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

Association Between MR Elastography Liver Stiffness and Histologic Liver Fibrosis in Children and Young Adults With Autoimmune Liver Disease

BACKGROUND. Liver fibrosis is an important clinical endpoint of the progression of autoimmune liver disease (AILD); its monitoring would benefit from noninvasive imaging tools. OBJECTIVE. The purpose of this study was to assess the relationship between MR elastography (MRE) liver stiffness measurements and histologic liver fibrosis, as well as to evaluate the performance of MRE and biochemical-based clinical markers for stratifying histologic liver fibrosis severity, in children and young adults with AILD. METHODS. This retrospective study used an existing institutional registry of children and young adults diagnosed with AILD (primary sclerosing cholangitis [PSC], autoimmune sclerosing cholangitis [ASC], or autoimmune hepatitis [AIH]). The registry was searched to identify patients who underwent both a research abdominal 1.5-T MRI examination that included liver MRE (performed for registry enrollment) and a clinically indicated liver biopsy within 6 months of that examination. MRE used a 2D gradient-recalled echo sequence. One analyst measured mean liver shear stiffness (in kilopascals) for each examination. Laboratory markers of liver fibrosis (aspartate aminotransferase-to-platelet ratio index [APRI] and fibrosis-4 [FIB-4] score) were recorded. For investigational purposes, one pathologist, blinded to clinical and MRI data, determined histologic Metavir liver fibrosis stage. The Spearman rank order correlation coefficient was calculated between MRE liver stiffness and Metavir liver fibrosis stage. ROC analysis was used to evaluate diagnostic performance for identifying advanced fibrosis (i.e., differentiating Metavir F0-F1 from F2-F4 fibrosis), and sensitivity and specificity were calculated using the Youden index. RESULTS. The study included 46 patients (median age, 16.6 years [IQR, 13.7-17.8 years]; 20 female patients, 26 male patients); 12 had PSC, 10 had ASC, and 24 had AIH. Median MRE liver stiffness was 2.9 kPa (IQR, 2.2-4.0 kPa). MRE liver stiffness and Metavir fibrosis stage showed strong positive correlation (ρ = 0.68). For identifying advanced liver fibrosis, MRE liver stiffness had an AUC of 0.81, with sensitivity of 65.4% and specificity of 90.0%; APRI had an AUC of 0.72, with sensitivity of 64.0% and specificity of 80.0%; and FIB-4 score had an AUC of 0.71, with sensitivity of 60.0% and specificity of 85.0%. CONCLUSION. MRE liver stiffness measurements were associated with histologic liver fibrosis severity. CLINICAL IMPACT. The findings support a role for MRE in noninvasive monitoring of liver stiffness, a surrogate for fibrosis, in children and young adults with AILD. TRIAL REGISTRATION. ClinicalTrials.gov NCT03175471.

Longitudinal changes in quantitative magnetic resonance imaging metrics in children and young adults with autoimmune liver disease

PURPOSE

To assess longitudinal changes in quantitative MRI metrics in pediatric and young adult patients with autoimmune liver disease (AILD).

METHODS

This prospective, IRB-approved study included 20 children and young adults (median age = 15 years) with primary sclerosing cholangitis (PSC)/autoimmune sclerosing cholangitis (ASC) and 19 (median age = 17 years) with autoimmune hepatitis (AIH). At a field strength of 1.5-T, T2*-corrected T1 mapping (cT1), 3D fast spin-echo MRCP, and 2D gradient recalled echo MR elastography (MRE) were performed at baseline, one year, and two years. cT1 and quantitative MRCP were processed using LiverMultiScan and MRCP + , respectively (Perspectum Ltd, Oxford, UK). Linear mixed models were used to assess longitudinal changes in quantitative MRI metrics. Spearman rank-order correlation was used to assess relationships between changes in quantitative MRI metrics.

RESULTS

Changes in quantitative MRI metrics greater than established repeatability coefficients were measured in six (cT1) and five (MRE) patients with PSC/ASC as well as in six patients (cT1 and MRE) with AIH, although linear mixed models identified no significant changes for the subgroups as a whole. For PSC/ASC, there were positive correlations between change in liver stiffness and changes in bile duct strictures (ρ = 0.68; p = 0.005) and bile duct dilations (ρ = 0.70; p = 0.004) between baseline and Year 2.

CONCLUSION

On average, there were no significant changes in quantitative MRI metrics over a two-year period in children and young adults with AILD. However, worsening cholangiopathy was associated with increasing liver stiffness by MRE in patients with PSC/ASC.

Automated CNN-Based Analysis Versus Manual Analysis for MR Elastography in Nonalcoholic Fatty Liver Disease: Inter-method Agreement and Fibrosis Stage Discriminative Performance

Background: Histological fibrosis stage is the most important prognostic factor in chronic liver disease. MR elastography (MRE) is the most accurate noninvasive method for detecting and staging liver fibrosis. Although accurate, manual ROI-based MRE analysis is complex, time consuming, requires specialized readers, and prone to methodologic variability and suboptimal inter-reader agreement. Objectives: To develop an automated convolutional neural network (CNN)-based method for liver MRE analysis, evaluate its agreement with manual ROI-based analysis, and assess its discriminative performance for dichotomized fibrosis stages using histology as reference standard. Methods: In this retrospective cross-sectional study, 675 participants who underwent MRE using different MRI systems and field strengths at 28 imaging sites from five multicenter international clinical trials of nonalcoholic steatohepatitis were included for algorithm development and internal testing of agreement between automated CNN- and manual ROI-based analyses. Eighty-one patients (52 women, 29 men; mean age, 54 years) who underwent MRE using a single 3-Tesla system and liver biopsy for clinical purposes at a single institution were included for external testing of agreement and assessment of fibrosis stage discriminative performance. Agreement was evaluated using intra-class correlation coefficients (ICC). 95% CIs were computed using bootstrapping. Discriminative performance of each method for dichotomized histologic fibrosis stage was evaluated by AUC and compared using bootstrapping. Results: Mean CNN- and manual ROI-based stiffness measurements ranged from 3.21 to 3.34 kPa in trial participants and from 3.30 to 3.45 kPa in clinical patients. ICC for CNN- and manual ROI-based measurements was 0.98 (95% CI, 0.978-0.98) in trial participants and 0.99 (95% CI: 0.98-0.99) in clinical patients. AUC for classification of dichotomized fibrosis stage ranged from 0.89-0.93 for CNN- and 0.87-0.93 for manual ROI-based analyses (p=.23-.75). Conclusion: Stiffness measurements using the automated CNN-based method agreed strongly with manual ROIbased analysis across MRI systems and field strengths, with excellent discriminative performance for histology-determined dichotomized fibrosis stages in external testing. Clinical Impact: Given the high incidence of chronic liver disease worldwide, it is important that noninvasive tools to assess fibrosis are applied reliably across different settings. CNN-based analysis is feasible and may reduce reliance on expert image analysts.

Associations Between Quantitative MRI Metrics and Clinical Risk Scores in Children and Young Adults With Autoimmune Liver Disease

Background: The Mayo risk score and SCOPE (Sclerosing Cholangitis Outcomes in Pediatrics) Index are clinical risk scores for monitoring progression of primary sclerosing cholangitis (PSC) and predict clinically important endpoints. Objective: To evaluate relationships of quantitative MRI measures of liver disease with clinical risk scores in children and young adults with autoimmune liver disease (AILD). Methods: This prospective study included 58 patients (35 male, 23 female; mean age, 15 years; range, 6-24 years) with AILD [PSC (n=16), autoimmune hepatitis (n=30), autoimmune sclerosing cholangitis (n=12)] who underwent research liver MRI examinations including: MR elastography (MRE), T2*-corrected T1 (cT1), and quantitative MRCP measurements. Associations between quantitative MRI metrics and clinical risk scores were evaluated using Spearman rank-order correlation coefficients and multivariable regression analyses. Results: Mean Mayo risk score was -1.1±0.9 (range: -2.9-1.1); mean SCOPE Index was 2.7±2.2 (range: 0-9). Mean liver stiffness was 2.8±1.1 kPa, mean whole-liver mean cT1 was 875±78 ms, and mean cT1 interquartile range (IQR) was 151±56 ms. Mayo risk score was significantly correlated with liver stiffness (r=0.56; p<.001), cT1 IQR (r=0.58; p<.001), whole-liver mean cT1 (r=0.31; p=.02), and multiple quantitative MRCP measures (r=0.36-0.45, p<.001). SCOPE Index was significantly correlated with liver stiffness (r=0.68; p<.001), cT1 IQR (r=0.51; p<.001), and multiple quantitative MRCP measures (r=0.47-0.49, p<.001). Multivariable linear regression analyses identified liver stiffness, cT1 IQR, and left hepatic duct maximum diameter as significant independent predictors of Mayo risk score (adjusted R2=0.45), and liver stiffness, cT1 IQR, common bile duct maximum (CBD) diameter, and CBD median diameter as significant independent predictors of SCOPE Index (adjusted R2=0.69). On logistic regression analysis, greater than low risk by SCOPE Index was best predicted by liver stiffness [odds ratio (OR)=49.6; 95% CI: 3.1-793.6) and CBD maximum diameter (OR=2.5; 95% CI: 1.3-4.7). Conclusion: Increased liver stiffness, increased cT1 IQR, and larger bile duct diameters are independently associated with higher (worse) Mayo risk score and SCOPE Index in children and young adults with AILD and may be surrogate markers of clinically meaningful endpoints. Clinical Impact: Multiparametric liver MRI incorporating quantitative metrics may serve as a noninvasive diagnostic and prognostic tool in pediatric AILD.

Magnetic resonance elastography of the liver: everything you need to know to get started

Magnetic resonance elastography (MRE) of the liver has emerged as the non-invasive standard for the evaluation of liver fibrosis in chronic liver diseases (CLDs). The utility of MRE in the evaluation of different CLD in both adults and children has been demonstrated in several studies, and MRE has been recommended by several clinical societies. Consequently, the clinical indications for evaluation of CLD with MRE have increased, and MRE is currently used as an add-on test during routine liver MRI studies or as a standalone test. To meet the increasing clinical demand, MRE is being installed in many academic and private practice imaging centers. There is a need for a comprehensive practical guide to help these practices to deliver high-quality liver MRE studies as well as troubleshoot the common issues with MRE to ensure smooth running of the service. This comprehensive clinical practice review summarizes the indications and provides an overview on why to use MRE, technical requirements, system set-up, patient preparation, acquiring the data, and interpretation.

Agreement Between Automated and Clinically Reported Manual ROI-Based MR Elastography Liver Stiffness Measurements in Children and Young Adults

MR elastography (MRE) typically requires manual ROI placement to generate liver shear stiffness measurements. Among 419 patients (primarily children and young adults), a computer-based automated MRE processing tool and clinically reported manual ROI-based measurements generated similar results (mean bias = 0.13 kPa). The intraclass correlation coefficient was 0.94 and was at least 0.90 across common indications in male and female patients and in patients with and without elevated liver fat fraction. Automated analysis may promote postprocessing standardization and decrease reporting variability.