Objective Experiments were carried out to test the hypothesis that using prospective ECG-triggering acquisition, also called "step-and-shoot" (SAS) mode on head can reduce radiation dose without compromising image quality compared with using conventional dual energy CTA scan. Methods Eighty-four patients with clinically suspected or confirmed cerebrovascular disease were randomly divided into 2 groups: Group A (43 patients underwent prospective ECG-triggering combined with "step-and-shoot" acquisition) and Group B (41 patients, underwent conventional dual-energy scanning). Images were reconstructed at 60% R-R interval. All images were processed on workstation and the image qualities of these images were scored by two experienced radiologists. These image scores and radiation doses used in each group were subjected to statistical analysis using the paired-sample t-test. Results The image quality score for group A was 4.7±0.5 with a good rate of 98%(42/43) and 4.7±0.5 for group B with a rate of 98%(40/41). The difference in the scores of image quality, between two groups was not statistically significant (P=0.903). The average effective dose was(0.216±0.01) mSv in group A and(0.541±0.04) mSv in group B. T-test results showed that the effective dose for the two groups were statistical different(P=0.000). Conclusion Compared with conventional mode, SAS mode with a narrow R-R interval can be applied to perform cerebral CTA with a dose reduction by 60%and produced similar image quality.%目的：探讨双源CT前瞻性心电触发序列（SAS）扫描模式，脑血管成像的图像质量及辐射剂量。方法将84例临床怀疑或确诊的脑血管性病变的患者按照随机数字表法分为A，B 2组。 A组43例行前瞻性心电触发序列模式的脑血管CTA（SAS-CTA）扫描，采集期相：应用60%R-R间期的心电图（ECG）演示模式；B组41例行双能量CTA（DE-CTA）扫描。对2组患者脑血管CTA分别做图像后处理，应用两独立样本t检验方法统计分析图像质量评分及辐射剂量，并评价优良率。结果 A组图像质量评分为4.7±0.5，优良率达98%（42/43），B组图像质量评分为4.7±0.5，优良率达98%（40/41），2组间图像质量评分差异无统计学意义（t=0.443，P=0.903）。 A组扫描范围为（138.5±2.9） mm，B组为（139.3±0.8） mm，2组间扫描范围差异无统计学意义（t=0.685，P=0.074）。A组平均有效剂量及平均曝光时间分别为（0.216±0.01） mSv和（0.92±0.11） s， B组分别为（0.541±0.04） mSv和（2.33±0.10） s，2组间平均有效剂量及平均曝光时间差异有统计学意义（t=-53.086，t=0.902，P=0.000）。 SAS-CTA有效辐射剂量与DE-CTA比较降幅达到60.01%。结论前瞻性心电触发序列模式应用于脑血管成像，可在保证图像质量的同时显著降低辐射剂量。
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