In vitro validation of computational fluid dynamic simulation in human proximal airways with hyperpolarized ³He magnetic resonance phase-contrast velocimetry

Abstract

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 (3)He 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.

Multiscale Modeling of the Respiratory Tract

“…At the peak of inspiration we obtain a typical M-shape after the first bifurcation (see [13] where steady state simulations and experiments are performed on the same geometry).…”

“…2) were constructed using INRIA GHS3D mesh generator [16]. The original 3D surface geometry is the same used in [14,13], and it was reconstructed, from CRT medical images, using a marching cube-base adaptive approach (see [14] for more details) .…”

Multi-scale computational models of the airways to unravel the pathophysiological mechanisms in asthma and chronic obstructive pulmonary disease (AirPROM)

“…In previous studies, this concept has been applied to long-acting b 2 -agonists (LABAs) [32], a combination of a LABA and an inhaled corticosteroid [30], a short-acting anticholinergic, a short-acting b 2 -agonist [31] and non-invasive ventilation [33]. The concept has been validated using gamma scintigraphy [34], single-photon emission computed tomography [35] and HP MRI [36]. Within AirPROM, state-of-the-art software (MIMICS, Materialise NV, Belgium; AIRWAYS, Institut Telecom, France) is being developed to enable automatic extraction of the morphological properties of airways and lobes from patient CT data.…”

Measurement of gas transport kinetics in high‐frequency oscillatory ventilation (HFOV) of the lung using hyperpolarized 3He magnetic resonance imaging

“…Particularly, using HP 3 He MRI can the distribution and efficiency of ventilation as well as gas flow velocity profiles be visualized and evaluated (9). Hyperpolarization of 3 He enables a nuclear magnetization of factor 10 5 higher in comparison with the Boltzmann equilibrium in static magnetic fields on the order of 1T and, thus, allows for unbeatable physical sensitivity of MRI measurements using gaseous imaging agents.…”