Characterization of renal tumors is critical to determine the best therapeutic approach and improve overall patient survival. Because of increased use of high-resolution cross-sectional imaging in clinical practice, renal masses are being discovered with increased frequency. As a result, accurate imaging characterization of these lesions is more important than ever. However, because of the wide array of imaging features encountered as well as overlapping characteristics, identifying reliable imaging criteria for differentiating malignant from benign renal masses remains a challenge. Multiparametric magnetic resonance (MR) imaging based on various anatomic and functional parameters has an important role and adds diagnostic value in detection and characterization of renal masses. MR imaging may allow distinction of benign solid renal masses from several renal cell carcinoma (RCC) subtypes, potentially suggest the histologic grade of a neoplasm, and play an important role in ensuring appropriate patient management to avoid unnecessary surgery or other interventions. It is also a useful noninvasive imaging tool for patients who undergo active surveillance of renal masses and for follow-up after treatment of a renal mass. The purpose of this article is to review the characteristic MR imaging features of RCC and common benign renal masses and propose a diagnostic imaging approach to evaluation of solid renal masses using multiparametric MR imaging. RSNA, 2017.

Purpose: To evaluate the utility of diffusion-weighted magnetic resonance imaging (DWI) in pancreatic ductal adenocarcinoma with various grades of differentiation. Materials and Methods:Following Institutional Review Board (IRB) approval, 21 consecutive patients with surgical pathology-proven pancreatic adenocarcinomas were retrospectively evaluated. Histopathologic characteristics and grades of differentiation of adenocarcinomas were analyzed. Twenty-one patients without a known history of pancreatic disease were evaluated as the control group. Anatomic MR images and DW images were acquired using 1.5-T MR systems. DWI with b values of 0 and 500 sec/ mm 2 were performed on both patients and control groups. The difference in mean apparent diffusion coefficient (ADC) values among groups of normal pancreatic parenchyma, adenocarcinomas with poor differentiation, and adenocarcinomas with well/moderate differentiation were compared using one-way analysis of variance.Results: Mean ADCs of pancreatic adenocarcinomas (1.77 6 0.45 Â 10 À3 mm 2 /sec) was not significantly lower than that of normal parenchyma (1.98 6 0.31) (P ¼ 0.09). When adenocarcinomas were subdivided based on grades of differentiation, however, poorly differentiated adenocarcinoma with histopathologic characteristics of limited glandular formation and dense fibrosis had significantly lower ADCs (1.46 6 0.17) compared to those of well/moderately differentiated adenocarcinomas (2.10 6 0.42) characterized by neoplastic tubular structures (P < 0.01). Well/moderately differentiated adenocarcinomas with dense fibrosis showed significantly lower ADC values (1.49 6 0.19) than those with loose fibrosis (2.26 6 0.30) (P ¼ 0.01).Conclusion: Difference in ADC values using DWI between poorly and well/moderately differentiated pancreatic ductal adenocarcinoma may relate to differences in glandular formation and density of fibrosis.

Purpose To compare the diagnostic accuracy of MR elastography and anatomic MR imaging features in the diagnosis of severe hepatic fibrosis and cirrhosis. Materials and Methods Three readers independently assessed presence of morphological changes associated with hepatic fibrosis in 72 patients with liver biopsy including: caudate to right lobe ratios, nodularity, portal venous hypertension (PVH) stigmata, posterior hepatic notch, expanded gallbladder fossa and right hepatic vein caliber. Three readers measured shear stiffness values using quantitative shear stiffness maps (elastograms). Sensitivity, specificity and diagnostic accuracy of stiffness values and each morphological feature were calculated. Inter-reader agreement was summarized using weighted kappa statistics. Intra-class correlation coefficient was used to assess inter-reader reproducibility of stiffness measurements. Binary logistic regression was used to assess inter-reader variability for dichotomized stiffness values and each morphological feature. Results Using 5.9 kPa as a cut-off for differentiating F3–F4 from F0–2 stages, overall sensitivity, specificity and diagnostic accuracy for MR elastography were 85.4%, 88.4 % and 87% respectively. Overall inter-reader agreement for stiffness values was substantial, with insignificant difference (p=0.74) in the frequency of differentiating F3–4 from F0–2 fibrosis. Only hepatic nodularity and PVH stigmata showed moderately high overall accuracy of 69.4% and 72.2%. Inter-reader agreement was substantial only for PVH stigmata, moderate for C/R m, deep notch and expanded gallbladder fossa. Only posterior hepatic notch (p=0.82) showed no significant difference in reader rating. Conclusion MR elastography is a non-invasive, accurate and reproducible technique compared with conventional features of detecting severe hepatic fibrosis.

This article reviews the imaging findings associated with acute pancreatitis and its complications on cross-sectional imaging and discusses the role of imaging in light of this revision.

Liver and spleen size were measured in 11 normal subjects and 12 patients with cirrhosis. Volume was calculated by adding together the area measurements obtained from successive transverse abdominal scans. The normal mean volume of the liver (+/- S.D.) was 1,493 +/- 230 cm3 and that of the spleen was 219 +/- 76 cm3; interobserver variability was 4-8% and the day-to-day coefficient of variation was 6-10%. In cirrhotic patients studied prior to and 7-10 days after a distal splenorenal shunt, the mean liver volume fell from 1,642 to 1,529 cm3 (p less than 0.06) and the mean spleen volume from 660 to 507 cm3 (p less than 0.006), supporting the use of such a shunt in selective decompression of varices and maintenance of portal hypertension. This is a clinically useful method of measuring organ volume with the required sensitivity.

The ACR Committee on Incidental Findings presents recommendations for managing liver lesions that are incidentally detected on CT. These recommendations represent an update from the liver component of the ACR 2010 white paper on managing incidental findings in the pancreas, adrenal glands, kidneys, and liver. The Liver Subcommittee-which included five abdominal radiologists, one hepatologist, and one hepatobiliary surgeon-developed this algorithm. The recommendations draw from published evidence and expert opinion and were finalized by informal iterative consensus. Algorithm branches categorize liver lesions on the basis of patient characteristics and imaging features. They terminate with an assessment of benignity or a specific follow-up recommendation. The algorithm addresses most, but not all, pathologies and clinical scenarios. The goal is to improve the quality of care by providing guidance on how to manage incidentally detected liver lesions.

Hepatic fibrosis is potentially reversible, however early diagnosis is necessary for treatment in order to halt progression to cirrhosis and development of complications including portal hypertension and hepatocellular carcinoma. Morphologic signs of cirrhosis on ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) alone are unreliable and are seen with more advanced disease. Newer imaging techniques to diagnose liver fibrosis are reliable and accurate, and include magnetic resonance elastography and US elastography (1 dimensional transient elastography and point shear wave elastography or acoustic radiation force impulse imaging). Research is ongoing with multiple other techniques for the noninvasive diagnosis of hepatic fibrosis, including MRI with diffusion weighted imaging, hepatobiliary contrast enhancement, and perfusion; CT using perfusion, fractional extracellular space techniques, and dual energy, contrast-enhanced US, texture analysis in multiple modalities, quantitative mapping, and direct molecular imaging probes. Efforts to advance the noninvasive imaging assessment of hepatic fibrosis will facilitate earlier diagnosis and improved patient monitoring with the goal of preventing the progression to cirrhosis and its complications.

Improvements in radiologic imaging technology and therapeutic options available for management of tumors have necessitated the revision of guidelines for the imaging-based assessment of tumor response to therapy. The purpose of this article is to familiarize radiologists with the modifications to the Response Evaluation Criteria in Solid Tumors (RECIST) that have been incorporated in the latest version of the guidelines, RECIST 1.1. The most important differences between this version and the previous one, RECIST 1.0, include reductions in the maximum number of lesions per patient and per organ that may be targeted for measurement, augmentation of the criteria defining progressive disease, additional guidelines for reporting findings of lesions that are too small to measure and for measuring lesions that appear to have fragmented or coalesced at follow-up imaging, new criteria for characterizing lymphadenopathy, new criteria for selecting bone lesions and cystic lesions as targets for measurement, and the inclusion of findings at positron emission tomography among the indicators of disease response.