Hepatic shear wave elastography in children under free-breathing and breath-hold conditions

Applicability of multiple quantitative ultrasound liver biomarkers in children and adolescents with severe obesity

BACKGROUND

Obesity is associated with chronic liver disease, which is why improved non-invasive diagnostic assessment of liver affection is desirable. The ultrasound-based biomarkers Attenuation Imaging coefficient (ATI), Shear Wave Elastography (SWE), and Shear Wave Dispersion (SWD) have the potential to assess liver steatosis, fibrosis and inflammation/oedema respectively. The aim was therefore to evaluate the feasibility of applying ultrasound-based liver biomarkers in children and adolescents with severe obesity.

METHODS

Ultrasound was performed, before treatment, in 56 patients with childhood obesity (< 18 years) referred for bariatric surgery or treatment with glucagon-like peptide-1 receptor agonists. An ultrasound visualisation score (A: no limitations - D: severe limitations) was used. ATI, SWE and SWD were measured, irrespective of visualisation score, and compared to clinical data, serological measures and depth of measurement. Scan-rescan reproducibility measurements were performed, both for continuous measures using intraclass correlation coefficient (ICC) and for kappa coefficient using proposed reference thresholds for elevated/pathological values in children during fasting and free-breathing: > ATI 0.56 dB/cm/MHz, > SWE 4.9 kPa and > SWD 11.9 (m/s)/kHz.

RESULTS

The median (min-max) age of the 56 patients (51.8% male) was 16.2 years (9.9; 18) and the median BMI standard deviation score (SDS) was 4.4 (2.7; 7.3). The distribution of the visibility score was A 5.5%, B 50%, C 41% and D 3.5%. The median (min-max) ATI, SWE and SWD values were 0.58 dB/cm/MHz (0.32; 0.97), 7.2 kPa (4.3; 19.6) and 14.3 (m/s)/kHz (8.9; 24.3) respectively. Both ATI (β = -4.2; r2 = 0.3; p < 0.0001) and SWD (β = 0.14; r2 = 0.17; p = 0.0033) were influenced by depth of measurement. A weak association was found between ATI and serum triglycerides (β = 0.07; r2 = 0.12; p = 0.015). SWE was associated with BMI-SDS (β = 0.71; r2 = 0.09; p = 0.035). No other significant associations were found. ICC was moderate for ATI (0.61), fair for SWE (0.46) and fair for SWD (0.51). Kappa coefficient was substantial for ATI (0.77), excellent for SWE (1.0) and moderate for SWD (0.53).

CONCLUSION

When accounting for visualization score, multiple ultrasound liver biomarkers appear applicable in most children and adolescents with severe obesity. Median ATI, SWE and SWD values were all increased, compared to currently known paediatric normal values. However, median ATI was likely underestimated due to depth dependence of measurement. Although caution is advised in clinical decision-making due to fair-moderate reproducibility between scans, most importantly, the biomarkers appear capable of differentiating between non-affected and affected liver in children with severe obesity.

Ultrasound innovations in abdominal radiology: techniques and clinical applications in pediatric imaging

Contrast-enhanced ultrasound, microvascular imaging, elastography, and fat quantification have varying degrees of utility, with some applications in the pediatric setting mirroring that in adults and having unique uses when applied to children in others. This review will present novel ultrasound technologies and the clinical context in which they are applied to the pediatric abdomen. New ultrasound technologies have a broad range of applications in clinical practice and represent a powerful diagnostic tool with the potential to replace other imaging modalities, such as magnetic resonance imaging and computed tomography, in specific cases.

Quantitative Liver Imaging in Children

ABSTRACT

In children and adults, quantitative imaging examinations determine the effectiveness of treatment for liver disease. However, pediatric liver disease differs in presentation from liver disease in adults. Children also needed to be followed for a longer period from onset and have less control of their bodies, showing more movement than adults during imaging examinations, which leads to a greater need for sedation. Thus, it is essential to appropriately tailor and accurately perform noninvasive imaging tests in these younger patients. This article is an overview of updated imaging techniques used to assess liver disease quantitatively in children. The common initial imaging study for diffuse liver disease in pediatric patients is ultrasound. In addition to preexisting echo analysis, newly developed attenuation imaging techniques have been introduced to evaluate fatty liver. Ultrasound elastography is also now actively used to evaluate liver conditions, and the broad age spectrum of the pediatric population requires caution to be taken even in the selection of probes. Magnetic resonance imaging (MRI) is another important imaging tool used to evaluate liver disease despite requiring sedation or anesthesia in young children because it allows quantitative analysis with sequences such as fat analysis and MR elastography. In addition to ultrasound and MRI, we review quantitative imaging methods specifically for fatty liver, Wilson disease, biliary atresia, hepatic fibrosis, Fontan-associated liver disease, autoimmune hepatitis, sinusoidal obstruction syndrome, and the transplanted liver. Lastly, concerns such as growth and motion that need to be addressed specifically for children are summarized.

Unveiling the potential of ultrasound in brain imaging: Innovations, challenges, and prospects

Within medical imaging, ultrasound serves as a crucial tool, particularly in the realms of brain imaging and disease diagnosis. It offers superior safety, speed, and wider applicability compared to Magnetic Resonance Imaging (MRI) and X-ray Computed Tomography (CT). Nonetheless, conventional transcranial ultrasound applications in adult brain imaging face challenges stemming from the significant acoustic impedance contrast between the skull bone and soft tissues. Recent strides in ultrasound technology encompass a spectrum of advancements spanning tissue structural imaging, blood flow imaging, functional imaging, and image enhancement techniques. Structural imaging methods include traditional transcranial ultrasound techniques and ultrasound elastography. Transcranial ultrasound assesses the structure and function of the skull and brain, while ultrasound elastography evaluates the elasticity of brain tissue. Blood flow imaging includes traditional transcranial Doppler (TCD), ultrafast Doppler (UfD), contrast-enhanced ultrasound (CEUS), and ultrasound localization microscopy (ULM), which can be used to evaluate the velocity, direction, and perfusion of cerebral blood flow. Functional ultrasound imaging (fUS) detects changes in cerebral blood flow to create images of brain activity. Image enhancement techniques include full waveform inversion (FWI) and phase aberration correction techniques, focusing on more accurate localization and analysis of brain structures, achieving more precise and reliable brain imaging results. These methods have been extensively studied in clinical animal models, neonates, and adults, showing significant potential in brain tissue structural imaging, cerebral hemodynamics monitoring, and brain disease diagnosis. They represent current hotspots and focal points of ultrasound medical research. This review provides a comprehensive summary of recent developments in brain imaging technologies and methods, discussing their advantages, limitations, and future trends, offering insights into their prospects.

Changes in Liver Shear Wave Elastography of Preterm Infants during Hospitalization

OBJECTIVE

 Liver evaluation is essential in preterm infants because of exposure to hepatotoxic drugs, the effects of parenteral nutrition, and their organ immaturity. The clinical significance of shear wave elastography (SWE) which measures tissue elasticity, is unclear in preterm infants. For SWE application to liver evaluation in preterm infants, we examined the postnatal course and factors associated with changes.

STUDY DESIGN

 We prospectively measured liver SWE values every other week in 37 preterm infants born at 23 to 35 weeks gestation and 12 term infants born after 36 weeks gestation.

RESULTS

 The median early postnatal liver SWE value was 1.22 (interquartile range, 1.19-1.26) m/s. The correlations of liver SWE values with gestational age and birth weight were r = -0.18 (p = 0.23) and r = -0.21 (p = 0.157), respectively. The median liver SWE values from birth to 36 to 38 postmenopausal weeks were 1.22 (1.17-1.24) m/s at <28 weeks gestation (n = 9), 1.21 (1.18-1.25) m/s at 28 to 29 weeks gestation (n = 11), 1.24 (1.21-1.28) m/s at 30 to 31 weeks gestation (n = 8), and 1.21 (1.20-1.24) m/s at ≥32 weeks gestation (n = 9). There was no change over time in any gestational age group (p = 0.158). The median liver SWE values were 1.22 (1.17-1.25) m/s (n = 10) and 1.22 (1.19-1.25) m/s (n = 27) for small- and appropriate-for-gestational-age infants, respectively (p = 0.93). The correlations of abnormally high serum concentrations of direct bilirubin (>1.0 mg/dL) and alanine aminotransferase (>12 IU/L) with liver SWE values were r = 0.37 (p = 0.041) and r = 0.21 (p = 0.35), respectively.

CONCLUSION

 Liver SWE values may be useful for the evaluation of liver damage with cholestasis in preterm infants because they remain constant regardless of gestational age and birth weight and do not change over time or with a deviation of body size.

KEY POINTS

· Liver SWE was prospectively performed in preterm infants.. · Liver SWE was constant until term regardless of gestational age or birth weight.. · Liver SWE values of preterm infants ranged from 1.2 to 1.3 m/s.. · For preterm infants, elevation of liver SWE values reflected cholestasis.. · Liver SWE may become the new standard for liver evaluation in preterm infants..

Impact of Respiratory Motion on the Quantification of Pediatric Hepatic Steatosis Using Two Different Ultrasonography Machines

PURPOSE

This study aimed to investigate the effect of respiratory motion on hepatic steatosis quantification using ultrasound attenuation imaging (ATI) or ultrasound-guided attenuation parameter (UGAP) in pediatric patients.

MATERIALS AND METHODS

Pediatric patients (aged ≤18 years) who underwent liver ultrasonography (US) with ATI or UGAP between May 2022 and February 2023 were included retrospectively. Median, interquartile range (IQR), and IQR/median values were calculated in both free-breathing (FB) and breath-holding (BH) states. Subjects were divided into normal and fatty liver groups according to grayscale US. Wilcoxon signed rank test, intraclass correlation coefficient (ICC), and linear regression test were used.

RESULTS

A total of 83 patients (M:F=46:37, median age 10 years, range 6-17 years) was included, with 55 patients in the ATI group and 28 patients in the UGAP group. The measured values of ATI and UGAP were not significantly different between FB and BH. The ICC values between FB and BH states were 0.950 [95% confidence interval (CI) 0.916-0.971] for median ATI and 0.786 (95% CI 0.591-0.894) for median UGAP. FB and BH status did not significantly affect the median ATI and UGAP (p=0.852, 0.531, respectively). The IQR/median value showed a significant association with age only in the FB status of the normal group using ATI (β= -0.014, p=0.042).

CONCLUSION

Respiratory motion does not significantly affect the measurement of ATI or UGAP. Median ATI value showed excellent agreement in FB and BH status, while UGAP showed good agreement. Younger age may affect measurement variability in FB status of the normal group using ATI.

Evaluation of Hepatic Shear Wave Elastography to Assess Liver Fibrosis in Biliary Atresia Patients and Its Correlation with Liver Histology and Surgical Outcomes: A Prospective Observational Study

Introduction  The native liver survival in biliary atresia (BA) depends on various factors, and one of the crucial factors is the rate of progression of liver fibrosis after portoenterostomy, but there is no reliable investigation to assess it. This study evaluated shear wave elastography (SWE) to detect liver fibrosis in BA patients and assess its utility during follow-up. Materials and Methods  This was an observational study; SWE was done preoperatively and postoperatively at 3 and 6 months. The SWE values were analyzed to determine their correlations with preoperative liver histology as well as with postoperative SWE variation between different postoperative outcomes. Results  Twenty-one patients were included in the study; the preoperative SWE values were strongly correlated with liver biopsy grading ( p  < 0.001). At the 3 months postoperatively, SWE was done for 18 children: 12 in group A (patent bilioenteric drainage on hepatobiliary iminodiacetic acid scan) and 6 (nonpatent) in group B; mean SWE value was 12.8 and 17.3 kPa, respectively ( p  < 0.001). Ten children from group A underwent SWE 6 months postoperatively, and the mean value was 13.23 kPa. Conclusion  The SWE values correlate with liver histology grading, suggesting a reliable alternative to biopsy. Additionally, the baseline SWE values and their trend during follow-up can provide information on the disease's progression.

Weight-specific normal liver stiffness values in children

BACKGROUND

Two-dimensional (2-D) shear wave elastography is a commonly used sonographic elastography method for the noninvasive measurement of liver stiffness. There is little liver stiffness data available in the pediatric population and its association with the child's weight is scarce.

OBJECTIVE

The principal aim of our study was to determine weight-specific reference liver stiffness values in a pediatric population free of liver disease.

MATERIALS AND METHODS

In this retrospective single-center study, 2-D shear wave elastography values were recorded in children with no history of liver disease and with a clinically indicated ultrasound examination, between April 2021 and July 2022. Examinations were performed using an Aplio i800 and two Aplio a450 (Canon Medical Systems), with a convex probe (i8CX1 or 8C1 transducers). This population was divided into ten weight groups. We evaluated the relation between weight and liver elasticity values and compared right and left lobe measurements.

RESULTS

During the period of the study, 235 children were included. We then excluded 64 patients (weight not available = 13, interquartile range to median ratio (IQR/M) greater than 30% = 51). On the final sample (171 patients, median age 6.5 years [0-18], median weight 22.6 kg [2.5-80]), stiffness values showed a global significant trend to increase with weight. In each group, there was no significant difference between right and left liver stiffness values. The mean normal liver stiffness value including all children was 5.3 ± 1.1 kPa.

CONCLUSION

Liver stiffness in our pediatric sample with no history of liver disease increases with weight. These data may help to distinguish normal from pathological elastography values.

WFUMB Guideline/Guidance on Liver Multiparametric Ultrasound: Part 1. Update to 2018 Guidelines on Liver Ultrasound Elastography

The World Federation for Ultrasound in Medicine and Biology (WFUMB) endorsed the development of this document on multiparametric ultrasound. Part 1 is an update to the WFUMB Liver Elastography Guidelines Update released in 2018 and provides new evidence on the role of ultrasound elastography in chronic liver disease. The recommendations in this update were made and graded using the Oxford classification, including level of evidence (LoE), grade of recommendation (GoR) and proportion of agreement (Oxford Centre for Evidence-Based Medicine [OCEBM] 2009). The guidelines are clinically oriented, and the role of shear wave elastography in both fibrosis staging and prognostication in different etiologies of liver disease is discussed, highlighting advantages and limitations. A comprehensive section is devoted to the assessment of portal hypertension, with specific recommendations for the interpretation of liver and spleen stiffness measurements in this setting.

Shear wave elastography and dispersion imaging for hepatic veno-occlusive disease prediction after pediatric hematopoietic stem cell transplantation: a feasibility study

BACKGROUND

Non-invasive imaging modalities are warranted for diagnosing and monitoring veno-occlusive disease because early diagnosis and treatment improve the prognosis.

OBJECTIVE

To evaluate the usefulness of liver shear wave elastography (SWE) and shear wave dispersion (SWD) imaging in diagnosing and monitoring veno-occlusive disease in pediatric patients.

MATERIALS AND METHODS

We conducted a prospective cohort study at a single tertiary hospital from March 2021 to April 2022. The study protocol included four ultrasound (US) sessions: a baseline US and three follow-up US after hematopoietic stem cell transplantation. Clinical criteria, including the European Society for Blood and Marrow Transplantation criteria, were used to diagnose veno-occlusive disease. We compared clinical factors and US parameters between the veno-occlusive disease and non-veno-occlusive disease groups. The diagnostic performance of US parameters for veno-occlusive disease was assessed by plotting receiver operating characteristic (ROC) curves. We describe temporal changes in US parameters before and after veno-occlusive disease diagnosis.

RESULTS

Among the 38 participants (mean age 10.7 years), eight developed veno-occlusive disease occurring 17.0 ± 5.2 days after hematopoietic stem cell transplantation. Liver stiffness, as measured by SWE (15.0 ± 6.2 kPa vs. 5.8 ± 1.8 kPa; P<0.001), and viscosity, as assessed with SWD (17.7 ± 3.1 m/s/kHz vs. 14.3 ± 2.8 m/s/kHz; P=0.015), were significantly higher in the veno-occlusive disease group compared to the non-veno-occlusive disease group at the time of diagnosis. Liver stiffness demonstrated the highest area under the ROC (AUROC) curves at 0.960, with an optimal predictive value of >6.5 kPa, resulting in sensitivity and specificity of 100% and 83.3%, respectively. Viscosity demonstrated an AUROC of 0.783, with an optimal cutoff value of 13.9 m/s/kHz for predicting veno-occlusive disease, with a sensitivity of 100% and specificity of 53.3%, respectively. Liver stiffness increased with disease severity and decreased during post-treatment follow-up.

CONCLUSION

SWE may be a promising technique for early diagnosis and severity prediction of veno-occlusive disease. Furthermore, liver viscosity assessed by SWD may serve as an additional marker of veno-occlusive disease.

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.

Do Ultrasound Based Quantitative Hepatic Fat Content Measurements Have Differences Between Respiratory Phases?

RATIONALE AND OBJECTIVES

The recently developed ultrasound based tools using attenuation coefficient (AC) and scatter distribution coefficient (SDC) values can be used to quantify hepatic fat content in patients with non-alcoholic fatty liver disease (NAFLD). However, currently the impact of respiratory phase on these measurements is not known. The purpose of this study is to compare AC and SDC measurements acquired at peak inspiration and end expiration phases.

MATERIALS AND METHODS

AC and SDC measurements were obtained in 50 patients with NAFLD. Tissue Attenuation Imaging (TAI) and Tissue Scatter Distribution Imaging (TSI) tools were utilized to measure AC and SDC values, respectively. Five measurements were performed at respiratory phases using TAI and TSI tools and the median values were noted. Subgroup analyses were performed and Wilcoxon signed rank test was used for comparison of the measurements.

RESULTS

The median values of the AC measurements at peak inspiration and end expiration phases were 0.87 dB/cm/MHz and 0.89 dB/cm/MHz, respectively. The median values of the SDC measurements at peak inspiration and end expiration phases were 97.91 and 96.62, respectively. There were no statistically significant differences in AC and SDC measurements between the respiratory phases except for AC measurements in BMI <30 kg/m2 subgroup.

CONCLUSION

Our results revealed that respiratory phases have no impact on SDC measurements. However, while the AC measurements in BMI ≥30 kg/m2 subgroup showed no significant difference, there was a significant difference in AC measurements in BMI <30 kg/m2 subgroup between the respiratory phases.

Ultrasound Elastography in Children

Ultrasound elastography is a novel ultrasound technique, being extensively researched in children in the last decade. It measures tissue elasticity with the observation of tissue response after an external stimulus. From research to clinical practice, ultrasound elastography has evolved significantly in liver fibrosis evaluation in children; however, several other applications of the technique are available in both clinical practice and research environments. Practically, in children any organ can be assessed, including the brain in early ages, along with muscle and connective tissue elasticity evaluation, spleen, kidney, skin, lymphatic tissue, etc. The elastography method, age, body mass index and technical points should be considered when performing ultrasound elastography. This review highlights its vast potential as a diagnostic tool in the pediatric population, where ultrasound is a dominant imaging tool; however, the indications and exam protocol for its clinical use in several fields in pediatrics have yet to be elucidated.

Liver cirrhosis in children - the role of imaging in the diagnostic pathway

Liver cirrhosis in children is a rare disease with multifactorial causes that are distinct from those in adults. Underlying reasons include cholestatic, viral, autoimmune, hereditary, metabolic and cardiac disorders. Early detection of fibrosis is important as clinical stabilization or even reversal of fibrosis can be achieved in some disorders with adequate treatment. This article focuses on the longitudinal evaluation of children with chronic liver disease with noninvasive imaging tools, which play an important role in detecting cirrhosis, defining underlying causes, grading fibrosis and monitoring patients during follow-up. Ultrasound is the primary imaging modality and it is used in a multiparametric fashion. Magnetic resonance imaging and computed tomography are usually applied second line for refined tissue characterization, clarification of nodular lesions and full delineation of abdominal vessels, including portosystemic communications.

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.

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

Introduction

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

Methods

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

Results

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

Conclusions

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

Ultrasound elastography in children - nice to have for scientific studies or arrived in clinical routine?

Ultrasound elastography (USE) is a modality that in addition to fundamental B-mode, Doppler, and contrast-enhanced sonography is suitable to make qualitative and quantitative statements about the stiffness of tissues. Introduced more than 20 years ago in adults, USE becomes now a diagnostic tool also in children. The aim of this paper is to describe current available techniques for USE in children. The significance for routine use in children is shown, and further interesting applications are reported.

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

Background

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

Purpose

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

Materials and Methods

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

Results

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

Conclusion

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

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.

Development and Validation of a Nomogram Incorporating Ultrasonic and Elastic Findings for the Preoperative Diagnosis of Biliary Atresia

RATIONALE AND OBJECTIVES

To develop and validate a nomogram that incorporates the gallbladder morphology, hepatic elasticity, and demographic information for the prediction of biliary atresia (BA) in children.

MATERIALS AND METHODS

A total of 294 consecutive patients under the age of 70 days with cholestasis and suspected symptoms of BA were enrolled in this study, who were divided into a training cohort (150 patients) and a validation cohort (144 patients). Ultrasonography and two-dimensional shear wave elastography were performed for each patient prior to knowing the final diagnosis. Multivariate logistic regression was used to analyze the gallbladder morphologic feature in the sonogram (absence of gallbladder, small gallbladder, lower postprandial gallbladder contractibility, or abnormal gallbladder wall), hepatic elasticity and clinical data from the training cohort, and a diagnostic nomogram for BA was subsequently developed. The performance of the nomogram was respectively evaluated with respect to the discrimination and calibration in every cohort.

RESULTS

The multivariate analysis showed that the factors of age (p = 0.009), gallbladder morphology (p = 0.001) and hepatic elasticity (p < 0.001) could serve as independent predictive factors to differentiate between BA and other causes of cholestasis. The nomogram incorporating these three parameters showed good discrimination and satisfactory calibration, indicating a better performance compared to using only the gallbladder morphologic features and hepatic elasticity. The observed area under the receiver operator characteristic curve in the training cohort and validation cohort was 0.939 (p < 0.001) and 0.942 (p < 0.001), respectively, with a sensitivity of 95.5% and a specificity of 83.4% in the combined cohort.

CONCLUSION

The established nomogram shows a favored and improved predictive value for the diagnosis of BA.

Liver shear wave elastography and attenuation imaging coefficient measures: prospective evaluation in healthy children

PURPOSE

Ultrasonographic quantitative measurements enable characterizing the stiffness and viscosity of liver parenchyma. Normal Shear Wave Elastography (SWE) values have been reported in adults and children. The Attenuation Imaging (ATI) coefficient is a measure of local sound energy loss thought to reflect steatosis in adults. The aim of our study was to provide normal SWE and ATI liver values in healthy children.

METHODS

A prospective monocentric study was conducted recruiting 86 children (45 boys and 41 girls) from a single University Hospital between January 2019 and June 2020, having a clinically indicated ultrasound examination, without a known or documented history of liver disease. Examinations were performed using an Aplio i800 (Canon Medical Systems) ultrasound system with an i8CX1 transducer. SWE measurements were obtained using a color map showing an automated measurement area grid overlay. ATI coefficients were generated automatically for each region of interest in the right liver.

RESULTS

Overall median age for the pediatric population was 106 months (1-180 months; SD 49 months). Children were normal weighted. Liver SWE was available for all children. The median liver SWE was 4.6 kPa [3.3-6.6]. ATI yielded valid measurements in 77 patients. The median ATI coefficient was 0.65 [0.5-0.81] dB/cm/MHz. No impact of age, sex, weight and Body Mass Index was observed.

CONCLUSION

SWE and ATI liver values were provided in healthy children. The normative quantitative data might be useful to characterize liver parenchyma in children better.

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

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

Presence of donor specific HLA class 2 antibodies (DSA class 2) is associated with development of graft fibrosis more than 10 years after liver transplantation-a retrospective single center study

Here the impact of donor specific human leukocyte antigen (HLA) class 2 antibodies (DSA cl 2) on long term outcome after liver transplantation (LT) was investigated. Altogether 156 (44 pediatric and 112 adult) LT recipients were included in the study. Graft fibrosis was assessed by liver elastography and biopsy. DSA cl 2 were determined by Luminex technology. 46% of LT recipients were positive for DSA cl 2 after a median follow-up of 15 years. In the multivariate analysis DSA cl 2 were significantly associated with immunosuppressive monotherapy (OR 5.42; 95% CI: 1.02-28.90; p = .048). Compared to DSA cl 2 negative patients, positive recipients had significantly more graft fibrosis based on the liver stiffness (mean 9.4 ± 9.0 kPa vs. 6.5 ± 6.3 kPa; p < .002) and fibrosis stages determined by liver elastography (p = .016) and the performed liver biopsies (p = .002). Also, a significantly higher incidence of chronic rejections (11% vs. 2%; p = .045) and graft losses (6% vs. 0%; p = .043) were found. In the multivariate regression analysis DSA cl 2 were significantly associated with graft fibrosis (OR 4.57; 95% CI 1.59-13.10; p = .005). So, these data suggest that development of DSA cl 2 occurs more often with immunosuppressive monotherapy and may ultimately result in chronic rejection and graft fibrosis.

Elastography for Pediatric Chronic Liver Disease: A Review and Expert Opinion

In adults with chronic liver diseases, ultrasound and magnetic resonance shear wave elastography (SWE) can replace liver biopsy in several clinical scenarios. Several guidelines on the use of ultrasound SWE for the adult population have been published. However, the number of publications in the pediatric population is limited, and available guidelines on SWE do not specifically address pediatric chronic liver diseases. In this article, we review the literature on the use of SWE for pediatric chronic liver diseases and provide expert opinion on how to use SWE, both ultrasound and magnetic resonance techniques, in the pediatric population.

Feasibility and Reliability of Two-Dimensional Shear-Wave Elastography of the Liver of Clinically Healthy Cats

Given the broad overlap of normal and abnormal liver tissue in the subjective evaluation of the liver in conventional B-mode ultrasonography, there is a need for a non-invasive and quantitative method for the diagnosis of liver disease. Novel two-dimensional shear-wave elastography (2-D SWE) can measure tissue stiffness by propagation of the shear wave induced using acoustic radiation force impulse in real time. To the best of our knowledge, two-dimensional shear-wave measurement of the liver in cats has not been reported to date. This study assessed the feasibility, reliability, normal values, and related influencing factors of 2-D SWE for assessment of the feline liver without anesthesia and breath-holding. Two-dimensional shear-wave ultrasonography was performed by two evaluators at the right and left sides of the liver. Twenty-nine client-owned clinically healthy adult cats were included. The means and standard deviations for the shear-wave speed and stiffness in the right liver were 1.52 ± 0.13 m/s and 6.94 ± 1.26 kPa, respectively, and those for the left liver were 1.61 ± 0.15 m/s and 7.90 ± 1.47 kPa, respectively. Shear-wave speed (P = 0.005) and stiffness (P = 0.002) were significantly lower in the right liver when compared to the left. The intraclass correlation value for liver stiffness was 0.835 and 0.901 for the right and left liver, respectively, indicating high interobserver agreement. Age, weight, body condition score (BCS), gabapentin administration, and measurement depths were not significantly correlated with liver stiffness or elastography measurements (P > 0.05). Our findings suggest that 2-D SWE measurements of the liver are not influenced significantly by age, weight, or BCS and can be reliably performed without anesthesia and breath-holding in cats. The values determined here can help form the basis for reference elastography values for evaluation of the feline liver.

Point Shear Wave Elastography and the Effect of Physical Exercise, Alcohol Consumption, and Respiration in Healthy Adults

Purpose Ultrasound elastography is a noninvasive method for liver stiffness measurement (LSM) with the aim of reflecting approximate liver fibrosis load. Despite minimal evidence, current guidelines recommend 10 min of rest and breath hold prior to measurements and offer no advice concerning recent alcohol consumption, leading to challenges in clinical practice. We aimed to investigate how LSM in healthy adults is influenced by physical exercise, recent alcohol consumption, and respiration.

Materials and Methods 42 healthy subjects aged 21–36 years were included. LSM using point shear wave elastography (pSWE) was performed in five stages: baseline, after physical activity, after registration of alcohol consumption, and during breath hold compared to free breathing.

Results LSM values were significantly increased following physical exercise compared to baseline values (4.1±0.8 vs. 3.8±0.8 kPa, p=0.01). Alcohol consumption during the last 72 h (0–27 alcohol units) did not significantly affect LSM. There was no significant difference between LSM during breath hold and free breathing.

Conclusion In healthy subjects, LSM increased after recent physical exercise, while alcohol consumption 24–72 h prior to examination did not have a significant impact. There was no clinically significant effect of breath hold on LSM. Our study supports present guidelines recommending rest prior to LSM, while indicating that breath hold may not be mandatory. Recent moderate alcohol exposure may affect LSM to a lesser extent than commonly believed.

Comparison of 2-Dimensional Shear Wave Elastographic Measurements Using ElastQ Imaging and SuperSonic Shear Imaging: Phantom Study and Clinical Pilot Study

OBJECTIVES

To compare the feasibility and clinical applicability of ElastQ imaging (Philips Healthcare, Best, the Netherlands) with that of SuperSonic shear imaging (SSI; SuperSonic Imagine, Aix-en-Provence, France) using an elastographic phantom and a pilot study of patients.

METHODS

Two-dimensional shear wave elastography measurement was performed by ElastQ imaging and SSI by 2 radiologists. An elastographic phantom with 5 target elasticities at 2 acquisition depths was used. The coefficients of variation and intraclass correlation coefficients (ICCs) were evaluated for repeatability and interobserver agreement, respectively. The mean elasticities of the systems at each target were compared. The proportions of measurements that were out of the range of expected values and measurement errors were calculated to determine accuracy. Liver stiffness (LS) was measured by both systems in 27 children and young adult patients with various liver diseases.

RESULTS

Both systems provided high repeatability in elasticity measurements of phantom targets (coefficients of variation, 0.69%-15.82%), and there was excellent interobserver agreement (ICC, 0.992). Most (90%) mean elasticities of targets were significantly different between the techniques (P ≤ .002) and acquisition depths (P ≤ .004). ElastQ imaging had significantly lower proportions of out-of-range measurements and measurement errors (P ≤ .003) than SSI. In patients with liver disease, LS measurements of the systems were strongly correlated (ρ = 0.955; P < .001) and had excellent agreement (ICC, 0.951; P < .001).

CONCLUSIONS

ElastQ imaging had comparably good results in terms of repeatability, interobserver agreement, and accuracy in the phantom model compared with SSI. The pilot patient study showed strong correlations in LS values between the systems.

Spleen stiffness by 2-D shear wave elastography is the most accurate predictor of high-risk esophagogastric varices in children with biliary atresia

AIM

Esophagogastric variceal hemorrhage is a cause of poor prognosis in patients with biliary atresia (BA). To prevent variceal hemorrhage, simple and reliable screening methods for high-risk esophagogastric varices (HR-EGV) are needed. We evaluated the efficacy of liver stiffness (LS) and spleen stiffness (SS) as measured by 2-D shear wave elastography (2D-SWE), which was reported to be more accurate than transient elastography, for detecting HR-EGV in children with BA.

METHODS

Thirty-four children with BA were enrolled. Both LS and SS were measured by 2D-SWE. The presence of large esophageal varices or esophageal varices of any size with red wale marking and/or the presence of gastric varices along the cardia were defined as HR-EGV. Clinical data were collected and previously reported prediction indices for varices were calculated.

RESULTS

Liver stiffness and SS were obtained from all patients. Fourteen patients showed HR-EGV. Significantly different variables between patients with and without HR-EGV were as follows: spleen diameter (116 mm vs. 95 mm), clinical prediction rule (104.7 vs. 124.7), King's variceal prediction score (78.8 vs. 99.4), aspartic aminotransferase-to-platelet ratio index (2.03 vs. 0.98), LS (2.63 m/s vs. 1.87 m/s), and SS (4.44 m/s vs. 3.69 m/s). The highest area under the receiver operating characteristic curve for detecting HR-EGV was that for SS (0.900), and the cut-off SS of 4.12 m/s yielded 92.9% sensitivity and 90% specificity. The intraclass correlation coefficient for intra-observer reproducibility was 0.828.

CONCLUSIONS

Spleen stiffness from 2D-SWE offered the most accurate predictor of HR-EGV in BA children.

Diagnostic Performance of 2-D Shear Wave Elastography for Differentiation of Hepatoblastoma and Hepatic Hemangioma in Children under 3 Years of Age

The aim of the present study was to prospectively evaluate the clinical efficiency of 2-D shear wave elastography (2-D-SWE) for differentiating hepatoblastoma and hepatic hemangioma in children under 3 y of age. 2-D-SWE was performed in 109 consecutive patients with confirmed hepatic neoplasms by pathologic analysis or contrast-enhanced computed tomography plus follow-up observation, in which 71 patients were defined as the test group, and the remaining 38 patients were defined as the validation group. An elasticity value was obtained from each lesion. The diagnostic performance and optimal cut-off value were determined by receiver operating characteristic (ROC) analysis in the test group, and the accuracy of this threshold was analyzed in the validation group. The interclass correlation coefficient (ICC) and Spearman rank correlation tests were applied to assess the reproducibility of elastic measurement and the relationship between the elasticity value and potential influencing parameters. The mean elasticity values were 58.4 ± 19.5 kPa for hepatoblastoma and 19.0 ± 16.0 kPa for hemangioma (Z = -7.685, p = 0.000). The cut-off value in the test group was 39.5 kPa with an area under the ROC curve for differentiation of 0.915, sensitivity of 88.1% and specificity of 86.2%. The accuracy of this threshold in the validation group was 86.8%. The ICCs for inter- and intra-observer reproducibility for acquisition of the elastic measurement were 0.946 and 0.971, respectively. No significant correlation was found between the elasticity value and age for either hemangioma (r = 0.205, p = 0.167) or hepatoblastoma (r = 0.047, p = 0.715). The elasticity value was positively correlated with lesion size (r = 0.332, p = 0.023) in patients with hemangioma but not in patients with hepatoblastoma (r = 0.222, p = 0.082). As a complementary method, 2-D-SWE may aid the differentiation of hepatoblastoma and hemangioma.

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.