Tateshima Satoshi, Grinstead John, Sinha Shantanu, Nien Yih-lin, Murayama Yuichi, Villablanca J Pablo, Tanishita Kazuo, Viñuela Fernando
Department of Radiological Sciences, University of California at Los Angeles Medical Center, Los Angeles, California 90095-1721, USA.
J Neurosurg. 2004 Jun;100(6):1041-8. doi: 10.3171/jns.2004.100.6.1041.
The aim of this study was to evaluate the feasibility of complex intraaneurysmal flow visualization with the currently available phase-contrast magnetic resonance (MR) imaging modality.
A geometrically realistic in vitro aneurysm model, in which detailed flow velocity analysis had already been conducted using laser Doppler velocimetry was used for this in vitro hemodynamic simulation, so that the results of phase-contrast velocity measurements could be compared with the previous reliable results. On a 1.5-tesla unit, three orthogonal components of velocity were obtained using a standard two-dimensional fast low-angle shot flow quantification sequence. Three-dimensional (3D) intraaneurysmal flow structures recorded during one cardiac cycle were depicted in one midsagittal and three axial cross-sectional planes with the aid of gray scale phase-contrast velocity maps. Isovelocity contour maps and secondary flow vectors were also created based on the phase-contrast velocity maps by using MATLAB software. The isovelocity contours in those three axial sections could demonstrate the shapes of inward and outward flow areas and their alternation over one cardiac cycle. The secondary flow vectors demonstrated twin vortices within the outward flow area adjacent to the boundary layer of inward and outward flow in all axial planes.
The phase-contrast MR imaging method was able to depict the complex 3D intraaneurysmal flow structures in the in vitro aneurysm model. Detailed 3D intraaneurysmal flow information will be obtainable in vivo after improvements are made in spatial resolution, which is expected in the near future. The capability to visualize intraaneurysmal flow structures directly with the use of noninvasive MR imaging technology will have a positive impact on future clinical practice.
本研究旨在评估利用现有相衬磁共振成像方式进行复杂动脉瘤内血流可视化的可行性。
使用一个几何逼真的体外动脉瘤模型，该模型已通过激光多普勒测速仪进行了详细的流速分析，用于本次体外血流动力学模拟，以便将相衬速度测量结果与先前可靠结果进行比较。在一台1.5特斯拉设备上，使用标准二维快速低角度激发血流定量序列获取速度的三个正交分量。借助灰度相衬速度图，在一个矢状中平面和三个轴向横截面中描绘一个心动周期内记录的三维动脉瘤内血流结构。还使用MATLAB软件基于相衬速度图创建等速轮廓图和二次流矢量。这三个轴向截面中的等速轮廓可展示向内和向外流动区域的形状及其在一个心动周期内的交替变化。二次流矢量在所有轴向平面中均显示出在与向内和向外流动边界层相邻的向外流动区域内的双涡旋。
相衬磁共振成像方法能够在体外动脉瘤模型中描绘复杂的三维动脉瘤内血流结构。在空间分辨率方面进行改进后，有望在体内获取详细的三维动脉瘤内血流信息，这在不久的将来是可以实现的。利用无创磁共振成像技术直接可视化动脉瘤内血流结构的能力将对未来临床实践产生积极影响。
