胸部增强磁共振血管造影扫描时机的选择

Scan timing in thoracic enhanced MR angiography

目的:探讨不同流速时磁共振对比剂在胸部血管内的血流动力学分布特征,为把握胸部增强磁共振血管造影的最佳扫描时机提供参考数据。方法:无明显胸部疾病的自愿者50例,按对比剂流速2、3和4 ml/s随机分3组,用2 ml对比剂进行试验性注射,均经肘静脉注射。绘制各靶血管的动态强化曲线,测量对比剂到达时间、峰值时间、肺循环时间等。结果:2 ml/s流速时,对比剂到达肺动脉、肺静脉和主动脉的时间分别为(5.17±1.47)、(8.16±1.09)和(10.17±0.75)s;3 ml/s流速时,分别为(4.43±1.27)、(7.71±2.69)和(8.71±1.60)s;4 ml/s时,分别为(4.33±1.16)、(8.35±2.15)和(8.20±1.84)s,呈现出高流速略快于低流速的趋势;强化峰值持续时间均在15～20 s;肺循环时间2 ml/s组为(3.50±0.55)s,3 ml/s组为(3.43±0.54)s,4 ml/s组(3.67±0.58)s,各组间无显著差异(P>0.05)。结论:(1)对比剂到达靶血管时间肺动脉为3～6 s,肺静脉为7～11 s,主动脉为8～12 s;(2)15～20 s的强化峰值持续时间基本可以保证大多数快速序列的扫描;(3)肺实质成像的数据采集时间最好短至5 s以下才能比较理想。

Objective: To study the hemodynamics distribution of contrast material in thoracic vessels, providing references of contrast medium in contrast-enhanced MR angiography. Methods: Totally 50 volunteers without apparent thoracic disease underwent breath-hold MR scanning on a 1. 5T system by using 2 ml contrast material. The patients were assigned to 3 groups according to flow rate(2 ml/s, 3 ml/s and 4 ml/s) ,dynamic signal intensity-time curve were plotted automatically, contrast travel time , peak value sustaining time and the pulmonary circulation period were calculated respectively. Results: All patients were injected through cubitus veins. In 2 ml/s group, the contrast travel times to pulmonary artery, pulmonary vein and aorta were (5. 17±1. 47) s, (8. 16±1. 09) s and (10. 17±0. 75) s respectively;In 3 ml/s group, it was (4. 43±1.27) s,(7. 71 ± 2. 69) s and (8. 71±1. 60) s respectively ;In 4 ml/s group.it was (4. 33±1. 16) s, (8. 35±2. 15) sand (8.20±1. 84) s;The peak value sustaining time was around 15-20 s in all groups,the pulmonary circulation time was (3. 50±0. 55) s in 2 ml/s group,(3. 43±0. 54) s in 3 ml/s group and (3. 67±0. 58) s in 4 ml/s group, no significant difference was found between the 3 groups (P>0. 05). Conclusion: The scan delay time of CEMRA should be 3-6 s for pulmonary arteries, 7-11 s for pulmonary veins and 8-12 s for aortas; The 15-20 s peak value sustaining time can fulfill the most fast 3D MRA sequences. Scanning time should be less than 5 s if the imaging target is pulmonary parenchyma.