Contrast enhanced liver MRI in patients with primary sclerosing cholangitis: inverse appearance of focal confluent fibrosis on delayed phase MR images with hepatocyte specific versus extracellular gadolinium based contrast agents

Differentiation of confluent hepatic fibrosis and infiltrative hepatocellular carcinoma on MR imaging

BACKGROUND

To identify reliable magnetic resonance imaging (MRI) features that can differentiate confluent fibrosis (CF) from infiltrative hepatocellular carcinoma (HCC).

METHODS

A retrospective analysis was conducted on Twenty CF patients and 28 infiltrative HCC patients who underwent upper abdomen MRI scans. The imaging features of lesions were analyzed, and the apparent diffusion coefficient (ADC) of lesions were measured. Accuracy, sensitivity and specificity for the diagnosis of CF were calculated for each category individually and combined.

RESULTS

Compared to infiltrative HCC, hepatic capsular retraction at the site of lesion, hepatic volume loss at the site of lesion and "nodular surround sign" were more common in patients with CF (all P < 0.001). Hepatic volume loss at the site of lesion, no or mild enhancement in arterial phase, and hyper-enhancing in delayed phase to the background parenchyma showed superior diagnostic accuracy (83.3%, 85.4%, 97.9%, respectively). When the lesion exhibited hepatic volume loss at the site of lesion or no or mild enhancement in arterial phase or hyper-enhancing in delayed phase, a sensitivity of 100.0% for the diagnosis of CF was achieved. When the lesion was positive for any two of three categories, or positive for all three categories, a specificity of 100.0% was achieved. The ADC values of CF were higher than those of infiltrative HCC (P < 0.001).

CONCLUSION

The combination of the hepatic volume loss at the site of lesion, no or mild enhancement in arterial phase, and hyper-enhancing in delayed phase to the background parenchyma can be considered reliable MR features for the diagnosis of CF, as they allow differentiation from infiltrative HCC.

Primary Sclerosing Cholangitis: Diagnostic Criteria

Primary sclerosing cholangitis is a chronic cholestatic liver disease characterized by inflammation and fibrosis of intra- and/or extrahepatic bile ducts leading to the formation of multifocal strictures alternated to bile duct dilatations. The diagnosis of the most common subtype of the disease, the large duct PSC, is based on the presence of elevation of cholestatic indices, the association of typical cholangiographic findings assessed by magnetic resonance cholangiography and the exclusion of causes of secondary sclerosing cholangitis. Liver biopsy is not routinely applied for the diagnosis of large duct PSC but is mandatory in the case of suspicion of small duct PSC or overlap with autoimmune hepatitis.

Clinic-radiomics model using liver magnetic resonance imaging helps predict chronicity of drug-induced liver injury

BACKGROUND AND AIMS

Some drug-induced liver injury (DILI) cases may become chronic, even after drug withdrawal. Radiomics can predict liver disease progression. We established and validated a predictive model incorporating the clinical characteristics and radiomics features for predicting chronic DILI.

METHODS

One hundred sixty-eight DILI patients who underwent liver gadolinium-diethylenetriamine pentaacetate-enhanced magnetic resonance imaging were recruited. The patients were clinically diagnosed using the Roussel Uclaf causality assessment method. Patients who progressed to chronicity or recovery were randomly divided into the training (70%) and validation (30%) cohorts, respectively. Hepatic T1-weighted images were segmented to extract 1672 radiomics features. Least absolute shrinkage and selection operator regression was used for feature selection, and Rad-score was constructed using support vector machines. Multivariable logistic regression analysis was performed to build a clinic-radiomics model incorporating clinical characteristics and Rad-scores. The clinic-radiomics model was evaluated for its discrimination, calibration, and clinical usefulness in the independent validation set.

RESULTS

Of 1672 radiomics features, 28 were selected to develop the Rad-score. Cholestatic/mixed patterns and Rad-score were independent risk factors of chronic DILI. The clinic-radiomics model, including the Rad-score and injury patterns, distinguished chronic from recovered DILI patients in the training (area under the receiver operating characteristic curve [AUROC]: 0.89, 95% confidence interval [95% CI]: 0.87-0.92) and validation (AUROC: 0.88, 95% CI: 0.83-0.91) cohorts with good calibration and great clinical utility.

CONCLUSION

The clinic-radiomics model yielded sufficient accuracy for predicting chronic DILI, providing a practical and non-invasive tool for managing DILI patients.

Imaging Spectrum of Intrahepatic Mass-Forming Cholangiocarcinoma and Its Mimickers: How to Differentiate Them Using MRI

Intrahepatic cholangiocarcinoma (ICC) is the second most common primary hepatic malignancy, with mass-forming growth pattern being the most common. The typical imaging appearance of mass-forming ICC (mICC) consists of irregular ring enhancement in the arterial phase followed by the progressive central enhancement on portal venous and delayed phases. However, atypical imaging presentation in the form of hypervascular mICC might also be seen, which can be attributed to distinct pathological characteristics. Ancillary imaging features such as lobular shape, capsular retraction, segmental biliary dilatation, and vascular encasement favor the diagnosis of mICC. Nevertheless, these radiological findings may also be present in certain benign conditions such as focal confluent fibrosis, sclerosing hemangioma, organizing hepatic abscess, or the pseudosolid form of hydatid disease. In addition, a few malignant lesions including primary liver lymphoma, hemangioendothelioma, solitary hypovascular liver metastases, and atypical forms of hepatocellular carcinoma (HCC), such as scirrhous HCC, infiltrative HCC, and poorly differentiated HCC, may also pose a diagnostic dilemma by simulating mICC in imaging studies. Diffusion-weighted imaging and the use of hepatobiliary contrast agents might be helpful for differential diagnosis in certain cases. The aim of this manuscript is to provide a comprehensive overview of mICC imaging features and to describe useful tips for differential diagnosis with its potential mimickers.

Morphological, dynamic and functional characteristics of liver pseudolesions and benign lesions

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide and one of the most common causes of death among patients with cirrhosis, developing in 1-8% of them every year, regardless of their cirrhotic stage. The radiological features of HCC are almost always sufficient for reaching the diagnosis; thus, histological confirmation is rarely needed. However, the study of cirrhotic livers remains a challenge for radiologists due to the developing of fibrous and regenerative tissue that cause the distortion of normal liver parenchyma, changing the typical appearances of benign lesions and pseudolesions, which therefore may be misinterpreted as malignancies. In addition, a correct distinction between pseudolesions and malignancy is crucial to allow appropriate targeted therapy and avoid treatment delays.The present review encompasses technical pitfalls and describes focal benign lesions and pseudolesions that may be misinterpreted as HCC in cirrhotic livers, providing the imaging features of regenerative nodules, large regenerative nodules, siderotic nodules, hepatic hemangiomas (including rapidly filling and sclerosed hemangiomas), segmental hyperplasia, arterioportal shunts, focal confluent fibrosis and focal fatty changes. Lastly, the present review explores the most promising new imaging techniques that are emerging and that could help radiologists differentiate benign lesions and pseudolesions from overt HCC.

Imaging-based diagnosis of benign lesions and pseudolesions in the cirrhotic liver

Liver cirrhosis is a leading cause of death worldwide, with 1-year mortality rates of up to 57% in decompensated patients. Hepatocellular carcinoma (HCC) is the most common primary tumor in cirrhotic livers and the second leading cause of cancer-related mortality worldwide. Annually, up to 8% of patients with cirrhosis develop HCC. The diagnosis of HCC rarely requires histological confirmation: in fact, according to the most recent guidelines, the imaging features of HCC are almost always sufficient for a certain diagnosis. Thus, the role of the radiologist is pivotal because the accurate detection and characterization of focal liver lesions in patients with cirrhosis are essential in improving clinical outcomes. Despite recent technical innovations in liver imaging, several issues remain for radiologists regarding the differentiation of HCC from other hepatic lesions, particularly benign lesions and pseudolesions. It is important to avoid misdiagnosis of benign liver lesions as HCC (false-positive cases) because this diagnostic misinterpretation may lead to ineligibility of a patient for potentially curative treatments or inappropriate assignment of high priority scores to patients on waiting lists for liver transplantation. This review presents a pocket guide that could be useful for the radiologist in the diagnosis of benign lesions and pseudolesions in cirrhotic livers, highlighting the imaging features that help in making the correct diagnosis of macroregenerative nodules; siderotic nodules; arterioportal shunts; hemangiomas, including fast-filling hemangiomas, hemangiomas with pseudowashout, and sclerosed hemangiomas; confluent fibrosis; pseudomasses in chronic portal vein thrombosis; and focal fatty changes.

A case of focal confluent hepatic fibrosis in the patient with hepatitis C virus-related liver cirrhosis: a mimic of cholangiolocellular carcinoma

During routine ultrasound examination, a hyperechoic mass was detected in the anterior segment of the liver in an 80-year-old woman with hepatitis C virus-related cirrhosis. Computed tomography and magnetic resonance imaging findings suggested a malignant tumor with abundant fibrous stroma, similar to cholangiolocellular carcinoma. However, subsequent partial hepatectomy revealed a mass characterized by abundant fibrosis without tumor cells, dilated blood vessels, and marginal ductular reaction. Accordingly, focal confluent fibrosis was diagnosed. Generally, the diagnosis of focal confluent fibrosis is straightforward because of its well-established imaging characteristics. However, its differentiation from a malignant tumor can occasionally be difficult because of variation in presentation depending on the amount of fibrous stroma and the degree of inflammatory cell infiltration. In the present case, diagnosis was difficult because the lesion was more localized than usual, presenting a mass-like shape, and there was obvious hyperintensity on T2-weighted imaging and ring-shaped hyperintensity on diffusion-weighted imaging. Moreover, hepatic capsular retraction was indistinct, which can be one of the key findings of focal confluent fibrosis. When a hepatic mass is associated with a fibrous lesion, focal confluent fibrosis should be considered in the differential diagnosis, even though the lesion is associated with several atypical findings.

Focal lesions in cirrhosis: Not always HCC

Even though most hepatocellular carcinomas (HCC) develop in the setting of cirrhosis, numerous other focal liver lesions and pseudolesions may be encountered. The role of the radiologist is therefore to differentiate these lesions from HCC to avoid under- and overdiagnosis. There are several ways of classifying these lesions: those which predate the development of fibrosis and cirrhosis (cystic lesions, hemangioma), those related to or a consequence of cirrhosis (regenerative nodules, dysplastic nodules, focal fibrosis, peribiliary cysts, shunts, or even cholangiocarcinoma), and those related to the underlying cause of chronic liver disease (lymphoma). Finally, some may develop independently (liver metastases). From an imaging point of view, it is important to remember that the imaging features of pre-existing lesions are not dramatically changed by cirrhosis. Differentiating non-HCC from HCC requires not only an understanding of the multi-step process of hepatocarcinogenesis, but also the importance of medical history, and of complimentary imaging modalities, namely computed tomography (CT) and magnetic resonance imaging (MRI). This review article gives an overview of the imaging features of benign and malignant non-HCC focal liver lesions in the setting of cirrhosis, with a focus on CT and MR imaging.

[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.

MR-imaging features of hepatocellular carcinoma capsule appearance in cirrhotic liver: comparison of gadoxetic acid and gadobenate dimeglumine

PURPOSE

The purpose of the study is to compare the MR-imaging features of hepatocellular carcinoma (HCC) capsule appearance on gadoxetic acid and gadobenate dimeglumine-enhanced MR imaging, using imaging-based presumptive diagnosis of HCC as the reference standard.

METHODS

Gadoxetic acid and gadobenate dimeglumine-enhanced MR imaging of 51 patients with 71 HCCs were retrospectively reviewed. Three readers graded in consensus, using a five-point scale, the presence (score 4-5) of capsule appearance on images obtained during T1-weighted GRE portal venous phase (PVP), 3-min phase, and hepatobiliary phase (HBP). The Fisher's exact test and the t student unpaired test were performed.

RESULTS

A hyperintense capsule appearance was present either on PVP or 3-min phase in 11/46 and in 24/25 HCCs imaged with gadoxetic acid and gadobenate dimeglumine-enhanced MR imaging, respectively (24% vs. 96% p < 0.001). A hypointense capsule appearance was present on HBP in 8/46 and 0/22 HCCs evaluated with gadoxetic acid and gadobenate dimeglumine-enhanced MR imaging, respectively (17% vs. 0% p = 0.046). A capsule appearance was detected either on PVP, 3-min phase, or HBP in 17/46 (37%) HCCs after gadoxetic acid injection and in 24/25 (96%) HCCs after gadobenate dimeglumine injection (p < 0.001).

CONCLUSIONS

A capsule appearance was more frequently seen on gadobenate dimeglumine-enhanced MR imaging when compared to gadoxetic acid-enhanced MR imaging.

Differentiation of lipid poor angiomyolipoma from hepatocellular carcinoma on gadoxetic acid-enhanced liver MR imaging

PURPOSE

To investigate magnetic resonance (MR) findings of angiomyolipoma (AML) on gadoxetic acid-enhanced MR imaging, and to identify features that differentiate AML from hepatocellular carcinoma (HCC) in patients with a low risk of HCC development.

METHODS

This retrospective study was institutional review board approved, and the requirement for informed consent was waived. Twelve patients with hepatic AML who underwent gadoxetic acid-enhanced MRI with no risk factors for HCC development were recruited. Twenty-seven patients with HCC under the same inclusion criteria were recruited as control. Two radiologists analyzed the images in consensus for morphologic features, enhancement patterns, and hepatobiliary phase (HBP) findings. All results were analyzed using the Mann-Whitney test, two-tailed Fisher exact test, and chi-square test.

RESULTS

Patients with AML were younger than those with HCC (48.8 ± 15 years for AML vs. 62.7 ± 14.2 years for HCC, p = 0.008) with female predominance, while most HCC patients were male (75% (9/12) vs. 15% (4/27), p < 0.001). The most prevalent enhancement pattern was arterial enhancement followed by hypointensity at portal or transitional phases for both AMLs (58% (7/12)) and HCCs (74% (20/27)) (p = 0.455). However, during the HBP, AMLs frequently showed more homogeneous hypointensity than HCCs (83% (10/12) vs. 41% (11/27), p = 0.018). When compared with the signal intensity of the spleen, the mean relative signal intensity of the AML was 91.2 ± 15.4%, while in HCCs, it was 128.7 ± 40% (p < 0.001).

CONCLUSIONS

Although AMLs showed similar enhancement patterns to HCCs during the dynamic phases of gadoxetic acid-enhanced MRI, using characteristic MR features of AML during the HBP and demographic differences, one can better differentiate AML from HCC.

Differentiation of intrahepatic mass-forming cholangiocarcinoma from hepatocellular carcinoma on gadoxetic acid-enhanced liver MR imaging

OBJECTIVES

To determine the different imaging features of intrahepatic mass-forming cholangiocarcinoma (IMCC) from hepatocellular carcinoma (HCC) on gadoxetic acid-enhanced magnetic resonance imaging (MRI).

METHODS

This retrospective study was institutional review board approved and the requirement for informed consent was waived. Patients who underwent gadoxetic acid-enhanced MRI with histologically confirmed IMCCs (n = 46) or HCCs (n = 58) were included. Imaging features of IMCCs and HCCs on gadoxetic acid-enhanced MRI including T2- and T1-weighted, diffusion weighted images, dynamic study and hepatobiliary phase (HBP) images were analyzed. Univariate and multivariate logistic regression analyses were performed to identify relevant differentiating features between IMCCs and HCCs.

RESULTS

Multivariate analysis revealed heterogeneous T2 signal intensity and a hypointense rim on the HBP as suggestive findings of IMCCs and the wash-in and "portal wash-out" enhancement pattern as well as focal T1 high signal intensity foci as indicative of HCCs (all, p < 0.05). When we combined any three of the above four imaging features, we were able to diagnose IMCCs with 94 % (43/46) sensitivity and 86 % (50/58) specificity.

CONCLUSIONS

Combined interpretation of enhancement characteristics including HBP images, morphologic features, and strict application of the "portal wash-out" pattern helped more accurate discrimination of IMCCs from HCCs.

KEY POINTS

• Analysis of enhancement characteristics helped accurate discrimination of IMCCs from HCCs. • Wash-out should be determined on the PVP of gadoxetic acid-enhanced MRI. • A hypointense rim on the HBP was a significant finding of IMCCs.

Functional gadoxetate disodium-enhanced MRI in patients with primary sclerosing cholangitis (PSC)

OBJECTIVES

To assess the value of variable flip angle-based T1 liver mapping on gadoxetate disodium-enhanced MRI in patients with primary sclerosing cholangitis (PSC) for evaluation of global and segmental liver function, and determine a possible correlation with disease severity.

METHODS

Sixty-one patients (19 female, 42 male; mean age 41 years) with PSC were included in this prospective study. T1 mapping was performed using a 3D-spoiled GRE sequence (flip angles 5°, 15°, 20°, 30°) before, 16 (HP1) and 132 min (HP2) after contrast injection. T1 values were measured and compared (Wilcoxon-Test) by placing ROIs in each liver segment. The mean reduction of T1 relaxation time at HP1 and HP2 was calculated and correlated with liver function tests (LFTs), MELD, Mayo Risk and Amsterdam Scores (Spearman correlation).

RESULTS

Significant changes of T1 relaxation times between non-enhanced and gadoxetate disodium-enhanced MRI at HP1 and HP2 could be observed in all liver segments (p < 0.0001). A significant correlation of T1 reduction could be observed with LFTs, MELD and Mayo Risk Score (p < 0.05).

CONCLUSIONS

T1 mapping of the liver using a variable flip angle-based sequence is a feasible technique to evaluate liver function on a global level, and may be extrapolated on a segmental level in patients with PSC.

KEY POINTS

• T1 mapping enables evaluation of global liver function in PSC. • T1 relaxation time reduction correlates with the MELD and MayoRisk Score. • Extrapolated, T1 mapping may allow for segmental evaluation of liver function.

P4 radiology of hepatobiliary diseases with gadoxetic acid-enhanced MRI as a biomarker

A recent paradigm shift in radiology has focused on the globalization of so-called P4 radiology. P4 radiology represents delivery of imaging results that are predictive, personalized, pre-emptive and participatory. The combination of the P4 approach and biomarkers is particularly pertinent to MRI, especially with technological advances such as diffusion-weighted imaging. The development of new liver-specific MRI contrast media, particularly gadoxetic acid, demonstrate specific pharmacokinetic properties, which provide combined morphologic and functional information in the same setting. The evaluation of hepatobiliary pathology beyond morphology gives rise to the possibilty of using gadoxetic acid-enhanced MRI as an imaging biomarker of hepatobiliary diseases. The integration of functional imaging with an understanding of complex disease mechanisms forms the basis for P4 radiology, which may ultimately lead to individualized, cost-effective, targeted therapy for patients. This will enable radiologists to determine the prognosis of the disease and estimate early response to treatment, with the participation of all the required medical disciplines.

Primovist, Eovist: what to expect?

Gadolinium ethoxybenzyl dimeglumine (Gd-EOB-DTPA, Primovist in Europe and Eovist in the USA) is a liver-specific magnetic resonance imaging contrast agent that has up to 50% hepatobiliary excretion in the normal liver. After intravenous injection, Gd-EOB-DTPA distributes into the vascular and extravascular spaces during the arterial, portal venous and late dynamic phases, and progressively into the hepatocytes and bile ducts during the hepatobiliary phase. The hepatocyte uptake of Gd-EOB-DTPA mainly occurs via the organic anion transporter polypeptides OATP1B1 and B3 located at the sinusoidal membrane and biliary excretion via the multidrug resistance-associated proteins MRP2 at the canalicular membrane. Because of these characteristics, Gd-EOB-DTPA behaves similarly to non-specific gadolinium chelates during the dynamic phases, and adds substantial information during the hepatobiliary phase, improving the detection and characterization of focal liver lesions and diffuse liver disease. This information is particularly relevant for the detection of metastases, and for the detection and characterization of nodular lesions in liver cirrhosis, including early hepatocellular carcinomas. Finally, GD-EOB-DTPA-enhanced magnetic resonance imaging may provide quantitative assessment regarding liver perfusion and hepatocyte function in diffuse liver diseases. The full potential of GD-EOB-DTPA-enhanced magnetic resonance imaging has to be established further. It is already clear that GD-EOB-DTPA-enhanced magnetic resonance imaging provides anatomic and functional information in the setting of focal and diffuse liver disease that is unattainable with magnetic resonance imaging enhanced with non-specific contrast agents.