Three-dimensional MR Cholangiopancreatography in a Breath Hold with Sparsity-based Reconstruction of Highly Undersampled Data.

Purpose To develop a three-dimensional breath-hold (BH) magnetic resonance (MR) cholangiopancreatographic protocol with sampling perfection with application-optimized contrast using different flip-angle evolutions (SPACE) acquisition and sparsity-based iterative reconstruction (SPARSE) of prospectively sampled 5% k-space data and to compare the results with conventional respiratory-triggered (RT) acquisition. Materials and Methods This HIPAA-compliant prospective study was institutional review board approved. Twenty-nine patients underwent conventional RT SPACE and BH-accelerated SPACE acquisition with 5% k-space sampling at 3 T. Spatial resolution and other parameters were matched when possible. BH SPACE images were reconstructed by enforcing joint multicoil sparsity in the wavelet domain (SPARSE-SPACE). Two board-certified radiologists independently evaluated BH SPARSE-SPACE and RT SPACE images for image quality parameters in the pancreatic duct and common bile duct by using a five-point scale. The Wilcoxon signed-rank test was used to compare BH SPARSE-SPACE and RT SPACE images. Results Acquisition time for BH SPARSE-SPACE was 20 seconds, which was significantly (P < .001) shorter than that for RT SPACE (mean ± standard deviation, 338.8 sec ± 69.1). Overall image quality scores were higher for BH SPARSE-SPACE than for RT SPACE images for both readers for the proximal, middle, and distal pancreatic duct, but the difference was not statistically significant (P > .05). For reader 1, distal common bile duct scores were significantly higher with BH SPARSE-SPACE acquisition (P = .036). More patients had acceptable or better overall image quality (scores ≥ 3) with BH SPARSE-SPACE than with RT SPACE acquisition, respectively, for the proximal (23 of 29 [79%] vs 22 of 29 [76%]), middle (22 of 29 [76%] vs 18 of 29 [62%]), and distal (20 of 29 [69%] vs 13 of 29 [45%]) pancreatic duct and the proximal (25 of 28 [89%] vs 22 of 28 [79%]) and distal (25 of 28 [89%] vs 24 of 28 [86%]) common bile duct. Conclusion BH SPARSE-SPACE showed similar or superior image quality for the pancreatic and common duct compared with that of RT SPACE despite 17-fold shorter acquisition time. (©) RSNA, 2016.

Utility of diffusion-weighted MRI for differentiating acute from chronic cholecystitis.

PURPOSE: To assess the use of diffusion-weighted imaging (DWI) for differentiating acute from chronic cholecystitis, in comparison with conventional magnetic resonance imaging (MRI) features. MATERIALS AND METHODS: Liver MRI including DWI (b-values 0/500/1000s/mm(2) ) was performed at 1.5T ≤30 days before cholecystectomy in 83 patients with abdominal pain. Two radiologists assessed cases for conventional (gallstones, wall thickening, pericholecystic fluid, pericholecystic fat changes, gallbladder distension, pericholecystic liver enhancement, mural T2 -hyperintensity, mural hyperenhancement, mural striations, abscess, intraluminal membranes, and mural defect) and DWI (increased mural signal on high b-value images, visually low apparent diffusion coefficient [ADC], and ADC values) features. RESULTS: Acute cholecystitis was present in 43%; chronic cholecystitis was present in 57%. Nine of 12 conventional features were more frequent in acute cholecystitis for both readers (P ≤ 0.003). Increased mural signal on high b-value images was more frequent (P < 0.001) in acute than chronic cholecystitis for R1 (92% vs. 32%) and R2 (83% vs. 30%). Sensitivity and specificity of increased signal on high b-value images were: R1, 92%/68%; R2, 83%/70%. Visually low ADC was more frequent in acute cholecystitis for R2 (P < 0.001) but not R1 (P = 0.406); ADC values were not different between groups for either reader (P = 0.104-0.139). Among conventional and DWI features, only increased signal on high b-value DWI was independently associated with acute cholecystitis for both readers (P = 0.006-0.012). CONCLUSION: Visually increased mural signal on high b-value DWI was highly sensitive and moderately specific for acute cholecystitis, being an independent predictor relative to conventional features for both readers. Although requiring larger studies, DWI (particularly the high b-value images) may have additive value relative to conventional MRI-suspected acute cholecystitis. J. Magn. Reson. Imaging 2016;44:89-97.

Length of capsular contact for diagnosing extraprostatic extension on prostate MRI: Assessment at an optimal threshold.

PURPOSE: To evaluate the length of capsular contact of dominant lesions on multiparametric prostate magnetic resonance imaging (MRI) for predicting extraprostatic extension (EPE) and to determine a threshold value to apply in clinical practice. MATERIALS AND METHODS: Ninety patients undergoing 3T prostate MRI before prostatectomy were included. Two independent readers (R1, R2) recorded for each lobe the presence or absence of capsular irregularity on T2 -weighted imaging (T2 WI) and of overt measurable EPE. Readers also recorded the length of capsular contact of each lobe's dominant lesion for T2 WI and the apparent diffusion coefficient (ADC) map. Based on prostatectomy specimens, EPE was recorded for each lobe and classified as focal (single focus ≤0.5 mm in depth) vs. established. Receiver operating characteristic analysis, logistic regression, and kappa coefficients were used to assess interpretive approaches on a side-specific basis. RESULTS: The optimal thresholds were 6 mm and 7 mm of contact using T2 WI and ADC for any EPE, and 10 mm and 7 mm using T2 WI and ADC for nonfocal EPE (AUCs 81.0-82.5%). Capsular contact had higher sensitivity, yet lower specificity, than subjective interpretations for any EPE and for nonfocal EPE (all P ≤ 0.018, aside from any EPE for R2 using ADC). Length of contact exhibited more substantial gains in sensitivity (9-20% for any EPE; 34-41% for nonfocal EPE) than losses in specificity (6-13% for any EPE; 17-27% for nonfocal EPE) compared with subjective interpretations. Interreader agreement: 0.70 for assessments based on length of contact; 0.49-0.59 for subjective assessments. CONCLUSION: Length of capsular contact of dominant lesions can improve interreader agreement and sensitivity for EPE compared with subjective features, with relatively mild specificity loss.

MRI Evaluation of the Urothelial Tract: Pitfalls and Solutions.

OBJECTIVE: MR urography (MRU) can be an alternative to CT urography (CTU) for imaging of the kidneys, urinary bladder, and collecting systems. MRU can be a challenging examination to perform and interpret, which may result in technical and interpretive errors being made. This article highlights the pitfalls associated with MRU and discusses how to recognize and avoid them. CONCLUSION: When performed properly, MRU may provide imaging quality generally comparable to that of CTU, and it enables comprehensive evaluation of the entire urinary tract.

Hematologic malignancies of the liver: spectrum of disease.

The incidence of hematologic malignancies and their extranodal manifestations is continuously increasing. Previously unsuspected hepatic involvement in hematologic malignancies such as Hodgkin disease and non-Hodgkin lymphoma, posttransplant lymphoproliferative disorder, myeloid sarcoma (chloroma), multiple myeloma, Castleman disease, and lymphohistiocytosis may be seen by radiologists. Although the imaging features of more common hepatic diseases such as hepatocellular carcinoma, metastases, and infection may overlap with those of hepatic hematologic malignancies, combining the imaging features with clinical manifestations and laboratory findings can facilitate correct diagnosis. Clinical features that suggest a hematologic neoplasm as the cause of liver lesions include a young patient (<40 years of age), no known history of cancer, abnormal bone marrow biopsy results, fever of unknown origin, and night sweats. Imaging features that suggest hematologic malignancy include hepatosplenomegaly or splenic lesions, vascular encasement by a tumor without occlusion or thrombosis, an infiltrating mass at the hepatic hilum with no biliary obstruction, and widespread adenopathy above and below the diaphragm. Familiarity with the imaging features of hepatic hematologic malignancies permits correct provisional diagnosis and may influence therapeutic management. For example, when biopsy is performed, core biopsy may be needed in addition to fine-needle aspiration so that the tissue architecture of the neoplasm can be discerned. The predominant treatment of hematologic malignancies is chemotherapy or radiation therapy rather than surgery. Online supplemental material is available for this article.

Three-dimensional conformal radiation therapy in the liver: MRI findings along a time continuum.

Recent development of 3-dimensional conformal radiation therapies provides a concentrated radiation dose to the tumor. To achieve this goal, a complex design of multiple narrow beamlets is used to shape the radiation exposure to conform to the shape of the tumor. Imaging findings after novel radiation therapy techniques differ from those of conventional radiation therapy. This article discusses changes in the liver parenchyma and tumor after conformal radiation therapy focusing on magnetic resonance imaging.

Hematologic malignancies of the pancreas.

Hematologic malignancies are relatively uncommon neoplasms of abdominal soft tissue. This article discusses the clinical and imaging features of pancreatic lymphoma, pancreatic extraosseous multiple myeloma, granulocytic sarcoma (chloroma), posttransplant lymphoproliferative disorder, and Castleman disease. The combination of imaging findings and the appropriate clinical presentation should allow the radiologist to raise a provisional diagnosis of hematologic malignancy.

Uncommon pancreatic tumors and pseudotumors.

A heterogeneous group of uncommon neoplastic and non-neoplastic pancreatic pathologies exists that can mimic pancreatic adenocarcinoma. These "imitators" are unique and may demonstrate characteristic clinical and imaging features. Imaging characteristics of some of these diverse lesions are not well described in the literature, and erroneous diagnoses of these entities as pancreatic carcinoma may be responsible for unnecessary surgeries. Knowledge of these selected pancreatic pathologies is essential to facilitate optimal patient management.

Recent advances in the diagnosis and management of autoimmune pancreatitis.

OBJECTIVE: Autoimmune pancreatitis (AIP) is a rare chronic relapsing steroid-responsive fibroinflammatory disorder of the pancreas that is likely caused by immune dysregulation. It is now thought that AIP consists of two distinct clinicopathologic syndromes currently designated as types 1 and 2. CONCLUSION: A current update on etiopathogenesis, pathology, and clinical and imaging findings of AIP is provided with an emphasis on diagnosis and management.

Imaging of the porta hepatis: spectrum of disease.

A wide array of pathologic conditions can arise within the porta hepatis, which encompasses the portal triad (the main portal vein, common hepatic artery, and common bile ducts), lymphatics, nerves, and connective tissue. Major vascular diseases of the portal triad include thrombosis, stenosis, and aneurysm. Portal vein thrombosis can complicate liver cirrhosis and hepatocellular carcinoma and has important therapeutic implications. Hepatic artery thrombosis and stenosis require immediate attention to reduce graft loss in liver transplant recipients. Congenital (eg, choledochal cyst) and acquired (benign and malignant) diseases of the biliary system can manifest as mass lesions in the porta hepatis. Lymphadenopathy can arise from neoplastic and nonneoplastic entities. Uncommon causes of mass lesions arise from nerves (eg, neurofibroma, neurofibrosarcoma) and connective tissue (sarcomas) and are rare. The hepatoduodenal ligament is a peritoneal reflection at the porta hepatis and is an important route for the spread of pancreatic and gastrointestinal cancers. Imaging plays a major role in diagnosis and enables appropriate management. Ultrasonography accurately demonstrates anatomic variations and pathologic conditions and is the initial modality of choice for detection of vascular and biliary lesions. Multidetector computed tomography and magnetic resonance imaging allow characterization and differentiation of various masses in the porta hepatis. Imaging-guided interventions, including embolization and stent placement, also play a key role in disease management.

The mysterious organ. Spectrum of focal lesions within the splenic parenchyma: cross-sectional imaging with emphasis on magnetic resonance imaging.

Incidental splenic lesions are frequently encountered at imaging performed for unrelated causes. Splenic cysts, hemangiomas, and lymphomatous involvement are the most frequently encountered entities. Computed tomography and sonography are commonly used for initial evaluation with magnetic resonance imaging reserved as a useful problem-solving tool for characterizing atypical and uncommon lesions. The value of magnetic resonance imaging lies in classifying these lesions as either benign or malignant by virtue of their signal-intensity characteristics on T1- and T2-weighted imaging and optimal depiction of internal hemorrhage. Dynamic contrast-enhanced sequences may improve the evaluation of focal splenic lesions and allow characterization of cysts, smaller hemangiomas, and hamartomas. Any atypical or unexplained imaging feature related to an incidental splenic lesion requires additional evaluation and/or follow-up. Occasionally, biopsy or splenectomy may be required for definitive assessment given that some of tumours may demonstrate uncertain biologic behavior.

Chronic fibrosing conditions in abdominal imaging.

Chronic fibrosing conditions of the abdomen are relatively poorly understood and involve varied and often multiple organ systems. At histopathologic analysis, they share the unifying features of proliferative fibrosis and chronic inflammation. Different conditions in this group are often found in association with each other and with other fibrosing conditions outside the abdomen. Some of the confusion about these conditions stems from their complex nomenclature, which includes a gamut of alternate terms and eponyms. Many of them can be categorized within two large subgroups: the fibromatoses and immunoglobulin G4 (IgG4)-related disorders. While many of these entities are of uncertain etiology, some, especially the IgG4-associated conditions, appear to have an immune-mediated pathogenesis. Nephrogenic systemic fibrosis, sclerosing peritonitis, and retroperitoneal fibrosis have iatrogenic associations, while some of the fibromatoses are genetically inherited. Imaging differentiation of these conditions is difficult due to considerable overlap in their radiologic findings. However, certain conditions such as penile fibromatosis and sclerosing peritonitis may have unique imaging features that can help the radiologist make the diagnosis. Others such as deep fibromatoses and inflammatory pseudotumor demonstrate fibroproliferative mass formation and cannot be differentiated from neoplastic conditions at imaging. Thus, histopathologic correlation is often required to confirm their diagnosis.

Current concepts in the imaging of uterine sarcoma.

Recent advances in genetics and pathology have improved our understanding of diagnosis and staging of uterine sarcomas. The major types of uterine sarcomas include leiomyosarcoma, low-grade endometrial stromal sarcoma, undifferentiated endometrial sarcoma, adenosarcoma and carcinosarcoma. The distinctive biological behavior and poor overall survival of uterine sarcoma create challenges in the management of these tumors. We herein present a comprehensive review of taxonomy, epidemiology, pathology, imaging findings and natural history of a wide spectrum of uterine sarcomas.

Uncommon primary pelvic retroperitoneal masses in adults: a pattern-based imaging approach.

There is a broad spectrum of primary pelvic retroperitoneal masses in adults that demonstrate characteristic epidemiologic and histopathologic features and natural histories. These masses may be classified into five distinct subgroups using a pattern-based approach that takes anatomic distribution and certain imaging characteristics into account, allowing greater accuracy in their detection and characterization and helping to optimize patient management. The five groups are cystic (serous and mucinous epithelial neoplasms, pelvic lymphangioma, tailgut cyst, ancient schwannoma), vascular or hypervascular (solitary fibrous tumor, paraganglioma, pelvic arteriovenous malformation, Klippel-Trénaunay-Weber syndrome, extraintestinal GIST [gastrointestinal stromal tumor]), fat-containing (lipoma, liposarcoma, myelolipoma, presacral teratoma), calcified (calcified lymphocele, calcified rejected transplant kidney, rare sarcomas), and myxoid (schwannoma, plexiform neurofibroma, myxoma).Cross-sectional imaging modalities help differentiate the more common gynecologic neoplasms from more unusual masses. In particular, the tissue-specific multiplanar capability of high-resolution magnetic resonance imaging permits better tumor localization and internal characterization, thereby serving as a road map for surgery.

Laparoscopic adjustable gastric banding: what radiologists need to know.

Laparoscopic adjustable gastric banding (LAGB) is performed with increasing frequency for the management of morbid obesity. Although LAGB is less invasive than other bariatric surgical procedures, it is associated with various complications that may lead to nonspecific abdominal symptoms several months or years after the procedure. Because complications of LAGB may be encountered incidentally at imaging for other indications, all radiologists should be familiar with the appearances of correctly positioned and malpositioned gastric bands, normal and abnormal appearances of the postprocedural pouch and stomach, and imaging features suggestive or indicative of early or delayed complications of LAGB. Familiarity with the techniques and systems currently approved by the Food and Drug Administration for use in this procedure may help radiologists detect postoperative complications and guide their management. Both commercially available systems include a silicone gastric band with an inflatable inner surface, a reservoir port, and a tube that connects the port to the gastric band. All these components of LAGB systems should be visible at radiologic imaging; however, older models of gastric bands may not be radiopaque and therefore may not be depicted on images. The most common complications of LAGB are gastric band slippage and associated pouch dilatation, intragastric erosion of the band, gastric perforation, and abscess formation. Complications that occur with less frequency include tube migration, tube disconnection, port-site infection, and small bowel obstruction.

Immunological diseases of the pancreatico-hepatobiliary system: update on etiopathogenesis and cross-sectional imaging findings.

Immunological diseases of the hepatobiliary system and the pancreas include a broad spectrum of disorders that manifest characteristic histopathology/serology and variable clinical features and imaging findings. Recent studies have thrown fresh light on the complex role of genetics and autoimmunity in the pathogenesis and natural history of these diverse disorders that include autoimmune hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis, IgG4-related cholangitis, overlap/outlier syndromes, and autoimmune pancreatitis.

Rare (<1%) histological subtypes of renal cell carcinoma: an update.

Recent advances in genetics and pathology have allowed description of several new histological subtypes of renal cell carcinoma (RCC) as well as better characterization of other rare subtypes. We herein present a comprehensive review of taxonomy, epidemiology, pathology, imaging findings, and natural history of a wide spectrum of rare subtypes of RCCs that individually constitute <1% of all the RCCs.

Mesenchymal neoplasms of the urinary bladder: a comprehensive review with focus on cross-sectional imaging findings.

Mesenchymal neoplasms of the urinary bladder are exceedingly rare and display remarkable diversity. These tumors demonstrate distinct pathological features as well as variable biological behavior and cross-sectional imaging findings. The rarity of tumors, nonspecific symptoms and seemingly normal cystoscopic findings (particularly with small and exophytic tumors) frequently lead to misdiagnosis or missed diagnosis. While some tumors display characteristic cross-sectional imaging findings that may suggest a diagnosis, imaging findings are mostly nonspecific. Histopathological examination is required for accurate diagnosis, management and prognostication. The purpose of this article is to review the cross-sectional imaging findings of a diverse spectrum of mesenchymal tumors of the urinary bladder.

Recent advances in cytogenetics and molecular biology of adult hepatocellular tumors: implications for imaging and management.

Focal nodular hyperplasia (FNH), hepatocellular adenoma (HCA), and hepatocellular carcinoma (HCC) compose hepatocellular neoplasms that occur in adults. These tumors demonstrate characteristic epidemiologic and histopathologic features and clinical and imaging manifestations. HCAs are monoclonal neoplasms characterized by increased predilection to hemorrhage or rupture and occasional transformation to HCC. On the other hand, FNH is a polyclonal tumorlike lesion that occurs in response to increased perfusion and has an indolent clinical course. Up to 90% of HCCs occur in the setting of cirrhosis. Chronic viral hepatitis (hepatitis B and hepatitis C) infection and metabolic syndrome are major risk factors that can induce HCCs in nonfibrotic liver. Recent advances in pathology and genetics have led to better understanding of the histogenesis, natural history, and molecular events that determine specific oncologic pathways used by these neoplasms. HCAs are now believed to result from specific genetic mutations involving TCF1 (transcription factor 1 gene), IL6ST (interleukin 6 signal transducer gene), and CTNNB1 (ß catenin-1 gene); FNHs are characterized by an "imbalance" of angiopoietin. While the ß catenin signaling pathway is associated with well- and moderately differentiated HCCs, mutations involving p53 (tumor protein 53 gene), MMP14 (matrix metalloproteinase 14 gene), and RhoC (Ras homolog gene family, member C) are associated with larger tumor size, higher tumor grade with resultant shortened tumor-free survival, and poor prognosis. Fibrolamellar carcinoma (FLC), a unique HCC subtype, exhibits genomic homogeneity that partly explains its better overall prognosis. On the basis of recent study results involving cytogenetics and oncologic pathways of HCCs, novel drugs that act against molecular targets are being developed. Indeed, sorafenib (a multikinase inhibitor) is currently being used in the successful treatment of patients with advanced HCC. Characterization of genetic abnormalities and genotype-phenotype correlations in adult hepatocellular tumors provides better understanding of tumor pathology and biology, imaging findings, prognosis, and response to molecular therapeutics.

Benign biliary strictures: a current comprehensive clinical and imaging review.

OBJECTIVE: There is a wide spectrum of nonneoplastic causes of biliary stricture that can pose a significant challenge to clinicians and radiologists. Imaging plays a key role in differentiating benign from malignant strictures, defining the extent, and directing the biopsy. We describe the salient clinical and imaging manifestations of benign biliary strictures that will help radiologists to accurately diagnose these entities. CONCLUSION: Accurate diagnosis and management are based on correlating imaging findings with epidemiologic, clinical, and laboratory data. Cross-sectional imaging modalities permit precise localization of the site and length of the segment involved, thereby serving as a road map to surgery, and permit exclusion of underlying malignancy.