Evaluation of coronary artery in-stent restenosis with prospectively ECG-triggered axial CT angiography versus retrospective technique: a phantom study

Purpose This study compared the performance of prospectively electrocardiographically (ECG)-triggered axial computed tomography (CT) angiography with retrospective technique in evaluating coronary artery stent restenosis by 64-slice CT. Materials and methods A pulsing cardiac phantom with artificial coronary artery in-stent restenosis was examined by CT angiography with different types of scan modes. The visibility of in-stent restenosis was evaluated with a three-point score. Artificial lumen narrowing [(inner stent diameter-measured lumen diameter)/inner stent diameter], lumen attenuation increase ratio [(in-stent attenuation-coronary artery lumen attenuation)/coronary artery lumen attenuation], measurement error of restenosis percent [(known restenosis percent-measured restenosis percent)/known restenosis percent] and imaging noise were analysed. Results Prospective acquisition showed better visibility than retrospective acquisition ( p <0.05): 61% of in-stent restenoses had good visibility on the prospective acquisition compared with 17% on the retrospective acquisition. Furthermore, the effective dose was 6.2±0.3 mSv for the prospective technique compared with 18.8±1.1 mSv for the retrospective technique. Artificial lumen narrowing (mean 40%), lumen attenuation increase ratio (mean 33%) and measurement error of restenosis percent were not different between types of CT acquisitions. Conclusions Compared with the traditional retrospective technique, prospective coronary CT angiography offers improved image quality and reduces effective radiation dose in evaluating in-stent restenosis.