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Purpose: To assess the feasibility of extracellular volume (ECV) fraction determined with equilibrium contrast-enhanced MRI for prediction of treatment response to chemotherapy in pancreatic ductal adenocarcinoma (PDAC) in comparison with dynamic contrast-enhanced MRI (DCE-MRI), and to clarify the association between ECV fraction and DCE-MRI-derived pharmacokinetic parameters., Methods: This retrospective study included 58 consecutive patients with histologically confirmed PDAC who underwent DCE-MRI before systemic chemotherapy. Tumor pharmacokinetic parameters, including the volume transfer coefficient (K trans ), rate constant (k ep ), and extracellular extravascular volume fraction (v e ) of DCE-MRI, and ECV fraction determined with equilibrium contrast-enhanced MRI were compared between the response and non-response groups. The correlation of tumor ECV fraction with each DCE-MRI-derived pharmacokinetic parameter was examined using Spearman's rank correlation coefficient., Results: Tumor K trans , v e , and ECV fraction were significantly higher in the response group than in the non-response group (all, P < 0.001), whereas no significant difference was found in k ep (P = 0.119). Tumor ECV fraction showed the highest area under receiver operating characteristic curve of 0.918, with a sensitivity of 89.3%, specificity of 90.0%, and accuracy of 89.7% (cut off, >37.6%). The ECV fraction showed a significant positive correlation with K trans (Spearman's coefficient = 0.66, P < 0.001) and v e (Spearman's coefficient = 0.79, P < 0.001)., Conclusions: ECV fraction determined with equilibrium contrast-enhanced MRI was as useful as DCE-MRI-derived pharmacokinetic parameters for predicting treatment response to chemotherapy in patients with PDAC., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Purpose: To evaluate whether diffusion tensor imaging (DTI) can be used to differentiate malignant parotid gland tumors from the benign ones., Materials and Methods: The study population comprised 59 parotid gland tumors (24 Warthin's tumors, 19 pleomorphic adenomas, seven other benign tumors, and nine malignant tumors). Single-shot echo-planar DTI was performed with motion-probing gradients along 30 noncollinear directions (b=1000s/mm 2 ) at 3.0T. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values for benign and malignant tumors were compared using the Mann-Whitney U test. Receiver-operating characteristic (ROC) curve analysis was performed to assess the ability of the ADC and FA values to differentiate malignant tumors from the benign ones., Results: ADC values showed no significant difference between malignant (0.93±0.21×10 -3 mm 2 /s) and benign tumors (1.19±0.50×10 -3 mm 2 /s) (p=0.225). FA values of malignant tumors were significantly higher than those of benign tumors (0.26±0.06 vs. 0.17±0.05, p<0.001). The area under the ROC curve of FA was significantly greater than that under the curve of ADC (0.884 vs. 0.628, p=0.010)., Conclusions: DTI, particularly FA, can help differentiate malignant parotid gland tumors from the benign ones., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objective: To assess the feasibility of computed diffusion-weighted imaging (cDWI) in comparison with directly acquired DWI for visualizing pancreatic adenocarcinomas., Materials and Methods: Patients with pancreatic adenocarcinoma underwent DWI at b-values of 0, 1000 (DWI 1000 ), 1500 (DWI 1500 ) and 2000 (DWI 2000 ) s/mm 2 . From DWIs at b-values of 0 and 1000s/mm 2 , we generated cDWIs at b-values of 1500 (cDWI 1500 ) and 2000 (cDWI 2000 ) s/mm 2 . DWI findings of pancreatic adenocarcinomas (clear hyperintensity; hyperintensity with an unclear distal border; and isointensity), the image quality and the tumor to pancreas contrast ratio (CR) were compared between directly acquired DWI and cDWI., Results: Among the 63 included patients, clear hyperintense tumors were seen in 35 on DWI 1000 , 50 on DWI 1500 , 50 on cDWI 1500 , 53 on DWI 2000 and 44 on cDWI 2000 . Incidence of clear hyperintense tumors was significantly higher on cDWI 1500 than on DWI 1000 (P=0.013). There was no significant difference in the incidence of clear hyperintense tumors between DWI 1500 and cDWI 1500 (P>0.999), but a lower incidence was seen on cDWI 2000 than on DWI 2000 (P=0.028). Image quality was lower on cDWI than on DWI at b-values of 1500 (P=0.002) and 2000s/mm 2 (P<0.001). The tumor to distal pancreas CR was significantly higher on cDWI 2000 than on cDWI 1500 (P<0.001), and on cDWI 1500 than on DWI 1000 (P<0.001). The cDWI showed a significantly higher tumor to distal pancreas CR than DWI at b-values of 1500 (P=0.004) and 2000s/mm 2 (P<0.001)., Conclusions: cDWI 1500 generated from b-values of 0 and 1000s/mm 2 should be considered more effective than DWI 1000 and at least as effective as DWI 1500 ., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objective: To compare the quality of contrast enhancement and hepatic CT images acquired using bolus tracking technique at two different time points and those acquired with fixed scan delay technique using a previous bolus tracking data., Materials and Methods: Fifty patients who underwent 3 different hepatic CT exams (25-s fixed injection of 600 mg iodine (I)/kg or 100mL of 370 mg I/mL nonionic contrast medium) were enrolled. The first and second exams were performed with a bolus tracking technique. The third exam was performed with a fixed scan delay technique using the first exam data. Differences in attenuation values in the abdominal organs were examined and evaluated visually on hepatic arterial phase images., Results: There was no significant difference in the mean 50-HU threshold times between the first and second bolus tracking exams with intra-patient differences between them (1.3±0.9 s). No significant intra-patient differences were noted in organ attenuation and visual evaluation on hepatic arterial phase images between the 3 exams., Conclusion: The fixed scan delay technique using a previous bolus tracking data is feasible for hepatic CT exams to follow up hepatocellular carcinoma., (Crown Copyright © 2012. Published by Elsevier Ireland Ltd. All rights reserved.)