Value of CT Angiography Using Low Tube Voltage and Low Contrast Combined with Iterative Model Reconstruction in Patients with Coronary Artery Bypass Grafts / 中国医学科学院学报

ABSTRACT

Objective 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 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 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 [SNR19±5,20±5.7,19.1±4.9,and 37±34;CNR17±4.7,18±5,16±5.4,and 34±32] were significantly higher than those in group B [SNR16±6 (P=0.012),15.6±5.5 (P=0.002),15±6 (P=0.002),24±8.3 (P=0.035);CNR14±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).Conclusions 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.