Advances in quantitative computed tomography (CT) has provided methods to assess the detailed structure of the pulmonary airways and parenchyma, providing the means of applying computational fluid dynamics-based modeling to better understand subject-specific differences in structure-to-function relationships. Most of the previous numerical studies, seeking to predict patterns of inhaled particle deposition, have considered airway geometry and regional ventilation derived from static images. Because geometric alterations of the airway and parenchyma associated with regional ventilation may greatly affect particle transport, we have sought to investigate the effect of rigid vs. deforming airways, linear vs. nonlinear airway deformations, and step-wise static vs. dynamic imaging on particle deposition with varying numbers of intermediate lung volume increments. Airway geometry and regional ventilation at different time points were defined by four-dimensional (space and time) dynamic or static CT images. Laminar, transitional, and turbulent air flows were reproduced with a three-dimensional eddy-resolving computational fluid dynamics model. Finally, trajectories of particles were computed with the Lagrangian tracking algorithm. The results demonstrated that static-imaging-based models can contribute 7% uncertainty to overall particle distribution and deposition primarily due to regional flow rate (ventilation) differences as opposed to geometric alterations. The effect of rigid vs. deforming airways on serial distribution of particles over generations was significantly smaller than reported in a previous study that used the symmetric Weibel geometric model with smaller flow rate. Rigid vs. deforming airways were also shown to affect parallel particle distribution over lobes by 8% and the differences associated with use of static vs. dynamic imaging was 18%. These differences demonstrate that estimates derived from static vs. dynamic imaging can significantly affect the assessment of particle distribution heterogeneity. The effect of linear vs. nonlinear airway deformations was within the uncertainty due to mesh size.

中文翻译：

---

静态与动态成像对基于 CT 的人体中央气道数值模型中粒子传输的影响

定量计算机断层扫描 (CT) 的进步提供了评估肺气道和实质详细结构的方法，提供了应用基于计算流体动力学的建模的方法，以更好地了解结构与功能关系中特定主题的差异。以前的大多数数值研究旨在预测吸入颗粒沉积的模式，已经考虑了从静态图像得出的气道几何形状和区域通风。由于与区域通气相关的气道和实质的几何变化可能会极大地影响颗粒传输，因此我们试图研究刚性与变形气道、线性与非线性气道变形以及逐步静态与非连续性气道变形的影响。具有不同数量的中间肺容积增量的颗粒沉积的动态成像。不同时间点的气道几何形状和区域通气由四维（空间和时间）动态或静态 CT 图像定义。层流、过渡和湍流空气流使用三维涡旋解析计算流体动力学模型再现。最后，使用拉格朗日跟踪算法计算粒子的轨迹。结果表明，主要由于区域流速（通风）差异而不是几何变化，基于静态成像的模型可以对整体颗粒分布和沉积贡献 7% 的不确定性。刚性对比的效果 几代粒子在连续分布上的气道变形明显小于先前使用对称 Weibel 几何模型和较小流速的研究中报告的。刚性气道与变形气道也显示出对叶上平行粒子分布的影响为 8%，与使用静态与动态成像相关的差异为 18%。这些差异表明，从静态与动态成像得出的估计值会显着影响粒子分布异质性的评估。由于网格尺寸，线性与非线性气道变形的影响在不确定性范围内。变形气道也被证明会影响 8% 的肺叶上的平行粒子分布，并且与使用静态和动态成像相关的差异为 18%。这些差异表明，从静态与动态成像得出的估计值会显着影响粒子分布异质性的评估。由于网格尺寸，线性与非线性气道变形的影响在不确定性范围内。变形气道也被证明会影响 8% 的肺叶上的平行粒子分布，并且与使用静态和动态成像相关的差异为 18%。这些差异表明，从静态与动态成像得出的估计值会显着影响粒子分布异质性的评估。由于网格尺寸，线性与非线性气道变形的影响在不确定性范围内。