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 patientswith 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 perexamination 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 ofCM-associated bowel angioedema during CTwas 1.7% to 3.3%, and none of the studied predisposing factors was associated with bowel angioedema.

Pancreatic surgery remains the only curative treatment for pancreatic neoplasms, and plays an important role in the management of medically intractable diseases. Since the original Whipple operation in the 20th century, surgical techniques have advanced, resulting in decreased postoperative complications and better clinical outcomes. Normal postoperative imaging findings vary greatly depending on the surgical technique used. Radiologists are required to be familiar with the normal postoperative imaging findings, in order to distinguish from postoperative complications or tumor recurrence. In this study, we briefly review a variety of surgical techniques for the pancreas, and present the normal postoperative computed tomography findings.

OBJECTIVE:To validate the diffusion-weighted MRI (DWI) for differentiation of benign from malignant portal vein thrombosis. MATERIALS AND METHODS:The Institutional Review Board approved this retrospective study and waived informed consent. A total of 59 consecutive patients (52 men and 7 women, aged 40-85 years) with grossly defined portal vein thrombus (PVT) on hepatic MRI were retrospectively analyzed. Among them, liver cirrhosis was found in 45 patients, and hepatocellular carcinoma in 47 patients. DWI was performed using b values of 50 and 800 sec/mm(2) at 1.5-T unit. A thrombus was considered malignant if it enhanced on dynamic CT or MRI; otherwise, it was considered bland. There were 18 bland thrombi and 49 malignant thrombi in 59 patients, including 8 patients with simultaneous benign and malignant PVT. Mean apparent diffusion coefficients (ADCs) of benign and malignant PVTs were compared by using Mann-Whitney U test. Diagnostic accuracy was evaluated using receiver operating characteristic (ROC) curve analysis. RESULTS:The mean ADC ± standard deviation of bland and malignant PVT were 1.00 ± 0.39 × 10(-3) mm(2)/sec and 0.92 ± 0.25 × 10(-3) mm(2)/sec, respectively; without significant difference (p = 0.799). The area under ROC curve for ADC was 0.520. An ADC value of > 1.35 × 10(-3) mm(2)/sec predicted bland PVT with a specificity of 94.6% (95% confidence interval [CI]: 84.9-98.9%) and a sensitivity of 22.2% (95% CI: 6.4-47.6%), respectively. CONCLUSION:Due to the wide range and considerable overlap of the ADCs, DWI cannot differentiate the benign from malignant thrombi efficiently.

In the field of contrast-enhanced ultrasonography (US), contrast agents are classified as either first- or second-generation agents depending on the gas within the microbubbles. In the case of first-generation contrast agents, a high-mechanical-index technique is used and only intermittent scanning is possible due to the early destruction of the microbubbles during the scanning. The use of second-generation contrast agents in a low-mechanical-index technique enables continuous scanning. Besides the detection and characterization of focal liver lesions, contrastenhanced US is helpful in the monitoring of radiofrequency ablation therapy and in the targeting step of an US-guided biopsy. Recently, there has been a demand for new criteria to evaluate the treatment response obtained using anti-angiogenic agents because morphologic criteria alone may not reflect the treatment response of the tumor and contrast-enhanced US can provide quantitative markers of tissue perfusion. In spite of the concerns related to its cost-effectiveness, contrast-enhanced US has the potential to be more widely used as a complimentary tool or to substitute the current imaging modalities in some occasions.

Objective To assess the added value of arterial enhancement fraction (AEF) color maps for the differentiation of small metastases from hepatic benign lesions. Subjects and Methods We retrospectively analyzed 46 patients with colorectal cancer who underwent multiphasic liver CT imaging and had low-attenuating liver lesions smaller than 3 cm (123 total lesions; metastasis: benign = 32:91). AEF color maps of the liver were created from multiphasic liver CT images using dedicated software. Two radiologists independently reviewed multiphasic CT image sets alone and in combination with image sets with AEF color maps using a five-point scale. The additional diagnostic value of the color maps was assessed by means of receiver-operating characteristic (ROC) analysis. Results The area under the ROC curve (Az) increased when multiphasic CT images were combined with AEF color map analysis as compared with evaluation based only on multiphasic CT images (from 0.698 to 0.897 for reader 1, and from 0.825 to 0.945 for reader 2; P < 0.001 and 0.002, respectively). The increase Az was especially significant for lesions less than 1 cm (from 0.702 to 0.888 for reader 1, and from 0.768 to 0.958 for reader 2; P = 0.001 and P = 0.001, respectively). The mean AEF of tumor-adjacent parenchyma (35.07 ± 27.2) was significantly higher than that of tumor-free liver parenchyma (27.3 ± 20.6) (P = 0.04). Conclusions AEF color mapping can improve the diagnostic performance for small hepatic metastases from colorectal cancer and may allow for the elimination of additional examinations.

Purpose: To investigate the optimal blending percentage of adaptive statistical iterative reconstruction (ASIR) in a reduced radiation dose while preserving a degree of image quality and texture that is similar to that of standard-dose computed tomography (CT).Materials and Methods: The CT performance phantom was scanned with standard and dose reduction protocols including reduced mAs or kVp.Image quality parameters including noise, spatial, and low-contrast resolution, as well as image texture, were quantitatively evaluated after applying various blending percentages of ASIR.The optimal blending percentage of ASIR that preserved image quality and texture compared to standard dose CT was investigated in each radiation dose reduction protocol.Results: As the percentage of ASIR increased, noise and spatial-resolution decreased, whereas low-contrast resolution increased.In the texture analysis, an increasing percentage of ASIR resulted in an increase of angular second moment, inverse difference moment, and correlation and in a decrease of contrast and entropy.The 20% and 40% dose reduction protocols with 20% and 40% ASIR blending, respectively, resulted in an optimal quality of images with preservation of the image texture.Conclusion: Blending the 40% ASIR to the 40% reduced tube-current product can maximize radiation dose reduction and preserve adequate image quality and texture.

ObjectivesThe objectives of the study were to evaluate the image quality and diagnostic performance of sinogram-affirmed iterative reconstruction (SAFIRE) for detecting hepatic metastasis and to estimate the potential radiation dose reduction at abdominal computed tomography (CT).Materials and MethodsFifty-nine consecutive patients (mean age, 59.2 years; range, 42-81 years) who had hepatic metastasis and who underwent dual-source abdominal CT were enrolled in this study. The image noise of the liver was compared between full-dose filtered back projection images (FD-FBP) and simulated half-dose images, which used only single-source projection data, and reconstructed with different strengths of SAFIRE (HD-SAFIRE(1-5)) by 1-way analysis of variance with Bonferroni correction. The diagnostic performance for hepatic metastasis was compared by logistic regression with the weighted least squares method and noninferiority test between the FD-FBP images and the half-dose sinogram-affirmed iterative reconstruction (HD-SAFIRE) images.ResultsAs the SAFIRE strength increased, image noise decreased (P < 0.001). The images of HD-SAFIRE(2) showed similar image noise for liver parenchyma (13.4 Hounsfield unit [HU]), signal-to-noise ratio for liver parenchyma (9.2), and lesion-to-liver contrast-to-noise ratio (4.5), compared with the FD-FBP images (12.6 HU, P = 0.668; 9.6, P > 0.999; and 4.5, P > 0.999, respectively). The diagnostic accuracy for hepatic metastasis with the HD-SAFIRE(2) images (87.5%) was not different from that of the FD-FBP images (87.5%, P > 0.999). The diagnostic performance of the HD-SAFIRE(2) images was also noninferior to that of the FD-FBP images (95% confidence interval lower limit difference [-9.16%] excluding the -10% clinical noninferiority limit). The mean (SD) volume CT dose index of FD-FBP was 11.26 (2.66) mGy, and the mean (SD) radiation dose equivalent associated with HD-SAFIRE was estimated to be 5.63 (1.33) mGy.ConclusionsBy applying SAFIRE(2), the radiation dose could be reduced by up to 50% compared with the standard-of-care abdominal CT protocol without increasing image noise and without deteriorating diagnostic performance for the detection of hepatic metastasis.

Purpose : To assess the usefulness of rectal filling using ultrasonographic gel in patients with lower rectal cancer. Materials and Methods: Twenty five patients with lower rectal cancer were enrolled. High resolution pelvic MR was performed twice before and after gel filling. Independently and retrospectively, two radiologists reviewed each set of MR images using five-grade scales for sphincter involvement, CRM (circumferential resection margin) involvement and depiction of the tumor. Same two radiologists retrospectively performed consensus review of each set of MR images for tumor distance from the anal verge and T&N staging. Results: Tumor depiction scores from MR with gel filling were significantly higher than those of MR without distention (p 0.05). Distance from the anal verge was significantly different between MR with gel filling and rigid endoscopy (6.8 1.6 cm vs. 5.8 1.6 cm, p=0.001). There were no significant differences between pathological staging and MR staging with or without gel filling. Conclusion: MR with gel filling improved tumor depiction. And also MR with gel filling revealed same ability for the predictions of CRM or sphincter invasion in patients with lower rectal cancer, comparing with MR without gel filling. Index words : Rectal cancer∙Magnetic resonance imaging (MRI)∙Rectum∙Ultrasonographic transmission gel Preoperative staging

BACKGROUND/AIMSTo assess the perfusion parameters and angiogenesis of HCC using dynamic contrast enhanced(DCE) MR and to correlate it with histopathologic findings in an experimental rat model.METHODOLOGYTwenty rats were continuously infused with diethylnitrosamine (DEN) for tumor induction. After 32 to 36 weeks of DEN treatment, the rats underwent MRI of the liver with a 3-T MR imaging system. Perfusion parametric maps and perfusion parameters such as, time to peak (TTP) and peak enhancement (PE) were obtained by using a commercially available software package. The nodules were correlated precisely to DCE MR images.RESULTSA total of 13 nodules were found in 12 rats; 5 dysplastic nodule (DN)s were identified in 5 rats and 8 HCCs (3 Edmonson grade I, 2 Edmonson grade I-II, 3 Edmonson grade II) were found in 7 rats. There were significant differences in mean values of PE and HPH (histogram peak height) of PE between DN and HCC. Mean value and HPH of PE showed statistically significant correlation with tumor grade.CONCLUSIONSThere were significant differences in perfusion parameters between DN and HCC. DCE MR imaging can be used in the differential diagnosis and management of liver disease in hepatocarcinogenesis.

OBJECTIVE The objective of our study was to determine the feasibility of using Metal Artifact Reduction (MAR) software for abdominopelvic dual-energy CT in patients with metal hip prostheses. MATERIALS AND METHODS This retrospective study included 33 patients (male-female ratio, 19:14; mean age, 63.7 years) who received total hip replacements and 20 patients who did not have metal prostheses as the control group. All of the patients underwent dual-energy CT. The quality of the images reconstructed using the MAR algorithm and of those reconstructed using the standard reconstruction was evaluated in terms of the visibility of the bladder wall, pelvic sidewall, rectal shelf, and bone-prosthesis interface and the overall diagnostic image quality with a 4-point scale. The mean and SD attenuation values in Hounsfield units were measured in the bladder, pelvic sidewall, and rectal shelf. For validation of the MAR interpolation algorithm, pelvis phantoms with small bladder "lesions" and metal hip prostheses were made, and images of the phantoms both with and without MAR reconstruction were evaluated. RESULTS Image quality was significantly better with MAR reconstruction than without at all sites except the rectal shelf, where the image quality either had not changed or had worsened after MAR reconstruction. The mean attenuation value was changed after MAR reconstruction to its original expected value at the pelvic sidewall (p < 0.001) and inside the bladder (p < 0.001). The SD attenuation value was significantly decreased after MAR reconstruction at the pelvic sidewall (p = 0.019) but did not show significant differences at the bladder (p = 0.173) or rectal shelf (p = 0.478). In the phantom study, all lesions obscured by metal artifacts on the standard reconstruction images were visualized after MAR reconstruction; however, new artifacts had developed in other parts of the MAR reconstruction images. CONCLUSION The use of MAR software with dual-energy CT decreases metal artifacts and increases diagnostic confidence in the assessment of the pelvic cavity but also introduces new artifacts that can obscure pelvic structures.

PurposeTo assess whether MR perfusion and diffusion parameters taken before concurrent chemoradiotherapy (CCRT) are useful imaging biomarkers for predicting progression‐free survival (PFS) in patients with hepatocellular carcinoma (HCC).Materials and MethodsTwenty patients with locally advanced HCC who had no treatment before CCRT underwent dynamic contrast‐enhanced (DCE) and diffusion‐weighted MRI. Mean values of the volume transfer constant (Ktrans), reflex constant (Kep), extravascular extracellular volume fraction (Ve) and the apparent diffusion coefficient (ADC) were estimated on a region of interest. The best cutoff value for each factor was assessed to differentiate between patients who had PFS shorter or longer than the median PFS. Patients were dichotomized in terms of the cutoff value. The survival outcome of the two groups and the predictive ability of each factor on PFS were evaluated.ResultsMedian time to PFS was 179 days. The best cutoff values for ADC, Ktrans, Kep, and Ve was 1.008 × 10−3 mm2 s−1, 0.108 min−1, 0.570 min−1, and 0.298%. Patients with higher ADC had significantly longer PFS than those with lower ADC(P < 0.0001).ConclusionThe ADC of HCC acquired before CCRT correlated with PFS and was valuable in the prediction of the clinical outcome of HCC treated with CCRT. J. Magn. Reson. Imaging 2014;39:286–292. © 2013 Wiley Periodicals, Inc.

To compare the accuracy of multidetector computed tomography (MDCT) and gadoxetic acid-enhanced magnetic resonance imaging (MRI) for the detection of intrahepatic tumor recurrence after curative resection of hepatocellular carcinoma (HCC).

Background & AimsThe dynamic enhancement pattern of HCCs smaller than 3cm in diameter on gadoxetic acid-enhanced magnetic resonance imaging (MRI) have not been extensively investigated. We aimed to evaluate the dynamic enhancement patterns of small HCCs (3cm) on gadoxetic acid-enhanced magnetic resonance imaging (MRI) and compare enhancement patterns with multiphasic multidetector computed tomography (MDCT) based on tumour cellular differentiation and size.MethodsWe retrospectively included 55 patients with 67 surgically confirmed small HCCs (3cm) who underwent multiphasic MDCT and gadoxetic acid-enhanced MRI. Dynamic enhancement patterns were analysed according to tumour cellular differentiation and size. Hepatobiliary phase images were also analysed to assess their additional value.ResultsThe proportion of small HCCs demonstrating the typical enhancement pattern differed depending on tumour cellular differentiation on both MRI (P=0.001) and MDCT (P=0.001), but differed depending on tumour size only on CT (P=0.008). Gadoxetic acid-enhanced MRI more sensitively depicted the typical enhancement pattern than CT for all tumours (P=0.001), for moderately or poorly differentiated HCCs (P=0.021) and for HCCs 2cm (P=0.001). 80% of tumours with atypical enhancement could be diagnosed as HCC based on tumour size and hepatobiliary phase images.ConclusionsOn both gadoxetic acid-enhanced MRI and multiphasic CT, the dynamic enhancement patterns of small HCCs (3cm) differed according to tumour cellular differentiation. Gadoxetic acid-enhanced MRI more frequently demonstrated the typical HCC enhancement pattern than CT in small HCCs.

Purpose To investigate the correlations between parameters of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and prognostic factors in rectal cancer. Materials and Methods We studied 29 patients with rectal cancer who underwent gadolinium contrast-enhanced, T1-weighted DCE-MRI with a three Tesla scanner prior to surgery. Signal intensity on DCE-MRI was independently measured by two observers to examine reproducibility. A time-signal intensity curve was generated, from which four semiquantitative parameters were calculated: steepest slope (SLP), time to peak (Tp), relative enhancement during a rapid rise (Erise), and maximal enhancement (Emax). Morphologic prognostic factors including T stage, N stage, and histologic grade were identified. Tumor angiogenesis was evaluated in terms of microvessel count (MVC) and microvessel area (MVA) by morphometric study. As molecular factors, the mutation status of the K-ras oncogene and microsatellite instability were assessed. DCE-MRI parameters were correlated with each prognostic factor using bivariate correlation analysis. A p-value of <0.05 was considered significant. Results Erise was significantly correlated with N stage (r=-0.387 and -0.393, respectively, for two independent data), and Tp was significantly correlated with histologic grade (r=0.466 and 0.489, respectively). MVA was significantly correlated with SLP (r=-0.532 and -0.535, respectively) and Erise (r=-0.511 and -0.446, respectively). MVC was significantly correlated with Emax (r=-0.435 and -0.386, respectively). No significant correlations were found between DCE-MRI parameters and T stage, K-ras mutation, or microsatellite instability. Conclusion DCE-MRI may provide useful prognostic information in terms of histologic differentiation and angiogenesis in rectal cancer.

Autoimmune pancreatitis (AIP) has been considered an extraordinary type of chronic pancreatitis, with characteristic abundant IgG4-positive plasma cell infiltration and accompanying sclerosis, and was recently recognized as the pancreatic manifestation of IgG4-related sclerosing disease. Diagnosis of AIP has been recently increased with increase in awareness, dramatic improvement of radiological examination such as CT and MRI, and immunologic diagnostic assay tool including IgG and IgG4. Many investigators have focused on the image findings of AIP on CT and MR and its differential diagnosis from the common bile duct (CBD) or pancreatic cancer.

As a result of recent developments in imaging modalities and wide spread routine medical checkups and screening, more incidental liver lesions are found frequently on US these days. When incidental liver lesions are found on US, physicians have to make a decision whether to just follow up or to undergo additional imaging studies for lesion characterization. In order to choose the next appropriate imaging modality, the diagnostic accuracy of each imaging study needs to be considered. Therefore, we tried to compare the accuracy of contrast-enhanced multidetector CT (MDCT) and Gd-EOB-DTPA-enhanced MRI for characterization of incidental liver masses. We included 127 incidentally found focal liver lesions (94 benign and 33 malignant) from 80 patients (M: F = 45: 35) without primary extrahepatic malignancy or chronic liver disease. Two radiologists independently reviewed Gd-EOB-DTPA-enhanced MRI and MDCT. The proportion of confident interpretations for differentiation of benign and malignant lesions and for the specific diagnosis of diseases were compared. The proportion of confident interpretations for the differentiation of benign and malignant lesions was significantly higher with EOB-MRI(94.5%-97.6%) than with MDCT (74.0%-92.9%). In terms of specific diagnosis, sensitivity and accuracy were significantly higher with EOB-MRI than with MDCT for the diagnosis of focal nodular hyperplasia (FNH) and focal eosinophilic infiltration. The diagnoses of the remaining diseases were comparable between EOB-MRI and MDCT. Hence, our results suggested that Gd-EOB-MRI may provide a higher proportion of confident interpretations than MDCT, especially for the diagnosis of incidentally found FNH and focal eosinophilic infiltration.