Department of Mechanical and Environmental Informatics, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8552, Japan.
Int J Numer Method Biomed Eng. 2013 Oct;29(10):1089-103. doi: 10.1002/cnm.2562. Epub 2013 Jun 4.
In the patient-specific vascular CFD, determination of the inlet and outlet boundary conditions (BCs) is an important issue for a valid diagnosis. The 3D cine phase-contrast MRI (4D Flow) velocimetry is promising for this issue; yet, its measured velocities contain relatively large error and are not admissible as the BCs without any correction. This paper proposes a novel correction method for determining the BCs accurately using the 4D Flow velocimetry. First, we reveal that the error of the velocity measured by the 4D Flow at each measurement voxel is large but is distributed symmetrically. Secondly, our method pays attention to the incompressibility of the blood and the fact that the volume flow rate (VFR) in each vessel is constant on any cross sections. We reveal that the average of the cross-sectional VFRs integrated from many measurement voxel in each vessel is accurate despite the large error. Finally, we propose the novel correction method, which applies a smoothing to the measured velocities on each inlet or outlet boundary with a low-pass filter and then corrects them with the VFR. The results of the several phantom studies are presented to validate the accuracy of our method. A demonstrative analysis for an actual aneurysm is also presented to show the feasibility and effectiveness of our method.
在针对特定患者的血管 CFD 中，确定入口和出口边界条件（BC）是进行有效诊断的一个重要问题。3D 电影相位对比 MRI（4D Flow）速度测量在这方面很有前景；然而，其测量的速度包含较大的误差，如果不进行任何校正，就不能作为 BC 使用。本文提出了一种使用 4D Flow 速度测量值准确确定 BC 的新校正方法。首先，我们揭示了 4D Flow 在每个测量体素处测量的速度误差较大，但分布对称。其次，我们的方法注意到血液的不可压缩性，以及在任何横截面上血管内的体积流量（VFR）保持恒定的事实。我们揭示了尽管存在较大误差，但从每个血管中的许多测量体素中积分得到的平均血管横截面积 VFR 是准确的。最后，我们提出了一种新的校正方法，该方法对每个入口或出口边界上的测量速度应用低通滤波器进行平滑处理，然后使用 VFR 对其进行校正。本文还展示了几个模拟体研究的结果，以验证我们方法的准确性。此外，还展示了一个实际动脉瘤的分析案例，以说明我们方法的可行性和有效性。
