CT-determined resectability of borderline resectable and unresectable pancreatic adenocarcinoma following FOLFIRINOX therapy.

OBJECTIVES: We aimed to assess the ability of CT-determined resectability, as defined by a recent version of NCCN criteria, and associated CT findings to predict margin-negative (R0) resection in patients with PDAC after neoadjuvant FOLFIRINOX chemotherapy. METHODS: Sixty-four patients (36 men and 28 women; mean age, 58.8 years) with borderline resectable or unresectable PDAC who received neoadjuvant FOLFIRINOX were evaluated retrospectively. CT findings were independently assessed by two abdominal radiologists according to NCCN criteria (version 3. 2019). Tumor resectability was classified as resectable, borderline resectable, or unresectable, and change in resectability was classified as regression, stability, or progression. The associations of R0 resection rate with CT-determined resectability and change in resectability categories were evaluated, as were the sensitivity and specificity of NCCN criteria for R0 resection. Factors associated with R0 resection were identified by logistic regression analysis. RESULTS: R0 resection rate did not differ significantly among the resectable, borderline resectable, or unresectable PDAC (67-73%, p = 0.95) or among PDAC with regression, stability, or progression (56-77%, p = 0.39). The sensitivity and specificity for R0 resection were 67% and 37%, respectively, for resectability (resectable/borderline vs. unresectable) and 80% and 21%, respectively, for changes in resectability (regression/stable vs. progression). Low-contrast enhancement of soft tissue contacting artery (≤ 46.4 HU) was independently associated with R0 resection (p = 0.01). CONCLUSION: CT-determined resectability after neoadjuvant FOLFIRINOX chemotherapy was relatively insensitive and non-specific for predicting R0 resection. Low-contrast enhancement of soft tissue contacting artery may increase the ability of CT to predict R0 resection. KEY POINTS: • Margin-negative resection rate of pancreatic cancer following FOLFIRINOX therapy did not differ among each resectability (67-73%, p = 0.95) based on NCCN criteria or changes in resectability categories (56-77%, p = 0.39). • The sensitivity and specificity for margin-negative resection were 67% and 37% for resectability (resectable/borderline vs. unresectable) and 80% and 21% for changes in resectability (regression/stable vs. progression). • Low-contrast enhancement of soft tissue contacting artery (≤ 46.4 HU) was independently associated with margin-negative resection (p = 0.01).

Value of apparent diffusion coefficient for differentiating peripancreatic tuberculous lymphadenopathy from metastatic lymphadenopathy.

PURPOSE: To evaluate effectiveness of the apparent diffusion coefficient (ADC) values of the peripancreatic lymphadenopathy to differentiate tuberculous lymphadenopathy from metastatic lymphadenopathy. MATERIALS AND METHODS: Twenty-nine patients with 65 peripancreatic necrotic tuberculous lymphadenopathy and 31 patients with 47 peripancreatic necrotic metastatic lymphadenopathy from pancreatic ductal adenocarcinoma, who underwent magnetic resonance imaging (MRI), were included in this study. MRI features in the T1-weighted image (WI), T2WI, and diffusion-weighted image were analyzed. The ADC values of necrotic and non-necrotic portions of the lymph nodes were measured and compared using t test. Receiver operating characteristic analysis was performed to obtain the optimal ADC threshold value and diagnostic accuracy for differentiating tuberculous lymphadenopathy from metastatic lymphadenopathy. RESULTS: On T2WI, the signal intensity of necrotic portions was variable in tuberculous lymphadenopathy, but was mostly high in metastatic lymphadenopathy. The mean ADCs of necrotic portions of tuberculous lymphadenopathy were significantly lower than those of metastatic lymphadenopathy ([0.919 ± 0.272] × 10-3 mm2/s vs. [1.553 ± 0.406] × 10-3 mm2/s, p < 0.001). Receiver operating characteristic analysis for differentiating tuberculous from metastatic lymphadenopathy demonstrated an area under the curve for the ADC values of necrotic portions of 0.929 (95% CI, 0.865-0.969) with an ADC threshold of 1.022. The sensitivity and specificity for the differentiation of tuberculous from metastatic lymphadenopathy were 80.0% and 97.8%, respectively. CONCLUSION: The ADC values of necrotic portions of peripancreatic lymphadenopathy may be useful for differentiating tuberculous from metastatic lymphadenopathy.

Feasibility of non-enhanced CT for assessing longitudinal changes in hepatic steatosis.

To evaluate the feasibility of computed tomography (CT) in the assessment of the change in hepatic steatosis (HS) in longitudinal follow-up by employing pathological HS as the reference standard.We retrospectively evaluated 38 living liver donor candidates (27 men and 11 women; mean age, 29.5 years) who underwent liver biopsy twice and had liver CT scans within 1 week of each biopsy. Four readers independently calculated CTL-S index by subtracting spleen attenuation from liver attenuation on non-enhanced CT images. The changes in pathological HS (ΔHS) and CTL-S (ΔCTL-S) between the 1st and 2nd examinations were assessed. The correlation between ΔHS and ΔCTL-S was assessed using the linear regression analysis. Inter-observer measurement error for ΔCTL-S among the 4 readers was assessed using the repeatability coefficient.ΔCTL-S showed a significant correlation with ΔHS in all readers (r = 0.571-0.65, P < .001). The inter-observer measurement error for ΔCTL-S was ±8.9. The ΔCTL-S values beyond the measurement error were associated with a consistent change in HS in 83.3% (13/15) to 100% (15/15), with sensitivities of 47.8 to 79.9% and specificities of 86.7 to 100% for detecting an absolute change of ≥10% in HS among the 4 readers. However, ΔCTL-S values within the measurement error were associated with a consistent change in HS in 43.5% (8/19) to 61.5% (16/26).The change in CTL-S roughly reflects the change in HS during longitudinal follow-up. A small change in CTL-S should not be considered meaningful, while a larger change in CTL-S beyond the measurement error strongly indicates a true change in HS.

Differentiating focal autoimmune pancreatitis and pancreatic ductal adenocarcinoma: contrast-enhanced MRI with special emphasis on the arterial phase.

OBJECTIVES: To compare focal-type autoimmune pancreatitis (AIP) and pancreatic ductal adenocarcinoma (PDA) using contrast-enhanced MR imaging (CE-MRI), and to assess diagnostic performance of the lesion contrast at arterial phase (AP) (ContrastAP) for differentiating between the two diseases. METHODS: Thirty-six patients with focal-type AIP and 72 patients with PDA were included. All included patients underwent CE-MRI with triple phases. The signal intensity (SI) of the mass and normal pancreas was measured at each phase, and the lesion contrast (SIpancreas/SImass) was compared between AIP and PDA groups. The sensitivity and specificity of ContrastAP using an optimal cutoff point were compared with those of key imaging features specific to AIP and PDA. RESULTS: The lesion contrast differed significantly between AIP and PDA groups at all phases of CE-MRI; the maximum difference was observed at AP. For AIP, the sensitivity (94.4%) and specificity (87.5%) of ContrastAP (cutoff ≤ 1.41) were comparable or significantly higher than those of all key imaging features (sensitivity, 38.9-88.9%; specificity, 48.6-95.8%), except for the halo sign. For PDA, the sensitivity (87.5%) and specificity (94.4%) of ContrastAP (cutoff > 1.41) were comparable or significantly higher than those of all key imaging features (sensitivity, 40.3-68.1%; specificity, 72.2-94.4%), except for the discrete mass. CONCLUSIONS: Quantitative analysis of the lesion contrast using CE-MRI, particularly at AP, was helpful to differentiate focal-type AIP from PDA. The diagnostic performance of ContrastAP was mostly comparable or higher than those of the key imaging features. KEY POINTS: • Diagnosis of focal-type AIP vs. PDA using imaging techniques is extremely challenging. • Lesion contrast in the arterial-phase MRI differs significantly between focal-type AIP and PDA. • Quantitative analysis of lesion contrast using CE-MRI, particularly at the arterial phase, is helpful to differentiate focal-type AIP from PDA.

Diagnostic performance of [18F]FDG-PET/MRI for liver metastasis in patients with primary malignancy: a systematic review and meta-analysis.

OBJECTIVES: To systematically determine the diagnostic accuracy of 18-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging ([18F]FDG-PET/MRI) for the detection of liver metastases and evaluate the sources of heterogeneity in the reported results. METHODS: PubMed and EMBASE databases were searched up until December 31, 2017, to identify original research studies reporting the diagnostic performance (Se and Sp) of PET/MRI for liver metastases, in comparison with PET/CT. Study quality was assessed using QUADAS-2. The summary Se and Sp of the studies were estimated using hierarchical modeling methods. To determine causes of study heterogeneity, the presence of a threshold effect was analyzed, and meta-regression analysis was performed. RESULTS: Of 546 articles screened, eight suitable articles were identified, with seven for per-lesion analysis, and four for per-patient analysis. The meta-analytic summary Se and Sp for per-patient-based analysis were 99.2% (95% CI, 31.4-100.0%, I2 = 89.4%) and 98.6% (95% CI, 84.0-99.9%, I2 = 0.0%), respectively, while for per-lesion-based analysis they were 95.4% (95% CI, 78.3-99.2%, I2 = 99.7%) and 99.3% (95% CI, 93.8-99.9%, I2 = 96.5%). PET/MRI showed higher Se (95.4% vs. 68.3%) and Sp (99.3% vs. 95.8%) than PET/CT. Meta-regression analysis showed five significant factors affecting study heterogeneity: study subject characteristics, study design, MRI technique (DWI, HBP after injection of liver-specific contrast media), imaging review method, and reference standard. CONCLUSION: The diagnostic accuracy of [18F]FDG-PET/MRI for liver metastasis was high overall, but substantial heterogeneity was found. Further randomized controlled studies or prospective studies are needed to investigate the role of PET/MRI in liver metastasis in comparison with PET/CT. KEY POINTS: • [ 18 F]FDG-PET/MRI has high meta-analytic Se and Sp for the diagnosis of liver metastasis. • PET/MRI using DWI and HBP images significantly increased diagnostic accuracy. • Study heterogeneity was associated with subject characteristics, study design, MRI technique, image review method, and reference standard.

Radiomics Analysis of Gadoxetic Acid-enhanced MRI for Staging Liver Fibrosis.

Purpose To develop and validate a radiomics-based model for staging liver fibrosis by using gadoxetic acid-enhanced hepatobiliary phase MRI. Materials and Methods In this retrospective study, 436 patients (mean age, 51 years; age range, 18-86 years; 319 men [mean age, 51 years; age range, 18-86 years]; 117 women [mean age, 50 years; age range, 18-79 years]) with pathologic analysis-proven liver fibrosis who underwent gadoxetic acid-enhanced MRI from June 2015 to December 2016 were randomized in a three-to-one ratio into development (n = 329) and test (n = 107) cohorts, respectively. In the development cohort, a model was developed to calculate radiomics fibrosis index (RFI) by using logistic regression with elastic net regularization to differentiate stage F3-F4 from stage F0-F2. Optimal RFI cutoffs to diagnose clinically significant fibrosis (stage F2-F4), advanced fibrosis (stage F3-F4), and cirrhosis (stage F4) were determined by receiver operating characteristic curve analysis. In the test cohort, the diagnostic performance of RFI was compared with that of normalized liver enhancement, aspartate transaminase-to-platelet ratio index (APRI), and fibrosis-4 index by using the Obuchowski index. Results In the test cohort, RFI (Obuchowski index, 0.86) significantly outperformed normalized liver enhancement (Obuchowski index, 0.77; P < .03), APRI (Obuchowski index, 0.60; P < .001), and fibrosis-4 index (Obuchowski index, 0.62; P < .001) for staging liver fibrosis. By using the cutoffs, RFI had sensitivities and specificities as follows: 81% (95% confidence interval: 71%, 89%) and 78% (95% confidence interval: 63%, 89%) for diagnosing stage F2-F4, respectively; 79% (95% confidence interval: 67%, 88%) and 82% (95% confidence interval: 69%, 91%), respectively, for diagnosing stage F3-F4; and 92% (95% confidence interval: 79%, 98%) and 75% (95% confidence interval: 62%, 83%), respectively, for diagnosing stage F4. Conclusion Radiomics analysis of gadoxetic acid-enhanced hepatobiliary phase images allows for accurate diagnosis of liver fibrosis. © RSNA, 2018 Online supplemental material is available for this article.

CT indices for the diagnosis of hepatic steatosis using non-enhanced CT images: development and validation of diagnostic cut-off values in a large cohort with pathological reference standard.

OBJECTIVES: To compare the performances of CT indices for diagnosing hepatic steatosis (HS) and to determine and validate the CT index cut-off values. METHODS: Three indices were measured on non-enhanced CT images of 4413 living liver donor candidates (2939 men, 1474 women; mean age, 31.4 years): hepatic attenuation (CTL), hepatic attenuation minus splenic attenuation (CTL-S), and hepatic attenuation divided by splenic attenuation (CTL/S). The performances of these CT indices in diagnosing HS, relative to pathologic diagnosis, were compared in the development cohort of 3312 subjects by receiver operating characteristic (ROC) analysis. The cut-off values for diagnosing HS > 33% in the development cohort were determined at 95% specificity and 95% sensitivity using bootstrap ROC analysis, and the diagnostic performance of these cut-off values was validated in the test cohort of 1101 subjects. RESULTS: CTL-S showed the highest performance for diagnosing HS ≥ 5% and HS > 33% (areas under the curve (AUCs) = 0.737 and 0.926, respectively), followed by CTL/S (AUCs = 0.732 and 0.925, respectively) and CTL (AUCs = 0.707 and 0.880, respectively). For CT scans using 120 kVp, the CTL-S cut-off values for highly specific (i.e., - 2.1) and highly sensitive (i.e., 7.6) diagnosis of HS > 33% resulted in a specificity of 96.4% with a sensitivity of 64.0% and a sensitivity of 97.3% with a specificity of 54.9%, respectively, in the test cohort. CONCLUSION: CT indices using liver and spleen attenuations have higher performance for diagnosing HS than indices using liver attenuation alone. The CTL-S cut-off values in this study may have utility for diagnosing HS in clinical practice and research. KEY POINTS: • CT indices based on both liver attenuation and spleen attenuation (CTL-Sand CTL/S) have higher diagnostic performance than CTLbased on liver attenuation alone in diagnosing HS using various CT techniques. • The CT index cut-off values determined in this study can be utilized for reliable diagnosis or to rule out subjects with moderate to severe HS in clinical practice and research, including the selection of living liver donors and the development of cohorts with HS or healthy controls.

LI-RADS Classification and Prognosis of Primary Liver Cancers at Gadoxetic Acid-enhanced MRI.

Purpose To (a) evaluate the postsurgical prognostic implication of the Liver Imaging Reporting and Data System (LI-RADS) categories of primary liver cancers and (b) determine the performance of LI-RADS version 2017 in differentiating hepatocellular carcinoma (HCC) from intrahepatic cholangiocarcinoma (IHCC) and combined hepatocellular-cholangiocarcinoma (cHCC-CC) at gadoxetic acid-enhanced MRI. Materials and Methods In this retrospective study, 194 patients with cirrhosis and surgically proven single primary liver cancer (53 with cHCC-CC, 44 with IHCC, and 97 with HCC) were evaluated with gadoxetic acid-enhanced MRI between 2009 and 2014. The mean patient age was 57 years (age range, 30-83 years). There were 155 men with a mean age of 56 years (range, 30-81 years) and 39 women with a mean age of 58 years (range, 38-83 years). Two independent readers assigned an LI-RADS category for each nodule. Overall survival (OS), recurrence-free survival (RFS), and their associated factors were evaluated by using the Kaplan-Meier method, log-rank test, and Cox proportional hazard model. Results In the multivariable analysis, the LI-RADS category was an independent factor for OS (hazard ratio, 4.2; P < .001) and RFS (hazard ratio, 2.6; P = .01). The LR-M category showed more correlation with poorer OS and RFS than did the LR-4 or LR-5 category for all primary liver cancers (P < .001 for both), HCCs (P = .01 and P < .001, respectively), and cHCC-CCs (P = .01 and P = .03, respectively). The LR-5 category had a sensitivity of 69% (67 of 97) and a specificity of 87% (84 of 97) in the diagnosis of HCC; most false-positive diagnoses (85%, 11 of 13) were the result of misclassification of cHCC-CCs. Conclusion The Liver Imaging Reporting and Data System (LI-RADS) category was associated with postsurgical prognosis of primary liver cancers, independent of pathologic diagnosis. The LI-RADS enabled the correct classification of most hepatocellular carcinomas (HCCs) and intrahepatic cholangiocarcinomas, whereas differentiation of combined hepatocellular-cholangiocarcinoma from HCC was unreliable. © RSNA, 2018 Online supplemental material is available for this article. See also the editorial by Bashir and Chernyak in this issue.

Comparison of diagnostic performance between CT and MRI in differentiating non-diffuse-type autoimmune pancreatitis from pancreatic ductal adenocarcinoma.

OBJECTIVES: To intraindividually compare the diagnostic performance of CT and MRI in differentiating non-diffuse-type autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDA). METHODS: Sixty-one patients with non-diffuse-type AIP and 122 patients with PDA, who underwent dynamic contrast-enhanced CT and MRI with MR pancreatography, were included. Two blinded radiologists independently rated their confidence in differentiating the two diseases on a 5-point scale, and the diagnostic performances of CT and MRI were compared. The presence of key imaging features to differentiate AIP and PDA were compared between CT and MRI. RESULTS: The area under the receiver operating characteristic curve was significantly greater on MRI (0.993-0.995) than on CT (0.953-0.976) for both raters (p≤0.035). The sensitivities of MRI were higher than those of CT for the diagnosis of AIP (88.5-90.2% vs. 77-80.3%, p≤0.07) and PDA (97.5-99.2% vs. 91.8-94.3%, p≤0.031) for both raters, although the difference for AIP was statistically marginal (p=0.07) for rater 1. In AIP, multiple pancreatic masses, delayed homogeneous enhancement of the pancreatic mass, and multiple main pancreatic duct (MPD) strictures were observed significantly more frequently using MRI than CT (p≤0.008). In PDA, discrete pancreatic mass and MPD stricture were observed significantly more frequently using MRI than CT (p≤0.012). CONCLUSIONS: The diagnostic performance of MRI is better for differentiating non-diffuse-type AIP from PDA, which is due to the superiority of MRI over CT in demonstrating the key distinguishing features of both diseases. KEY POINTS: • Imaging differential diagnosis of non-diffuse-type AIP and PDA is challenging. • MRI has better diagnostic performance than CT in differentiating non-diffuse-type AIP from PDA. • MRI is superior to CT in demonstrating key distinguishing features of non-diffuse-type AIP and PDA.

Imaging and clinical features of xanthogranulomatous pancreatitis: an analysis of 10 cases at a single institution.

PURPOSE: The purpose of the study was to investigate the imaging and clinical features of xanthogranulomatous pancreatitis (XGP). METHODS: This retrospective series study included 10 patients with pathology-proven XGP. Two radiologists reviewed the computed tomography (CT) and magnetic resonance imaging (MRI) in consensus to determine the morphological features of XGP. The lesion enhancement pattern on dynamic contrast-enhanced scans and the MR signal intensity were also evaluated. Clinical data including symptoms, underlying pancreatic disease, and laboratory findings were reviewed. RESULTS: Two XGP cases were of a solid type; six were of cystic type, and two were mixed type. XGP usually showed a lobulated contour (90%) and heterogeneous enhancement (100%), with lesion size varying from 2 to 11 cm. Perilesional infiltration was common (90%), but pancreatic duct dilatation was less frequent (30%). Cystic type XGP mostly had an irregular thick wall (83%). On dynamic contrast-enhanced CT/MRI, XGP enhanced progressively from arterial to portal or delayed phases. Lesions appeared hypointense on T1-weighted images (89%) and hyperintense on T2-weighted images (100%). All lesions appeared hyperintense on diffusion-weighted images, with the majority (78%) showing diffusion restriction on apparent diffusion coefficient maps. The patients often had abdominal pain (80%) and underlying pancreatic disease (80%), but mostly had normal or clinically insignificant laboratory findings. CONCLUSIONS: XGP typically manifests as a clinically silent lobulated heterogeneous mass, with a progressive enhancement pattern and/or irregular thick wall, and diffusion restriction on CT/MRI. Awareness of the imaging and clinical features of XGP may help differentiate it from pancreatic neoplasms, thereby reducing unnecessary surgery.

Intraductal Papillary Neoplasm of the Bile Duct: Clinical, Imaging, and Pathologic Features.

OBJECTIVE: We outline the concept of intraductal papillary neoplasm of the bile duct (IPNB), discuss the morphologic features of IPNB and the differential diagnoses, and describe the radiologic approaches used in multidisciplinary management. CONCLUSION: The concept of IPNB has been evolving. Because the imaging features of IPNB can be variable, different mimickers according to IPNB subtype can be considered. A multimodality approach is essential to obtain an optimal diagnosis and establish treatment plans.

Clinical impact of preoperative liver MRI in the evaluation of synchronous liver metastasis of colon cancer.

OBJECTIVES: To investigate whether additional MRI including gadoxetic acid enhancement is associated with survival rate (SR) in patients with synchronous liver metastasis of colon cancer (sCLM), compared with patients assessed only with CT. METHODS: Fifty-two patients underwent only CT (CT group) and 65 underwent additional MRI (CT+MRI group) for preoperative work-up of sCLM. In the CT+MRI group, the discrepancy between CT and MRI was analyzed. The 5-year SR was compared between the groups, and affecting factors were investigated. The inverse probability treatment weighting analysis (IPTW) adjusted by propensity scores was performed. RESULTS: In the CT+MRI group, 44 (67.7%) showed a discrepancy in the number of sCLMs between CT and MRI. MRI detected 39 additional sCLMs initially missed on CT in 26 patients. The number of detected sCLMs was better correlated with the pathologic findings in the CT+MRI group than in the CT group (p = 0.008). The estimated 5-year SR in the CT+MRI group was 70.8%, while that in the CT group was 48.1%. On adjusted multivariate analyses after the IPTW, the CT+MRI group showed a significantly lower risk of overall mortality than the CT group. CONCLUSION: Additional preoperative evaluation by MRI allowed us to more precisely detect sCLM and was associated with a better SR. KEY POINTS: • CT+MRI group showed significantly higher 5-year survival rates than CT group. • CT+MRI group was an independent prognostic factor of overall mortality. • MRI facilitates more accurate detection and better lesion characterization. • MRI selected better candidates for curative treatment. • The benefits of MRI were reflected by better survival.

Diagnostic performance of CT, gadoxetate disodium-enhanced MRI, and PET/CT for the diagnosis of colorectal liver metastasis: Systematic review and meta-analysis.

BACKGROUND: Imaging studies, including computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET), have an essential role in the detection and localization of colorectal liver metastasis (CRLM). PURPOSE: To systematically determine the diagnostic accuracy of multidetector row CT (MDCT), gadoxetate disodium-enhanced MRI, and PET/CT for diagnosing CRLM and the sources of heterogeneity between the reported results. STUDY TYPE: Systematic review and meta-analysis. SUBJECTS: In all, 2151 lesions in CT studies, 2301 lesions in MRI studies, 1846 lesions in PET/CT studies, FIELD STRENGTH: 1.5T and 3.0T. ASSESSMENT: We identified research studies that investigated MDCT, gadoxetate disodium-enhanced MRI, and PET/CT to diagnose CRLM by performing a systematic search of PubMed MEDLINE and EMBASE. Study quality was assessed using Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2). STATISTICAL TESTS: According to the types of imaging tests, study heterogeneity and the threshold effect were analyzed and the meta-analytic summary of sensitivity and specificity were estimated. Meta-regression analysis was performed to further investigate study heterogeneity. RESULTS: Of the 860 articles screened, we found 36 studies from 24 articles reporting a diagnosis of CRLM (11 CT studies, 12 MRI studies, and 13 PET/CT studies). The meta-analytic summary sensitivity for CT, MRI, and PET/CT were 82.1% (95% confidence interval [CI], 74.0-88.1%), 93.1% (95% CI, 88.4-96.0%), and 74.1% (95% CI, 62.1-83.3%), respectively. The meta-analytic summary specificity for CT, MRI, and PET/CT were 73.5% (95% CI, 53.7-86.9%), 87.3% (95% CI, 77.5-93.2%), and 93.9% (95% CI, 83.9-97.8%), respectively. There was no threshold effect in any of the imaging tests. Neoadjuvant chemotherapy significantly decreased the sensitivity of CT and MRI (P < 0.01), although it did not significantly affect the sensitivity of PET/CT. The study design, type of reference standard, and study quality also affected the diagnostic performances of imaging studies. DATA CONCLUSION: Despite the heterogeneous accuracy between studies, gadoxetate disodium-enhanced MRI showed the highest sensitivity, and gadoxetate disodium-enhanced MRI and PET/CT had similar specificities for diagnosing CRLM. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1237-1250.

Pancreatic Duct in Autoimmune Pancreatitis: Intraindividual Comparison of Magnetic Resonance Pancreatography at 1.5 T and 3.0 T.

OBJECTIVE: The aim of this study was to intraindividually compare magnetic resonance pancreatography (MRP) image quality at 1.5 T and 3.0 T when demonstrating main pancreatic duct (MPD) abnormalities in patients with autoimmune pancreatitis (AIP). METHODS: Thirty prospectively enrolled patients with AIP underwent MRP at both 1.5 T and 3.0 T followed by endoscopic retrograde pancreatography before treatment. Two readers independently analyzed the MRP images and graded the visualization of MPD strictures and full-length MPD, using endoscopic retrograde pancreatography as the reference standard, as well as overall image artifacts on a 4-point scale. The contrast between the MPD and periductal area was calculated using a region-of-interest measurement. RESULTS: Visualization scores of MPD strictures and full-length MPD, and summed scores of each qualitative analysis, were significantly greater at 3.0-T MRP than at 1.5-T MRP for both readers (P ≤ 0.02). There were less image artifacts at 3.0 T compared with 1.5 T (P ≤ 0.052). The contrast between the MPD and periductal area was significantly greater at 3.0-T MRP than at 1.5-T MRP (P < 0.001). CONCLUSIONS: The MRP at 3.0 T was superior to 1.5-T MRP for demonstrating MPD abnormalities in AIP, with better image contrast and fewer image artifacts. Consequently, 3.0-T MRP may be useful for the diagnosis and management of patients with AIP.

Subtraction Images of Gadoxetic Acid-Enhanced MRI: Effect on the Diagnostic Performance for Focal Hepatic Lesions in Patients at Risk for Hepatocellular Carcinoma.

OBJECTIVE: The purpose of this study is to evaluate the effect of subtraction images of gadoxetic acid-enhanced MRI on the image interpretation of focal hepatic lesions in patients at risk for hepatocellular carcinoma (HCC). MATERIALS AND METHODS: We retrospectively analyzed 255 malignant nodules from 233 patients with chronic hepatitis or liver cirrhosis (187 men and 46 women; mean age, 55.2 years) who underwent preoperative gadoxetic acid-enhanced MRI and surgical resection. We compared the detection rate of arterial hypervascularity on visual assessment with that of subtraction images. Subgroup analysis was performed according to the pathologic profile of the lesion (HCC vs non-HCC), the lesion size (≤ 3 vs > 3 cm), and the MRI technique (1.5 vs 3 T). We assessed the effect of subtraction images in diagnosing HCC according to the American Association for the Study of Liver Diseases guidelines compared with that of visual assessment. RESULTS: After excluding six patients whose images were not of nondiagnostic quality, 249 nodules (215 HCCs, 27 cholangiocarcinomas, and seven combined HCC and cholangiocarcinomas) from 227 patients were analyzed. Subtraction images more sensitively detected the arterial hypervascularity of all of the hepatic lesions than did visual assessment (sensitivity, 89.2% vs 72.4%; p < 0.001). In all of the subgroup analyses, the same tendency was observed (p = 0.001-0.145). Compared with visual assessment only, arterial hypervascularity determined by both subtraction images and the visual enhancement patterns increased sensitivity from 76.5% to 87.5% (p < 0.001) in diagnosing HCCs, with a minimal decrease in specificity from 80.9% to 78.1% (p = 0.332). CONCLUSION: Adding subtraction images with consideration of visual enhancement patterns can enhance the sensitivity in diagnosing HCC by enhancing the detection of arterial hypervascularity.

Combined hepatocellular-cholangiocarcinoma: Gadoxetic acid-enhanced MRI findings correlated with pathologic features and prognosis.

PURPOSE: To evaluate gadoxetic acid-enhanced magnetic resonance imaging (MRI) findings of combined hepatocellular cholangiocarcinoma (cHCC-CC) with special emphasis on correlation of MRI findings with histopathologic tumor characteristics and survival outcomes after curative surgery. MATERIALS AND METHODS: Our Institutional Review Board approved this study, with a waiver of informed consent. For 82 patients (64 men, 18 women; mean age, 54.0 years; age range, 30-81) with surgically confirmed cHCC-CCs, we evaluated clinical features, histologic findings, and tumor morphologic and enhancement features on gadoxetic acid-enhanced liver MRI at 1.5T (n = 67) or 3.0T (n = 15). Imaging features of cHCC-CCs were correlated with pathologic findings according to the 2010 World Health Organization classification system. Tumors were categorized as hypervascular or nonhypervascular based on arterial phase enhancement and were compared with respect to overall and recurrence-free survival after curative-intent surgery. RESULTS: Of the 82 lesions, 48 showing global arterial phase enhancement were categorized as the hypervascular group, while 34 lesions demonstrating rim, peripheral, or isoenhancement were categorized as the nonhypervascular group. There was no significant difference in MRI findings between pathologic tumor types (classical type versus stem cell feature type, P = 0.324-1.0). Compared with the nonhypervascular group, the hypervascular group had a larger HCC component (P = 0.014), smaller CC component (P = 0.001), and lesser amount of fibrotic stroma (P = 0.006) on pathologic analysis and was an independent factor associated with better overall survival after surgical resection (P = 0.033). CONCLUSION: Gadoxetic acid-enhanced MRI findings of cHCC-CCs were diverse, reflecting heterogeneous histologic features. The hypervascular group on MRI is associated with a larger HCC component, smaller CC component, less fibrotic stroma, and better overall survival after curative surgery than the nonhypervascular group. LEVEL OF EVIDENCE: 4 J. MAGN. RESON. IMAGING 2017;46:267-280.

Intravoxel incoherent motion diffusion-weighted MRI of the abdomen: The effect of fitting algorithms on the accuracy and reliability of the parameters.

PURPOSE: To evaluate the influence of fitting methods on the accuracy and reliability of intravoxel incoherent motion (IVIM) parameters, with a particular emphasis on the constraint function. MATERIALS AND METHODS: Diffusion-weighted (DW) imaging data were analyzed using IVIM-based full-fitting (simultaneous fit of all parameters) and segmented-fitting (step-by-step fit of each parameter), each with and without the constraint function, to estimate the molecular diffusion coefficient (Dslow ), perfusion fraction (f), and flow-related diffusion coefficient (Dfast ). Computational simulations were performed at variable signal-to-noise ratios to evaluate the relative error (RE) and coefficient of variation (CV) of the estimated IVIM parameters. DW imaging of the abdomen was performed twice at 1.5 Tesla using nine b-values (0-900 s/mm2 ) in 12 health volunteers (6 men and 6 women; mean age: 30 years). The measurement repeatability of IVIM parameters in the liver and the pancreas was evaluated using the within-subject coefficient of variation (w CV). RESULTS: In simulations, full-fitting without the constraint function yielded the largest RE (P < 0.001 for Dslow and f; P ≤ 0.044 for Dfast ) and CV (P ≤ 0.033 for Dslow and f; P ≤ 0.473 for Dfast ) for IVIM parameters among all four algorithms. In volunteer imaging, full-fitting without the constraint function also resulted in the poorest repeatability for Dslow (w CV, 17.12%-65.45%) and f (w CV, 19.35%-42.84%) in the liver and pancreas, while the other algorithms had similar repeatability values (w CV, 4.05%-11.99% for Dslow and 9.65%-18.66% for f). Measurement repeatability of Dfast (w CV, 29.52%-85.01%) was the poorest among the IVIM parameters. CONCLUSION: For accurate and reliable measurement of IVIM parameters, segmented fitting or full-fitting with the constraint function should be used for IVIM-based analysis of DW imaging. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;45:1637-1647.

Intrahepatic Cholangiocarcinoma in Patients with Cirrhosis: Differentiation from Hepatocellular Carcinoma by Using Gadoxetic Acid-enhanced MR Imaging and Dynamic CT.

Purpose To determine the imaging features at gadoxetic acid-enhanced magnetic resonance (MR) imaging of intrahepatic cholangiocarcinoma (IHCC) in a cirrhotic liver, with an emphasis on the distinction between IHCC and hepatocellular carcinoma (HCC) and on the comparison of nodule enhancement patterns between MR imaging and computed tomography (CT). Materials and Methods The institutional review board approved this study and waived the requirement for informed consent. Gadoxetic acid-enhanced MR and CT images in 72 consecutive patients (61 men; mean age, 56.6 years) with 78 IHCCs and one-to-one matched control patients (56 men; mean age, 56.6 years) with 77 HCCs were evaluated retrospectively by two independent readers. Findings that could differentiate IHCC from HCC were evaluated with univariate and multivariate analyses. Using the enhancement criteria and the Liver Imaging Reporting and Data System with modifications (mLI-RADS), the sensitivity and specificity for diagnosing HCC were calculated with conventional washout and portal venous phase (PVP) washout. Results At MR imaging with conventional washout, the specificities for diagnosing HCC were 94.9% (74 of 78) with the enhancement criteria and 96.2% (75 of 78) with mLI-RADS, while the use of PVP washout achieved 100% (78 of 78) specificity for diagnosing HCC with both diagnostic criteria at the expense of decreased sensitivity (from 76.6% [59 of 77] to 63.6% [49 of 77] with the enhancement criteria and from 64.9% [50 of 77] to 55.8% [43 of 77] with mLI-RADS, P ≤ .016). At CT, the sensitivities and specificities with conventional washout were 72.7% (56 of 77) and 97.4% (76 of 78), respectively, with the enhancement criteria and 67.5% (52 of 77) and 97.4% (76 of 78), respectively, with mLI-RADS. Conclusion The use of PVP washout instead of conventional washout at gadoxetic acid-enhanced MR imaging prevents the misclassification of IHCC as HCC in a cirrhotic liver but leads to a decreased sensitivity for HCC. © RSNA, 2016 Online supplemental material is available for this article.