Value of Ultra-low Dose Coronary CT Angiography for Classification and Quantification of Coronary Stenosis

Objective: To investigate the agreement between 70 kV and 100 kV scan for classification and quantification of coronary artery stenosis, on wide-detector coronary computed tomography angiography (CCTA) examination. Methods: 70 patients of suspected or known coronary artery disease were included, who were suitable for CCTA. Single heartbeat CCTA was performed on 256-row wide-detector CT by using 70 kV and 100 kV tube voltage, respectively. Effective radiation dose and signal-to-noise ratio (SNR) were compared between these two groups. Nine coronary segments were evaluated, in which the stenosis degree was categorized as:normal (0%), mild (1%~49%), moderate (50%~69%) and severe (70%~100%). We recorded the number of consistent stenosis category between 70 kV and 100 kV scan. Bland-Altman analysis was used to evaluate coronary stenosis between 70 kV and 100 kV scan. Result: Effective radiation dose of 70 kV scan was significantly lower than that of 100 kV, which were (0.26±0.08) mSv and (1.07±0.05) mSv (P<0.01), respectively. SNR of 70 kV scan was significantly lower either, which were 16.53±5.87 and 18.19±6.07 (P<0.05), respectively. Stenosis degree of 630 coronary segments were evaluated, in which 608 (96.5%) were consistent between 70 kV and 100 kV scan. Bland-Altman analysis revealed a 95% confidence interval (CI) between 15% and 30% for coronary stenosis between the two groups. Conclusion: CCTA of 70 kV tube voltage significantly reduces radiation dose, while showing optimal consistent categorization for coronary stenosis to 100 kV scan. However, variability exists between 70 kV and 100 kV scans for precise quantification of coronary stenosis.