Magnetic resonance elastography (MRE) in assessing hepatic fibrosis: performance in a cohort of patients with histological data

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.

Diagnostic accuracy of magnetic resonance elastography and point-shear wave elastography for significant hepatic fibrosis screening: Systematic review and meta-analysis

The hepatic diseases are extremely common in clinical practice. The correct classification of liver fibrosis is extremely important, as it influences therapy and predicts disease outcomes. The purpose of this study is to compare the diagnostic performance of point-shear wave elastography (pSWE) and magnetic resonance elastography (MRE) in the hepatic fibrosis diagnostic. A meta-analysis was carried out based on articles published until October 2020. The articles are available at following databases: MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Scientific Electronic Library Online, LILACS, Scopus, and CINAHL. Diagnostic performances were analyzed per METAVIR F2, using 3.5kPa as target fibrosis. Assessment of the methodological quality of the incorporated papers by the QUADAS-2 tool for pSWE and MRE. A total 2,153 studies articles were evaluated and 44 studies, comprising 6,081 patients with individual data, were included in the meta-analysis: 28 studies for pSWE and 16 studies for MRE. The pooled sensitivity and specificity were 0.86 (95%CI 0.80-0.90) and 0.88 (95%CI 0.85-0.91), respectively, for pSWE, compared with 0.94 (95%CI 0.89-0.97) and 0.95 (95%CI 0.89-0.98) respectively, for MRE. The pooled SROC curve for pSWE shows in the area under the curve (AUC) of 0.93 (95%CI 0.90-0.95), whereas the AUC for MRE was 0.98 (95%CI 0.96-0.99). The diagnostic odds ratio for pSWE and MRE were 41 (95%CI 24-72) and 293 (95%CI 86-1000), respectively. There was statistically significant heterogeneity for pSWE sensitivity (I² = 85.26, P<0.001) and specificity (I² = 89.46, P<0.001). The heterogeneity for MRE also was significant for sensitivity (I² = 73.28, P<0.001) and specificity (I² = 87.24, P<0.001). Therefore, both pSWE and MRE are suitable modalities for assessing liver fibrosis. In addition, MRE is a more accurate imaging technique than pSWE and can be used as alternative to invasive biopsy.

Diagnostic Performance of Spin-Echo Echo-Planar Imaging Magnetic Resonance Elastography in 3T System for Noninvasive Assessment of Hepatic Fibrosis

Objective

To validate the performance of 3T spin-echo echo-planar imaging (SE-EPI) magnetic resonance elastography (MRE) for staging hepatic fibrosis in a large population, using surgical specimens as the reference standard.

Materials and Methods

This retrospective study initially included 310 adults (155 undergoing hepatic resection and 155 undergoing donor hepatectomy) with histopathologic results from surgical liver specimens. They underwent 3T SE-EPI MRE ≤ 3 months prior to surgery. Demographic findings, underlying liver disease, and hepatic fibrosis pathologic stage according to METAVIR were recorded. Liver stiffness (LS) was measured by two radiologists, and inter-reader reproducibility was evaluated using the intraclass correlation coefficient (ICC). The mean LS of each fibrosis stage (F0–F4) was calculated in total and for each etiologic subgroup. Comparisons among subgroups were performed using the Kruskal–Wallis test and Conover post-hoc test. The cutoff values for fibrosis staging were estimated using receiver operating characteristic (ROC) curve analysis.

Results

Inter-reader reproducibility was excellent (ICC, 0.98; 95% confidence interval, 0.97–0.99). The mean LS values were 1.91, 2.41, 3.24, and 5.41 kPa in F0–F1 (n = 171), F2 (n = 26), F3 (n = 38), and F4 (n = 72), respectively. The discriminating cutoff values for diagnosing ≥ F2, ≥ F3, and F4 were 2.18, 2.71, and 3.15 kPa, respectively, with the ROC curve areas of 0.97–0.98 (sensitivity 91.2%–95.9%, specificity 90.7%–99.0%). The mean LS was significantly higher in patients with cirrhosis (F4) of nonviral causes, such as primary biliary cirrhosis (9.56 kPa) and alcoholic liver disease (7.17 kPa) than in those with hepatitis B or C cirrhosis (4.28 and 4.92 kPa, respectively). There were no statistically significant differences in LS among the different etiologic subgroups in the F0–F3 stages.

Conclusion

The 3T SE-EPI MRE demonstrated high interobserver reproducibility, and our criteria for staging hepatic fibrosis showed high diagnostic performance. LS was significantly higher in patients with non-viral cirrhosis than in those with viral cirrhosis.

Evaluation of Rabbits Liver Fibrosis Using Gd-DTPA-BMA of Dynamic Contrast-Enhanced Magnetic Resonance Imaging

Objective

To evaluate the different pharmacokinetic parameters of the DCE-MRI method on diagnosing and staging of rabbits' liver fibrosis.

Methods

We had performed DCE-MRI for rabbits that had been divided into the experiment group and the control group. Then, rabbits' images were transferred to a work station to get three parameters such as K _trans, K _ep, and V _e, which had been measured to calculate. After data were analyzed, ROC analyses were performed to assess the diagnostic performance of K _trans, K _ep, and V _e to judge liver fibrosis.

Results

The distribution of the different liver fibrosis group was as follows: F1, n = 8; F2, n = 9; F3, n = 6; F4, n = 5. No fibrosis was deemed as F0, n = 6. K _ep is statistically significant (P < 0.05) for F0 and mild liver fibrosis stage, and the K _ep shows AUC of 0.814. Three parameters are statistically significant for F0 and advanced liver fibrosis stage (K _trans and K _ep, P < 0.01; V _e, P < 0.05), and the K _trans shows AUC of 0.924; the K _ep shows AUC of 0.909; the V _e shows AUC of 0.848; K _trans and K _ep are statistically significant for mild and advanced liver fibrosis stages (K _trans, P < 0.01; K _ep, P < 0.05), and the K _trans shows AUC of 0.840; the K _ep shows AUC of 0.765. Both K _trans and K _ep are negatively correlated with the liver fibrosis stage. V _e is positively correlated with the liver fibrosis stage.

Conclusion

K _trans is shown to be the best DCE parameter to distinguish the fibrotic liver from the normal liver and mild and advanced fibrosis. On the contrary, K _ep is moderate and V _e is worst. And K _ep is a good DCE parameter to differentiate mild fibrosis from the normal liver.

Comparison of diffusion-weighted imaging and MR elastography in staging liver fibrosis: a meta-analysis

PURPOSE

To compare the diagnostic performance of diffusion-weighted imaging (DWI), gradient-recalled echo-based magnetic resonance elastography (GRE-MRE), and spin-echo echo-planar imaging-based MRE (SE-EPI-MRE) in liver fibrosis staging.

METHODS

A systematic literature search was done to collect studies on the performance of DWI, GRE-MRE, and SE-EPI-MRE for diagnosing liver fibrosis. Pooled sensitivity, specificity, diagnostic odds ratio, positive and negative likelihood ratio, and a summary receiver operating characteristic (ROC) curve were estimated with a bivariate random effects model. Subgroup analyses on various study characteristics were performed.

RESULTS

Sixty studies with a total of 6620 patients were included in the meta-analysis. Pooled sensitivity and specificity of GRE-MRE and SE-EPI-MRE showed high diagnostic accuracy and did not differ significantly. The area under the summary ROC curve for all stages of fibrosis differed significantly between DWI (0.83-0.88) and either GRE-MRE (0.95-0.97) or SE-EPI-MRE (0.95-0.99). Substantial heterogeneity was detected for all three imaging methods.

CONCLUSIONS

Both GRE-MRE and SE-EPI-MRE are highly accurate for detection of each liver fibrosis stage, with high potential to replace liver biopsy. Although DWI had a moderate accuracy in distinguishing liver fibrosis, it could be regarded as an alternative to MRE, since it is widely available and easily implemented in routine liver MRI.

Effect of breath holding at the end of the inspiration and expiration phases on liver stiffness measured by 2D-MR elastography

PURPOSE

Evaluate the effect of breath holding at the end of the inspiration and expiration phases on the measurement of liver stiffness by 2D-MR elastography (MRE).

METHODS

The study included 61 subjects, of which 31 subjects were pathologically confirmed liver fibrosis patients [liver fibrosis group (LFG)] and 30 healthy subjects [healthy group (HG)]. MRE was used to measure the liver stiffness of subjects in inspiration breath-hold (IBH) and expiration breath-hold (EBH) states.

RESULTS

In IBH and EBH states, the liver stiffness measured by MRE was not significantly different in the HG (P = 0.125, > 0.05), while the LFG showed a significant difference (P <0.001). Also, a significant difference was observed between the change values in the mild/moderate fibrosis group (MFG) and advanced fibrosis group (AFG) (P = 0.005, < 0.05).

CONCLUSIONS

The liver stiffness values in patients with liver fibrosis were affected by breath-holding states. The higher the stage of liver fibrosis, the greater the change in liver stiffness values, but no significant difference was observed between liver stiffness values in healthy subjects under the two breath-holding conditions. Different breath-holding states are factors influencing liver fibrosis stiffness measured by MRE, which should be given due attention in both clinical and research contexts.

Reproducibility of hepatic MR elastography across field strengths, pulse sequences, scan intervals, and readers

PURPOSE

To evaluate the reproducibility of hepatic MRE under various combinations of settings of field strength, pulse sequence, scan interval, and reader in non-alcoholic fatty liver disease (NAFLD) patients.

METHODS

Adult NAFLD patients were prospectively enrolled for serial hepatic MRE with 1.5 T using 2D GRE sequence and 3.0 T using 2D SE-EPI sequence on the same day and after 2 weeks, resulting a total of four MRE examinations per patient. Three readers with various levels of background knowledge in MRE technique and liver anatomy measured liver stiffness after a training session. Linear regression, Bland-Altman analysis, within-subject coefficient of variation, and reproducibility coefficient (RDC) were used to determine reproducibility of hepatic MRE measurement.

RESULTS

Twenty patients completed the MRE sessions. Liver stiffness through MRE showed pooled RDC of 26% (upper 95% CI 30.6%) and corresponding limits of agreement (LOA) within 0.55 kPa across field strengths, MRE sequences, and 2-week interscan interval in three readers. Small mean biases and narrow LOA were observed among readers (0.05-0.19 kPa ± 0.53).

CONCLUSION

The magnitude of change across combinations of scan parameters is within acceptable clinical range, rendering liver stiffness through MRE a reproducible quantitative imaging biomarker. A lower reproducibility was observed for measurements under different field strengths/MRE sequences at a longer (2 weeks) interscan interval. Operators should be trained to acquire region of interest consistently in repeat examinations.

Imaging fibrosis in inflammatory diseases: targeting the exposed extracellular matrix

In a variety of diseases, from benign to life-threatening ones, inflammation plays a major role. Monitoring the intensity and extent of a multifaceted inflammatory process has become a cornerstone in diagnostics and therapy monitoring. However, the current tools lack the ability to provide insight into one of its most crucial aspects, namely, the alteration of the extracellular matrix (ECM). Using a radiolabeled platelet glycoprotein VI-based ECM-targeting fusion protein (GPVI-Fc), we investigated how binding of GPVI-Fc on fibrous tissue could uncover the progression of several inflammatory disease models at different stages (rheumatoid arthritis, cutaneous delayed-type hypersensitivity, lung inflammation and experimental autoimmune encephalomyelitis). Methods: The fusion protein GPVI-Fc was covalently linked to 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) and subsequently labeled with 64Cu. We analyzed noninvasively in vivo64Cu-GPVI-Fc accumulation in murine cutaneous delayed-type hypersensitivity, anti-glucose-6-phosphate isomerase serum-induced rheumatoid arthritis, lipopolysaccharide-induced lung inflammation and an experimental autoimmune encephalomyelitis model. Static and dynamic Positron Emission Tomography (PET) of the radiotracer distribution was performed in vivo, with ex vivo autoradiography confirmation, yielding quantitative accumulation and a distribution map of 64Cu-GPVI-Fc. Ex vivo tissue histological staining was performed on harvested samples to highlight the fusion protein binding to collagen I, II and III, fibronectin and fibrinogen as well as the morphology of excised tissue. Results:64Cu-GPVI-Fc showed a several-fold increased uptake in inflamed tissue compared to control tissue, particularly in the RA model, with a peak 24 h after radiotracer injection of up to half the injected dose. Blocking and isotype control experiments indicated a target-driven accumulation of the radiotracer in the case of chronic inflammation. Histological analysis confirmed a prolonged accumulation at the inflammation site, with a pronounced colocalization with the different components of the ECM (collagen III and fibronectin notably). Binding of the fusion protein appeared to be specific to the ECM but unspecific to particular components. Conclusion: Imaging of 64Cu-GPVI-Fc accumulation in the ECM matrix appears to be a promising candidate for monitoring chronic inflammation. By binding to exposed fibrous tissue (collagen, fibronectin, etc.) after extravasation, a new insight is provided into the fibrotic events resulting from a prolonged inflammatory state.

Predicting gastroesophageal varices through spleen magnetic resonance elastography in pediatric liver fibrosis

BACKGROUND

A recent retrospective study confirmed that hepatic stiffness and splenic stiffness measured with magnetic resonance elastography (MRE) are strongly associated with the presence of esophageal varices. In addition, strong correlations have been reported between splenic stiffness values measured with MRE and hepatic venous pressure gradients in animal models. However, most studies have been conducted on adult populations, and previous pediatric MRE studies have only demonstrated the feasibility of MRE in pediatric populations, while the actual clinical application of spleen MRE has been limited.

AIM

To assess the utility of splenic stiffness measurements by MRE to predict gastroesophageal varices in children.

METHODS

We retrospectively reviewed abdominal MRE images taken on a 3T system in pediatric patients. Patients who had undergone Kasai operations for biliary atresia were selected for the Kasai group, and patients with normal livers and spleens were selected for the control group. Two-dimensional spin-echo echo-planar MRE acquisition centered on the liver, with a pneumatic driver at 60 Hz and a low amplitude, was performed to obtain hepatic and splenic stiffness values. Laboratory results for aspartate aminotransferase to platelet ratio index (APRI) were evaluated within six months of MRE, and the normalized spleen size ratio was determined with the upper normal size limit. All Kasai group patients underwent gastroesophageal endoscopy during routine follow-up. The Mann-Whitney U test, Kendall's tau b correlation and diagnostic performance analysis using the area under the curve (AUC) were performed for statistical analysis.

RESULTS

The median spleen MRE value was 5.5 kPa in the control group (n = 9, age 9-18 years, range 4.7-6.4 kPa) and 8.6 kPa in the Kasai group (n = 22, age 4-18 years, range 5.0-17.8 kPa). In the Kasai group, the APRI, spleen size ratio and spleen MRE values were higher in patients with portal hypertension (n = 11) than in patients without (n = 11) (all P < 0.001) and in patients with gastroesophageal varices (n = 6) than in patients without (n = 16) (all P < 0.05), even though their liver MRE values were not different. The APRI (τ = 0.477, P = 0.007), spleen size ratio (τ = 0.401, P = 0.024) and spleen MRE values (τ = 0.426, P = 0.016) also correlated with varices grades. The AUC in predicting gastroesophageal varices was 0.844 at a cut-off of 0.65 (100% sensitivity and 75% specificity) for the APRI, and 0.844 at a cut-off of 9.9 kPa (83.3% sensitivity and 81.3% specificity) for spleen MRE values.

CONCLUSION

At a cut-off of 9.9 kPa, spleen MRE values predicted gastroesophageal varices as well as the APRI and spleen size ratio in biliary atresia patients after the Kasai operation. However, liver MRE values were not useful for this purpose.

Magnetic resonance elastography of liver and spleen: Methods and applications

The viscoelastic properties of the liver and spleen can be assessed with magnetic resonance elastography (MRE). Several actuators, MRI acquisition sequences and reconstruction algorithms have been proposed for this purpose. Reproducible results are obtained, especially when the examination is performed in standard conditions with the patient fasting. Accurate staging of liver fibrosis can be obtained by measuring liver stiffness or elasticity with MRE. Moreover, emerging evidence shows that assessing the tissue viscous parameters with MRE is useful for characterizing liver inflammation, non-alcoholic steatohepatitis, hepatic congestion, portal hypertension, and hepatic tumors. Further advances such as multifrequency acquisitions and compression-sensitive MRE may provide novel quantitative markers of hepatic and splenic mechanical properties that may improve the diagnosis of hepatic and splenic diseases.

Diagnostic imaging in the management of patients with metabolic syndrome

Metabolic syndrome (MetS) is the constellation of metabolic risk factors that might foster development of type 2 diabetes and cardiovascular disease. Abdominal obesity and insulin resistance play a prominent role among all metabolic traits of MetS. Because intervention including weight loss can reduce these morbidity and mortality in MetS, early detection of the severity and complications of MetS could be useful. Recent advances in imaging modalities have provided significant insight into the development and progression of abdominal obesity and insulin resistance, as well as target organ injuries. The purpose of this review is to summarize advances in diagnostic imaging modalities in MetS that can be applied for evaluating each components and target organs. This may help in early detection, monitoring target organ injury, and in turn developing novel therapeutic target to alleviate and avert them.

Diagnostic Performance of MR Elastography for Liver Fibrosis in Children and Young Adults with a Spectrum of Liver Diseases

Purpose To assess the diagnostic performance of magnetic resonance (MR) elastography-derived liver stiffness to detect liver fibrosis in a pediatric and young adult population with a spectrum of liver diseases. Materials and Methods This retrospective study included patients younger than 21 years of age who underwent MR elastography and liver biopsy within 3 months of one another between January 2012 and September 2016 for indications other than liver transplantation or Fontan palliation of congenital heart disease. MR elastography examinations were reprocessed by a single observer, blinded to pathologic findings. Pathology specimens were reviewed by a single pathologist who scored steatosis (lipid in ≥ 5% of hepatocytes) and staged fibrosis. Receiver operating characteristic (ROC) curves were used to assess diagnostic performance. Results A total of 86 patients, 49 (57%) male with a median age of 14.2 years (range, 0.3-20.6 years), were included. Fifty-one patients (59.3%) had Ludwig stage 2 or higher fibrosis; 44 patients (51.2%) had hepatic steatosis. The area under the ROC curve for Ludwig stage 0-1 versus stage 2 or higher fibrosis was 0.70 (95% confidence interval [CI]: 0.59, 0.81) for the whole population and was significantly lower for patients with steatosis versus those without (0.53 [95% CI: 0.35, 0.71] vs 0.82 [95% CI: 0.67, 0.96], P = .014). Optimal stiffness cut-offs for the entire population were 2.27 kPa with 68.6% sensitivity (95% CI: 57.2%, 80.1%) and 74.3% specificity (95% CI: 63.5%, 85.1%) or 1.67 kPa with 35.3% sensitivity (95% CI: 23.5%, 47.1%) and 91.4% specificity (95% CI: 84.5%, 98.3%). Conclusion In children and young adults, MR elastography performs significantly better for distinguishing stage 0-1 versus stage 2 or higher fibrosis in patients without steatosis than in those with steatosis. This suggests a confounding effect of steatosis or inflammation in the population with nonalcoholic fatty liver disease. ^© RSNA, 2018.

Progress in non-invasive detection of liver fibrosis

Liver fibrosis is an important pathological precondition for hepatocellular carcinoma. The degree of hepatic fibrosis is positively correlated with liver cancer. Liver fibrosis is a series of pathological and physiological process related to liver cell necrosis and degeneration after chronic liver injury, which finally leads to extracellular matrix and collagen deposition. The early detection and precise staging of fibrosis and cirrhosis are very important for early diagnosis and timely initiation of appropriate therapeutic regimens. The risk of severe liver fibrosis finally progressing to liver carcinoma is >50%. It is known that biopsy is the gold standard for the diagnosis and staging of liver fibrosis. However, this method has some limitations, such as the potential for pain, sampling variability, and low patient acceptance. Furthermore, the necessity of obtaining a tissue diagnosis of liver fibrosis still remains controversial. An increasing number of reliable non-invasive approaches are now available that are widely applied in clinical practice, mostly in cases of viral hepatitis, resulting in a significantly decreased need for liver biopsy. In fact, the non-invasive detection and evaluation of liver cirrhosis now has good accuracy due to current serum markers, ultrasound imaging, and magnetic resonance imaging quantification techniques. A prominent advantage of the non-invasive detection and assessment of liver fibrosis is that liver fibrosis can be monitored repeatedly and easily in the same patient. Serum biomarkers have the advantages of high applicability (>95%) and good reproducibility. However, their results can be influenced by different patient conditions because none of these markers are liver-specific. The most promising techniques appear to be transient elastography and magnetic resonance elastography because they provide reliable results for the detection of fibrosis in the advanced stages, and future developments promise to increase the reliability and accuracy of the staging of hepatic fibrosis. This article aims to describe the recent progress in the development of non-invasive assessment methods for the staging of liver fibrosis, with a special emphasize on computer-aided quantitative and deep learning methods.

Prospective Comparison of the Diagnostic Performance of Magnetic Resonance Elastography with Acoustic Radiation Force Impulse Elastography for Pre-operative Staging of Hepatic Fibrosis in Patients with Hepatocellular Carcinoma

The purpose of this study was to compare the diagnostic accuracy of magnetic resonance (MR) elastography with that of acoustic radiation force impulse (ARFI) elastography for pre-operative staging of hepatic fibrosis in patients with hepatocellular carcinoma. We prospectively enrolled 77 patients who were scheduled to undergo hepatectomy for hepatocellular carcinoma. Pre-operative MRE and ARFI elastography examinations were performed on the same day, and liver stiffness/velocity values were determined. Fibrosis stage and necro-inflammatory activity of resected specimens were determined histopathologically using the METAVIR scoring system. Correlations between MRE and ARFI elastography findings and histologic findings were determined by receiver operating characteristic (ROC) analysis. Correlation of MRE was excellent and correlation of ARFI elastography was good with fibrosis stage. MRE had better diagnostic performance than ARFI elastography in estimating substantial fibrosis (F2), severe fibrosis (F3) and cirrhosis (F4). The optimal cutoff value and the area under the ROC curve (AUROC) were determined using ROC curve analysis. The highest Youden index was used as a criterion for selecting the optimal cutoff value. ROC analysis revealed that MRE discriminated advanced stages of fibrosis (F ≥ 2) well in patients with hepatocellular carcinoma at a cutoff value of 3.0 kPa with an AUROC value of 0.93, and ARFI elastography did so at a cutoff value of 1.77 m/s with an AUROC value of 0.81 for predicting advanced stages of fibrosis (F ≥ 2). In conclusion, MRE is a more accurate imaging modality than ARFI elastography in estimating advanced stages of fibrosis and cirrhosis.

A prediction model for the grade of liver fibrosis using magnetic resonance elastography

BACKGROUND

Liver stiffness measurement (LSM) has recently become available for assessment of liver fibrosis. We aimed to develop a prediction model for liver fibrosis using clinical variables, including LSM.

METHODS

We performed a prospective study to compare liver fibrosis grade with fibrosis score. LSM was measured using magnetic resonance elastography in 184 patients that underwent liver resection, and liver fibrosis grade was diagnosed histologically after surgery. Using the prediction model established in the training group, we validated the classification accuracy in the independent test group.

RESULTS

First, we determined a cut-off value for stratifying fibrosis grade using LSM in 122 patients in the training group, and correctly diagnosed fibrosis grades of 62 patients in the test group with a total accuracy of 69.3%. Next, on least absolute shrinkage and selection operator analysis in the training group, LSM (r = 0.687, P < 0.001), indocyanine green clearance rate at 15 min (ICGR15) (r = 0.527, P < 0.001), platelet count (r = -0.537, P < 0.001) were selected as variables for the liver fibrosis prediction model. This prediction model applied to the test group correctly diagnosed 32 of 36 (88.8%) Grade I (F0 and F1) patients, 13 of 18 (72.2%) Grade II (F2 and F3) patients, and 7 of 8 (87.5%) Grade III (F4) patients in the test group, with a total accuracy of 83.8%.

CONCLUSIONS

The prediction model based on LSM, ICGR15, and platelet count can accurately and reproducibly predict liver fibrosis grade.

Comparison of gradient-recalled echo and spin-echo echo-planar imaging MR elastography in staging liver fibrosis: a meta-analysis

OBJECTIVES

To compare the diagnostic performance of gradient-recalled echo-based magnetic resonance elastography (GRE-MRE) and spin-echo echo-planar imaging-based MRE (SE-EPI-MRE) in liver fibrosis staging.

METHODS

A systematic literature search was performed to identify studies involving the performance of MRE for the diagnosis of liver fibrosis. Pooled sensitivity, specificity, positive and negative likelihood ratios, the diagnostic odds ratio, and a summary receiver operating characteristic (ROC) curve were estimated by using a bivariate random effects model. Subgroup analyses were performed between different study characteristics.

RESULTS

Twenty-six studies with a total of 3,200 patients were included in the meta-analysis. Pooled sensitivity and specificity of GRE-MRE and SE-EPI-MRE did not differ significantly. The area under the summary ROC curve for stage diagnosis of any (F ≥ 1), significant (F ≥ 2), advanced (F ≥ 3), and cirrhosis (F = 4) on GRE-MRE and SE-EPI-MRE were 0.93 versus 0.94, 0.95 versus 0.94, 0.94 versus 0.95, and 0.92 versus 0.93, respectively. Substantial heterogeneity was detected for both sequences.

CONCLUSION

Both GRE and SE-EPI-MRE show high sensitivity and specificity for detection of each stage of liver fibrosis, without significant differences. Magnetic resonance elastography (MRE) may be useful for noninvasive evaluation of liver fibrosis in chronic liver disease.

KEY POINTS

• Pooled sensitivity and specificity of GRE-MRE and SE-EPI-MRE did not differ significantly. • GRE-MRE and SE-EPI-MRE were highly accurate for detecting all stages of fibrosis. • Due to better agreement and repeatability, GRE-MRE should be used first. • In case of failure on GRE-MRE, SE-EPI-MRE should be used.

MR elastography is effective for the non-invasive evaluation of fibrosis and necroinflammatory activity in patients with nonalcoholic fatty liver disease

OBJECTIVES

To evaluate the performance of magnetic resonance elastography (MRE) in diagnosing and staging hepatic fibrosis in patients with histologically confirmed nonalcoholic fatty liver disease (NAFLD) and in distinguishing simple steatosis from nonalcoholic steatohepatitis (NASH).

METHODS

Ninety subjects (49 NAFLD patients and 41 healthy volunteers) were prospectively enrolled. Liver stiffness measured by MRE was correlated with the grade of fibrosis and/or inflammation determined by liver biopsy. Correlations, ROC (receiver operator characteristic) curves and diagnostic performance were evaluated. The study was approved by the local ethics committee.

RESULTS

The area under the ROC curve (AUROC) of MRE in discriminating healthy from NAFLD individuals was 0.964 (P<0.0001), and that for distinguishing advanced (F3-F4) from absent/mild fibrosis (F0-F2) was 0.928 (P<0.0001). The use of a threshold >4.39 kPa resulted in a sensitivity of 90.9% and a specificity of 97.3% for diagnosing advanced fibrosis. For discriminating NASH from simple steatosis, the AUROC was 0.783 (P<0.0001), and the threshold, 3.22 kPa.

CONCLUSIONS

MRE is an effective, non-invasive method for detecting/staging hepatic fibrosis in NAFLD. This method has good performance in discriminating normal from NAFLD subjects and between the extreme grades of fibrosis. NAFLD patients with inflammation and without fibrosis have higher liver stiffness than those with simple steatosis.

Magnetic resonance elastography is as accurate as liver biopsy for liver fibrosis staging

BACKGROUND

Liver MR elastography (MRE) is available for the noninvasive assessment of liver fibrosis; however, no previous studies have compared the diagnostic ability of MRE with that of liver biopsy.

PURPOSE

To compare the diagnostic accuracy of liver fibrosis staging between MRE-based methods and liver biopsy using the resected liver specimens as the reference standard.

STUDY TYPE

A retrospective study at a single institution.

POPULATION

In all, 200 patients who underwent preoperative MRE and subsequent surgical liver resection were included in this study. Data from 80 patients were used to estimate cutoff and distributions of liver stiffness values measured by MRE for each liver fibrosis stage (F0-F4, METAVIR system). In the remaining 120 patients, liver biopsy specimens were obtained from the resected liver tissues using a standard biopsy needle.

FIELD STRENGTH/SEQUENCE

2D liver MRE with gradient-echo based sequence on a 1.5 or 3T scanner was used.

ASSESSMENT

Two radiologists independently measured the liver stiffness value on MRE and two types of MRE-based methods (threshold and Bayesian prediction method) were applied. Two pathologists evaluated all biopsy samples independently to stage liver fibrosis. Surgically resected whole tissue specimens were used as the reference standard.

STATISTICAL TESTS

The accuracy for liver fibrosis staging was compared between liver biopsy and MRE-based methods with a modified McNemar's test.

RESULTS

Accurate fibrosis staging was achieved in 53.3% (64/120) and 59.1% (71/120) of patients using MRE with threshold and Bayesian methods, respectively, and in 51.6% (62/120) with liver biopsy. Accuracies of MRE-based methods for diagnoses of ≥F2 (90-91% [108-9/120]), ≥F3 (79-81% [95-97/120]), and F4 (82-85% [98-102/120]) were statistically equivalent to those of liver biopsy (≥F2, 79% [95/120], P ≤ 0.01; ≥F3, 88% [105/120], P ≤ 0.006; and F4, 82% [99/120], P ≤ 0.017).

DATA CONCLUSION

MRE can be an alternative to liver biopsy for fibrosis staging.

LEVEL OF EVIDENCE

3. Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1268-1275.

Predicting postoperative outcomes of liver resection by magnetic resonance elastography

BACKGROUND

Cirrhosis is associated with blood loss during liver resection and postoperative complications. The liver stiffness measurement has recently become available for assessment of liver fibrosis.

METHODS

This prospective study was performed to predict postoperative outcomes of liver resection. The liver stiffness measurement was measured prospectively using magnetic resonance elastography for patients who had undergone liver resection for malignancy. We investigated whether the liver stiffness measurement by magnetic resonance elastography is correlated with liver fibrosis and postoperative outcomes.

RESULTS

The median liver stiffness measurement by magnetic resonance elastography in 175 patients was 3.4 (range: 1.5-11.3) kPa, and the pathologic grade of liver fibrosis was significantly correlated with the liver stiffness measurement (r = 0.68, P < .001). The median blood loss during transection per unit area was 4.1 mL/cm² (range: 0.1-37.0 mL/cm²), and the frequency of major complications was 16.0%. The liver stiffness measurement was the only independent prognostic factor for both blood loss (regression coefficient: 1.14, 95% confidence interval: 0.45-1.83, P = .001) and major complications (odds ratio: 2.14, 95% confidence interval: 1.63-2.93, P < .001). Receiver operating characteristic curve analysis indicated a significant correlation between the liver stiffness measurement and major complications with calculated area under the curve of 0.81 (P < .001), and the sensitivity and specificity for prediction of major complications (cutoff value: 5.3 kPa) were 64.3% and 87.8%, respectively. On the other hand, the amount of blood loss was significantly correlated with the frequency of major complications (P = .003).

CONCLUSION

The liver stiffness measurement by magnetic resonance elastography could be used as a predictive marker for the risk of major complications due to blood loss during liver resection.

Comparison of spin-echo echoplanar imaging and gradient recalled echo-based MR elastography at 3 Tesla with and without gadoxetic acid administration

OBJECTIVE

To compare spin-echo echoplanar imaging (SE-EPI) and gradient recalled echo (GRE) MR elastography (MRE) at 3 T with and without gadoxetic acid administration.

METHODS

We included 84 patients who underwent MRE before and after gadoxetic acid administration, each time using SE-EPI and GRE sequences. Diagnostic performance for predicting clinical liver cirrhosis and high-risk oesophageal varices was assessed using the area under the receiver-operating characteristic curve (AUC). The relationships between T2* and success of MRE, and correlations of liver stiffness (LS) values between the two sequences or before and after gadoxetic acid administration, were investigated.

RESULTS

SE-EPI-MRE resulted in a significantly lower failure rate than GRE-MRE (1.19% vs. 10.71%, P = 0.018). Increased T2* was related to higher probability of successful LS measurement (odds ratio, 1.426; P = 0.004). The AUC of SE-EPI-MRE was comparable to that of GRE-MRE for the detection of clinical liver cirrhosis (0.938 vs. 0.948, P = 0.235) and high-risk oesophageal varices (0.839 vs. 0.752, P = 0.354). LS values were not significantly different before and after gadoxetic acid administration.

CONCLUSION

SE-EPI-MRE can substitute for GRE-MRE for the detection of clinical liver cirrhosis and high-risk oesophageal varices. SE-EPI-MRE is particularly useful in patients with iron deposition, with lower failure rates than GRE-MRE.

KEY POINTS

• LS values are comparable between SE-EPI-MRE and GRE-MRE. • Administration of gadoxetic acid does not influence LS measurement. • The failure rate of SE-EPI-MRE is significantly lower than that of GRE-MRE.

Liver Stiffness Measurements with MR Elastography: Agreement and Repeatability across Imaging Systems, Field Strengths, and Pulse Sequences

Purpose To prospectively assess agreement and repeatability of magnetic resonance (MR) elastography liver stiffness measurements across imager manufacturers, field strengths, and pulse sequences. Materials and Methods This prospective cross-sectional study was approved by the institutional review board; informed consent was obtained from all subjects. On the basis of an a priori power calculation, 24 volunteer adult subjects underwent MR elastography with four MR imaging systems (two vendors) and multiple pulse sequences (two-dimensional [2D] gradient-echo [GRE] imaging, 2D spin-echo [SE] echo-planar imaging, and three-dimensional [3D] SE echo-planar imaging). Each sequence was performed twice in each patient with each imaging system. Intraclass correlation coefficients (ICCs) were used to assess agreement and repeatability. P < .05 was considered indicative of a statistically significant difference. Results Pairwise ICCs were 0.67-0.82 and 0.62-0.83 for agreement between pulse sequences across manufacturers (n = 4) and field strengths (n = 5), respectively. ICCs were 0.45-0.90 for pairwise agreement between sequences while fixing manufacturer and field strength (n = 8). Test-retest repeatability across the various manufacturer, field strength, and pulse sequence combinations (n = 10) was excellent (ICCs, 0.77-0.94). The overall ICC for all manufacturer, field strength, and sequence combinations (n = 10) was 0.68 (95% confidence interval [CI]: 0.55, 0.82). ICC according to field strength was 0.78 (95% CI: 0.67, 0.88) at 1.5 T (n = 5) and 0.64 (95% CI: 0.49, 0.78) at 3.0 T (n = 5). ICCs according to vendor were 0.83 (95% CI: 0.73, 0.91) (n = 4) and 0.65 (95% CI: 0.51, 0.79) (n = 6). Average patient level variance was 0.042 kPa, with a coefficient of variation of 10.7%. Conclusion MR elastography is a reliable method for assessing liver stiffness, with small amounts of variability between imager manufacturers, field strengths, and pulse sequences. ^© RSNA, 2016.

Opportunity and challenge for diagnosis and treatment of hepatic fibrosis

Hepatic fibrosis is a wound-healing response to all kinds of chronic liver injuries, which is characterized by extracellular matrix remodeling. Hepatic fibrosis ultimately leads to cirrhosis and even hepatic cell carcinoma. Thus, diagnosis and treatment of hepatic fibrosis are important for the management of chronic liver diseases. Recently, the study of hepatic fibrogenesis has witnessed tremendous progress, with many new diagnostic and therapeutic options emerging. This article mainly discusses the opportunity and challenge for diagnosis and treatment of hepatic fibrosis.

Evaluation of liver stiffness with magnetic resonance elastography in patients with constrictive pericarditis: Preliminary findings

PURPOSE

To evaluate with magnetic resonance elastography (MRE) whether patients with constrictive pericarditis (CP) have increased hepatic stiffness. CP results in reduced pericardial compliance, ventricular interdependence, and right heart failure. Patients with untreated CP may develop liver fibrosis and ultimately cirrhosis due to chronic venous congestion. Chronic venous congestion ± fibrosis may lead to increased liver stiffness.

MATERIALS AND METHODS

Prospectively, patients with suspected CP underwent 2D transthoracic echocardiography, cardiac MRI, and liver MRE. An automated method was used to draw regions of interest (ROIs) on the stiffness maps to calculate the mean liver stiffness in kilopascals (kPa). A t-test with α = 0.05 was performed between stiffness values of patients with positive and negative CP findings based on previously published echocardiography criteria.

RESULTS

Nineteen patients met inclusion criteria with a mean ± standard deviation (SD) age of 51 ± 16 years. Nine patients (47%) had CP. Mean liver stiffness trended higher in patients with CP compared to those without CP (4.04 kPa vs. 2.46; P = 0.045). Liver stiffness correlated with MRI septal bounce (P = 0.04), inferior vena cava size (P = 0.003), echo abnormal septal motion (P = 0.04), and echo mitral inflow variation >25% (P = 0.02). Only MRI septal bounce predicted CP by echocardiography (P < 0.001).

CONCLUSION

CP was associated with increased liver stiffness. The increased stiffness is most likely secondary to chronic hepatic venous congestion and/or fibrosis. MRE may be useful for noninvasive liver stiffness assessment in CP. J. Magn. Reson. Imaging 2016;44:81-88.

Non-invasive diagnosis of liver fibrosis and cirrhosis

The evaluation and follow up of liver fibrosis and cirrhosis have been traditionally performed by liver biopsy. However, during the last 20 years, it has become evident that this “gold-standard” is imperfect; even according to its proponents, it is only “the best” among available methods. Attempts at uncovering non-invasive diagnostic tools have yielded multiple scores, formulae, and imaging modalities. All are better tolerated, safer, more acceptable to the patient, and can be repeated essentially as often as required. Most are much less expensive than liver biopsy. Consequently, their use is growing, and in some countries the number of biopsies performed, at least for routine evaluation of hepatitis B and C, has declined sharply. However, the accuracy and diagnostic value of most, if not all, of these methods remains controversial. In this review for the practicing physician, we analyze established and novel biomarkers and physical techniques. We may be witnessing in recent years the beginning of the end of the first phase for the development of non-invasive markers. Early evidence suggests that they might be at least as good as liver biopsy. Novel experimental markers and imaging techniques could produce a dramatic change in diagnosis in the near future.