ABSTRACT
Objective:To explore the optimal monochromatic level for the observation of coronary in-stent lumen by dual-layer spectral CT (DLCT).Methods:Forty-nine patients with 74 stents after percutaneous coronary intervention (PCI) who underwent coronary CTA (CCTA) examinations by a DLCT between January 2016 and September 2017 were retrospectively enrolled. A total of 12 groups of images including 60-120 keV (kilo electron voltage) images with 10 keV interval, 140-200 keV images with 20 keV interval and conventional images. In-stent lumen diameter of proximal, mid and distal portion was measured. Difference of CT values between in-stent lumen and ascending aorta was used to describe as blooming artifact, and noise of in-stent lumen as image noise. Then Likert 5-point scale was performed to evaluate images noise, enhancement of in-stent lumen, blooming artifact and diagnostic confidence. Differences of objective and subjective parameters among conventional and various monochromatic images were compared by Friedman test.Results:In the diameter measurement of the proximal, middle and distal segments of the stent, the difference between the images of each group was statistically significant (χ 2 = 427.270, 426.375, 400.981, P< 0.001). The diameter of the lumen measured by 120-200 keV single-level image was larger than that measured by 60-100 keV single-level image, and the difference was statistically significant ( P< 0.05). In the comparison of CT difference between the stent lumen and ascending aorta, the difference between the images of each group was statistically significant (χ 2 = 242.193, P< 0.001), and 100-200 keV single-level images were lower than the conventional images, the difference was statistically significant ( P< 0.05). In the comparison of noise values, the difference between the images of each group was statistically significant (χ 2 = 420.161, P< 0.001), and the difference was statistically significant ( P< 0.05). In the subjective scores of noise, enhancement, halo artifact and diagnostic confidence, there were statistically significant differences among the groups (χ2= 333.827, 455.989, 276.824, 399.497, P< 0.001). The noise score of 100-200 keV single-level image was higher than that of conventional image, the difference was statistically significant ( P< 0.05). The enhancement score of 60 keV was significantly higher than that of other images ( P< 0.05). The halo artifact score of 100-200 keV single level image was higher than that of 60-90 keV image, the difference was statistically significant ( P<0.05). The scores of 90-120 keV single-level images were higher than those of other single-level images, and the difference was statistically significant ( P< 0.05). Conclusions:CCTA examinations can be effectively performed by DLCT in patients after PCI in clinical settings, and 120 keV is recommended as the optimal monochromatic image for the observation of in-stent lumen.