目的 探讨减少对比剂注射时 间、优化对比剂用量在256排螺旋CT冠 状动脉成像检查(coronary computed tomographic angiography，CCTA)中 的临床应用价值。方法 收集冠状动脉 成像检查100例患者，随机分为A组(注 射时间10s)50例、B组(注射时间8s)50 例，两组选用相同对比剂。在升主动脉 根部及冠状动脉主干(右冠状动脉RCA、 左冠状动脉主干LM、左前降支LAD、左 回旋支LCX)起始处管腔内及邻近脂肪组 织内放置感兴趣区，测量CT值和标准差 (standard deviation, SD)。比较主动脉 及各冠状动脉主干内CT值及血管对比噪声 比(contrast-to-noise ratio，CNR)， 使用独立样本t检验比较。采用5分法(1 分最差，5分最好)主观比较两组图像质 量，使用wilcoxon符号等级检验比较。 记录并比较对比剂用量和有效辐射剂量 (effective dose，ED)。结果 两组间ED 差异有统计学意义(P＜0.05)，A组碘对 比剂用量为(46.16±6.90)mL，B组碘对 比剂用量为(35.74±4.81)mL，减少约 22.57%。两组在主动脉根部、RCA、LM、 LAD、LCX起始处CT值、CNR无统计学差异 (P＞0.05)，平均主观评分两组间无统计 学差异（P>0.05）。结论 在256排螺旋CT 冠状动脉成像检查中，选择8s对比剂注射 时间能够有效减少对比剂的用量，而图像 质量不受影响。

Objective To investigate the clinical value by reducing contrast material injection time and optimizing the dosage on the quality of image of coronary CT in 256-row spiral CT scanner. Methods A total of 100 consecutive patients who had done coronary CTA were divided into A group (injection time 10s,50 cases)and B group(injection time 8s,50m cases) randomly, which use the same contrast agent and the injection velocity. We place the area of interest in start section of the ascending aortic root cavity and main coronary artery(right coronary artery, left coronary artery, left anterior descending branch of coronary artery, left circumflex artery) and adjacent tissue, measuring the CT value and standard deviation (SD). Compared the CT value, the noise ratio(CNR) of the aortic and coronary artery by using paired T-test. Subjectively compared the coronary CT image quality (CCTA) between two groups through using 5 points methods(5 is the best,1 is the worst) and wilcoxon symbols rank test. Contrast dose and radiation dose were measured and calculated. Results There are no statistically significance of ED between the two groups (P=0.50), the ED of group A and group B was (46.16±6.90)mL, (35.74±4.81) mL respectively. The aortic root,right coronary artery, left main coronary artery, the left anterior descending branch of coronary artery, the start section of left circumflex artery of CT value and vascular contrast to noise ratio (CNR) in two groups has no difference (P>0.05). Conclusion In 256-slice spiral CT coronary angiography, the choice of 8s contrast agent injection time can effectively reduce the amount of contrast agent, but the image quality is not affected.