 0.01). This study is first step to analyze fetal lung maturation noninvasively using VTTQ elastography technique by measuring fetal lung stiffness.

Point shear-wave elastography for the diagnosis of veno-occlusive disease in children and young adults

BACKGROUND

Hepatic veno-occlusive disease or sinusoidal obstruction syndrome is a potentially life-threatening complication of hematopoietic stem cell transplantation.

OBJECTIVE

To assess the usefulness of point shear-wave elastography (pSWE) for the early diagnosis of sinusoidal obstruction syndrome (SOS) in children.

MATERIALS AND METHODS

A retrospective study was carried out in 43 patients with suspected SOS assessed between March 2018 and November 2021. Diagnosis of SOS was confirmed in 28 patients based on the European Society for Blood and Marrow Transplantation diagnostic criteria. Abdominal ultrasound and pSWE of the liver were performed before and after hematopoietic stem cell transplantation on first suspicion of SOS.

RESULTS

Liver stiffness on initial suspicion was higher in patients diagnosed with SOS and these values increased compared to the pre-transplantation values. A cutoff value of 1.37 m/s was found for the diagnosis of SOS, with an area under the curve of 0.779 (95% CI 0.61-0.93).

CONCLUSION

Point shear wave elastography of the liver is a promising technique for the early diagnosis of pediatric SOS.

Clinical study of the value of shear wave elastography in evaluating the degree of liver fibrosis in children

OBJECTIVES

To explore the clinical application of shear wave elastography (SWE) in evaluating the degree of liver fibrosis in children.

METHODS

To explore the value of SWE in assessing liver fibrosis in children, the correlation between elastography values and the METAVIR grade of liver fibrosis in children with biliary system or liver diseases was studied. Children with significant liver enlargement were enrolled, and the fibrosis grade was analyzed to explore the value of SWE in assessing the degree of liver fibrosis in the presence of significant liver enlargement.

RESULTS

A total of 160 children with bile system or liver diseases were recruited. The areas under the receiver operating characteristic curve (AUROCs) for liver biopsy from stage F1 to F4 were 0.990, 0.923, 0.819, and 0.884. According to the degree of liver fibrosis at liver biopsy, there was a high correlation between the SWE value and the degree of liver fibrosis (correlation coefficient 0.74). There was no significant correlation between the Young's modulus value of the liver and the degree of liver fibrosis (correlation coefficient 0.16).

CONCLUSIONS

Supersonic SWE can generally accurately evaluate the degree of liver fibrosis in children with liver disease. However, When the liver is significantly enlarged, SWE can only evaluate liver stiffness based on Young's modulus values, and the degree of liver fibrosis must still be determined by pathologic biopsy.

Assessment of ultrasound shear wave elastography within muscles using different region of interest sizes, manufacturers, probes and acquisition angles: an ex vivo study

BACKGROUND

The application of shear wave elastography (SWE) in assessment of the musculoskeletal system is affected by various factors. This study aimed to explore the influence of machines, probes, region of interest (ROI) sizes, and the acquisition angles on muscle shear wave speed (SWS).

METHODS

The SWS of ex vivo isolated muscles were acquired using 3 different machines (Aixplorer system, SuperSonic Imagine; Acuson S3000, Siemens Healthcare; Resona 7, Mindray) and 2 linear probes (Aixplorer system, SL 10-2 and SL 15-4). Also, 4 different ROI sizes (diameter 1-10 mm) and 9 different acquisition angles (0-40°) were tested. The SWS acquired under different conditions were compared, and the intra-class correlation coefficients (ICC) were used to evaluate reproducibility.

RESULTS

There was a significant difference in SWS acquired using the 3 different machines (P<0.001) or with 9 different angles (P=0.008). There was no significant difference in SWS acquired using 2 probes (P=0.053) or 4 different ROI sizes (P=0.874, 0.778, and 0.865 for 3 operators, respectively). All machines produced substantial intra-system reproducibility (ICC, 0.61-0.80). Both probes demonstrated an almost perfect degree of intra-system agreement (ICC, >0.80), and nearly all ROI sizes demonstrated an almost perfect degree of intra- and inter-operator agreement (ICC, >0.80). The measurement reliability was higher when the acquisition angles were no more than 20°.

CONCLUSIONS

The 3 machines had different SWS values. Attention should be paid when comparing SWS results using different machines. For the Aixplorer system, the ROI size had no effect on the SWS values. Angles larger than 25° will lead to SWS measurements with greater variability compared to smaller angles (≤20°).

Sources of Variability in Shear Wave Speed and Dispersion Quantification with Ultrasound Elastography: A Phantom Study

There is a growing interest in quantifying shear-wave dispersion (SWD) with ultrasound shear-wave elastography (SWE). Recent studies suggest that SWD complements shear-wave speed (SWS) in diffuse liver disease diagnosis. To accurately interpret these metrics in clinical practice, we analyzed the impact of operator-dependent acquisition parameters on SWD and SWS measurements. Considered parameters were the acquisition depth, lateral position and size of the region of interest (ROI), as well as the size of the SWE acquisition box. Measurements were performed using the Canon Aplio i800 system (Canon Medical Systems, Otawara, Tochigi, Japan) and four homogeneous elasticity phantoms with certified stiffness values ranging from 3.7 to 44 kPa. In general, SWD exhibited two to three times greater variability than SWS. The acquisition depth was the main variance-contributing factor for both SWS and SWD, which decayed significantly with depth. The lateral ROI position contributed as much as the acquisition depth to the total variance in SWD. Locations close to the initial shear-wave excitation pulse were more robust to biases because of inaccurate probe-phantom coupling. The size of the ROI and acquisition box did not introduce significant variations. These results suggest that future guidelines on multiparametric elastography should account for the depth- and lateral-dependent variability of measurements.

Ultrasound shear wave elastography: does it add value to gray-scale ultrasound imaging in differentiating biliary atresia from other causes of neonatal jaundice?

BACKGROUND

Neonatal/infantile jaundice is relatively common, and most cases resolve spontaneously. However, in the setting of unresolved neonatal cholestasis, a prompt and accurate assessment for biliary atresia is vital to prevent poor outcomes.

OBJECTIVE

To determine whether shear wave elastography (SWE) alone or combined with gray-scale imaging improves the diagnostic performance of US in discriminating biliary atresia from other causes of neonatal jaundice over that of gray-scale imaging alone.

MATERIALS AND METHODS

Infants referred for cholestatic jaundice were assessed with SWE and gray-scale US. On gray-scale US, two radiology readers assessed liver heterogeneity, presence of the triangular cord sign, hepatic artery size, presence/absence of common bile duct and gallbladder, and gallbladder shape; associated interobserver correlation coefficients (ICC) were calculated. SWE speeds were performed on a Siemens S3000 using 6C2 and 9 L4 transducers with both point and two-dimensional (2-D) SWE US. Both univariable and multivariable analyses were performed, as were receiver operating characteristic curves (ROC) and statistical significance tests (chi-squared, analysis of variance, t-test and Wilcoxon rank sum) when appropriate.

RESULTS

There were 212 infants with biliary atresia and 106 without biliary atresia. The median shear wave speed (SWS) for biliary atresia cases was significantly higher (P<0.001) than for non-biliary-atresia cases for all acquisition modes. For reference, the median L9 point SWS was 2.1 m/s (interquartile range [IQR] 1.7-2.4 m/s) in infants with biliary atresia and 1.5 m/s (IQR 1.3-1.9 m/s) in infants without biliary atresia (P<0.001). All gray-scale US findings were significantly different between biliary-atresia and non-biliary-atresia cohorts (P<0.001), intraclass correlation coefficient (ICC) range 0.7-1.0. Triangular cord sign was most predictive of biliary atresia independent of other gray-scale findings or SWS - 96% specific and 88% sensitive. Multistep univariable/multivariable analysis of both gray-scale findings and SWE resulted in three groups being predictive of biliary atresia likelihood. Abnormal common bile duct/gallbladder and enlarged hepatic artery were highly predictive of biliary atresia independent of SWS (100% for girls and 95-100% for boys). Presence of both the common bile duct and the gallbladder along with a normal hepatic artery usually excluded biliary atresia independent of SWS. Other gray-scale combinations were equivocal, and including SWE improved discrimination between biliary-atresia and non-biliary-atresia cases.

CONCLUSION

Shear wave elastography independent of gray-scale US significantly differentiated biliary-atresia from non-biliary-atresia cases. However, gray-scale findings were more predictive of biliary atresia than elastography. SWE was useful for differentiating biliary-atresia from non-biliary-atresia cases in the setting of equivocal gray-scale findings.

Paediatric gastrointestinal and hepatobiliary radiology: why do we need subspecialists, and what is new?

We present the case for subspecialisation in paediatric gastrointestinal and hepato-pancreatico-biliary radiology. We frame the discussion around a number of questions: What is different about the paediatric patient and paediatric gastrointestinal system? What does the radiologist need to do differently? And finally, what can be translated from these subspecialty areas into everyday practice? We cover conditions that the sub-specialist might encounter, focusing on entities such as inflammatory bowel disease and hepatic vascular anomalies. We also highlight novel imaging techniques that are a focus of research in the subspecialties, including contrast-enhanced ultrasound, MRI motility, magnetisation transfer factor, and magnetic resonance elastography.

Acoustic radiation force impulse imaging: normal values of spleen stiffness in healthy children

BACKGROUND

Acoustic radiation force impulse (ARFI) imaging is a noninvasive ultrasound elastography technique for evaluating tissue stiffness. The association of liver and spleen stiffness provides additional information in the assessment of portal hypertension. The technique and normal values of spleen stiffness by point shear wave elastography (p-SWE) in pediatrics have not been well documented.

OBJECTIVE

Our aim is to describe the feasibility and normal ARFI elastography values in the spleen for healthy children and to compare measurements in two different probe positions (the axial and sagittal planes).

MATERIALS AND METHODS

Spleen p-SWE using ARFI values were measured with a 6C1 probe in 102 healthy children (age range: 8 weeks to 17 years) divided into four age groups. An average of nine (standard deviation: two) spleen stiffness measurements were taken during free breathing in each plane (axial and sagittal). The impact of age and measurement plane in the spleen was analyzed using multivariate models.

RESULTS

There was no significant difference in spleen stiffness values taken at different ages, with an average of the medians of 2.43±0.31 m/s. There was no significant difference based on probe orientation: sagittal plane (median: 2.46±0.29 m/s) and axial plane (median: 2.43±0.32 m/s) with Student's t-test P=0.18. The mean depth of measurement varied between 2.3 cm and 3.7 cm, according to age.

CONCLUSION

Normal spleen stiffness values using ARFI imaging in children do not vary with age and correspond to a median of 2.43 m/s. No significant difference was found when using different probe positions.

Splenic stiffness and platelet count to predict varices needing treatment in pediatric extrahepatic portal vein obstruction

BACKGROUND

Surveillance endoscopy to detect varices needing treatment (VNT) is important to prevent bleeding and morbidity in portal hypertension. In adult and pediatric cirrhosis, platelet count and liver stiffness measurement (LSM) are useful in selecting patients for endoscopy. Such recommendations do not exist for extrahepatic portal vein obstruction (EHPVO). Splenic stiffness measurement (SSM) has been studied in adult and pediatric EHPVO with conflicting results and methodological errors. This study evaluates the role of platelet counts and SSM to predict VNT and bleeding in pediatric EHPVO while comparing LSM and SSM between pediatric EHPVO and controls.

METHODS

One hundred and seven children (55 with EHPVO and 52 controls) were recruited. Clinical, biochemical, hematological, and radiographic parameters of all children were noted. All children with EHPVO underwent endoscopy.

RESULTS

Of the 55 children with EHPVO, 48 (87.3%) had VNT. There was no difference in the platelet counts (85,000/mm³ vs. 120,000/mm³, p = 0.58) and SSM (3.62 vs. 3.19, p = 0.05) between EHPVO children with VNT and those without. They had poor sensitivity and specificity to predict VNT. EHPVO children with bleeding had higher SSM that those without. LSM was higher among EHPVO than among controls (1.19 vs. 1.10, p = 0.003). Those with LSM higher than controls had normal liver histology.

CONCLUSION

SSM is higher in EHPVO bleeders but SSM and platelet counts are unreliable to predict VNT in pediatric EHPVO. Surveillance endoscopies may be needed in all pediatric EHPVO until better screening strategies are available.

TRIAL REGISTRATION

Not applicable.

Shear wave velocity by quantitative acoustic radiation force impulse in the placenta of normal and high-risk pregnancy

Background

Traditionally, the placental functional integrity is suggested by indirect ultrasound measurements like fetal growth, amniotic fluid index, and uterine and umbilical artery Doppler indices. Only recently the elasticity of the placenta is studied as a measure of placental consistency and biomechanical prosperities and may reflect the placental function. Shear wave velocity is the quantitative parameter of the shear wave elastography. A high-risk pregnancy is a situation which puts the mother, the fetus, or both at greater risk than a normal pregnancy.

Results

The shear wave velocity (SWV) showed no significant difference between the placenta of normal pregnancies in the second and third trimesters (0.85 ± 0.43 m/s and 0.89 ± 0.57 m/s, respectively). The placenta of patients with preeclampsia/eclampsia had high SWV in the second and third trimesters (2.13 ± 1.48 m/s and 2.23 ± 1.48 m/s) with a highly significant difference from the normal placenta (P < 0.001). The placentas with abnormal location (placenta previa) and penetration (placenta accreta) had higher SWV than the placenta of normal pregnancies. The mean SWV for placenta previa was 1.1 ± 0.74 m/s and 1.3 ± 0.81 m/s in the second and third trimesters, respectively, with a mildly significant difference with the normal placenta. The placenta accreta shows high mean SWV in the second and third trimesters (1.6 ± 0.65 m/s and 1.961.6 ± 0.65, respectively) which differed significantly (P < 0.001) from SWV in the normal placenta in the second and third trimesters.

Conclusion

Shear wave velocity measurement as the quantitative parameter of acoustic radiation force impulse (ARFI) elastography reflects the placental elasticity in normal and high-risk pregnancies. The SWV increases in conditions like hypertension, preeclampsia, maternal renal disease, and diabetes and reflects the structural and biomechanical abnormalities in such diseases. High shear wave velocity correlates with the incidence of growth restriction and abnormal Doppler parameters especially in the hypertensive disease. The virtual touch quantification (VTQ) can be used as a complementary diagnostic and prognostic tool in high-risk pregnancy.

Diagnostic performance of non-invasive tests for evaluation of hepatic graft fibrosis in pediatric liver transplantation: A scoping review

BACKGROUND

Hepatic graft fibrosis is a common histologic finding of pediatric liver transplant (LT) that might affect long-term graft outcome. However, its diagnosis and staging require an invasive liver biopsy.

AIM

To review the published literature on the diagnostic accuracy of elastography and serum-based fibrosis markers for assessing hepatic graft fibrosis in pediatric LT recipients.

METHODS

A scoping review was conducted using a systematic search of published literature in PubMed (MEDLINE), EMBASE, SCOPUS, and Cochrane Library between 2002 and 2019. We included all English conference abstracts or full-text articles that examined the diagnostic accuracy of the non-invasive test(s) to assess hepatic fibrosis in LT children, using liver biopsy as the reference test.

RESULTS

Eight studies were included, of which 6 examined transient elastography (TE), one investigated acoustic radiation force impulse elastography, and 5 examined serum-based fibrosis markers (AST/ALT ratio, AST-to-platelet ratio index, FibroTest, enhanced liver fibrosis test). TE reportedly had a good AUROC (range: 0.82-0.92) to distinguish children with hepatic graft fibrosis (≥F1) from those with no fibrosis. However, there was considerable overlap of liver stiffness cutoffs in the mild to significant fibrosis groups (≥F1 and ≥F2). Current serum-based fibrosis markers reportedly had an unsatisfactory diagnostic accuracy.

CONCLUSIONS

TE in LT children has similar diagnostic value and limitations as in the non-transplant setting. Prospective studies are warranted to validate an optimal liver stiffness cutoff for predicting significant hepatic graft fibrosis (≥F2) and to determine if a meaningful change in liver stiffness from baseline could identify patients at risk for fibrosis progression.

Comparison of acoustic radiation force impulse imaging with the convex probe 6C1 and linear probe 9L4

BACKGROUND

Acoustic radiation force impulse imaging (ARFI) is a noninvasive method to detect liver fibrosis. The aims of the study were to evaluate the difference between 2 different probes, 6 C1 and 9 L4, and to study inter- and intraobserver reproducibility for the probes.

METHODS

We enrolled 100 patients in this cross-sectional comparative study. All patients underwent liver stiffness measurement with both probes. Intraobserver, interobserver, intralobe, and interlobe agreement was analyzed using the intraclass correlation coefficient.

RESULTS

A significant difference in success rates was observed for both probes between the right and left liver lobes. A success rate of 91% was observed in the right liver lobe compared with 77% in the left liver for the convex probe (P = .007), and 91% vs 68% for the linear probe (P < .001). There was a significant correlation in ARFI-shear wave velocity (ARFI-SWV) between both probes in the right liver lobe (P = .01; r = .508) and in the left liver lobe (P = .05; r = .278); however, there was no significant correlation in ARFI-SWV between the liver lobes for both probes (convex probe r = .19 P = .112; linear probe r = .144 P = .23). Good or excellent inter- and intraobserver was detected for both probes. Poor agreement was found only for the interobserver agreement in the left lobe with the convex probe (ICC = .320).

CONCLUSION

ARFI can be performed successfully with both probes in both liver lobes. There was no significant correlation in ARFI between the liver lobes for both probes; however, the right liver lobe should be favored. Standardization of the procedure is needed for the comparability of different studies.

The effect of placental elasticity on intraoperative bleeding in pregnant women with previous cesarean section

Background We aimed to evaluate the efficiency of placental elasticity in predicting the amount of intraoperative bleeding via real-time tissue elastography technique. Methods Pregnant women in the third trimester of pregnancy who had planned delivery via cesarean section due to the recurrent cesareans were enrolled in the research (n = 78). Elastographic measurements of placental tissues of all cases were carried out by real-time elastographic ultrasonography. It is a tissue elastography software (Esaote MyLabSeven) that uses a 8-1-MHz multifrequency AC2541 Probe. Results A significant relationship was found between placental elasticity and intraoperative bleeding. There was a significant correlation between alterations in the preoperative and postoperative hemoglobin (Hb) and hematocrit (Hct) levels and placental strain ratio (SR) (P < 0.001, r: 0.831; P < 0.001, r: 0.733, respectively). Conclusion These findings may reflect an alteration at the tissue elasticity level. We hope that the use of real-time elastographic ultrasonography technique may give an idea about the amount of bleeding during the cesarean section.

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.

Normal values of shear wave velocity in liver tissue of healthy children measured using the latest acoustic radiation force impulse technology

BACKGROUND

Several studies have demonstrated the feasibility and effectiveness of using ultrasound elastography to assess liver tissue stiffness. Virtual touch imaging quantification (VTIQ) based on acoustic radiation force impulse imaging has been developed as a latest and noninvasive method for assessing liver stiffness in children.

AIM

To determine the standard value in healthy children, and to identify possible factors that might influence the VTIQ measurement.

METHODS

With the ethical approval, 202 children between 1 month and 15 years old were included in this study. None of them had any liver or systematic diseases. All children had a normal ultrasound scan and normal body mass index (BMI) range. The subjects were divided into four age and BMI groups. The effects of gender, age, liver lobe, measurement depth, and BMI on liver elasticity were investigated.

RESULTS

A significant correlation was found between age and shear wave velocity (SWV) value. At measurement depths of 1.5 cm and 2.0 cm in the left lobe, there were significant differences among the age groups. SWV values were significantly negatively correlated with the measurement depth. Gender, liver lobe, and BMI showed no significant effect on the SWV values. Age and BMI may influence the quality of the elastogram.

CONCLUSION

VTIQ is a noninvasive technique that is feasible to measure liver stiffness in children. The afore-mentioned velocity value obtained utilizing VTIQ method could be used as reference value for normal liver stiffness in children.

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.

Technical performance of shear wave elastography for measuring liver stiffness in pediatric and adolescent patients: a systematic review and meta-analysis

OBJECTIVE

To assess the technical performance (proportion of technical failure and unreliable measurements) of shear wave elastography (SWE) for assessing liver stiffness in pediatric and adolescent patients.

METHODS

We searched Ovid-MEDLINE and EMBASE databases for eligible studies and selected original articles investigating transient elastography (TE), point shear wave elastography (pSWE), or two-dimensional SWE (2D-SWE) for measuring liver stiffness in pediatric and adolescent patients. A quantitative synthesis of studies reporting technical failures and/or unreliable measurements of TE, pSWE, or 2D-SWE is presented. Meta-analytic pooling was conducted using the random effects model. Meta-regression analysis was conducted to explore potential causes of heterogeneity.

RESULTS

Forty of 69 studies (58%) provided technical performance information. Technical failure data were reported in 3 TE, 6 pSWE, and 8 2D-SWE studies. Unreliable measurement data were provided in 21 TE, 4 pSWE, and 1 2D-SWE study. The pooled proportion of unreliable measurements of TE was 12.1%. Meta-regression analysis showed that the study population size and readers' blinding to pathologic results affected the study's heterogeneity. The pooled proportions of technical failure during pSWE and 2D-SWE were 4.1% and 2.2%, respectively, demonstrating no significant difference between the techniques.

CONCLUSIONS

We reviewed the technical performance of SWE, especially the rate of unreliable measurements from TE studies and rates of technical failure from pSWE and 2D-SWE studies. Considering the importance of technical performance for clinical validation of SWE, numbers of and reasons for technical failure and unreliable measurements should be reported in future studies. Further efforts are necessary to standardize SWE reliability criteria.

KEY POINTS

• Most TE studies reported rate of unreliable measurements, whereas pSWE and 2D-SWE studies were likely to report rates of technical failure. • The pooled proportion of unreliable measurements of TE was 12.1%. • The pooled proportions of technical failure during pSWE and 2D-SWE were 4.1% and 2.2%, respectively, demonstrating no significant difference between the techniques.

Liver Ultrasound Elastography: An Update to the World Federation for Ultrasound in Medicine and Biology Guidelines and Recommendations

The World Federation for Ultrasound in Medicine and Biology has produced these guidelines for the use of elastography techniques in liver diseases. For each available technique, the reproducibility, results and limitations are analyzed, and recommendations are given. This set of guidelines updates the first version, published in 2015. Since the prior guidelines, there have been several advances in technology. The recommendations are based on the international published literature, and the strength of each recommendation is judged according to the Oxford Centre for Evidence-Based Medicine. The document has a clinical perspective and is aimed at assessing the usefulness of elastography in the management of liver diseases.

Current Knowledge in Ultrasound-Based Liver Elastography of Pediatric Patients

Studies performed using transient elastography (TE), point shear wave elastography (pSWE) and two-dimensional shear wave elastography (2D-SWE) have shown that these techniques are all feasible and accurate in children for the evaluation of liver fibrosis due to several etiologies. However, for some specific pediatric pathologies, such as biliary atresia, the evidence is still limited. As shown in adults, inflammation is a confounding factor when assessing fibrosis severity and care should be taken when interpreting the results. Due to the scarce comparative data between serological tests and elastography techniques in children, a definite conclusion regarding which is the best cannot be drawn. Neither non-invasive elastographic techniques nor laboratory scores allow determination of the presence and the degree of inflammation, necrosis, iron or copper deposits.

The search for noninvasive methods to identify liver fibrosis in children with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the obesity epidemic. Recent studies have clearly shown that the stage of fibrosis in adults with NAFLD is the most important histological feature in long-term outcomes and the development of liver-related complications. Despite the paucity of data regarding the natural history of pediatric NAFLD, its progression to cirrhosis and end-stage liver disease requiring liver transplantation is well documented. Given the high prevalence of NAFLD in children and adults, there is an urgent need to find safe and cost-effective alternatives to biopsy to determine the stage of liver fibrosis. In this review, we provide a concise overview of different noninvasive methods for diagnosing and staging liver fibrosis in children with NAFLD.

Acoustic radiation force impulse imaging for detection of liver fibrosis in overweight and obese children

Background Acoustic radiation force impulse (ARFI) is a non-invasive alternative to a liver biopsy for the evaluation of liver fibrosis (LF). Purpose To investigate the potential usefulness of acoustic radiation force impulse ARFI for detecting LF in overweight and obese children Material and Methods A cross-sectional study was conducted in 148 schoolchildren. A diagnosis of non-alcoholic fatty liver disease (NAFLD) and LF was based on ultrasound (US) and ARFI shear wave velocity (SWV). Results The laboratory parameters were normal in all the children. NAFLD was observed in 50 children (33.8%). The median SWV was 1.18 ± 0.28 m/s. Differences between ARFI categories and hepatic steatosis grades were observed (χ2 = 43.38, P = 0.0005). No fibrosis or insignificant fibrosis (SWV ≤ 1.60 m/s) was detected in 137 children (92.5%), and significant fibrosis (SWV > 1.60 m/s) in 11 children (7.5%), nine of whom had normal US or mild steatosis. Conclusion The present study is the first to evaluate the utility of the ARFI technique for detecting LF in overweight and obese children. The results of the study suggest that children with normal laboratory parameters such as normal liver ultrasound or mild steatosis may present with significant LF.

Evaluation of Liver, Kidney, and Spleen Elasticity in Healthy Newborns and Infants Using Shear Wave Elastography

OBJECTIVES

Elasticity measurements of tissues can be valuable in the diagnosis and management of various diseases. The aim of this study was to determine the elasticity values for normal liver, kidney, and spleen of healthy newborns and infants using shear wave elastography (SWE) imaging.

METHODS

A total of 50 healthy term newborns and infants (19 girls and 31 boys; mean age 20.1 days, range 1 to 70 days) were examined by an experienced pediatric radiologist using SWE. None of them had any liver, kidney or spleen disease, or any other systemic disease that could affect these organs secondarily. All newborns and infants had a normal abdominal ultrasound scan.

RESULTS

Age, sex, weight, height, and body mass index had no significant effects on shear wave velocity (SWV) values of liver and spleen. The SWV values of both kidneys decreased with age, weight, height, and body mass index. The mean SWV values were 1.70 m/s (range: 1.23-2.43 m/s) for the liver, 1.69 m/s (range: 0.8-2.40 m/s) for the right kidney, 1.70 m/s (range: 0.9-2.49 m/s) for the left kidney, and 2.03 m/s (range: 1.28-2.48 m/s) for the spleen.

CONCLUSIONS

Shear wave elastography can be used to measure liver, kidney, and spleen elasticity in newborns and infants. The standard values for abdominal organs allow differentiation of healthy versus pathological tissue. We measured the normal values of SWE in healthy newborns and infants as reference data.

Liver stiffness measurements with supersonic shear wave elastography in the diagnosis of biliary atresia: a comparative study with grey-scale US

OBJECTIVES

To prospectively assess the diagnostic performance of supersonic shear wave elastography (SSWE) in identifying biliary atresia (BA) among infants with conjugated hyperbilirubinaemia by comparing this approach with grey-scale ultrasonography (US).

METHODS

Forty infants were analysed as the control group to determine normal liver stiffness values. The use of SSWE values for identifying BA was investigated in 172 infants suspected of having BA, and results were compared with the results obtained by grey-scale US. The Mann-Whitney U test, unpaired t-test, Spearman correlation and linear regression were also performed.

RESULTS

The success rates of SSWE measurements in the control and study group were 100% (40/40) and 96.4% (244/253), respectively. Age, direct bilirubin, and indirect bilirubin all significantly correlated with SSWE in the liver (all P < 0.001). Linear regression showed that age had a greater effect on SSWE values than direct or indirect bilirubin. The diagnostic performance of liver stiffness values in identifying BA was lower than that of grey-scale US (area under the receiver operating characteristic curve [AUC], 0.790 vs 0.893, P < 0.001).

CONCLUSIONS

SSWE is feasible and valuable in differentiating BA from non-BA. However, its diagnostic performance does not exceed that of grey-scale US.

KEY POINTS

• SSWE could be successfully performed in an infant population. • For infants, the liver stiffness will increase as age increases. • SSWE is potentially useful in assessing infants suspected of biliary atresia. • SSWE is inferior to grey-scale US in identifying biliary atresia.

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.

Optimal Acquisition Number for Hepatic Shear Wave Velocity Measurements in Children

OBJECTIVE

To investigate the minimum optimal acquisition number of hepatic shear wave velocities (SWVs) on ultrasound elastography in children.

MATERIALS AND METHODS

We prospectively performed hepatic supersonic shear wave elastography in children of four groups (group A-C, healthy children, group A with 0-5 years old; group B with 6-10 years old; group C with 11-18 years old; and group D, children with previous Kasai operation) with free breathing (FB) and breath holding (BH) status, if possible. SWVs were measured fifteen times for each child at a 4 cm depth for the right lobe using a 1-6 MHz convex transducer. Mean SWVs from three, five, and seven acquisitions were compared to the mean SWV from fifteen measurements, using an intraclass correlation coefficient (ICC) analyzed with the 1,000 times bootstrap method.

RESULTS

Total eighty-eight children were included (25 children in group A, 30 children in group B, 21 children in group C, and 12 children in group D). The mean SWVs from fifteen measurements in FB status were 5.5 ± 1.3 kPa for groups A-C together and 8.0 ± 2.2 kPa for group D. For all groups together, mean SWVs from the three (ICC 0.944 and 0.937), five (ICC 0.958 and 0.938) and seven (ICC 0.969 and 0.941) acquisitions demonstrated almost perfect agreement with the reference of fifteen acquisitions in both FB and BH status, respectively. A subgroup analysis showed three measurements were in almost perfect agreement during FB for groups B-D and strong agreement (ICC 0.675) for group A.

CONCLUSION

Three acquisitions can be enough for hepatic SWVs in children more than 6 years old regardless of breathing status or hepatic pathology. More acquisitions are recommended for children under the age of 5 years during FB.

Diagnostic Performance of MR Elastography and Vibration-controlled Transient Elastography in the Detection of Hepatic Fibrosis in Patients with Severe to Morbid Obesity

Purpose To evaluate the diagnostic performance and examination success rate of magnetic resonance (MR) elastography and vibration-controlled transient elastography (VCTE) in the detection of hepatic fibrosis in patients with severe to morbid obesity. Materials and Methods This prospective and HIPAA-compliant study was approved by the institutional review board. A total of 111 patients (71 women, 40 men) participated. Written informed consent was obtained from all patients. Patients underwent MR elastography with two readers and VCTE with three observers to acquire liver stiffness measurements for liver fibrosis assessment. The results were compared with those from liver biopsy. Each pathology specimen was evaluated by two hepatopathologists according to the METAVIR scoring system or Brunt classification when appropriate. All imaging observers were blinded to the biopsy results, and all hepatopathologists were blinded to the imaging results. Examination success rate, interobserver agreement, and diagnostic accuracy for fibrosis detection were assessed. Results In this obese patient population (mean body mass index = 40.3 kg/m²; 95% confidence interval [CI]: 38.7 kg/m², 41.8 kg/m²]), the examination success rate was 95.8% (92 of 96 patients) for MR elastography and 81.3% (78 of 96 patients) or 88.5% (85 of 96 patients) for VCTE. Interobserver agreement was higher with MR elastography than with biopsy (intraclass correlation coefficient, 0.95 vs 0.89). In patients with successful MR elastography and VCTE examinations (excluding unreliable VCTE examinations), both MR elastography and VCTE had excellent diagnostic accuracy in the detection of clinically significant hepatic fibrosis (stage F2-F4) (mean area under the curve: 0.93 [95% CI: 0.85, 0.97] vs 0.91 [95% CI: 0.83, 0.96]; P = .551). Conclusion In this obese patient population, both MR elastography and VCTE had excellent diagnostic performance for assessing hepatic fibrosis; MR elastography was more technically reliable than VCTE and had a higher interobserver agreement than liver biopsy. ^© RSNA, 2016 Online supplemental material is available for this article. An earlier incorrect version of this article appeared online. This article was corrected on January 25, 2017.

Ultrasound Elastography Is Useful for Evaluation of Liver Fibrosis in Children-A Systematic Review

OBJECTIVES

Adult studies have proven ultrasound elastography as a validated measure of liver fibrosis. The present study aimed to review the available literature on ultrasound elastography in children to evaluate the ability of the method to distinguish healthy from fibrotic liver tissue and investigate whether cutoff values for liver fibrosis in children have been established.

METHODS

A literature search was performed in MEDLINE, EMBASE, the Cochrane Library, and Web of Science to identify studies on ultrasound elastography of the liver in children. Only original research articles in English concerning ultrasound elastography in children with and without liver disease, younger than 18 years, were included. All reference lists of the included articles were hand-searched for further references.

RESULTS

Twenty-seven articles were included. Elastography in children without liver disease was investigated in 14 studies and were comparable to those existing for adults. Twelve studies compared elastography with liver biopsy in children with liver disease and found that cirrhosis was correctly diagnosed, whereas it was more difficult to assess severe fibrosis correctly. For the distinction between no, mild, and moderate fibrosis in children with liver disease the method was less accurate. Ultrasound elastography was able to differentiate between children with and without liver fibrosis. In children without liver disease ultrasound, elastography showed consistent liver stiffness values comparable to those found in adults. No fibrosis-specific cutoffs were proposed.

CONCLUSIONS

Ultrasound elastography was able to diagnose cirrhosis, distinguish healthy from fibrotic liver tissue, and showed consistent liver stiffness values in children without liver disease.

ARFI: from basic principles to clinical applications in diffuse chronic disease-a review

Abstract

The many factors influencing the shear wave velocity (SWV) measured with Acoustic Radiation Force Impulse (ARFI) are examined in order to define the most correct examination technique. In particular, attention is given to the information achieved by experimental models, such as phantoms and animal studies. This review targets the clinical applications of ARFI in the evaluation of chronic diffuse disease, especially of liver and kidneys. The contribution of ARFI to the clinical workout of these patients and some possible perspectives are described.

Teaching Points

• Stiffness significantly varies among normal and abnormal biological tissues.

• In clinical applications physical, geometrical, anatomical and physiological factors influence the SWV.

• Elastographic techniques can quantify fibrosis, which is directly related to stiffness.

• ARFI can be useful in chronic diffuse disease of liver and kidney.

Measurement of elasticity of normal placenta using the Virtual Touch quantification technique

PURPOSE

The aim of this study was to measure the elasticity of normal placentas using the Virtual Touch quantification (VTQ) technique.

METHODS

This study was approved by the Institutional Ethics Committee. Fifty randomly selected, healthy pregnant women in their second trimester and 50 randomly selected, healthy pregnant women in their third trimester with a single fetus were included, and their placentas underwent VTQ through shear wave velocity (SWV) measurements. The measurements were performed at different locations to sample different areas of the placenta. Measurements were performed 3-4 times in each location, the mean shear wave velocities were calculated without the highest and lowest values of measurements in each region, and the results were compared.

RESULTS

The SWV of the placenta was 0.983±0.260 m/sec, and the minimal and maximal speed was 0.63 m/sec and 1.84 m/sec, respectively. There was no significant difference between the second and third trimester of VTQ of the placenta in terms of SWV (0.978±0.255 m/sec vs. 0.987±0.266 m/sec, P=0.711). The maternal age between second and third trimester was 27.9±4.3 years and 29.2±4.4 years, respectively; there was no significant difference between them (P=0.159).

CONCLUSION

The results of this study show that the SWV of normal placenta tissue is 0.983±0.260 m/sec, it has little variation between the second and third trimesters, and the VTQ technique may potentially play an additional role in placenta evaluation.

Primary biliary cirrhosis degree assessment by acoustic radiation force impulse imaging and hepatic fibrosis indicators

AIM: To evaluate the assessment of primary biliary cirrhosis degree by acoustic radiation force impulse imaging (ARFI) and hepatic fibrosis indicators.

METHODS: One hundred and twenty patients who developed liver cirrhosis secondary to primary biliary cirrhosis were selected as the observation group, with the degree of patient liver cirrhosis graded by Child-Pugh (CP) score. Sixty healthy individuals were selected as the control group. The four indicators of hepatic fibrosis were detected in all research objects, including hyaluronic acid (HA), laminin (LN), type III collagen (PC III), and type IV collagen (IV-C). The liver parenchyma hardness value (LS) was then measured by ARFI technique. LS and the four indicators of liver fibrosis (HA, LN, PC III, and IV-C) were observed in different grade CP scores. The diagnostic value of LS and the four indicators of liver fibrosis in determining liver cirrhosis degree with PBC, whether used alone or in combination, were analyzed by receiver operating characteristic (ROC) curve.

RESULTS: LS and the four indicators of liver fibrosis within the three classes (A, B, and C) of CP scores in the observation group were higher than in the control group, with C class > B class > A class; the differences were statistically significant (P < 0.01). Although AUC values of LS within the three classes of CP scores were higher than in the four indicators of liver fibrosis, sensitivity and specificity were unstable. The ROC curves of LS combined with the four indicators of liver fibrosis revealed that: AUC and sensitivity in all indicators combined in the A class of CP score were higher than in LS alone, albeit with slightly decreased specificity; AUC and specificity in all indicators combined in the B class of CP score were higher than in LS alone, with unchanged sensitivity; AUC values (0.967), sensitivity (97.4%), and specificity (90%) of all indicators combined in the C class of CP score were higher than in LS alone (0.936, 92.1%, 83.3%).

CONCLUSION: The diagnostic value of PBC cirrhosis degree in liver cirrhosis degree assessment by ARFI combined with the four indicators of serum liver fibrosis is of satisfactory effectiveness and has important clinical application value.

White Paper on P4 Concepts for Pediatric Imaging

Over the past decade, innovations in the field of pediatric imaging have been based largely on single-center and retrospective studies, which provided limited advances for the benefit of pediatric patients. To identify opportunities for potential "quantum-leap" progress in the field of pediatric imaging, the ACR-Pediatric Imaging Research (PIR) Committee has identified high-impact research directions related to the P4 concept of predictive, preventive, personalized, and participatory diagnosis and intervention. Input from 237 members of the Society for Pediatric Radiology was clustered around 10 priority areas, which are discussed in this article. Needs within each priority area have been analyzed in detail by ACR-PIR experts on these topics. By facilitating work in these priority areas, we hope to revolutionize the care of children by shifting our efforts from unilateral reaction to clinical symptoms, to interactive maintenance of child health.

Comparison of shear wave velocities on ultrasound elastography between different machines, transducers, and acquisition depths: a phantom study

OBJECTIVES

To investigate consistency in shear wave velocities (SWVs) on ultrasound elastography using different machines, transducers and acquisition depths.

METHODS

The SWVs were measured using an elasticity phantom with a Young's modulus of 16.9 kPa, with three recently introduced ultrasound elastography machines (A, B and C from different vendors) and two transducers (low and high frequencies) at four depths (2, 3, 4 and 5 cm). Mean SWVs from 15 measurements and coefficient of variations (CVs) were compared between three machines, two transducers and four acquisition depths.

RESULTS

The SWVs using the high frequency transducer were not acquired at 5 cm depth in machine B, and a high frequency transducer was not available in machine C. The mean SWVs in the three machines were different (p ≤ 0.002). The CVs were 0-0.09 in three machines. The mean SWVs between the two transducers were different (p < 0.001) except at 4 and 5 cm depths in machine A. The SWVs were affected by the acquisition depths in all conditions (p < 0.001).

CONCLUSION

There is considerable difference in SWVs on ultrasound elastography depending on different machines, transducers and acquisition depths. Caution is needed when using the cutoff values of SWVs in different conditions.

KEY POINTS

• The shear wave velocities (SWVs) are different between different ultrasound elastography machines • The SWVs are also different between different transducers and acquisition depths • Caution is needed when using the cutoff SWVs measured under different conditions.

New combined parameter of liver and splenic stiffness as determined by elastography in healthy volunteers

BACKGROUND

The diagnosis of chronic liver disease (CLD) leading to fibrosis, cirrhosis, and portal hypertension had witnessed dramatic changes after the introduction of noninvasive figure accessible tools over the past few years. Imaging techniques that are based on evaluation of the liver stiffness was particularly useful in this respect. Acoustic radiation force impulse (ARFI) emerged as an interesting figure tool with reliable repute and high precision.

AIMS

To evaluate liver stiffness measurement (LSM) and splenic stiffness measurement (SSM) in healthy volunteers as concluded by the ARFI technique and to out a numeric calculated ratio that may reflect their correlation in the otherwise healthy liver.

PATIENTS AND METHODS

A ratio (splenic stiffness/liver stiffness in kPa) was determined in 207 consenting healthy subjects and was investigated with respect to age, gender, ethnic origin, body mass index (BMI), liver and spleen sizes healthy volunteers, alanine aminotransferase (ALT), aspartate aminotransferase (AST), platelet count (PLT), APRI, and FIB-4 scores.

RESULTS

Data from this work led to computing an index of 4.72 (3.42-7.33) in healthy persons on an average. Females had a higher index than males 6.37 vs 4.92, P=0.002. There was not any significant difference of the ratio in different age groups; ethnic origins; any correlation between SSM/LSM ratio and BMI; liver and spleen sizes; or ALT, AST, PLT, APRI, and FIB-4 scores.

CONCLUSIONS

A quantifiable numeric relationship between splenic and liver stiffness in the healthy subjects could be computed to a parameter expressed as SSM/LSM ratio. We believe that this ratio can be a useful reference tool for further researches in CLD.

Quantitative Shear-Wave Elastography of the Liver in Preterm Neonates with Intra-Uterine Growth Restriction

The feasibility and reproducibility of liver stiffness measurements using Supersonic Shear-wave Imaging (SSI) in preterm neonate have not been reported. Our aim was to determine if liver stiffness differs between intra-uterine growth restriction (IUGR) and appropriate for gestational age (AGA) preterm infants with/without cholestasis. We measured liver stiffness (in kPa) in 45 AGA and 18 IUGR preterm infants, and assessed reproducibility in 26 preterms using Intraclass Correlation Coefficients (ICC) and Bland-Altman tests. Liver stiffness values were compared between AGA and IUGR with and without cholestasis and correlated with birth weight. Measurements showed high reproducibility (ICC = 0.94–0.98 for intra-operator, 0.86 for inter-operator) with good agreement (95% limits: -1.24 to 1.24 kPa). During the first postnatal week, liver stiffness was higher in IUGR (7.50 ±1.53 kPa) than in AGA infants (5.11 ±0.80 kPa, p<0.001). After day 8, liver stiffness remained unchanged in AGA but increased progressively in IUGR infants (15.57 ±6.49 kPa after day 21). Liver stiffness was higher in IUGR neonates with cholestasis (19.35 ± 9.80 kPa) than without cholestasis (7.72 ± 1.27 kPa, p<0.001). In conclusion, quantitative liver SSI in preterms is feasible and reproducible. IUGR preterms who will develop cholestasis present high liver stiffness even at birth, before biological cholestasis occurs.

Hepatic and Splenic Acoustic Radiation Force Impulse Shear Wave Velocity Elastography in Children with Liver Disease Associated with Cystic Fibrosis

BACKGROUND

Liver disease associated with cystic fibrosis (CFLD) is the second cause of mortality in these patients. The diagnosis is difficult because none of the available tests are specific enough. Noninvasive elastographic techniques have been proven to be useful to diagnose hepatic fibrosis. Acoustic radiation force impulse (ARFI) imaging is an elastography imaging system. The purpose of the work was to study the utility of liver and spleen ARFI Imaging in the detection of CFLD. Method. 72 patients with cystic fibrosis (CF) were studied and received ARFI imaging in the liver and in the spleen. SWV values were compared with the values of 60 healthy controls. Results. Comparing the SWV values of CFLD with the control healthy group, values in the right lobe were higher in patients with CFLD. We found a SWV RHL cut-off value to detect CFLD of 1.27 m/s with a sensitivity of 56.5% and a specificity of 90.5%. CF patients were found to have higher SWC spleen values than the control group. Conclusions. ARFI shear wave elastography in the right hepatic lobe is a noninvasive technique useful to detect CFLD in our sample of patients. Splenic SWV values are higher in CF patients, without any clinical consequence.

Ultrasound shear wave speed measurements correlate with liver fibrosis in children

BACKGROUND

Little published research has shown the relationship between noninvasive US shear wave speed (SWS) measurements and degree of liver fibrosis as established by percutaneous biopsy in children.

OBJECTIVE

To assess the relationship between liver US shear wave speed (SWS) measurements and parenchymal fibrosis in children.

MATERIALS AND METHODS

Sixty-two children (0-18 years old) with known or suspected liver disease underwent same-day US shear wave elastography (SWE) and clinically ordered percutaneous core needle biopsy. SWE was performed just before the liver biopsy in the area targeted for sampling, using an Acuson S3000 US system with a 9L4 transducer; six SWS measurements were acquired using Virtual Touch Quantification (VTQ) and Virtual Touch IQ (VTIQ) modes. Biopsy specimens were scored for histological fibrosis and inflammation. Bivariate relationships were assessed using Pearson correlation, while multiple linear regression analysis was used to establish the relationship between SWS and predictor variables. Receiver operating characteristic (ROC) curves were created to assess the abilities of VTQ and VTIQ to discern low vs. high liver fibrosis (histological fibrosis scores 0-2 vs. 3-6).

RESULTS

There were significant positive correlations between liver histological fibrosis score and VTQ (n = 49) and VTIQ (n = 48) mean shear wave speed measurements (r = 0.68 and r = 0.73; P-values <0.0001). There also were significant positive correlations between liver histological inflammation score and VTQ and VTIQ mean shear wave speed measurements (r = 0.47 and r = 0.44, and P = 0.0006 and P = 0.0016, respectively). For VTQ, both histological fibrosis (P < 0.0001) and inflammation (P = 0.04) scores were significant predictors of shear wave speed (model adjusted R (2) = 0.49). For VTIQ, only histological fibrosis score (P < 0.0001) was a significant predictor of shear wave speed (model adjusted R (2) = 0.56). ROC areas under the curve were 0.84 and 0.86 for VTQ and VTIQ, respectively.

CONCLUSION

Liver US shear wave speed measurements increase with increasing parenchymal fibrosis in children.

Feasibility and Diagnostic Accuracy of Supersonic Shear-Wave Elastography for the Assessment of Liver Stiffness and Liver Fibrosis in Children: A Pilot Study of 96 Patients

PURPOSE

To evaluate the feasibility of using supersonic shear-wave elastography (SSWE) in children and normal values of liver stiffness with the use of control patients of different ages (from neonates to teenagers) and the diagnostic accuracy of supersonic shear wave elastography for assessing liver fibrosis by using the histologic scoring system as the reference method in patients with liver disease, with a special concern for early stages of fibrosis.

MATERIALS AND METHODS

The institutional review board approved this prospective study. Informed consent was obtained from parents and children older than 7 years. First, 51 healthy children (from neonate to 15 years) were analyzed as the control group, and univariate and multivariate comparisons were performed to study the effect of age, transducer, breathing condition, probe, and position on elasticity values. Next, 45 children (from 1 month to 17.2 years old) who underwent liver biopsy were analyzed. SSWE measurements were obtained in the same region of the liver as the biopsy specimens. Biopsy specimens were reviewed in a blinded manner by a pathologist with the use of METAVIR criteria. The areas under the receiver operating characteristics curve (AUCs) were calculated for patients with fibrosis stage F0 versus those with stage F1-F2, F2 or higher, F3 or higher, and F4 or higher.

RESULTS

A successful rate of SSWE measurement was 100% in 96 patients, including neonates. Liver stiffness values were significantly higher when an SC6-1 probe (Aixplorer; SuperSonic Imagine SA, Aix-enProvence, France) was used than when an SL15-4 probe (Aixplorer) was used (mean ± standard deviation, 6.94 kPa ± 1.42 vs 5.96 kPa ± 1.31; P = .006). There was no influence of sex, the location of measurement, or respiratory status on liver elasticity values (P = .41-.93), although the power to detect such a difference was low. According to the degree of liver fibrosis at liver biopsy, 88.5%-96.8% of patients were correctly classified, with AUCs of 0.90-0.98 (95% confidence interval [CI]: 0.8, 1.0). The AUC for patients with stage F0 versus stage F1-F2 was 0.93 (95% CI: 0.87, 0.99).

CONCLUSION

SSWE allows accurate assessment of liver fibrosis, even in children with early stage (F1-F2) disease, and the choice of transducer influences liver stiffness values.

Normal values of spleen stiffness in healthy children assessed by acoustic radiation force impulse imaging (ARFI): comparison between two ultrasound transducers

BACKGROUND

Portal hypertension, a major complication of hepatic fibrosis, can affect the stiffness of the spleen.

OBJECTIVE

To suggest normal values of spleen stiffness determined by acoustic radiation force impulse imaging in healthy children and to compare measurements using two different US probes.

MATERIALS AND METHODS

In a prospective study, 60 healthy children between 1 day and 14 years of age were assigned to four age groups with 15 children in each. Measurements were performed using two transducers (convex 4C1 and linear 9L4), and 10 measurements were obtained in each child, 5 with each probe.

RESULTS

The mean splenic shear wave velocities were 2.17 m/s (SD 0.35, 95% CI 2.08-2.26) with the 4C1 probe and 2.15 m/s (SD 0.23, 95% CI 2.09-2.21) with the 9L4 probe (not significant).

CONCLUSION

We found normal values for spleen stiffness with no difference in the mean values obtained using two types of US transducers, but with higher variability using a convex compared to a linear transducer.

Evaluation of Acoustic Radiation Force Impulse Imaging (ARFI) for the Determination of Liver Stiffness Using Transient Elastography as a Reference in Children

PURPOSE

Transient elastography (Fibroscan(©); (FS)) and acoustic radiation force impulse imaging (ARFI) represent noninvasive, user-friendly and quick methods providing an objective and reproducible measure of liver stiffness. The aim of the study was to evaluate cut-off values and performance of ARFI measurements in children using transient elastography as a reference.

METHODS/PATIENTS

A total of 198 children were enrolled in this study. All patients underwent liver stiffness measurements with FS (FS-LS) as well as ARFI (with shear wave velocity quantification; ARFI-SWV) and the performance of ARFI in comparison to FS was studied.

RESULTS

Significantly higher rates of successful measurements were found for ARFI compared to FS (198/198 (100%) vs. 160/198 (80.8%); p<0.001). ARFI-SWV correlated significantly with FS-LS (r=0.751, p=0.001). ARFI-SWV increased significantly with the stage of fibrosis (1.19+0.15 m/s for patients with FS-LS<7.6 kPa); 1.34+0.22 m/s for patients with 7.613.0 kPa). ARFI-SWV cut-off values were identified for no significant fibrosis (1.31 m/s; sensitivity 61.8% and specificity 79.5%) and for liver cirrhosis (1.63 m/s; sensitivity 70.0% and specificity 97.4%). The median values of liver stiffness measured by FS were age-dependent in 90 children without liver diseases with 4.8, 5.6, and 5.7 kPa in children 0-5, 6-11, and 12-18 years, respectively.