Improving Vessel Segmentation with Multi-Task Learning and Auxiliary Data Available Only During Model Training.

Liver vessel segmentation in magnetic resonance imaging data is important for the computational analysis of vascular remodeling, associated with a wide spectrum of diffuse liver diseases. Existing approaches rely on contrast enhanced imaging data, but the necessary dedicated imaging sequences are not uniformly acquired. Images without contrast enhancement are acquired more frequently, but vessel segmentation is challenging, and requires large-scale annotated data. We propose a multi-task learning framework to segment vessels in liver MRI without contrast. It exploits auxiliary contrast enhanced MRI data available only during training to reduce the need for annotated training examples. Our approach draws on paired native and contrast enhanced data with and without vessel annotations for model training. Results show that auxiliary data improves the accuracy of vessel segmentation, even if they are not available during inference. The advantage is most pronounced if only few annotations are available for training, since the feature representation benefits from the shared task structure. A validation of this approach to augment a model for brain tumor segmentation confirms its benefits across different domains. An auxiliary informative imaging modality can augment expert annotations even if it is only available during training.

Are dilution, slow injection and care bolus technique the causal solution to mitigating arterial-phase artifacts on gadoxetic acid-enhanced MRI? A large-cohort study.

OBJECTIVE: Arterial-phase artifacts are gadoxetic acid (GA)-enhanced MRI's major drawback, ranging from 5 to 39%. We evaluate the effect of dilution and slow injection of GA using automated fluoroscopic triggering on liver MRI arterial-phase (AP) acquisition timing, artifact frequency, and lesion visibility. METHODS AND MATERIALS: Saline-diluted 1:1 GA was injected at 1 ml/s into 1413 patients for 3 T liver MRI. Initially, one senior abdominal radiologist, i.e., principal investigator (PI), assessed all MR exams and compared them to previous and follow-up images, as well as the radiology report on record, determining the standard of reference for lesion detection and characterization. Then, three other readers independently evaluated the AP images for artifact type (truncation (TA), transient severe motion (TSM) or mixed), artifact severity (on a 5-point scale), acquisition timing (on a 4-point scale) and visibility (on a 5-point scale) of hypervascular lesions ≥ 5 mm, selected by the PI. Artifact score ≥ 4 and artifact score ≤ 3 were considered significant and non-significant artifacts, respectively. RESULTS: Of the 1413 exams, diagnostic-quality arterial-phase images included 1100 (77.8%) without artifacts, 220 (15.6%) with minimal, and 77 (5.4%) with moderate artifacts. Only 16 exams (1.1%) had significant artifacts, 13 (0.9%) with severe artifacts (score 4), and three (0.2%) non-diagnostic artifacts (score 5). AP acquisition timing was optimal in 1369 (96.8%) exams. Of the 449 AP hypervascular lesions, 432 (96.2%) were detected. CONCLUSION: Combined dilution and slow injection of GA with MR results in well-timed arterial-phase images in 96.8% and a reduction of exams with significant artifacts to 1.1%. CLINICAL RELEVANCE STATEMENT: Hypervascular lesions, in particular HCC detection, hinge on arterial-phase hyperenhancement, making well-timed, artifact-free arterial-phase images a prerequisite for accurate diagnosis. Saline dilution 1:1, slow injection (1 ml/s), and automated bolus triggering reduce artifacts and optimize acquisition timing. KEY POINTS: • There was substantial agreement among the three readers regarding the presence and type of arterial-phase (AP) artifacts, acquisition timing, and lesion visibility. • Impaired AP hypervascular lesion visibility occurred in 17 (3.8%) cases; in eight lesions due to mistiming and in nine lesions due to significant artifacts. • When AP timing was suboptimal, it was too late in 40 exams (3%) and too early in 4 exams (0.2%) of exams.

Consensus report from the 10th Global Forum for Liver Magnetic Resonance Imaging: developments in HCC management.

The 10th Global Forum for Liver Magnetic Resonance Imaging (MRI) was held as a virtual 2-day meeting in October 2021, attended by delegates from North and South America, Asia, Australia, and Europe. Most delegates were radiologists with experience in liver MRI, with representation also from specialists in liver surgery, oncology, and hepatology. Presentations, discussions, and working groups at the Forum focused on the following themes: • Gadoxetic acid in clinical practice: Eastern and Western perspectives on current uses and challenges in hepatocellular carcinoma (HCC) screening/surveillance, diagnosis, and management • Economics and outcomes of HCC imaging • Radiomics, artificial intelligence (AI) and deep learning (DL) applications of MRI in HCC. These themes are the subject of the current manuscript. A second manuscript discusses multidisciplinary tumor board perspectives: how to approach early-, mid-, and late-stage HCC management from the perspectives of a liver surgeon, interventional radiologist, and oncologist (Taouli et al, 2023). Delegates voted on consensus statements that were developed by working groups on these meeting themes. A consensus was considered to be reached if at least 80% of the voting delegates agreed on the statements. CLINICAL RELEVANCE STATEMENT: This review highlights the clinical applications of gadoxetic acid-enhanced MRI for liver cancer screening and diagnosis, as well as its cost-effectiveness and the applications of radiomics and AI in patients with liver cancer. KEY POINTS: • Interpretation of gadoxetic acid-enhanced MRI differs slightly between Eastern and Western guidelines, reflecting different regional requirements for sensitivity vs specificity. • Emerging data are encouraging for the cost-effectiveness of gadoxetic acid-enhanced MRI in HCC screening and diagnosis, but more studies are required. • Radiomics and artificial intelligence are likely, in the future, to contribute to the detection, staging, assessment of treatment response and prediction of prognosis of HCC-reducing the burden on radiologists and other specialists and supporting timely and targeted treatment for patients.

Consensus report from the 10th global forum for liver magnetic resonance imaging: multidisciplinary team discussion.

The 10th Global Forum for Liver Magnetic Resonance Imaging was held in October 2021. The themes of the presentations and discussions at this Forum are described in detail in the review by Taouli et al (2023). The focus of this second manuscript developed from the Forum is on multidisciplinary tumor board perspectives in hepatocellular carcinoma (HCC) management: how to approach early-, mid-, and late-stage management from the perspectives of a liver surgeon, an interventional radiologist, and an oncologist. The manuscript also includes a panel discussion by multidisciplinary experts on three selected cases that explore challenging aspects of HCC management. CLINICAL RELEVANCE STATEMENT: This review highlights the importance of a multidisciplinary team approach in liver cancer patients and includes the perspectives of a liver surgeon, an interventional radiologist, and an oncologist, including illustrative case studies. KEY POINTS: • A liver surgeon, interventional radiologist, and oncologist presented their perspectives on the treatment of early-, mid-, and late-stage HCC. • Different perspectives on HCC management between specialties emphasize the importance of multidisciplinary tumor boards. • A multidisciplinary faculty discussed challenging aspects of HCC management, as highlighted by three case studies.

Influence of dilution on arterial-phase artifacts and signal intensity on gadoxetic acid-enhanced liver MRI.

OBJECTIVES: To investigate the effect of saline-diluted gadoxetic acid, done for arterial-phase (AP) artifact reduction, on signal intensity (SI), and hence focal lesion conspicuity on MR imaging. METHODS: We retrospectively examined 112 patients who each had at least two serial gadoxetic acid-enhanced liver MRIs performed at 1 ml/s, first with non-diluted (ND), then with 1:1 saline-diluted (D) contrast. Two blinded readers independently analyzed the artifacts and graded dynamic images using a 5-point scale. The absolute SI of liver parenchyma, focal liver lesions (if present), aorta, and portal vein at the level of the celiac trunk and the SI of the paraspinal muscle were measured in all phases. The signal-to-norm (SINorm) of the vascular structures, hepatic parenchyma and focal lesions, and the contrast-to-norm (CNorm) of focal liver lesions were calculated. RESULTS: AP artifacts were significantly reduced with dilution. Mean absolute contrast-enhanced liver SI was significantly higher on the D exams compared to the ND exams. Likewise, SINorm of liver parenchyma was significantly higher in all contrast-enhanced phases except transitional phase on the D exams. SINorm values in the AP for the aorta and in the PVP for portal vein were significantly higher on the diluted exams. The CNorm was not significantly different between ND and D exams for lesions in any imaging phase. The interclass correlation coefficient was excellent (0.89). CONCLUSION: Gadoxetic acid dilution injected at 1ml/s produces images with significantly fewer AP artifacts but no significant loss in SINorm or CNorm compared to standard non-diluted images. KEY POINTS: • Diluted gadoxetic acid at slow injection (1 ml/s) yielded images with higher SINorm of the liver parenchyma and preserved CNorm for focal liver lesions. • Gadoxetic acid-enhanced MRI injected at 1 ml/s is associated with arterial-phase (AP) artifacts in 31% of exams, which may degrade image quality and limits focal liver lesion detection. • Saline dilution of gadoxetic acid 1:1 combined with a slow injection rate of 1 ml/s significantly reduced AP artifacts from 31 to 9% and non-diagnostic AP artifacts from 16 to 1%.

Imaging features facilitate diagnosis of porto-sinusoidal vascular disorder.

OBJECTIVES: Porto-sinusoidal vascular disorder (PSVD) is a recently defined vascular liver disease. Since diagnosis remains challenging, we aimed to evaluate radiological features that are distinct between PSVD and cirrhosis. METHODS: Clinical, laboratory, and radiological parameters (CT/MRI) of patients with histologically-confirmed PSVD vs. cirrhosis vs. non-cirrhotic parenchymal liver disease were retrospectively evaluated. RESULTS: Sixty-three PSVD, 155 cirrhosis, and 41 non-cirrhotic patients were included. As compared to cirrhosis, PSVD patients were younger and had lower HVPG, liver stiffness, and MELD. Routine clinical and imaging findings indicative of portal hypertension were similarly common. Intrahepatic portal tract abnormalities (49% vs. 15%; p < 0.001), FNH-like lesions (30% vs. 1%; p < 0.001), and abnormal liver morphology defined as peripheral parenchymal atrophy and compensatory hypertrophy of central segments (32% vs. 7%; p < 0.001) were significantly more common in PSVD patients. Hypertrophy of segment I (70% vs. 84%; p = 0.019), atrophy of segment IV (24% vs. 47%; p = 0.001), and nodular liver surface (22% vs. 89%; p < 0.001) were more common in patients with cirrhosis. In patients with gadoxetic acid-enhanced MRI, we identified the distinct imaging feature of "periportal hyperintensity" in the hepatobiliary phase (HBP) in 42% of patients with PSVD (14/33) vs. 1% in cirrhosis (1/95) vs. 0% in non-cirrhotic controls (0/41); p < 0.001). CONCLUSIONS: Diagnosis of PSVD must be considered in younger patients presenting with clinical features of portal hypertension, portal tract abnormalities, and FNH-like lesions on CT/MRI. 'Periportal hyperintensity' in the HBP of gadoxetic acid-enhanced MRI was identified as a specific radiological feature of PSVD. KEY POINTS: • Cross-sectional imaging can provide essential information to identify patients with porto-sinusoidal vascular disorder (PSVD). • Intrahepatic portal tract abnormalities, FNH-like lesions, and abnormal liver morphology are common in PSVD patients. • Periportal hyperintensity on the hepatobiliary phase of gadoxetic acid-enhanced MRI seems to be specific for patients with PSVD.

Added value of quantitative, multiparametric 18F-FDG PET/MRI in the locoregional staging of rectal cancer.

PURPOSE: The purpose of this study was to determine whether multiparametric positron emission tomography/magnetic resonance imaging (mpPET/MRI) can improve locoregional staging of rectal cancer (RC) and to assess its prognostic value after resection. METHODS: In this retrospective study, 46 patients with primary RC, who underwent multiparametric 18F-fluorodeoxyglucose (FDG) PET/MRI, followed by surgical resection without chemoradiotherapy, were included. Two readers reviewed T- and N- stage, mesorectal involvement, sphincter infiltration, tumor length, and distance from anal verge. In addition, diffusion-weighted imaging (DWI) and PET parameters were extracted from the multiparametric protocol and were compared to radiological staging as well as to the histopathological reference standard. Clinical and imaging follow-up was systematically assessed for tumor recurrence and death. RESULTS: Locally advanced rectal cancers (LARC) exhibited significantly higher metabolic tumor volume (MTV, AUC 0.74 [95% CI 0.59-0.89], p = 0.004) and total lesion glycolysis (TLG, AUC 0.70 [95% CI 0.53-0.87], p = 0.022) compared to early tumors. T-stage was associated with MTV (AUC 0.70 [95% CI 0.54-0.85], p = 0.021), while N-stage was better assessed using anatomical MRI sequences (AUC 0.72 [95% CI 0.539-0.894], p = 0.032). In the multivariate regression analysis, depending on the model, both anatomical MRI sequences and MTV/TLG were capable of detecting LARC. Combining anatomical MRI stage and MTV/TLG led to a superior diagnostic performance for detecting LARC (AUC 0.81, [95% CI 0.68-0.94], p < 0.001). In the survival analysis, MTV was independently associated with overall survival (HR 1.05 [95% CI 1.01-1.10], p = 0.044). CONCLUSION: Multiparametric PET-MRI can improve identification of locally advanced tumors and, hence, help in treatment stratification. It provides additional information on RC tumor biology and may have prognostic value.

Imaging Features of Premalignant Biliary Lesions and Predisposing Conditions with Pathologic Correlation.

Biliary malignancies include those arising from the intrahepatic and extrahepatic bile ducts as well as the gallbladder and hepatopancreatic ampulla of Vater. The majority of intrahepatic and extrahepatic malignancies are cholangiocarcinomas (CCAs). They arise owing to a complex interplay between the patient-specific genetic background and multiple risk factors and may occur in the liver (intrahepatic CCA), hilum (perihilar CCA), or extrahepatic bile ducts (distal CCA). Biliary-type adenocarcinoma constitutes the most common histologic type of ampullary and gallbladder malignancies. Its prognosis is poor and surgical resection is considered curative, so early detection is key, with multimodality imaging playing a central role in making the diagnosis. There are several risk factors for biliary malignancy as well as predisposing conditions that increase the risk; this review highlights the pertinent imaging features of these entities with histopathologic correlation. The predisposing factors are broken down into three major categories: (a) congenital malformations such as choledochal cyst and pancreaticobiliary maljunction; (b) infectious or inflammatory conditions such as parasitic infections, hepatolithiasis, primary sclerosing cholangitis, and porcelain gallbladder; and (c) preinvasive epithelial neoplasms such as biliary intraepithelial neoplasm, intraductal papillary neoplasm of the bile duct, intra-ampullary papillary tubular neoplasm, and intracholecystic papillary neoplasm of the gallbladder. Recognizing the baseline features of these premalignant biliary entities and changes in their appearance over time that indicate the advent of malignancy in high-risk patients can lead to early diagnosis and potentially curative management. An invited commentary by Volpacchio is available online. Online supplemental material is available for this article. ©RSNA, 2022.

Risk Scores for Metabolic Dysfunction-Associated Fatty Liver Disease in Pediatric Obesity.

INTRODUCTION: Early noninvasive detection of incipient liver damage is crucial to prevent long-term adverse health outcomes. A variety of scores to assess liver status have been proposed, mostly for adult populations. Validation of noninvasive hepatic scores to identify children at risk of metabolic dysfunction-associated fatty liver disease (MAFLD) is a gap in research, particularly in youth with severe obesity considering pubertal stage and sex. METHODS: In a well-characterized pediatric population aged 9-19 years (n = 115), 19 published liver scores were analyzed. The area under the receiver operating characteristic curve (AUROC) for determination of MAFLD as assessed by magnetic resonance imaging was calculated. RESULTS: The pediatric indices PNFI, B-AST, and M-APRI and several scores developed in adults significantly differed in children with MAFLD compared to children without, while some established indices did not. Only nonalcoholic fatty liver disease liver fat score (NAFLD-LFS) and the model by Cao et al. [PLoS One. 2013;8(12):e82092] showed acceptable predictive accuracy (AUROC >0.8) independently of pubertal stage and sex. When stratifying for pubertal stage and sex, the GSG-Index was superior in pubertal girls, and NAFLD-LFS performed best in pubertal boys. CONCLUSION: NAFLD-LFS and the model by Cao et al. [PLoS One. 2013;8(12):e82092] were well suited to predict MAFLD in youth with severe obesity. In pubertal children, GSG-Index and NAFLD-LFS performed best in girls and boys, respectively.

Gadoxetic acid-enhanced MRI-derived functional liver imaging score (FLIS) and spleen diameter predict outcomes in ACLD.

BACKGROUND & AIMS: Functional liver imaging score (FLIS) - derived from gadoxetic acid-enhanced MRI - correlates with liver function and independently predicts liver-related mortality in patients with chronic liver disease (CLD), while splenic craniocaudal diameter (SCCD) is a marker of portal hypertension. The aim of this study was to investigate the accuracy of a combination of FLIS and SCCD for predicting hepatic decompensation, acute-on-chronic liver failure (ACLF), and mortality in patients with advanced CLD (ACLD). METHODS: We included 397 patients with CLD who underwent gadoxetic acid-enhanced liver MRI. The FLIS was calculated by summing the points (0-2) of 3 hepatobiliary-phase features: hepatic enhancement, biliary excretion, and portal vein signal intensity. Patients were stratified into 3 groups according to liver fibrosis severity and presence/history of hepatic decompensation: non-ACLD, compensated ACLD (cACLD), and decompensated ACLD (dACLD). RESULTS: SCCD showed excellent intra- and inter-reader agreement. Importantly, SCCD was an independent risk factor for hepatic decompensation in patients with cACLD (per cm; adjusted hazard ratio [aHR] 1.13; 95% CI 1.04-1.23; p = 0.004). Patients with cACLD and a FLIS of 0-3 points and/or a SCCD of >13 cm were at increased risk of hepatic decompensation (aHR 3.07; 95% CI 1.43-6.59; p = 0.004). In patients with dACLD, a FLIS of 0-3 was independently associated with an increased risk of ACLF (aHR 2.81; 95% CI 1.16-6.84; p = 0.02), even after adjusting for other prognostic factors. Finally, a FLIS and SCCD-based algorithm was independently predictive of transplant-free mortality and stratified the probability of transplant-free survival (TFS) in ACLD (p <0.001): FLIS 4-6 and SCCD ≤13 cm (5-year TFS of 84%) vs. FLIS 4-6 and SCCD >13 cm (5-year TFS of 70%) vs. FLIS 0-3 (5-year TFS of 24%). CONCLUSION: The FLIS and SCCD are simple imaging markers that provide complementary information for risk stratification in patients with compensated and decompensated ACLD. LAY SUMMARY: Magnetic resonance imaging (MRI) can be used to assess the state of the liver. Previously the functional liver imaging score, which is based on MRI criteria, was developed as a measure of liver function and to predict the risk of liver-related complications or death. By combining this score with a measurement of spleen diameter, also using MRI, we generated an algorithm that could predict the risk of adverse liver-related outcomes in patients with advanced chronic liver disease.

Reporting standards for primary sclerosing cholangitis using MRI and MR cholangiopancreatography: guidelines from MR Working Group of the International Primary Sclerosing Cholangitis Study Group.

Primary sclerosing cholangitis (PSC) is a chronic inflammatory disorder affecting the bile ducts and is characterized by biliary strictures, progressive liver parenchymal fibrosis, and an increased risk of hepatobiliary malignancies primarily cholangiocarcinoma (CCA). PSC may lead to portal hypertension, liver decompensation, and liver failure with the need for liver transplantation. Magnetic resonance imaging (MRI)/magnetic resonance cholangiopancreatography (MRCP) are considered the imaging standard for diagnosis and follow-up in patients with PSC. Currently, there are no universally accepted reporting standards and definitions for MRI/MRCP features. Controversies exist about the definition of a high-grade stricture and there is no widely agreed approach to their management. The members of the MRI working group of the International Primary Sclerosing Cholangitis Study Group (IPSCSG) sought to define terminologies and reporting standards for describing MRI/MRCP features that would be applied to diagnosis and surveillance of disease progression, and potentially for evaluating treatment response in clinical trials. In this extensive review, the technique of MRI/MRCP and assessment of image quality for the evaluation of PSC is briefly described. The definitions and terminologies for severity and length of strictures, duct wall thickening and hyperenhancement, and liver parenchyma signal intensity changes are outlined. As CCA is an important complication of PSC, standardized reporting criteria for CCA developing in PSC are summarized. Finally, the guidelines for reporting important changes in follow-up MRI/MRCP studies are provided. KEY POINTS: • Primary sclerosing cholangitis is a chronic inflammatory disorder affecting the bile ducts, causing biliary strictures and liver fibrosis and an increased risk of cholangiocarcinoma. • This consensus document provides definitions and suggested reporting standards for MRI and MRCP features of primary sclerosing cholangitis, which will allow for a standardized approach to diagnosis, assessment of disease severity, follow-up, and detection of complications. • Standardized definitions and reporting of MRI/MRCP features of PSC will facilitate comparison between studies, promote longitudinal assessment during management, reduce inter-reader variability, and enhance the quality of care and communication between health care providers.

Modern imaging of cholangitis.

Cholangitis refers to inflammation of the bile ducts with or without accompanying infection. When intermittent or persistent inflammation lasts 6 months or more, the condition is classified as chronic cholangitis. Otherwise, it is considered an acute cholangitis. Cholangitis can also be classified according to the inciting agent, e.g. complete mechanical obstruction, which is the leading cause of acute cholangitis, longstanding partial mechanical blockage, or immune-mediated bile duct damage that results in chronic cholangitis.The work-up for cholangitis is based upon medical history, clinical presentation, and initial laboratory tests. Whereas ultrasound is the first-line imaging modality used to identify bile duct dilatation in patients with colicky abdominal pain, cross-sectional imaging is preferable when symptoms cannot be primarily localised to the hepatobiliary system. CT is very useful in oncologic, trauma, or postoperative patients. Otherwise, magnetic resonance cholangiopancreatography is the method of choice to diagnose acute and chronic biliary disorders, providing an excellent anatomic overview and, if gadoxetic acid is injected, simultaneously delivering morphological and functional information about the hepatobiliary system. If brush cytology, biopsy, assessment of the prepapillary common bile duct, stricture dilatation, or stenting is necessary, then endoscopic ultrasound and/or retrograde cholangiography are performed. Finally, when the pathologic duct is inaccessible from the duodenum or stomach, percutaneous transhepatic cholangiography is an option. The pace of the work-up depends upon the severity of cholestasis on presentation. Whereas sepsis, hypotension, and/or Charcot's triad warrant immediate investigation and management, chronic cholestasis can be electively evaluated.This overview article will cover the common cholangitides, emphasising our clinical experience with the chronic cholestatic liver diseases.

Imaging of inflammatory disease of the pancreas.

Increasingly acute and chronic pancreatitis (AP and CP) are considered a continuum of a single entity. Nonetheless, if, after flare-up, the pancreas shows no residual inflammation, it is classified as AP. CP is characterised by a long cycle of worsening and waning glandular inflammation without the pancreas ever returning to its baseline structure or function. According to the International Consensus Guidelines on Early Chronic Pancreatitis, pancreatic inflammation must last at least 6 months before it can be labelled CP. The distinction is important because, unlike AP, CP can destroy endocrine and exocrine pancreatic function, emphasising the importance of early diagnosis. As typical AP can be diagnosed by clinical symptoms plus laboratory tests, imaging is usually reserved for those with recurrent, complicated or CP. Imaging typically starts with ultrasound and more frequently with contrast-enhanced computed tomography (CECT). MRI and/or MR cholangiopancreatography can be used as a problem-solving tool to confirm indirect signs of pancreatic mass, differentiate between solid and cystic lesions, and to exclude pancreatic duct anomalies, as may occur with recurrent AP, or to visualise early signs of CP. MR cholangiopancreatography has replaced diagnostic endoscopic retrograde cholangiopancreatography (ERCP). However, ERCP, and/or endoscopic ultrasound (EUS) remain necessary for transpapillary biliary or pancreatic duct stenting and transgastric cystic fluid drainage or pancreatic tissue sampling, respectively. Finally, positron emission tomography-MRI or positron emission tomography-CT are usually reserved for complicated cases and/or to search for extra pancreatic systemic manifestations. In this article, we discuss a broad spectrum of inflammatory pancreatic disorders and the utility of various modalities in diagnosing acute and chronic pancreatitis.

[Chronic pancreatitis : Characterization and differentiation from pancreatic cancer]. / Chronische Pankreatitis : Charakterisierung und Differenzierung zum Pankreaskarzinom.

CLINICAL/METHODOLOGICAL ISSUE: Chronic pancreatitis (CP) is a long-lasting inflammation of the pancreas that changes the normal structure and function of the organ. There are a wide range of inflammatory pancreatic diseases, of which some entities, such as focal pancreatitis (FP) or "mass-forming pancreatitis," can mimic pancreatic ductal adenocarcinoma (PDAC). As a consequence, a misdiagnosis can lead to avoidable and unnecessary surgery or delay of therapy. STANDARD RADIOLOGICAL METHODS: The initial imaging method used in pancreatic diseases is ultrasound due to its availability and low cost, followed by contrast-enhanced computed tomography (CE-CT), which is considered a workhorse in the diagnostic work-up of diseases of the pancreas. Magnetic resonance imaging (MRI) and/or MR cholangiopancreatography (MRCP) can be used as a problem-solving tool to distinguish between solid and cystic lesions, and to rule out abnormalities in the pancreatic ducts, such as those associated with recurrent acute pancreatitis (AP) or to show early signs of CP. MRCP has essentially replaced diagnostic endoscopic retrograde cholangiopancreatography (ERCP) in the initial assessment before any therapeutic intervention. PRACTICAL RECOMMENDATION: The following review article summarizes the relevant features of CT and MRI that can help to make the diagnosis of CP and to aid in the differentiation between focal pancreatitis and PDAC, even in difficult cases.

Consensus report from the 9th International Forum for Liver Magnetic Resonance Imaging: applications of gadoxetic acid-enhanced imaging.

OBJECTIVES: The 9th International Forum for Liver Magnetic Resonance Imaging (MRI) was held in Singapore in September 2019, bringing together radiologists and allied specialists to discuss the latest developments in and formulate consensus statements for liver MRI, including the applications of gadoxetic acid-enhanced imaging. METHODS: As at previous Liver Forums, the meeting was held over 2 days. Presentations by the faculty on days 1 and 2 and breakout group discussions on day 1 were followed by delegate voting on consensus statements presented on day 2. Presentations and discussions centered on two main meeting themes relating to the use of gadoxetic acid-enhanced MRI in primary liver cancer and metastatic liver disease. RESULTS AND CONCLUSIONS: Gadoxetic acid-enhanced MRI offers the ability to monitor response to systemic therapy and to assist in pre-surgical/pre-interventional planning in liver metastases. In hepatocellular carcinoma, gadoxetic acid-enhanced MRI provides precise staging information for accurate treatment decision-making and follow-up post therapy. Gadoxetic acid-enhanced MRI also has potential, currently investigational, indications for the functional assessment of the liver and the biliary system. Additional voting sessions at the Liver Forum debated the role of multidisciplinary care in the management of patients with liver disease, evidence to support the use of abbreviated imaging protocols, and the importance of standardizing nomenclature in international guidelines in order to increase the sharing of scientific data and improve the communication between centers. KEY POINTS: • Gadoxetic acid-enhanced MRI is the preferred imaging method for pre-surgical or pre-interventional planning for liver metastases after systemic therapy. • Gadoxetic acid-enhanced MRI provides accurate staging of HCC before and after treatment with locoregional/biologic therapies. • Abbreviated protocols for gadoxetic acid-enhanced MRI offer potential time and cost savings, but more evidence is necessary. The use of gadoxetic acid-enhanced MRI for the assessment of liver and biliary function is under active investigation.

Spectrum of liver lesions hyperintense on hepatobiliary phase: an approach by clinical setting.

Hepatobiliary MRI contrast agents are increasingly being used for liver imaging. In clinical practice, most focal liver lesions do not uptake hepatobiliary contrast agents. Less commonly, hepatic lesions may show variable signal characteristics on hepatobiliary phase. This pictorial essay reviews a broad spectrum of benign and malignant focal hepatic observations that may show hyperintensity on hepatobiliary phase in various clinical settings. In non-cirrhotic patients, focal hepatic observations that show hyperintensity in the hepatobiliary phase are usually benign and typically include focal nodular hyperplasia. In patients with primary or secondary vascular disorders, focal nodular hyperplasia-like lesions arise as a local hyperplastic response to vascular alterations and tend to be iso- or hyperintense in the hepatobiliary phase. In oncologic patients, metastases and cholangiocarcinoma are hypointense lesions in the hepatobiliary phase; however, occasionally they may show a diffuse, central and inhomogeneous hepatobiliary paradoxical uptake with peripheral rim hypointensity. Post-chemotherapy focal nodular hyperplasia-like lesions may be tricky, and their typical hyperintense rim in the hepatobiliary phase is very helpful for the differential diagnosis with metastases. In cirrhotic patients, hepatocellular carcinoma may occasionally appear hyperintense on hepatobiliary phase.

A branched-chain amino acid-based metabolic score can predict liver fat in children and adolescents with severe obesity.

BACKGROUND: Eighty percent of adolescents with severe obesity suffer from non-alcoholic fatty liver disease (NAFLD). Non-invasive prediction models have been tested in adults, however, they performed poorly in paediatric populations. OBJECTIVE: This study aimed to investigate novel biomarkers for NAFLD and to develop a score that predicts liver fat in youth with severe obesity. METHODS: From a population with a BMI >97th percentile aged 9-19 years (n = 68), clinically thoroughly characterized including MRI-derived proton density fat fraction (MRI-PDFF), amino acids and acylcarnitines were measured by HPLC-MS. RESULTS: In children with NAFLD, higher levels of plasma branched-chain amino acids (BCAA) were determined. BCAAs correlated with MRI-PDFF (R = 0.46, p < .01). We identified a linear regression model adjusted for age, sex and pubertal stage consisting of BCAAs, ALT, GGT, ferritin and insulin that predicted MRI-PDFF (R = 0.75, p < .01). ROC analysis of this model revealed AUCs of 0.85, 0.85 and 0.92 for the detection of any, moderate and severe steatosis, respectively, thus markedly outperforming previously published scores. CONCLUSION: BCAAs could be an important link between obesity and other metabolic pathways. A BCAA-based metabolic score can predict steatosis grade in high-risk children and adolescents and may provide a feasible alternative to sophisticated methods like MRI or biopsy in the future.

Quantification of liver function using gadoxetic acid-enhanced MRI.

The introduction of hepatobiliary contrast agents, most notably gadoxetic acid (GA), has expanded the role of MRI, allowing not only a morphologic but also a functional evaluation of the hepatobiliary system. The mechanism of uptake and excretion of gadoxetic acid via transporters, such as organic anion transporting polypeptides (OATP1,3), multidrug resistance-associated protein 2 (MRP2) and MRP3, has been elucidated in the literature. Furthermore, GA uptake can be estimated on either static images or on dynamic imaging, for example, the hepatic extraction fraction (HEF) and liver perfusion. GA-enhanced MRI has achieved an important role in evaluating morphology and function in chronic liver diseases (CLD), allowing to distinguish between the two subgroups of nonalcoholic fatty liver diseases (NAFLD), simple steatosis and nonalcoholic steatohepatitis (NASH), and help to stage fibrosis and cirrhosis, predict liver transplant graft survival, and preoperatively evaluate the risk of liver failure if major resection is planned. Finally, because of its noninvasive nature, GA-enhanced MRI can be used for long-term follow-up and post-treatment monitoring. This review article aims to describe the current role of GA-enhanced MRI in quantifying liver function in a variety of hepatobiliary disorders.

Consensus report from the 8th International Forum for Liver Magnetic Resonance Imaging.

OBJECTIVES: The 8th International Forum for Liver Magnetic Resonance Imaging (MRI), held in Basel, Switzerland, in October 2017, brought together clinical and academic radiologists from around the world to discuss developments in and reach consensus on key issues in the field of gadoxetic acid-enhanced liver MRI since the previous Forum held in 2013. METHODS: Two main themes in liver MRI were considered in detail at the Forum: the use of gadoxetic acid for contrast-enhanced MRI in patients with liver cirrhosis and the technical performance of gadoxetic acid-enhanced liver MRI, both opportunities and challenges. This article summarises the expert presentations and the delegate voting on consensus statements discussed at the Forum. RESULTS AND CONCLUSIONS: It was concluded that gadoxetic acid-enhanced MRI has higher sensitivity for the diagnosis of hepatocellular carcinoma (HCC), when compared with multidetector CT, by utilising features of hyperenhancement in the arterial phase and hypointensity in the hepatobiliary phase (HBP). Recent HCC management guidelines recognise an increasing role for gadoxetic acid-enhanced MRI in early diagnosis and monitoring post-resection. Additional research is needed to define the role of HBP in predicting microvascular invasion, to better define washout during the transitional phase in gadoxetic acid-enhanced MRI for HCC diagnosis, and to reduce the artefacts encountered in the arterial phase. Technical developments are being directed to shortening the MRI protocol for reducing time and patient discomfort and toward utilising faster imaging and non-Cartesian free-breathing approaches that have the potential to improve multiphasic dynamic imaging. KEY POINTS: • Gadoxetic acid-enhanced MRI provides higher diagnostic sensitivity than CT for diagnosing HCC. • Gadoxetic acid-enhanced MRI has roles in early-HCC diagnosis and monitoring post-resection response. • Faster imaging and free-breathing approaches have potential to improve multiphasic dynamic imaging.

PET/MRI versus PET/CT in oncology: a prospective single-center study of 330 examinations focusing on implications for patient management and cost considerations.

PURPOSE: PET/MRI has recently been introduced into clinical practice. We prospectively investigated the clinical impact of PET/MRI compared with PET/CT, in a mixed population of cancer patients, and performed an economic evaluation of PET/MRI. METHODS: Cancer patients referred for routine staging or follow-up by PET/CT underwent consecutive PET/CT and PET/MRI, using single applications of [18F]FDG, [68Ga]Ga-DOTANOC, or [18F]FDOPA, depending on tumor histology. PET/MRI and PET/CT were rated separately, and lesions were assessed per anatomic region; based on regions, per-examination and per-patient accuracies were determined. A simulated, multidisciplinary team meeting served as reference standard and determined whether differences between PET/CT and PET/MRI affected patient management. The McNemar tests were used to compare accuracies, and incremental cost-effectiveness ratios (ICERs) for PET/MRI were calculated. RESULTS: Two hundred sixty-three patients (330 same-day PET/CT and PET/MRI examinations) were included. PET/MRI was accurate in 319/330 examinations and PET/CT in 277/330 examinations; the respective accuracies of 97.3% and 83.9% differed significantly (P < 0.001). The additional findings on PET/MRI-mainly liver and brain metastases-had implications for patient management in 21/263 patients (8.0%). The per-examination cost was 596.97 EUR for PET/MRI and 405.95 EUR for PET/CT. ICERs for PET/MRI were 14.26 EUR per percent of diagnostic accuracy and 23.88 EUR per percent of correctly managed patients. CONCLUSIONS: PET/MRI enables more appropriate management than PET/CT in a nonnegligible fraction of cancer patients. Since the per-examination cost is about 50% higher for PET/MRI than for PET/CT, a histology-based triage of patients to either PET/MRI or PET/CT may be meaningful.