Magnetic Resonance Elastography in Primary Sclerosing Cholangitis: Interobserver Agreement for Liver Stiffness Measurement with Manual and Automated Methods

Mechanical properties of human hepatic tissues to develop liver-mimicking phantoms for medical applications

Using liver phantoms for mimicking human tissue in clinical training, disease diagnosis, and treatment planning is a common practice. The fabrication material of the liver phantom should exhibit mechanical properties similar to those of the real liver organ in the human body. This tissue-equivalent material is essential for qualitative and quantitative investigation of the liver mechanisms in producing nutrients, excretion of waste metabolites, and tissue deformity at mechanical stimulus. This paper reviews the mechanical properties of human hepatic tissues to develop liver-mimicking phantoms. These properties include viscosity, elasticity, acoustic impedance, sound speed, and attenuation. The advantages and disadvantages of the most common fabrication materials for developing liver tissue-mimicking phantoms are also highlighted. Such phantoms will give a better insight into the real tissue damage during the disease progression and preservation for transplantation. The liver tissue-mimicking phantom will raise the quality assurance of patient diagnostic and treatment precision and offer a definitive clinical trial data collection.

Primary Sclerosing Cholangitis: Epidemiology, Diagnosis, and Presentation

Primary sclerosing cholangitis (PSC) is considered an immunologically mediated disease. However, some of its features are not consistent with the typical profile of autoimmune conditions. PSC is characterized by progressive biliary fibrosis that may ultimately result in the eventual development of cirrhosis. In recent years, multiple studies have reported that the incidence and prevalence of this disease are on the rise. Consequently, patients are often diagnosed without symptoms or signs of advanced liver disease, although many still present with signs of decompensated liver disease. This article discusses the epidemiology, clinical presentation, and diagnostic workup in patients with PSC.

Imaging of the biliary tract

PURPOSE OF REVIEW

Magnetic resonance cholangiopancreatography (MRCP) has become the reference examination for the exploration of the biliary tract and has replaced endoscopic cholangiography for the analysis of the biliary tract because of its equivalent performance and its noninvasive character.

RECENT FINDINGS

Based on the International Primary Sclerosing Cholangitis (PSC) Study Group recommendations for MR imaging in PSC, two protocols can be distinguished for the imaging of biliary tract: a basic protocol and a more complete protocol. It is essential to know the main pitfalls in order not to wrongly describe biliary anomalies. In addition to the excellent performance of MR imaging with MRCP in analyzing the anatomy and the anomalies of the biliary tree, complementary techniques have recently been developed. Several MR prognostic factors have been described. New hepato-specific contrast agents are now available for assessment of the general and segmental liver function. MR Elastography and Diffusion-weighted MR sequences are accurate to evaluate the degree of hepatic fibrosis. Finally, images obtained in MRCP can be postprocessed by a software that will analyze and model the biliary tree in order to quantitatively evaluate the biliary system.

SUMMARY

Magnetic resonance imaging with its recent developments becomes by now an essential tool for the evaluation of biliary diseases.

SWOT analysis of noninvasive tests for diagnosing NAFLD with severe fibrosis: an expert review by the JANIT Forum

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. Nonalcoholic steatohepatitis (NASH) is an advanced form of NAFLD can progress to liver cirrhosis and hepatocellular carcinoma (HCC). Recently, the prognosis of NAFLD/NASH has been reported to be dependent on liver fibrosis degree. Liver biopsy remains the gold standard, but it has several issues that must be addressed, including its invasiveness, cost, and inter-observer diagnosis variability. To solve these issues, a variety of noninvasive tests (NITs) have been in development for the assessment of NAFLD progression, including blood biomarkers and imaging methods, although the use of NITs varies around the world. The aim of the Japan NASH NIT (JANIT) Forum organized in 2020 is to advance the development of various NITs to assess disease severity and/or response to treatment in NAFLD patients from a scientific perspective through multi-stakeholder dialogue with open innovation, including clinicians with expertise in NAFLD/NASH, companies that develop medical devices and biomarkers, and professionals in the pharmaceutical industry. In addition to conventional NITs, artificial intelligence will soon be deployed in many areas of the NAFLD landscape. To discuss the characteristics of each NIT, we conducted a SWOT (strengths, weaknesses, opportunities, and threats) analysis in this study with the 36 JANIT Forum members (16 physicians and 20 company representatives). Based on this SWOT analysis, the JANIT Forum identified currently available NITs able to accurately select NAFLD patients at high risk of NASH for HCC surveillance/therapeutic intervention and evaluate the effectiveness of therapeutic interventions.

MR elastography in nonalcoholic fatty liver disease: inter-center and inter-analysis-method measurement reproducibility and accuracy at 3T

OBJECTIVES

To assess reproducibility and fibrosis classification accuracy of magnetic resonance elastography (MRE)-determined liver stiffness measured manually at two different centers, and by automated analysis software in adults with nonalcoholic fatty liver disease (NAFLD), using histopathology as a reference standard.

METHODS

This retrospective, cross-sectional study included 91 adults with NAFLD who underwent liver MRE and biopsy. MRE-determined liver stiffness was measured independently for this analysis by an image analyst at each of two centers using standardized manual analysis methodology, and separately by an automated analysis. Reproducibility was assessed pairwise by intraclass correlation coefficient (ICC) and Bland-Altman analysis. Diagnostic accuracy was assessed by receiver operating characteristic (ROC) analyses.

RESULTS

ICC of liver stiffness measurements was 0.95 (95% CI: 0.93, 0.97) between center 1 and center 2 analysts, 0.96 (95% CI: 0.94, 0.97) between the center 1 analyst and automated analysis, and 0.94 (95% CI: 0.91, 0.96) between the center 2 analyst and automated analysis. Mean bias and 95% limits of agreement were 0.06 ± 0.38 kPa between center 1 and center 2 analysts, 0.05 ± 0.32 kPa between the center 1 analyst and automated analysis, and 0.11 ± 0.41 kPa between the center 2 analyst and automated analysis. The area under the ROC curves for the center 1 analyst, center 2 analyst, and automated analysis were 0.834, 0.833, and 0.847 for distinguishing fibrosis stage 0 vs. ≥ 1, and 0.939, 0.947, and 0.940 for distinguishing fibrosis stage ≤ 2 vs. ≥ 3.

CONCLUSION

MRE-determined liver stiffness can be measured with high reproducibility and fibrosis classification accuracy at different centers and by an automated analysis.

KEY POINTS

• Reproducibility of MRE liver stiffness measurements in adults with nonalcoholic fatty liver disease is high between two experienced centers and between manual and automated analysis methods. • Analysts at two centers had similar high diagnostic accuracy for distinguishing dichotomized fibrosis stages. • Automated analysis provides similar diagnostic accuracy as manual analysis for advanced fibrosis.

Comparative Performance of Quantitative and Qualitative Magnetic Resonance Imaging Metrics in Primary Sclerosing Cholangitis

Background and Aims

Several quantitative and qualitative magnetic resonance imaging (MRI) metrics have been reported to predict outcomes among those with primary sclerosing cholangitis (PSC). We aimed to compare the reproducibility and prognostic performances of MRI biomarkers and examine if combining these measurements adds value.

Methods

We performed a retrospective review of 388 patients with PSC who underwent a magnetic resonance elastography and magnetic resonance cholangiopancreatography. Liver stiffness (LS) was determined by validated automated software, whereas spleen volume was calculated by semiautomated software, and radiologists manually determined the ANALI scores. The primary endpoint was hepatic decompensation.

Results

LS and spleen volume values had perfect and near-perfect agreement (intraclass correlation coefficient of 1.00 and 0.9996, respectively), whereas ANALI with and without gadolinium had a moderate inter-rater agreement between 3 radiologists (kappa = 0.42-0.54 and 0.46-0.57, respectively). As a continuous variable, LS alone was the best predictor of hepatic decompensation (concordance score = 0.90; 95% confidence interval, 0.87-0.93). A quantitative-only MRI model [LS (>4.70 kPa = 2 or ≤4.70 kPa = 0) + spleen volume (>600 mm3 = 1 or ≤600 mm3 = 0)] had the optimal reproducibility and performance (concordance score = 0.85; 95% confidence interval = 0.80-0.89) and enabled patient risk stratification by estimating the 5-year incidence of hepatic decompensation: 7.49%, 44.50%, 70.00%, and 91.30% (score 0-3).

Conclusion

Quantitative MRI markers of fibrosis and portal hypertension generated by automated and semiautomated software are highly reproducible. LS is the single best imaging predictor of hepatic decompensation. However, a quantitative MRI score using LS and spleen volume is well suited to risk stratify those with PSC.

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.

Diagnostic value of magnetic resonance parametric mapping for non-invasive assessment of liver fibrosis in patients with primary sclerosing cholangitis

Background

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease, characterized by bile duct inflammation and destruction, leading to biliary fibrosis and cirrhosis. The purpose of this study was to investigate the utility of T1 and T2 mapping parameters, including extracellular volume fraction (ECV) for non-invasive assessment of fibrosis severity in patients with PSC.

Methods

In this prospective study, patients with PSC diagnosis were consecutively enrolled from January 2019 to July 2020 and underwent liver MRI. Besides morphological sequences, MR elastography (MRE), and T1 and T2 mapping were performed. ECV was calculated from T1 relaxation times. The presence of significant fibrosis (≥ F2) was defined as MRE-derived liver stiffness ≥ 3.66 kPa and used as the reference standard, against which the diagnostic performance of MRI mapping parameters was tested. Student t test, ROC analysis and Pearson correlation were used for statistical analysis.

Results

32 patients with PSC (age range 19–77 years) were analyzed. Both, hepatic native T1 (r = 0.66; P < 0.001) and ECV (r = 0.69; P < 0.001) correlated with MRE-derived liver stiffness. To diagnose significant fibrosis (≥ F2), ECV revealed a sensitivity of 84.2% (95% confidence interval (CI) 62.4–94.5%) and a specificity of 84.6% (CI 57.8–95.7%); hepatic native T1 revealed a sensitivity of 52.6% (CI 31.7–72.7%) and a specificity of 100.0% (CI 77.2–100.0%). Hepatic ECV (area under the curve (AUC) 0.858) and native T1 (AUC 0.711) had an equal or higher diagnostic performance for the assessment of significant fibrosis compared to serologic fibrosis scores (APRI (AUC 0.787), FIB-4 (AUC 0.588), AAR (0.570)).

Conclusions

Hepatic T1 and ECV can diagnose significant fibrosis in patients with PSC. Quantitative mapping has the potential to be a new non-invasive biomarker for liver fibrosis assessment and quantification in PSC patients.

Elastography in the evaluation of liver allograft

Elastography is an established technique in the evaluation of chronic liver diseases. While there is a large clinical experience and data available regarding the performance of elastography in native liver, elastography experience with liver grafts is limited and still growing. Both ultrasound-based elastography techniques and MR Elastography (MRE) are useful in the assessment of liver fibrosis in liver transplants. Technical modifications for performing elastography will be required for optimum evaluation of the graft. In general, caution needs to be exercised regarding the use of elastography immediately following transplantation as post-operative changes, perioperative conditions/complications, inflammation, and rejection can cause increased stiffness in the graft. In the follow-up, detection of increased stiffness with elastography is useful for predicting development of fibrosis in the graft. Adjunctive MRI or ultrasound with Doppler also provides comprehensive evaluation of anatomy, vascular anastomosis and patency, biliary tree, and stiffness for fibrosis. In this review, we provide a brief overview of elastography techniques available followed by the literature review of elastography in the evaluation of grafts and illustration with clinical examples.

Magnetic resonance imaging features of small-duct primary sclerosing cholangitis

PURPOSE

To evaluate the biliary tree and hepatic parenchymal findings on magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) in small-duct primary sclerosing cholangitis (SD-PSC).

METHODS

Thirty-nine patients with biopsy-proven primary sclerosing cholangitis (PSC) without any bile duct abnormality on MRCP (n = 15) or ERCP (n = 24) at the time of diagnosis were identified. Follow-up MRCP was available in 36/39 patients (12/15 Baseline MRCP group and 24 Baseline ERCP group). Two radiologists in consensus assessed the MRI/MRCP findings. The baseline MRI/MRCP of 15 SD-PSC patients was compared with MRI/MRCP of 15 normal healthy potential liver donors (Control group). Comparisons were made between SD-PSC patients and the Control group, and between baseline and follow-up MRI/MRCP findings in the SD-PSC patients.

RESULTS

In the 15 Baseline MRCP SD-PSC subjects, the biliary tree was normal with a trend of larger bile ducts compared to the Control group. Periductal enhancement (arterial phase: 70%, 7/10; delayed phase: 90%, 9/10), heterogeneous parenchymal signal on T2-weighted (53%, 8/15) and post contrast-enhanced images (70%, 7/10), and enlarged periportal lymph nodes (73%, 11/15) were frequently present in patients with SD-PSC. Eight (33%) of 24 SD-PSC patients who had normal MRCP at baseline MRCP or initial follow-up MRCP after normal baseline ERCP showed large-duct PSC (LD-PSC) features on follow-up and the 10-year cumulative incidence for progression to LD-PSC rate was 8.5%.

CONCLUSION

SD-PSC patients have a normal biliary tree but frequently have peribiliary enhancement, abnormal parenchymal signal intensity, and periportal lymphadenopathy. One-third shows progression to LD-PSC on follow-up.