PurposeTo investigate the value of spectral CT in the differential diagnosis of benign from malignant pleural effusion.Method and materials14 patients with benign pleural effusion and 15 patients with malignant pleural effusion underwent non-contrast spectral CT imaging. These patients were later verified by the combination of disease history, clinical signs and other information with the consensus of surgeons and radiologists. Various Spectral CT image parameters measured for the effusion were as follows: CT numbers of the polychromatic 140kVp images, monochromatic images at 40keV and 100keV, the material density contents from the water, fat and blood-based material decomposition images, the effective atomic number and the spectral curve slope. These values were statistically compared with t test and logistic regression analysis between benign and malignant pleural effusion.ResultsThe CT value of benign and malignant pleural effusion in the polychromatic 140kVp images showed no differences (12.61±3.39HU vs. 14.71±5.03HU) (P>0.05), however, they were statistically different on the monochromatic images at 40keV (43.15±3.79 vs. 39.42±2.60, p = 0.005) and 100keV (9.11±1.38 vs. 6.52±2.04, p<0.001). There was difference in the effective atomic number value between the benign (7.87±0.08) and malignant pleural effusion (7.90±0.02) (P = 0.02). Using 6.32HU as the threshold for CT value measurement at 100keV, one could obtain sensitivity of 100% and specificity of 66.7% with area-under-curve of 0.843 for differentiating benign from malignant effusion. In addition, age and disease history were potential confounding factors for differentiating malignant pleural effusion from benign, since the older age (61.13±12.51 year-old vs48.57±12.33 year-old) as well as longer disease history (70.00±49.28 day vs.28.36±21.64 day) were more easily to be found in the malignant pleural effusion group than those in the benign pleural effusion group. By combining above five factors, one could obtain sensitivity of 100% and specificity of 71.4% with area-under-curve of 0.933 for differentiating benign from malignant effusion.ConclusionThe CT value measurement at both high and low energy levels and the effective atomic number obtained in a single spectral CT scan can assist the differential diagnosis of benign from malignant pleural effusion.Combining them with patient age and disease history can further improve diagnostic performance.Clinical relevance/ApplicationClinical findings and Spectral CT imaging can provide significant evidences about the nature of pleural effusion.

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Objective: To evaluate the clinical value of dual-energy spectral CT with adaptive statistical iterative reconstruction (ASiR) for reducing contrast medium dose in CT portal venography (CTPV). Methods: This prospective study was institutional review board-approved, and written informed consent was obtained from all patients. 50 patients undergoing abdominal CT were randomized to 2 groups: Group A (n 5 25), using spectral CT and 350 mgI kg 21 contrast injection protocol; Group B (n 5 25), using standard 120 kVp and 500 mgI kg 21 contrast. Spectral CT images at 60 keV and standard 120-kVp images were both reconstructed with 50% ASiR. CT number and contrastto-noise ratio (CNR) for intrahepatic and extrahepatic portal veins were measured. The maximum intensity projection (MIP) and volume-rendering (VR) images were used for subjective evaluation. These two kinds of results were statistically analyzed. Results: CNR values for the intrahepatic portal vein of the 60-keV spectral images (4.2 6 1.1) were higher than those of 120-kVp images (3.0 6 2.1) (p 5 0.03) and were the same for the extrahepatic portal vein (5.9 6 1.4 vs 5.9 6 1.6, p 5 0.90). The portal vein and left and right branches in the 60-keV spectral images had higher CT number and lower standard deviation than the 120-kVp images (p , 0.05). Radiation dose (dose-length product and effective dose) and subjective image quality were similar for the two groups, while the spectral CT group required 25% less iodine dose (23.1 6 3.2 g vs 30.5 6 5.0 g). Conclusion:The 60-keV spectral CT images with ASiR allow 25% reduction in the iodine dose while providing better or equal image quality as the standard 120-kVp images in portal venography with comparable radiation dose. Advances in knowledge: Compared with conventional 120-kVp CT, the use of 60-keV spectral CT images provides 25% contrast dose reduction with similar image quality in CTPV. Compared with conventional 120-kVp CT, the use of 60-keV spectral CT images with ASiR algorithm improves CNR values for the intrahepatic portal vein.

Objective: To study the application of using low energy images combined with adaptive statistical iterative reconstruction (ASiR) in dual-energy spectral CT portal venography (CTPV) to reduce iodine load. Methods: 41 patients for CTPV were prospectively and randomly divided into two groups. Group A ( n = 21) used conventional 120 kVp scanning protocol with contrast dose at 0.6 gI/kg while group B ( n = 20) used dual-energy spectral imaging with reduced contrast dose at 0.3 gI/kg. The 120 kVp images in Group A and 50 keV images in Group B were reconstructed with 40% ASiR. The contrast-to-noise ratio of portal vein was calculated. The image quality and the numbers of intrahepatic portal vein branches were evaluated by two experienced radiologists using a 5-point scoring system. Results: Group B reduced iodine load by 52% compared to Group A (17.21 ± 3.30 gI vs 35.80 ± 6.18 gI, p < 0.001). All images in both groups were acceptable for diagnosis. CT values and standard deviations in portal veins of Group B were higher than Group A (all p < 0.05); There were no statistical differences in contrast-to-noise ratio, image quality score and the number of observed portal vein branches between the two groups (all p > 0.05), and the two observers had excellent agreement in image quality assessment (all κ > 0.75). Conclusion: The use of 50 keV images in dual-energy spectral CTPV with ASiR reduces total iodine load by 52% while maintaining good image quality. Advances in knowledge: Spectral CT images combined with ASiR can be used in low contrast dose CTPV portal venography to maintain image quality and reduce contrast dose.