Magnetic Resonance Elastography of Liver: Current Update. Top Magn Reson Imaging. 2018;27:319-333. [PMID: 30289828 DOI: 10.1097/rmr.0000000000000177]

Viscoelastic polyacrylamide MR elastography phantoms with tunable damping ratio independent of shear stiffness

Physiologically modeled test samples with known properties and characteristics, or phantoms, are essential for developing sensitive, repeatable, and accurate quantitative MRI techniques. Magnetic resonance elastography (MRE) is one such technique used to estimate tissue mechanical properties, and it is advantageous to use phantoms with independently tunable mechanical properties to benchmark the accuracy of MRE methods. Phantoms with tunable shear stiffness are commonly used for MRE, but tuning the viscosity or damping ratio has proven to be difficult. A promising candidate for MRE phantoms with tunable damping ratio is polyacrylamide (PAA). While pure PAA has very low attenuation, viscoelastic hydrogels have been made by entrapping linear polyacrylamide strands (LPAA) within the PAA network. In this study, we evaluate the use of LPAA/PAA gels as physiologically accurate phantoms with tunable damping ratio, independent of shear stiffness, via MRE. Phantoms were made with 15.3 wt% PAA while the LPAA concentration ranged from 4.5 wt% to 8.0 wt%. MRE was performed at 9.4 T with 400 Hz vibration on all phantoms revealing a strong, positive correlation between damping ratio and LPAA content (p < 0.001). There was no significant correlation between shear stiffness and LPAA content, confirming a constant PAA concentration yielded constant shear stiffness. Rheometry at 10 Hz was performed to verify the damping ratio of the phantoms. Nearly identical slopes for damping ratio versus LPAA content were found from both MRE and rheometry (0.0073 and 0.0075 respectively). Ultimately, this study validates the adaptation of polyacrylamide gels into physiologically-relevant MRE phantoms to enable testing of MRE estimates of damping ratio.

Cardiac and Liver Fibrosis Assessed by Multiparametric MRI in Patients with Fontan Circulation

The abnormal hemodynamics in Fontan circulation due to persistently increased systemic venous pressure results in hepatic venous congestion and Fontan-associated liver disease. Combined assessment of cardiac and liver fibrosis and cardiac remodeling using multiparametric MRI in this context have not been fully explored. To evaluate cardiac and liver fibrosis and cardiac remodeling using multiparametric MRI in patients who have undergone Fontan procedures. Thirty-eight patients and 23 controls underwent cardiac and liver MRI examinations in a 3.0-T scanner. Mann-Whitney, Fisher exact test, and Spearman's correlation were applied to evaluate myocardial volumes, function, native cardiac and liver T1 mapping, ECVs and liver stiffness. The mean native cardiac T1 value (p = 0.018), cardiac ECV (p < 0.001), liver native T1 (p < 0.001), liver ECV (p < 0.001), and liver stiffness (p < 0.001) were higher in patients than controls. The indexed end-diastolic volume (EDVi) correlated with the myocardial ECV (r = 0.356; p = 0.033), native liver T1 (r = 0.571; p < 0.001), and with liver stiffness (r = 0.391; p = 0.015). In addition, liver stiffness correlated with liver ECV (r = 0.361; p = 0.031) and native liver T1 (r = 0.458; p = 0.004). An association between cardiac remodeling and cardiac and liver fibrosis were found in this population. The usefulness of MRI to follow cardiac and liver involvement in these patients is critical to improve treatment strategies and to prevent the need for combined liver and heart transplantation.

Free-breathing motion corrected magnetic resonance elastography of the abdomen

Background

Magnetic resonance elastography (MRE) is a non-invasive method to measure the viscoelastic properties of tissue and has been applied in multiple abdominal organs. However, abdominal MRE suffers from detrimental breathing motion causing misalignment of structures between repeated acquisitions for different MRE dimensions (e.g., motion encoding directions and wave phase offsets). This study investigated motion correction strategies to resolve all breathing motion on sagittal free-breathing MRE acquisitions in a phantom, in healthy volunteers and showed feasibility in patients.

Methods

First, in silico experiments were performed on a static phantom dataset with simulated motion. Second, eight healthy volunteers underwent two sagittal MRE acquisitions in the pancreas and right kidney. The multi-frequency free-breathing spin-echo echo-planar-imaging (SE-EPI) MRE consisted of four frequencies (30, 40, 50, 60 Hz), eight wave-phase offsets, with 3 mm3 isotropic voxel size. Following data re-sorting in different number of motion states (4 till 12) based on respiratory waveform signal, three intensity-based registration methods (monomodal, multimodal, and phase correlation) and non-rigid local registration were compared. A ranking method was used to determine the best registration method, based on seven signal-to-noise and image quality measures. Repeatability was assessed for no motion correction (Original) and the best performing method (Best) using Bland-Altman analysis. Lastly, the best motion correction method was compared to no motion correction on patient MRE data [pancreatic ductal adenocarcinoma (PDAC, n=5) and metabolic dysfunction-associated steatotic liver disease (MASLD) (n=1)].

Results

In silico experiments showed a deviation of shear wave speed (SWS) with simulated motion to the ground truth, which was (partially) resolved using motion correction. In healthy volunteers ranking resulted in the best motion correction method of monomodal registration using nine motion states, while no motion correction was ranked last. Limits of agreement were (-0.18, 0.14), and (-0.25, 0.18) m/s for Best and Original, respectively. Using motion correction in patients resulted in a significant increase in SWS in the pancreas (Original: 1.39±0.10 and Best: 1.50±0.17 m/s). After motion correction PDAC had a mean SWS of 1.56±0.27 m/s (Original: 1.42±0.25 m/s). The fibrotic liver mean SWS was 2.07±0.20 m/s (Original: 2.12±0.18 m/s).

Conclusions

Motion correction in sagittal free-breathing abdominal MRE results in improved data quality, inversion precision, repeatability, and is feasible in patients.

Low-frequency MR elastography reveals altered deep gray matter viscoelasticity in multiple sclerosis

INTRODUCTION

Brain viscoelasticity as assessed by magnetic resonance elastography (MRE) has been discussed as a promising surrogate of microstructural alterations due to neurodegenerative processes. Existing studies indicate that multiple sclerosis (MS) is associated with a global reduction in brain stiffness. However, no study to date systematically investigated the MS-related characteristics of brain viscoelasticity separately in normal-appearing white matter (NAWM), deep gray matter (DGM) and T2-hyperintense white matter (WM) lesions.

METHODS

70 MS patients and 42 healthy volunteers underwent whole-cerebral MRE using a stimulated echo sequence (DENSE) with a low-frequency mechanical excitation at 20 Hertz. The magnitude |G∗| (Pa) and phase angle φ (rad) of the complex shear modulus G∗ were reconstructed by multifrequency dual elasto-visco (MDEV) inversion and related to structural imaging and clinical parameters.

RESULTS

We observed φ in the thalamus to be higher by 4.3 % in patients relative to healthy controls (1.11 ± 0.07 vs. 1.06 ± 0.07, p < 0.0001). Higher Expanded Disability Status Scale (EDSS) scores were negatively associated with φ in the basal ganglia (p = 0.01). We measured φ to be lower in MS lesions compared to surrounding NAWM (p = 0.001), which was most prominent for lesions in the temporal lobe (1.01 ± 0.22 vs. 1.06 ± 0.19, p = 0.003). Age was associated with lower values of |G∗| (p = 0.04) and φ (p = 0.004) in the thalamus of patients. No alteration in NAWM stiffness relative to WM in healthy controls was observed.

CONCLUSION

Low-frequency elastography in MS patients reveals age-independent alterations in the viscoelasticity of deep gray matter at early stages of disease.

Telomere Biology Disorder: A Focus on Gastrointestinal and Hepatic Manifestations

PURPOSE OF REVIEW

Telomere biology disorders (TBD) encompass several illnesses caused by underlying mutations in telomere maintenance leading to premature telomere attrition and telomere dysfunction. These disorders have unique features but share common disease manifestations including pulmonary fibrosis, cirrhosis, and bone marrow failure. The goals of this article are to provide an overview of the gastrointestinal and hepatic manifestations of TBD, focusing on their pathophysiology, clinical disease states, and current management strategies.

RECENT FINDINGS

Telomere shortening has been observed in patients with chronic liver disease and is associated with a higher risk of progression to cirrhosis and portal hypertension. While the directionality of the association between telomere dysfunction and senescence on liver disease is not fully understood, research in TBD may provide clarity and could lead to future therapies for this increasingly prevalent disease. While treatment options remain limited in TBD-associated liver disease, recent studies point to the safety and efficacy of liver transplantation among patients with end-stage liver disease.

Macro-indentation testing of soft biological materials and assessment of hyper-elastic material models from inverse finite element analysis

Mechanical characterization of hydrogels and ultra-soft tissues is a challenging task both from an experimental and material parameter estimation perspective because they are much softer than many biological materials, ceramics, or polymers. The elastic modulus of such materials is within the 1 - 100 kPa range, behaving as a hyperelastic solid with strain hardening capability at large strains. In the current study, indentation experiments have been performed on agarose hydrogels, bovine liver, and bovine lymph node specimens. This work reports on the reliable determination of the elastic modulus by indentation experiments carried out at the macro-scale (mm) using a spherical indenter. However, parameter identification of the hyperelastic material properties usually requires an inverse finite element analysis due to the lack of an analytical contact model of the indentation test. Hence a comprehensive study on the spherical indentation of hyperelastic soft materials is carried out through robust computational analysis. Neo-Hookean and first-order Ogden hyperelastic material models were found to be most suitable. A case study on known anisotropic hyperelastic material showed the inability of the inverse finite element method to uniquely identify the whole material parameter set.

Co-existence of hepatic and pancreatic fibrosis in chronic pancreatitis patients including associated risk factors: a magnetic resonance elastography study

OBJECTIVES

To investigate the co-existence of hepatic and pancreatic fibrosis using magnetic resonance elastography (MRE) in chronic pancreatitis (CP), including the association between hepatic and pancreatic MRE-derived stiffness and exploration of potential etiological risk factors.

MATERIALS AND METHODS

Fifty-four CP patients and 35 healthy controls underwent hepatic and pancreatic MRE with measurements of tissue stiffness. Clinical parameters including stage (probable or definite CP), etiology of CP, the presence of diabetes or exocrine insufficiency, and previous history of common bile duct stenosis were assessed. Uni- and multivariate regression models were used to investigate risk factors associated with hepatic fibrosis/stiffness in CP patients.

RESULTS

Fifteen percent of CP patients and none of the controls had abnormal liver stiffness (>2.5 kPa), p = 0.02. 5.6% of CP patients had liver stiffness indicating F1 fibrosis (>2.93 kPa). However, hepatic stiffness was not higher in patients than in healthy controls (2.20 ± 0.41 vs 2.08 ± 0.21 kPa, p = 0.10). In patients, a positive association was seen between hepatic and pancreatic stiffness (r = 0.270, p = 0.048). In the multivariate analysis (adjusted for age, gender and BMI), liver stiffness was significantly associated with alcoholic etiology of CP (p = 0.029). In contrast, stage of CP, history of common bile duct stenosis, and the presence of diabetes or exocrine insufficiency were not associated with liver stiffness (all p > 0.14).

CONCLUSIONS

Only a modest co-existence of hepatic and pancreatic fibrosis was observed in CP. However, the positive association between hepatic and pancreatic stiffness indicates some level of common pathophysiology. Especially, alcoholic etiology of CP was related to increased hepatic stiffness.

Magnetic resonance elastography for noninvasive detection of liver fibrosis: is there an added value of 3D acquisition?

PURPOSE

(1) Assess the diagnostic performance of liver 3D magnetic resonance elastography (MRE) parameters (including stiffness, storage/loss modulus and damping ratio) compared to liver stiffness measured with 2D MRE for noninvasive detection of advanced liver fibrosis (F3-F4) and cirrhosis (F4) in patients with chronic liver disease. (2) Assess the value of serum markers (FIB-4) in detecting advanced liver fibrosis and cirrhosis in the same patients.

METHODS

This was a single center, prospective IRB-approved cross-sectional study that included 49 patients (M/F: 23/26, mean age 50.8 y) with chronic liver disease and concomitant liver biopsy. MRE was acquired at 1.5T using a spin echo-EPI sequence. The following parameters were measured: liver stiffness using 2D MRE (LS-2D) and 3D MRE parameters (LS-3D, liver storage, loss modulus and damping ratio). The Mann-Whitney U test, ROC curve analysis, Spearman correlation and logistic regression were performed to evaluate diagnostic performance of MRE parameters and FIB-4.

RESULTS

LS-2D and LS-3D had similar diagnostic performance for diagnosis of F3-F4, with AUCs of 0.87 and 0.88, sensitivity of 0.71 and 0.81, specificity of 0.89 for both. For diagnosis of F4, LS-2D and LS-3D had similar performance with AUCs of 0.81 for both, sensitivity of 0.75 and 0.83, and specificity of 0.84 and 0.73, respectively. Additional 3D parameters (storage modulus, loss modulus, damping ratio) had variable performance, with AUC range of 0.59-0.78 for F3-F4; and 0.52-0.70 for F4. FIB-4 had lower diagnostic performance, with AUCs of 0.66 for F3-F4, and 0.68 for F4.

CONCLUSION

Our study shows no added value of 3D MRE compared to 2D MRE for detection of advanced fibrosis and cirrhosis, while FIB-4 had lower diagnostic performance.

An individual patient data meta-analysis to determine cut-offs for and confounders of NAFLD-fibrosis staging with magnetic resonance elastography

BACKGROUND & AIMS

We conducted an individual patient data meta-analysis to establish stiffness cut-off values for magnetic resonance elastography (MRE) in staging liver fibrosis and to assess potential confounding factors.

METHODS

A systematic review of the literature identified studies reporting MRE data in patients with NAFLD. Data were obtained from the corresponding authors. The pooled diagnostic cut-off value for the various fibrosis stages was determined in a two-stage meta-analysis. Multilevel modelling methods were used to analyse potential confounding factors influencing the diagnostic accuracy of MRE in staging liver fibrosis.

RESULTS

Eight independent cohorts comprising 798 patients were included in the meta-analysis. The area under the receiver operating characteristic curve (AUROC) for MRE in detecting significant fibrosis was 0.92 (sensitivity, 79%; specificity, 89%). For advanced fibrosis, the AUROC was 0.92 (sensitivity, 87%; specificity, 88%). For cirrhosis, the AUROC was 0.94 (sensitivity, 88%, specificity, 89%). Cut-offs were defined to explore concordance between MRE and histopathology: ≥F2, 3.14 kPa (pretest probability, 39.4%); ≥F3, 3.53 kPa (pretest probability, 24.1%); and F4, 4.45 kPa (pretest probability, 8.7%). In generalized linear mixed model analysis, histological steatohepatitis with higher inflammatory activity (odds ratio 2.448, 95% CI 1.180-5.079, p <0.05) and high gamma-glutamyl transferase (GGT) concentration (>120U/L) (odds ratio 3.388, 95% CI 1.577-7.278, p <0.01] were significantly associated with elevated liver stiffness, and thus affecting accuracy in staging early fibrosis (F0-F1). Steatosis, as measured by magnetic resonance imaging proton density fat fraction, and body mass index(BMI) were not confounders.

CONCLUSIONS

MRE has excellent diagnostic performance for significant, advanced fibrosis and cirrhosis in patients with NAFLD. Elevated inflammatory activity and GGT level may lead to overestimation of early liver fibrosis, but anthropometric measures such as BMI or the degree of steatosis do not.

IMPACT AND IMPLICATIONS

This individual patient data meta-analysis of eight international cohorts, including 798 patients, demonstrated that MRE achieves excellent diagnostic accuracy for significant, advanced fibrosis and cirrhosis in patients with NAFLD. Cut-off values (significant fibrosis, 3.14 kPa; advanced fibrosis, 3.53 kPa; and cirrhosis, 4.45 kPa) were established. Elevated inflammatory activity and gamma-glutamyltransferase level may affect the diagnostic accuracy of MRE, leading to overestimation of liver fibrosis in early stages. We observed no impact of diabetes, obesity, or any other metabolic disorder on the diagnostic accuracy of MRE.

Water flow elastography - A promising tool to measure tissue stiffness during minimally invasive surgery

Mechanical properties are important markers for pathological processes in tissue. Elastography techniques are therefore becoming more and more useful for diagnostics. In minimally invasive surgery (MIS), however, the probe size is limited and the handling is restricted, thereby excluding the application of most established elastography techniques. In this paper we introduce water flow elastography (WaFE) as a new technique that benefits from a small and inexpensive probe. This probe flows pressurized water against the sample surface to locally indent it. The volume of the indentation is measured with a flow meter. We use finite element simulations to find the relation between the indentation volume, the water pressure, and the Young's modulus of the sample. We used WaFE to measure the Young's modulus of silicone samples and porcine organs, finding agreement within 10% to measurements with a commercial material testing machine. Our results show that WaFE is a promising technique for providing local elastography in MIS.

Evaluation of Spleen Stiffness in Young Healthy Volunteers Using Magnetic Resonance Elastography

PURPOSE

Magnetic resonance elastography (MRE) has been established as the most accurate noninvasive technique for diagnosing liver fibrosis. Recent publications have suggested that the measurement of splenic stiffness is useful in setting where portal hypertension may be present. The goal of the current study was to compile normative data for MRE-assessed stiffness measurements of the spleen in young adults.

MATERIALS AND METHODS

A total of 100 healthy young Caucasian volunteers (65 females and 35 males) in the age range of 20 to 32 years were enrolled in this study. The participants reported no history of chronic spleen and liver disease, normal alcohol consumption, and a normal diet. The MRE data were acquired by using a 1.5 T whole-body scanner and a 2D GRE pulse sequence with 60 Hz excitation. Spleen stiffness was calculated as a weighted mean of stiffness values in the regions of interest manually drawn by the radiologist on three to five spleen slices.

RESULTS

Mean spleen stiffness was 5.09 ± 0.65 kPa for the whole group. Male volunteers had slightly higher splenic stiffness compared to females: 5.28 ± 0.78 vs. 4.98 ± 0.51 kPa, however, this difference was not statistically significant (p = 0.12). Spleen stiffness did not correlate with spleen fat content and liver stiffness but a statistically significant correlation with spleen volume was found.

CONCLUSIONS

The findings of this study provide normative values for 2D MRE-based measurement of spleen stiffness in young adults, a basis for assessing the value of this biomarker in young patients with portal system pathologies.

Quantitative MRI of diffuse liver diseases: techniques and tissue-mimicking phantoms

Quantitative magnetic resonance imaging (MRI) techniques are emerging as non-invasive alternatives to biopsy for assessment of diffuse liver diseases of iron overload, steatosis and fibrosis. For testing and validating the accuracy of these techniques, phantoms are often used as stand-ins to human tissue to mimic diffuse liver pathologies. However, currently, there is no standardization in the preparation of MRI-based liver phantoms for mimicking iron overload, steatosis, fibrosis or a combination of these pathologies as various sizes and types of materials are used to mimic the same liver disease. Liver phantoms that mimic specific MR features of diffuse liver diseases observed in vivo are important for testing and calibrating new MRI techniques and for evaluating signal models to accurately quantify these features. In this study, we review the liver morphology associated with these diffuse diseases, discuss the quantitative MR techniques for assessing these liver pathologies, and comprehensively examine published liver phantom studies and discuss their benefits and limitations.

Abdominal MR elastography with multiple driver arrays: performance and repeatability

PURPOSE

To evaluate the performance and repeatability assessing liver, spleen, and kidney stiffness with magnetic resonance elastography (MRE), using arrays of pneumatic passive drivers.

METHODS

An array of four flexible, pneumatically activated passive drivers for abdominal MRE were developed and tested in this study. Multiple MRE acquisitions were performed prospectively in a series of eleven volunteers, with activation of all combinations of the four drivers, individually and simultaneously. MRE exams were repeated three times to study within-day and between-day test-retest repeatability. Semi-quantitative evaluation of wave propagation and penetration, and quantitative assessment of tissue stiffness was conducted for liver, spleen, and kidneys.

RESULTS

When driver location and amplitude were sufficient to achieve necessary shear wave illumination in any given region of interest, the results showed excellent test-retest repeatability in abdominal organ stiffness with both single and multiple driver configurations. The results confirmed that multiple driver arrays provided suitable shear wave illumination over a larger region of the abdomen, allowing more reliable stiffness measurements in multiple organs. MRE assessment of the spleen was found to be prone to effects of excessive shear wave amplitude, however.

CONCLUSION

A multiple driver array provides shear wave illumination over a larger region of the abdomen than obtained with a single driver, for MRE assessment of multiple abdominal organs, providing excellent test-retest repeatability in stiffness measurements. However, careful tuning of the location and amplitude of each driver is essential to achieve consistent results.

Elastography of the Liver in Wilson's Disease

Staging of liver fibrosis is of special significance in Wilson's disease as it determines the patient's prognosis and treatment. Histopathological examination is a standard method for fibrosis assessment; however, non-invasive methods like transient elastography and share wave elastography are believed to be reliable and repetitive and are expected to replace liver biopsy in Wilson's disease. This article presents a short description of available elastography techniques and the results of the most recent studies on elastography of the liver in patients with Wilson's disease.

Transversely-isotropic brain in vivo MR elastography with anisotropic damping

Measuring tissue parameters from increasingly sophisticated mechanical property models may uncover new contrast mechanisms with clinical utility. Building on previous work on in vivo brain MR elastography (MRE) with a transversely-isotropic with isotropic damping (TI-ID) model, we explore a new transversely-isotropic with anisotropic damping (TI-AD) model that involves six independent parameters describing direction-dependent behavior for both stiffness and damping. The direction of mechanical anisotropy is determined by diffusion tensor imaging and we fit three complex-valued moduli distributions across the full brain volume to minimize differences between measured and modeled displacements. We demonstrate spatially accurate property reconstruction in an idealized shell phantom simulation, as well as an ensemble of 20 realistic, randomly-generated simulated brains. We characterize the simulated precisions of all six parameters across major white matter tracts to be high, suggesting that they can be measured independently with acceptable accuracy from MRE data. Finally, we present in vivo anisotropic damping MRE reconstruction data. We perform t-tests on eight repeated MRE brain exams on a single-subject, and find that the three damping parameters are statistically distinct for most tracts, lobes and the whole brain. We also show that population variations in a 17-subject cohort exceed single-subject measurement repeatability for most tracts, lobes and whole brain, for all six parameters. These results suggest that the TI-AD model offers new information that may support differential diagnosis of brain diseases.

Multiparametric MR assessment of liver fat, iron, and fibrosis: a concise overview of the liver "Triple Screen"

Chronic liver disease (CLD) is a common source of morbidity and mortality worldwide. Non-alcoholic fatty liver disease (NAFLD) serves as a major cause of CLD with a rising annual prevalence. Additionally, iron overload can be both a cause and effect of CLD with a negative synergistic effect when combined with NAFLD. The development of state-of-the-art multiparametric MR solutions has led to a change in the diagnostic paradigm in CLD, shifting from traditional liver biopsy to innovative non-invasive methods for providing accurate and reliable detection and quantification of the disease burden. Novel imaging biomarkers such as MRI-PDFF for fat, R2 and R2* for iron, and liver stiffness for fibrosis provide important information for diagnosis, surveillance, risk stratification, and treatment. In this article, we provide a concise overview of the MR concepts and techniques involved in the detection and quantification of liver fat, iron, and fibrosis including their relative strengths and limitations and discuss a practical abbreviated MR protocol for clinical use that integrates these three MR biomarkers into a single simplified MR assessment. Multiparametric MR techniques provide accurate and reliable non-invasive detection and quantification of liver fat, iron, and fibrosis. These techniques can be combined in a single abbreviated MR "Triple Screen" assessment to offer a more complete metabolic imaging profile of CLD.

A diagnostic test of three-dimensional magnetic resonance elastography imaging for preoperative prediction of microvascular invasion in patients with T1 stage clear cell renal carcinoma

Background

Detection of microvascular invasion (MVI) of kidney tumors is important for selecting the optimal therapeutic strategy. Currently, the prediction of MVI lacks an accurate imaging biomarker. This study evaluated the performance of three-dimensional (3D) magnetic resonance elastography (MRE) imaging in predicting microvascular invasion (MVI) of T1 stage clear cell renal carcinoma (ccRCC).

Methods

In this prospective study, we conducted pre-surgical imaging with a clinical 3.0 T magnetic resonance imaging (MRI) system. Firstly, 83 consecutive patients were enrolled in this study. A 3D MRE stiffness map was generated and transferred to a post-processing workstation. Contrast-enhanced computed tomography (CT) was conducted to calculate the tumor enhancement ratio. The presence of MVI was evaluated by histopathological analysis and graded according to the risk stratification based upon the number and distribution. The mean stiffness and CT tumor enhancement ratio was calculated for tumors with or without MVI. The diagnostic performance [sensitivity, specificity, positive predictive value, negative predictive value, area under the curve (AUC)] and independent predicting factors for MVI were investigated.

Results

Finally, A total of 80 patients (aged 46.7±13.2 years) were enrolled, including 22 cases of tumors with MVI. The mean MRE stiffness of kidney parenchyma and kidney tumors was 4.8±0.2 and 4.5±0.7 kPa, respectively. There was significant difference in the mean MRE stiffness between tumors with MVI (5.4±0.6 kPa) and tumors without MVI (4.1±0.3 kPa) (P<0.05). The sensitivity, specificity, positive predictive value, negative predictive value, and the AUC for mean stiffness in the prediction of MVI were 100%, 75%, 63%, 96%, and 0.87 [95% confidence interval (CI): 0.72, 0.94], respectively. The corresponding values for the CT tumor enhancement ratio were 90%, 80%, 63%, 96%, and 0.88 (95% CI: 0.71, 0.93), respectively. The odds ratio (OR) value for MRE tumor stiffness and CT kidney tumor enhancement ratio in the prediction of MVI was 2.9 (95% CI: 1.8, 3.7) and 1.2 (95% CI: 1.0, 1.7), respectively (P>0.05).

Conclusions

3D MRE imaging has promising diagnostic performance for predicting MVI in T1 stage ccRCC, which may improve the reliability of surgical strategy selection with T1 stage ccRCC.

Early diagnosis of hepatic inflammation in Japanese nonalcoholic fatty liver disease patients using 3D MR elastography

BACKGROUND

The damping ratio (DR) and the loss modulus (G″) obtained by 3D MR elastography complex modulus analysis has been reported recently to reflect early intrahepatic inflammation, and is expected to be a noninvasive biomarker of inflammation in nonalcoholic fatty liver disease (NAFLD). However, the role of the DR and the G″ in Japanese NAFLD patients remains unclear.

METHODS

We enrolled 39 Japanese patients with NAFLD who underwent liver biopsy and 3D MR elastography within 1 month and analyzed the association between DR, G″, and histological activity.

RESULTS

Regarding DR, no evident correlation was observed between the DR and histological activity (p = 0.14) when patients with all fibrosis stages were included. However, when patients were restricted up to stage F2 fibrosis, the association of the DR and inflammation became significant, the DR increasing with the degree of activity (p = 0.02). Among the constituents of fibrosis activity, ballooning correlated with the DR (p < 0.01) while lobular inflammation did not. Regarding G″, it was correlated with histological activity (p < 0.01), ballooning (p < 0.01), and lobular inflammation (p < 0.01) in patients with all fibrosis stages and in patients up to F2 fibrosis (p = 0.03 for activity and p = 0.04 for ballooning). The best cutoff value of DR for hepatitis activity in patients within the F2 stage was 0.094 (area under the receiver operating characteristic curve 0.775, 95% CI: 0.529-1.000) and G″ was 0.402 (area under the receiver operating characteristic curve 0.825, 95% CI: 0.628-1.000).

CONCLUSIONS

The DR and G″ reflected the histological activity in Japanese patients with NAFLD during the early stage, indicating these values for noninvasive diagnosis of inflammation in Japanese patients with NAFLD.

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.

Detecting Early-Stage Liver Fibrosis Using Macromolecular Proton Fraction Mapping Based on Spin-Lock MRI: Preliminary Observations

BACKGROUND

Liver fibrosis is characterized by macromolecule depositions. Recently, a novel technology termed macromolecular proton fraction quantification based on spin-lock magnetic resonance imaging (MPF-SL) is reported to measure macromolecule levels.

HYPOTHESIS

MPF-SL can detect early-stage liver fibrosis by measuring macromolecule levels in the liver.

STUDY TYPE

Retrospective.

SUBJECTS

Fifty-five participants, including 22 with no fibrosis (F0) and 33 with early-stage fibrosis (F1-2), were recruited.

FIELD STRENGTH/SEQUENCE

3 T; two-dimensional (2D) MPF-SL turbo spin-echo sequence, 2D spin-lock T1rho turbo spin-echo sequence, and multi-slice 2D gradient echo sequence.

ASSESSMENT

Macromolecular proton fraction (MPF), T1rho, liver iron concentration (LIC), and fat fraction (FF) biomarkers were quantified within regions of interest.

STATISTICAL TESTS

Group comparison of the biomarkers using Mann-Whitney U tests; correlation between the biomarkers assessed using Spearman's rank correlation coefficient and linear regression with goodness-of-fit; fibrosis stage differentiation using receiver operating characteristic curve (ROC) analysis. P-value < 0.05 was considered statistically significant.

RESULTS

Average T1rho was 41.76 ± 2.94 msec for F0 and 41.15 ± 3.73 msec for F1-2 (P = 0.60). T1rho showed nonsignificant correlation with either liver fibrosis (ρ = -0.07; P = 0.61) or FF (ρ = -0.14; P = 0.35) but indicated a negative correlation with LIC (ρ = -0.66). MPF was 4.73 ± 0.45% and 5.65 ± 0.81% for F0 and F1-2 participants, respectively. MPF showed a positive correlation with liver fibrosis (ρ = 0.59), and no significant correlations with LIC (ρ = 0.02; P = 0.89) or FF (ρ = 0.05; P = 0.72). The area under the ROC curve was 0.85 (95% confidence interval [CI] 0.75-0.95) and 0.55 (95% CI 0.39-0.71; P = 0.55) for MPF and T1rho to discriminate between F0 and F1-2 fibrosis, respectively.

DATA CONCLUSION

MPF-SL has the potential to diagnose early-stage liver fibrosis and does not appear to be confounded by either LIC or FF.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY STAGE: 3.

Ex vivo bovine liver nonlinear viscoelastic properties: MR elastography and rheological measurements

INTRODUCTION

Knowledge of the nonlinear viscoelastic properties of the liver is important, but the complex tissue behavior outside the linear viscoelastic regime has impeded their characterization, particularly in vivo. Combining static compression with magnetic resonance (MR) elastography has the potential to be a useful imaging method for assessing large deformation mechanical properties of soft tissues in vivo. However, this remains to be verified. Therefore this study aims first to determine whether MR elastography can measure the nonlinear mechanical properties of ex vivo bovine liver tissue under varying levels of uniform and focal preloads (up to 30%), and second to compare MR elastography-derived complex shear modulus with standard rheological measurements.

METHOD

Nine fresh bovine livers were collected from a local abattoir, and experiments were conducted within 12hr of death. Two cubic samples (∼10 × 10 × 10 cm³) were dissected from each liver and imaged using MR elastography (60 Hz) under 4 levels of uniform and focal preload (1, 10, 20, and 30% of sample width) to investigate the relationship between MR elastography-derived complex shear modulus (G∗) and the maximum principal Right Cauchy Green Strain (C₁₁). Three tissue samples from each of the same 9 livers underwent oscillatory rheometry under the same 4 preloads (1, 10, 20, and 30% strain). MR elastography-derived complex shear modulus (G∗) from the uniform preload was validated against rheometry by fitting the frequency dependence of G∗ with a power-law and extrapolating rheometry-derived G∗ to 60 Hz.

RESULTS

MR elastography-derived G∗ increased with increasing compressive large deformation strain, and followed a power-law curve (G∗ = 1.73 × C₁₁^-0.38, R² = 0.96). Similarly, rheometry-derived G∗ at 1 Hz, increasing from 0.66 ± 1.03 kPa (1% strain) to 1.84 ± 1.65 kPa (30% strain, RM one-way ANOVA, P < 0.001), and the frequency dependence of G∗ followed a power-law with the exponent decreasing from 0.13 to 0.06 with increasing preload. MR elastography-derived G∗ was 1.4-3.1 times higher than the extrapolated rheometry-derived G∗ at 60 Hz, but the strain dependence was consistent between rheometry and MR elastography measurements.

CONCLUSIONS

This study demonstrates that MR elastography can detect changes in ex vivo bovine liver complex shear modulus due to either uniform or focal preload and therefore can be a useful technique to characterize nonlinear viscoelastic properties of soft tissue, provided that strains applied to the tissue can be quantified. Although MR elastography could reliably characterize the strain dependence of the ex vivo bovine liver, MR elastography overestimated the complex shear modulus of the tissue compared to rheological measurements, particularly at lower preload (<10%). That is likely to be important in clinical hepatic MR elastography diagnosis studies if preload is not carefully considered. A limitation is the absence of overlapping frequency between rheometry and MR elastography for formal validation.

Portal Venous Thrombosis in Alcoholic Hepatitis: A Relatively Unknown Association

Portal venous thrombosis (PVT) is a rare diagnosis in the general population. However, it is seen in patients with liver cirrhosis with an estimated prevalence ranging from 0.6% to 26%. Literature reports that about one-third of PVT cases have an unknown etiology. Identifying the precipitating factors implicated in the development of PVT is imperative as it may help guide therapy. Although the association between liver cirrhosis and PVT has been well established in current literature, there continues to be a relative lack of awareness of alcoholic hepatitis (AH) as a risk factor for PVT. Identifying AH as a trigger for thrombosis can help avoid extended anticoagulation and its complications. In the following case report and brief review, we discuss an uncommon case of a 33-year-old male who came to the hospital emergency department with complaints of nauseousness, abdominal discomfort, and yellow discoloration. Lab investigations showed transaminitis. The diagnosis of AH was established, and an abdominal duplex ultrasound revealed PVT. Heparin drip was started as a part of treatment, which improved his abdominal discomfort. He was eventually discharged on apixaban 5 mg twice daily for 3 months and a repeat abdominal duplex ultrasound in 3 months to check for the resolution of the PVT.

Preoperative evaluation of liver regeneration following hepatectomy in hepatocellular carcinoma using magnetic resonance elastography

BACKGROUND

For patients with hepatocellular carcinoma (HCC) undergoing hepatectomy, insufficient remnant liver regenerative capacity can lead to liver failure. The aim of this study was to evaluate the potential role of magnetic resonance elastography (MRE) for the preoperative prediction of liver regeneration in patients with HCC after partial hepatectomy (PH).

METHODS

A total of 54 patients with HCC undergoing MRE prior to PH were retrospectively included. The total functional liver, volume of preoperative future liver remnant (LVpre), and volume of postoperative liver remnant (LVpost), respectively, were measured, and the regeneration index (RI) and parenchymal hepatic resection rate (PHRR) were manually calculated. Univariate and multivariate logistic regression analyses were conducted to identify factors associated with a high RI, and receiver operating characteristic (ROC) curves were employed to evaluate the diagnostic performance of the liver stiffness (LS) values. Patients were classified into three subgroups based on the value of PHRR: low PHRR (<30%), intermediate PHRR (30-50%), and high PHRR (>50%). Subsequently, Spearman correlation analysis was used to investigate the relationship between LS values and RI in the subgroups.

RESULTS

Multivariable analysis revealed a low LS value was associated with greater odds of a high RI [odds ratio (OR), 0.049; 95% confidence interval (CI): 0.002 to 0.980]. An optimal cutoff value of 3.30 kPa was used to divide all patients into a low RI group and a high RI group with an area under the curve (AUC) value of 0.882 (95% CI: 0.767 to 0.996). A significant negative relationship between RI and LS values (r=-0.799; P<0.001) was observed in the intermediate PHRR subgroup.

CONCLUSIONS

The LS values based on MRE may serve as a potential preoperative predictor of liver regeneration for patients with HCC undergoing PH.

Clinical studies of magnetic resonance elastography from 1995 to 2021: Scientometric and visualization analysis based on CiteSpace

BACKGROUND

To assess the knowledge framework around magnetic resonance elastography (MRE) and to explore MRE research hotspots and emerging trends.

METHODS

The Science Citation Index Expanded of the Web of Science Core Collection was searched on 22 October 2021 for MRE-related studies published between 1995 and 2021. Excel 2016 and CiteSpace V (version 5.8.R3) were used to analyze the downloaded data.

RESULTS

In all, 1,236 articles published by 726 authors from 540 institutions in 40 countries were included in this study. The top 10 authors published 57.6% of all included articles. The 3 most productive countries were the USA (n=631), Germany (n=202), and France (n=134), and the 3 most productive institutions were the Mayo Clinic (n=240), Charité (n=131), and the University of Illinois (n=56). The USA and the Mayo Clinic had the highest betweenness centrality among countries and institutions, respectively, and played an important role in the field of MRE. In this study, the 24,347 distinct references were clustered into 48 categories via reasonable clustering using specific keywords, forming the knowledge framework. Among the 294 co-occurring keywords, "hepatic fibrosis", "stiffness", "skeletal muscle", "acoustic strain wave", "in vivo", and "non-invasive assessment" were research hotspots. "Diagnostic performance", "diagnostic accuracy", "hepatic steatosis", "chronic hepatitis B", "radiation force impulse", "children", and "echo" were frontier topics.

CONCLUSIONS

Scientometric and visualized analysis of MRE can provide information regarding the knowledge framework, research hotspots, frontier areas, and emerging trends in this field.

Predictive Value of Liver Stiffness Measurement by Magnetic Resonance Elastography for Complications after Liver Resection: A Systematic Review and Meta-Analysis

BACKGROUND AND AIMS

Liver fibrosis has been recognized as a significant risk factor for short-term outcomes after hepatectomy. Magnetic resonance elastography (MRE) showed higher diagnostic performance in staging liver fibrosis than other elastography modalities. This study aimed to assess the accuracy of predicting postoperative complications in patients with malignant liver tumors using liver stiffness measurement (LSM) by MRE.

METHODS

After a systematic review of the relevant studies, the sensitivity, specificity, positive and negative likelihood ratios, diagnostic odds ratio, and area under the curve (AUC) for the diagnosis of postoperative complications were pooled using bivariate meta-analysis. Meanwhile, the pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the effect. Heterogeneity was explored by sensitivity analysis, univariate meta-regression, and subgroup analysis. The potential publication bias was evaluated by the Deek's funnel plot test.

RESULTS

Eight studies comprising a total of 1,154 patients that predicted postoperative outcomes as their purpose were ultimately included in the quantitative analysis. The pooled results of the meta-analysis revealed that the pooled sensitivity, specificity, and AUC were 78% (95% CI: 69-85%, Higgins's inconsistency index [I2] = 43.00), 75% (95% CI: 70-80%, Higgins's inconsistency index [I2] = 72.53), and 0.83 (95% CI: 0.80-0.86), respectively. Preoperative LSM by MRE was significantly associated with the development of overall postoperative outcomes (OR 1.78, 95% CI: 1.49-2.08). Univariate meta-regression showed that advanced fibrosis stage (≥F3), HCC patient proportion and cut-off value significantly influenced the heterogeneity of the included studies. The AUC of several novel prediction models based on LSM by MRE ranged from 0.818 to 0.911.

CONCLUSIONS

In conclusion, liver stiffness measured by MRE was a significant predictor of postoperative outcomes in patients undergoing liver resection. Future studies could focus on setting a prognostic model integrated with LSM by MRE in distinguishing patients at high risk of posthepatectomy complications.

Liver fibrosis assessment: MR and US elastography

Elastography has emerged as a preferred non-invasive imaging technique for the clinical assessment of liver fibrosis. Elastography methods provide liver stiffness measurement (LSM) as a surrogate quantitative biomarker for fibrosis burden in chronic liver disease (CLD). Elastography can be performed either with ultrasound or MRI. Currently available ultrasound-based methods include strain elastography, two-dimensional shear wave elastography (2D-SWE), point shear wave elastography (pSWE), and vibration-controlled transient elastography (VCTE). MR Elastography (MRE) is widely available as two-dimensional gradient echo MRE (2D-GRE-MRE) technique. US-based methods provide estimated Young's modulus (eYM) and MRE provides magnitude of the complex shear modulus. MRE and ultrasound methods have proven to be accurate methods for detection of advanced liver fibrosis and cirrhosis. Other clinical applications of elastography include liver decompensation prediction, and differentiation of non-alcoholic steatohepatitis (NASH) from simple steatosis (SS). In this review, we briefly describe the different elastography methods, discuss current clinical applications, and provide an overview of advances in the field of liver elastography.

US Shear-Wave Elastography Dispersion for Characterization of Chronic Liver Disease

Background Little is known about the benefits of the use of dispersion slope (DS) as a viscosity-related parameter derived from two-dimensional (2D) shear-wave elastography (SWE) in the stratification of hepatic pathologic stages. Purpose To evaluate whether DS as an additional parameter can improve the diagnostic performance in detecting liver necroinflammation, fibrosis, and steatosis. Materials and Methods In this prospective study, consecutive participants with chronic liver disease who underwent liver biopsy and 2D SWE were recruited between July 2019 and September 2020. DS and liver stiffness (LS) measurements were obtained with use of a 2D SWE system immediately before biopsy. The biopsy specimens were assessed to obtain the scores of fibrosis, necroinflammation, and steatosis. Differences in the area under the receiver operating characteristic curve (AUC) were used to compare the diagnostic performance of DS, LS, and a combination of DS and LS. Results There were 159 participants evaluated (among them, 79 participants with chronic hepatitis B and 11 participants with nonalcoholic fatty liver disease). The distributions of DS values among various necroinflammatory activities (P = .02) and fibrosis stages (P < .001) were different. Moreover, DS was only associated with fibrosis after subgroup analysis based on the fibrosis stages and necroinflammatory activities (P < .001). The AUCs of DS in detecting clinically significant fibrosis (fibrosis stage ≥F2), cirrhosis (fibrosis stage of F4), and moderate to severe necroinflammatory activity (necroinflammatory activity ≥A2) were 0.72 (95% CI: 0.64, 0.79), 0.71 (95% CI: 0.63, 0.78), and 0.64 (95% CI: 0.55, 0.71), respectively. The differences of AUCs were not apparent for the DS and LS combination model after excluding DS (fibrosis stage ≥F2: 0.00 [95% CI: 0.00, 0.01], fibrosis stage of F4: -0.01 [95% CI: -0.02, 0.00], and necroinflammatory activity ≥A2: 0.00 [95% CI: 0.00, 0.01]). Conclusion The addition of dispersion slope derived from two-dimensional shear-wave elastography did not improve the diagnostic performance in detecting liver fibrosis, necroinflammation, or steatosis in patients with primarily viral hepatitis. ClinicalTrials.gov registration no.: NCT03777293 © RSNA, 2022 Online supplemental material is available for this article.

Targeting the tumor biophysical microenvironment to reduce resistance to immunotherapy

Immunotherapy based on immune checkpoint inhibitors has evolved into a new pillar of cancer treatment in clinics, but dealing with treatment resistance (either primary or acquired) is a major challenge. The tumor microenvironment (TME) has a substantial impact on the pathological behaviors and treatment response of many cancers. The biophysical clues in TME have recently been considered as important characteristics of cancer. Furthermore, there is mounting evidence that biophysical cues in TME play important roles in each step of the cascade of cancer immunotherapy that synergistically contribute to immunotherapy resistance. In this review, we summarize five main biophysical cues in TME that affect resistance to immunotherapy: extracellular matrix (ECM) structure, ECM stiffness, tumor interstitial fluid pressure (IFP), solid stress, and vascular shear stress. First, the biophysical factors involved in anti-tumor immunity and therapeutic antibody delivery processes are reviewed. Then, the causes of these five biophysical cues and how they contribute to immunotherapy resistance are discussed. Finally, the latest treatment strategies that aim to improve immunotherapy efficacy by targeting these biophysical cues are shared. This review highlights the biophysical cues that lead to immunotherapy resistance, also supplements their importance in related technologies for studying TME biophysical cues in vitro and therapeutic strategies targeting biophysical cues to improve the effects of immunotherapy.

Virtual Biopsy in Soft Tissue Sarcoma. How Close Are We?

A shift in radiology to a data-driven specialty has been unlocked by synergistic developments in imaging biomarkers (IB) and computational science. This is advancing the capability to deliver “virtual biopsies” within oncology. The ability to non-invasively probe tumour biology both spatially and temporally would fulfil the potential of imaging to inform management of complex tumours; improving diagnostic accuracy, providing new insights into inter- and intra-tumoral heterogeneity and individualised treatment planning and monitoring. Soft tissue sarcomas (STS) are rare tumours of mesenchymal origin with over 150 histological subtypes and notorious heterogeneity. The combination of inter- and intra-tumoural heterogeneity and the rarity of the disease remain major barriers to effective treatments. We provide an overview of the process of successful IB development, the key imaging and computational advancements in STS including quantitative magnetic resonance imaging, radiomics and artificial intelligence, and the studies to date that have explored the potential biological surrogates to imaging metrics. We discuss the promising future directions of IBs in STS and illustrate how the routine clinical implementation of a virtual biopsy has the potential to revolutionise the management of this group of complex cancers and improve clinical outcomes.

Mapping heterogenous anisotropic tissue mechanical properties with transverse isotropic nonlinear inversion MR elastography

The white matter tracts of brain tissue consist of highly-aligned, myelinated fibers; white matter is structurally anisotropic and is expected to exhibit anisotropic mechanical behavior. In vivo mechanical properties of tissue can be imaged using magnetic resonance elastography (MRE). MRE can detect and monitor natural and disease processes that affect tissue structure; however, most MRE inversion algorithms assume locally homogenous properties and/or isotropic behavior, which can cause artifacts in white matter regions. A heterogeneous, model-based transverse isotropic implementation of a subzone-based nonlinear inversion (TI-NLI) is demonstrated. TI-NLI reconstructs accurate maps of the shear modulus, damping ratio, shear anisotropy, and tensile anisotropy of in vivo brain tissue using standard MRE motion measurements and fiber directions estimated from diffusion tensor imaging (DTI). TI-NLI accuracy was investigated with using synthetic data in both controlled and realistic settings: excellent quantitative and spatial accuracy was observed and cross-talk between estimated parameters was minimal. Ten repeated, in vivo, MRE scans acquired from a healthy subject were co-registered to demonstrate repeatability of the technique. Good resolution of anatomical structures and bilateral symmetry were evident in MRE images of all mechanical property types. Repeatability was similar to isotropic MRE methods and well within the limits required for clinical success. TI-NLI MRE is a promising new technique for clinical research into anisotropic tissues such as the brain and muscle.

Diagnostic Feasibility of Magnetic Resonance Elastography Radiomics Analysis for the Assessment of Hepatic Fibrosis in Patients With Nonalcoholic Fatty Liver Disease

OBJECTIVE

The aim of the study was to investigate the diagnostic feasibility of radiomics analysis using magnetic resonance elastography (MRE) to assess hepatic fibrosis in patients with nonalcoholic fatty liver disease (NAFLD).

METHODS

One hundred patients with suspected NAFLD were retrospectively enrolled. All patients underwent a liver parenchymal biopsy. Magnetic resonance elastography was performed using a 3.0-T scanner. After multislice segmentation of MRE images, 834 radiomic features were analyzed using a commercial program. Radiologic features, such as median and mean values of the regions of interest and variable clinical features, were analyzed. A random forest regressor was used to extract important radiomic, radiological, and clinical features. A random forest classifier model was trained to use these features to classify the fibrosis stage. The area under the receiver operating characteristic curve was evaluated using a classifier for fibrosis stage diagnosis.

RESULTS

The pathological hepatic fibrosis stage was classified as low-grade fibrosis (stages F0-F1, n = 82) or clinically significant fibrosis (stages F2-F4, n = 18). Eight important features were extracted from radiomics analysis, with the 2 most important being wavelet-high high low gray level dependence matrix dependence nonuniformity-normalized and wavelet-high high low gray level dependence matrix dependence entropy. The median value of the multiple small regions of interest was identified as the most important radiologic feature. Platelet count has been identified as an important clinical feature. The area under the receiver operating characteristic curve of the classifier using radiomics was comparable with that of radiologic measures (0.97 ± 0.07 and 0.96 ± 0.06, respectively).

CONCLUSIONS

Magnetic resonance elastography radiomics analysis provides diagnostic performance comparable with conventional MRE analysis for the assessment of clinically significant hepatic fibrosis in patients with NAFLD.

Pituitary MRI Standard and Advanced Sequences: Role in the Diagnosis and Characterization of Pituitary Adenomas

Pituitary adenomas (PAs) represent the most frequently found lesions in the sellar region; however, several other lesions may be encountered in this region, such as meningiomas, craniopharyngiomas, and aneurysms. High-quality imaging is fundamental for diagnosis, characterization, and guidance of treatment planning of PAs. Sellar magnetic resonance imaging (MRI) is considered the imaging modality of choice for the evaluation of lesions in the sella turcica. The sellar MRI standard protocol includes coronal and sagittal T1-weighted spin-echo sequencing with and without gadolinium-based contrast agent and coronal T2-weighted (T2w) fast-spin echo sequencing. A systematic MRI approach to the pituitary region generally provides information that includes the size and shape of the PA, the presence of cysts or hemorrhage within the tumor, its relationship with the optic pathways and surrounding structures, potential cavernous sinus invasion, sphenoid sinus pneumatization type, and differential diagnosis with other sellar lesions. The standard protocol is sufficient for the evaluation of most cases; however, some advanced techniques (susceptibility imaging, diffusion-weighted imaging, 3D T2w high-resolution sequences, magnetic resonance elastography, perfusion-weighted imaging) may render additional information, which may be important for some cases. In this "approach to the patient" manuscript, we will discuss the use of standard and advanced MRI sequences in the diagnosis and characterization of PAs, including MRI features associated with treatment response that may aid in presurgical evaluation and planning, and red flags that may point to an alternative diagnosis.

Intra-patient comparison of 3D and 2D magnetic resonance elastography techniques for assessment of liver stiffness

PURPOSE

To evaluate performance of 3D magnetic resonance elastography (MRE) using spin-echo echo-planar imaging (seEPI) for assessment of hepatic stiffness compared with 2D gradient-recalled echo (GRE) and 2D seEPI sequences.

METHODS

Fifty-seven liver MRE examinations including 2D GRE, 2D seEPI, and 3D seEPI sequences were retrospectively evaluated. Elastograms were analyzed by 2 radiologists and polygonal regions of interests (ROIs) were drawn in 2 different fashions: "curated" ROI (avoiding liver edge, major vessels, and areas of wave interferences) and "non-curated" ROI (including largest cross section of liver, to assess the contribution of artifacts). Liver stiffness measurement (LSM) was calculated as the arithmetic mean of individual stiffness values for each technique. For 3D MRE, LSMs were also calculated based on 4 slices ("abbreviated LSM"). Intra-patient variations in LSMs and different methods of ROI placement were assessed by univariate tests. A p-value of < 0.05 was set as a statistically significant difference.

RESULTS

Mean surface areas of the ROIs were 50,723 mm², 12,669 mm², 5814 mm², and 10,642 mm² for 3D MRE, abbreviated 3D MRE, 2D GRE, and 2D seEPI, respectively. 3D LSMs based on curated and non-curated ROIs showed no clinically significant difference, with a mean difference less than 0.1 kPa. Abbreviated 3D LSMs had excellent correlation with 3D LSMs based on all slices (r = 0.9; p < 0.001) and were not significantly different (p = 0.927).

CONCLUSION

3D MRE allows more reproducible measurements due to its lower susceptibility to artifacts and provides larger areas of parenchyma, enabling a more comprehensive evaluation of the liver.

Magnetic resonance elastography for prediction of long-term progression and outcome in chronic liver disease: A retrospective study

BACKGROUND AND AIMS

Although magnetic resonance elastography (MRE) has been well-established for detecting and staging liver fibrosis, its prognostic role in determining outcomes of chronic liver disease (CLD) is mostly unknown.

APPROACH AND RESULTS

This retrospective study consisted of 1269 subjects who underwent MRE between 2007 and 2009 and followed up until death or last known clinical encounter or end of study period. Charts were reviewed for cirrhosis development, decompensation, and transplant or death. The cohort was split into baseline noncirrhosis (group 1), compensated cirrhosis (group 2), and decompensated cirrhosis (group 3). Cox-regression analysis with age, sex, splenomegaly, CLD etiology, Child-Pugh Score (CPS), Fibrosis-4 Index (FIB-4) score, and Model for End-Stage Liver Disease (MELD)-adjusted HR for every 1-kPa increase in liver stiffness measurement (LSM) were used to assess the predictive performance of MRE on outcomes. Group 1 (n = 821) had baseline median LSM of 2.8 kPa, and cirrhosis developed in 72 (8.8%) subjects with an overall rate of about 1% cirrhosis/year. Baseline LSM predicted the future cirrhosis with multivariable adjusted HR of 2.38 (p < 0.0001) (concordance, 0.84). In group 2 (n = 277) with baseline median LSM of 5.7 kPa, 83 (30%) subjects developed decompensation. Baseline LSM predicted the future decompensation in cirrhosis with FIB-4 and MELD-adjusted HR of 1.22 (p < 0.0001) (concordance, 0.75). In group 3 (n = 171) with median baseline LSM of 6.8 kPa (5.2, 8.4), 113 (66%) subjects had either death or transplant. Baseline LSM predicted the future transplant or death with HR of 1.11 (p = 0.013) (concordance 0.53) but not in CPS and MELD-adjusted models (p = 0.08).

CONCLUSION

MRE-based LSM is independently predictive of development of future cirrhosis and decompensation, and has predictive value in future transplant/death in patients with CLD.

Evaluation of a PEGylated Fibroblast Growth Factor 21 Variant Using Novel Preclinical Magnetic Resonance Imaging and Magnetic Resonance Elastography in a Mouse Model of Nonalcoholic Steatohepatitis

Background

Treatments for nonalcoholic steatohepatitis (NASH) are urgently needed. Hepatic fat fraction and shear stiffness quantified by magnetic resonance imaging (MRI‐HFF) and magnetic resonance elastography (MRE‐SS), respectively, are biomarkers for hepatic steatosis and fibrosis.

Purpose

This study assessed the longitudinal effects of fibroblast growth factor 21 variant (polyethylene glycol [PEG]‐FGF21v) on MRI‐HFF and MRE‐SS in a NASH mouse model.

Study Type

Preclinical.

Animal Model

This study included a choline‐deficient, amino acid‐defined, high‐fat diet (CDAHFD) model and 6‐week‐old, male C57BL/6J mice (N = 78).

Field Strength/Sequence

This study was performed using: 3T: gradient‐echo two‐point Dixon and spin‐echo (SE) echo‐planar imaging elastography (200 Hz) and 7T: SE two‐point Dixon and SE elastography (200 Hz).

Assessment

MRI and MRE were performed before control diet (CD) or CDAHFD (BD), before PEG‐FGF21v dosing (baseline), and after PEG‐FGF21v treatment (WK4/8). Regions of interest for MRI‐HFF and MRE‐SS were delineated by J.L. and H.T. (>5 years of experience each). Fibrosis and steatosis were measured histologically after picrosirius red and H&E staining. Alkaline phosphatase, alanine transaminase, bile acids, and triglycerides (TGs) were measured.

Statistical Tests

Two‐tailed Dunnett's tests were used for statistical analysis; untreated CDAHFD or baseline was used for comparisons. Imaging and histology/biochemistry data were determined using Spearman correlations. Bayesian posterior distributions for MRE‐SS at WK8, posterior means, and 95% credible intervals were presented.

Results

CDAHFD significantly increased baseline MRI‐HFF (3T: 21.97% ± 0.29%; 7T: 40.12% ± 0.35%) and MRE‐SS (3T: 1.25 ± 0.02; 7T: 1.78 ± 0.06 kPa) vs. CD (3T: 3.45% ± 0.7%; 7T: 12.06% ± 1.4% and 3T: 1.01 ± 0.02; 7T: 0.89 ± 0.06 kPa). At 7T, PEG‐FGF21v significantly decreased MRI‐HFF (WK4: 28.97% ± 1.22%; WK8: 20.93% ± 1.15%) and MRE‐SS (WK4: 1.57 ± 0.04; WK8: 1.36 ± 0.05 kPa) vs. untreated (WK4: 36.36% ± 0.62%; WK8: 30.58% ± 0.81% and WK4: 2.03 ± 0.06; WK8: 2.01 ± 0.04 kPa); 3T trends were similar. WK8 SS posterior mean percent attenuation ratios (R_DI) were −68% (−90%, −44%; 3T) and −64% (−78%, −52%; 7T). MRI‐HFF was significantly correlated with H&E (3T, r = 0.93; 7T, r = 0.94) and TGs (both, r = 0.92).

Data Conclusions

MRI‐HFF and MRE‐SS showed PEG‐FGF21v effects on hepatic steatosis and fibrosis across 3 and 7T, consistent with histological and biochemical data.

Level of Evidence

1

Technical Efficacy Stage

2

Performance of C-SENSE Accelerated Rapid Liver Shear Stiffness Measurement Using Displacement Wave Polarity-Inversion Motion Encoding: An Evaluation Study

BACKGROUND

Liver shear stiffness measurement using magnetic resonance elastography (MRE) aids in the noninvasive diagnosis and staging of liver fibrosis. Inadequate breath-holds can lead to inaccurate stiffness estimation and/or failed MRE exams.

PURPOSE

To prospectively evaluate the performance of compressed sensitivity encoding (C-SENSE) accelerated rapid MRE measurement of liver shear stiffness using displacement wave polarity-inversion motion encoding.

STUDY TYPE

Retrospective.

SUBJECTS

Eleven with liver disease and 10 asymptomatic subjects.

FIELD STRENGTH/SEQUENCE

1.5 T; gradient-recalled-echo (GRE) MRE.

ASSESSMENT

All participants underwent: 1) two-dimensional (2D) GRE MRE with inflow saturation using SENSE acceleration factor (R) of 2 (standard of care [SC]); 2) 2D rapid MRE with (RwS); and 3) without (RnS) inflow saturation using C-SENSE R = 3; and 4) spatial three-dimensional (3D) rapid MRE with inflow saturation (R3D) using C-SENSE R = 4; with nominally identical spatial resolution and coverage. Image analyst (D.G., 2 years of experience) drew identical and maximal regions of interest (ROIs) in right hepatic lobe.

STATISTICAL TESTS

Linear regression, intra-class correlation coefficients (ICC), Bland-Altman analyses, and the Wilcoxon signed-rank test were used to assess consistency and agreement of liver stiffness measurements for manually drawn identical and maximal ROIs.

RESULTS

In 21 participants (37 ± 14 years) with liver stiffness (2.3 ± 0.7 kPa), body mass index (BMI 27 ± 7 kg/m² ), proton density fat fraction (PDFF 9 ± 9%), and T₂ * (27 ± 4 msec); rapid MRE sequences showed excellent agreement (ICC > 0.95) with SC MRE and no correlation (r²  < 0.1) of the differences (mean difference <0.2 kPa, <6%; limits of agreement <0.4 kPa, <16%) with BMI, PDFF, and T₂ *. Breath-hold times were: 14 seconds (SC), 5 seconds (RnS), 7 seconds (RwS) per slice, and 16 seconds for the R3D acquisition.

DATA CONCLUSIONS

C-SENSE accelerated GRE MRE sequences, using displacement wave polarity-inversion motion encoding, produce equivalent measurements of liver stiffness and have potential clinical benefit in patients with limited breath-holding capacity.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 1.

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.

OUP accepted manuscript

Background

This study aimed to assess the performance of transient elastography (TE), two-dimensional shear wave elastography (2D-SWE), and magnetic resonance elastography (MRE) for staging significant fibrosis and cirrhosis in untreated chronic hepatitis B (CHB) patients.

Methods

Pubmed, Embase, Web of Science, and Cochrane Library were searched for terms involving CHB, TE, 2D-SWE, and MRE. Other etiologies of chronic liver disease, previous treatment in patients, or articles not published in SCI journals were excluded. Hierarchical non-linear models were used to evaluate the diagnostic accuracy of TE, 2D-SWE, and MRE. Heterogeneity was explored via analysis of threshold effect and meta-regression.

Results

Twenty-eight articles with a total of 4,540 untreated CHB patients were included. The summary areas under the receiver-operating characteristic curves (AUROCs) using TE, 2D-SWE, and MRE for predicting significant fibrosis (SF) were 0.84, 0.89, and 0.99, respectively. The AUROC values of TE, 2D-SWE, and MRE for staging cirrhosis were 0.9, 0.94, and 0.99, respectively. Based on the meta-analysis of studies with head-to-head comparison, 2D-SWE is superior to TE (0.92 vs 0.85, P < 0.01) in staging significant fibrosis.

Conclusion

TE, 2D-SWE, and MRE express acceptable diagnostic accuracies in staging significant fibrosis and cirrhosis in untreated CHB patients. 2D-SWE outperforms TE in detecting significant fibrosis in treatment-naive people with hepatitis B virus.

Brazilian Society of Hepatology and Brazilian College of Radiology practice guidance for the use of elastography in liver diseases

In 2015 the European Association for the Study of Liver Diseases (EASL) and the Asociación Latinoamericana para el Estudio del Hígado (ALEH) published a guideline for the use of non-invasive markers of liver disease. At that time, this guideline focused on the available data regarding ultrasonic-related elastography methods. Since then, much has been published, including new data about XL probe use in transient elastography, magnetic resonance elastography, and non-invasive liver steatosis evaluation. In order to draw evidence-based guidance concerning the use of elastography for non-invasive assessment of fibrosis and steatosis in different chronic liver diseases, the Brazilian Society of Hepatology (SBH) and the Brazilian College of Radiology (CBR) sponsored a single-topic meeting on October 4th, 2019, at São Paulo, Brazil. The aim was to establish specific recommendations regarding the use of imaging-related non-invasive technology to diagnose liver fibrosis and steatosis based on the discussion of evidence-based topics by an organizing committee of experts. It was submitted online to all SBH and CBR members. The present document is the final version of the manuscript that supports the use of this new technology as an alternative to liver biopsy.

The Fontan Pathway: Change in Dimension and Catheter-Based Intervention over Time

An unobstructed Fontan pathway is essential for optimal hemodynamics. We hypothesize that more extracardiac conduit (ECC) Fontan pathways develop obstruction compared to lateral tunnel (LT) Fontans and that the dilation typically observed in LTs results in similar mid-term clinical outcomes. A single-center, retrospective study was done including all Fontan cardiac catheterizations from 2006 to 2019. Angiography and medical records were reviewed to define Fontan pathway dimensions, interventions, and clinical outcomes. 232 patients underwent cardiac catheterization, where 60% were ECCs and 30% LTs. The minimum cross-sectional area (CSA) of ECCs was significantly smaller than LTs and LTs dilated over time. 13% of patients had Fontan pathway stenting at a median age of 16.2 years. The minimum CSA for patients who underwent intervention was significantly smaller than patients who did not. Lower weight at Fontan surgery was associated with intervention on the Fontan pathway, with a threshold weight of 15 kg for patients with an ECC. The median follow-up was 3.3 years. Patients who had Fontan pathway intervention were not more likely to experience the composite adverse clinical outcome. LTs were more likely than ECCs to have worse clinical outcome, when liver fibrosis was included. This is the first study to describe angiographic dimensions of the Fontan pathway in a large number of patients over time. ECCs tend to become stenotic. Lower weight at Fontan surgery is a potential risk for Fontan pathway intervention. LTs may experience worse clinical outcomes in follow-up. This information can help inform the optimal timing and method of post-Fontan surveillance.

Clinical utility of 3D magnetic resonance elastography in patients with biliary obstruction

OBJECTIVES

Three-dimensional magnetic resonance elastography (3D-MRE) allows for multiparametric modeling of both elastic and viscous tissue characteristics. Our aim was to compare 3D-MRE with conventional liver shear stiffness assessment in gauging obstructive jaundice (OJ), predicting the adequacy of biliary decompression after drainage, and discriminating OJ from liver fibrosis.

METHODS

Patients with no histories of liver disease (n = 201) were studied in retrospect, grouped by bilirubin levels as no jaundice (NJ ≤ 2 mg/dL; n = 75), mild OJ (>2 mg/dL and ≤ 4 mg/dL; n = 56), and severe OJ (> 4 mg/dL; n = 70). For comparison, another 75 patients with chronic hepatitis B and C infections and histologically proven liver fibrosis were similarly analyzed. Each patient underwent spin-echo echo-planar-imaging MRE at 60 Hz with 3D wave postprocessing. Logistic regression and ordinary regression models were used to compare the 3D-MRE model with liver shear stiffness.

RESULTS

Liver shear stiffness, loss modulus, and damping ratio were incorporated into a 3D-MRE model, which significantly outperformed shear stiffness in predicting OJ severity (accuracy: 0.801 vs 0.672; p < 0.001). Both the 3D-MRE model and liver shear stiffness performed equally well in predicting the outcome of biliary drainage procedure (C-statistics: 0.852 vs 0.847; p = 0.48). The 3D-MRE model also demonstrated significantly better C-statistics than that of liver shear stiffness in discriminating mild OJ from F1-F2 liver fibrosis (0.765 vs 0.641; p = 0.005) and severe OJ from F3-F4 liver fibrosis (0.750 vs 0.635; p = 0.031).

CONCLUSIONS

3D-MRE is an innovative imaging method for gauging OJ severity, predicting the outcome of biliary drainage procedure, and discriminating OJ from liver fibrosis.

KEY POINTS

• 3D-MR elastography achieved promising results for predicting the severity of obstructive jaundice. • Advanced parameters of 3D-MR elastography demonstrated significantly better performance than that of shear stiffness of 2D-MR elastography in discriminating obstructive jaundice from liver fibrosis caused by chronic hepatitis B/C. • Both 3D-MR elastography and 2D-MR elastography were equivalent in predicting the outcome of biliary drainage procedure.

Randomised clinical trial: semaglutide versus placebo reduced liver steatosis but not liver stiffness in subjects with non-alcoholic fatty liver disease assessed by magnetic resonance imaging

BACKGROUND

Glucagon-like peptide-1 receptor agonists may be a treatment option in patients with non-alcoholic fatty liver disease (NAFLD).

AIMS

To investigate the effects of semaglutide on liver stiffness and liver fat in subjects with NAFLD using non-invasive magnetic resonance imaging (MRI) methods.

METHODS

This randomised, double-blind, placebo-controlled trial enrolled subjects with liver stiffness 2.50-4.63 kPa by magnetic resonance elastography (MRE) and liver steatosis ≥10% by MRI proton density fat fraction (MRI-PDFF). The primary endpoint was change from baseline to week 48 in liver stiffness assessed by MRE.

RESULTS

Sixty-seven subjects were randomised to once-daily subcutaneous semaglutide 0.4 mg (n = 34) or placebo (n = 33). Change from baseline in liver stiffness was not significantly different between semaglutide and placebo at week 48 (estimated treatment ratio 0.96 (95% CI 0.89, 1.03; P = 0.2798); significant differences in liver stiffness were not observed at weeks 24 or 72. Reductions in liver steatosis were significantly greater with semaglutide (estimated treatment ratios: 0.70 [0.59, 0.84], P = 0.0002; 0.47 [0.36, 0.60], P < 0.0001; and 0.50 [0.39, 0.66], P < 0.0001) and more subjects achieved a ≥ 30% reduction in liver fat content with semaglutide at weeks 24, 48 and 72, (all P < 0.001). Decreases in liver enzymes, body weight and HbA_1c were also observed with semaglutide.

CONCLUSIONS

The change in liver stiffness in subjects with NAFLD was not significantly different between semaglutide and placebo. However, semaglutide significantly reduced liver steatosis compared with placebo which, together with improvements in liver enzymes and metabolic parameters, suggests a positive impact on disease activity and metabolic profile. ClinicalTrials.gov identifier: NCT03357380.

Synthetic extracellular volume fraction without hematocrit sampling for hepatic applications

Purpose

Calculation of extracellular volume fraction (ECV) currently receives increasing interest as a potential biomarker for non-invasive assessment of liver fibrosis. ECV calculation requires hematocrit (Hct) sampling, which might be difficult to obtain in a high-throughput radiology department. The aim of this study was to generate synthetic ECV for hepatic applications without the need for Hct sampling.

Methods

In this prospective study participants underwent liver MRI. T1 mapping was performed before and after contrast administration. Blood Hct was obtained prior to MRI. We hypothesized that the relationship between Hct and longitudinal relaxation rate of blood (R1 = 1/T1_blood) could be calibrated and used to generate the equation for synthetic Htc and ECV calculation. Conventional and synthetic ECV were calculated. Pearson correlation, linear regression and Bland–Altman method were used for statistical analysis.

Results

180 consecutive patients were divided into derivation (n = 90) and validation (n = 90) cohorts. In the derivation cohort, native R1_blood and Hct showed a linear relationship (Hct_MOLLI = 98.04 × (1/T1_blood) − 33.17, R² = 0.75, P < 0.001), which was used to calculate synthetic ECV in the validation and whole study cohorts. Synthetic and conventional ECV showed significant correlations in the derivation, validation and in the whole study cohorts (r = 0.99, 0.97 and 0.99, respectively, P < 0.001, respectively) with minimal bias according to the Bland–Altman analysis.

Conclusion

Synthetic ECV seems to offer an alternative method for non-invasive quantification of the hepatic ECV. It may potentially overcome an important barrier to clinical implementation of ECV and thus, enable broader use of hepatic ECV in routine clinical practice.

Multiparametric magnetic resonance imaging/magnetic resonance elastography assesses progression and regression of steatosis, inflammation, and fibrosis in alcohol-associated liver disease

BACKGROUND

Magnetic resonance imaging (MRI) and MRI-based elastography (MRE) are the most promising noninvasive techniques in assessing liver diseases. The purpose of this study was to evaluate an advanced multiparametric imaging method for staging disease and assessing treatment response in realistic preclinical alcohol-associated liver disease (ALD).

METHODS

We utilized four different preclinical mouse models in our study: Model 1-mice were fed a fast-food diet and fructose water for 48 weeks to induce nonalcoholic fatty liver disease; Model 2-mice were fed chronic-binge ethanol (EtOH) for 10 days or 8 weeks to induce liver steatosis/inflammation. Two groups of mice were treated with interleukin-22 at different time points to induce disease regression; Model 3-mice were administered CCl4 for 2 to 4 weeks to establish liver fibrosis followed by 2 or 4 weeks of recovery; and Model 4-mice were administered EtOH plus CCl4 for 12 weeks. Mouse liver imaging biomarkers including proton density fat fraction (PDFF), liver stiffness (LS), loss modulus (LM), and damping ratio (DR) were assessed. Liver and serum samples were obtained for histologic and biochemical analyses. Ordinal logistic regression and generalized linear regression analyses were used to model the severity of steatosis, inflammation, and fibrosis, and to assess the regression of these conditions.

RESULTS

Multiparametric models with combinations of biomarkers (LS, LM, DR, and PDFF) used noninvasively to predict the histologic severity and regression of steatosis, inflammation, and fibrosis were highly accurate (area under the curve > 0.84 for all). A three-parameter model that incorporates LS, DR, and ALT predicted histologic fibrosis progression (r = 0.84, p < 0.0001) and regression (r = 0.79, p < 0.0001) as measured by collagen content in livers.

CONCLUSION

This preclinical study provides evidence that multiparametric MRI/MRE can be used noninvasively to assess disease severity and monitor treatment response in ALD.

Non-Invasive Assessment of Liver Fibrosis and Steatosis in End-Stage Renal Disease Patients Undergoing Renal Transplant Evaluation

Background

Non-alcoholic fatty liver disease (NAFLD) has an increased prevalence in end-stage renal disease (ESRD) due to similar risk factors. The aim of this study was to assess non-invasive testing including transient elastography (TE) for liver stiffness (LS), controlled attenuated parameter (CAP) for steatosis, Fibrosis-4 (FIB-4) score, aspartate aminotransferase (AST) to platelet ratio index (APRI) and NAFLD fibrosis score (NFS), for evaluation of NAFLD along with advanced fibrosis (AF) in patients with ESRD undergoing renal transplant evaluation.

Methods

Data were retrospectively collected within 12 weeks of TE. Primary outcomes were AF, defined by LS ≥ 9 kPa compared to APRI > 1.5, FIB-4 > 2.67, and NFS of 0.675, and ≥ 5% steatosis by CAP ≥ 263 dB/m compared to liver histology when available.

Results

A total of 171 patients were evaluated: mean age 56, 65% male, 36% obese, 47% had diabetes, 96% hypertension, and 56% dyslipidemia. Mean LS was 6.5 kPa with 21% having AF. Mean CAP was 232 dB/m, with 25% having steatosis. Those with AF were older with higher NFS. Those with steatosis were obese and had diabetes without higher LS or fibrosis scores. Only NFS was associated with LS ≥ 9 kPa. In those with liver histology, AF was associated with LS ≥ 9 kPa but not with APRI, FIB-4, or NFS.

Conclusions

Despite normal liver enzymes, non-invasive assessment via TE in ESRD patients exhibited high prevalence of AF and steatosis not detected by APRI or FIB-4 scores. This high prevalence was secondary to the common risk factors such as obesity and diabetes, among patients with NAFLD and ESRD.

The Advance of Magnetic Resonance Elastography in Tumor Diagnosis

The change in tissue stiffness caused by pathological changes in the tissue's structure could be detected earlier, prior to the manifestation of their clinical features. Magnetic resonance elastography (MRE) is a noninvasive imaging technique that uses low-frequency vibrations to quantitatively measure the elasticity or stiffness of tissues. In tumor tissue, stiffness is directly related to tumor development, invasion, metastasis, and chemoradiotherapy resistance. It also dictates the choice of surgical method. At present, MRE is widely used in assessing different human organs, such as the liver, brain, breast, prostate, uterus, gallbladder, and colon stiffness. In the field of oncology, MRE's value lies in tumor diagnosis (especially early diagnosis), selection of treatment method, and prognosis evaluation. This article summarizes the principle of MRE and its research and application progress in tumor diagnosis and treatment.

MR elastography in patients with suspected diffuse liver disease at 1.5T: Intraindividual comparison of gradient-recalled echo versus spin-echo echo-planar imaging sequences and investigation of potential confounding factors

PURPOSE

To compare liver stiffness (LS) in patients with suspected diffuse liver disease between gradient-recalled-echo magnetic resonance elastography (GRE-MRE) and different spin-echo echo-planar imaging (SE-EPI-MRE) sequences and to investigate confounding factors including fat, iron, age, and sex.

METHOD

LS was measured at 1.5T using GRE-MRE, SE-EPI-MRE and short-TE-SE-EPI-MRE (hiSE-EPI-MRE) sequences and compared using Bland-Altman-plots together with concordance correlation coefficients (CCC). Success gradings were evaluated considering possible confounding factors.

RESULTS

305 patients (225 male, 80 females, mean age 51.12 years) were included. 109/305 showed hepatic iron overload, 183 hepatic steatosis. The mean difference (bias) in stiffness values between GRE-MRE and SE-EPI-MRE/hiSE-EPI-MRE was 0.15/0.2 kPa (LOA: -0.72,0.41 kPa/-0.94,0.55 kPa), between SE-EPI-MRE and hiSE-EPI-MRE 0.04 kPa (LOA: -0.62,0.53 kPa). The CCC for agreement between stiffness values for GRE-MRE and SE-EPI-MRE was 0.94 (0.92-0.95), 0.89 (0.86-0.91) for hiSE-EPI-MRE and GRE-MRE and 0.94 (0.92-0.95) for SE-EPI-MRE and hiSE-EPI-MRE. Using GRE-MRE, 72/305 showed unusable results whereby all these patients had high iron levels (mean R2*=209.7 1/s). For SE-EPI-MRE and hiSE-EPI-MRE only 10/305 and 8/305 were inconclusive respectively, corresponding to a significantly higher iron load (mean R2*= 549.2 1/s for SE-EPI-MRE and 570.7 1/s for hiSE-EPI-MRE). Concerning fat, age or sex no significant influence on success was observed for all sequences.

CONCLUSIONS

Good agreement of LS values was observed between GRE-MRE and SE-EPI-MRE sequences. The number of successful exams, however, was considerably lower for GRE-MRE, mainly due to iron content. Study reference number: AN5093.