核磁共振成像研究正常人主动脉瓣上血流速度分布的临床初探

目的:应用核磁共振成像(MRI)对国内正常人升主动脉内特定横截面上的血流速度分布进行研究,以探讨其普遍规律。方法:13例健康志愿者,均为窦性心律。应用1.5T核磁共振仪在升主动脉内、距主动脉瓣环0.5、1.0和2.0个瓣环直径处,垂直于升主动脉的层面进行成像扫描和血流参数的测量。应用血流分析软件对测得的数据进行后处理,并读取每个研究对象的核磁共振扫描图像,最后作出相应各个时相血流速度的三维图形。结果:在所有13个测试者中,在心脏收缩射血时,均有很强的信号缺失,主要分布于升主动脉外侧弯曲部分。阶段对比测量显示1.0D层面是研究升主动脉内血流速度分布的理想层面。自收缩射血的加速期至舒张早期,前向最大速度血流的偏斜呈现出从后-右-前的"右手螺旋"现象。在收缩射血的加速期和峰期,绝大部分研究对象未出现返流。结论:本研究初步探索应用MRI研究国内正常人升主动脉内特定横截面上的血流速度分布。为使这项技术成为一种安全、无创的评价人体主动脉瓣上血流速度分布的工具提供依据。

Using magnetic resonance imaging to study the velocity distribution of blood flow downstream of the aortic valve in normal human

Objective：Using magnetic resonance imaging（MRI） technique study the velocity distribution of blood flow in a certain transverse section downstream of the aortic valve in normal human.Method：Thirteen normal human, all with sinous rhythm, were enrolled in this study. MRI-scanning was performed on a 1.5 Tesla scanner. Blood measurements were performed in the planes perpendicular to the ascending aorta half, one and two valve ring diameters downstream of the aortic annulus. The data acquired were analyzed qualitatively, and three-dimensional surface plots of velocity field of all subjects were displayed and analyzed qualitatively.Result：In all 13 subjects, there was significant signal loss in systole phase and the signal loss mainly distributed in lateral curve part of ascending aorta. The plane one valve ring diameters downstream of the aortic annulus was the ideal plane to study the velocity distribution. From systolic acceleration phase to early diastolic phase, the highest velocity skewed from back to right and to anterior, just like right hand helix. In systolic acceleration and peak phase, no regurgitation was seen in most subjects.Conclusion：Display and interpretation of blood velocity data obtained downstream of the aortic annulus in normal subjects is feasible using the MRI technique. With the characteristic of safe and non-invasive, MRI technique has significant potential for function evaluation of heart valves in vivo.