Determination of arterial invasion in pancreatic ductal adenocarcinoma: what is the best diagnostic criterion on CT?

OBJECTIVES: To investigate the diagnostic performance and interobserver variability in the determination of arterial invasion in pancreatic ductal adenocarcinoma (PDAC) and determine the best CT imaging criterion. METHODS: We retrospectively evaluated 128 patients with PDAC (73 men and 55 women) who underwent preoperative contrast-enhanced CT. Five board-certified radiologists (expert) and four fellows (non-expert]) independently assessed the arterial invasion (celiac, superior mesenteric, splenic, and common hepatic arteries) using a 6-point score: 1, no tumor contact; 2, hazy attenuation ≤ 180°; 3, hazy attenuation > 180°; 4, solid soft tissue contact ≤ 180°; 5, solid soft tissue contact > 180°; and 6, contour irregularity. ROC analysis was performed to evaluate the diagnostic performance and determine the best diagnostic criterion for arterial invasion, with pathological or surgical findings as references. Interobserver variability was assessed using Fleiss's ĸ statistics. RESULTS: Among the 128 patients, 35.2% (n = 45/128) received neoadjuvant treatment (NTx). Solid soft tissue contact ≤ 180° was the best diagnostic criterion for arterial invasion as defined by the Youden Index both in patients who did and did not receive NTx (sensitivity, 100% vs. 100%; specificity, 90% vs. 93%; and AUC, 0.96 vs. 0.98, respectively). Interobserver variability among the non-expert was not inferior to that among the expert (ĸ = 0.61 vs 0.61; p = .39 and ĸ = 0.59 vs 0.51; p < .001 in patients treated with and without NTx, respectively). CONCLUSIONS: Solid soft tissue contact ≤ 180° was the best diagnostic criterion for the determination of arterial invasion in PDAC. Considerable interobserver variability was seen among the radiologists. KEY POINTS: • Solid soft tissue contact ≤ 180° was the best diagnostic criterion for the determination of arterial invasion in pancreatic ductal adenocarcinoma. • Interobserver agreement among non-expert radiologists was almost comparable to that among expert radiologists.

Optimal window settings in single-source dual-energy computed tomography of the abdomen.

PURPOSE: To determine the optimal window settings for monochromatic images with various energy levels in single-source dual-energy computed tomography (DECT) of the abdomen. MATERIALS AND METHODS: Two hundred consecutive patients underwent contrast-enhanced DECT to screen tumor metastases and/or recurrences after surgery for malignant tumors. Two independent radiologists reviewed eight energy levels (40, 45, 50, 55, 60, 65, 70, and 75 kilo-electron volts [keV]) of the portal venous phase monochromatic images. For each keV image, the radiologists adjusted the window level (WL) and width (WW) using settings of 40 HU of WL and 350 HU of WW on 65 keV images as a reference and recorded these values. After removing the top and bottom 5% of the data, the optimal WL and WW in each energy levels were obtained by rounding the median values. In 7 of 200 patients with a total of 23 liver metastases, the tumor-to-liver contrast-to-noise ratio (CNR) was calculated and compared among the energy levels. RESULTS: The optimal WLs and WWs at each energy level were as follows: 40 keV, 140 and 680 HU; 45 keV, 110 and 570 HU; 50 keV, 90 and 490 HU; 55 keV, 70 and 440 HU; 60 keV, 60 and 390 HU; 65 keV, 40 and 350 HU; 70 keV, 30 and 320 HU; and 75 keV, and 20 and 300 HU. The best CNR was obtained using 65 keV images (P < 0.001). CONCLUSION: We clarified the optimal WL and WW available for the preset window settings in abdominal DECT.

Gadoxetate disodium-enhanced MR imaging: differentiation between early-enhancing non-tumorous lesions and hypervascular hepatocellular carcinomas.

PURPOSE: To retrospectively assess imaging features that help differentiate early-enhancing non-tumorous (EN) hepatic lesions from hepatocellular carcinomas (HCCs) on gadoxetate disodium-enhanced MR imaging. MATERIALS AND METHODS: Our institutional review board approved this retrospective study. We reviewed the studies of 158 patients (92 men and 65 women; age range: 29-91; mean age: 65.6 years) with chronic liver damage, who underwent gadoxetate disodium-enhanced MR imaging at 3T MR scanner. Hypervascular lesions identified during the hepatic artery phase were selected for a study cohort. The location, shape, size (maximum diameter and maximum area), and contrast enhancement signal intensity characteristics of the lesions were evaluated, then compared between the EN and HCC lesions. RESULTS: A total of 65 EN lesions (range: 3-60mm, mean: 13.6 ± 10.6 mm) from 35 patients and 33 HCCs (range: 9-61 mm, mean: 19.3 ± 12.6 mm) from 20 patients were identified. Lesions were more frequently round or oval in shape for HCCs (n=29; 88%) than ENs (n=26; 40%) (P<0.01). Unexpectedly, some ENs (n=12; 18%) showed hypointensity on hepatocyte-phase, and 6 (50%) of them were T2 hyperintense. For lesions smaller than 2 cm (9 ENs and 21 HCCs) on hepatic arterial-phase images, the mean area of hypointensity in hepatocyte-phase (54.2 ± 33.1 mm(2)) was significantly smaller than those of the corresponding hyperintensity in hepatic arterial-phase (97.1 ± 42.0 mm(2)) for EN lesions (P=0.019), whereas no significant difference in area was found for HCCs. CONCLUSION: EN lesions may occasionally present with hypointensity during the hepatocyte-phase; presenting a diagnostic dilemma. In this situation, EN lesions may be differentiated from HCCs when a hypointense area in hepatocyte-phase is smaller than the corresponding hypervascular area in hepatic-arterial phase.

Indomethacin solubilization induced shape transition in CnE7 (n=14,16) nonionic micelles.

Shape transitions were examined with regard to the solubilization of the poorly water-soluble drug indomethacin (IMC) in the nonionic surfactants heptaethylene oxide tetradecyl (C14E7) and hexadecyl (C16E7) ethers by means of a dynamic light scattering technique. The cloud points of the pure C14E7 and C16E7 micelles ranged from 58 to 62 degrees C and from 52.1 to 55.6 degrees C, respectively, at surfactant concentrations of 1 to 10 mM. The cloud points of IMC-solubilized micelles increased by approximately 1 to 5 degrees . The sizes of the pure C14E7 micelles were 4 to 14 nm at 20 to 40 degrees C at a concentration of 2 to 20 mM. The apparent hydrodynamic radius (R happ) of pure C16E7 micelles varied with temperature and concentration. C16E7 surfactant formed small spherical micelles at 20 and 25 degrees C at concentrations below 5 mM; the size of the micelles was approximately 5 nm. On the other hand, from 30 to 40 degrees C and at a higher concentration, C16E7 formed elongated cylindrical micelles, and these elongated micelles entangled or overlapped each other. The R happ of the IMC-solubilized C14E7 micelles at 20 to 40 degrees C and of C16E7 micelles at 20 degrees C increased compared to that of pure micelles. On the other hand, the cylindrical micelles of C16E7 decreased in size and turned into spherical ones because of the hydrophobicity between the micelles caused by solubilization of IMC. This phenomenon was confirmed by transmission electron microscope (TEM) images.