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1U2R2M, Unité de Recherche en Résonance Magnétique Médicale, CNRS, Univ Paris-Sud, Le Kremlin-Bicêtre; 2Centre de Recherche Claude Delorme (Air Liquide Research Center), Les Loges-en-Josas; 3Laboratoire Jacques Louis Lions, CNRS UMR 7598, Université Paris VI, Paris; 4Biomécanique Cellulaire et Respiratoire, Institut National de la Santé et de la Recherche Médicale UMR651, Université Paris XII, Créteil, France
Submitted 22 December 2005 ; accepted in final form 4 February 2007
Computational fluid dynamics (CFD) and magnetic resonance (MR) gas velocimetry were concurrently performed to study airflow in the same model of human proximal airways. Realistic in vivo-based human airway geometry was segmented from thoracic computed tomography. The three-dimensional numerical description of the airways was used for both generation of a physical airway model using rapid prototyping and mesh generation for CFD simulations. Steady laminar inspiratory experiments (Reynolds number Re = 770) were performed and velocity maps down to the fourth airway generation were extracted from a new velocity mapping technique based on MR velocimetry using hyperpolarized 3He gas. Full two-dimensional maps of the velocity vector were measured within a few seconds. Numerical simulations were carried out with the experimental flow conditions, and the two sets of data were compared between the two modalities. Flow distributions agreed within 3%. Main and secondary flow velocity intensities were similar, as were velocity convective patterns. This work demonstrates that experimental and numerical gas velocity data can be obtained and compared in the same complex airway geometry. Experiments validated the simulation platform that integrates patient-specific airway reconstruction process from in vivo thoracic scans and velocity field calculation with CFD, hence allowing the results of this numerical tool to be used with confidence in potential clinical applications for lung characterization. Finally, this combined numerical and experimental approach of flow assessment in realistic in vivo-based human airway geometries confirmed the strong dependence of airway flow patterns on local and global geometrical factors, which could contribute to gas mixing.
tracheobronchial tree; patient-based geometry; airway velocity profiles
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