Effects of threshold and delay time settings on image quality and vessel display in coronary CT angiography

HU Guoying; ZHOU Hong; LIU Xiaojing; HOU Jincheng

doi:10.20258/j.cnki.1006-9011.2025.08.011

Abstract：Objective To investigate the effects of threshold and delay time settings on image quality and vessel display in coronary artery CT angiography(CTA)examination.Methods 171 patients with suspected coronary artery disease were se-lected for coronary CTA examination,and were divided into high heart rate group(>90 beats/min),center rate group(70～90 beats/min),and low heart rate group(<70 beats/min),with 57 cases in each group,according to different heart rates.The CTA examination threshold was set at 100 HU in all three groups,and the delay times were set at 5.0,5.3,and 5.9 s in the high heart rate group,the center rate group,and the low heart rate group,respectively.The results of the three groups were subjected to im-age quality scoring;the coronary arteries were objectively evaluated by imaging,including the CT values within the luminal space in the proximal segments of the root of the ascending aorta(AA),the main trunk of the left coronary artery(LM),and the right coronary artery(RCA),with the root of the ascending aorta being the same as that in the LM and the RCA,CT values of the main pulmonary artery(AAP)at the same level of the ascending aortic root,signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)of the proximal part of the AA,LM,and RCA.The radiation parameter indexes of the single volumetric CT dose index(CTDIvol)and the dose-length product(DLP)were recorded,and the effective radiation dose(ED)was calculated.Results The image quality scores of the center rate group and the low heart rate group were better than those of the high heart rate group,and the differences were statistically significant(P<0.05).The mean CT values of AA,LM,and RCA proximal ves-sel lumen in the low heart rate group were higher than those in the high heart rate group and the center rate group,and the mean CT value of AAP in the high heart rate group was higher than that in the middle and low heart rate groups,and the differences were statistically significant(all P<0.05);and the mean values of proximal SNR and CNR in the low heart rate group of AA,LM,and RCA were higher than those in the high heart rate group and the center rate group,and the differences were statistically significant(all P<0.05).CTDIvol,DLP and ED in the low heart rate group were lower than those in the high heart rate group and center rate group,and the differences were statistically significant(all P<0.05).Conclusion In coronary CTA examination,the examination threshold and delay time settings have a certain impact on image quality and vascular imaging,in which the threshold value of 100 HU and delay time of 5.9 s can simultaneously obtain high-quality images of coronary arteries as well as the trigger threshold and reasonable time of contrast injection tracking,and the radiation dose is lower.