应用磁共振4D flow成像对正常颅内前循环动脉血流动力学参数定量评估的可重复性研究

Reproducibility of quantitative flow assessment of intracranial arteries of anterior cerebral circulation of healthy subjects using 4D flow imaging

目的探讨应用磁共振4D flow成像对正常颅内前循环动脉的血流动力学状态进行定量评估的可重复性。方法收集正常志愿者4例,对每名志愿者的颅内Willis环区域分别进行两次4D flow成像,应用4D flow图像后处理软件测量计算正常志愿者双侧颈内动脉(internal carotid artery,ICA)入颅段、虹吸段、末端、双侧大脑中动脉(middle cerebral artery,MCA)起始部及近段、大脑前动脉(anterior cerebral artery,ACA)起始部(每例取双侧共12个位置)的血流动力学参数,比较两次扫描的平均血管面积、平均及最大血流速度、平均及最大瞬时血流量。生成血流矢量图、流线图及粒子追踪图显示颅内前循环大动脉的血流动力学状态。结果 4名正常志愿者两次颅内Willis环血流参数比较显示,ICA虹吸段左侧最大血流速度及右侧各项血流动力学参数两次扫描之间的差异有统计学意义;ICA入颅段、MCA及ACA起始部双侧及MCA近段右侧最大血流速度之间的差异有统计学意义;MCA近段双侧平均血管面积、ACA起始部左侧平均血管面积及平均血流速度之间的差异有统计学意义。其中一名志愿者的心率两次之间有较大变化,两次的最大血流速度之间存在明显区别。另外,在针对不同部位的分析中发现,颈动脉虹吸段位置两次测量的最大血流速度之间存在较明显区别。结论应用磁共振4D flow成像对颅内动脉血流速度的评估的可重复性较好,对于不同心率状态下以及血流状态复杂部位的血流动力学评估,4D flow成像测量的可重复性可能还需要进一步验证。

Objective To investigate the reproducibility of quantitative flow assessment of healthy subjects using 4D flow imaging.Methods Four healthy volunteers were enrolled in this study.Four￣dimensional flow magnetic resonance(MR)imaging were acquired and rescanned for circle of Willis using the same protocol and parameters.The flow data were post￣processed with a prototype flow analysis software 4D Flow.The hemodynamic parameters at the biateral locations including the inlet of the intracranial portion of the internal carotid artery(ICA),the siphon of the ICA,the distal segment of the ICA,the beginning and the proximal segment of the middle cerebral artery(MCA),and the proximal segment of the anterior cerebral artery(ACA)were calculated.The average vessel area,average velocity,maximum flow velocity,and average net flow rate obtained from the first imaging and rescanned imaging were compared.Velocity vectors,streamlines,and particle traces maps were visualized.Results The comparison of hemodynamic parameters showed that significant difference was found in all parameters of right ICA(RICA)siphon,the maximum flow velocity of left ICA(LICA)siphon,bilateral ICA inlet segment,the beginning of bilateral MCA and ACA,and the proximal segment of right MCA,as well as the average area of the proximal segment of bilateral MCA and the beginning of left ACA,and the average velocity of the beginning of left ACA between two scanned images.In one subject,the heartbeats of two scans showed obvious change,and the maximum flow velocity was found to vary obviously.In the siphon segment of ICA,it was also found that there was intense variety in maximum flow velocity between two examinations.Conclusion The reproducibility of 4D flow imaging in quantitative flow assessment of intracranial arteries was acceptable.However,the reproducibility of 4D flow imaging will need further confirmation under different heartbeats conditions and for locations with complex hemodynamics status in future studies.