A quasi-3D wire approach to model pulmonary airflow in human airways
A quasi-3D wire approach to model pulmonary airflow in human airways
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DOI：
10.1002/cnm.2838
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发表时间：
2017-07-01
影响因子：
2.1
通讯作者：
Walenga, Ross
中科院分区：
文献类型：
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作者：
Kannan, Ravishekar;Chen, Z. J.;Walenga, Ross
用于模拟人体呼吸道内气流的模型可以是0维隔室模型或全三维(3D)计算流体动力学(CFD)模型。在前者中，将气道视为隔间，在几个假设的情况下执行计算，从而生成低保真解。CFD方法表现出极高的保真度，因为解是通过在生理上一致的几何形状中求解守恒方程来获得的。然而，CFD模型(1)需要数百万个自由度来精确描述几何形状并减少离散化误差，(2)存在收敛问题，(3)需要几天来模拟几个呼吸周期。在本文中，我们提出了一种新颖的、快速运行的、健壮的准三维线模型，用于模拟人肺气道中的气流。金属丝网是通过将高保真的肺气道面网格收缩到具有明确定义的半径的连接金属丝系统来获得的。然后在每根导线中求解守恒方程。这些金属丝网具有大约O(1000)个自由度，因此比它们的CFD对应网格快3000到25000倍。3D空间性质也被保留，因为这些导线收缩出实际的肺STL表面。两种方法之间的压力读数有微小差异(最大误差=15%)。总体而言，此公式快速且可靠，允许几何变化，并提供高保真解决方案。因此，这种方法对于更复杂的问题有很大的潜力，包括对狭窄/病变的肺切片进行建模，以及通过参数反演来校准肺血流阻力。
The models used for modeling the airflow in the human airways are either 0-dimensional compartmental or full 3-dimensional (3D) computational fluid dynamics (CFD) models. In the former, airways are treated as compartments, and the computations are performed with several assumptions, thereby generating a low-fidelity solution. The CFD method displays extremely high fidelity since the solution is obtained by solving the conservation equations in a physiologically consistent geometry. However, CFD models (1) require millions of degrees of freedom to accurately describe the geometry and to reduce the discretization errors, (2) have convergence problems, and (3) require several days to simulate a few breathing cycles. In this paper, we present a novel, fast-running, and robust quasi-3D wire model for modeling the airflow in the human lung airway. The wire mesh is obtained by contracting the high-fidelity lung airway surface mesh to a system of connected wires, with well-defined radii. The conservation equations are then solved in each wire. These wire meshes have around O(1000) degrees of freedom and hence are 3000 to 25 000 times faster than their CFD counterparts. The 3D spatial nature is also preserved since these wires are contracted out of the actual lung STL surface. The pressure readings between the 2 approaches showed minor difference (maximum error = 15%). In general, this formulation is fast and robust, allows geometric changes, and delivers high-fidelity solutions. Hence, this approach has great potential for more complicated problems including modeling of constricted/diseased lung sections and for calibrating the lung flow resistances through parameter inversion.