Objective:The purpose of this study was to investigate the optimal virtual single en-ergy of double-layer detector spectral CT for displaying the left colonic artery(LCA),so as to provide assistance for the evaluation of LCA before laparoscopic radical rectal resection.Methods:The images of 100 patients who underwent abdominal CT angiography in our hospital were retrospectively ana-lyzed.The original images of the arterial phase were reconstructed into mixed energy images and four groups of single energy images based on energy spectrum of 40～70keV with an interval of 10keV.The CT value,signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR),image noise and image quality scores of the LCA of the five groups of images were compared.Results:The CT value,noise,CNR and SNR of the LCA of single-energy images in the 40～70keV group decreased with the increase of ener-gy level.Compared with the conventional mixed energy image group and the 40～70keV single-energy image group,the differences in CT value,SNR,CNR and noise between the groups were statistically significant(P＜0.05).The CT value,CNR,and SNR of the LCA of the 40keV group were higher than those of other groups,and the noise was lower than that of the conventional mixed energy image group.The subjective evaluation of image quality of the two radiologists was consistent well(0.40≤Kappa value＜0.75),and the subjective score of image was statistically significant between the groups(P＜0.001).The subjective score of images in the 40keV group was the highest,and the single-energy image quality in the 40～70keV group was higher than that of conventional mixed energy images.Con-clusion:40keV is the best virtual single energy display of LCA,showing clear blood vessels with sharp edges,which can more clearly display LCA and its anatomical variants,which is conducive to the smooth progress of laparoscopic radical rectal cancer resection by surgeons.
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