Northwestern Polytechnical University Xian, School of Electronics, Xian, China.
Phys Med. 2011 Jul;27(3):169-76. doi: 10.1016/j.ejmp.2010.07.002. Epub 2010 Aug 8.
The exact knowledge of the blood vessel geometry plays an important role, not only in clinical applications (stroke diagnosis, detection of stenosis), but also for deeper analysis of hemodynamic functional data, such as fMRI. Such vessel geometries can be obtained by different MR angiographic measurements. It is shown that simulations using computational fluid dynamics (CFD) can be used to validate the vessel geometry, automatically reconstructed from time of flight (TOF) angiograms or phase contrast angiography (PC-MRA) data. CFD simulations are based on PC-MRA data, since these data contain additionally rheological information (phases) besides merely amplitudes as is the case for TOF measurements. Parts of the rat brain vessel system are carefully modeled consisting of a main tube and second order branches. By analyzing velocity changes up and downstream of bifurcations, it is shown that CFD can be used to help detecting missing vessels in the TOF based reconstruction. It is demonstrated by artificially deleting a branch from the reconstruction and compared the flow in both resulting CFD simulations. Finally the simulations help to understand the effects of secondary branches on the flow in the main tube. The aim of this study is to compare the measured (PCA) flow data with the CFD simulation results, based on the vessel geometry gained from the PCA image using an in house reconstruction algorithm. If a more accurate simulation method is found and if in principal the simulation matches the PCA data, it might be possible to deduct that in cases where the measured data varies from the CFD simulation, the reconstruction is not complete, i.e. branches are missing or wrong branches were reconstructed.
血管几何形状的精确知识不仅在临床应用（中风诊断、狭窄检测）中起着重要作用，而且对于血流动力学功能数据（如 fMRI）的深入分析也起着重要作用。这些血管几何形状可以通过不同的磁共振血管造影测量来获得。已经表明，使用计算流体动力学（CFD）的模拟可以用于验证从飞行时间（TOF）血管造影或相位对比血管造影（PC-MRA）数据自动重建的血管几何形状。CFD 模拟基于 PC-MRA 数据，因为这些数据除了幅度之外还包含流变学信息（相位），而 TOF 测量则仅包含幅度。仔细模拟了大鼠脑血管系统的一部分，包括主管道和二级分支。通过分析分叉处上下游的速度变化，可以看出 CFD 可用于帮助检测基于 TOF 的重建中缺失的血管。通过从重建中人工删除一个分支并比较两个结果的 CFD 模拟，可以证明这一点。最后，模拟有助于理解二级分支对主管道中流动的影响。本研究的目的是基于 PCA 图像中使用内部重建算法获得的血管几何形状，将测量（PCA）流量数据与 CFD 模拟结果进行比较。如果找到更准确的模拟方法，并且原则上模拟与 PCA 数据匹配，则有可能推断出在测量数据与 CFD 模拟结果不同的情况下，重建不完整，即分支缺失或重建了错误的分支。
