Normal range for MR elastography measured liver stiffness in children without liver disease

Metabolic dysfunction-associated steatotic liver disease in children

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease, is the most common cause of chronic liver disease in children. MASLD encompasses a spectrum of liver disease and can be severe, with 10% of affected children presenting with advanced fibrosis. While biopsy remains the most accurate method for diagnosing and staging the disease, MRI proton density fat fraction and magnetic resonance elastography are the most reliable non-invasive measures for assessing steatosis and fibrosis, respectively. MASLD is associated with multiple comorbidities including type 2 diabetes, hypertension, dyslipidaemia, decreased bone mineral density, obstructive sleep apnoea, anxiety and depression. Currently, there are no pharmacological treatments available for children, highlighting the urgent need for paediatric clinical trials. A diet low in free sugars is promising for reducing steatosis and decreasing alanine aminotransferase, a surrogate marker for hepatic inflammation. Emerging data indicate that steatosis can be present in children under 6 years of age, which was previously considered rare. The intricate interplay of genetics may inform future therapeutics and prognostication, with the PNPLA3 gene showing the most evidence for association with the risk and severity of steatotic liver disease and steatohepatitis. MASLD is a complex disease affecting one in ten children and is associated with increased early mortality risk. More dedicated studies are needed in children to advance our understanding of this disease and find effective treatments.

Multi-site, multi-vendor development and validation of a deep learning model for liver stiffness prediction using abdominal biparametric MRI

BACKGROUND

Chronic liver disease (CLD) is a substantial cause of morbidity and mortality worldwide. Liver stiffness, as measured by MR elastography (MRE), is well-accepted as a surrogate marker of liver fibrosis.

PURPOSE

To develop and validate deep learning (DL) models for predicting MRE-derived liver stiffness using routine clinical non-contrast abdominal T1-weighted (T1w) and T2-weighted (T2w) data from multiple institutions/system manufacturers in pediatric and adult patients.

MATERIALS AND METHODS

We identified pediatric and adult patients with known or suspected CLD from four institutions, who underwent clinical MRI with MRE from 2011 to 2022. We used T1w and T2w data to train DL models for liver stiffness classification. Patients were categorized into two groups for binary classification using liver stiffness thresholds (≥ 2.5 kPa, ≥ 3.0 kPa, ≥ 3.5 kPa, ≥ 4 kPa, or ≥ 5 kPa), reflecting various degrees of liver stiffening.

RESULTS

We identified 4695 MRI examinations from 4295 patients (mean ± SD age, 47.6 ± 18.7 years; 428 (10.0%) pediatric; 2159 males [50.2%]). With a primary liver stiffness threshold of 3.0 kPa, our model correctly classified patients into no/minimal (< 3.0 kPa) vs moderate/severe (≥ 3.0 kPa) liver stiffness with AUROCs of 0.83 (95% CI: 0.82, 0.84) in our internal multi-site cross-validation (CV) experiment, 0.82 (95% CI: 0.80, 0.84) in our temporal hold-out validation experiment, and 0.79 (95% CI: 0.75, 0.81) in our external leave-one-site-out CV experiment. The developed model is publicly available ( https://github.com/almahdir1/Multi-channel-DeepLiverNet2.0.git ).

CONCLUSION

Our DL models exhibited reasonable diagnostic performance for categorical classification of liver stiffness on a large diverse dataset using T1w and T2w MRI data.

KEY POINTS

Question Can DL models accurately predict liver stiffness using routine clinical biparametric MRI in pediatric and adult patients with CLD? Findings DeepLiverNet2.0 used biparametric MRI data to classify liver stiffness, achieving AUROCs of 0.83, 0.82, and 0.79 for multi-site CV, hold-out validation, and external CV. Clinical relevance Our DeepLiverNet2.0 AI model can categorically classify the severity of liver stiffening using anatomic biparametric MR images in children and young adults. Model refinements and incorporation of clinical features may decrease the need for MRE.

Dihydroxyacetone phosphate is a novel predictor of hepatic fibrosis in Latino adolescents with obesity

OBJECTIVES

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common pediatric liver disease and can progress to liver fibrosis. Latino adolescents have increased MASLD and fibrosis risk. While fibrosis is diagnosed by biopsy or imaging, more accessible, noninvasive, and economical screening methods are needed. We aimed to use plasma metabolomics/lipidomics to identify potential fibrosis biomarkers in Latino adolescents with obesity.

METHODS

Liver stiffness (LS) was measured in 93 Latino adolescents with obesity using magnetic resonance elastography. Metabolites and lipids were extracted from plasma and identified on Compound Discoverer. Associations between metabolites/lipids and fibrosis (LS > 2.73 kPa) were determined using linear regression models after covariate adjustment. False discovery rate (FDR) adjusted Pearson's correlations were performed. Analytes yielding significant FDR-adjusted correlations were examined further by receiver operator curve analysis.

RESULTS

Mean (±standard deviation) alanine transaminase (ALT) was 45.7(±65.2) IU/L, hepatic fat fraction was 12.7(±9.1)%, and LS was 2.4(±0.3) kPa. We identified 795 metabolites and 413 lipids in plasma, but only one single metabolite, dihydroxyacetone phosphate (DHAP), a marker of triglyceride synthesis, was significantly associated with fibrosis after FDR adjustment (p < 0.05). In terms of predicting fibrosis, ALT had an area under the curve (AUC) of 0.79, and DHAP had an AUC of 0.79. When combined, ALT + DHAP had an AUC of 0.89.

CONCLUSIONS

The combination of ALT + DHAP may have the potential as an accurate, noninvasive test for liver fibrosis. Our data are limited to Latino children with obesity, and a larger cohort should be examined to further validate this novel biomarker.

Practical approach to quantitative liver and pancreas MRI in children

Quantitative abdominal magnetic resonance imaging (MRI) offers non-invasive, objective assessment of diseases in the liver, pancreas, and other organs and is increasingly being used in the pediatric population. Certain quantitative MRI techniques, such as liver proton density fat fraction (PDFF), R2* mapping, and MR elastography, are already in wide clinical use. Other techniques, such as liver T1 mapping and pancreas quantitative imaging methods, are emerging and show promise for enhancing diagnostic sensitivity and treatment monitoring. Quantitative imaging techniques have historically required a breath-hold, making them more difficult to implement in the pediatric population. However, technological advances, including free-breathing techniques and compressed sensing imaging, are making these techniques easier to implement. The purpose of this article is to review current liver and pancreas quantitative techniques and to provide a practical guide for implementing these techniques in pediatric practice. Future directions of liver and pancreas quantitative imaging will be briefly discussed.

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.

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.

Ambient air pollution exposure is associated with liver fat and stiffness in Latino youth with a more pronounced effect in those with PNPLA3 genotype and more advanced liver disease

BACKGROUND

Exposure to ambient air pollutants has emerged as a risk for metabolic-dysfunction associated steatotic liver disease (MASLD).

OBJECTIVES

We sought to examine associations between short-term (prior month) and long-term (prior year) ambient air pollution exposure with hepatic fat fraction (HFF) and liver stiffness in Latino youth with obesity. A secondary aim was to investigate effect modification by patatin-like phospholipase domain-containing protein 3 (PNPLA3) genotype and liver disease severity.

METHODS

Data was analyzed from 113 Latino youth (age 11-19) with obesity in Southern California. Individual exposure to particulate matter with aerodynamic diameter ≤ 2.5μm (PM2.5), ≤ 10μm (PM10), nitrogen dioxide (NO2), 8-hour maximum ozone (8hrMax-O3), 24-hr O3, and redox-weighted oxidative capacity (Oxwt) were estimated using residential address histories and United States Environmental Protection Agency air quality observations. HFF and liver stiffness were measured using magnetic resonance imaging. Linear models were used to determine associations between short-term and long-term exposure to air pollutants with HFF and liver stiffness. Modification by PNPLA3 and liver disease severity was then examined.

RESULTS

Short-term exposure to 8hrMax-O3 was positively associated with HFF. Relationships between air pollution exposure and HFF were not impacted by PNPLA3 genotype or liver disease severity. Long-term exposure to 8hrMax-O3 and Oxwt were positively associated with liver stiffness. Associations between air pollution exposure and liver stiffness depended on PNPLA3 genotype, such that individuals with GG genotypes exhibited stronger, more positive relationships between short-term exposure to PM10, 8hrMax-O3, 24-hr O3, and Oxwt and liver stiffness than individuals with CC/CG genotypes. In addition, relationships between short-term exposure to NO2 and liver stiffness were stronger in those with severe liver disease.

DISCUSSION

Air pollution exposure may be a risk factor for liver disease among Latino youth with obesity, particularly in those with other preexisting risks for liver damage.

Liver fibrosis and liver stiffness in patients with obesity and type 1 diabetes

AIM

To compare hepatic stiffness and fat fraction in patients with obesity and type 1 diabetes (T1D) with type 2 diabetes (T2D) with a similar body mass index (BMI).

METHODS

In this prospective cross-sectional study, 90 participants with T1D (BMI 30.5 ± 4.5 kg/m2; diabetes duration 20.5 ± 9.8 years; HbA1c 8.2% ± 1.4%) and 69 with T2D (BMI: 30.8 ± 4.6 kg/m2; diabetes duration: 11.7 ± 7.8 years; HbA1c: 7.3% ± 1.4%) were included. Liver fat fraction and stiffness were examined by magnetic resonance imaging and elastography, respectively. Logistic regressions were used to evaluate associations with biomedical variables.

RESULTS

The mean liver stiffness score in patients with obesity and T1D was 2.2 ± 0.5 kPa, while in T2D it was 2.6 ± 0.8 kPa (P < .001). The liver fat fraction in patients with obesity and T1D was 3.7% ± 6.3%, and in T2D it was 10.6% ± 7.9% (P < .001). Metabolic dysfunction-associated steatotic liver disease (MASLD) was present in 13.3% of patients with T1D and in 69.6% of patients with T2D, whereas fibrosis was suggested in 7.8% of patients with T1D and in 27.5% of patients with T2D. Liver stiffness was four times higher in patients with T2D compared with those with T1D (odds ratio = 5.4, 95% confidence interval: 2.1-13.6, P < .001). Aspartate transaminase (AST), alanine transaminase, gamma-glutamyl transferase (GGT), triglycerides and the android-to-gynoid ratio were associated with elevated fat fraction in both cohorts. AST and GGT were associated with elevated liver stiffness in both cohorts.

CONCLUSIONS

Patients with obesity and T1D had lower liver fat and liver stiffness compared with those patients with T2D, despite similar levels of BMI, a longer duration of diabetes and worse glycaemic control.

Associations of dietary sugars with liver stiffness in Latino adolescents with obesity differ on PNPLA3 and liver disease severity

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common paediatric liver disease. Latinos have high MASLD risk due to 50% prevalence of GG genotype of PNPLA3. Our primary aim was to evaluate associations between dietary carbohydrates/sugars and liver stiffness in Latino adolescents with obesity. Our secondary aim was to examine effect modification by (a) PNPLA3 genotype or (b) liver disease severity. Data were obtained from 114 Latino adolescents with obesity involved in two prior studies. No associations were seen between dietary carbohydrates/sugars and liver stiffness in the group as a whole. In subjects with GG genotype of PNPLA3, total sugar, fructose, sucrose, and glucose were associated with liver stiffness. Positive relationships between carbohydrate, total sugar, and sucrose and liver stiffness were stronger in those with MASLD and fibrosis compared to those with healthy livers and MASLD without fibrosis.

Towards a Standardized Classification of the Hepatobiliary Manifestations in Cystic Fibrosis (CFHBI): A Joint ESPGHAN/NASPGHAN Position Paper

The broad spectrum of hepatobiliary involvement in cystic fibrosis (CF) has been commonly referred to as cystic fibrosis liver disease (CFLD). However, differences in the definitions of CFLD have led to variations in reported prevalence, incidence rates, and standardized recommendations for diagnosis and therapies. Harmonizing the description of the spectrum of hepatobiliary involvement in all people with CF (pwCF) is deemed essential for providing a reliable account of the natural history, which in turn supports the development of meaningful clinical outcomes in patient care and research. Recognizing this necessity, The European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) and the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN) commissioned and tasked a committee to develop and propose a systematic classification of the CF hepatobiliary manifestations to increase uniformity, accuracy, and comparability for clinical, registry, and research purposes. This report describes the committee's combined expert position statement on hepatobiliary involvement in CF, which has been endorsed by NASPGHAN and ESPGHAN. We recommend using CFHBI (Cystic Fibrosis Hepato-Biliary Involvement) as the updated term to describe and classify all hepatobiliary manifestations in all pwCF. CFHBI encompasses the current extensive spectrum of phenotypical, clinical, or diagnostic expressions of liver involvement observed in pwCF. We present a schematic categorization of CFHBI, which may also be used to track and classify the changes and development of CFHBI in pwCF over time. The proposed classification for CFHBI is based on expert consensus and has not been validated for clinical practice and research purposes. Achieving validation should be an important aim for future research.

Nonalcoholic fatty liver disease and insulin resistance in children

Nonalcoholic fatty liver disease (NAFLD), a spectrum of liver diseases characterized by excessive fat accumulation, is the leading cause of chronic liver disease. The global prevalence of NAFLD is increasing in both adults and children. In Korea, the prevalence of pediatric NAFLD increased from 8.2% in 2009 to 12.1% in 2018 according to a national surveillance study. For early screening of pediatric NAFLD, laboratory tests including aspartate aminotransferase and alanine aminotransferase; biomarkers including hepatic steatosis index, triglyceride glucose index, and fibrosis-4 index; and imaging studies including ultrasonography and magnetic resonance imaging are required. Insulin resistance plays a major role in the pathogenesis of NAFLD, which promotes insulin resistance. Thus, the association between NAFLD and insulin resistance, diabetes mellitus, and metabolic syndrome has been reported in many studies. This review addresses issues related to the epidemiology and investigation of NAFLD as well as the association between NAFLD and insulin resistance and metabolic syndrome with focus on pediatric NAFLD.

Liver Disease-Related Sarcopenia: A Predictor of Poor Prognosis by Accelerating Hepatic Decompensation in Advanced Chronic Liver Disease

Background Sarcopenia is considered a prognostic factor for advanced chronic liver disease (ACLD) independent of liver function, but the underlying mechanisms are unknown. Here, we investigated whether sarcopenia contributed to hepatic decompensation and worsened prognosis. Methods This was a single-center retrospective study of 708 patients with chronic liver disease who underwent magnetic resonance elastography (MRE). Magnetic resonance imaging (MRI) was used to diagnose sarcopenia and hepatic decompensation (presence of ascites). Results The incidence of sarcopenia (29% overall) and age were significantly correlated to increased liver stiffness (LS) (p < 0.01 each), but age did not differ for LS ≥ 4 kPa. Rates of thrombocytopenia and varices increased at ≥4 kPa, and ascites (n = 52) accounted for 81% of patients with ≥6 kPa LS. Age, alcoholic liver disease, C-reactive protein, sodium level, and controlling nutritional status score were extracted as factors contributing to sarcopenia (all p < 0.05). In ACLD, sarcopenia was an independent predictor of ascites (p < 0.01), and in a follow-up analysis of 163 patients without ascites at baseline, the incidence of ascites in patients with sarcopenia was significantly higher, even after adjusting for LS and liver severity (p < 0.01). The Cox proportional hazards model indicated albumin-bilirubin score and sarcopenia as independent prognostic factors (p < 0.01 each). Conclusions In ACLD, both portal hypertension and liver disease-related sarcopenia were found to occur at ≥4 kPa. Sarcopenia was accompanied by mildly decreased sodium levels and contributed to the early development of ascites and poor prognosis, independent of liver function.

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.

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.

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.

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.

A tailored passive driver for liver MRE in pediatric patients

Objectives

Magnetic resonance elastography (MRE) is increasingly used in the pediatric population for diagnosis and staging of liver fibrosis. However, the MR-compatible driver and sequences are usually those used for adult patients. Our feasibility study aimed to adapt the standardized adult MRE passive driver and vibrational parameters to a pediatric population.

Methods

We designed an elliptic passive driver shaped on a torus equipped with an elastic membrane and adapted to children's morphologies. As a first step, eight children (aged 8-18 years) were enrolled in a prospective pilot study aiming to determine the threshold vibrational amplitude for MRE using a custom passive driver, based on phase aliasing assessment and the occurrence of signal void artifacts on magnitude MR images. In the second step, the practicality and the consistency of the custom driver were assessed in a further 11 pediatric patients (aged 7-18 years). In the third step, we compared our custom driver vs. the commercial driver on six adult volunteers, in terms of the reliable region of interest area within the acquired MRE slices, the shear wave maps' quality, and measured stiffness values obtained.

Results

Based on pediatric patient data, the threshold vibrational amplitude expressed as percentage of maximum output was found to be 0.4 and 1.1 times the body weight (kg) at 40 and 60 Hz frequencies, respectively. In comparison to the commercial passive driver, the custom driver improved threefold the contact with the body surface, also enabling a more comfortable examination as self-assessed by the volunteers.

Conclusions

Our custom driver was more comfortable for the volunteers and was able to generate more homogenous shear waves, yielding larger usable hepatic area, and more reliable stiffness values.

Recent advances in the epidemiology of nonalcoholic fatty liver disease in children

Children with obesity are at risk for numerous health problems, including nonalcoholic fatty liver disease (NAFLD). This review focuses on progress made in the epidemiology of NAFLD in children for the years 2015-2020. The estimated prevalence of NAFLD in children with obesity is 26%. The incidence of NAFLD in children has risen rapidly over the past decade. An understanding of the reasons for this rise is incomplete, but over the past 5 years, many studies have provided additional insight into the complexity of risk factors, diagnostic approaches, and associated comorbidities. Risk factors for NAFLD are wide-ranging, including perinatal factors involving both the mother and newborn, as well as environmental toxin exposure. Progress made in the noninvasive assessment will be critical to improving issues related to variability in approach to screening and diagnosis of NAFLD in children. The list of serious comorbidities observed in children with NAFLD continues to grow. Notably, for many of these conditions, such as diabetes and depression, the rates observed have exceeded the rates reported in children with obesity without NAFLD. Recent advancements reviewed show an increased awareness of this problem, while also calling attention to the need for additional research to guide successful efforts at prevention and treatment.

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.

PNPLA3 Genotype, Arachidonic Acid Intake, and Unsaturated Fat Intake Influences Liver Fibrosis in Hispanic Youth with Obesity

Non-alcoholic fatty liver disease impacts 15.2% of Hispanic adolescents and can progress to a build-up of scared tissue called liver fibrosis. If diagnosed early, liver fibrosis may be reversible, so it is necessary to understand risk factors. The aims of this study in 59 Hispanic adolescents with obesity were to: (1) identify potential biological predictors of liver fibrosis and dietary components that influence liver fibrosis, and (2) determine if the association between dietary components and liver fibrosis differs by PNPLA3 genotype, which is highly prevalent in Hispanic adolescents and associated with elevated liver fat. We examined liver fat and fibrosis, genotyped for PNPLA3 gene, and assessed diet via 24-h diet recalls. The prevalence of increased fibrosis was 20.9% greater in males, whereas participants with the GG genotype showed 23.7% greater prevalence. Arachidonic acid was associated with liver fibrosis after accounting for sex, genotype, and liver fat (β = 0.072, p = 0.033). Intakes of several dietary types of unsaturated fat have different associations with liver fibrosis by PNPLA3 genotype after accounting for sex, caloric intake, and liver fat. These included monounsaturated fat (βCC/CG = -0.0007, βGG = 0.03, p-value = 0.004), polyunsaturated fat (βCC/CG = -0.01, βGG = 0.02, p-value = 0.01), and omega-6 (βCC/CG = -0.0102, βGG = 0.028, p-value = 0.01). Results from this study suggest that reduction of arachidonic acid and polyunsaturated fatty acid intake might be important for the prevention of non-alcoholic fatty liver disease progression, especially among those with PNPLA3 risk alleles.

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.

DeepLiverNet: a deep transfer learning model for classifying liver stiffness using clinical and T2-weighted magnetic resonance imaging data in children and young adults

BACKGROUND

Although MR elastography allows for quantitative evaluation of liver stiffness to assess chronic liver diseases, it has associated drawbacks related to additional scanning time, patient discomfort, and added costs.

OBJECTIVE

To develop a machine learning model that can categorically classify the severity of liver stiffness using both anatomical T2-weighted MRI and clinical data for children and young adults with known or suspected pediatric chronic liver diseases.

MATERIALS AND METHODS

We included 273 subjects with known or suspected chronic liver disease. We extracted data including axial T2-weighted fast spin-echo fat-suppressed images, clinical data (e.g., demographic/anthropomorphic data, particular medical diagnoses, laboratory values) and MR elastography liver stiffness measurements. We propose DeepLiverNet (a deep transfer learning model) to classify patients into one of two groups: no/mild liver stiffening (<3 kPa) or moderate/severe liver stiffening (≥3 kPa). We conducted internal cross-validation using 178 subjects, and external validation using an independent cohort of 95 subjects. We assessed diagnostic performance using accuracy, sensitivity, specificity and area under the receiver operating characteristic curve (AuROC).

RESULTS

In the internal cross-validation experiment, the combination of clinical and imaging data produced the best performance (AuROC=0.86) compared to clinical (AuROC=0.83) or imaging (AuROC=0.80) data alone. Using both clinical and imaging data, the DeepLiverNet correctly classified patients with accuracy of 88.0%, sensitivity of 74.3% and specificity of 94.6%. In our external validation experiment, this same deep learning model achieved an accuracy of 80.0%, sensitivity of 61.1%, specificity of 91.5% and AuROC of 0.79.

CONCLUSION

A deep learning model that incorporates clinical data and anatomical T2-weighted MR images might provide a means of risk-stratifying liver stiffness and directing the use of MR elastography.

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.

Future of paediatric gastroenterology

This article explores what an 'ideal' paediatric gastroenterology department in the future should look like and what it could potentially provide if given carte blanche by health funds.

MR elastography of liver: current status and future perspectives

Non-invasive evaluation of liver fibrosis has evolved over the last couple of decades. Currently, elastography techniques are the most widely used non-invasive methods for clinical evaluation of chronic liver disease (CLD). MR elastography (MRE) of the liver has been used in the clinical practice for nearly a decade and continues to be widely accepted for detection and staging of liver fibrosis. With MRE, one can directly visualize propagating shear waves through the liver and an inversion algorithm in the scanner automatically converts the shear wave properties into an elastogram (stiffness map) on which liver stiffness can be calculated. The commonly used MRE method, two-dimensional gradient recalled echo (2D-GRE) sequence has produced excellent results in the evaluation of liver fibrosis in CLD from various etiologies and newer clinical indications continue to emerge. Advances in MRE technique, including 3D MRE, automated liver elasticity calculation, improvements in shear wave delivery and patient experience, are promising to provide a faster and more reliable MRE of liver. Innovations, including evaluation of mechanical parameters, such as loss modulus, displacement, and volumetric strain, are promising for comprehensive evaluation of CLD as well as understanding pathophysiology, and in differentiating various etiologies of CLD. In this review, the current status of the MRE of liver in CLD are outlined and followed by a brief description of advanced techniques and innovations in MRE of liver.

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.

Advances in Diagnostic Imaging in Pediatric Gastroenterology

PURPOSE OF REVIEW

The purpose is to provide a review of cross-sectional imaging updates in the assessment of gastrointestinal diseases, relevant to clinical practice and research.

RECENT FINDINGS

New magnetic resonance imaging contrast agents (Eovist) are taken up by hepatocytes and excreted via the biliary tree. As such, a lesion will retain contrast only if hepatocytes are present, which aids in refining the differential diagnosis. Magnetic resonance enterography is a method for non-invasively diagnosing and following various GI conditions, predominantly inflammatory bowel disease. Contrast-enhanced ultrasound uses gas-filled microbubbles providing superb temporal resolution most notably in the arterial phase, which aids in differentiating lesions. Elastography is a new technique which assesses stiffness of liver for evaluating fibrosis. These new techniques provide more accurate diagnoses and information, often limiting ionizing radiation exposure from other modalities. While ultrasound will still remain the initial imaging modality, familiarity with these other options is valuable for appropriate pathology workup.