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.

Differentiation of Malignant Omental Caking from Benign Omental Thickening using MRI.

PURPOSE: To determine multi-parametric MRI features that can help differentiate malignant omental caking from benign omental thickening in the setting of portal hypertension. METHODS: We identified 19 patients with an abnormal omentum on MRI and an available reference standard: 11 patients with portal hypertension and benign omental thickening (9 male, 2 female, mean age 58 ± 6 years) and 8 patients with metastatic omental caking (4 male, 4 female, mean age 61 ± 13 years). Criteria for benign omental thickening were no evidence of malignancy for at least 24 months of follow-up (n = 7), negative ascites cytology (n = 2), or absence of malignancy on pathologic analysis of liver explant (n = 2). Criteria for omental malignancy were positive omental biopsy (n = 6) or ascites cytology (n = 2). Two radiologists (R1 and R2) evaluated characteristics of the thickened omentum on MRI. RESULTS: Findings occurring with significantly higher frequency in malignant omental caking were hyperintensity on high b-value diffusion-weighted imaging (DWI) (R1 88% vs. 0%, R2 88% vs. 0%), hyperenhancement (R1 75% vs. 0%, R2 75% vs. 0%), and convex outer omental contour (R1 88% vs. 0%, R2 75% vs. 9%) (all p ≤ 0.001); discrete omental nodules were significantly more frequent in malignant omental thickening for R1 (63% vs. 0%, p = 0.005). Features not significantly different between groups included decreased ADC, T2 hyperintensity, vessels coursing through the omentum, moderate/large volume ascites, splenomegaly, and mesenteric edema (all p ≥ 0.058). CONCLUSION: Abnormal signal on DWI, hyperenhancement, and convex outer contour are helpful MRI features to differentiate malignant from benign omental thickening.

Comparison of MRI pulse sequences for prediction of size of hepatocellular carcinoma at explant evaluation.

OBJECTIVE: The purpose of this study was to retrospectively compare the size of hepatocellular carcinoma (HCC) on images obtained using different MRI pulse sequences with the tumor size determined at pathologic evaluation of liver explant specimens. MATERIALS AND METHODS: Ninety-two patients with HCC who underwent contrast-enhanced liver MRI within 90 days before liver transplant were included. A single pathologist measured the dominant HCC in each case. In different sessions, two abdominal radiologists (readers 1 and 2) aware only of the location of the dominant HCC independently measured lesion size on images obtained using the following sequences: T2-weighted imaging; b-500 diffusion-weighted imaging; and arterial, portal venous, and equilibrium phases of contrast enhancement. Size measurements on MR images were compared with explant measurements by use of Pearson correlation coefficients, paired t tests, and Bland-Altman plots. RESULTS: Correlation with pathologic findings was highest for reader 1 for portal venous (r = 0.890) and equilibrium (r = 0.828) phase images and for reader 2 for arterial, portal venous, and equilibrium phase images (r = 0.842-0.860). Absolute error relative to pathologic size was lowest for reader 1 using portal venous (4.3 mm) and for reader 2 using portal venous and arterial phase images (both 4.7 mm). Systematic error for both readers was lowest with portal venous and equilibrium phase images (reader 1, systematic under-measurement of 0.5 mm in both sequences; reader 2, systematic over-measurement of 0.1 mm with portal venous phase images and systematic under-measurement of 1.1 mm with equilibrium phase images). Sequences in which reader 1 made systematic over-measurements were diffusion-weighted images, arterial phase images, and T2-weighted images (by 3.5, 2.9, and 1.6 mm). Reader 2 made systematic over-measurements using arterial phase and T2-weighted images (by 1.5 and 0.4 mm). CONCLUSION: The data suggest the arterial phase may be suboptimal for measuring HCC at MRI. Portal venous phase acquisition warrants further investigation as a potential standard approach for such measurements.

Comparison of intra- and inter-reader agreement of abbreviated versus comprehensive MRCP for pancreatic cyst surveillance.

OBJECTIVE: To retrospectively compare inter- and intra-reader agreement of abbreviated MRCP (aMRCP) with comprehensive MRI (cMRCP) protocol for detection of worrisome features, high-risk stigmata, and concomitant pancreatic cancer in pancreatic cyst surveillance. METHODS: 151 patients (104 women, mean age: 69[10] years) with baseline and follow-up contrast-enhanced MRIs were included. This comprised 138 patients under cyst surveillance with 5-year follow-up showing no pancreatic ductal adenocarcinoma (PDAC), 6 with pancreatic cystic lesion-derived malignancy, and 7 with concomitant PDAC. The aMRCP protocol used four sequences (axial and coronal Half-Fourier Single-shot Turbo-spin-Echo, axial T1 fat-saturated pre-contrast, and 3D-MRCP), while cMRCP included all standard sequences, including post-contrast. Three blinded abdominal radiologists assessed baseline cyst characteristics, worrisome features, high-risk stigmata, and PDAC signs using both aMRCP and cMRCP, with a 2-week washout period. Intra- and inter-reader agreement were calculated using Fleiss' multi-rater kappa and Intra-class Correlation Coefficient (ICC). 95% confidence intervals (CI) were calculated. RESULTS: Cyst size, growth, and abrupt main pancreatic duct transition had strong intra- and inter-reader agreement. Intra-reader agreement was ICC = 0.93-0.99 for cyst size, ICC = 0.71-1.00 for cyst growth, and kappa = 0.83-1.00 for abrupt duct transition. Inter-reader agreement for cyst size was ICC = 0.86 (aMRCP) and ICC = 0.83 (cMRCP), and for abrupt duct transition was kappa = 0.84 (aMRCP) and kappa = 0.69 (cMRCP). Thickened cyst wall, mural nodule and cyst-duct communication demonstrated varying intra-reader agreements and poor inter-reader agreements. CONCLUSION: aMRCP showed high intra- and inter-reader agreement for most pancreatic cyst parameters that highly rely on T2-weighted sequences.

Hepatocellular carcinoma: detection with diffusion-weighted versus contrast-enhanced magnetic resonance imaging in pretransplant patients.

UNLABELLED: This study evaluates the performance of diffusion-weighted magnetic resonance imaging (DWI) for the detection of hepatocellular carcinoma (HCC) in pre-liver transplantation patients, compared and combined with contrast-enhanced T1-weighted imaging (CET1WI), using liver explant as the standard of reference. We included 52 patients with cirrhosis (40 men, 12 women; mean age, 56 years) who underwent DWI and CET1WI within 90 days of liver transplantation. Magnetic resonance images were analyzed for HCC detection in three separate sessions by two independent observers: DWI images (DW-set), CET1WI (CE-set), and all images together (All-set). Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), per-patient accuracy, and per-lesion PPV were calculated for each image set. A total of 72 HCCs were present in 33 patients at explant (mean size, 1.5 cm [range, 0.3-6.2 cm]). Per-patient sensitivity and NPV of CE-set were significantly higher than those of DW-set when using pooled data between observers (P = 0.02 and 0.03, respectively), whereas specificity, PPV, and accuracy were equivalent. Per-lesion sensitivity was significantly higher for CE-set versus DW-set (59.0% versus 43.8%; P = 0.008, pooled data from two observers). When stratified by lesion size, the difference was significant only for lesions with a size between 1 and 2 cm (42.0% for DW-set versus 74.0% for CE-set; P = 0.001). The addition of DWI to CET1WI improved sensitivity for the more experienced observer. CONCLUSION: DWI is outperformed by CET1WI for detection of HCC, but represents a reasonable alternative to CET1WI for detection of HCC with a size above 2 cm. The addition of DWI to CET1WI slightly increases the detection rate.

Hepatocellular carcinoma: perfusion quantification with dynamic contrast-enhanced MRI.

OBJECTIVE: The objective of our study was to report our initial experience with dynamic contrast-enhanced MRI (DCE-MRI) for perfusion quantification of hepatocellular carcinoma (HCC) and surrounding liver. SUBJECTS AND METHODS: DCE-MRI of the liver was prospectively performed on 31 patients with HCC (male-female ratio, 26:5; mean age, 61 years; age range, 41-83 years). A dynamic coronal 3D FLASH sequence was performed at 1.5 T before and after injection of gadolinium-based contrast agent with an average temporal resolution of 3.8 seconds. Regions of interest were drawn on the abdominal aorta, portal vein, liver parenchyma, and HCC lesions by two observers in consensus. Time-activity curves were analyzed using a dual-input single-compartment model. The following perfusion parameters were obtained: arterial flow, portal venous flow, arterial fraction, distribution volume, and mean transit time (MTT). RESULTS: Thirty-three HCCs (mean size, 3.9 cm; range, 1.1-12.6 cm) were evaluated in 26 patients. When compared with liver parenchyma, HCC showed significantly higher arterial hepatic blood flow and arterial fraction (p < 0.0001) and significantly lower distribution volume and portal venous hepatic blood flow (p < 0.0001-0.023), with no difference in MTT. Untreated HCCs (n = 16) had a higher arterial fraction and lower portal venous hepatic blood flow value than chemoembolized HCCs (n = 17, p < 0.04). CONCLUSION: DCE-MRI can be used to quantify perfusion metrics of HCC and liver parenchyma and to assess perfusion changes after HCC chemoembolization.

Magnetization transfer contrast-prepared MR imaging of the liver: inability to distinguish healthy from cirrhotic liver.

PURPOSE: To evaluate the ability of magnetization transfer (MT) contrast-prepared magnetic resonance (MR) imaging to help distinguish healthy from cirrhotic liver by using a spectrum of MT pulse frequency offsets. MATERIALS AND METHODS: This HIPAA-compliant prospective study was approved by the institutional review board. Written informed consent was obtained from all subjects. After optimization of the MT sequence by using agar phantoms with protein concentrations ranging from 0% to 4%, 20 patients with cirrhosis and portal hypertension and 20 healthy volunteers with no known liver disease underwent liver MR imaging that included eight separate breath-hold MT contrast sequences, each performed by using a different MT pulse frequency offset (range, 200-2500 Hz). Regions of interest were then placed to calculate the MT ratio for the liver, fat, and muscle in the volunteer group and for the liver in the cirrhosis group. RESULTS: MT ratio increased with decreasing MT pulse frequency offset for each of the four phantoms and the assessed in vivo tissues, consistent with previous reports. At all frequency offsets, MT ratio increased with increasing phantom protein concentration. In volunteers, at frequency offsets greater than 400 Hz, the MT ratio was significantly greater for muscle (range, 34.4%-54.9%) and significantly lower for subcutaneous fat (range, 10.3%-12.6%), compared with that for the liver (range, 22.8%-46.9%; P < .001 all comparisons). However, the MT ratio was nearly identical between healthy (range, 26.0%-80.0%) and cirrhotic livers (range, 26.7%-81.2%) for all frequency offsets (P = .162-.737), aside from a minimal difference in MT ratio of 1.7% at a frequency offset of 2500 Hz (22.8% in healthy liver vs 24.5% in cirrhotic liver) that was not significant when the Bonferroni correction was applied (P = .015). CONCLUSION: Findings of this study confirm the ability of the MT contrast-prepared sequence to help distinguish substances of varying protein concentration and suggest that MT imaging is unlikely to be of clinical utility in differentiating healthy and cirrhotic livers.

Leiomyosarcoma of the splenic vein.

Leiomyosarcomas are smooth muscle-derived tumors generally found intra-abdominally in the retoperitoneum, mesentery, or omentum. Only approximately 5% of these tumors originate from vessel wall smooth muscle. Those derived from the splenic vein are exceedingly rare, with only one previously published case in the literature. We present a second case of leiomyosarcoma of the splenic vein in a 58-year-old woman with 2 months of epigastric pain. A distal pancreatectomy was performed to include the tumor found centered in the splenic vein at the splenic and portal vein confluence and growing into the pancreas in the body on the posterior aspect. A saphenous vein patch was used for reconstruction.

The effect of liver iron deposition on hepatic apparent diffusion coefficient values in cirrhosis.

OBJECTIVE: The purpose of this study was to assess the effect of hepatic iron deposition on apparent diffusion coefficient (ADC) values measured with single-shot echo-planar imaging (EPI) diffusion-weighted MRI (DWI) in patients with liver cirrhosis and in vitro. MATERIALS AND METHODS: Fifty-two patients with liver cirrhosis who underwent breath-hold single-shot EPI DWI at 1.5 T before liver transplantation were retrospectively assessed. Estimated signal-to-noise ratio (SNRest) and ADC were measured in the right hepatic lobe (for b values of 50 and 500 s/mm2). SNRest and ADC were compared between patients stratified by pathologic iron grade using the Mann-Whitney test. Hepatic ADC values were correlated to T2* values using the Spearman correlation test in a subset of patients. In addition, a phantom consisting of solutions of varying iron concentrations was imaged with single-shot EPI DWI and T2* imaging, and iron concentration was correlated with ADC and T2*. RESULTS: In phantoms, there was a decrease in ADC and T2* with increasing iron concentration (r=-0.95 and -0.92, respectively; p<0.05). Patients with hepatic siderosis had significantly lower SNRest and ADC compared with patients without siderosis (p<0.0001). SNRest at b=50 s/mm2 and b=500 s/mm2 and ADC had a significant negative correlation with pathologic iron grade (r=-0.67 to 0.77, p<0.0001). There was a significant correlation between liver T2* and ADC (r=0.83, p<0.0001). CONCLUSION: Hepatic siderosis lowers liver ADC and should be taken into account when using ADC for diagnosing liver cirrhosis.

Hepatoportal sclerosis: CT and MRI appearance with histopathologic correlation.

OBJECTIVE: The purposes of this study were to describe the spectrum of cross-sectional imaging findings of pathologically proven hepatoportal sclerosis and to compare the features of advanced and nonadvanced hepatoportal sclerosis. MATERIALS AND METHODS: Eighteen patients with a histopathologic diagnosis of hepatoportal sclerosis who had concurrent MRI or CT images participated in the study. The following imaging features were assessed: presence of liver nodularity and liver lesions, portal vein patency, presence and degree of portal hypertension, liver volume, and caudate-to-right lobe ratio. These features were compared between patients who underwent transplant and those who did not. RESULTS: The 18 patients (11 men and one boy, six women; mean age, 46.5 years) had hepatoportal sclerosis confirmed with liver biopsy (14 patients) or explant (four patients). Fourteen patients underwent contrast-enhanced MRI, and five underwent CT. The imaging findings were as follows: liver surface nodularity, five patients (all four transplant, one nontransplant) (p = 0.0016); evidence of portal hypertension, 17 patients; increased caudate-to-right lobe ratio, 16 patients; high periportal signal intensity on T2-weighted images, six patients; portal vein occlusion with cavernous transformation, five patients. The transplant patients had smaller pretransplant liver volume than did nontransplant patients (p < 0.04). CONCLUSION: Hepatoportal sclerosis is characterized by caudate lobe hypertrophy and right hepatic lobe atrophy, preserved liver volume, and lack of the liver nodularity associated with portal hypertension. In advanced cases, liver nodularity and atrophy produce an imaging appearance indistinguishable from that of cirrhosis.

Multi-Center Follow-up Study to Develop a Classification System Which Differentiates Mucinous Cystic Neoplasm of the Liver and Benign Hepatic Cyst Using Machine Learning.

RATIONALE AND OBJECTIVES: To date, no clinically useful classification system has been developed for reliably differentiating mucinous cystic neoplasm (MCN) from a benign hepatic cyst (BHC) in the liver. The objective was to use machine learning and a multi-center study design to develop and assess the performance of a novel classification system for predicting whether a hepatic cystic lesion represents MCN or BHC. MATERIALS AND METHODS: A multi-center cohort study identified 154 surgically resected hepatic cystic lesions in 154 subjects which were pathologic confirmed as MCN (43) or BHC (111). Readers at each institution recorded seven pre-determined imaging features previously identified as potential differentiating features from prior publications. The contribution of each of these features to differentiating MCN from BHC was assessed by machine learning to develop an optimal classification system. RESULTS: Although several of the assessed imaging features demonstrated statistical significance, only 3 imaging features were found by machine learning to significantly contribute to a potential classification system: (1) solid enhancing nodule (2) all septations arising from an external macro-lobulation (3) whether the lesion was solitary or one of multiple cystic liver lesions. The optimal classification system had only four categories and correctly identified 144/154 lesion (93.5%). CONCLUSION: This multi-center follow-up study was able to use machine learning to develop a highly accurate classification system for differentiation of hepatic MCN from BHC, which could be readily applied to clinical practice.

Adult polyglucosan body disease: a rare presentation with chronic liver disease and ground-glass hepatocellular inclusions.

Liver involvement in genetic and metabolic disorders may result in intrahepatic accumulation of specific precursors or byproducts, which have distinctive features on light microscopy. The "polyglucosan disorders" are diseases in which polyglucosan (abnormal glycogen with decreased branching) is formed and deposited in various tissues because of decreased or absent glycogen branching enzyme activity. These disorders include Lafora disease (myoclonus epilepsy) and type IV glycogen storage disease. Polyglucosan deposits in both conditions result in ground-glass hepatocellular inclusions resembling those seen in chronic hepatitis B virus infection. In the present report, we describe a case of the rare, adulthood form of glycogen branching enzyme deficiency, adult polyglucosan body disease (APBD), in which abnormal serum liver tests prompted a liver biopsy. The pathologic findings of periportal ground-glass hepatocellular inclusions, mild chronic portal inflammation, and periportal fibrosis are not well described in APBD, but resemble the chronic changes that have been reported in Lafora disease. The differential diagnosis of ground-glass hepatocytes and the genetic basis of APBD are discussed.

Microvascular invasion in hepatocellular carcinoma: is it predictable with pretransplant MRI?

OBJECTIVE: The purpose of this article is to correlate clinicopathologic and MRI parameters with the presence of microvascular invasion at histopathologic examination in patients with hepatocellular carcinoma (HCC) who are undergoing liver transplantation. MATERIALS AND METHODS: In this retrospective single-center study, we assessed 60 patients (47 men and 13 women; mean age, 58 years) with HCC who underwent liver transplantation and pretransplant MRI (performed within 90 days before liver transplantation). Two observers analyzed the following tumor parameters in consensus: number, size, T1 and T2 signal intensity, margins, presence of capsule or pseudocapsule, distance to closest vessel, distance to liver capsule, and quantitative tumor enhancement. The size and number of HCCs, tumor differentiation, and the presence or absence of microvascular invasion were determined at histopathologic examination. Odds ratios (ORs) were calculated and logistic regression analysis was performed to assess the utility of these clinicopathologic and imaging parameters for predicting microvascular invasion. RESULTS: None of the clinical parameters or morphologic and enhancement MRI features of HCC was predictive of microvascular invasion. Tumor multifocality, on both MRI and pathologic examination, was the only variable that predicted microvascular invasion (OR = 2.43 and p = 0.013 for MRI; OR = 1.94 and p = 0.013 for pathologic examination). The presence of three or more tumors on MRI and four or more tumors at pathologic examination had high specificity (88.2% and 91.2%, respectively) for the prediction of microvascular invasion. CONCLUSION: Tumor multifocality on MRI was the only parameter that correlated significantly with microvascular invasion. All other MRI tumor characteristics failed to predict microvascular invasion.

Hepatocellular carcinoma: assessment of response to transarterial chemoembolization with image subtraction.

PURPOSE: To assess the diagnostic accuracy of image subtraction compared with nonsubtracted images obtained with contrast-enhanced T1-weighted imaging (CE T1WI) for the diagnosis of hepatocellular carcinoma (HCC) necrosis after transarterial chemoembolization (TACE), using liver explant as the reference standard. MATERIALS AND METHODS: Thirty-four patients who underwent TACE within 90 days of liver transplantation and CE MRI scans were assessed by two independent observers who determined the percentage of tumor necrosis using nonsubtracted and subtracted postcontrast phases. Histopathologic percentage of necrosis was retrospectively determined by an experienced pathologist. Spearman rank correlation test was used to correlate the percentages of necrosis from MR evaluation and from pathology. Receiver operating characteristics curve analysis was performed to determine the performance of subtracted versus nonsubtracted datasets for the diagnosis of complete tumor necrosis. RESULTS: There were 57 HCCs (mean size, 2.4 cm; range, 1.2-4.2 cm) diagnosed at explant and identified on MRI, including 16 completely necrotic HCCs. Subtraction demonstrated better interobserver agreement than nonsubtraction dataset for the diagnosis of tumor necrosis. There was a strong correlation between image subtraction and histopathologic assessment of necrosis (r = 0.80-0.86, depending on the phase, P < 0.0001). Subtraction demonstrated significantly higher sensitivity and accuracy for the diagnosis of complete tumor necrosis compared with nonsubtracted dataset. CONCLUSION: Image subtraction enables accurate assessment of necrosis of HCC after TACE with the best accuracy observed at the arterial phase.

Diagnosis of liver fibrosis and cirrhosis with diffusion-weighted imaging: value of normalized apparent diffusion coefficient using the spleen as reference organ.

OBJECTIVE: The purpose of this study is to compare the diagnostic accuracy of liver apparent diffusion coefficient (ADC) versus normalized liver ADC using the spleen as a reference organ for the diagnosis of liver fibrosis and cirrhosis. MATERIALS AND METHODS: Fifty-six patients, 34 with liver disease and 22 control subjects, were assessed with breath-hold single-shot echo-planar diffusion-weighted imaging using b values of 0, 50, and 500 s/mm(2). Liver ADC and normalized liver ADC (defined as the ratio of liver ADC to spleen ADC) were compared between patients stratified by fibrosis stage. Receiver operating characteristic (ROC) analysis was used to determine the performance of ADC and normalized liver ADC for prediction of liver fibrosis and cirrhosis. Reproducibility was assessed by measuring coefficient of variation (n = 7). RESULTS: Liver ADC failed to distinguish individual stages of fibrosis, except between stages 0 and 4. There were significant differences in normalized liver ADC between control livers and intermediate stages of fibrosis (stages 2-3) and cirrhosis (stage 4) and between stages 1 and 4, and there was a trend toward significance between stages 0 and 1 (p = 0.051) and stages 1 and 3 (p = 0.06). ROC analysis showed that normalized liver ADC was superior to liver ADC for detection of stage > or = 2 (area under the ROC curve, 0.864 vs 0.655; p = 0.013) and stage > or =3 (0.805 vs 0.689; p = 0.015), without a difference for diagnosing cirrhosis (0.935 vs 0.720; p = 0.185). Normalized liver ADC had higher reproducibility than ADC (mean coefficient of variation, 3.5% vs 12.6%). CONCLUSION: Our results suggest that normalizing liver ADC with spleen ADC improves diagnostic accuracy for detection of liver fibrosis and cirrhosis when using breath-hold diffusion-weighted imaging, with better reproducibility.

Quantification of hepatic iron deposition in patients with liver disease: comparison of chemical shift imaging with single-echo T2*-weighted imaging.

OBJECTIVE: The purpose of this study was to determine the diagnostic performance of chemical shift imaging, compared with that of single-echo T2*-weighted imaging, for hepatic iron quantification in patients with liver disease, and to examine the confounding effect of steatosis. MATERIALS AND METHODS: Sixty-three patients who underwent liver MRI and who had concomitant liver histopathologic analysis were retrospectively assessed. Chemical shift imaging and T2*-weighted imaging (n = 49) of the liver were reviewed by two independent observers. An iron index for each sequence (I(Fe-CSI) and I(Fe-T2*), respectively) was correlated with pathologic iron grade (0-4). Receiver operating characteristic curve analysis was performed to assess the accuracy of both sequences for the diagnosis of iron deposition (grades >or= 1, >or= 2, and >or= 3), and the impact of steatosis on accuracy was evaluated. RESULTS: Forty-seven (74.6%) patients had hepatic siderosis. There was a significant correlation between both I(Fe-CSI) and I(Fe-T2*) with pathologic iron grade (r = 0.65 and -0.61, respectively; p < 0.0001 for both). I(Fe-CSI) and I(Fe-T2*) were significantly higher or lower in iron grades 2-4 versus grades 0-1 and in grades 3-4 versus grades 0-2 (p < 0.001). Area under the curve values for detecting iron grade >or= 1, >or= 2, and >or= 3 were 0.75, 0.88, and 0.90 for I(Fe-CSI) and 0.72, 0.81, and 0.98 for I(Fe-T2*). Accuracy was lower for both sequences in steatotic patients for detection of iron grades >or= 1 and >or= 2, without reaching significance. CONCLUSION: Routine chemical shift imaging and single-echo T2*-weighted imaging have excellent diagnostic performance for detection of significant hepatic siderosis (grade >or= 2). Concomitant steatosis lowers the diagnostic performance of both sequences without reaching significance.

Author Correction: Integrating microarray-based spatial transcriptomics and single-cell RNA-seq reveals tissue architecture in pancreatic ductal adenocarcinomas.

A Correction to this paper has been published: https://doi.org/10.1038/s41587-019-0392-8.

Integrating microarray-based spatial transcriptomics and single-cell RNA-seq reveals tissue architecture in pancreatic ductal adenocarcinomas.

Single-cell RNA sequencing (scRNA-seq) enables the systematic identification of cell populations in a tissue, but characterizing their spatial organization remains challenging. We combine a microarray-based spatial transcriptomics method that reveals spatial patterns of gene expression using an array of spots, each capturing the transcriptomes of multiple adjacent cells, with scRNA-Seq generated from the same sample. To annotate the precise cellular composition of distinct tissue regions, we introduce a method for multimodal intersection analysis. Applying multimodal intersection analysis to primary pancreatic tumors, we find that subpopulations of ductal cells, macrophages, dendritic cells and cancer cells have spatially restricted enrichments, as well as distinct coenrichments with other cell types. Furthermore, we identify colocalization of inflammatory fibroblasts and cancer cells expressing a stress-response gene module. Our approach for mapping the architecture of scRNA-seq-defined subpopulations can be applied to reveal the interactions inherent to complex tissues.

Differentiating pancreatic cystic neoplasms from pancreatic pseudocysts at MR imaging: value of perceived internal debris.

PURPOSE: To retrospectively evaluate the sensitivity and specificity of several morphologic findings that may be seen with cystic pancreatic lesions, in the diagnosis of pseudocyst at magnetic resonance (MR) imaging. MATERIALS AND METHODS: This study was institutional review board approved and HIPAA compliant. From January 1, 2005, to December 31, 2007, electronic radiology and pathology databases were searched to identify patients with pancreatic cystic neoplasms or pseudocysts who underwent pancreatic MR imaging. Twenty-two patients with cystic pancreatic neoplasms that were confirmed at surgical resection (n = 12) or endoscopic ultrasonography (US) with cystic fluid analysis (n = 10) were identified. Of 20 patients with pancreatic pseudocysts, seven had pseudocysts that were identified at pathologic resection and 13 had a clinical history of pancreatitis, with initial computed tomography (CT) revealing no pancreatic cyst and subsequent follow-up MR imaging depicting cystic lesions. Two abdominal radiologists independently and randomly evaluated each case for presence or absence of septa and internal dependent debris and for external cyst morphology on axial and coronal T2-weighted images and three-dimensional gradient-echo T1-weighted images obtained before and after intravenous contrast agent administration. Logistic regression for correlated data was used to assess the usefulness of internal debris, external morphology, and septa for differentiating cystic neoplasms from pseudocysts. RESULTS: The readers' assessments of the presence or absence of cystic debris were concordant for 40 (95%) of the 42 patients, with a kappa coefficient of 0.889, which indicated nearly perfect agreement. Thirteen (93%) of 14 lesions found to have debris by either or both readers were pseudocysts, and only one (4%) of the 22 cystic neoplasms had debris. Both readers were more likely to identify septa within cystic neoplasms than within pseudocysts; however, the difference was not significant for either reader. The readers were more likely to observe microlobulated morphology in cystic neoplasms than in pseudocysts, with the difference between these lesion types, in terms of prevalence of microlobulated morphology, exhibiting a trend toward-but not reaching-statistical significance (P = .0627). CONCLUSION: Presence of internal dependent debris appears to be a highly specific MR finding for the diagnosis of pancreatic pseudocyst.