目的：探讨利用智能触发技术在选择相同触发位置、不同阈值时小剂量对比剂肺动脉ＣＴ成像效果，以期提高肺动脉CTA图像质量。方法：72例接受肺动脉CTA患者随机平均分成A、B、C组，以主动脉弓平面上腔静脉为监测点，分别以50、80、110 HU作为监测阈值进行智能触发扫描，比较肺动脉主干、亚段肺动脉、静脉、主动脉强化CT值及亚段肺动脉与肺静脉强化CT值差值的差异，同时比较不同监测阈值图像之间的差异。结果：肺动脉主干、亚段肺动脉和肺静脉、主动脉强化CT值及亚段肺动脉与肺静脉强化CT值差值和不同监测阈值下等级图像差异在50 HU与其它2组有显著性差异（P<0.05），图像质量好；80 HU和110 HU两组比较除了亚段肺动、静脉CT值的差值外，其它统计量差异无统计学意义（P>0.05），图像质量较差。结论：以主动脉弓平面上腔静脉为监测点，50 HU作为触发阈值时肺动脉强化CT值最大，能获得更理想的肺动脉CTA图像。

Objective: To study the effect of angiography of the pulmonary arteries using the intelligent technology in the same trigger position, but different threshold value of low dose contrast agent, in order to improve the pulmonary CTA image quality. Methods: Seventy-two patients accepting pulmonary artery CTA were randomly divided into A, B, C group. The superior vena cava in the level of the aortic arch was the monitor position. 50, 80, 110 HU were the monitoring threshold under which the intelligent trigger scan was administered respectively. Both the difference of CT value of main pulmonary artery, segmental pulmonary artery, vein, aorta, and the difference between the subsegmental pulmonary arterial and the pulmonary venous enhancement CT value, and the differences of image quality in different monitoring threshold levels were compared finally. Results: The differences of the enhancement CT value of the main pulmonary artery, segmental pulmonary artery and pulmonary vein, aorta and subsegmental pulmonary artery and pulmonary vein and the image quality in different monitoring threshold level were significant. The 50 HU group had good image quality and superior to the other two groups(P<0.05). There were no significant difference between the 80 HU and the 110 HU groups(P>0.05) in the segmental pulmonary artery and vein. Conclusion: With superior vena cava for monitoring points in the level of the aortic arch, and by using 50 HU as the trigger threshold can obtain more ideal images.