Application of the Dual-layer Spectral Detector CT in the CT Angiography of Superior Vena Cava.

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Objective To evaluate the application of the dual-layer spectral detector CT in the CT angiography of superior vena cava (SVC). Methods Totally 30 consecutive patients who underwent chest enhanced CT in our center were enrolled in this study. Eight series of images were reconstructed,including the conventional images at 120 kVp and seven series of virtual monoenergetic spectral images at 40,50,60,70,80,90,and 100 keV. The regions of interest (ROIs) were placed at the level of the proximal end,middle part,and distal end in the SVC vessel. The CT values and standard deviations of these three ROIs and the lipid on prothroax wall were measured. The signal to noise ratio (SNR),contrast to noise ratio (CNR),and effective dose (ED) were calculated. In addition,the quality of images was evaluated by two blinded readers using a grading scheme. The differences in CT values,SNR,and CNR among groups were analyzed using the independent t-test. The quality of all images was compared using non-parametric test between two readers,and the consistency between two radiologists were evaluated by using Kappa (κ) value. Results There was no significantly different attenuation value among three ROIs of the SVC for each monoenergetic images (all P>0.05). The SVC showed significantly higher attenuation value (223.51±40.35)HU,SNR 13.56±4.18 and CNR 24.15±6.58 in the 40 keV group than in other keV groups and the conventional group [attenuation value:(97.70±13.85)HU;SNR:4.59±1.41;CNR:9.69±2.81] (P<0.005). The mean ED was(2.04±0.63) mSv. The subjective diagnostic scores accessed from two radiologists were 1 (1,2) and 1 (1,2) (Z=-0.358,P=0.720). The subjective diagnostic quality values evaluated by two observers showed excellent consistency (κ=0.863,P=0.000). Conclusion An optimal imaging of the SVC can be achieved on monoenergetic reconstructions at 40 keV by using the dual-layer spectral detector CT.