Gadolinium-enhanced imaging of liver tumors and manifestations of hepatitis: pharmacodynamic and technical considerations

ACR Appropriateness Criteria® Abnormal Liver Function Tests

Liver function tests are commonly obtained in symptomatic and asymptomatic patients. Various overlapping lab patterns can be seen due to derangement of hepatocytes and bile ducts function. Imaging tests are pursued to identify underlying etiology and guide management based on the lab results. Liver function tests may reveal mild, moderate, or severe hepatocellular predominance and can be seen in alcoholic and nonalcoholic liver disease, acute hepatitis, and acute liver injury due to other causes. Cholestatic pattern with elevated alkaline phosphatase with or without elevated γ-glutamyl transpeptidase can be seen with various causes of obstructive biliopathy. Acute or subacute cholestasis with conjugated or unconjugated hyperbilirubinemia can be seen due to prehepatic, intrahepatic, or posthepatic causes. We discuss the initial and complementary imaging modalities to be used in clinical scenarios presenting with abnormal liver function tests. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

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.

The role of dynamic and diffusion MR imaging in therapeutic response assessment after microwave ablation of hepatocellular carcinoma using LI-RADS v2018 treatment response algorithm

Background

Hepatocellular carcinoma (HCC) is considered as one of the major causes of morbidity and mortality worldwide. Microwave ablation (MWA) is a widely used treatment option having less morbidity and complications as compared with surgery and liver transplantation. MRI is the most widely used modality in the assessment of treatment response after MWA. Currently, LI-RADS v2018 algorithm is considered the cornerstone in daily clinical practice for assessment of the treatment response after locoregional therapy. The aim of the study was to assess the role of dynamic MRI and diffusion imaging in the assessment of treatment response and detection of tumor viability following microwave ablation therapy of HCC according to LI-RADS v2018 treatment response algorithm.

Results

This retrospective study was performed over 45 HCC lesions underwent MWA as the only therapeutic procedure and followed up by dynamic MRI with diffusion images and then classified according to the LI-RADS treatment response criteria into LR-TR viable and LR-TR nonviable groups. All the malignant lesions found in this study showed arterial phase hyperenhancment (APHE), whether in the early or late arterial phases. Delayed washout was found in all malignant lesions as well. In the diffusion analysis, the mean ADC value for the malignant lesions was 0.900 ± 0.126 × 10-3 mm2/s, while the mean ADC of the treatment-related specific benign parenchymal enhancement was 1.284 ± 0.129 × 10-3 mm2/s with a significant statistical difference in between (P = 0.0001) and a cutoff value of 1.11 × 10-3 mm2/s. Our findings showed that the dynamic MRI has 100% sensitivity, 93.5% specificity, 87.5% PPV, and 100% NPV in the detection of tumoral activity compared with 71.43% sensitivity, 93.55% specificity, 83.33% PPV, and 87.88% NPV for diffusion images.

Conclusion

LI-RADS 2018 provides a treatment response algorithm superior to the previously used assessment criteria. MRI with dynamic contrast-enhanced technique and diffusion imaging provide a powerful tool in the evaluation of treatment response after microwave ablation of hepatocellular carcinoma using the LI-RADS treatment response criteria and is considered a reliable method in differentiating between the recurrent or residual malignant lesions and the posttreatment benign liver changes.

Detection of Dysplastic Liver Nodules in Patients with Cirrhosis Using the Multi-Arterial CAIPIRINHA-Dixon-TWIST-Volume-Interpolated Breath-Hold Examination (MA-CDT-VIBE) Technique in Dynamic Contrast-Enhanced Magnetic Resonance Imaging

Background

The multi-arterial CAIPIRINHA-Dixon-TWIST-volume-interpolated breath-hold examination (MA-CDT-VIBE) sequence has the advantage of detecting hypervascular lesions during the arterial phase of magnetic resonance imaging (MRI) of the liver. Liver cirrhosis may be associated with dysplastic nodules. This study aimed to compare the use of routine liver MRI sequences with the MA-CDT-VIBE sequence to identify dysplastic liver nodules in patients with liver cirrhosis.

Material/Methods

Between February 2016 and March 2017, there were 21 patients with liver cirrhosis who had 33 dysplastic liver nodules, which were detected by comprehensive multisequence MRI as the reference standard for nodule imaging. Liver MRI using edge sharpness assessment by parametric (ESAP) modeling was compared with five dynamic arterial subphases that were included in the MA-CDT-VIBE sequence with a temporal resolution of 2.8 s and an acquisition time of 20 s during one breath-hold.

Results

In the 21 patients included in the study, the MA-CDT-VIBE technique (30/33 for the first reading and 33/33 for the second reading) showed an improved lesion detection rate compared with the ESAP technique (27/33 for the first reading and 29/33 for the second reading), and for 73% of the patients, MA-CDT-VIBE imaging showed improved arterial parenchyma contrast. There was a high degree of interobserver agreement between the two reads (κ: 0.68–0.91; P<0.001).

Conclusions

The MA-CDT-VIBE sequence of MRI liver imaging improved the detection of dysplastic nodules in cirrhosis of the liver compared with routine liver MRI sequences.

Advanced MR Imaging of the Pancreas

MR imaging can be optimized to evaluate a spectrum of pancreatic disorders with advanced sequences aimed to provide quantitative results and increase MR diagnostic capabilities. The pancreas remains a challenging organ to image because of its small size and location deep within the body. Besides its anatomic limitations, pancreatic pathology can be difficult to identify in the early stages. For example, subtle changes in ductal anatomy and parenchymal composition seen in early chronic pancreatitis are imperceptible with other modalities, such as computed tomography. This article reviews the application of MR imaging techniques and emerging MR sequences used in pancreas imaging.

Imaging of hepatocellular carcinoma and image guided therapies - how we do it

Treatment options for hepatocellular carcinoma have evolved over recent years. Interventional radiologists and surgeons can offer curative treatments for early stage tumours, and locoregional therapies can be provided resulting in longer survival times. Early diagnosis with screening ultrasound is the key. CT and MRI are used to characterize lesions and determine the extent of tumour burden. Imaging techniques are discussed in this article as the correct imaging protocols are essential to optimise successful detection and characterisation. After treatment it is important to establish regular imaging follow up with CT or MRI as local residual disease can be easily treated, and recurrence elsewhere in the liver is common.

Arterial Phase with CAIPIRINHA-Dixon-TWIST (CDT)-Volume-Interpolated Breath-Hold Examination (VIBE) in Detecting Hepatic Metastases

PURPOSE: To evaluate lesion enhancement performance of Multi-Arterial CAIPIRINHA-Dixon-TWIST–Volume-Interpolated Breath-Hold Examination (MA-CDT-VIBE) for the detection of hepatic metastases. MATERIALS AND METHODS: Thirty-one patients with suspicious hepatic metastases were enrolled in this retrospective study. Two independent radiologists scored visualization of each lesion on a scale of 1 (poor visualization) to 11 (excellent visualization) on 11 sets of images. These included 6 hepatic arterial sub-phases acquired in one breath-hold, 1 series of the mean of 6 hepatic arterial sub-phases, 3 subtracted arterial sub-phases, and 1 portal venous phase. The phases with good (score 8–10) and excellent (score 11) lesion visualization were identified, and the number of lesions seen on each of these phases was compared to the number of lesions that was seen best on the equivalent-to-conventional single arterial phase as well as to those that were see best on the mean of 6 hepatic arterial sub-phases. Inter-reader agreement was also calculated. RESULTS: The MA-CDT-VIBE was successfully acquired in 25 patients with hypervascular metastases (96 lesions) and 6 patients with hypovascular metastases (13 lesions). In case of hypervascular metastases, the 6th/6 arterial sub-phase had excellent lesion visualization (sore of 11) in 56 and 44 lesions for the 2 readers, respectively. Good lesion visualization (score of 8-10) was recorded in 5th/6 arterial subphases, in 81 and 67 lesions for the 2 readers, respectively. In case of hypovascular metastases, the portal venous phase had excellent lesion visualization (sore of 11) in all 13 lesions for the 2 readers. Good lesion visualization (score of 8–10) was recorded in 12 and 13 lesions on the 5th/6 and 6th/6 arterial subphases, respectively. More hypervascular lesions scored good (score of 8–10) and excellent (score of 11) on the 5th/6 and 6th/6 phases of MA-CDT-VIBE compared with the equivalent-to-conventional single arterial phase (3rd/6) and the set with mean of 6 hepatic arterial sub-phases. The results were statistically significant (t test, P < .0001). Inter-reader agreement was good for hypervascular lesions (kappa = 0.627, P < .0001) and excellent for hypovascular lesions (kappa = 1.0, P < .0001), respectively. CONCLUSIONS: The MA-CDT-VIBE improves lesion conspicuity by providing a wide observation window for hypervascular lesions. For hypovascular lesions, the advantage of multiple arterial sub-phases over the portal venous phase is not apparent.

Improved detection of hypervascular liver lesions with CAIPIRINHA-Dixon-TWIST-volume-interpolated breath-hold examination

OBJECTIVES

The aim of this study was to assess the diagnostic performance of a dynamic, multiphasic contrast-enhanced volume-interpolated sequence with advanced parallel imaging techniques, Dixon fat saturation, and view sharing with 5 hepatic arterial subphases for the detection of focal liver lesions.

MATERIALS AND METHODS

Twenty-four consecutive patients (13 females, 11 males; mean [SD] age, 58 [15] years) with focal liver lesions were included in this prospective study. The examination was performed at a 3-T magnetic resonance imaging system (MAGNETOM Skyra; Siemens Healthcare, Erlangen, Germany). Five dynamic arterial subphases with a temporal resolution of 2.6 seconds, starting 17 seconds after injection of the hepatobiliary contrast agent gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Eovist; Bayer HealthCare, Leverkusen, Germany), were acquired using an accelerated parallel imaging volume-interpolated sequence with view sharing (multiarterial controlled aliasing in parallel imaging results in higher acceleration-Dixon-time-resolved angiography with interleaved stochastic trajectories-volumetric interpolated breath-hold examination [MA-CDT-VIBE]). The fourth of the 5 arterial acquisition phases (ie, at 24.8 seconds after the start of contrast agent injection) was considered the equivalent of a standard hepatic arterial phase (equivalent standard arterial phase [ESAP]). The diagnostic value of all 5 dynamic arterial phases for the detection of focal liver lesions, as compared with the single ESAP, was judged in 2 independent consensus readings. The 2 consensus reading groups were blinded to each others' results. The complete, comprehensive multisequence magnetic resonance imaging examination, including T1-weighted, T2-weighted, and multiphasic contrast-enhanced sequences, served as the standard of reference for lesion detection.

RESULTS

Forty-six percent of the patients (11/24) had hypervascular lesions. In 79 % of all patients (19/24), the best arterial parenchymal contrast of one of the MA-CDT-VIBE acquisition phases was considered better than that of the ESAP. In one third of all cases (8/24 for the first and 6/24 for the second consensus reading), MA-CDT-VIBE showed an improved lesion detection rate compared with ESAP, especially in hypervascular lesions (4/11, representing 36% of all patients with hypervascular lesions). There was a high degree of interrater agreement between the 2 consensus reading groups (the Cohen κ, 0.71-1.00; P < 0.001).

CONCLUSIONS

Compared with a standard hepatic arterial phase, MA-CDT-VIBE with 5 hepatic arterial subphases demonstrated greater diagnostic accuracy for the detection of hypervascular focal liver lesions and provided a robust and optimized hepatic arterial acquisition phase.

MRI of diffuse liver disease: characteristics of acute and chronic diseases

Diffuse liver disease, including chronic liver disease, affects tens of millions of people worldwide, and there is a growing need for diagnostic evaluation as treatments become more readily available, particularly for viral liver diseases. Magnetic resonance imaging (MRI) provides unique capabilities for noninvasive characterization of the liver tissue that rival or surpass the diagnostic utility of liver biopsies. There has been incremental improvement in the use of standardized MRI sequences, acquired before and after administration of a contrast agent, for the evaluation of diffuse liver disease and the study of the liver parenchyma and blood supply. More recent developments have led to methods for quantifying important liver metabolites, including lipids and iron, and liver fibrosis, the hallmark of chronic liver disease. Here, we review the MRI techniques and diagnostic features associated with acute and chronic liver disease.

MRI of hepatocellular carcinoma: an update of current practices

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and liver transplantation is the optimal treatment for selected patients with HCC and chronic liver disease (CLD). Accurate selection of patients for transplantation is essential to maximize patient outcomes and ensure optimized allocation of donor organs. Magnetic resonance imaging (MRI) is a powerful tool for the detection, characterization, and staging of HCC. In patients with CLD, the MRI findings of an arterial-enhancing mass with subsequent washout and enhancing capsule on delayed interstitial phase images are diagnostic for HCC. Major organizations with oversight for organ donor distribution, such as The Organ Procurement and Transplantation Network (OPTN), accept an imaging diagnosis of HCC, no longer requiring tissue biopsy. In patients that are awaiting transplantation, or are not candidates for liver transplantation, localized therapies such as transarterial chemoembolization and radiofrequency ablation may be offered. MRI can be used to monitor treatment response. The purpose of this review article is to describe the role of imaging methods in the diagnosis, staging, and follow-up of HCC, with particular emphasis on established and evolving MRI techniques employing nonspecific gadolinium chelates, hepatobiliary contrast agents, and diffusion weighted imaging. We also briefly review the recently developed Liver Imaging Reporting and Data System (LI-RADS) formulating a standardized terminology and reporting structure for evaluation of lesions detected in patients with CLD.

Enhancement of the liver and pancreas in the hepatic arterial dominant phase: comparison of hepatocyte-specific MRI contrast agents, gadoxetic acid and gadobenate dimeglumine, on 3 and 1.5 Tesla MRI in the same patient

PURPOSE

To evaluate the relative enhancement of liver, pancreas, focal nodular hyperplasia (FNH), pancreas-to-liver index, and FNH-to-liver index in the hepatic arterial dominant phase (HADP) after injection of hepatocyte-specific MRI contrast agents, gadoxetic acid and gadobenate dimeglumine, on 3 and 1.5 Tesla (T) MRI in the same patient.

MATERIALS AND METHODS

The MRI database was retrospectively searched to identify consecutive patients who underwent abdominal MRI at 3T and 1.5T systems, using both 0.025 mmol/kg gadoxetic acid-enhanced and 0.05 mmol/kg gadobenate dimeglumine-enhanced MRI at the same magnetic strength field system. 22 patients were identified, 10 were scanned at 3T system and 12 at 1.5T system. The enhancement of liver, pancreas, and FNH was evaluated quantitatively on MR images.

RESULTS

The relative enhancement of liver in HADP in the gadobenate dimeglumine-enhanced group in all subjects was significantly higher than that in gadoxetic acid-enhanced group (P = 0.023). The gadobenate dimeglumine-enhanced group in HADP had better relative enhancement of pancreas and FNH, pancreas-to-liver index, and FNH-to-liver index than gadoxetic acid-enhanced group, but the difference was not statistically significant.

CONCLUSION

The 0.05 mmol/kg gadobenate dimeglumine-enhanced abdominal MRI studies at 3T and 1.5T MR systems are superior in relative enhancement of the liver in HADP to 0.025 mmol/kg gadoxetic acid-enhanced MRI. This type of assessment may provide comparative effectiveness data.

MR imaging techniques for pancreas

Pancreatic magnetic resonance (MR) imaging has become a useful tool in evaluating pancreatic disorders. Technical innovations in MR imaging have evolved over the last decade, with most sequences being performed in one or a few breath-holds. Three-dimensional sequences with thin, contiguous slices allow for improved spatial resolution on the postgadolinium images and MR cholangiopancreatography (MRCP). The diagnostic potential of MRCP is equivalent to endoscopic retrograde pancreatography, particularly when intravenous secretin is used to enhance the pancreatic duct assessment. This article highlights the advantages and disadvantages of state-of-the-art and emerging pulse sequences and their application to imaging pancreatic diseases.

Magnetic resonance imaging of the liver: sequence optimization and artifacts

The liver is one of the most challenging organs of the body to image with magnetic resonance because it is large and mobile, receives a dual blood supply, and is surrounded by organs and structures that contribute to artifacts from flow and susceptibility. Recent advances in imaging hardware, in addition to improvements in temporal resolution and development of hepatocyte-specific contrast agents, make imaging of the liver more approachable than in the past; however, it remains a complex process that requires compromise. In this article the authors discuss development and optimization of a liver imaging protocol at 1.5 T, with common variations in each element of the protocol, as well as the strengths and weaknesses associated with the relevant sequences.

Magnetic resonance imaging: Review of imaging techniques and overview of liver imaging

Magnetic resonance imaging (MRI) of the liver is slowly transitioning from a problem solving imaging modality to a first line imaging modality for many diseases of the liver. The well established advantages of MRI over other cross sectional imaging modalities may be the basis for this transition. Technological advancements in MRI that focus on producing high quality images and fast imaging, increasing diagnostic accuracy and developing newer function-specific contrast agents are essential in ensuring that MRI succeeds as a first line imaging modality. Newer imaging techniques, such as parallel imaging, are widely utilized to shorten scanning time. Diffusion weighted echo planar imaging, an adaptation from neuroimaging, is fast becoming a routine part of the MRI liver protocol to improve lesion detection and characterization of focal liver lesions. Contrast enhanced dynamic T1 weighted imaging is crucial in complete evaluation of diseases and the merit of this dynamic imaging relies heavily on the appropriate timing of the contrast injection. Newer techniques that include fluoro-triggered contrast enhanced MRI, an adaptation from 3D MRA imaging, are utilized to achieve good bolus timing that will allow for optimum scanning. For accurate interpretation of liver diseases, good understanding of the newer imaging techniques and familiarity with typical imaging features of liver diseases are essential. In this review, MR sequences for a time efficient liver MRI protocol utilizing newer imaging techniques are discussed and an overview of imaging features of selected common focal and diffuse liver diseases are presented.

State-of-the-art pancreatic MRI

OBJECTIVE

The purpose of this article is to discuss the most current techniques used for pancreatic imaging, highlighting the advantages and disadvantages of state-of-the-art and emerging pulse sequences and their application to pancreatic disease.

CONCLUSION

Given the technologic advances of the past decade, pancreatic MRI protocols have evolved. Most sequences can now be performed in one or a few breath-holds; 3D sequences with thin, contiguous slices offer improved spatial resolution; and better fat and motion suppression allow improved contrast resolution and image quality. The diagnostic potential of MRCP is now almost as good as ERCP, with pancreatic MRI as the main imaging technique to investigate biliopancreatic pain, chronic pancreatitis, and cystic pancreatic tumors at many institutions. In addition, functional information is provided with secretin-enhanced MRCP.