Liu Jian, Yu Yong, Zhu Chenqi, Zhang Yu
People's Hospital, Peking University, Beijing, P. R. China.
School of Aerospace Engineering, Beijing Institute of Technology, Beijing, P. R. China.
Proc Inst Mech Eng H. 2021 Sep;235(9):1058-1068. doi: 10.1177/09544119211016912. Epub 2021 May 13.
The finite volume method (FVM)-based computational fluid dynamics (CFD) technology has been applied in the non-invasive diagnosis of coronary artery stenosis. Nonetheless, FVM is a time-consuming process. In addition to FVM, the lattice Boltzmann method (LBM) is used in fluid flow simulation. Unlike FVM solving the Navier-Stokes equations, LBM directly solves the simplified Boltzmann equation, thus saving computational time. In this study, 12 patients with left anterior descending (LAD) stenosis, diagnosed by CTA, are analysed using FVM and LBM. The velocities, pressures, and wall shear stress (WSS) predicted using FVM and LBM for each patient is compared. In particular, the ratio of the average and maximum speed at the stenotic part characterising the degree of stenosis is compared. Finally, the golden standard of LAD stenosis, invasive fractional flow reserve (FFR), is applied to justify the simulation results. Our results show that LBM and FVM are consistent in blood flow simulation. In the region with a high degree of stenosis, the local flow patterns in those two solvers are slightly different, resulting in minor differences in local WSS estimation and blood speed ratio estimation. Notably, these differences do not result in an inconsistent estimation. Comparison with invasive FFR shows that, in most cases, the non-invasive diagnosis is consistent with FFR measurements. However, in some cases, the non-invasive diagnosis either underestimates or overestimates the degree of stenosis. This deviation is caused by the difference between physiological and simulation conditions that remains the biggest challenge faced by all CFD-based non-invasive diagnostic methods.
基于有限体积法（FVM）的计算流体动力学（CFD）技术已应用于冠状动脉狭窄的无创诊断。尽管如此，有限体积法是一个耗时的过程。除了有限体积法，格子玻尔兹曼方法（LBM）也用于流体流动模拟。与求解纳维-斯托克斯方程的有限体积法不同，格子玻尔兹曼方法直接求解简化的玻尔兹曼方程，从而节省计算时间。在本研究中，对12例经CTA诊断为左前降支（LAD）狭窄的患者使用有限体积法和格子玻尔兹曼方法进行分析。比较了有限体积法和格子玻尔兹曼方法为每位患者预测的速度、压力和壁面剪应力（WSS）。特别地，比较了表征狭窄程度的狭窄部位平均速度与最大速度之比。最后，应用LAD狭窄的金标准——有创血流储备分数（FFR）来验证模拟结果。我们的结果表明，格子玻尔兹曼方法和有限体积法在血流模拟中是一致的。在高度狭窄区域，这两种求解器的局部流动模式略有不同，导致局部壁面剪应力估计和血流速度比估计存在微小差异。值得注意的是，这些差异不会导致估计不一致。与有创FFR的比较表明，在大多数情况下，无创诊断与FFR测量结果一致。然而，在某些情况下，无创诊断要么低估要么高估了狭窄程度。这种偏差是由生理条件和模拟条件之间的差异引起的，这仍然是所有基于CFD的无创诊断方法面临的最大挑战。
