Dynamic contrast-enhanced magnetic resonance imaging with Gd-EOB-DTPA for the evaluation of liver fibrosis in chronic hepatitis patients

Advances in Noninvasive Molecular Imaging Probes for Liver Fibrosis Diagnosis

Liver fibrosis is a wound-healing response to chronic liver injury, which may lead to cirrhosis and cancer. Early-stage fibrosis is reversible, and it is difficult to precisely diagnose with conventional imaging modalities such as magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, and ultrasound imaging. In contrast, probe-assisted molecular imaging offers a promising noninvasive approach to visualize early fibrosis changes in vivo, thus facilitating early diagnosis and staging liver fibrosis, and even monitoring of the treatment response. Here, the most recent progress in molecular imaging technologies for liver fibrosis is updated. We start by illustrating pathogenesis for liver fibrosis, which includes capillarization of liver sinusoidal endothelial cells, cellular and molecular processes involved in inflammation and fibrogenesis, as well as processes of collagen synthesis, oxidation, and cross-linking. Furthermore, the biological targets used in molecular imaging of liver fibrosis are summarized, which are composed of receptors on hepatic stellate cells, macrophages, and even liver collagen. Notably, the focus is on insights into the advances in imaging modalities developed for liver fibrosis diagnosis and the update in the corresponding contrast agents. In addition, challenges and opportunities for future research and clinical translation of the molecular imaging modalities and the contrast agents are pointed out. We hope that this review would serve as a guide for scientists and students who are interested in liver fibrosis imaging and treatment, and as well expedite the translation of molecular imaging technologies from bench to bedside.

Intravoxel incoherent motion assessment of liver fibrosis staging in MASLD

PURPOSE

Partial correlation analysis was performed to account for the interference of steatosis changes and inflammatory factors, to determine the true correlation between fibrosis and IVIM parameters (Dfast, Dslow, and F), and to evaluate the diagnostic efficacy of IVIM for liver fibrosis.

METHODS

A total of 106 patients with metabolic dysfunction-associated steatotic liver disease (MASLD) examined by IVIM from November 2016 to November 2023 at our hospital were retrospectively included. Preliminary analysis of each IVIM parameter and correlations with pathological findings were performed using Spearman correlation analysis, and partial correlation analysis was used to exclude the interference of other pathological factors, thus yielding the true correlations between IVIM parameters (Dfast, Dslow, and F) and pathology. The diagnostic efficacy of IVIM parameters for diagnosing MASLD was assessed via receiver operating characteristic (ROC) curve analysis.

RESULTS

Spearman correlation analysis of all the IVIM parameters revealed correlations with steatosis, lobular inflammation, and ballooning. Partial correlation analysis indicated that Dfast was correlated with the pathological fibrosis stage (r = - 0.593, P < 0.001), Dslow was correlated with the pathological steatosis score (r = - 0.313, P < 0.05), and F was correlated with the pathological fibrosis stage and steatosis score (r = - 0.456 and 0.255, P < 0.001 and P < 0.05). In the diagnosis of hepatic fibrosis, significant hepatic fibrosis, advanced liver fibrosis and cirrhosis, Dfast achieved areas under the ROC curve of 0.763, 0.801, 0.853, and 0.897, respectively. The threshold values for diagnosing different fibrosis stages using Dfast (10-3 mm2/s) were 57.613, 54.587, 52.714, and 51.978, respectively.

CONCLUSION

According to our partial correlation analysis, there was a moderate correlation between Dfast and F according to fibrosis stage, and Dfast was not influenced by inflammation or steatosis when diagnosing fibrosis in MASLD patients. A relatively close Dfast threshold is insufficient for accurately and noninvasively assessing various stages of MASLD fibrosis. In clinical practice, this approach can be considered an alternative method for the preliminary assessment of fibrosis in MASLD patients.

This Is What Metabolic Dysfunction-Associated Steatotic Liver Disease Looks Like: Potential of a Multiparametric MRI Protocol

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent condition with a broad spectrum defined by liver biopsy. This gold standard method evaluates three features: steatosis, activity (ballooning and lobular inflammation), and fibrosis, attributing them to certain grades or stages using a semiquantitative scoring system. However, liver biopsy is subject to numerous restrictions, creating an unmet need for a reliable and reproducible method for MASLD assessment, grading, and staging. Noninvasive imaging modalities, such as magnetic resonance imaging (MRI), offer the potential to assess quantitative liver parameters. This review aims to provide an overview of the available MRI techniques for the three criteria evaluated individually by liver histology. Here, we discuss the possibility of combining multiple MRI parameters to replace liver biopsy with a holistic, multiparametric MRI protocol. In conclusion, the development and implementation of such an approach could significantly improve the diagnosis and management of MASLD, reducing the need for invasive procedures and paving the way for more personalized treatment strategies.

Pathophysiologic Mapping of Chronic Liver Diseases With Longitudinal Multiparametric MRI in Animal Models

OBJECTIVES

Chronic liver diseases (CLDs) have diverse etiologies. To better classify CLDs, we explored the ability of longitudinal multiparametric MRI (magnetic resonance imaging) in depicting alterations in liver morphology, inflammation, and hepatocyte and macrophage activity in murine high-fat diet (HFD)- and carbon tetrachloride (CCl4)-induced CLD models.

MATERIALS AND METHODS

Mice were either untreated, fed an HFD for 24 weeks, or injected with CCl4 for 8 weeks. Longitudinal multiparametric MRI was performed every 4 weeks using a 7 T MRI scanner, including T1/T2 relaxometry, morphological T1/T2-weighted imaging, and fat-selective imaging. Diffusion-weighted imaging was applied to assess fibrotic remodeling and T1-weighted and T2*-weighted dynamic contrast-enhanced MRI and dynamic susceptibility contrast MRI using gadoxetic acid and ferucarbotran to target hepatocytes and the mononuclear phagocyte system, respectively. Imaging data were associated with histopathological and serological analyses. Principal component analysis and clustering were used to reveal underlying disease patterns.

RESULTS

The MRI parameters significantly correlated with histologically confirmed steatosis, fibrosis, and liver damage, with varying importance. No single MRI parameter exclusively correlated with 1 pathophysiological feature, underscoring the necessity for using parameter patterns. Clustering revealed early-stage, model-specific patterns. Although the HFD model exhibited pronounced liver fat content and fibrosis, the CCl4 model indicated reduced liver fat content and impaired hepatocyte and macrophage function. In both models, MRI biomarkers of inflammation were elevated.

CONCLUSIONS

Multiparametric MRI patterns can be assigned to pathophysiological processes and used for murine CLD classification and progression tracking. These MRI biomarker patterns can directly be explored clinically to improve early CLD detection and differentiation and to refine treatments.

Perfusion MR Imaging of Liver: Principles and Clinical Applications

Perfusion imaging techniques provide quantitative characterization of tissue microvasculature. Perfusion MR of liver is particularly challenging because of dual afferent flow, need for large organ high-resolution coverage, and significant movement with respiration. The most common MR technique used for quantifying liver perfusion is dynamic contrast-enhanced MR imaging. Here, the authors describe the various perfusion MR models of the liver, the basic concepts behind implementing a perfusion acquisition, and clinical results that have been obtained using these models.

Conventional and artificial intelligence-based computed tomography and magnetic resonance imaging quantitative techniques for non-invasive liver fibrosis staging

Chronic liver disease (CLD) ultimately develops into liver fibrosis and cirrhosis and is a major public health problem globally. The assessment of liver fibrosis is important for patients with CLD for prognostication, treatment decisions, and surveillance. Liver biopsies are traditionally performed to determine the stage of liver fibrosis. However, the risks of complications and technical limitations restrict their application to screening and sequential monitoring in clinical practice. CT and MRI are essential for evaluating cirrhosis-associated complications in patients with CLD, and several non-invasive methods based on them have been proposed. Artificial intelligence (AI) techniques have also been applied to stage liver fibrosis. This review aimed to explore the values of conventional and AI-based CT and MRI quantitative techniques for non-invasive liver fibrosis staging and summarized their diagnostic performance, advantages, and limitations.

Role of Functional MRI in Liver SBRT: Current Use and Future Directions

Stereotactic body radiation therapy (SBRT) is an emerging treatment for liver cancers whereby large doses of radiation can be delivered precisely to target lesions in 3-5 fractions. The target dose is limited by the dose that can be safely delivered to the non-tumour liver, which depends on the baseline liver functional reserve. Current liver SBRT guidelines assume uniform liver function in the non-tumour liver. However, the assumption of uniform liver function is false in liver disease due to the presence of cirrhosis, damage due to previous chemo- or ablative therapies or irradiation, and fatty liver disease. Anatomical information from magnetic resonance imaging (MRI) is increasingly being used for SBRT planning. While its current use is limited to the identification of target location and size, functional MRI techniques also offer the ability to quantify and spatially map liver tissue microstructure and function. This review summarises and discusses the advantages offered by functional MRI methods for SBRT treatment planning and the potential for adaptive SBRT workflows.

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.

Quantitative Functional Evaluation of Liver Fibrosis in Mice with Dynamic Contrast-enhanced Photoacoustic Imaging

Background Dynamic contrast-enhanced (DCE) photoacoustic (PA) imaging (PAI) is a novel noninvasive imaging modality that uses the differences in optical absorption of oxyhemoglobin and deoxyhemoglobin and may be performed in a dynamic fashion to image the indocyanine green (ICG) pharmacokinetics in the liver. Purpose To determine whether DCE PAI parameters (maximum peak time [T_max] and half-life [T_1/2]) derived from the PA liver function curve correlate with fibrosis determined using histopathologic analysis. Materials and Methods Between June 2020 and October 2020, 28 male mice aged 8 weeks were intraperitoneally injected with carbon tetrachloride solution every 2 days to establish a liver fibrosis model. At the 1st, 4th, and 8th week of modeling, the changes in liver structure were monitored dynamically by using a PA technique. The T_max and T_1/2 of ICG were calculated at different pathologic stages and within a control group. Corresponding liver histopathologic results and blood biochemical data were obtained. Spearman rank correlation was used to evaluate the relationship between the DCE PAI results and histologic scores. Results The PA liver function curve showed that the T_max and T_1/2 varied among groups (mean T_max: control group, 9 seconds ± 1.8 [standard deviation]; 1 week, 51 seconds ± 4.4; 4 weeks, 73 seconds ± 5.3; 8 weeks, 104 seconds ± 6.6; P < .001) (mean T_1/2: control group, 28 seconds ± 6.5; 1 week, 201 seconds ± 12.4; 4 weeks, 285 seconds ± 11; 8 weeks, 318 seconds ± 30.5; P < .001). There was a positive correlation between the dynamic parameters (T_max and T_1/2) and the histopathologic scores; the Spearman ρ ratios for the Sirius red and α-smooth muscle actin (αSMA)-positive areas versus the T_max were 0.93 and 0.94 (P < .001 for both), and the Spearman ρ ratios for the Sirius red and αSMA-positive areas versus T_1/2 were 0.87 and 0.89 (P < .001 for both). Conclusion Dynamic contrast-enhanced photoacoustic imaging demonstrated a higher maximum peak time and half-life in mice with induced fibrosis compared with control mice without fibrosis, and these values correlated with histologic measures of fibrosis. © RSNA, 2021 Online supplemental material is available for this article.

Magnetic resonance quantitative susceptibility mapping in the evaluation of hepatic fibrosis in chronic liver disease: a feasibility study

Background

Noninvasive methods for the early diagnosis and staging of hepatic fibrosis are needed. The present study aimed to investigate the alteration of magnetic susceptibility in the liver of patients with various fibrosis stages and to evaluate the feasibility of using susceptibility to stage hepatic fibrosis.

Methods

A total of 30 consecutive patients with chronic liver diseases (CLDs) underwent magnetic resonance imaging (MRI) and liver biopsy evaluation of hepatic fibrosis, necroinflammatory activity, iron load, and steatosis. Quantitative susceptibility mapping (QSM), R2* and proton density fat fraction (PDFF) images were postprocessed from the same gradient-echo data for quantitative tissue characterization using region of interest (ROI) analysis. The differences for MRI measurements between cohorts of non-significant (Ishak-F <3) and significant fibrosis (Ishak-F ≥3) and the correlation of MRI measurements with fibrosis stages and necroinflammatory activity grades were tested. Receiver operating characteristic (ROC) analysis was also performed.

Results

There was a significant difference in liver susceptibility between the cohorts of significant and non-significant fibrosis (Z=-2.880, P=0.004). A moderate negative correlation between the stages of liver fibrosis and liver susceptibility was observed (r=-0.471, P=0.015). Liver magnetic susceptibility differentiated non-significant from significant hepatic fibrosis with an area under the receiver operating curve (AUC) of 0.836 (P=0.004). A highly sensitive diagnostic performance with an AUC of 0.933 was obtained using magnetic susceptibility and PDFF together (P<0.001).

Conclusions

A noninvasive liver QSM-based evaluation promises an accurate assessment of significant fibrosis in patients with CLDs.

Quantitative T2 mapping of rats with chronic hepatitis

The aim of the study was to explore the diagnostic value of T2 mapping in an experimental rat model of chronic liver disease. Chronic hepatitis was induced in Sprague-Dawley male rats (n=88) by intraperitoneal and abdominal subcutaneous injection of carbon tetrachloride in olive oil. The normal control rats (n=12) were similarly injected with the same dose of normal saline. All rats were randomly selected and subjected to T2-weighted/spectral adiabatic inversion recovery and multiple gradient- and spin-echo sequence. After scanning, rats were sacrificed immediately and livers removed for staining with hematoxylin and eosin, as well as Masson's trichrome, to determine the pathological stage of hepatic fibrosis, necroinflammatory activity and steatosis. The T2 values were measured and associated with histopathological findings. The T2 values were significantly associated with hepatic fibrosis (P<0.05), but not with hepatitis (P>0.05) or steatosis (P>0.05). By partial correlation analysis, a significant positive correlation was observed between the T2 values and stages of liver fibrosis (r=0.820; P<0.05). T2 values increased with progressive hepatic fibrosis. The differences between T2 values and stages of liver fibrosis were statistically significant. Statistically significant differences were observed between different stages of liver fibrosis (P<0.05), with an area under the curve value of 0.944 for predicting stage F1 or greater, 0.942 for stage F2 or greater, 0.958 for stage F3 or greater, and 0.948 for F4. Thus, the T2 value is one of the quantitative indices of imaging and accurately reflects the stages of liver fibrosis.

Evaluation of liver function using liver parenchyma, spleen and portal vein signal intensities during the hepatobiliary phase in Gd-EOB-D TPA-enhanced MRI

Background

Previous studies have used signal intensity (SI) to reflect liver function. However, few studies have evaluated liver function via the portal vein. Regarding the SI of the liver, spleen, and portal vein, no study has indicated which can best reflect liver function. Therefore, the aim of this study is to investigate whether these parameters can evaluate liver function in patients with cirrhosis and determine which is the best parameter.

Methods

120 patients with normal livers (n = 41) or Child–Pugh class A (n = 50), B (n = 21) or C (n = 8) disease who had undergone Gd-EOB-DTPA-enhanced MRI were retrospectively reviewed. Comparisons of the MRI data (liver parenchyma SI, portal vein SI, and spleen SI and liver-to-portal vein contrast ratio (LPC), liver-to-spleen contrast ratio (LSC), and portal vein-to-spleen contrast ratio (PSC)) in the 15-min hepatobiliary phase images were performed among the groups, and the correlations among the liver function parameters (total bilirubin, direct bilirubin, indirect bilirubin, aspartate aminotransferase, alanine aminotransferase, albumin, creatinine, platelet count, prothrombin time and international normalized ratio), liver function scores and MRI data were also quantitatively analysed.

Results

Significant differences were observed in the liver parenchyma SI, LPC and LSC among the groups. These values all decreased gradually from normal livers to Child–Pugh class C cirrhotic livers (P < 0.001). The portal vein SI constantly and slightly increased from normal livers to Child–Pugh class C cirrhotic livers, but no differences were found among the groups in the portal vein SI and PSC (P > 0.05). LPC showed a stronger correlation with the Child–Pugh score and MELD score than LSC and the liver parenchyma SI. The order of the AUCs of these parameters, from largest to smallest, was as follows: LPC, LSC, and liver parenchyma SI (P > 0.05).

Conclusion

The liver parenchyma SI, LSC and LPC may be used as alternative imaging biomarkers to assess liver function, while the portal vein SI and PSC do not reflect liver function. Furthermore, LPC values can more effectively distinguish severity among patients with cirrhosis than the liver parenchyma SI and LSC.

ACR Appropriateness Criteria® Chronic Liver Disease

The liver fibrosis stage is the most important clinical determinate of morbidity and mortality in patients with chronic liver diseases. With newer therapies, liver fibrosis can be stabilized and possibly reversed, thus accurate diagnosis and staging of liver fibrosis are clinically important. Ultrasound, CT, and conventional MRI can be used to establish the diagnosis of advanced fibrosis/cirrhosis but have limited utility for assessing earlier stages of fibrosis. Elastography-based ultrasound and MRI techniques are more useful for assessment of precirrhotic hepatic fibrosis. In patients with advanced fibrosis at risk for hepatocellular carcinoma (HCC), ultrasound is the surveillance modality recommended by international guidelines in nearly all circumstances. However, in patients in whom ultrasound does not assess the liver well, including those with severe steatosis or obesity, multiphase CT or MRI may have a role in surveillance for HCC. Both multiphase CT and MRI can be used for continued surveillance in patients with a history of HCC, and contrast-enhanced ultrasound may have an emerging role in this setting. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Gd-EOB-DTPA-enhanced MRI T1 relaxometry as an imaging-based liver function test compared with 13C-methacetin breath test

Background

Gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) can be used as an imaging-based liver function test. This study aims to further corroborate its validity.

Purpose

To compare Gd-EOB-DTPA-enhanced MRI as an imaging-based liver function test with the 13C-methacetin breath test.

Material and Methods

Fifty-three patients who underwent Gd-EOB-DTPA-enhanced MRI T1 relaxometry before and 20 min after intravenous Gd-EOB-DTPA administration as well as a 13C-methacetin breath test (LiMAx test) were retrospectively analyzed. T1 relaxation times of liver parenchyma, total liver volume (TLV), and functional liver volume (FLV) were determined. Pearson correlations, multiple linear regression analysis, and receiver operating characteristic curve analysis were performed with indices derived from T1 relaxometry, liver volumetry, and laboratory parameters to identify the best predictor of liver function as determined by the LiMAx test.

Results

T1 reduction rate (T1 RR), T1 RR × TLV, T1 RR × FLV, and T1 relaxation time 20 min after intravenous Gd-EOB administration showed a statistically significant correlation with LiMAx and discriminatory capacity between patients with LiMAx of > and < 315 µg/kg/h. Of the indices investigated, T1 RR showed the best discriminatory capacity and proved to be the only statistically significant parameter in multiple linear regression analysis.

Conclusion

Gd-EOB-DTPA-enhanced MRI as an imaging-based liver function test also correlates with the LiMAx test which in turn reflects cytochrome P450 function. The T1 reduction rate of the liver on Gd-EOB-DTPA-enhanced MRI allows prediction of liver function as determined by the LiMAx test both for 1.5 and 3.0 T.

Quantitative Evaluation of Liver Fibrosis on T1 Relaxometry in Comparison with Fibroscan

Purpose

This study was performed to determine whether the T1 relaxation time of gadoxetic acid-enhanced liver MR imaging is useful for detecting and staging liver fibrosis in patients with chronic liver disease.

Materials and Methods

One hundred and three patients with suspected focal liver lesion underwent MR imaging and Fibroscan. Fibroscan was chosen as the reference standard for classifying liver fibrosis. T1 relaxation times were acquired before (preT1), 20 minutes after (postT1) contrast administration, and reduction rate of T1 relaxation time (rrT1) on transverse 3D VIBE (volumetric interpolated breath-hold examination) sequence using 3T MR imaging. The optimal cut-off values for the fibrosis staging were determined with ROC analysis.

Results

PreT1 and postT1 increased and rrT1 decreased constantly with increasing severity of liver fibrosis according to the METAVIR score (F0–F4). There were statistically significant differences between F2 and F3 in preT1 (F2, 836.0 ± 74.7 ms; F3, 888.6 ± 77.5 ms, p < 0.05) and between F3 and F4 in postT1 (F3, 309.0 ± 80.2 ms; F4, 406.6 ± 147.7 ms, p < 0.05) and rrT1 (F3, 65.4 ± 7.7%; F4, 57.3 ± 11.4%, p < 0.05). ROC analysis revealed that combination test (preT1 + postT1) was the best test for predicting liver fibrosis.

Conclusion

PreT1 and postT1 increased constantly with increasing severity of liver fibrosis. T1 mapping in gadoxetic acid-enhanced liver MR imaging could be a helpful complementary sequence to determine the liver fibrosis stage.

Application Value of Magnetic Resonance Perfusion Imaging in the Early Diagnosis of Rat Hepatic Fibrosis

Objective

To assess the application value of perfusion-weighted imaging (PWI) in early diagnosis, quantitation, and hepatic fibrosis staging by analyzing the related parameters in hepatic fibrosis.

Methods

A total of 60 rats were randomly divided into the hepatic fibrosis and control groups, and carbon tetrachloride (CCL4) was used to establish the liver fibrosis model. All rats underwent PWI examination, and the trend of the time-signal intensity curve (TIC, automatically generated by the software) was observed. Also, the perfusion parameters, maximum signal reduction ratio (SRRmax), time to peak (TTP), and mean transit time (MTT), were analyzed and compared with pathological staging.

Results

The TIC curve was characterized by slow wash-in and wash-out with a low and wide peak. The PWI perfusion parameters were statistically significant in specific groups (P < 0.05): SRRmax values (control group and F3, F4), TTP, and MTT values (control group and F2–F4, F1 and F3, F1 and F4, and F2 and F4 in addition to TTP values for F1 and F2). Pearson's correlation analysis showed a negative correlation of SRRmax with hepatic fibrosis stage (r = −0.439, P < 0.05), while TTP and MTT values were positively correlated with hepatic fibrosis stage (TTP, r = 0.798; MTT, r = 0.647; all P < 0.001).

Conclusions

PWI perfusion parameters reflect the degree of hepatic fibrosis, especially TTP and MTT, and PWI is recommended for the early diagnosis of liver fibrosis for timely intervention and treatment of the disease and delaying its progression.

Clinical and Preclinical Imaging of Hepatosplenic Schistosomiasis

Schistosomiasis, a neglected tropical disease, is a major cause of chronic morbidity and disability, and premature death. The hepatosplenic form of schistosomiasis is characterized by hepatosplenomegaly, liver fibrosis, portal hypertension, and esophageal varices, whose rupture may cause bleeding and death. We review currently available abdominal imaging modalities and describe their basic principles, strengths, weaknesses, and usefulness in the assessment of hepatosplenic schistosomiasis (HSS). Advanced imaging methods are presented that could be of interest for hepatosplenic schistosomiasis evaluation by yielding morphological, functional, and molecular parameters of disease progression. We also provide a comprehensive view of preclinical imaging studies and current research objectives such as parasite visualization in hosts, follow-up of the host's immune response, and development of noninvasive quantitative methods for liver fibrosis assessment.

Gadoxetate-disodium-enhanced magnetic resonance imaging for liver fibrosis staging: a systematic review and meta-analysis

AIM

To identify and evaluate the efficiency of the most commonly used parameters applied to gadoxetate disodium (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) for liver fibrosis (LF) staging.

MATERIALS AND METHODS

Literature searches of PubMed, Web of Science, Embase, and MEDLINE databases from January 2004 to August 2018 were conducted. The applied parameters during imaging were noted and summarised. Studies using the most commonly used parameter were included. Extractive data were combined as pooled weighted mean difference (WMD) to determine the benefits in LF staging. The pooled sensitivity, specificity, and summary receiver operating characteristics (SROC) curve were calculated.

RESULTS

Among 57 relevant studies, the contrast enhancement index (CEI) was a relatively commonly used parameter. It was calculated as SI_post/SI_pre, where SI_post and SI_pre are the liver-to-muscle signal intensity ratios in the hepatocyte phase and pre-enhanced images, respectively. Six studies were included. F0 was regarded as normal liver, F1 as mild LF, F2 as moderate LF, and F3 and F4 as advanced LF. Comparisons of WMD revealed significant differences between F1-2 and F3-4. For stage ≥F1, the pooled sensitivity, specificity, and areas under SROC curve were 0.58, 0.84, and 0.85, respectively; the corresponding values for ≥F2 were 0.57, 0.68, and 0.76, while those for ≥F3 were 0.61, 0.75, and 0.72.

CONCLUSION

The methodology and parameters used for Gd-EOB-DTPA-enhanced MRI for LF staging are diverse, but the CEI was a relatively common parameter. Overall, there is evidence to support use of CEI, but more evidence from larger studies is needed.

Topics on quantitative liver magnetic resonance imaging

Liver magnetic resonance imaging (MRI) is subject to continuous technical innovations through advances in hardware, sequence and novel contrast agent development. In order to utilize the abilities of liver MR to its full extent and perform high-quality efficient exams, it is mandatory to use the best imaging protocol, to minimize artifacts and to select the most adequate type of contrast agent. In this article, we review the routine clinical MR techniques applied currently and some latest developments of liver imaging techniques to help radiologists and technologists to better understand how to choose and optimize liver MRI protocols that can be used in clinical practice. This article covers topics on (I) fat signal suppression; (II) diffusion weighted imaging (DWI) and intravoxel incoherent motion (IVIM) analysis; (III) dynamic contrast-enhanced (DCE) MR imaging; (IV) liver fat quantification; (V) liver iron quantification; and (VI) scan speed acceleration.

Differentiation of hypervascular primary hepatic tumors showing hepatobiliary hypointensity on gadoxetic acid-enhanced magnetic resonance imaging

PURPOSE

To determine the imaging features that help differentiate hypervascular primary hepatic tumors showing hepatobiliary hypointensity on gadoxetic acid MRI.

METHODS

This study comprised 148 patients with pathologically proven hypervascular hepatic tumors who underwent gadoxetic acid MRI. Tumors included 23 atypical focal nodular hyperplasias (FNHs), 11 hepatocellular adenomas (HCAs), 15 neuroendocrine tumors (NETs), 25 intrahepatic cholangiocarcinomas (ICCs), and 74 hepatocellular carcinomas (HCCs). MRIs were analyzed for morphologic features, signal intensity, and enhancement pattern of the tumors to determine the differential features using multivariate logistic regression analysis. We evaluated the diagnostic performance of the MRI features for differentiating the five tumor types upon review by two observers.

RESULTS

Multivariate analysis revealed that reverse target sign on hepatobiliary phase in FNHs (p = 0.009), iso or hyperintensity on ADC map in FNHs and HCAs (p = 0.009, < 0.001, respectively), central hypointensity on arterial phase in NETs (p = 0.001), hepatobiliary target sign in ICCs (p = 0.002), the presence of septum and capsule in HCCs (all p < 0.001) were significant independent features of each tumor group over other tumor groups. Diagnostic accuracy for both observers was 98-98.6% for FNHs, 96.6-98% for HCAs, 97.3-98.6% for NETs, 90.5-94.6% for ICCs, and 85.8-93.2% for HCCs.

CONCLUSIONS

Ancillary MRI features established in our study can be helpful in the differentiation of hypervascular and hepatobiliary hypointense primary hepatic tumors on gadoxetic acid MRI.

Predicting Patients With Insufficient Liver Enhancement in the Hepatobiliary Phase Before the Injection of Gadoxetic Acid: A Practical Approach Using the Bayesian Method

BACKGROUND

Gadoxetic acid-enhanced hepatobiliary phase (HBP) is useful in liver MRI, but sometimes shows insufficient liver enhancement. There is no established method to predict insufficient liver enhancement before the contrast injection.

PURPOSE

To reveal the utility of the Bayesian method for predicting patients with insufficient liver enhancement in the gadoxetic acid-enhanced HBP.

STUDY TYPE

Retrospective.

SUBJECTS

In all, 576 patients with chronic liver disease.

FIELD STRENGTH/SEQUENCE

3T/3D gradient-echo T₁ -weighted imaging and MR elastography (MRE).

ASSESSMENT

The patients were divided into two groups: insufficient and sufficient liver enhancement in HBP according to the liver-to-portal vein signal intensity ratio. Various parameters, including liver function tests and liver stiffness by MRE, were evaluated as predictors of insufficient liver enhancement.

STATISTICAL TESTS

We used Chi-square/Student's t-test/logistic regression analysis to determine independent associates, and Bayes' theorem to estimate the probability of insufficient (or sufficient) liver enhancement. The feasibility of Bayesian prediction of insufficient liver enhancement was tested by leave-one-out cross-validation to calculate sensitivity and specificity for single variables and combinations of some variables in all patients and in a subpopulation showing a confidence level of >80%.

RESULTS

Independent associates of insufficient liver enhancement in HBP included: serum albumin (odds ratio [OR] = 4.82, P < 0.001), total bilirubin (OR = 0.30, P < 0.00), platelet count (OR = 1.54, P < 0.00), and liver stiffness by MRE (OR = 0.59, P < 0.00). The accuracy of Bayesian prediction of insufficient liver enhancement was 80.9% (466/576) for the single parameter of albumin and 79.0% (455/576) for total bilirubin, and was increased to 85.2% (487/576) for a combination of albumin, total bilirubin, and liver stiffness. In patients who showed a confidence level of >80%, the accuracy was 89.0% (439/493) for the above combination.

DATA CONCLUSION

Bayesian prediction was useful to predict patients with insufficient enhancement by combining serum liver function tests and liver stiffness by MRE.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2020;51:62-69.

Noninvasive Assessment of Liver Fibrosis in Patients with Chronic Hepatitis B or C by Contrast-Enhanced Magnetic Resonance Imaging

Background and Aim. To develop a noninvasive magnetic resonance imaging (MRI) method for evaluation of liver fibrosis. We evaluate the utility of hepatocyte-phase Gadoxetate disodium-enhanced magnetic resonance (MR) imaging in staging hepatic fibrosis and compare it with histological analysis as the reference standard (liver biopsy). Methods. Prospective cohort of 78 patients, who received Gadoxetate disodium dynamic contrast-enhanced MRI (DCE-MRI), were divided into three groups. The first group (n=19) was a control group of healthy individuals without liver injury and remaining 59 subjects were chronic hepatitis B and C patients who underwent liver biopsy. These patients were divided into the mild fibrosis F1-F2 (n=32) and advanced fibrosis F3-F4 (n=27) groups. Patients were examined by generated DCE-MRI in 20th minute. Variables such as liver surface changes, homogeneities, and quantitative contrast liver/spleen ratio-Q-LSCR were evaluated and these results were consequently compared between the three groups. Results. Gd-EOB-DTPA contrast-enhanced dynamic liver MRI examination (DCE-MRI) can in the 20th minute differentiate mild stage of liver fibrosis (F1-F2) from severe stage of liver fibrosis (F3-F4) on the basis of liver surface changes, homogeneities, and quantitative contrast liver/spleen ratio-Q-LSCR. Diagnostic MRI criteria were created and named MRI Triple test. This test correctly identified 96% of patients with F3-F4 fibrosis and 91% of patients with the F1-F2 fibrosis in the liver biopsy. This test correctly identified 42,1% of patients in the control group (presumed F0 fibrosis without liver disease). Spearman's rank correlation coefficient (r = 0,86, P < .001) confirmed high agreement of biopsy and MR Triple test. MR Triple test's sensitivity was 96.30% (95%CI 81.03% to 99.91%), specificity 90.62% (95%CI 74.98% to 98.02%), positive predictive value 89.66% (95%CI 74.64% to 96.23%), and negative predictive value 96.67% (95%CI 80.86% to 99.50%) for discrimination between F3-4 and F1-2 fibrosis on liver biopsy. Conclusions. Gd-EOB-DTPA contrast-enhanced MRI liver examination in 20th minute is able to reliably differentiate mild stage of liver fibrosis (F1-F2) from severe stage fibrosis (F3-F4) on the basis of Triple test (liver surface changes, homogeneities, and quantitative contrast liver/spleen ratio-Q-LSCR).

Dynamic Contrast-Enhanced MRI of OATP Dysfunction in Diabetes

Diabetes is associated with hepatic metabolic dysfunction predisposing patients to drug-induced liver injury. Mouse models of type 2 diabetes (T2D) have dramatically reduced expression of organic anion transporting polypeptide (OATP)1A1, a transporter expressed in hepatocytes and in the kidneys. The effects of diabetes on OATP1B2 expression are less studied and less consistent. OATP1A1 and OATP1B2 both transport endogenous substrates such as bile acids and hormone conjugates as well as numerous drugs including gadoxetate disodium (Gd-EOB-DTPA). As master pharmacokinetic regulators, the altered expression of OATPs in diabetes could have a profound and clinically significant influence on drug therapies. Here, we report a method to noninvasively measure OATP activity in T2D mice by quantifying the transport of hepatobiliary-specific gadolinium-based contrast agents (GBCAs) within the liver and kidneys using dynamic contrast-enhanced MRI (DCE-MRI). By comparing GBCA uptake in control and OATP knockout mice, we confirmed liver clearance of the hepatobiliary-specific GBCAs, Gd-EOB-DTPA, and gadobenate dimeglumine, primarily though OATP transporters. Then, we measured a reduction in the hepatic uptake of these hepatobiliary GBCAs in T2D ob/ob mice, which mirrored significant reductions in the mRNA and protein expression of OATP1A1 and OATP1B2. As these GBCAs are U.S. Food and Drug Administration-approved agents and DCE-MRI is a standard clinical protocol, studies to determine OATP1B1/1B3 deficiencies in human individuals with diabetes can be easily envisioned.

Staging of liver fibrosis using Gd-EOB-DTPA and Gd-BOPTA enhanced magnetic resonance imaging

The severity of cirrhosis is closely related to its clinical treatment. Therefore, it is important to stage liver fibrosis accurately. Although liver biopsy can accurately stage the degree of cirrhosis, it has certain limitations in clinical application because of its invasive nature. Magnetic resonance imaging (MRI) has been used in the diagnosis of liver diseases. In recent years, two new contrast agents, gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) and gadobenate dimeglumine (Gd-BOPTA), have been successfully used for noninvasive liver imaging. They can be used for liver fibrosis staging and assessment of liver function. Cirrhotic patients with different liver function levels have a statistical difference in the liver parenchyma enhancement after giving contrast agents. This article briefly summarizes the progress of Gd-EOB-DTPA and Gd-BOPTA enhanced MRI in staging liver fibrosis stage.

Evaluation of hepatic function using dynamic contrast-enhanced magnetic resonance imaging in melanocortin 4 receptor-deficient mice as a model of nonalcoholic steatohepatitis

INTRODUCTION

Melanocortin 4 receptor-deficient (MC4R-KO) mice fed a high-fat diet (HFD) develop liver pathology similar to human nonalcoholic steatohepatitis (NASH). However, although liver histology and blood biochemistry have been reported, hepatic function has not been evaluated. In the present study, we evaluated hepatic function in MC4R-KO mice fed an HFD using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with gadolinium‑ethoxybenzyl‑diethylenetriamine pentaacetic acid (Gd-EOB-DTPA).

MATERIALS AND METHODS

Wild type (WT) mice and MC4R-KO mice were fed a standard diet (SD) or an HFD for 20 weeks. The hepatic signal intensity was obtained from DCE-MRI images, and relative enhancement (RE), the time to maximum RE (T_max), and the half-life of RE elimination (T_1/2) were calculated. Histopathological analysis was then performed.

RESULTS

Histological analysis with nonalcoholic fatty liver disease activity score (NAS) revealed that MC4R-KO mice fed an HFD achieved the NAS of 5. There was moderate fibrosis in MC4R-KO mice fed an HFD. DCE-MRI with Gd-EOB-DTPA showed that T_max and T_1/2 were significantly longer in MC4R-KO mice fed an HFD compared with wild type (WT) mice (T_max, WT, 3.9 ± 0.4 min; MC4R-KO, 7.4 ± 1.5 min; T_1/2, WT, 23.7 ± 1.9 min; MC4R-KO, 62.5 ± 18.5 min). T_max and T_1/2 were significantly correlated with histopathologic score (steatosis vs. Tmax, rho = 0.48, P = 0.04; steatosis vs. T_1/2, rho = 0.50, P = 0.03; inflammation vs. Tmax, rho = 0.55, P = 0.02; inflammation vs. T_1/2, rho = 0.61, P < 0.01; ballooning vs. T_1/2, rho = 0.51, P = 0.03;fibrosis vs T_max, rho = 0.72, P < 0.01; fibrosis vs T_1/2, rho = 0.75, P < 0.01).

CONCLUSIONS

MC4R-KO mice fed an HFD developed obesity and NASH. The liver kinetics of Gd-EOB-DTPA were significantly different in MC4R-KO mice fed an HFD from WT mice, and correlated with the histopathologic score. These results suggest that MC4R-KO mice fed an HFD mimic the hepatic pathology and liver function of human NASH, and therefore might be useful for the study of hepatic dysfunction during the fibrotic stage of NASH.

Non-invasive in vivo Imaging Grading of Liver Fibrosis

Liver fibrosis (LF), a common consequence of chronic liver diseases with various etiologies, is characterized by excessive accumulation of macromolecules, including collagen, glycoproteins and proteoglycans, in the liver. LF can result in hepatic dysfunction, cirrhosis, portal hypertension and, in some cases, hepatocellular carcinoma. As the current gold standard for diagnosing LF, liver biopsy, however, is invasive and prone to sampling errors and procedure-related complications. Therefore, developing noninvasive, precise and reproducible imaging tests for diagnosing and staging LF is of great significance. Conventional ultrasound (US), computed tomography (CT) and magnetic resonance (MR) imaging can depict morphological alterations of advanced LF, but have relatively limited capability characterizing early-stage LF. In order to optimize the diagnostic performances of noninvasive imaging techniques for LF across its entire spectrum of severity, a number of novel methods, including US elastography, CT perfusion imaging and various MR imaging-based techniques, have been established and introduced to clinical practice. In this review, we intended to summarize current noninvasive imaging techniques for LF, with special emphasis on the possible roles, advantages and limitations of the new emerging imaging modalities.

Detection of liver fibrosis using qualitative and quantitative MR elastography compared to liver surface nodularity measurement, gadoxetic acid uptake, and serum markers

BACKGROUND

Multiparametric magnetic resonance imaging (mpMRI) combining different techniques such as MR elastography (MRE) has emerged as a noninvasive approach to diagnose and stage liver fibrosis with high accuracy allowing for anatomical and functional information.

PURPOSE

To assess the diagnostic performance of mpMRI including qualitative and quantitative assessment of MRE, liver surface nodularity (LSN) measurement, hepatic enhancement ratios postgadoxetic acid, and serum markers (APRI, FIB-4) for the detection of liver fibrosis.

STUDY TYPE

IRB-approved retrospective.

SUBJECTS

Eighty-three adult patients.

FIELD STRENGTH/SEQUENCE

1.5T and 3.0T MR systems. MRE and T₁ -weighted postgadoxetic acid sequences.

ASSESSMENT

Two independent observers analyzed qualitative color-coded MRE maps on a scale of 0-3. Regions of interest were drawn to measure liver stiffness on MRE stiffness maps and on pre- and postcontrast T₁ -weighted images to measure hepatic enhancement ratios. Software was used to generate LSN measurements. Histopathology was used as the reference standard for diagnosis of liver fibrosis in all patients.

STATISTICAL TESTS

A multivariable logistic analysis was performed to identify independent predictors of liver fibrosis. Receiver operating characteristic (ROC) analysis evaluated the performance of each imaging technique for detection of fibrosis, in comparison with serum markers.

RESULTS

Liver stiffness measured with MRE provided the strongest correlation with histopathologic fibrosis stage (r = 0.74, P < 0.001), and the highest diagnostic performance for detection of stages F2-F4, F3-F4, and F4 (areas under the curve [AUCs] of 0.87, 0.91, and 0.89, respectively, P < 0.001) compared to other methods. Qualitative assessment of MRE maps showed fair to good accuracy for detection of fibrosis (AUC range 0.76-0.84). Multivariable logistic analysis identified liver stiffness and FIB-4 as independent predictors of fibrosis with AUCs of 0.90 (F2-F4), 0.93 (F3-F4) and 0.92 (F4) when combined.

DATA CONCLUSION

Liver stiffness measured with MRE showed the best performance for detection of liver fibrosis compared to LSN and gadoxetic acid uptake, with slight improvement when combined with FIB-4.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1552-1561.

Quantitative assessment of hepatic fibrosis in chronic hepatitis B and C: T1 mapping on Gd-EOB-DTPA-enhanced liver magnetic resonance imaging

AIM

To assess the accuracy of Look-Locker on gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) for staging liver fibrosis in chronic hepatitis B/C (CHB/C).

METHODS

We prospectively included 109 patients with CHB or CHC who underwent a 3.0-Tesla MRI examination, including T1-weighted and Look-Locker sequences for T1 mapping. Hepatocyte fractions (HeF) and relaxation time reduction rate (RE) were measured for staging liver fibrosis. A receiver operating characteristic analysis using the area under the receiver operating characteristic curve (AUC) was used to compare the diagnostic performance in predicting liver fibrosis between HeF and RE.

RESULTS

A total of 73 patients had both pathological results and MRI information. The number of patients in each fibrosis stage was evaluated semiquantitatively according to the METAVIR scoring system: F0, n = 23 (31.5%); F1, n = 19 (26.0%); F2, n = 13 (17.8%); F3, n = 6 (8.2%), and F4, n = 12 (16.4%). HeF by EOB enhancement imaging was significantly correlated with fibrosis stage (r = -0.808, P < 0.05). AUC values for diagnosis of any (≥ F1), significant (≥ F2) or advanced (≥ F3) fibrosis, and cirrhosis (F4) using HeF were 0.837 (0.733-0.913), 0.890 (0.795-0.951), 0.957 (0.881-0.990), and 0.957 (0.882-0.991), respectively. HeF measurement was more accurate than use of RE in establishing liver fibrosis staging, suggesting that calculation of HeF is a superior noninvasive liver fibrosis staging method.

CONCLUSION

A T1 mapping-based HeF method is an efficient diagnostic tool for the staging of liver fibrosis.

Assessment of Liver Function Using Pharmacokinetic Parameters of Gd-EOB-DTPA: Experimental Study in Rat Hepatectomy Model

Objectives

To determine whether the pharmacokinetic parameters of Gd-EOB-DTPA can identify the difference in liver function in a rat hepatectomy model.

Methods

A total of 56 eight-week-old male Sprague-Dawley rats were divided into the following groups: control group without hepatectomy (n = 16), 70% hepatectomy group (n = 14), and 90% hepatectomy group (n = 26). On postoperative day 2, Gd-EOB-DTPA (0.1 mmol/kg) was injected intravenously and serial blood samples were obtained. Pharmacokinetic analysis was performed using a noncompartmental method. Statistical analysis was performed using one-way analysis of variance and post hoc pairwise group comparisons.

Results

After excluding 6 rats that died unexpectedly, blood samples were obtained from 16, 14, and 20 rats in the control group, 70% hepatectomy group, and 90% hepatectomy group. There was a significant increase in area under the concentration-time curve from time zero to the time of the last measurable concentration between the 70% and 90% hepatectomy group (P < 0.001). The volume of distribution at steady state was significantly decreased between the control and 70% hepatectomy group (P < 0.001). The clearance was significantly different in all pairwise group comparisons (P < 0.001).

Conclusions

The vascular clearance of Gd-EOB-DTPA can identify the difference in liver function in a rat hepatectomy model.

Detecting liver fibrosis with Gd-EOB-DTPA-enhanced MRI: A confirmatory study

Strong correlations between the grade of fibrosis and cirrhosis, classified using the Ishak scoring system, and the uptake characteristics of Gd-EOB-DTPA with the relative enhancement (RE) of the liver parenchyma have been reported. To confirm the results of a retrospective analysis, patients undergoing liver surgery were prospectively examined with Gd-EOB-DTPA-enhanced liver 3 Tesla MRI to determine the degree of liver fibrosis. Correlations between the grade of fibrosis and cirrhosis, classified using the Ishak scoring system, and RE were investigated and compared with those derived from an initial retrospective study. After validating the cut-off values in the retrospective study (Ishak ≥ 1, RE-cut-off 0.90; Ishak ≥ 2, RE-cut-off 0.79; Ishak ≥ 4, RE-cut-off 0.60; and Ishak = 6, RE-cut-off 0.47), we showed that Gd-EOB-DTPA has a high sensitivity (≥86%) and a high positive predictive value (≥86%). These results support the use of Gd-EOB-DTPA-enhanced liver MRI as a non-invasive method for determining the degree of liver fibrosis and cirrhosis.

Quantification of hepatic perfusion and hepatocyte function with dynamic gadoxetic acid-enhanced MRI in patients with chronic liver disease

The purpose of the present study was to develop and perform initial validation of dynamic MRI enhanced with gadoxetic acid as hepatobiliary contrast agent to quantify hepatic perfusion and hepatocyte function in patients with chronic liver disease. Free-breathing, dynamic gadoxetic acid-enhanced MRI was performed at 3.0 T using a 3D time-resolved angiography sequence with stochastic trajectories during 38 min. A dual-input three-compartment model was developed to derive hepatic perfusion and hepatocyte function parameters. Method feasibility was assessed in 23 patients with biopsy-proven chronic liver disease. Parameter analysis could be performed in 21 patients (91%). The hepatocyte function parameters were more discriminant than the perfusion parameters to differentiate between patients with minimal fibrosis (METAVIR F0-F1), intermediate fibrosis (F2-F3) and cirrhosis (F4). The areas under the receiver operating characteristic curves (ROCs) to diagnose significant fibrosis (METAVIR F ≥ 2) were: 0.95 (95% CI: 0.87-1; P<0.001) for biliary efflux, 0.88 (95% CI: 0.73-1; P<0.01) for sinusoidal backflux, 0.81 (95% CI: 0.61-1; P<0.05) for hepatocyte uptake fraction and 0.75 (95% CI: 0.54-1; P<0.05) for hepatic perfusion index (HPI), respectively. These initial results in patients with chronic liver diseases show that simultaneous quantification of hepatic perfusion and hepatocyte function is feasible with free breathing dynamic gadoxetic acid-enhanced MRI. Hepatocyte function parameters may be relevant to assess liver fibrosis severity.

DWI - histology: a possible means of determining degree of liver fibrosis?

Objectives

The aim of this study was to determine the diagnostic value of diffusion-weighted MRI of the liver at 3T to classify liver fibrosis/cirrhosis.

Methods

62 patients who underwent both histopathological examination and diffusion-weighted imaging of the liver via 3T MRI within a period of 3 months were included in the study. The Ishak score (1-6) was used to determine the degree of fibrosis: No liver fibrosis (NLF; Ishak 0, n = 16), mild liver fibrosis (MLF; Ishak 1-2, n = 23), advanced liver fibrosis (ALF; Ishak 3-5, n = 12), and liver cirrhosis (LC; Ishak 6, n = 11).

Results

The corresponding ADC values for the individual patient groups were as follows: NLF: 1123 (SD 95.8); MLF: 1032 (SD 77.6); ALF: 962 (SD 68.8); LC: 1015 (SD 60.2) mm2/s. There is a significant difference between NLF and MLF (p = 0.004) and between MLF and ALF (p = 0.022). A significant difference between patients with ALF and LC (p = 0.117) could not be found.

Conclusion

Liver fibrosis/cirrhosis lowers the ADC values of the liver parenchyma in 3T MRI. However, the degree of fibrosis can only be conditionally determined on the basis of ADC values.

Contrast agents in dynamic contrast-enhanced magnetic resonance imaging

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a noninvasive method to assess angiogenesis, which is widely used in clinical applications including diagnosis, monitoring therapy response and prognosis estimation in cancer patients. Contrast agents play a crucial role in DCE-MRI and should be carefully selected in order to improve accuracy in DCE-MRI examination. Over the past decades, there was much progress in the development of optimal contrast agents in DCE-MRI. In this review, we describe the recent research advances in this field and discuss properties of contrast agents, as well as their advantages and disadvantages. Finally, we discuss the research perspectives for improving this promising imaging method.

Vascular input function correction of inflow enhancement for improved pharmacokinetic modeling of liver DCE-MRI

PURPOSE

To propose a simple method to correct vascular input function (VIF) due to inflow effects and to test whether the proposed method can provide more accurate VIFs for improved pharmacokinetic modeling.

METHODS

A spoiled gradient echo sequence-based inflow quantification and contrast agent concentration correction method was proposed. Simulations were conducted to illustrate improvement in the accuracy of VIF estimation and pharmacokinetic fitting. Animal studies with dynamic contrast-enhanced MR scans were conducted before, 1 week after, and 2 weeks after portal vein embolization (PVE) was performed in the left portal circulation of pigs. The proposed method was applied to correct the VIFs for model fitting. Pharmacokinetic parameters fitted using corrected and uncorrected VIFs were compared between different lobes and visits.

RESULTS

Simulation results demonstrated that the proposed method can improve accuracy of VIF estimation and pharmacokinetic fitting. In animal study results, pharmacokinetic fitting using corrected VIFs demonstrated changes in perfusion consistent with changes expected after PVE, whereas the perfusion estimates derived by uncorrected VIFs showed no significant changes.

CONCLUSION

The proposed correction method improves accuracy of VIFs and therefore provides more precise pharmacokinetic fitting. This method may be promising in improving the reliability of perfusion quantification. Magn Reson Med 79:3093-3102, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Simultaneous acquisition sequence for improved hepatic pharmacokinetics quantification accuracy (SAHA) for dynamic contrast-enhanced MRI of liver

PURPOSE

To propose a simultaneous acquisition sequence for improved hepatic pharmacokinetics quantification accuracy (SAHA) method for liver dynamic contrast-enhanced MRI.

METHODS

The proposed SAHA simultaneously acquired high temporal-resolution 2D images for vascular input function extraction using Cartesian sampling and 3D large-coverage high spatial-resolution liver dynamic contrast-enhanced images using golden angle stack-of-stars acquisition in an interleaved way. Simulations were conducted to investigate the accuracy of SAHA in pharmacokinetic analysis. A healthy volunteer and three patients with cirrhosis or hepatocellular carcinoma were included in the study to investigate the feasibility of SAHA in vivo.

RESULTS

Simulation studies showed that SAHA can provide closer results to the true values and lower root mean square error of estimated pharmacokinetic parameters in all of the tested scenarios. The in vivo scans of subjects provided fair image quality of both 2D images for arterial input function and portal venous input function and 3D whole liver images. The in vivo fitting results showed that the perfusion parameters of healthy liver were significantly different from those of cirrhotic liver and HCC.

CONCLUSIONS

The proposed SAHA can provide improved accuracy in pharmacokinetic modeling and is feasible in human liver dynamic contrast-enhanced MRI, suggesting that SAHA is a potential tool for liver dynamic contrast-enhanced MRI. Magn Reson Med 79:2629-2641, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Evaluation of hepatic fibrosis: a review from the society of abdominal radiology disease focus panel

Hepatic fibrosis is potentially reversible; however early diagnosis is necessary for treatment in order to halt progression to cirrhosis and development of complications including portal hypertension and hepatocellular carcinoma. Morphologic signs of cirrhosis on ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) alone are unreliable and are seen with more advanced disease. Newer imaging techniques to diagnose liver fibrosis are reliable and accurate, and include magnetic resonance elastography and US elastography (one-dimensional transient elastography and point shear wave elastography or acoustic radiation force impulse imaging). Research is ongoing with multiple other techniques for the noninvasive diagnosis of hepatic fibrosis, including MRI with diffusion-weighted imaging, hepatobiliary contrast enhancement, and perfusion; CT using perfusion, fractional extracellular space techniques, and dual-energy, contrast-enhanced US, texture analysis in multiple modalities, quantitative mapping, and direct molecular imaging probes. Efforts to advance the noninvasive imaging assessment of hepatic fibrosis will facilitate earlier diagnosis and improve patient monitoring with the goal of preventing the progression to cirrhosis and its complications.

Diagnostic value of gadobenate dimeglumine-enhanced hepatocyte-phase magnetic resonance imaging in evaluating hepatic fibrosis and hepatitis

AIM

To evaluate the diagnostic value of gadobenate dimeglumine (Gd-BOPTA)-enhanced hepatocyte-phase magnetic resonance imaging (MRI) in evaluating hepatic fibrosis and hepatitis.

METHODS

Hepatocyte-phase images of Gd-BOPTA-enhanced MRI were retrospectively evaluated in 76 patients with chronic liver disease. These patients were classified into five groups according to either the histopathological fibrosis stage (S0-S4) or the histopathological hepatitis grade (G0-G4). The relative enhancement ratio (RE) of the liver parenchyma in the T1-vibe sequence was calculated by measuring the signal intensity before (SI pre) and 90 min after (SI post) intravenous injection of Gd-BOPTA using the following formula: RE = (SI post - SI pre)/SI pre. One-way analysis of variance was used to compare the difference between the relative RE in the hepatocyte phase (REh) and the stage of hepatic fibrosis and the grade of hepatitis. Pearson’s product-moment correlation analysis was used to evaluate the relationship between the REh and the levels of serologic liver functional parameters.

RESULTS

According to histopathological hepatic fibrosis stage, the 76 patients were classified into five groups: 16 in S0, 15 in S1, 21 in S2, 9 in S3, and 15 in S4 group. According to histopathological hepatitis grade, the 76 patients were also classified into five groups: 0 in G0, 44 in G1, 22 in G2, 8 in G3, and 2 in G3 group. With regard to the stage of hepatic fibrosis, REh showed significant differences between the S2 and S3 groups and between the S2 and S4 groups (P < 0.05), but no significant difference was observed between the other groups. With regard to the grade of hepatitis, REh showed significant differences between the G1 and G2 groups and between the G1 and G4 groups (P < 0.05), but no significant difference was observed between the other groups. Increased REh showed correlations with decreased serum levels of TB, ALT and AST (P < 0.05).

CONCLUSION

To some extent, measuring the REh using Gd-BOPTA-enhanced MRI might be a noninvasive technique for assessing the stage of hepatic fibrosis. This method is able to differentiate no/mild hepatitis from advanced hepatitis. TB, ALT and AST levels can predict the degree of liver enhancement in the hepatocyte phase of Gd-BOPTA-enhanced MRI.

Quantitative Measurement of Hepatic Fibrosis with Gadoxetic Acid-Enhanced Magnetic Resonance Imaging in Patients with Chronic Hepatitis B Infection: A Comparative Study on Aspartate Aminotransferase to Platelet Ratio Index and Fibrosis-4 Index

Objective

To quantitatively measure hepatic fibrosis on gadoxetic acid-enhanced magnetic resonance (MR) in chronic hepatitis B (CHB) patients and identify the correlations with aspartate aminotransferase-to-platelet ratio index (APRI) and fibrosis-4 index (FIB-4) values.

Materials and Methods

This study on gadoxetic acid-enhanced 3T MR imaging included 81 patients with CHB infection. To quantitatively measure hepatic fibrosis, MR images were analyzed with an aim to identify inhomogeneous signal intensities calculated from a coefficient of variation (CV) map in the liver parenchyma. We also carried out a comparative analysis between APRI and FIB-4 based on metaregression results. The diagnostic performance of the CV map was evaluated using a receiver-operating characteristic (ROC) curve.

Results

In the MR images, the mean CV values in control, groups I, II, and III based on APRI were 4.08 ± 0.92, 4.24 ± 0.80, 5.64 ± 1.11, and 5.73 ± 1.28, respectively (p < 0.001). In CHB patients grouped by FIB-4, the mean CV values of groups A, B, and C were 4.22 ± 0.95, 5.40 ± 1.19, and 5.71 ± 1.17, respectively (p < 0.001). The mean CV values correlated well with APRI (r = 0.392, p < 0.001) and FIB-4 (r = 0.294, p < 0.001). In significant fibrosis group, ROC curve analysis yielded an area under the curve of 0.875 using APRI and 0.831 using FIB-4 in HB, respectively.

Conclusion

Gadoxetic acid-enhanced MR imaging for calculating a CV map showed moderate correlation with APRI and FIB-4 values and could be employed to quantitatively measure hepatic fibrosis in patients with CHB.

Gd-EOB-DTPA-enhanced MR relaxometry for the detection and staging of liver fibrosis

Gd-EOB-DTPA, a liver-specific contrast agent with T1-shortening effects, is routinely used in clinical routine for detection and characterization of focal liver lesions and has recently received increasing attention as a tool for the quantitative analyses of liver function. We report the relationship between the extent of Gd-EOB-DTPA- induced T1 relaxation and the degree of liver fibrosis, which was assessed according to the METAVIR score. For the T1 relaxometry, a transverse 3D VIBE sequence with inline T1 calculation was acquired prior to and 20 minutes after Gd-EOB-DTPA administration. The reduction rates of the T1 relaxation time (rrT1) between the pre- and postcontrast images were calculated, and the optimal cutoff values for the fibrosis stages were determined with receiver operating characteristic (ROC) curve analyses. The rrT1 decreased with the severity of liver fibrosis and regression analysis revealed a significant correlation of the rrT1 with the stage of liver fibrosis (r = -0.906, p < 0.001). ROC analysis revealed sensitivities ≥78% and specificities ≥94% for the differentiation of different fibrosis stages. Gd-EOB-DTPA-enhanced T1 relaxometry is a reliable tool for both the detection of initial hepatic fibrosis and the staging of hepatic fibrosis.

Hepatic gadoxetic acid uptake as a measure of diffuse liver disease: Where are we?

MRI has emerged as the most comprehensive noninvasive diagnostic tool for focal liver lesions and diffuse hepatobiliary disorders. The introduction of hepatobiliary contrast agents, most notably gadoxetic acid (GA), has expanded the role of MRI, particularly in the functional imaging of chronic liver diseases, such as nonalcoholic fatty liver disease (NAFLD). GA-enhanced MRI (GA-MRI) may help to distinguish between the two subgroups of NAFLD, simple steatosis and nonalcoholic steatohepatitis. Furthermore, GA-MRI can be used to stage fibrosis and cirrhosis, predict liver transplant graft survival, and preoperatively estimate the risk of liver failure should major resection be undertaken. The amount of GA uptake can be estimated, using static images, by the relative liver enhancement, hepatic uptake index, and relaxometry of T1-mapping during the hepatobiliary phase. On the contrary, the hepatic extraction fraction and liver perfusion can be measured on dynamic imaging. Importantly, there is currently no clear consensus as to which of these MR-derived parameters is the most suitable for assessing liver dysfunction. This review article aims to describe the current role of GA-enhanced MRI in quantifying liver function, primarily in diffuse hepatobiliary disorders.

LEVEL OF EVIDENCE

3 J. Magn. Reson. Imaging 2017;45:646-659.

Hepatic function imaging using dynamic Gd-EOB-DTPA enhanced MRI and pharmacokinetic modeling

PURPOSE

To determine whether pharmacokinetic modeling parameters with different output assumptions of dynamic contrast-enhanced MRI (DCE-MRI) using Gd-EOB-DTPA correlate with serum-based liver function tests, and compare the goodness of fit of the different output assumptions.

METHODS

A 6-min DCE-MRI protocol was performed in 38 patients. Four dual-input two-compartment models with different output assumptions and a published one-compartment model were used to calculate hepatic function parameters. The Akaike information criterion fitting error was used to evaluate the goodness of fit. Imaging-based hepatic function parameters were compared with blood chemistry using correlation with multiple comparison correction.

RESULTS

The dual-input two-compartment model assuming venous flow equals arterial flow plus portal venous flow and no bile duct output better described the liver tissue enhancement with low fitting error and high correlation with blood chemistry. The relative uptake rate Kir derived from this model was found to be significantly correlated with direct bilirubin (r = -0.52, P = 0.015), prealbumin concentration (r = 0.58, P = 0.015), and prothrombin time (r = -0.51, P = 0.026).

CONCLUSION

It is feasible to evaluate hepatic function by proper output assumptions. The relative uptake rate has the potential to serve as a biomarker of function. Magn Reson Med 78:1488-1495, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Assessment of liver function by Gd-EOB-DTPA enhanced magnetic resonance imaging

Gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA), a liver-specific magnetic resonance imaging (MRI) contrast agent, is increasingly used for imaging-based liver function tests. Like indocyanine green and mebrofenin, Gd-EOB-DTPA is taken up by hepatocytes through organic anion-transporting polypeptides 1 (OATP₁) B₁ and B₃ and is then excreted into the bile by multi-drug resistance protein (MRP₂). The advantages of Gd-EOB-DTPA-based liver function tests include function measurement integrated in an existing MRI protocol, ability of evaluating segmental liver function, and no ionizing radiation. The approaches based on Gd-EOB-DTPA for function measurement are as follows: measurement of biliary elimination, hepatic parenchymal enhancement, MR relaxometry, and MR perfusion. These approaches have potential value for assessing liver reserve, hepatic fibrosis, non-alcoholic fatty liver disease and so on.

[Functional MR imaging of the liver]

The diagnostics of diffuse liver disease traditionally rely on liver biopsies and histopathological analysis of tissue specimens. However, a liver biopsy is invasive and carries some non-negligible risks, especially for patients with decreased liver function and those requiring repeated follow-up examinations. Over the last decades, magnetic resonance imaging (MRI) has developed into a valuable tool for the non-invasive characterization of focal liver lesions and diseases of the bile ducts. Recently, several MRI methods have been developed and clinically evaluated that also allow the diagnostics and staging of diffuse liver diseases, e.g. non-alcoholic fatty liver disease, hepatitis, hepatic fibrosis, liver cirrhosis, hemochromatosis and hemosiderosis. The sequelae of diffuse liver diseases, such as a decreased liver functional reserve or portal hypertension, can also be detected and quantified by modern MRI methods. This article provides the reader with the basic principles of functional MRI of the liver and discusses the importance in a clinical context.

Semi-quantitative assessment of the presence and Child-Pugh class of hepatitis B related cirrhosis by using liver lobe-based dynamic contrast-enhanced MRI

AIM

To determine whether liver lobe-based DCE-MRI can be used to detect the presence and Child-Pugh class of hepatitis B-related cirrhosis.

MATERIALS AND METHODS

Fifty-six cirrhotic patients with hepatitis B and 20 healthy participants underwent liver DCE-MRI, and the positive enhancement integral (PEI), time to peak (TTP), maximum slope of increase (MSI) and maximum slope of decrease (MSD) of the left lateral liver lobe (LLL), left medial liver lobe (LML), right liver lobe (RL), and caudate lobe (CL) were measured and analysed statistically to evaluate cirrhosis.

RESULTS

TTP values of the LLL, LML, RL and CL were positively correlated with the Child-Pugh class of cirrhosis (r=0.452 to 0.55, all p<0.05). PEI values of the LLL, LML, RL and CL, as well as the MSI of the CL and the MSD of the RL, were inversely correlated with the Child-Pugh class (r=-0.349 to -0.72, all p<0.05). PEI values of the LLL and CL, or TTP values of the RL had the most area under receiver operating characteristic curve (AUC) of 0.99 for identifying the presence of liver cirrhosis. The PEI of the RL had the largest AUC of 0.975 and 0.78 for distinguishing the Child-Pugh class A of cirrhosis from class B-C and class A-B of cirrhosis from class C, respectively.

CONCLUSION

Liver lobe-based DCE-MRI parameters are associated with the presence and Child-Pugh class of hepatitis B-related cirrhosis.

Staging liver fibrosis in chronic hepatitis B with T1 relaxation time index on gadoxetic acid-enhanced MRI: Comparison with aspartate aminotransferase-to-platelet ratio index and FIB-4

PURPOSE

To assess the accuracy of the T₁ relaxation time index on gadoxetic acid-enhanced magnetic resonance imaging (MRI) for staging liver fibrosis in chronic hepatitis B (CHB), in comparison and combination with the aspartate aminotransferase-to-platelet ratio index (APRI) and fibrosis-4 (FIB-4).

MATERIALS AND METHODS

A retrospective study of gadoxetic acid-enhanced T₁ mapping and serum biochemical tests was performed on 126 CHB patients who underwent gadoxetic acid-enhanced 1.5T MRI, and the histological score used as the gold standard. The reduction rate of T₁ relaxation time before and 20 minutes after gadoxetic acid injection (ΔT₁ , ΔR1%), the contrast uptake rate (K_Hep ), APRI, and FIB-4 were calculated. The diagnostic efficacy of ΔT₁ , ΔR1%, K_Hep , APRI, and FIB-4 for predicting stage 2 or greater (≥S2), stage 3 or greater (≥S3), and stage 4 (S4) was compared.

RESULTS

ΔT₁ (r = -0.513, P < 0.001), ΔR1% (r = -0.626, P < 0.001), K_Hep (r = -0.527, P < 0.001), APRI (r = 0.519, P < 0.001), and FIB-4 (r = 0.476, P < 0.001) correlated significantly with fibrosis stages. Areas under the curves (AUCs) of ΔR1% for detecting ≥S2, ≥S3, and S4 were 0.849, 0.827, and 0.809, which were greater than that of APRI (0.763, 0.745, 0.787) and FIB-4 (0.727, 0.738, 0.772), but significant difference was found only in discriminating ≥S2 between ΔR1% and FIB-4 (P = 0.027). The combination of all five indices performed best, with AUC, sensitivity, and specificity of 0.860, 87.21%, and 72.50% for diagnosing ≥S2, 0.878, 82.81%, and 85.48% for ≥S3, and 0.867, 80.00%, and 83.95% for S4.

CONCLUSION

The gadoxetic acid-enhanced T₁ relaxation time index appears to be superior to APRI and FIB-4 for predicting hepatic fibrosis. The combined use of gadoxetic acid-enhanced T₁ mapping, APRI, and FIB-4 may be more reliable for staging liver fibrosis in CHB.

LEVEL OF EVIDENCE

4 J. Magn. Reson. Imaging 2017;45:1186-1194.