MR prediction of liver fibrosis using a liver-specific contrast agent: Superparamagnetic iron oxide versus Gd-EOB-DTPA

Comparison between CT volumetry, technetium99m galactosyl-serum-albumin scintigraphy, and gadoxetic-acid-enhanced MRI to estimate the liver fibrosis stage in preoperative patients

OBJECTIVES

To compare the efficacy of computed tomography volumetry (CTV), technetium99m galactosyl-serum-albumin (99mTc-GSA) scintigraphy, and gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic-acid-enhanced MRI (EOB-MRI) in estimating the liver fibrosis (LF) stage in patients undergoing liver resection.

METHODS

This retrospective study included 91 consecutive patients who had undergone preoperative dynamic CT and 99mTc-GSA scintigraphy. EOB-MRI was performed in 76 patients. CTV was used to measure the total liver volume (TLV), spleen volume (SV), normalised to the body surface area (BSA), and liver-to-spleen volume ratio (TLV/SV). 99mTc-GSA scintigraphy provided LHL15, HH15, and GSA indices. The liver-to-spleen ratio (LSR) was calculated in the hepatobiliary phase of EOB-MRI. Hyaluronic acid and type 4 collagen levels were measured in 65 patients. Logistic regression and receiver operating characteristic (ROC) analyses were performed to identify useful parameters for estimating the LF stage and laboratory data.

RESULTS

According to the multivariable logistic regression analysis, SV/BSA (odds ratio [OR], 1.01; 95% confidence interval [CI], 1.003-1.02; p = 0.011), LSR (OR, 0.06; 95%CI, 0.004-0.70; p = 0.026), and hyaluronic acid (OR, 1.01; 95%CI, 1.001-1.02; p = 0.024) were independent variables for severe LF (F3-4). Combined SV/BSA, LSR, and hyaluronic acid correctly estimated severe LF, with an AUC of 0.91, which was significantly larger than the AUCs of the GSA index (AUC = 0.84), SV/BSA (AUC = 0.83), or LSR (AUC = 0.75) alone.

CONCLUSIONS

Combined CTV, EOB-MRI, and hyaluronic acid analyses improved the estimation accuracy of severe LF compared to CTV, EOB-MRI, or 99mTc-GSA scintigraphy individually.

CLINICAL RELEVANCE STATEMENT

The combined analysis of spleen volume on CT volumetry, liver-to-spleen ratio on gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic-acid-enhanced MRI, and hyaluronic acid can identify severe liver fibrosis associated with a high risk of liver failure after hepatectomy and recurrence in patients with hepatocellular carcinoma.

KEY POINTS

• Spleen volume of CT volumetry normalised to the body surface area, liver-to-spleen ratio of EOB-MRI, and hyaluronic acid were independent variables for liver fibrosis. • CT volumetry and EOB-MRI enable the detection of severe liver fibrosis, which may correlate with post-hepatectomy liver failure and complications. • Combined CT volumetry, gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic-acid-enhanced MRI (EOB-MRI), and hyaluronic acid analyses improved the estimation of severe liver fibrosis compared to technetium99m galactosyl-serum-albumin scintigraphy.

Magnetic Resonance Imaging for Monitoring of Hepatic Disease Induced by Ebola Virus: a Nonhuman Primate Proof-of-Concept Study

Severe liver impairment is a well-known hallmark of Ebola virus disease (EVD). However, the role of hepatic involvement in EVD progression is understudied. Medical imaging in established animal models of EVD (e.g., nonhuman primates [NHPs]) can be a strong complement to traditional assays to better investigate this pathophysiological process in vivo and noninvasively. In this proof-of-concept study, we used longitudinal multiparametric magnetic resonance imaging (MRI) to characterize liver morphology and function in nine rhesus monkeys after exposure to Ebola virus (EBOV). Starting 5 days postexposure, MRI assessments of liver appearance, morphology, and size were consistently compatible with the presence of hepatic edema, inflammation, and congestion, leading to significant hepatomegaly at necropsy. MRI performed after injection of a hepatobiliary contrast agent demonstrated decreased liver signal on the day of euthanasia, suggesting progressive hepatocellular dysfunction and hepatic secretory impairment associated with EBOV infection. Importantly, MRI-assessed deterioration of biliary function was acute and progressed faster than changes in serum bilirubin concentrations. These findings suggest that longitudinal quantitative in vivo imaging may be a useful addition to standard biological assays to gain additional knowledge about organ pathophysiology in animal models of EVD. IMPORTANCE Severe liver impairment is a well-known hallmark of Ebola virus disease (EVD), but the contribution of hepatic pathophysiology to EVD progression is not fully understood. Noninvasive medical imaging of liver structure and function in well-established animal models of disease may shed light on this important aspect of EVD. In this proof-of-concept study, we used longitudinal magnetic resonance imaging (MRI) to characterize liver abnormalities and dysfunction in rhesus monkeys exposed to Ebola virus. The results indicate that in vivo MRI may be used as a noninvasive readout of organ pathophysiology in EVD and may be used in future animal studies to further characterize organ-specific damage of this condition, in addition to standard biological assays.

Application of A U-Net for Map-like Segmentation and Classification of Discontinuous Fibrosis Distribution in Gd-EOB-DTPA-Enhanced Liver MRI

Highlights

Abstract

We aimed to evaluate whether U-shaped convolutional neuronal networks can be used to segment liver parenchyma and indicate the degree of liver fibrosis/cirrhosis at the voxel level using contrast-enhanced magnetic resonance imaging. This retrospective study included 112 examinations with histologically determined liver fibrosis/cirrhosis grade (Ishak score) as the ground truth. The T1-weighted volume-interpolated breath-hold examination sequences of native, arterial, late arterial, portal venous, and hepatobiliary phases were semi-automatically segmented and co-registered. The segmentations were assigned the corresponding Ishak score. In a nested cross-validation procedure, five models of a convolutional neural network with U-Net architecture (nnU-Net) were trained, with the dataset being divided into stratified training/validation (n = 89/90) and holdout test datasets (n = 23/22). The trained models precisely segmented the test data (mean dice similarity coefficient = 0.938) and assigned separate fibrosis scores to each voxel, allowing localization-dependent determination of the degree of fibrosis. The per voxel results were evaluated by the histologically determined fibrosis score. The micro-average area under the receiver operating characteristic curve of this seven-class classification problem (Ishak score 0 to 6) was 0.752 for the test data. The top-three-accuracy-score was 0.750. We conclude that determining fibrosis grade or cirrhosis based on multiphase Gd-EOB-DTPA-enhanced liver MRI seems feasible using a 2D U-Net. Prospective studies with localized biopsies are needed to evaluate the reliability of this model in a clinical setting.

T1 reduction rate with Gd-EOB-DTPA determines liver function on both 1.5 T and 3 T MRI

Magnetic resonance T1 mapping before and after Gd-EOB-DTPA administration allows quantification of the T1 reduction rate as a non-invasive surrogate marker of liver function. A major limitation of T1 relaxation time measurement is its dependency on MRI field strengths. Since T1 reduction rate is calculated as the relative shortening of T1 relaxation time before and after contrast administration, we hypothesized that the T1 reduction rate is comparable between 1.5 and 3 T. We thus compared liver T1 relaxation times between 1.5 and 3 T in a total of 243 consecutive patients (124, 1.5 T and 119, 3 T) between 09/2018 and 07/2019. T1 reduction rates were compared between patients with no cirrhosis and patients with cirrhosis Child-Pugh A-C. There was no significant difference of T1 reduction rate between 1.5 and 3 T in any patient group (p-value 0.126-0.861). On both 1.5 T and 3 T, T1 reduction rate allowed to differentiate between patients with no cirrhosis and patients with liver cirrhosis Child A-C (p < 0.001). T1 reduction rate showed a good performance to predict liver cirrhosis Child A (AUC = 0.83, p < 0.001), Child B (AUC = 0.83, p < 0.001) and Child C (AUC = 0.92, p < 0.001). In conclusion, T1 reduction rate allows to determine liver function on Gd-EOB-DTPA MRI with comparable values on 1.5 T and 3 T.

Diagnostic potential of T1ρ and T2 relaxations in assessing the severity of liver fibrosis and necro-inflammation

PURPOSE

To investigate the utility of T1ρ and T2 relaxations for assessing the severity of liver fibrosis (F stage) and necro-inflammation (A stage) in patients with chronic liver disease (CLD).

MATERIALS AND METHODS

We calculated T1ρ and T2 relaxations of the liver parenchyma in 82 patients who underwent liver surgery. F and A stages of enrolled patients were assessed by referring to surgically resected specimens. The relationships between T1ρ or T2 relaxation and F or A stage were assessed using one-way analysis of variance followed by Tukey's multiple comparison test, Spearman's rank correlation test and a receiver operating characteristic analysis.

RESULTS

The T1ρ and T2 values of the liver parenchyma were significantly increased as the F and A stages progressed. The T1ρ and T2 values showed significant differences between F0 and F4, between F1 and F4, and between F2 and F4. In addition, T1ρ values showed a significant difference between F0 and F3 as well. The highest diagnostic ability for fibrosis was obtained when differentiating ≥F3 from ≤F2 using T1ρ: the sensitivity was 82.8%, the specificity 79.2% and the area under the curve (AUC) 0.87. The sensitivity and AUC of T1ρ relaxation (46.9% and 0.67) were significantly higher than those of T2 relaxation (29.7% and 0.60) for differentiating ≥A1 from A0.

CONCLUSION

T1ρ and T2 relaxations have potential as a biochemical marker for assessing the severity of liver fibrosis and necro-inflammation. T1ρ relaxation may be slightly superior to T2 relaxation in terms of diagnostic ability for liver fibrosis and necro-inflammation.

Therapeutic and diagnostic targeting of fibrosis in metabolic, proliferative and viral disorders

Fibrosis is a common denominator in many pathologies and crucially affects disease progression, drug delivery efficiency and therapy outcome. We here summarize therapeutic and diagnostic strategies for fibrosis targeting in atherosclerosis and cardiac disease, cancer, diabetes, liver diseases and viral infections. We address various anti-fibrotic targets, ranging from cells and genes to metabolites and proteins, primarily focusing on fibrosis-promoting features that are conserved among the different diseases. We discuss how anti-fibrotic therapies have progressed over the years, and how nanomedicine formulations can potentiate anti-fibrotic treatment efficacy. From a diagnostic point of view, we discuss how medical imaging can be employed to facilitate the diagnosis, staging and treatment monitoring of fibrotic disorders. Altogether, this comprehensive overview serves as a basis for developing individualized and improved treatment strategies for patients suffering from fibrosis-associated pathologies.

Liver Fibrosis Staging with Gadolinium Ethoxybenzyl Diethylenetriamine Penta-Acetic Acid-enhanced: A Systematic Review and Meta-analysis

OBJECTIVE

While liver biopsy is the golden standard for liver-fibrosis diagnosis, it is also invasive and has many limitations. Non-invasive techniques such as Magnetic Resonance Imaging (MRI) need to be further developed for liver fibrosis staging. This study aimed to evaluate the diagnostic accuracy of Gadolinium Ethoxybenzyl Diethylenetriamine Penta-acetic Acid (Gd-EOBDTPA)- enhanced MRI for liver fibrosis through systematic review and meta-analysis.

METHODS

This study comprehensively searched relevant article in PubMed, Embase, and the Cochrane Library published from 2004 to 2018 to find studies analyzing the diagnostic accuracy of Gd-EOB-DTPA-enhanced MRI for liver fibrosis. Two reviewers independently screened the retrieved articles, extracted the required data from the included studies, and evaluated the methodological quality of the studies. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and Summary Receiver Operating Characteristics (SROC) curve were assessed.

RESULTS

This study finally included 16 studies (n = 1,599) and selected a random-effects model based on the results of the I² statistic to combine them. The areas under the SROC curve for the detection of F1 or greater, F2 or greater, F3 or greater, or F4 liver fibrosis were 0.8669, 0.8399, 0.8481, and 0.8858, respectively.

CONCLUSION

Gd-EOB-DTPA-enhanced MRI showed a good diagnostic performance for staging liver fibrosis, especially for F4 liver fibrosis.

Patterns of enhancement in the hepatobiliary phase of gadoxetic acid-enhanced MRI

A variety of patterns of enhancement of liver lesions and liver parenchyma is observed in the hepatobiliary phase (HBP) of gadoxetic acid-enhanced MRI. It is becoming increasingly apparent that many lesions may exhibit HBP enhancement. Much of the literature regarding the role of gadoxetic acid-enhanced MRI in characterising liver lesions is dichotomous, focusing on whether lesions are enhancing or non-enhancing in the HBP, rather than examining the patterns of enhancement. We provide a pattern-based description of HBP enhancement of liver parenchyma and of liver lesions. The role of OATP1B3 transporters, hepatocyte function and lesion composition in influencing patterns of HBP hyperintensity are discussed.

Efficiency of regional functional liver volume assessment using Gd-EOB-DTPA-enhanced magnetic resonance imaging for hepatocellular carcinoma with portal vein tumor thrombus

PURPOSE

We investigated whether functional future remnant liver volume (fFRLV), assessed using gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (EOB-MRI), could evaluate regional liver function in hepatocellular carcinoma (HCC) patients with portal vein tumor thrombus (PVTT) and help establish the indication for hepatectomy.

METHODS

The subjects of this study were 12 patients with PVTT [PVTT(+) group] and 58 patients without PVTT [PVTT(-) group], from among 191 patients who underwent hepatectomy of more than one segment for HCC. We calculated the liver-to-muscle ratio (LMR) in the remnant liver, using EOB-MRI and fFRLV. Preoperative factors and surgical outcome were compared between the groups. The LMR of the area occluded by PVTT was compared with that of the non-occluded area.

RESULTS

The indocyanine green retention rate at 15 min (ICG-R15) and liver fibrosis indices were increased in the PVTT(+) group, but the surgical outcomes of patients in this group were acceptable, with no liver failure, no mortality, and no differences from those in the PVTT(-) group. The fFRLV in the PVTT(+) group was not significantly different from that in the PVTT(-) group (p = 0.663). The LMR was significantly lower in the occluded area than in the non-occluded area (p = 0.004), indicating decreased liver function.

CONCLUSION

Assessing fFRLV using EOB-MRI could be useful for evaluating regional liver function and establishing operative indications for HCC with PVTT.

Increased and More Heterogeneous Gadoxetic Acid Uptake of the Liver Parenchyma after Hepatitis C Virus Eradication by Direct Antiviral Agent

We evaluated the changes of gadoxetic acid uptake of the liver parenchyma after hepatitis C virus (HCV) eradication by direct-antiviral agent (DAA) therapy. The increase rate of the liver-to-muscle signal intensity ratio, the skewness and the kurtosis were calculated in the hepatobiliary phase. After sustained virological response, gadoxetic acid uptake of the liver parenchyma increased, but became heterogeneous. Our study proved that HCV eradication by DAA therapy could significantly affect gadoxetic acid uptake.

Functional remnant liver volumetry using Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) predicts post-hepatectomy liver failure in resection of more than one segment

BACKGROUND

Gd-EOB-DTPA-enhanced magnetic resonance imaging (EOB-MRI) can be used for evaluating liver functional reserve. We assessed whether functional remnant liver volumetry (FRLV) using EOB-MRI predicted post-hepatectomy liver failure (PHLF) in resection of more than one segment.

METHODS

We retrospectively analyzed 155 cases of hepatectomy of more than one segment. For assessment of FRLV, signal intensity (SI) of remnant liver was measured in T1-weighted images. Functional remnant liver score was derived by division of SI of liver by SI of muscle (or spleen), resulting in liver-to-muscle ratio (LMR) and liver-to-spleen ratio (LSR). FRLV were calculated by multiplying LMR (or LSR) and remnant liver volume. We investigated preoperative factors predicting PHLF (≥grade B) in study cohort (all cases except for portal vein embolization [PVE], n = 129) and validation cohort (PVE cases, n = 26).

RESULTS

In study cohort, PHLF occurred in 5 patients (3.9%). In multivariate analysis, FRLV (LMR) was the most reliable predictor of PHLF (P = 0.013). The cutoff value of FRLV (LMR) predicting PHLF was 615 mL/m² (AUC: 0.939). In validation cohort (n = 26), the cutoff value of FRLV (LMR) indicated reliable results, sensitivity (100%), specificity (77.3%), and accuracy (80.8%).

CONCLUSIONS

FRLV using LMR could precisely predict PHLF of more than one segment, and was useful even in patients who underwent PVE.

GAN and dual-input two-compartment model-based training of a neural network for robust quantification of contrast uptake rate in gadoxetic acid-enhanced MRI

PURPOSE

Gadoxetic acid uptake rate (k₁ ) obtained from dynamic, contrast-enhanced (DCE) magnetic resonance imaging (MRI) is a promising measure of regional liver function. Clinical exams are typically poorly temporally characterized, as seen in a low temporal resolution (LTR) compared to high temporal resolution (HTR) experimental acquisitions. Meanwhile, clinical demands incentivize shortening these exams. This study develops a neural network-based approach to quantitation of k₁ , for increased robustness over current models such as the linearized single-input, two-compartment (LSITC) model.

METHODS

Thirty Liver HTR DCE MRI exams were acquired in 22 patients with at least 16 min of postcontrast data sampled at least every 13 s. A simple neural network (NN) with four hidden layers was trained on voxel-wise LTR data to predict k₁ . Low temporal resolution data were created by subsampling HTR data to contain six time points, replicating the characteristics of clinical LTR data. Both the total length and the placement of points in the training data were varied considerably to encourage robustness to variation. A generative adversarial network (GAN) was used to generate arterial and portal venous inputs for use in data augmentation based on the dual-input, two-compartment, pharmacokinetic model of gadoxetic acid in the liver. The performance of the NN was compared to direct application of LSITC on both LTR and HTR data. The error was assessed when subsampling lengths from 16 to 4 min, enabling assessment of robustness to acquisition length.

RESULTS

For acquisition lengths of 16 min NRMSE (Normalized Root-Mean-Squared Error) in k₁ was 0.60, 1.77, and 1.21, for LSITC applied to HTR data, LSITC applied to LTR data, and GAN-augmented NN applied to LTR data, respectively. As the acquisition length was shortened, errors greatly increased for LSITC approaches by several folds. For acquisitions shorter than 12 min the GAN-augmented NN approach outperformed the LSITC approach to a statistically significant extent, even with HTR data.

CONCLUSIONS

The study indicates that data length is significant for LSITC analysis as applied to DCE data for standard temporal sampling, and that machine learning methods, such as the implemented NN, have potential for much greater resilience to shortened acquisition time than directly fitting to the LSITC model.

Systematic review: The diagnostic efficacy of gadoxetic acid-enhanced MRI for liver fibrosis staging

PURPOSE

To evaluate the diagnostic efficacy of gadoxetic acid-enhanced MRI for the staging of liver fibrosis by meta-analysis.

METHODS

PubMed/Medline, EMBASE, the Web of Science, and the Cochrane Library were searched. Studies were included according to their eligibility and the exclusion criteria. The Quality Assessment of Diagnostic Accuracy Studies 2 tool was used to assess the methodologic quality. The bivariate random-effects model was used to obtain the pooled summary estimates, heterogeneity, and the area under summary receiver operating characteristic curves (AUROC). Meta-regression was performed to discover the source of heterogeneity and compare certain some subsets for their capacity to stage hepatic fibrosis by AUROC comparison.

RESULTS

A total of 20 original articles (1936 patients) were included. Most studies had a low risk of bias and minimal concerns regarding applicability. The summary AUROC values of gadoxetic acid-enhanced MRI in staging the liver fibrosis ≥ F1, ≥ F2, ≥ F3, and F4 subsets were 0.92, 0.87, 0.89, and 0.91, respectively. Studies with populations equal to or more than 100 had a significantly higher sensitivity (84 %) and specificity (91 %) than those with populations less than 100 (70 % and 77 %, respectively, P < 0.01). Studies of a prospective design exhibited a significantly higher sensitivity (94 %) and specificity (94 %) than those of a retrospective design (75 % and 84 %, respectively, P < 0.01).

CONCLUSIONS

Our meta-analysis shows the high diagnostic efficacy of gadoxetic acid-enhanced MRI in the staging of liver fibrosis. A prospective study with more than one hundred patients showed higher diagnostic efficacy.

Assessment of liver fibrosis with gadoxetic acid-enhanced MRI: comparisons with transient elastography, ElastPQ, and serologic fibrosis markers

OBJECTIVES

To compare the diagnostic performance of gadoxetic acid-enhanced magnetic resonance imaging (MRI), ultrasonography (US)-based elastography, and serologic fibrosis markers in assessing the stage of liver fibrosis.

MATERIALS AND METHODS

This retrospective study included 67 patients (55 male and 12 female; mean age 62.5 years) who underwent gadoxetic acid-enhanced MRI and liver stiffness measurements before liver biopsy or surgery between January 2014 and January 2018. Measurements were performed using transient elastography (TE), ultrasound shear wave elastography point quantification (ElastPQ), and blood tests. The following MRI-based fibrosis markers were assessed: contrast enhancement index (CEI), liver-spleen contrast ratio (LSC), liver-portal vein contrast ratio (LPC), and signal intensity ratio (SIR). The diagnostic performances of fibrosis markers were compared using the area under the receiver operating characteristic curve (AUC), with histopathologic fibrosis stage as the reference standard.

RESULTS

The fibrosis stages were F0-F1 (n = 17), F2 (n = 7), F3 (n = 20), and F4 (n = 23). MRI-based fibrosis markers negatively correlated with histologic stage: CEI (r = -0.786); LSC (r = - 0.718); LPC (r = - 0.448); and SIR (r = - 0.617; all P < 0.001). For diagnosis of either significant liver fibrosis (≥ F2) or cirrhosis (F4), the CEI provided better diagnostic accuracy (AUC = 0.898 and 0.881) than the aspartate aminotransferase-to-platelet ratio index (APRI) (AUC = 0.699 and 0.715; all P < 0.05). The CEI displayed similar diagnostic accuracy for ≥ F2 or F4 when using TE (AUC = 0.866 and 0.884, both P > 0.05) or ElastPQ [AUC = 0.751 (P = 0.021) and AUC = 0.786 (P = 0.234)].

CONCLUSIONS

The CEI measured by gadoxetic acid-enhanced MRI allows the staging of liver fibrosis, with a diagnostic accuracy comparable to that of TE and superior to that of ElastPQ or APRI.

Influence of hepatic fibrosis and inflammation: Correlation between histopathological changes and Gd-EOB-DTPA-enhanced MR imaging

Objective

To evaluate the influence of an active inflammatory process in the liver on Gd-EOB-DTPA-enhanced MR imaging in patients with different degrees of fibrosis/cirrhosis.

Material and methods

Overall, a number of 91 patients (61 men and 30 women; mean age 58 years) were included in this retrospective study. The inclusion criteria for this study were Gd-EOB-DTPA-enhanced MRI of the liver and histopathological evaluation of fibrotic and inflammatory changes. T1-weighted VIBE sequences of the liver with fat suppression were evaluated to determine the relative signal change (RE) between native and hepatobiliary phase (20min). In simple and multiple linear regression analyses, the influence of liver fibrosis/cirrhosis (Ishak score) and the histopathological degree of hepatitis (Modified Hepatic Activity Index, mHAI) on RE were evaluated.

Results

RE decreased significantly with increasing liver fibrosis/cirrhosis (p < 0.001) and inflammation (mHAI, p = 0.004). In particular, a correlation between RE and periportal or periseptal boundary zone hepatitis (moth feeding necrosis, mHAI A, p = 0.001) and portal inflammation (mHAI D, p < 0.001) was observed. In multiple linear regression analysis, both the degree of inflammation and the degree of fibrosis were significant predictors for RE (p < 0.01).

Conclusion

The results of this study suggest that the MR-based hepatic enhancement index RE is not only influenced by the degree of fibrosis, but also by the degree of inflammation.

Evaluation of non-targeting, C- or N-pH (low) insertion peptide modified superparamagnetic iron oxide nanoclusters for selective MRI of liver tumors and their potential toxicity in cirrhosis

Superparamagnetic iron oxide nanoclusters (SPIONs) modified with pH (low) insertion peptide (pHLIP) could be advantageous for magnetic resonance imaging (MRI) diagnosis of liver tumors at the early stage due to their unique responsiveness to the tumor acidic microenvironment when tumor markers are unknown. However, many critical aspects including the effectiveness of selective MRI in liver tumors, types of delivery and the potential safety profile in cirrhosis need to be fully evaluated. In this study, we report the evaluation of non-targeting, C- or N-pHLIP modified SPIONs as the contrast agent for selective MRI of liver tumors and their potential toxicity profile in cirrhosis. It was found that N-pHLIP modified SPIONs did not result in the loss of liver tumor in the T2-weight MRI but provided additional dynamic details of tumor structures that would enhance the diagnosis of liver tumors at a small size below 8 mm. In addition, an enhanced safety profile was found for N-pHLIP modified SPIONs with almost fully recoverable impact in cirrhosis. In contrast, the poly-d-lysine assembled SPIONs and C-terminus linked pHLIP SPIONs had non-tumor specific MRI contrast enhancement and potential safety risks in cirrhosis due to the iron overload post injection. All these results implied the promising potential of N-terminus linked pHLIP SPIONs as an MRI contrast agent for the diagnosis of liver tumors.

The acid-responsive pHLIP modified SPION as an MRI contrast agent for liver cancer diagnosis requires the validation of both the tumor-specific enhancement and a safe profile in cirrhosis.

Amide proton transfer imaging to predict tumor response to neoadjuvant chemotherapy in locally advanced rectal cancer

BACKGROUND AND AIM

The amount of proteins and peptides can be estimated with amide proton transfer (APT) imaging. Previous studies demonstrated the usefulness of APT imaging to predict tumor malignancy. We determined whether APT imaging can predict the tumor response to neoadjuvant chemotherapy (NAC) in patients with locally advanced rectal cancer (LARC).

METHODS

Seventeen patients with LARC who underwent a pretherapeutic magnetic resonance examination including APT imaging and NAC (at least two courses) were enrolled. The APT-weighted imaging (WI) signal intensity (SI) (%) was defined as magnetization transfer ratio asymmetry (MTR_asym ) at the offset of 3.5 ppm. Each tumor was histologically evaluated for the degree of degeneration and necrosis and then classified as one of five histological Grades (0, none; 1a, less than 1/3; 1b, 1/3 to 2/3; 2, more than 2/3; 3, all). We compared the mean APTWI SIs of the tumors between the Grade 0/1a/1b (low-response group) and Grade 2/3 (high-response group) by Student's t-test. We used receiver operating characteristics curves to determine the diagnostic performance of the APTWI SI for predicting the tumor response.

RESULTS

The mean APTWI SI of the low-response group (n = 12; 3.05 ± 1.61%) was significantly higher than that of the high-response group (n = 5; 1.14 ± 1.13%) (P = 0.029). The area under the curve for predicting the tumor response using the APTWI SI was 0.87. When ≥2.75% was used as an indicator of low-response status, 75% sensitivity and 100% specificity of the APTWI SI were obtained.

CONCLUSION

Pretherapeutic APT imaging can predict the tumor response to NAC in patients with LARC.

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.

Diagnostic performance of Gd-EOB-DTPA-enhanced MRI for evaluation of liver dysfunction: a multivariable analysis of 3T MRI sequences

OBJECTIVE

The aim of this study was to evaluate the diagnostic performance of a multiparametric gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced MRI examination for the estimation of liver dysfunction classified by the Model for End-Stage Liver Disease (MELD) score.

RESULTS

Liver dysfunction can be assessed by different methods. In a logistic regression analysis, T1- and T2-weighted images were affected by impaired liver function. In the assessment of liver dysfunction, the reduction rate in T1 mapping sequences showed a significant correlation in simple and multiple logistic regression.

CONCLUSION

Changes in Gd-EOB-DTPA-enhanced MRI between plain images and images obtained during the hepatobiliary phase allowed good prediction of liver dysfunction, especially when using T1 mapping sequences.

MATERIALS AND METHODS

A total of 199 patients underwent contrast-enhanced MRI with a hepatocyte-specific contrast agent at 3T. In the multivariable analysis, the full range of available MRI sequences was used to estimate the liver dysfunction of patients with various MELD scores.

Liver function correlates with liver-to-portal vein contrast ratio during the hepatobiliary phase with Gd-EOB-DTPA-enhanced MR at 3 Tesla

PURPOSES

To determine if liver-to-portal vein contrast ratio (LPC) correlates with liver function in patients with hepatitis B virus (HBV)-related cirrhosis on gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid (Gd-EOB-DTPA)-enhanced MR imaging.

METHODS

A total of 92 patients with normal (n = 20) or HBV-related cirrhotic livers graded by Child-Pugh class A (n = 50), B (n = 17) or C (n = 5) who underwent Gd-EOB-DTPA-enhanced 3Tesla MR imaging were retrospectively reviewed. LPC was defined as the signal intensity ratio of liver parenchyma to portal vein on hepatobiliary phase (HBP) acquired at 20 min, and it was compared between normal and cirrhotic livers. The correlation between LPC and hepatic function parameters at HBP after injection was quantitatively analyzed as well.

RESULTS

LPC differed between normal and cirrhotic livers significantly (P < 0.001). LPC constantly and significantly decreased from normal to cirrhotic livers with Child-Pugh class C at HBP imaging (P < 0.001). Multiple regression analysis revealed that total bilirubin (P = 0.011), albumin (P < 0.001), and platelet count (P = 0.007) were independent predictors of LPC at HBP imaging. A receiver operating characteristic (ROC) curve analysis revealed that the optimal cutoff value for LPC to distinguish normal group from cirrhotic groups was 2.05 (AUC 0.98) with a sensitivity of 84.1% and a specificity of 100%.

CONCLUSION

The level of LPC on Gd-EOB-DTPA MR imaging can efficaciously indicate the severity of liver function in patients with HBV-related cirrhosis and was correlated with liver function parameters significantly. It might be used as an alternative imaging biomarker for assessing liver function.

Hepatobiliary MRI: Signal intensity based assessment of liver function correlated to 13C-Methacetin breath test

Gadoxetic acid (Gd-EOB-DTPA) is a paramagnetic MRI contrast agent with raising popularity and has been used for evaluation of imaging-based liver function in recent years. In order to verify whether liver function as determined by real-time breath analysis using the intravenous administration of ¹³C-methacetin can be estimated quantitatively from Gd-EOB-DTPA-enhanced MRI using signal intensity (SI) values. 110 patients underwent Gd-EOB-DTPA-enhanced 3-T MRI and, for the evaluation of liver function, a ¹³C-methacetin breath test (¹³C-MBT). SI values from before (SI_pre) and 20 min after (SI_post) contrast media injection were acquired by T1-weighted volume-interpolated breath-hold examination (VIBE) sequences with fat suppression. The relative enhancement (RE) between the plain and contrast-enhanced SI values was calculated and evaluated in a correlation analysis of ¹³C-MBT values to SI_post and RE to obtain a SI-based estimation of ¹³C-MBT values. The simple regression model showed a log-linear correlation of ¹³C-MBT values with SI_post and RE (p < 0.001). Stratified by 3 different categories of ¹³C-MBT readouts, there was a constant significant decrease in both SI_post (p ≤ 0.002) and RE (p ≤ 0.033) with increasing liver disease progression as assessed by the ¹³C-MBT. Liver function as determined using real-time ¹³C-methacetin breath analysis can be estimated quantitatively from Gd-EOB-DTPA-enhanced MRI using SI-based indices.

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.

Prediction of high-stage liver fibrosis using ADC value on diffusion-weighted imaging and quantitative enhancement ratio at the hepatobiliary phase of Gd-EOB-DTPA-enhanced MRI at 1.5 T

Background Recently, diffusion-weighted imaging (DWI) and quantitative enhancement ratio measured at the hepatobiliary phase (HBP) of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) has been established as an effective method for evaluating liver fibrosis. Purpose To evaluate which is a more favorable surrogate marker in predicting high-stage liver fibrosis, apparently diffusion coefficient (ADC) value or quantitative enhancement ratio measured on HBP. Material and Methods Eighty-three patients with 99 surgically resected hepatic lesions were enrolled in this study. DWI was performed with b-values of 100 and 800 s/mm². Regions of interest were set on ADC map, and the HBP of Gd-EOB-DTPA-enhanced MRI, to calculate ADC value, liver-to-muscle ratio (LMR), liver-to-spleen ratio (LSR), and contrast enhancement index (CEI) of liver. We compared these parameters between low-stage fibrosis (F0, F1, and F2) and high-stage fibrosis (F3 and F4). Receiver operating characteristic analysis was performed to compare the diagnostic performance when distinguishing low-stage fibrosis from high-stage fibrosis. Results LMR and CEI were significantly lower at high-stage fibrosis than at the low stage ( P < 0.01 and P = 0.04, respectively), whereas LSR did not show a significant difference ( P = 0.053). No significant difference was observed in diagnostic performance between LMR and CEI ( P = 0.185). The best sensitivity and specificity, when an LMR of 2.80 or higher was considered to be low-stage fibrosis, were 82.4% and 75.6%, respectively. ADC value showed no significant differences among fibrosis grades ( P = 0.320). Conclusion LMR and CEI were both adequate surrogate parameters to distinguish high-stage fibrosis from low-stage fibrosis.

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.

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.

Feasibility of histogram analysis of susceptibility-weighted MRI for staging of liver fibrosis

PURPOSE

We aimed to evaluate whether histogram analysis of susceptibility-weighted imaging (SWI) could quantify liver fibrosis grade in patients with chronic liver disease (CLD).

METHODS

Fifty-three patients with CLD who underwent multi-echo SWI (TEs of 2.5, 5, and 10 ms) were included. Histogram analysis of SWI images were performed and mean, variance, skewness, kurtosis, and the 1st, 10th, 50th, 90th, and 99th percentiles were derived. Quantitative histogram parameters were compared. For significant parameters, further receiver operating characteristic (ROC) analyses were performed to evaluate the potential diagnostic performance for differentiating liver fibrosis stages.

RESULTS

The number of patients in each pathologic fibrosis grade was 7, 3, 5, 5, and 33 for F0, F1, F2, F3, and F4, respectively. The results of variance (TE: 10 ms), 90th percentile (TE: 10 ms), and 99th percentile (TE: 10 and 5 ms) in F0-F3 group were significantly lower than in F4 group, with areas under the ROC curves (AUCs) of 0.84 for variance and 0.70-0.73 for the 90th and 99th percentiles, respectively. The results of variance (TE: 10 and 5 ms), 99th percentile (TE: 10 ms), and skewness (TE: 2.5 and 5 ms) in F0-F2 group were smaller than those of F3/F4 group, with AUCs of 0.88 and 0.69 for variance (TE: 10 and 5 ms, respectively), 0.68 for 99th percentile (TE: 10 ms), and 0.73 and 0.68 for skewness (TE: 2.5 and 5 ms, respectively).

CONCLUSION

Magnetic resonance histogram analysis of SWI, particularly the variance, is promising for predicting advanced liver fibrosis and cirrhosis.

Diffusion kurtosis imaging and diffusion-weighted imaging in assessment of liver fibrosis stage and necroinflammatory activity

PURPOSE

To investigate and compare the diagnostic value of diffusion kurtosis imaging (DKI) with diffusion-weighted imaging (DWI) in assessing and quantifying hepatic fibrosis.

METHODS

Thirty rats were divided into the control group (n = 6) and the fibrosis experimental groups (n = 6 per group) with CCl₄ administration for 2, 4, 6, and 8 weeks. Liver fibrosis stage (S) and necroinflammatory activity grade (G) were histopathologically determined. DKI and DWI were performed; mean apparent diffusion (MD), mean kurtosis (MK), and apparent diffusion coefficient (ADC) values were calculated. DKI parameters were compared with ADC values according to G/S scores.

RESULTS

Strong inverse correlations were found between the degree of fibrosis and both MD and ADC (r = -0.840 and r = -0.760), while only weak correlation existed in MK (r = 0.405). ROC analyses demonstrated the AUC in MD, MK, and ADC of 0.862, 0.684, 0.817 for identifying mild and severe fibrosis, and 0.757, 0.675, 0.733 for non-cirrhosis and cirrhosis, respectively. The degree of fibrosis was significantly correlated with α-smooth muscle actin (α-SMA) (P < 0.0001); α-SMA had strong inverse correlation with MD (r = -0.723), moderate inverse correlation with ADC (r = -0.613), and very weak correlation with MK (r = 0.175). Additionally, MD was strongly correlated with the necroinflammatory activity (r = -0.758), ADC was moderately correlated (r = -0.492), and MK was weakly correlated (r = 0.254).

CONCLUSION

DKI may provide added information and serve as a valuable tool for the characterization and surveillance of liver fibrosis in a non-invasive manner.

Functional remnant liver assessment predicts liver-related morbidity after hepatic resection in patients with hepatocellular carcinoma

AIM

We aimed to evaluate whether functional assessment of the future remnant liver is a predictor of postoperative morbidity after hepatic resection in patients with hepatocellular carcinoma (HCC).

METHODS

One hundred forty-six patients who underwent hepatic resection for HCC were enrolled in this study. Gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid enhanced MRI (EOB-MRI) analysis for functional liver assessment was carried out before hepatic resection. The signal intensity in the remnant liver was measured and divided by the signal intensity of the major psoas muscle (the liver to major psoas muscle ratio, LMR) for standardization. The remnant liver function was calculated using the formula (LMR on the hepatobiliary phase/LMR on the precontrast image). Computed tomography liver volumetry was also carried out. The remnant functional liver was calculated as the remnant liver volume or volumetric rate × remnant liver function by EOB-MRI.

RESULTS

Morbidities developed in 19 (13.0%) patients. Morbidities associated with the liver occurred in 7 patients (4.7%). There was no mortality during surgery. Median remnant liver function scores using EOB-MRI and remnant functional liver using volumetric rate or volumetry were 1.82 (range, 1.25-2.96), 155.9 (range, 64.7-285.3), and 1027 (range, 369-2148), respectively. Logistic regression analysis identified the remnant functional liver volume as the only independent predictor for liver-related morbidity.

CONCLUSION

Remnant functional liver volume using computed tomography liver volumetry and EOB-MRI was a significantly useful predictor for liver-related morbidity after hepatic resection in patients with HCC.

Gd-EOB-DTPA-enhanced MRI for evaluation of liver function: Comparison between signal-intensity-based indices and T1 relaxometry

Gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) is a paramagnetic hepatobiliary magnetic resonance (MR) contrast agent. Due to its OATP1B1/B3-dependent hepatocyte-specific uptake and paramagnetic properties increasing evidence has emerged to suggest that Gd-EOB-DTPA-enhanced MRI can be potentially used for evaluation of liver function. In this paper we compare the diagnostic performance of Gd-EOB-DTPA-enhanced relaxometry-based and commonly used signal-intensity (SI)-based indices, including the hepatocellular uptake index (HUI) and SI-based indices corrected by spleen or muscle, for evaluation of liver function, determined using the Indocyanin green clearance (ICG) test. Simple linear regression model showed a significant correlation of the plasma disappearance rate of ICG (ICG-PDR) with all Gd-EOB-DTPA-enhanced MRI-based liver function indices with a significantly better correlation of relaxometry-based indices on ICG-PDR compared to SI-based indices. Among SI-based indices, HUI achieved best correlation on ICG-PDR and no significant difference of respective correlations on ICG-PDR could be shown. Assessment of liver volume and consecutive evaluation of multiple linear regression model revealed a stronger correlation of ICG-PDR with both (SI)-based and T1 relaxometry-based indices. Thus, liver function can be estimated quantitatively from Gd-EOB-DTPA-enhanced MRI-based indices. Here, indices derived from T1 relaxometry are superior to SI-based indices, and all indices benefit from taking into account respective liver volumes.

Can contrast-enhanced MRI with gadoxetic acid predict liver failure and other complications after major hepatic resection?

AIM

To determine whether a combination of clinical factors, the future liver remnant (FLR) ratio, and hepatic uptake of gadoxetic acid can be used to predict post-hepatectomy liver failure (PHLF) and other major complications (OMC).

MATERIALS AND METHODS

Sixty-five consecutive patients who underwent pre-hepatectomy gadoxetic acid-enhanced magnetic resonance imaging (MRI) between October 2010 and December 2013 were included. The relative liver enhancement (RLE) of gadoxetic acid was calculated from regions of interest on MRI, and FLR ratios were obtained from computed tomography (CT). PHLF and OMC were defined by the International Study Group of Liver Surgery criteria and Clavien-Dindo grade of ≥3, respectively. Multivariate logistic regression modelling was performed to identify predictors of PHLF and OMC, including RLE, FLR ratio, age, sex, chemotherapy history, intra-operative blood loss, and intra-operative transfusion.

RESULTS

Nine patients experienced PHLF and another nine patients experienced OMC. RLE was comparable to the FLR ratio in predicting PHLF (areas under the receiver operating characteristic [AUROC] curves, 0.665 and 0.705), but performed poorly in predicting OMCs (AUROCs, 0.556 and 0.702). Combining all clinical and imaging parameters as predictors yielded the best performing predictive models (AUROCs, 0.875 and 0.742 for PHLF and OMC, respectively).

CONCLUSION

A model based on clinical parameters, the FLR ratio, and RLE of gadoxetic acid may improve pre-hepatectomy risk assessment.

A comprehensive literatures update of clinical researches of superparamagnetic resonance iron oxide nanoparticles for magnetic resonance imaging

This paper aims to update the clinical researches using superparamagnetic iron oxide (SPIO) nanoparticles as magnetic resonance imaging (MRI) contrast agent published during the past five years. PubMed database was used for literature search, and the search terms were (SPIO OR superparamagnetic iron oxide OR Resovist OR Ferumoxytol OR Ferumoxtran-10) AND (MRI OR magnetic resonance imaging). The literature search results show clinical research on SPIO remains robust, particularly fuelled by the approval of ferumoxytol for intravenously administration. SPIOs have been tested on MR angiography, sentinel lymph node detection, lymph node metastasis evaluation; inflammation evaluation; blood volume measurement; as well as liver imaging. Two experimental SPIOs with unique potentials are also discussed in this review. A curcumin-conjugated SPIO can penetrate brain blood barrier (BBB) and bind to amyloid plaques in Alzheime's disease transgenic mice brain, and thereafter detectable by MRI. Another SPIO was fabricated with a core of Fe3O4 nanoparticle and a shell coating of concentrated hydrophilic polymer brushes and are almost not taken by peripheral macrophages as well as by mononuclear phagocytes and reticuloendothelial system (RES) due to the suppression of non-specific protein binding caused by their stealthy ''brush-afforded'' structure. This SPIO may offer potentials for the applications such as drug targeting and tissue or organ imaging other than liver and lymph nodes.

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.

Nanomaterials for In Vivo Imaging

In vivo imaging, which enables us to peer deeply within living subjects, is producing tremendous opportunities both for clinical diagnostics and as a research tool. Contrast material is often required to clearly visualize the functional architecture of physiological structures. Recent advances in nanomaterials are becoming pivotal to generate the high-resolution, high-contrast images needed for accurate, precision diagnostics. Nanomaterials are playing major roles in imaging by delivering large imaging payloads, yielding improved sensitivity, multiplexing capacity, and modularity of design. Indeed, for several imaging modalities, nanomaterials are now not simply ancillary contrast entities, but are instead the original and sole source of image signal that make possible the modality's existence. We address the physicochemical makeup/design of nanomaterials through the lens of the physical properties that produce contrast signal for the cognate imaging modality-we stratify nanomaterials on the basis of their (i) magnetic, (ii) optical, (iii) acoustic, and/or (iv) nuclear properties. We evaluate them for their ability to provide relevant information under preclinical and clinical circumstances, their in vivo safety profiles (which are being incorporated into their chemical design), their modularity in being fused to create multimodal nanomaterials (spanning multiple different physical imaging modalities and therapeutic/theranostic capabilities), their key properties, and critically their likelihood to be clinically translated.

[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.

Histogram analysis of noncancerous liver parenchyma on gadoxetic acid-enhanced MRI: predictive value for liver function and pathology

PURPOSE

To clarify whether the heterogeneity of hepatic parenchyma in the hepatobiliary phase on gadoxetic acid-magnetic resonance (MR) imaging is correlated with liver damage.

MATERIALS AND METHODS

We retrospectively examined the cases of 98 patients with or without chronic liver disease who underwent gadoxetic acid-enhanced 3T MR imaging before a hepatectomy between December 2010 and October 2014. For the evaluation of the heterogeneity of the signal intensity in the hepatobiliary phase, we placed the region of interest on the hepatic parenchyma, and the skewness and kurtosis were calculated using ImageJ software. A discriminant analysis was performed to examine the routine preoperative laboratory test results including indocyanine green retention at 15 min (ICG-R15), necro-inflammation grade, and liver fibrosis stage according to the METAVIR system: A0/1 (n = 69) and A2 (n = 29); F0/1 (n = 47), F2/3 (n = 31), and F4 (n = 20).

RESULTS

The combination of skewness and kurtosis could discriminate the high ICG-R15 (>20) and low (<20) groups (lambda; 0.925, p = 0.025), necro-inflammatory grade (lambda; 0.926, p = 0.026), and fibrosis stage (lambda; 0.752, p < 0.0001) with statistical significance. The difference between the patients with normal values and those with an abnormal platelet count or aspartate transaminase level was also detectable (lambda; 0.901, p < 0.007, and lambda; 0.864, p = 0.001, respectively).

CONCLUSION

Histogram analyses of the hepatobiliary phase of gadoxetic acid-enhanced MR imaging have potential as a biomarker for the assessment of liver function, liver fibrosis, and necro-inflammation.

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.

Stability of liver proton density fat fraction and changes in R 2* measurements induced by administering gadoxetic acid at 3T MRI

OBJECTIVE

To assess changes in liver proton density fat fraction (PDFF) and R 2* measurements in the presence of changes in tissue relaxation rates induced by administrating gadoxetic acid, using two different image reconstruction methods at 3T MRI.

METHODS

Forty-five patients were imaged at 3T with chemical-shift-based MRI sequences before and 20 min after administration of gadoxetic acid. Image reconstructions were performed using hybrid and complex methods to obtain PDFF and R 2* images. A single radiologist measured PDFF and R 2* values on precontrast and postcontrast images. Precontrast and postcontrast PDFF values were compared using intraclass correlation coefficient (ICC), linear regression, and Bland-Altman analysis. Changes in R 2* values from precontrast to postcontrast were correlated with relative liver enhancement (RLE) based on signal intensities on T 1-weighted images using Spearman's rank correlation.

RESULTS

PDFF values were similar between precontrast and postcontrast images (ICC = 0.99, linear regression slopes = 0.98, mean difference = -0.21 to -0.31%). PDFF measurements were stable between precontrast and postcontrast images. Changes in R 2* values were correlated with RLE (p < 0.001, r = 0.49-0.71).

CONCLUSIONS

PDFF measurements from both image reconstruction methods are stable in the presence of changes in tissue relaxation rates after administering gadoxetic acid at 3T MRI. Changes in R 2* values correlate with established measures of gadoxetic acid uptake based on T 1-weighted images.

MR Prediction of Liver Function and Pathology Using Gd-EOB-DTPA: Effect of Liver Volume Consideration

Purpose. To evaluate whether the diagnostic performance of Gd-EOB-DTPA-enhanced MRI in evaluating liver function and pathology is improved by considering liver volume (LV). Methods. This retrospective study included 104 patients who underwent Gd-EOB-DTPA-enhanced MRI before liver surgery. For each patient, using the precontrast and hepatobiliary phase images, we calculated the increase rate of the liver-to-spleen signal intensity ratio (LSR), that is, the “ΔLSR,” and the increase rate of the liver-to-muscle signal intensity ratio (LMR), that is, the “ΔLMR.” ΔLSR × LV and ΔLMR × LV were also calculated. The correlation of each MR parameter with liver function data or liver pathology was assessed. The correlation coefficients were compared between ΔLSR (ΔLMR) and ΔLSR (ΔLMR) × LV. Results. The correlation coefficient between ΔLSR (ΔLMR) × LV and cholinesterase was significantly higher than that between ΔLSR (ΔLMR) and cholinesterase. The correlation coefficient between ΔLSR (ΔLMR) × LV and the degree of fibrosis or necroinflammatory activity was significantly lower than that between ΔLSR (ΔLMR) and the degree of fibrosis or necroinflammatory activity. Conclusion. The inclusion of liver volume may improve Gd-EOB-DTPA-based predictions of liver function, but not in predictions of liver pathology.

Liver fibrosis and Gd-EOB-DTPA-enhanced MRI: A histopathologic correlation

Gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) is a hepatocyte-specific MRI contrast agent. Because the hepatic uptake of Gd-EOB-DTPA depends on the integrity of the hepatocyte mass, this uptake can be quantified to assess liver function. We report the relationship between the extent of Gd-EOB-DTPA uptake and the degree of liver fibrosis. T1-weighted volume-interpolated breath-hold examination (VIBE) sequences with fat suppression were acquired before and 20 minutes after contrast injection. Strong correlations of the uptake characteristics of Gd-EOB-DTPA with the relative enhancement (RE) of the liver parenchyma and the grade of fibrosis/cirrhosis, classified using the Ishak scoring system, were observed. The subdivisions between the grades of liver fibrosis based on RE were highly significant for all combinations, and a ROC revealed sensitivities ≥82% and specificities ≥87% for all combinations. MR imaging is a satisfactorily sensitive method for the assessment of liver fibrosis/cirrhosis.

The diagnostic efficacy of quantitative liver MR imaging with diffusion-weighted, SWI, and hepato-specific contrast-enhanced sequences in staging liver fibrosis--a multiparametric approach

PURPOSE

To assess the diagnostic efficacy of multiparametric MRI using quantitative measurements of the apparent diffusion coefficient (ADC) of the liver parenchyma on diffusion-weighted imaging (DWI), signal intensity (SI) on susceptibility-weighted imaging (SWI), and gadoxetic acid-enhanced T1-weighted imaging during the hepatobiliary phase for the staging of liver fibrosis.

MATERIALS AND METHODS

Seventy-seven patients underwent a 3T MRI examination, including DWI/SWI sequences and gadoxetic acid-enhanced T1-weighted MRI. Liver fibrosis according to liver biopsy was staged using the Metavir fibrosis score: F0 (n = 21, 27.3%); F1 (n = 7, 9.1%); F2 (n = 8, 10.4%); F3 (n = 12, 15.6%); and F4 (n = 29, 37.7%). SI of the liver was defined using region-of-interest measurements to calculate the ADC values, the relative enhancement (RE) in the hepatobiliary phase, and the liver-to-muscle ratio (LMR) measurements for SWI.

RESULTS

The values of RE, LMR, and ADC measurements were statistically significantly different among the five fibrosis stages (p < 0.004). Combining the three parameters in a multiparametric approach, the AUC for detecting F1 stage or greater (≥ F1) was 94%, for F2 or greater (≥F2) was 95%, for F3 or greater (≥F3) was 90%, and for stage F4 was 93%.

CONCLUSIONS

Multiparametric MRI is an efficient non-invasive diagnostic tool for the staging of liver fibrosis.

KEY POINTS

• Multiparametric MRI has high accuracy in predicting moderate or greater liver fibrosis. • Relative enhancement post- gadoxetic acid is an independent predictor of liver fibrosis. • Liver SWI signal intensity and ADC values enhance the diagnostic ability.

A novel serum marker, glycosylated Wisteria floribunda agglutinin-positive Mac-2 binding protein (WFA(+)-M2BP), for assessing liver fibrosis

BACKGROUND

Recently, a novel marker, hyperglycosylated Wisteria floribunda agglutinin-positive Mac-2 binding protein (WFA(+)-M2BP), was developed for liver fibrosis using the glycan "sugar chain"-based immunoassay; however, the feasibility of WFA(+)-M2BP for assessing liver fibrosis has not been proven with clinical samples of hepatitis.

METHODS

Serum WFA(+)-M2BP values were evaluated in 200 patients with chronic liver disease who underwent histological examination of liver fibrosis. The diagnostic accuracy of WFA(+)-M2BP values was compared with various fibrosis markers, such as ultrasound based-virtual touch tissue quantification (VTTQ), magnetic resonance imaging based-liver-to-major psoas muscle intensity ratio (LMR), and serum markers, including hyaluronic acid, type 4 collagen, and aspartate transaminase to platelet ratio index (APRI).

RESULTS

Serum WFA(+)-M2BP levels in patients with fibrosis grades F0, F1, F2, F3, and F4 had cutoff indices 1.62, 1.82, 3.02, 3.32, and 3.67, respectively, and there were significant differences between fibrosis stages F1 and F2, and between F2 and F3 (P < 0.01). The area under the receiver operating characteristic curves for the diagnosis of fibrosis (F ≥ 3) using serum WFA(+)-M2BP values (0.812) was almost comparable to that using VTTQ examination (0.814), but was superior to the other surrogate markers, including LMR index (0.766), APRI (0.694), hyaluronic acid (0.683), and type 4 collagen (0.625) (P < 0.01 each).

CONCLUSIONS

Serum WFA(+)-M2BP values based on a glycan-based immunoassay is an accurate, reliable, and reproducible method for the assessment of liver fibrosis. This approach could be clinically feasible for evaluation of beneficial therapy through the quantification of liver fibrosis in hepatitis patients if this measurement application is commercially realized.