Study On The Optimization Of Coronary Artery CTA Imaging Scanning And Its Standardization And Individualized Reconstruction

Objectives:To explore the effects of heart rate changes after holding breath and time for recovering stable heart rate on the quality of coronary CTA.And to explore coronary CT three-dimensional post-processing standardized display and the construction of digital teaching platform.And to assess the value of CT angiography using low-voltage and low-concentration contrast media(CM)combined with knowledge-based iterative model reconstruction(IMR)in patients with coronary artery bypass grafts(CABG).Methods:(1)Totally 700 patients undergoing coronary CTA examination in some hospital were enrolled into the study,whose data on initial heart rate at rest condition,maximal heart rate during breath holding,stable heart rate after breath holding as well as the time consumed for recovering stable heart rate were collected and analyzed.(2)The conventional display positions of 3D post-processing image were summarized during daily coronary CTA examination,the common place was refined.The construction mode was explored for CTA digital teaching demonstration platform.(3)Totally 71 patients after CABG undergoing CT angiography in our center from June to November 2016 were prospectively enrolled and randomly assigned into groups A and B.The scan protocol for group A was 80 kVp with 300 mgI/ml contrast at an injection rate of 4 ml/s;images were reconstructed by IMR algorithm.The scan protocol for group B was 100 kVp with 370 mgI/ml contrast at an injection rate of 5 ml/s;images were reconstructed by hybrid iterative reconstruction technique.Aorta,left ventricular,and grafts were chosen as regions of interest The image quality,radiation dose,and contrast load were compared between two groups.Results:(1)A heart rate trendgram was drawn to find out the rules for heart rate changes and time for recovering stable heart rate,it can be known that the trend curve of heart rate change in 70.43%of patients undergoing coronary CT scan is ascending and then descending.97.58%of patients can reach a stable heart rate by inhaling from the command and holding before 9s.So that proper retrospective or prospective scanning scheme could be determined.(2)The standardized display of "commonness"+"individuality" coronary CTA 3D post-processing can obtain the 3D coronary image display of Chinese aesthetics and the personalized display of details for coronary artery lesions,so as to make the display of coronary artery image more beautiful and comprehensive.The CTA digital teaching demonstration platform met the teaching requirements.(3)The signal to noise ratio(SNR)and contrast to noise ratio(CNR)of the ascending aorta,descending aorta,left ventricular,and venous bridge in group A[SNR:19±5,20±5.7,19.1±4.9,and 37 t 34;CNR:17±4.7,18±5,16±5.4,and 34±32]were significantly higher than those in group B[SNR:16±6(P=0.012),15.6±5.5(P=0.002),15±6(P=0.002),24±8.3(P=0.035);CNR:14±5.5(P=0.010),13.8±5(P=0.002),13±5.7(P=0.014),21±7.8(P=0.031)],except for left internal mammary artery graft(LIMA),which was not inferior to that in group B.An effective radiation dose reduction of 49%was achieved in group A[(2.3±0.4)mSv,compared with group B(4.5±0.5)mSv(P=0.000)].The iodine load of group A was(20±1.4)g compared with(29±1.6)g in group B,resulting in a reduction of 31%(P=0.000).Conclusion:Mastering the rules in heart rate changes and time for recovering stable heart rate contributes to guiding coronary CTA.The coronary CT 3D post-processing standardized display and digital teaching platform facilitate the student to master related knowledge.The low tube voltage(80 kVp)and low contrast protocol combined with IMR in patients with CABG can reduce radiation dose and improve image quality of aorta,left ventricular and venous graft.The image quality of LIMA graft in low dose group is not inferior to that in regular dose group.