3D 相位对比 MRI 在人类气道模型中的应用：稳态吸气流动计算流体动力学模拟的验证。
3D phase contrast MRI in models of human airways: Validation of computational fluid dynamics simulations of steady inspiratory flow.
机构信息
POLARIS, Unit of Academic Radiology, Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, UK.
School of Engineering and Centre for Scientific Computing, University of Warwick, Coventry, UK.
出版信息
J Magn Reson Imaging. 2018 Nov;48(5):1400-1409. doi: 10.1002/jmri.26039. Epub 2018 Apr 6.
BACKGROUND
Knowledge of airflow patterns in the large airways is of interest in obstructive airways disease and in the development of inhaled therapies. Computational fluid dynamics (CFD) simulations are used to study airflow in realistic airway models but usually need experimental validation.
PURPOSE
To develop MRI-based methods to study airway flow in realistic 3D-printed models.
STUDY TYPE
Case control.
PHANTOM
Two 3D-printed lung models.
FIELD STRENGTH/SEQUENCE: 1.5-3T, flow MRI.
ASSESSMENT
Two human airway models, respectively including and excluding the oral cavity and upper airways derived from MR and CT imaging, were 3D-printed. 3D flow MRI was performed at different flow conditions corresponding to slow and steady airflow inhalation rates. Water was used as the working fluid to mimic airflow. Dynamic acquisition of 1D velocity profiles was also performed at different locations in the trachea to observe variability during nonsteady conditions.
STATISTICAL TESTS
Linear regression analysis to compare both flow velocity fields and local flow rates from CFD simulations and experimental measurement with flow MRI.
RESULTS
A good agreement was obtained between 3D velocity maps measured with flow MRI and predicted by CFD simulations, with linear regression R-squared values ranging from 0.39 to 0.94 when performing a pixel-by-pixel comparison of each velocity component. The flow distribution inside the lung models was also similar, with average slope and R-squared values of 0.96 and 0.99, respectively, when comparing local flow rates assessed at different branching locations. In the model including the upper airways, a turbulent laryngeal jet flow was observed with both methods and affected remarkably the velocity profiles in the trachea.
DATA CONCLUSION
We propose flow MRI using water as a surrogate fluid to air, as a validation tool for CFD simulations of airflow in geometrically realistic models of the human airways.
LEVEL OF EVIDENCE
3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1400-1409.
背景
了解大气道中的气流模式对阻塞性气道疾病和吸入疗法的发展很有意义。计算流体动力学（CFD）模拟用于研究真实气道模型中的气流，但通常需要实验验证。
目的
开发基于 MRI 的方法来研究真实 3D 打印模型中的气道流动。
研究类型
病例对照。
模型
两个 3D 打印的肺模型。
磁场强度/序列：1.5-3T，流动 MRI。
评估
分别从 MRI 和 CT 成像中获得的包含和不包含口腔和上呼吸道的两个人类气道模型被 3D 打印。在不同的流动条件下进行 3D 流动 MRI，对应于缓慢和稳定的气流吸入率。使用水作为工作流体来模拟气流。还在气管的不同位置进行了 1D 速度剖面的动态采集，以观察非稳态条件下的可变性。
统计检验
线性回归分析比较 CFD 模拟和流动 MRI 实验测量的两个流速场和局部流速。
结果
流动 MRI 测量的 3D 速度图与 CFD 模拟预测值之间得到了很好的一致性，当对每个速度分量进行逐像素比较时，线性回归 R 平方值范围为 0.39 至 0.94。肺模型内的流量分布也相似，当比较在不同分支位置评估的局部流量时，平均斜率和 R 平方值分别为 0.96 和 0.99。在上呼吸道包括的模型中，两种方法均观察到喉湍流射流，这显著影响了气管中的速度剖面。
数据结论
我们提出使用水作为空气的替代流体的流动 MRI，作为 CFD 模拟在人体气道的几何真实模型中气流的验证工具。
证据水平
3 技术功效：第 2 阶段 J. Magn. Reson. Imaging 2018;47:1400-1409.
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