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To evaluate the ability of magnetic resonance imaging (MRI) to predict pathologic complete response (pCR) after neoadjuvant chemoradiation therapy (CRT) in patients with clinical T1/T2 rectal cancer to indicate candidates for organ-saving strategies.Between 2012 and 2016, 38 patients with clinical T1/T2 rectal cancer received neoadjuvant CRT. Radiologic complete response (rCR) was assigned when dense fibrotic tissue without tumor signal intensity was observed on post-CRT MRI. Surgical pathologic assessment was used to evaluate tumor regression. The association between rCR and the mural extent of the primary tumor, pCR, and pathologic T stage were analyzed.In rCR patients, the pCR rate was higher; the odds of achieving pCR were 8.00 times higher than for non-rCR patients (P = .02). rCR patients were also more likely to have early-stage cancer than non-rCR patients (P = 0.01). Patients with partial extent of the primary tumor on post-CRT MRI were more likely to be diagnosed with early-stage cancer than those with transmural extent (P = .01).rCR indicated by post-CRT MRI can be used as a supportive factor to predict pCR after neoadjuvant CRT in patients with clinical T1/T2 rectal cancer and can guide management decisions around organ-saving treatments.

Objective: To stratify the postsurgical computed tomography (CT) surveillance based on a risk-scoring system for predicting extragastric recurrence after surgical resection of early gastric cancer (EGC)., Summary of Background Data: Postsurgical CT surveillance should not be routinely performed in all patients because of the low incidence of extragastric recurrence and potential risk of radiation exposure., Methods: Data from 3162 patients who underwent surgical resection for EGC were reviewed to develop a risk-scoring system to predict extragastric recurrence. Risk scores were based on the predictive factors for extragastric recurrence, which were determined using Cox proportional hazard regression model. The risk-scoring system was validated by Uno censoring adjusted C-index. External validation was performed using an independent dataset (n = 430)., Results: The overall incidence of extragastric recurrence was 1.4% (44/3162). Five risk factors (lymph node metastasis, indications for endoscopic resection, male sex, positive lymphovascular invasion, and elevated macroscopic type), which were significantly associated with extragastric recurrence, were incorporated into the risk-scoring system, and the patients were categorized into 2 risk groups. The 10-year extragastric recurrence-free survival differed significantly between low- and high-risk groups (99.7% vs 96.5%; P < 0.001). The predictive accuracy of the risk-scoring system in the development cohort was 0.870 [Uno C-index; 95% confidence interval (95% CI), 0.800-0.939]. Discrimination was good after internal (0.859) and external validation (0.782, 0.549-1.000)., Conclusion: This risk-scoring system might be useful to predict extragastric recurrence of EGC after curative surgical resection. We suggest that postsurgical CT surveillance to detect extragastric recurrence should be avoided in the low-risk group.

Objective: Bowel angioedema is an acute adverse reaction to iodinated contrast media (CM) that involves the gastrointestinal tract. We aimed to investigate the incidence and predisposing factors of iodinated CM-associated bowel angioedema during computed tomography (CT) examinations., Materials and Methods: This study was approved by our institutional review board, and informed consent was waived due to its retrospective design. From July 2013 to July 2015, adult patients with a history of adverse reactions to iodinated CM during CT (group A, n = 427) and patients without adverse reactions matched for age and sex with the propensity-score matching method (group B, n = 427) were studied. Contrast media-associated bowel angioedema was determined when bowel wall thickness increased after contrast enhancement compared with the precontrast scan. Potential predisposing factors including patient demographics, symptoms and time of adverse reactions, and CM-related factors were compared between patients with and without angioedema in group A. In addition, the incidence of bowel angioedema was compared between groups A and B., Results: The incidence of CM-associated bowel angioedema in group A was 3.3% (14/427) in the per-patient analysis and 2.6% (15/578) in the per-examination analysis. The CM-associated bowel angioedema involved the distal duodenum and/or proximal jejunum and showed long-segmental circumferential bowel wall thickening on CT. None of the studied predisposing factors was different between patients with and without bowel angioedema (P > 0.05). The incidence of CM-associated bowel angioedema in group B was 1.9% (8/427) and 1.7% (8/458) for per-patient and per-examination analyses, respectively, and these rates were not significantly different between groups A and B (P = 0.346 and P = 0.370, respectively)., Conclusions: The incidence of CM-associated bowel angioedema during CT was 1.7% to 3.3%, and none of the studied predisposing factors was associated with bowel angioedema.

Objective: To assess the efficacy of preoperative magnetic resonance imaging (MRI) in identifying upper rectal cancer patients who are at high risk for local recurrence., Methods: 110 upper rectal cancer patients with locally advanced (pT3-4N0 or pTanyN+) tumors treated with tumor-specific mesorectal excision and no adjuvant radiotherapy were identified from an institutional database at a large academic medical center in Korea. Information on the extent of mesorectal invasion, sacral-side involvement was collected from preoperative MRI., Results: At a median follow-up of 47 months, 5 patients (4.5%) experienced local recurrence (LR). LR rates for patients with intermediate risk (T1-2/N1, T3N0), moderately high risk (T1-2/N2, T3N1, T4N0), and high risk (T3N2, T4/N1-2) were 3%, 4.8%, and 8.7%, respectively. Patients who did not have sacral-side involvement or mesorectal invasion of 5 mm or less did not experience LR. The patients with sacral-side involvement and intermediate risk, moderately high risk, and high risk had an LR rate of 4.2%, 5.6%, and 10%, respectively, or 11.1%, 33.3%, and 18.2%, respectively, when combined with those with mesorectal invasion of greater than 5 mm. Multivariate analyses demonstrated the presence of both sacral-side location and mesorectal invasion of greater than 5 mm was significantly associated with adverse disease-free and overall survival (P < 0.05)., Conclusions: Patients with mesorectal invasion of greater than 5 mm and sacral-side involvement identified on MRI were at an increased risk of local recurrence. The detection of these features on MRI provides prognostic information that is not available in conventional risk classification systems. Improved identification of a high-risk subset of upper rectal cancer patients may guide indications for preoperative chemoradiotherapy in this subset.

Objectives: The aim of the present study was to evaluate the diagnostic role of computed tomographic enterography (CTE) in distinguishing Crohn disease (CD) from intestinal tuberculosis (ITB)., Materials and Methods: From January 2006 to August 2011, a total of 81 consecutive patients (64 patients with CD and 17 patients with ITB) who received CTE on the initial workup were included. In CTE, degree of bowel involvement (number and length), mural change (mural hyperenhancement, stratification, wall thickening, and distribution), adjacent mesenteric change (comb sign, fibrofatty proliferation, fistula, abscess, and lymphadenopathy), and peritoneal change (peritoneal thickening and ascites) were assessed., Results: Segmental involvement, comb sign, fibrofatty changes, moderate wall thickening, and asymmetric distribution were significantly more common in the patients with CD than those with ITB. A positive comb sign was the most suggestive finding of CD (sensitivity, 74.1%; specificity, 90.9%)., Conclusions: A positive comb sign is the most suggestive finding that differentiates CD from ITB.

Objective: To evaluate the clinical usefulness of positive oral contrast computed tomography (CT) for the detection of leakage and its relationship with the immediate postoperative outcome after gastrectomy for gastric cancer., Methods: A total of 210 patients with a clinical suspicion of leakage after gastrectomy for gastric cancer underwent a positive oral contrast CT. Two radiologists retrospectively reviewed the CT images, recorded the presence of extraluminal contrast leakage, and graded the amount of leaked contrast. The rate of postoperative intervention treatment, the length of postoperative hospital stay, and mortality rates were correlated with the presence and grades of leakage. Matching accuracy between CT and other diagnostic studies in detection of leakage was also evaluated., Results: There were 162 patients without extraluminal contrast leakage (77.1%), 13 with grade 1 leakage (6.2%), 19 with grade 2 (9.0%), and 16 with grade 3 (7.6%). Postoperative intervention rate, hospital stay, and mortality were significantly higher in patients with extraluminal contrast than those in patients without extraluminal contrast (P < 0.05). Postoperative hospital stays increased as the leakage grades increased (P = 0.0008). The matching accuracy between CT and other studies was 82.1% (n = 32/39)., Conclusions: Positive oral contrast CT can be a reliable tool for diagnosing postoperative leakage that requires further intervention after gastrectomy in gastric cancer patients, and the immediate postoperative outcome may be related with the grade of leaked contrast on CT.

Objectives: To formulate an iodine-based contrast agent with an oil-in-water emulsion and to evaluate the feasibility of the agent for use as an interstitial computed tomographic (CT) lymphographic agent in a normal rat model., Materials and Methods: The effect of iodized oil (lipiodol) content and the type of surfactant/cosurfactant on the resultant emulsion size and polydispersity was investigated to obtain an optimized lipiodol emulsion for CT lymphography. Optimized emulsions (144 mg/mL) were injected in the hind paws of 6 rats, using 0.5 mL per paw. As control groups, iopamidol solution and lipiodol diluted with squalene to adjust the injection volume with iodine concentration equivalent to the emulsions were used. Precontrast and postcontrast CT images up to 1 week after contrast agent injection were obtained. Time-enhancement curves of the popliteal lymph nodes were obtained. Analysis of variance and post hoc analysis with the Dunn procedure were used for comparing mean peak enhancement, time to peak enhancement, and sustained duration of contrast enhancement., Results: Optimized emulsion formulations composed of 30% lipiodol and 282 mg/mL of 9:1 surfactant mixture (Tween 80:TPGS [alpha-tocopheryl polyethylene glycol succinate], Tween 80:Kollidon 12 PF, or Tween 80:Span 85) exhibited mean particle size less than 120 nm, and they were stable without significant particle size change up to 1 month. Targeted lymph nodes in all emulsion groups showed continuously increasing enhancement until 4 or 8 hours after injection, followed by continuous washout. Peak enhancement (time to peak enhancement) was 172.4 +/- 54.5 HU (Hounsfield unit) (384.0 +/- 131.5 minutes) for Tween 80:TPGS; 172.8 +/- 28.0 HU (432.0 +/- 107.3 minutes) for Tween 80:Kollidon 12 PF, and 177.2 +/- 68.9 HU (294.0 +/- 190.2 minutes) for Tween 80:Span 85. For iopamidol, peak enhancement of 153.0 +/- 46.1 HU (0.5 +/- 0.5 minutes) occurred early with rapid washout. For lipiodol as a reference agent, contrast enhancement continuously increased even 1 week after injection without washout (peak enhancement, 486.0 +/- 97.4 HU). Peak enhancement among the emulsion groups and the iopamidol group was not statistically different (P = 0.95). All emulsion groups showed more prolonged enhancement than the iopamidol group; enhancement duration for the emulsion groups was 534.0 +/- 481.1 minutes for Tween 80:TPGS; 957.0 +/- 524.8 minutes for Tween 80:Kollidon 12 PF; and 750.0 +/- 566.0 minutes for Tween 80:Span 85, and enhancement duration for iopamidol was 8.2 +/- 12.3 minutes (all P < 0.05 in multiple comparisons). However, there was no significant difference in enhancement duration among the 3 emulsion groups (P > 0.05)., Conclusions: Iodized oil emulsion made with a surfactant mixture (Tween 80 as the main surfactant and TPGS, Kollidon 12 PF, or Span 85 as the cosurfactant) provided sufficient and sustained contrast enhancement on CT of targeted lymph nodes with washout on delayed phase.

Objective: To identify conditions that might impair the delayed selective hepatobiliary enhancement of gadobenate dimeglumine., Materials and Methods: Ninety-five gadobenate-enhanced magnetic resonance imaging studies were retrospectively and independently analyzed. The effects of selective hepatic enhancement and biliary excretion were each categorized into 3 grades according to the perceived difference of signal intensity between the liver parenchyma and portal vein, and signal intensity in the common bile duct of precontrast- and delayed-phase images.History of diffuse liver disease, liver cirrhosis, and renal disease; elevated levels of blood urea nitrogen (BUN)/creatinine (Cr), aspartate aminotransferase (AST)/alanine aminotransferase, bilirubin, and alkaline phosphatase (ALP); ascites; and splenomegaly were compared according to the grade of hepatic and biliary enhancement., Results: Diffuse liver disease (P = 0.002); cirrhosis (P < 0.001); renal disease (P = 0.022); ascites (P = 0.001); splenomegaly (P < 0.001); and elevated levels of BUN (P = 0.001), Cr (P = 0.003), AST (P < 0.001), bilirubin (P < 0.001), and ALP (P < 0.001) were factors that impaired selective hepatic enhancement. Biliary excretion was affected by the presence of liver disease (P < 0.001), cirrhosis (P < 0.001), splenomegaly (P < 0.001), ascites (P = 0.002), and elevated levels of Cr (P = 0.013), AST (<0.001), alanine aminotransferase (P = 0.001), bilirubin (P < 0.001), and ALP (P < 0.001)., Conclusion: Delayed selective hepatobiliary enhancement of gadobenate dimeglumine can be impaired by liver or renal disease and/or by elevated levels of bilirubin, ALP, BUN, and Cr.

Objective: The aim of this study was to investigate differential imaging features between benign and malignant solid pseudopapillary neoplasms (SPN) of the pancreas on computed tomographic and magnetic resonance imagings., Methods: Between January 2001 and January 2007, we identified 30 patients with confirmed SPN by surgery. The computed tomographic and magnetic resonance images were reviewed by 3 radiologists in consensus. Each tumor was analyzed for the following categories: location of tumor, tumor margin, proportion of solid component, morphology of capsule, growth pattern, calcification, and presence of upstream pancreatic ductal dilatation., Results: Benign SPN usually had oval/round or smoothly lobulated margins, and malignant SPN more commonly had focal lobulated margins (P = 0.027). Presence of complete encapsulation was more frequently seen in benign SPN, whereas focal discontinuity of capsule was more commonly seen in malignant SPN (P = 0.005). There was no statistical difference between benign and malignant tumors in other imaging findings., Conclusions: A focal lobulated margin and a focal discontinuity of the capsule may suggest malignant SPN, whereas a round or smoothly lobulated margin and a complete encapsulation were more commonly seen in benign SPN.

Objective: This study describes the computed tomographic (CT) findings of true leiomyomas in the stomach., Methods: Eleven patients with histopathologically proven gastric true leiomyomas were finally enrolled. All cases were CD117 (c-kit) negative on immunohistochemical study. We retrospectively reviewed the CT findings of gastric true leiomyomas for the following considerations: location, morphological features (size, contour, tumor growth pattern, and enhancement pattern), and ancillary findings (ulceration and calcification)., Results: All leiomyomas were in the cardia, with an average tumor size of 36 mm (range, 13-47 mm). Computed tomography scans revealed the morphological features as follows: tumor growth pattern: intraluminal mass (n = 10) and extraluminal masses (n = 1); contour: lobulated margin (n = 7) or smooth margin (n = 4). All lesions showed homogeneous contrast enhancement. Most of the tumors showed lower enhancement than those in the liver (n = 10). One case showed ulceration but no calcification., Conclusions: In conclusion, gastric leiomyomas are mainly located in the cardia and usually appeared as homogenous low attenuated masses on computed tomography.

Purpose: To evaluate the diagnostic accuracy of multidetector row computed tomography (MDCT) for the preoperative T- and N staging of gastric cancer., Materials and Methods: Eighty-four consecutive patients with gastric cancer underwent preoperative MDCT. Except for 15 patients who did not undergo surgery, 69 patients were included in our study. Two radiologists independently evaluated the T- and N staging on the axial CT images alone and in combination with the MPR images. For N staging, the new TNM and Japanese classifications were independently used. Differences in staging accuracy for T- and N staging were assessed using the McNemar test., Results: The overall T staging accuracy of the axial and combined axial and MPR images was as follows: 67% (47 of 70 cancers) versus 77% (54 of 70 cancers) (P=0.039). The overall N staging accuracy of the axial and combined axial and MPR images was as follows: 59% (41 of 69 cancers) versus 67% (46 of 69 cancers) (P=0.180, Japanese classification) and 54% (37 of 69 cancers) versus 59% (41 of 69 cancers) (P=0.109, TNM classification)., Conclusions: Using MPR images enables more accurate preoperative T staging of gastric cancer, but not for N staging in either classification system.

Purpose: This study sought to evaluate the accuracy of multidetector computed tomography (MDCT) for preoperative staging of extrahepatic bile duct (EHD) carcinoma and to assess the value of coronal reformations from isotropic voxels., Materials and Methods: Thirty patients with surgically proven EHD cancer underwent dynamic MDCT with coronal reformation. Two experienced radiologists independently evaluated contrast-enhanced dynamic transverse CT images (axial approach) and combined transverse and coronal images (combined approach). The radial extent (TNM staging) and the vertical extent of tumors were assessed and correlated with pathological findings of surgical specimen., Results: All of primary tumors were detected by axial and combined CT imaging (100%). Overall accuracy of the T staging was 73% (22/30) with axial and 77% (23/30) with combined CT imaging (P>0.05). The accuracy of N staging was 57% (17/30) with axial and 63% (19/30) with combined CT imaging (P>0.05). The accuracy of M staging was 97% (29/30) with both axial and combined CT imaging. Upper margin accuracy was 97% (29/30) for axial and 100% for combined CT imaging (P>0.05), whereas that of the lower margin was 90% (27/30) for axial and 93% (28/30) for combined CT imaging (P>0.05)., Conclusions: Multidetector computed tomography was sufficiently accurate for evaluating the vertical extents, but radial extents of EHD cancer. The addition of coronal reformatted images did not improve the accuracy for staging of EHD cancer.

The objective of this study was to determine the optimal scan delay time after hepatic parenchymal enhancement using a 16-channel multidetector row helical CT (MDCT) scanner. Two hundred fifty-five consecutive patients underwent biphasic CT scans using a 16-channel MDCT. In group A (n = 125), two hepatic venous phase scans (HVP1 and HVP2) were obtained at 40 and 60 seconds, after 100-HU threshold time (T100HU) in the abdominal aorta. In group B (n = 130), HVP1 and HVP2 scans were obtained 50 and 70 seconds after T100HU. Both groups were divided into subgroups that were given different contrast media. Groups A1 and B1 received a contrast medium of 300 mgI/mL; groups A2 and B2 received a contrast medium of 370 mgI/mL. Each patient was injected with contrast medium at a dose of 2 mL/kg at a rate adjusted to the patient's body weight with a constant injection duration of 47 seconds. The attenuation values (HU) for the liver, portal vein, hepatic vein, and aorta were measured. The average HU was compared between the groups. Hepatic enhancement in the images obtained at 50 and 60 seconds after T100HU was greater (P < 0.05) than in images obtained at 40 and 70 seconds. These results were obtained with both contrast media. A few patients showed greater enhancement at a 40 seconds or 70 seconds. Hepatic enhancement was significantly greater in all scans using a contrast medium dose of 370 mgI/mL compared with the 300-mgI/mL dose (P < 0.05). Independent of the concentration of contrast medium, scan delays of 50 to 60 seconds after T100HU may provide optimal hepatic enhancement.

Cystic neoplasms in the pancreas encompass a broad spectrum of benign, borderline, and malignant lesions that either are primarily cystic or result from the cystic degeneration of solid tumors. Although these lesions show different histologic findings, the overlap of the radiologic findings for many pancreatic cystic lesions makes differentiation difficult, and the clinical manifestations can also overlap. Therefore, some of the pancreatic cystic lesions, especially uncommon lesions, can cause diagnostic confusion, and this may result in unnecessary surgery or inappropriate follow-up. In this article, we discuss and illustrate the radiologic features of unusual cystic neoplasms and the unusual findings of the relatively common cystic neoplasms in the pancreas. We also correlate the radiologic findings with the findings on pathologic analysis.

An annular pancreas is a rare congenital anomaly in which a portion of the pancreatic tissue surrounds the duodenum. Magnetic resonance cholangiopancreatography (MRCP) is used extensively for evaluating the pancreatobiliary ducts. There have been only few cases in which MRCP clearly demonstrated the types of annular ducts, however. Two cases of an annular pancreas based on a new classification of the morphologic type are reported.