Use of magnetic resonance elastography to assess hepatic fibrosis in children with chronic liver disease

MR and Ultrasound Elastography for Fibrosis Assessment in Children: Practical Implementation and Supporting Evidence-AJR Expert Panel Narrative Review

Quantitative MRI and ultrasound biomarkers of liver fibrosis have become important tools in the diagnosis and clinical management of children with chronic liver disease (CLD). In particular, MR elastography is now routinely performed in clinical practice to evaluate the liver for fibrosis. Ultrasound shear-wave elastography has also become widely performed for this purpose, especially in young children. These noninvasive methods are increasingly used to replace liver biopsy for the diagnosis, quantitative staging, and treatment monitoring of patients with CLD. Although ultrasound has the advantages of portability and lower equipment cost than MRI, available evidence indicates that MRI may have greater reliability and accuracy in liver fibrosis evaluation. In this AJR Expert Panel Narrative Review, we describe how, why, and when to use MRI- and ultrasound-based elastography methods for liver fibrosis assessment in children. Practical approaches are discussed for adapting and optimizing these methods in children, with consideration of clinical indications, patient preparation, equipment requirements, and acquisition technique, as well as pitfalls and confounding factors. Guidance is provided for interpretation and reporting, and representative case examples are presented.

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.

Self-Gated Radial Free-Breathing Liver MR Elastography: Assessment of Technical Performance in Children at 3 T

BACKGROUND

Conventional liver magnetic resonance elastography (MRE) requires breath-holding (BH) to avoid motion artifacts, which is challenging for children. While radial free-breathing (FB)-MRE is an alternative for quantifying liver stiffness (LS), previous methods had limitations of long scan times, acquiring two slices in 5 minutes, and not resolving motion during reconstruction.

PURPOSE

To reduce FB-MRE scan time to 4 minutes for four slices and to investigate the impact of self-gated (SG) motion compensation on FB-MRE LS quantification in terms of agreement, intrasession repeatability, and technical quality compared to conventional BH-MRE.

STUDY TYPE

Prospective.

POPULATION

Twenty-six children without fibrosis (median age: 12.9 years, 15 females).

FIELD STRENGTH/SEQUENCE

3 T; Cartesian gradient-echo (GRE) BH-MRE, research application radial GRE FB-MRE.

ASSESSMENT

Participants were scanned twice to measure repeatability, without moving the table or changing the participants' position. LS was measured in areas of the liver with numerical confidence ≥90%. Technical quality was examined using measurable liver area (%).

STATISTICAL TESTS

Agreement of LS between BH-MRE and FB-MRE was evaluated using Bland-Altman analysis for SG acceptance rates of 40%, 60%, 80%, and 100%. LS repeatability was assessed using within-subject coefficient of variation (wCV). The differences in LS and measurable liver area were examined using Kruskal-Wallis and Wilcoxon signed-rank tests. P < 0.05 was considered significant.

RESULTS

FB-MRE with 60% SG achieved the closest agreement with BH-MRE (mean difference 0.00 kPa). The LS ranged from 1.70 to 1.83 kPa with no significant differences between BH-MRE and FB-MRE with varying SG rates (P = 0.52). All tested methods produced repeatable LS with wCV from 4.4% to 6.5%. The median measurable liver area was smaller for FB-MRE (32%-45%) than that for BH-MRE (91%-93%) (P < 0.05).

DATA CONCLUSION

FB-MRE with 60% SG can quantify LS with close agreement and comparable repeatability with respect to BH-MRE in children.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 1.

The combined pioglitazone and topiramate therapy for management of pediatric patients with severe MASLD

BACKGROUND

Metabolic dysfunction associated steatotic liver disease (MASLD) is the most common cause of chronic hepatitis in adult and pediatric patients. Adolescents with severe MASLD can demonstrate a more aggressive disease phenotype as they more commonly develop liver fibrosis than BMI matched adults. Therefore, MASLD is the fastest growing indication for liver transplants in young adults.

METHODS

Pioglitazone has been shown to improve liver histology in adult patients with MASLD, and in some studies, it attenuated liver fibrosis. Despite its perceived efficacy, pioglitazone is not widely used, likely due to its side effect profile, specifically increased weight gain. Topiramate lowers body weight in adolescents and in combination with phentermine, is one of the few FDA-approved medications for the management of obesity in children over 12 years of age. We performed a retrospective review of the outcomes in pediatric patients with severe MASLD, treated with the combined pioglitazone and topiramate therapy.

RESULTS

Here, we report a case series of seven adolescents with severe MASLD and ≥F2 liver fibrosis treated with the combined pioglitazone and topiramate therapy. The combined therapy improved mean serum ALT from 165 ± 80 U/L to 89 ± 62 U/L after 12 months mean duration of treatment. One patient who completed 24 months of the combined therapy demonstrated a decrease in liver stiffness from 8.9 kPa to 5.6 kPa, as assessed by FibroScan elastography. There was a significant increase in body weight during this time, however, body mass index as a percentage of the 95 th percentile adjusted for age and gender did not increase significantly, 151 ± 29% vs. 152 ± 28%. Moreover, waist circumference, mid-upper arm circumference, percent body fat, and muscle mass were not significantly different before and after treatment. Serum lipid levels and hemoglobin A1c also did not change with the treatment.

CONCLUSION

In summary, this case series provides encouraging results about the efficacy of the combined pioglitazone and topiramate therapy for the management of adolescents with severe MASLD, which should be further explored in clinical studies.

Point Shear Wave Elastography Detected Liver Stiffness Increased in Pediatric Patient With Thalassemia Major

ABSTRACT

Transient elastography (TE) and point shear wave elastography (pSWE) are 2 elastographic ultrasound examinations used in liver stiffness (LS) measurement. It was shown that the LS value detected by TE in pediatric β-thalassemia major patients has increased, and there was no LS evaluation obtained with pSWE in literature. Thus, in this study, it was aimed to evaluate LS with pSWE examination in children with thalassemia major and to determine LS-related parameters in these patients. Sixty-three schoolchildren with a diagnosis of β-thalassemia major and 21 healthy controls between the ages of 7 and 18 years were included. In addition to routine anamnesis, physical examination, and laboratory examinations, renal and liver ultrasounds were performed. Liver stiffness values were measured by pSWE examination. Serum levels of urea, aspartate-aminotransferase, alanine-aminotransferase, iron, and ferritin were significantly higher in patients, and serum creatinine, iron binding capacity, and hemoglobin levels were found to be significantly lower (P < 0.05 for each). Liver stiffness values were significantly higher in patients compared with healthy controls. In linear regression analysis, serum iron and iron binding capacity values were found to be closely related with LS (P < 0.001 vs. β = 0.482 and P = 0.047 vs. β = 0.237, respectively). Liver stiffness values obtained by pSWE examination increase significantly in patients. According to the results of our study, in addition to the previously known TE method, we think that the LS evaluation obtained by pSWE, a new method that can make more accurate measurements, can be used in the possible early detection of target organ damage in children with thalassemia major.

Comparison of spin-echo echo planar imaging and gradient-recalled echo sequences in magnetic resonance elastography of liver at 1.5T same MRI scanner

PURPOSE

Magnetic resonance elastography (MRE) is used to measure liver stiffness with gradient-recalled echo (GRE)-based and spin-echo echo planar imaging (SE-EPI)-based sequences. We compared the liver stiffness (LS) values of the two sequences on a 1.5-T MR imaging scanner.

METHODS

This is a retrospective study. An MRE imaging section was obtained from a horizontal section of the liver. Region of interest was drawn on the elastogram, and the mean LS and pixel values were measured and compared. The correlations between proton density fat fraction, R2* values, and biochemical data from electronic medical records were confirmed, and multivariate analysis was performed.

RESULTS

The mean LS values were 3.01 ± 1.78 kPa for GRE and 3.13 ± 1.57 kPa for SE-EPI, showing excellent agreement and a strong correlation between the two sequences (correlation coefficient r = 0.96). The mean pixel values were 369.5 ± 142.7 pixels for GRE and 490.1 ± 197.9 pixels for SE-EPI, showing a significant difference by the Wilcoxon rank sum test (p < 0.01). There were no LS unmeasurable cases in SE-EPI, but seven (2.5%) were unmeasurable in GRE, and multivariate analysis showed a significant difference with p < 0.001 in R2* values (mean, 92.7 Hz) for the GRE method.

CONCLUSION

The GRE and SE-EPI methods were comparable for LS measurements in 1.5-T liver MRE, indicating that SE-EPI MRE is more useful because GRE MRE may not measure cases with high R2* values and the region of interest tends to be smaller.

Review of paediatric obesity and non-alcoholic fatty liver disease-A focus on emerging non-pharmacologic treatment strategies

Obesity in paediatrics has become one of the most serious public health concerns worldwide. Paediatric obesity leads to increased adult obesity and is associated with several comorbidities, both physical and psychological. Within gastroenterology, non-alcoholic fatty liver disease (NAFLD) is now the most common cause of paediatric liver disease and the most common cause of liver transplantation in young adults. Treatment for NAFLD largely focuses on treatment of obesity with weight loss strategies. Unfortunately, the traditional method of weight loss using multicomponent lifestyle modification (dietary changes, increased exercise and behavioural modification) has often led to disappointing results. In adult patients with obesity, treatment strategies have evolved to include bariatric surgery and, more recently, bariatric endoscopy. In paediatrics, the obesity and NAFLD epidemics will likely require this variety of treatment to address children in a personalized manner. Here, we present a review of paediatric obesity, paediatric NAFLD and the various treatment strategies to date. We focus on non-pharmacologic and emerging therapies, including bariatric surgery and bariatric endoscopy-based treatments. With such a large population of children and adolescents with obesity, further development of these treatments, including paediatric-focused clinical trials, is essential for these emerging modalities.

Diagnostic accuracy and clinical impact of MRI-based technologies for patients with non-alcoholic fatty liver disease: systematic review and economic evaluation

Background

Magnetic resonance imaging-based technologies are non-invasive diagnostic tests that can be used to assess non-alcoholic fatty liver disease.

Objectives

The study objectives were to assess the diagnostic test accuracy, clinical impact and cost-effectiveness of two magnetic resonance imaging-based technologies (LiverMultiScan and magnetic resonance elastography) for patients with non-alcoholic fatty liver disease for whom advanced fibrosis or cirrhosis had not been diagnosed and who had indeterminate results from fibrosis testing, or for whom transient elastography or acoustic radiation force impulse was unsuitable, or who had discordant results from fibrosis testing.

Data sources

The data sources searched were MEDLINE, MEDLINE Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Embase, Cochrane Database of Systematic Reviews, Cochrane Central Database of Controlled Trials, Database of Abstracts of Reviews of Effects and the Health Technology Assessment.

Methods

A systematic review was conducted using established methods. Diagnostic test accuracy estimates were calculated using bivariate models and a summary receiver operating characteristic curve was calculated using a hierarchical model. A simple decision-tree model was developed to generate cost-effectiveness results.

Results

The diagnostic test accuracy review (13 studies) and the clinical impact review (11 studies) only included one study that provided evidence for patients who had indeterminate or discordant results from fibrosis testing. No studies of patients for whom transient elastography or acoustic radiation force impulse were unsuitable were identified. Depending on fibrosis level, relevant published LiverMultiScan diagnostic test accuracy results ranged from 50% to 88% (sensitivity) and from 42% to 75% (specificity). No magnetic resonance elastography diagnostic test accuracy data were available for the specific population of interest. Results from the clinical impact review suggested that acceptability of LiverMultiScan was generally positive. To explore how the decision to proceed to biopsy is influenced by magnetic resonance imaging-based technologies, the External Assessment Group presented cost-effectiveness analyses for LiverMultiScan plus biopsy versus biopsy only. Base-case incremental cost-effectiveness ratio per quality-adjusted life year gained results for seven of the eight diagnostic test strategies considered showed that LiverMultiScan plus biopsy was dominated by biopsy only; for the remaining strategy (Brunt grade ≥2), the incremental cost-effectiveness ratio per quality-adjusted life year gained was £1,266,511. Results from threshold and scenario analyses demonstrated that External Assessment Group base-case results were robust to plausible variations in the magnitude of key parameters.

Limitations

Diagnostic test accuracy, clinical impact and cost-effectiveness data for magnetic resonance imaging-based technologies for the population that is the focus of this assessment were limited.

Conclusions

Magnetic resonance imaging-based technologies may be useful to identify patients who may benefit from additional testing in the form of liver biopsy and those for whom this additional testing may not be necessary. However, there is a paucity of diagnostic test accuracy and clinical impact data for patients who have indeterminate results from fibrosis testing, for whom transient elastography or acoustic radiation force impulse are unsuitable or who had discordant results from fibrosis testing. Given the External Assessment Group cost-effectiveness analyses assumptions, the use of LiverMultiScan and magnetic resonance elastography for assessing non-alcoholic fatty liver disease for patients with inconclusive results from previous fibrosis testing is unlikely to be a cost-effective use of National Health Service resources compared with liver biopsy only.

Study registration

This study is registered as PROSPERO CRD42021286891.

Funding

Funding for this study was provided by the Evidence Synthesis Programme of the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 27, No. 10. See the NIHR Journals Library website for further project information.

Noninvasive biomarkers in pediatric nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease worldwide among children and adolescents. It encompasses a spectrum of disease, from its mildest form of isolated steatosis, to nonalcoholic steatohepatitis (NASH) to liver fibrosis and cirrhosis, or end-stage liver disease. The early diagnosis of pediatric NAFLD is crucial in preventing disease progression and in improving outcomes. Currently, liver biopsy is the gold standard for diagnosing NAFLD. However, given its invasive nature, there has been significant interest in developing noninvasive methods that can be used as accurate alternatives. Here, we review noninvasive biomarkers in pediatric NAFLD, focusing primarily on the diagnostic accuracy of various biomarkers as measured by their area under the receiver operating characteristic, sensitivity, and specificity. We examine two major approaches to noninvasive biomarkers in children with NAFLD. First, the biological approach that quantifies serological biomarkers. This includes the study of individual circulating molecules as biomarkers as well as the use of composite algorithms derived from combinations of biomarkers. The second is a more physical approach that examines data measured through imaging techniques as noninvasive biomarkers for pediatric NAFLD. Each of these approaches was applied to children with NAFLD, NASH, and NAFLD with fibrosis. Finally, we suggest possible areas for future research based on current gaps in knowledge.

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.

Liver fibrosis in children: a comprehensive review of mechanisms, diagnosis, and therapy

Chronic liver disease incidence is increasing among children worldwide due to a multitude of epidemiological changes. Most of these chronic insults to the pediatric liver progress to fibrosis and cirrhosis to different degrees. Liver and immune physiology differs significantly in children from adults. Because most of pediatric liver diseases have no definitive therapy, a better understanding of population and disease-specific fibrogenesis is mandatory. Furthermore, fibrosis development has prognostic significance and often guide treatment. Evaluation of liver fibrosis continues to rely on the gold-standard liver biopsy. However, many high-quality studies put forward the high diagnostic accuracy of numerous diagnostic modalities in this setting. Herein, we summarize and discuss the recent literature on fibrogenesis with an emphasis on pediatric physiology along with a detailed outline of disease-specific signatures, noninvasive diagnostic modalities, and the potential for antifibrotic therapies.

Metabolic-Associated Fatty Liver Disease in Childhood and Adolescence

Metabolic-associated fatty liver disease (MAFLD) has become the most common cause for chronic liver disease among children and adolescents globally. Although liver biopsy remains the gold standard for diagnosis, emerging technology, like velocity controlled transient elastography, a noninvasive method, is being utilized to evaluate degree of fibrosis in these patients. The discovery of multiple gene polymorphisms has brought new hope for possible treatment targets. However, this research is still ongoing, making lifestyle changes and weight reduction the current mainstay of treatment. This review briefly reviews the most recent data regarding the epidemiology, pathophysiology, diagnostic modalities, and treatment of pediatric MAFLD.

Magnetic resonance elastography in evaluation of liver fibrosis in children with chronic liver disease

BACKGROUND

Magnetic resonance elastography (MRE) has been used to stage liver fibrosis in adults. We aimed to assess the agreement between the Ishak scoring system and magnetic resonance elastography-measured liver stiffness (MRE-LS) in children. This study included all the children who underwent abdominal MRE and liver biopsies between February 2018 and January 2021. The correlation between MRE-LS and Ishak fibrosis stage, MRE parameters, and clinical and biochemical markers affecting this relationship was investigated.

RESULTS

A total of 52 patients (31 male; a median age of 11.8 years) were included in the study. The MRE-LS values were significantly different between Ishak fibrosis stages (p = 0.036). With a cut-off value of 2.97 kilopascals, MRE-LS had sensitivity, specificity, PPV, NPV and accuracy values of 90.9%, 82.9%, 58.8%, 97.1%, and 84.6%, respectively, for differentiating mild/moderate fibrosis (F0, 1, 2, 3) from severe fibrosis (F ≥ 4). Although MRE-LS was moderately correlated with Ishak fibrosis score and histological activity index and weakly correlated with aspartate aminotransferase, hepatic steatosis, and R2*, only Ishak fibrosis score was a significant predictor of MRE-LS. MRE-measured spleen stiffness was weakly correlated with the Ishak fibrosis score.

CONCLUSIONS

MRE has high sensitivity and specificity for evaluating liver fibrosis in children. MRE may be used to evaluate liver fibrosis in pediatric patients.

Noninvasive Prediction of Advanced Fibrosis in Pediatric Liver Disease-Discriminatory Performance of 2D Shear Wave Elastography, Transient Elastography and Magnetic Resonance Elastography in Comparison to Histopathology

Background: Elastography can be measured with different imaging techniques and is increasingly used for noninvasive assessment of hepatic fibrosis. Little is known about the performance, and interrelation of different elastographic techniques, in prediction of hepatic fibrosis in pediatric liver disease. Objectives: We aimed to determine the discriminatory value for advanced fibrosis (Metavir F3-4) and evaluate the applicability of 2D shear wave ultrasound elastography (USe), Transient Elastography (TE) and Magnetic Resonance elastography (MRe) in pediatric liver disease. Methods: In patients with pediatric liver disease aged 0−19 years, USe, TE and MRe were compared with histopathological fibrosis stage. Multivariate logistic regression models for advanced fibrosis were considered. Discriminative performance was assessed by the area under the receiver operating characteristic curve and the Brier Score. Primary analyses included complete cases. Multiple imputation was used as sensitivity analysis. Results: In 93 histologically evaluated patients USe, TE and MRe were performed 89, 93 and 61 times respectively. With increased liver stiffness values, significantly increased odds for presenting F3-4 were seen in individual models for ALT < 470 U/L, whereas the effect for ALT > 470 U/L was non-significant. Area under the curve and Brier Score for discrimination of advanced fibrosis were 0.798 (0.661−0.935) and 0.115 (0.064−0.166); 0.862 (0.758−0.966) and 0.118 (0.065−0.171); 0.896 (0.798−0.994) and 0.098 (0.049−0.148) for USe, TE and MRe respectively. No significant increase in discriminatory ability was found when combining elastographic modalities. Conclusions: In pediatric liver disease, USe, TE and MRe had a good discriminatory ability for assessment of advanced liver fibrosis, although TE and MRe performed best. In most children with pediatric liver disease, TE is a reliable and easily applicable measure.

Liver and spleen volume and stiffness in patients post-Fontan procedure and patients with ARPKD compared to normal controls

PURPOSE

Both congestive (patients post-Fontan hepatopathy) and congenital (patients with ARPKD) disease can lead to hepatic fibrosis and portal hypertension with eventual development of splenomegaly. We investigated liver and spleen stiffness as measured by MRE between post-Fontan, ARPKD patients and controls independent of organ volume.

METHODS

Our study included 122 subjects (70 Fontan patients, 14 ARPKD patients, and 38 controls). The mean MRE liver and spleen stiffness values of Fontan patients and patients with ARPKD were compared to controls. Similarly, the liver and spleen volumes of the Fontan patients and patients with ARPKD were then compared to the volumes of controls.

RESULTS

Post-Fontan and ARPKD patients, mean liver stiffness, mean liver volume as well as mean spleen stiffness and mean spleen volume were higher than mean liver stiffness, mean liver volume, mean spleen stiffness, and mean spleen volume of controls. While liver stiffness correlated to liver volume in controls, we found no correlation between stiffness and volume in either Fontan or ARPKD patients, which indicates MRE's ability to act as an independent biomarker. However, these findings are not true in the spleen, where there is significant association between volume and stiffness in patients with ARPKD, but not in Fontan patients or controls.

CONCLUSION

Liver and spleen stiffness and volumes are significantly different among Fontan patients, ARPKD patients, and controls. Our findings suggest that beyond diagnosing fibrosis, MRE cut-off values could be disease-specific since not only the severity but the underlying pathology causing organ congestion or fibrosis influences MRE results.

Paediatric non-alcoholic fatty liver disease: an approach to pathological evaluation

Non-alcoholic fatty liver disease (NAFLD) is becoming an increasingly important healthcare issue along with the rising rates of obesity worldwide. It is the most common chronic liver disease in the paediatric population and the fastest growing indication for liver transplant in young adults. The pathogenesis is complex with contributions from multiple factors and genetic predisposition. While non-invasive laboratory tests and imaging modalities are being increasingly used, the liver biopsy continues to play a crucial role in the diagnosis and prognosis of NAFLD. Histologically, the assessment of paediatric fatty liver disease requires special considerations with respect to a periportal predominant pattern seen in prepubertal patients, as well as a different set of disease processes in the differential diagnosis. In this review, we provide a summary of current knowledge on the epidemiology, pathogenesis and clinical course of paediatric NAFLD as well as the clinical guidelines on diagnosis and management. We discuss the indications and limitations of liver biopsy, histological patterns seen in paediatric NAFLD, other entities to be considered in the differential diagnosis, and conclude with appropriate triaging of liver biopsies and essential elements of pathology reporting.

Non-Invasive Approaches to Estimate Liver Steatosis and Stiffness in Children With Non-Alcoholic Fatty Liver Disease

OBJECTIVES

To develop pediatric-specific models that predict liver stiffness and hepatic steatosis in non-alcoholic fatty liver disease (NAFLD), based on clinical and laboratory data.

METHODS

Children with NAFLD, who had undergone magnetic resonance imaging with proton density fat fraction (MRI-PDFF) for steatosis quantification and/or magnetic resonance elastography (MRE) for liver stiffness assessment were included. We used data from patients imaged between April 2009 to July 2018 to develop a predictive model for fat fraction and stiffness. We validated the performance of the models using data from a second cohort, imaged between 2018 and 2019.

RESULTS

The first cohort (n = 344) consisted of predominantly non-Hispanic (80%), male (67%) adolescents. MRE data were available for 343 children, while PDFF data were available for 130. In multivariable regression, ethnicity, insulin levels, platelet count, and aspartate aminotransferase independently predicted liver stiffness and these variables were used to develop the predictive model. Similarly, sex, ethnicity, alanine aminotransferase, and triglycerides levels independently predicted liver PDFF and were used in the PDFF model. The AUC of the optimal cutoff for the model that predicted a stiffness of >2.71 kPa was 0.70 and for the model that predicted PDFF >5% was 0.78. The validation group (n = 110) had similar characteristics. The correlation coefficient of the model with the measured liver stiffness was 0.30 and with the measured liver PDFF was 0.26.

CONCLUSIONS

Pediatric-specific models perform poorly at predicting exact liver stiffness and steatosis; however, in the absence of magnetic resonance imaging can be used to predict the presence of significant steatosis (>5%) and/or significant stiffness (>2.71). Thus, imaging remains an invaluable adjunct to laboratory investigations in determining disease severity.

Associations between MRI T1 mapping, liver stiffness, quantitative MRCP, and laboratory biomarkers in children and young adults with autoimmune liver disease

Purpose

Define relationships between quantitative magnetic resonance imaging (MRI) metrics and clinical/laboratory data in a pediatric and young adult cohort with autoimmune liver disease (AILD).

Materials and methods

This prospective, cross-sectional study was institutional review board-approved. Patients enrolled in an institutional AILD registry were divided into groups: (1) autoimmune hepatitis (AIH) or (2) primary sclerosing cholangitis (PSC)/autoimmune sclerosing cholangitis (ASC). Participants underwent serum liver biochemistry testing and research MRI examinations, including 3D magnetic resonance cholangiopancreatography (MRCP), magnetic resonance elastography (MRE), and iron-corrected T1 mapping (cT1). MRCP + and LiverMultiScan (Perspectum Ltd., Oxford, UK) were used to post-process 3D MRCP and cT1 data. Multiple linear regression models were used to assess relationships.

Results

58 patients, 35 male, median age 16 years were included; 30 in the AIH group, 28 in the PSC/ASC group. After statistical adjustments for patient age, sex, presence of inflammatory bowel disease (IBD), specific diagnosis (PSC/ASC vs. AIH), and time from diagnosis to MRI examination, left hepatic bile duct maximum diameter was a statistically significant predictor of whole liver mean cT1, cT1 interquartile range (IQR), and MRE liver stiffness (p = 0.01–0.04). Seven laboratory values were significant predictors of whole liver cT1 IQR (p < 0.0001–0.04). Eight laboratory values and right hepatic bile duct median and maximum diameter were significant predictors of liver stiffness (p < 0.0001–0.03).

Conclusions

Bile duct diameters and multiple laboratory biomarkers of liver disease are independent predictors of liver stiffness and cT1 IQR in pediatric patients with AILD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00261-021-03378-0.

Free-breathing radial magnetic resonance elastography of the liver in children at 3 T: a pilot study

BACKGROUND

Magnetic resonance (MR) elastography of the liver measures hepatic stiffness, which correlates with the histopathological staging of liver fibrosis. Conventional Cartesian gradient-echo (GRE) MR elastography requires breath-holding, which is challenging for children. Non-Cartesian radial free-breathing MR elastography is a potential solution to this problem.

OBJECTIVE

To investigate radial free-breathing MR elastography for measuring hepatic stiffness in children.

MATERIALS AND METHODS

In this prospective pilot study, 14 healthy children and 9 children with liver disease were scanned at 3 T using 2-D Cartesian GRE breath-hold MR elastography (22 s/slice) and 2-D radial GRE free-breathing MR elastography (163 s/slice). Each sequence was acquired twice. Agreement in the stiffness measurements was evaluated using Lin's concordance correlation coefficient (CCC) and within-subject mean difference. The repeatability was assessed using the within-subject coefficient of variation and intraclass correlation coefficient (ICC).

RESULTS

Fourteen healthy children and seven children with liver disease completed the study. Median (±interquartile range) normalized measurable liver areas were 62.6% (±26.4%) and 44.1% (±39.6%) for scan 1, and 60.3% (±21.8%) and 43.9% (±44.2%) for scan 2, for Cartesian and radial techniques, respectively. Hepatic stiffness from the Cartesian and radial techniques had close agreement with CCC of 0.89 and 0.94, and mean difference of 0.03 kPa and -0.01 kPa, for scans 1 and 2. Cartesian and radial techniques achieved similar repeatability with within-subject coefficient of variation=1.9% and 3.4%, and ICC=0.93 and 0.92, respectively.

CONCLUSION

In this pilot study, radial free-breathing MR elastography was repeatable and in agreement with Cartesian breath-hold MR elastography in children.

Pediatric Nonalcoholic Fatty Liver Disease

Obesity has led fatty liver disease to become the most common chronic liver disease in children worldwide. Pediatric professional organizations have agreed that screening for fatty liver disease in children is the need of the hour. Once identified, prevention is key through appropriate dietary and activity prescriptions. Research continues to identify key pathways and genetic risk factors that predispose certain children to the more severe manifestations of this silent epidemic. We hope these novel observations lead to breakthrough treatments for these children that are severely impacted, such that they may no longer need liver transplantation as young adults.

What is the impact of methotrexate on liver in patients with juvenile idiopathic arthritis? Results of liver SWE performed in a single centre

OBJECTIVES

Long-term therapy with low-dose methotrexate (MTX) is widely used in treatment of rheumatic diseases, in children. The purpose of this study was to evaluate liver elasticity in patients with juvenile idiopathic arthritis (JIA) who received MTX and compare the results with control group.

METHODS

Liver elasticity was evaluated with shear wave elastography (SWE) technique in 25 patients aged 3-17 years who were followed up with JIA and received MTX and compared with 25 healthy controls of the same age and weight. Factors that had an effect on liver elasticity were examined.

RESULTS

The mean SWE value of patients was 2.64 ± 2.13 m/s and 24.10 ± 18.50 kPa, whereas 1.83 ± 0.16 m/s and 10.09 ± 1.83 kPa in control group. There was a significant difference in liver elasticity in the patient and control groups. When the patients were evaluated as Group 1 (< 1000 mg) and Group 2 (≥ 1000 mg) according to the cumulative MTX dose, no significant difference was obtained. There was positive correlation between liver elasticity and weekly MTX dose and age.

CONCLUSIONS

Our study revealed that liver elasticity significantly decreased in patients who received MTX when compared with the control group. The elastography technique will be understood better over time and used safely in many areas.

Assessment of agreement between manual and automated processing of liver MR elastography for shear stiffness estimation in children and young adults with autoimmune liver disease

PURPOSE

To compare automated versus standard of care manual processing of 2D gradient recalled echo (GRE) liver MR Elastography (MRE) in children and young adults.

MATERIALS AND METHODS

2D GRE liver MRE data from research liver MRI examinations performed as part of an autoimmune liver disease registry between March 2017 and March 2020 were analyzed retrospectively. All liver MRE data were acquired at 1.5 T with 60 Hz mechanical vibration frequency. For manual processing, two independent readers (R1, R2) traced regions of interest on scanner generated shear stiffness maps. Automated processing was performed using MREplus+ (Resoundant Inc.) using 90% (A90) and 95% (A95) confidence masks. Agreement was evaluated using intra-class correlation coefficients (ICC) and Bland-Altman analyses. Classification performance was evaluated using receiver operating characteristic curve (ROC) analyses.

RESULTS

In 65 patients with mean age of 15.5 ± 3.8 years (range 8-23 years; 35 males) median liver shear stiffness was 2.99 kPa (mean 3.55 ± 1.69 kPa). Inter-reader agreement for manual processing was very strong (ICC = 0.99, mean bias = 0.01 kPa [95% limits of agreement (LoA): - 0.41 to 0.44 kPa]). Correlation between manual and A95 automated processing was very strong (R1: ICC = 0.988, mean bias = 0.13 kPa [95% LoA: - 0.40 to 0.68 kPa]; R2: ICC = 0.987, mean bias = 0.13 kPa [95% LoA: - 0.44 to 0.69 kPa]). Automated measurements were perfectly replicable (ICC = 1.0; mean bias = 0 kPa).

CONCLUSION

Liver shear stiffness values obtained using automated processing showed excellent agreement with manual processing. Automated processing of liver MRE was perfectly replicable.

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.

Advances in the Epidemiology, Diagnosis, and Management of Pediatric Fatty Liver Disease

PURPOSE

Nonalcoholic fatty liver (NAFL) is a major contributor to pediatric liver disease. This review evaluated the current literature on prevalence, screening, diagnosis, and management of NAFL in children and explored recent advances in the field of pediatric NAFL.

METHODS

A PubMed search was performed for manuscripts describing disease burden, diagnosis, and management strategies in pediatric NAFL published within the past 15 years. Systematic reviews, clinical practice guidelines, randomized controlled trials, and cohort and case-control studies were reviewed for the purpose of this article.

FINDINGS

The prevalence of NAFL in children is increasing. It is a leading cause of liver-related morbidity and mortality in children. Screening and diagnosis of NAFL in children are a challenge. Lifestyle changes and exercise are the cornerstones of the management of NAFL.

IMPLICATIONS

Further research is needed to develop better screening and diagnostic tools for pediatric NAFL, including noninvasive diagnostics. NAFL therapeutics is another area of much-needed, ongoing research.

Magnetic resonance elastography to quantify liver disease severity in autosomal recessive polycystic kidney disease

OBJECTIVES

To evaluate whether liver and spleen magnetic resonance elastography (MRE) can measure the severity of congenital hepatic fibrosis (CHF) and portal hypertension (pHTN) in individuals with autosomal recessive polycystic kidney disease (ARPKD), and to examine correlations between liver MRE and ultrasound (US) elastography.

METHODS

Cross-sectional study of nine individuals with ARPKD and 14 healthy controls. MRE was performed to measure mean liver and spleen stiffness (kPa); US elastography was performed to measure point shear wave speed (SWS) in both liver lobes. We compared: (1) MRE liver and spleen stiffness between controls vs. ARPKD; and (2) MRE liver stiffness between participants with ARPKD without vs. with pHTN, and examined correlations between MRE liver stiffness, spleen length, platelet counts, and US elastography SWS. Receiver operating characteristic (ROC) analysis was performed to examine diagnostic accuracy of liver MRE.

RESULTS

Participants with ARPKD (median age 16.8 [IQR 13.3, 18.9] years) had higher median MRE liver stiffness than controls (median age 14.7 [IQR 9.7, 16.7 years) (2.55 vs. 1.92 kPa, p = 0.008), but MRE spleen stiffness did not differ. ARPKD participants with pHTN had higher median MRE liver stiffness than those without (3.60 kPa vs 2.49 kPa, p = 0.05). Liver MRE and US elastography measurements were strongly correlated. To distinguish ARPKD vs. control groups, liver MRE had 78% sensitivity and 93% specificity at a proposed cut-off of 2.48 kPa [ROC area 0.83 (95% CI 0.63-1.00)].

CONCLUSION

Liver MRE may be a useful quantitative method to measure the severity of CHF and pHTN in individuals with ARPKD.

Relationship Between Histological Features of Non-alcoholic Fatty Liver Disease and Ectopic Fat on Magnetic Resonance Imaging in Children and Adolescents

Objectives: To investigate the association between ectopic fat content in the liver and pancreas, obesity-related metabolic components, and histological findings of non-alcoholic fatty liver disease (NAFLD) in children. Methods: This cross-sectional study investigated 63 children with biopsy-proven NAFLD who underwent magnetic resonance imaging (MRI), anthropometry, laboratory tests, and body composition analysis. Clinical and metabolic parameters, MRI-measured hepatic fat fraction (HFF) and pancreatic fat fraction (PFF), and histological findings were analyzed. Results: In a total of 63 children (48 boys, median age 12.6 years, median body mass index z-score 2.54), HFF was associated with histological steatosis [10.4, 23.7, and 31.1% in each steatosis grade, P < 0.001; Spearman's rho coefficient (rs) = 0.676; P < 0.001] and NAFLD activity score (rs = 0.470, P < 0.001), but not with lobular inflammation, hepatocyte ballooning, and hepatic fibrosis. PFF was not associated with any histological features of the liver. Waist circumference-to-height ratio and body fat percentage were associated with the steatosis grade (P = 0.006 and P = 0.004, respectively). Alanine aminotransferase was not associated with steatosis but was associated with lobular inflammation (P = 0.008). Lobular inflammation was also associated with high total cholesterol and low-density lipoprotein cholesterol and metabolic syndrome (P = 0.015, P = 0.036, and P = 0.038, respectively). Conclusions: Hepatic steatosis on MRI was only associated with the histological steatosis grade, while elevated serum levels of liver enzymes and lipids were related to the severity of lobular inflammation. Therefore, MRI should be interpreted in conjunction with the anthropometric and laboratory findings in pediatric patients.

MR Elastography of the Abdomen: Experimental Protocols

Application of MRE for noninvasive evaluation of renal fibrosis has great potential for noninvasive assessment in patients with chronic kidney disease (CKD). CKD leads to severe complications, which require dialysis or kidney transplant and could even result in death. CKD in native kidneys and interstitial fibrosis in allograft kidneys are the two major kidney fibrotic pathologies where MRE may be clinically useful. Both these conditions can lead to extensive morbidity, mortality, and high health care costs. Currently, biopsy is the standard method for renal fibrosis staging. This method of diagnosis is painful, invasive, limited by sampling bias, exhibits inter- and intraobserver variability, requires prolonged hospitalization, poses risk of complications and significant bleeding, and could even lead to death. MRE based methods can potentially be useful to noninvasively detect, stage, and monitor renal fibrosis, reducing the need for renal biopsy. In this chapter, we describe experimental procedure and step by step instructions to run MRE along with some illustrative applications. We also includes sections on how to perform data quality check and analysis methods.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers.

MR Elastography of the Abdomen: Basic Concepts

Magnetic resonance elastography (MRE) is an emerging imaging modality that maps the elastic properties of tissue such as the shear modulus. It allows for noninvasive assessment of stiffness, which is a surrogate for fibrosis. MRE has been shown to accurately distinguish absent or low stage fibrosis from high stage fibrosis, primarily in the liver. Like other elasticity imaging modalities, it follows the general steps of elastography: (1) apply a known cyclic mechanical vibration to the tissue; (2) measure the internal tissue displacements caused by the mechanical wave using magnetic resonance phase encoding method; and (3) infer the mechanical properties from the measured mechanical response (displacement), by generating a simplified displacement map. The generated map is called an elastogram.While the key interest of MRE has traditionally been in its application to liver, where in humans it is FDA approved and commercially available for clinical use to noninvasively assess degree of fibrosis, this is an area of active research and there are novel upcoming applications in brain, kidney, pancreas, spleen, heart, lungs, and so on. A detailed review of all the efforts is beyond the scope of this chapter, but a few specific examples are provided. Recent application of MRE for noninvasive evaluation of renal fibrosis has great potential for noninvasive assessment in patients with chronic kidney diseases. Development and applications of MRE in preclinical models is necessary primarily to validate the measurement against "gold-standard" invasive methods, to better understand physiology and pathophysiology, and to evaluate novel interventions. Application of MRE acquisitions in preclinical settings involves challenges in terms of available hardware, logistics, and data acquisition. This chapter will introduce the concepts of MRE and provide some illustrative applications.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by another separate chapter describing the experimental protocol and data analysis.

Deep learning networks on chronic liver disease assessment with fine-tuning of shear wave elastography image sequences

Chronic liver disease (CLD) is currently one of the major causes of death worldwide. If not treated, it may lead to cirrhosis, hepatic carcinoma and death. Ultrasound (US) shear wave elastography (SWE) is a relatively new, popular, non-invasive technique among radiologists. Although many studies have been published validating the SWE technique either in a clinical setting, or by applying machine learning on SWE elastograms, minimal work has been done on comparing the performance of popular pre-trained deep learning networks on CLD assessment. Currently available literature reports suggest technical advancements on specific deep learning structures, with specific inputs and usually on a limited CLD fibrosis stage class group, with limited comparison on competitive deep learning schemes fed with different input types. The aim of the present study is to compare some popular deep learning pre-trained networks using temporally stable and full elastograms, with or without augmentation as well as propose suitable deep learning schemes for CLD diagnosis and progress assessment. 200 liver biopsy validated patients with CLD, underwent US SWE examination. Four images from the same liver area were saved to extract elastograms and processed to exclude areas that were temporally unstable. Then, full and temporally stable masked elastograms for each patient were separately fed into GoogLeNet, AlexNet, VGG16, ResNet50 and DenseNet201 with and without augmentation. The networks were tested for differentiation of CLD stages in seven classification schemes over 30 repetitions using liver biopsy as the reference. All networks achieved maximum mean accuracies ranging from 87.2%-97.4% and area under the receiver operating characteristic curves (AUCs) ranging from 0.979-0.990 while the radiologists had AUCs ranging from 0.800-0.870. ResNet50 and DenseNet201 had better average performance than the other networks. The use of the temporal stability mask led to improved performance on about 50% of inputs and network combinations while augmentation led to lower performance for all networks. These findings can provide potential networks with higher accuracy and better setting in the CLD diagnosis and progress assessment. A larger data set would help identify the best network and settings for CLD assessment in clinical practice.

Normal Liver Stiffness Measured with MR Elastography in Children

Background Stiffness thresholds for liver MR elastography in children vary between studies and may differ from thresholds in adults. Normative liver stiffness data are needed to optimize diagnostic thresholds for children. Purpose To determine normal liver stiffness, and associated normal ranges for children, as measured with MR elastography across vendors and field strengths. Materials and Methods This was a prospective multicenter cohort study (ClinicalTrials.gov identifier: NCT03235414). Volunteers aged 7-17.9 years without a known history of liver disease were recruited at four sites for a research MRI and blood draw between February 2018 and October 2019. MRI was performed on three vendor platforms and at two field strengths (1.5 T and 3.0 T). All MRI scans were centrally analyzed; stiffness, proton density fat fraction (PDFF), and R2* values were expressed as means of means. Mean and 95% confidence intervals (CIs) for liver stiffness were calculated. Pearson correlation coefficient (r), two-sample t test, or analysis of variance was used to assess univariable associations. Results Seventy-one volunteers had complete data and no documented exclusion criterion (median age, 12 years; interquartile range [IQR], 10-15 years; 39 female participants). Median body mass index percentile was 54% (IQR, 32.5%-69.5%). Mean liver stiffness was 2.1 kPa (95% CI: 2.0, 2.2 kPa) with mean ± 1.96 kPa standard deviation of 1.5-2.8 kPa. Median liver PDFF was 2.0% (IQR, 1.7%-2.6%). There was no association between liver stiffness and any patient variable or MRI scanner factor. Conclusion Mean liver stiffness measured with MR elastography in children without liver disease was 2.1 kPa (similar to that in adults). The 95th percentile of normal liver stiffness was 2.8 kPa. Liver stiffness was independent of sex, age, or body mass index and did not vary with MRI scanner vendor or field strength. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Yin in this issue.

Fusing acceleration and saturation techniques with wave amplitude labeling of time-shifted zeniths MR elastography

PURPOSE

To design a new 2D gradient recalled echo MR elastography (MRE) pulse sequence with inflow saturation for measuring liver stiffness in half the breath-hold time compared to standard of care (SC) 2D GRE MRE sequences.

METHODS

FASTWALTZ (fusing acceleration and saturation techniques with wave amplitude labeling of time-shifted zeniths) MRE employs an interleaved dual TR strategy with wave amplitude labeling and compressed SENSE undersampling to reduce breath-hold time while incorporating inflow saturation to suppress flow artifacts. The sequence was implemented and compared with SC MRE both in phantoms and in vivo in 5 asymptomatic volunteers. Stiffness values, region of interest size, and breath-hold times were compared between sequences.

RESULTS

Stiffness values were comparable between FASTWALTZ and SC MRE for both phantoms and in-vivo data. In volunteers, the group mean stiffness values at 60 Hz and region of interest size were 1.96 ± 0.30 kilopascals and 2279 ± 516 mm² for SC MRE, and 1.95 ± 0.29 kilopascals and 2061 ± 464 mm² for FASTWALTZ. Breath-hold duration for FASTWALTZ was 6.3 s compared to 13.3 s for SC MRE.

CONCLUSION

FASTWALTZ provides comparable stiffness values in half the breath-hold time compared to SC MRE and may have clinical benefits in patients with limited breath-holding capacity.

Emerging New Diagnostic Modalities and Therapies of Nonalcoholic Fatty Liver Disease

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) has emerged as the leading cause of chronic liver disease in both adults and children. In this article, we review recent developments in the screening, diagnosis, and treatment of pediatric NAFLD.

RECENT FINDINGS

Although alanine aminotransferase (ALT) remains the best screening test for NAFLD in children, and liver biopsy is still required for the diagnosis of nonalcoholic steatohepatitis (NASH), other noninvasive biomarker/imaging studies (MRI-PDFF and VCTE) have emerged as diagnostic methods for pediatric NAFLD. Two large clinical therapeutic trials testing vitamin E, metformin, and cysteamine in pediatric NAFLD yielded mostly inconclusive results. Bariatric surgery has begun to be used in adolescents with severe obesity. An adult phase 2 study using obeticholic acid (OCA) to treat NASH patients with fibrosis showed some positive results. As we continue to await the first FDA-approved therapeutic agent for NASH, lifestyle change remains the main modality of treatment. Newer diagnostic and treatment modalities for pediatric NAFLD continue to be in development under FDA guidance.

Cardiac magnetic resonance derived atrial function in patients with a Fontan circulation

To assess atrial function in Fontan patients using cardiac MRI (CMR) and determine the relationships between atrial function, hemodynamics, and clinical outcomes. Two center chart review identified all Fontan patients with technically adequate CMR to assess atrial function within 1 year of cardiac catheterization and age-matched controls with CMR. Atrial reservoir, conduit, and pump global longitudinal strain and strain rate measurements were determined by CMR. Univariate and stepwise multivariable analysis were conducted to detect associations of atrial function measures with ventricular end diastolic pressure (EDP), cardiac index (CI), exercise capacity, liver stiffness and a composite outcome of heart transplantation, ventricular assist device or death. The study cohort was comprised of 33 Fontan patients and 30 age-matched controls. Fontan patients had lower atrial reservoir and conduit strain, and lower reservoir, conduit, and pump strain rate compared to age-matched controls. Atrial conduit strain was negatively associated with EDP and lower atrial pump-to-conduit strain ratio was associated with lower cardiac index in multivariable analysis. Lower atrial pump strain was associated with lower exercise capacity (per 1% increase: β = 2.3 ± 0.9, p = 0.03) and higher liver stiffness (per 1% increase: β =  - 0.12 ± 0.03, p = 0.002). Higher atrial pump strain (HR per 1% increase = 0.53 [95% confidence interval 0.22, 0.83], p = 0.002) and ventricular ejection fraction (HR per 1% increase = 0.90 [95% confidence interval 0.80, 0.98], p = 0.02) were associated with lower risk for the composite adverse outcome. Atrial function is impaired in Fontan patients and is associated with worse CI, EDP, exercise performance, liver stiffness, and a higher risk for adverse outcomes.

Quantitative Imaging in Pediatric Hepatobiliary Disease

Pediatric hepatobiliary imaging is important for evaluation of not only congenital or structural disease but also metabolic or diffuse parenchymal disease and tumors. A variety of ultrasonography and magnetic resonance imaging (MRI) techniques can be used for these assessments. In ultrasonography, conventional ultrasound imaging as well as vascular imaging, elastography, and contrast-enhanced ultrasonography can be used, while in MRI, fat quantification, T2/T2^* mapping, diffusion-weighted imaging, magnetic resonance elastography, and dynamic contrast-enhanced MRI can be performed. These techniques may be helpful for evaluation of biliary atresia, hepatic fibrosis, nonalcoholic fatty liver disease, sinusoidal obstruction syndrome, and hepatic masses in children. In this review, we discuss each tool in the context of management of hepatobiliary disease in children, and cover various imaging techniques in the context of the relevant physics and their clinical applications for patient care.

Comparison of liver T1 relaxation times without and with iron correction in pediatric autoimmune liver disease

BACKGROUND

Magnetic resonance imaging (MRI) T1 relaxometry (mapping) has been reported as a quantitative biomarker of liver injury due to inflammation and fibrosis.

OBJECTIVE

To assess the relationship between liver MRI T1 relaxometry measurements obtained using a modified Look-Locker inversion recovery (MOLLI) pulse sequence without and with iron (T2*) correction (cT1) in pediatric autoimmune liver disease.

MATERIALS AND METHODS

This cross-sectional study was institutional review board-approved, with informed consent obtained. MRI was acquired at 1.5 T in patients participating in an autoimmune liver disease registry. T1 relaxometry was performed using a MOLLI sequence with a 5(3)3-s acquisition strategy. A multi-echo gradient echo sequence was used to measure liver T2*. Non-iron-corrected native T1 (ms), calculated as the mean of four slices through the mid-liver, was measured using T1 parametric maps generated off-line. A proprietary T2* correction (Perspectum Diagnostics, Oxford, UK), blinded to native T1 values, calculated cT1 values. The relationship between native T1 and cT1 measurements was assessed using Spearman rank correlation and Bland-Altman analyses.

RESULTS

Forty-eight patients with a mean (standard deviation [SD]) age of 15.2 (4.1) years were included. Mean (SD) liver native T1 was 651.2 (123.9) ms and mean (SD) cT1 was 919.5 (86.8) ms, with excellent positive correlation between values (r=0.91 [95% confidence interval (CI): 0.85-0.95]; P<0.0001). Mean bias between native T1 and cT1 measurements was 268.3 ms (95% limits of agreement: 131.9-404.7 ms).

CONCLUSION

There is excellent positive correlation between liver native T1 and cT1 measurements in pediatric patients with autoimmune liver disease. This relationship brings into question the need to perform T1 iron correction in this patient population. T1 and cT1 measurements are not interchangeable, however, due to considerable systematic bias with cT1 values being considerably higher.

Nonalcoholic Fatty Liver Disease in Children: Unique Considerations and Challenges

Nonalcoholic fatty liver disease (NAFLD) is increasing in prevalence in concert with the global epidemic of obesity and is being diagnosed at increasingly younger ages. The unique histologic features and early presentation of disease in pediatrics suggest that children and adults may differ with regard to etiopathogenesis, with children displaying a greater vulnerability to genetic and environmental factors. Of significant relevance to pediatrics, in utero and perinatal stressors may alter the lifelong health trajectory of a child, increasing the risk of NAFLD and other cardiometabolic diseases. The development and progression of disease in childhood is likely to carry increased risk of long-term morbidity. Novel biomarkers and therapeutic agents are needed to avoid the otherwise inevitable health and societal consequences of this rapidly expanding pediatric population.

Diagnostic accuracy of texture analysis and machine learning for quantification of liver fibrosis in MRI: correlation with MR elastography and histopathology

OBJECTIVES

To compare the diagnostic accuracy of texture analysis (TA)-derived parameters combined with machine learning (ML) of non-contrast-enhanced T1w and T2w fat-saturated (fs) images with MR elastography (MRE) for liver fibrosis quantification.

METHODS

In this IRB-approved prospective study, liver MRIs of participants with suspected chronic liver disease who underwent liver biopsy between August 2015 and May 2018 were analyzed. Two readers blinded to clinical and histopathological findings performed TA. The participants were categorized into no or low-stage (0-2) and high-stage (3-4) fibrosis groups. Confusion matrices were calculated using a support vector machine combined with principal component analysis. The diagnostic accuracy of ML-based TA of liver fibrosis and MRE was assessed by area under the receiver operating characteristic curves (AUC). Histopathology served as reference standard.

RESULTS

A total of 62 consecutive participants (40 men; mean age ± standard deviation, 48 ± 13 years) were included. The accuracy of TA and ML on T1w was 85.7% (95% confidence interval [CI] 63.7-97.0) and 61.9% (95% CI 38.4-81.9) on T2w fs for classification of liver fibrosis into low-stage and high-stage fibrosis. The AUC for TA on T1w was similar to MRE (0.82 [95% CI 0.59-0.95] vs. 0.92 [95% CI 0.71-0.99], p = 0.41), while the AUC for T2w fs was significantly lower compared to MRE (0.57 [95% CI 0.34-0.78] vs. 0.92 [95% CI 0.71-0.99], p = 0.008).

CONCLUSION

Our results suggest that liver fibrosis can be quantified with TA-derived parameters of T1w when combined with a ML algorithm with similar accuracy compared to MRE.

KEY POINTS

• Liver fibrosis can be categorized into low-stage fibrosis (0-2) and high-stage fibrosis (3-4) using texture analysis-derived parameters of T1-weighted images with a machine learning approach. • For the differentiation of low-stage fibrosis and high-stage fibrosis, the diagnostic accuracy of texture analysis on T1-weighted images combined with a machine learning algorithm is similar compared to MR elastography.

Community Socioeconomic Deprivation and Nonalcoholic Fatty Liver Disease Severity

BACKGROUND AND OBJECTIVES

Nonalcoholic fatty liver disease (NAFLD) is linked to obesity. Obesity is associated with lower socioeconomic status (SES). An independent link between pediatric NAFLD and SES has not been elucidated. The objective of this study was to evaluate the distribution of socioeconomic deprivation, measured using an area-level proxy, in pediatric patients with known NAFLD and to determine whether deprivation is associated with liver disease severity.

METHODS

Retrospective study of patients <21 years with NAFLD, followed from 2009 to 2018. The patients' addresses were mapped to census tracts, which were then linked to the community deprivation index (CDI; range 0--1, higher values indicating higher deprivation, calculated from six SES-related variables available publicly in US Census databases).

RESULTS

Two cohorts were evaluated; 1 with MRI (magnetic resonance imaging) and/or MRE (magnetic resonance elastography) findings indicative of NAFLD (n = 334), and another with biopsy-confirmed NAFLD (n = 245). In the MRI and histology cohorts, the majority were boys (66%), non-Hispanic (77%-78%), severely obese (79%-80%), and publicly insured (55%-56%, respectively). The median CDI for both groups was 0.36 (range 0.15-0.85). In both cohorts, patients living above the median CDI were more likely to be younger at initial presentation, time of MRI, and time of liver biopsy. MRI-measured fat fraction and liver stiffness, as well as histologic characteristics were not different between the high- and low-deprivation groups.

CONCLUSIONS

Children with NAFLD were found across the spectrum of deprivation. Although children from more deprived neighborhoods present at a younger age, they exhibit the same degree of NAFLD severity as their peers from less deprived areas.

Newly Developed Methods for Reducing Motion Artifacts in Pediatric Abdominal MRI: Tips and Pearls

OBJECTIVE. The purpose of this article is to review established and emerging methods for reducing motion artifacts in pediatric abdominal MRI. CONCLUSION. Clearly understanding the strengths and limitations of motion reduction methods can enable practitioners of pediatric abdominal MRI to select and combine the appropriate techniques and potentially reduce the need for sedation and anesthesia.

Severe obesity is associated with liver disease severity in pediatric non-alcoholic fatty liver disease

BACKGROUND

Paediatric non-alcoholic fatty liver disease (NAFLD) is highly prevalent among children with obesity. The primary objective of this study was determining whether obesity severity is associated with NAFLD severity. By using paediatric classifications for severe obesity, clinicians may be able to better risk stratify patients, which in turn would guide more effective management and treatment.

METHODS

Retrospective cohort study including patients followed at Cincinnati Children's Medical Center for NAFLD. Patients were categorized as overweight or class I, II, III obese based on established body mass index (BMI) cut-offs. Liver disease severity was determined using biochemical, imaging (magnetic resonance elastography [MRE]), and histologic evidence of liver injury.

RESULTS

Three cohorts were studied individually based on the method used to assess disease severity (biochemical n = 767, imaging n = 366, and histology n = 249). Between the three cohorts, there were significant differences in age, proportion of patients with class II and class III obesity, and serum alanine transaminase (ALT) levels. In the biochemistry cohort, the odds of having ALT > 80 U/L were highest in patients with class III obesity (P = .026). In the imaging cohort, liver stiffness was significantly different between BMI groups of patients (P = .001). In the histology cohort, those with class III obesity had significantly higher odds of NAFLD activity score (NAS) ≥ 5 (P = .012).

DISCUSSION

Obesity severity is associated with liver disease severity. Patients with more severe obesity are more likely to have more advanced liver disease, a finding that can assist in risk stratification, as well as monitoring and treatment approaches.

Designing Clinical Trials in Pediatric Nonalcoholic Steatohepatitis: Tips for Patient Selection and Appropriate Endpoints

Nonalcoholic fatty liver disease (NAFLD) is common in children and may progress to nonalcoholic steatohepatitis (NASH), advanced fibrosis, and even cirrhosis in childhood or early adulthood, indicating the need for pharmacologic treatment in this age group. Multiple trials are evaluating different therapeutic targets for NASH with fibrosis in adults, and the U.S. Food and Drug Administration has recently provided clear guidance to the pharmaceutical industry on developing drugs for the treatment of noncirrhotic NASH with liver fibrosis. Pediatric NAFLD has several unique aspects that distinguish it from the adult disease in terms of histology, our understanding of the natural history, and the utility of noninvasive tests. These differences have the potential to impact the design of clinical trials to test different drugs in the pediatric population. The aim of this article is to provide a review of common misconceptions regarding pediatric NAFLD and key differences from adult NAFLD. We have provided our recommendations on the design of early proof-of-concept and late phase 2 trials based on lessons learned from previous clinical trials. We believe that clinical drug development for children with NAFLD should happen in parallel with ongoing adult trials.

Assessment of liver T1 mapping in fontan patients and its correlation with magnetic resonance elastography-derived liver stiffness

OBJECTIVES

To explore the utility of liver T1 mapping in Fontan patients and its correlation to magnetic resonance elastography (MRE)-derived liver stiffness.

BACKGROUND AND AIMS

Liver disease is a major long-term extra cardiac complication in the Fontan population. MRE is frequently used to quantify liver stiffness in Fontan patients; however, it has certain limitations. Native T1 mapping by cardiac magnetic resonance (CMR) is useful in assessment of cardiac fibrosis, but its potential in evaluating liver fibrosis and its correlation to MRE-derived liver stiffness in Fontan patients have not been reported.

METHODS

Fontan patients who underwent CMR and MRE were included. Liver Native T1, extracellular volume (ECV) and delta coefficients were measured and correlated with MRE-derived liver stiffness in all Fontan patients. Native liver T1 in Fontan patients were compared to normal controls with biventricular circulation and no known liver disease.

RESULTS

A total of 17 Fontan patients and 7 normal controls were included in this study. Fontan patients had significantly higher liver native T1 (690 ± 41 ms vs 620 ± 35 ms; p < 0.001) as compared to controls. There was strong positive correlation between MRE derived liver stiffness and liver native T1 (r = 0.81, p < 0.001).

CONCLUSIONS

Liver native T1 was significantly elevated in Fontan patients compared to controls and strongly correlated with MRE-derived liver stiffness. This technique may prove to be a useful noninvasive imaging biomarker for assessing liver fibrosis in the Fontan population.

Pediatric NAFLD: an overview and recent developments in diagnostics and treatment

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in children and adults in industrialized countries. Besides liver-related morbidity, NAFLD is also associated with an increased risk of cardiovascular disease, type 2 diabetes and mortality at adult age. However, despite the high prevalence and serious complications, diagnosing and staging of disease remains complicated due to a lack of accurate screening tools and non-invasive methods to detect fibrosis. Areas covered: Recent insights in epidemiology, pathogenesis, diagnostic evaluation and treatment options in pediatric NAFLD are being reviewed, with a particular focus on new developments in diagnostic tools. Expert opinion: Due to their long life span, children with NAFLD are particularly at risk of complications in their lifetime. Therefore, an effective screening strategy for children to identify those with NAFLD at risk of complications is urgently needed. This is further underscored by new pharmacological therapies that are expected to become available in the next 5 years. Momentarily no accurate non-invasive method for diagnosing pediatric NAFLD is available. New promising biomarkers and imaging tools could hopefully provide better screening tools and could contribute to the development of a successful management plan to identify children with NAFLD.

Magnetic resonance elastography SE-EPI vs GRE sequences at 3T in a pediatric population with liver disease

PURPOSE

The goal of our study is to compare hepatic stiffness measures using gradient-recalled echo (GRE) versus spin-echo echo planar imaging (SE-EPI)-based MR Elastography (MRE) at 3T used to measure hepatic stiffness in a patients with suspected liver diseases.

MATERIALS AND METHODS

This retrospective study included 52 patients with liver disease who underwent a 3T MRE exam including both an investigational SE-EPI-based technique and a product GRE-based technique. Regions of interest (ROI) were placed on the elastograms to measure elastography-derived liver stiffness as well as the area included within the ROIs. The mean liver stiffness values and area of ROIs were compared.

RESULTS

The mean liver stiffness was 3.72 kilopascal (kPa) ± 1.29 using GRE MRE and 3.78 kPa ± 1.13 using SE-EPI MRE. Measurement of liver stiffness showed excellent agreement between the two pulse sequences with a mean bias of - 0.1 kPa (range - 1.8 to 1.7 kPa) between sequences. The mean measurable ROI area was higher with SE-EPI (313.8 cm² ± 213.8) than with the GRE technique (208.6 cm² ± 114.8), and the difference was statistically significant (P < 0.05).

CONCLUSIONS

Our data shows excellent agreement of measured liver stiffness between GRE and SE-EPI-based sequences at 3T. Our results show the advantage of a SE-EPI MRE sequence in terms of image quality, ROI size and acquisition time with equivalent liver stiffness measurements as compared to GRE-MRE sequence.

Diagnostic performance of quantitative magnetic resonance imaging biomarkers for predicting portal hypertension in children and young adults with autoimmune liver disease

BACKGROUND

Primary sclerosing cholangitis, autoimmune hepatitis and autoimmune sclerosing cholangitis are forms of chronic, progressive autoimmune liver disease (AILD) that can affect the pediatric population.

OBJECTIVE

To determine whether quantitative MRI- and laboratory-based biomarkers are associated with conventional imaging findings of portal hypertension (radiologic portal hypertension) in children and young adults with AILD.

MATERIALS AND METHODS

Forty-four patients with AILD enrolled in an institutional registry underwent a research abdominal MRI examination at 1.5 tesla (T). Five quantitative MRI techniques were performed: liver MR elastography, spleen MR elastography, liver iron-corrected T1 mapping, liver T2 mapping, and liver diffusion-weighted imaging (DWI, quantified as apparent diffusion coefficients). Two anatomical sequences were used to document splenomegaly, varices and ascites. We calculated aspartate aminotransferase (AST)-to-platelet ratio index (APRI) and fibrosis-4 (FIB-4) scores - laboratory-based biomarkers of liver fibrosis. We used receiver operating characteristic (ROC) curve analyses to establish the diagnostic performance of quantitative MRI and laboratory biomarkers for indicating the presence of radiologic portal hypertension.

RESULTS

Twenty-three (52%) patients were male; mean age was 15.2±4.0 years. Thirteen (30%) patients had radiologic portal hypertension. Liver and spleen stiffness demonstrated the greatest diagnostic performance for indicating the presence of portal hypertension (area-under-the-ROC-curve [AUROC]=0.98 and 0.96, respectively). The APRI and FIB-4 scores also demonstrated good diagnostic performance (AUROC=0.87 and 0.88, respectively).

CONCLUSION

MRI-derived measures of liver and spleen stiffness as well as laboratory-based APRI and FIB-4 scores are highly associated with imaging findings of portal hypertension in children and young adults with AILD and thus might be useful for predicting portal hypertension impending onset and directing personalized patient management.