3D phase contrast MRI in models of human airways: Validation of computational fluid dynamics simulations of steady inspiratory flow

Collier, Guilhem J.; Kim, Minsuok; Chung, Yongmann M.; Wild, Jim M.

doi:10.1002/jmri.26039

Cited by 19 publications

(6 citation statements)

References 38 publications

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“…The corresponding Reynolds numbers ( Re = UD / ν ) of the LF and HF cases are Re = 350 and 2000, respectively. The flow velocities in the patient‐specific 3D printing model were measured by the flow‐sensitised phase contrast MRI technique . Three‐dimensional flow MRI measurements were performed on a 3 T MRI scanner (Philips, Ingenia, The Netherlands) with a multichannel cardiac coil during a constant flow of water ( Q L ).…”

Section: Methodsmentioning

confidence: 99%

Effect of upper airway on tracheobronchial fluid dynamics

Kim

Collier

Wild

et al. 2018

Numer Methods Biomed Eng

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The upper airways play a significant role in the tracheal flow dynamics. Despite many previous studies, however, the effect of the upper airways on the ventilation distribution in distal airways has remained a challenge. The aim of this study is to experimentally and computationally investigate the dynamic behaviour in the intratracheal flow induced by the upper respiratory tract and to assess its influence on the subsequent tributaries. Patient-specific images from 2 different modalities (magnetic resonance imaging of the upper airways and computed tomography of the lower airways) were segmented and combined. An experimental phantom of patient-specific airways (including the oral cavity, larynx, trachea, down to generations 6-8) was generated using 3D printing. The flow velocities in this phantom model were measured by the flow-sensitised phase contrast magnetic resonance imaging technique and compared with the computational fluid dynamics simulations. Both experimental and computational results show a good agreement in the time-averaged velocity fields as well as fluctuating velocity. The flows in the proximal trachea were complex and unsteady under both lower- and higher-flow rate conditions. Computational fluid dynamics simulations were also performed with an airways model without the upper airways. Although the flow near the carina remained unstable only when the inflow rate was high, the influence of the upper airways caused notable changes in distal flow distributions when the 2 airways models were compared with and without the upper airways. The results suggest that the influence of the upper airways should be included in the respiratory flow assessment as the upper airways extensively affect the flows in distal airways and consequent ventilation distribution in the lungs.

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Section: Methodsmentioning

confidence: 99%

Effect of upper airway on tracheobronchial fluid dynamics

Kim

Collier

Wild

et al. 2018

Numer Methods Biomed Eng

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“…Over the last years, computational models have been used to better understand those interactions. Anatomically based three-dimensional (3D) lung models have elegantly simulated lung tissue mechanics [7–9] and 3D fluid dynamics in large airways [10–12], but without specific focus on the ventilation and gas transport in the entire lung in the context of MBW. More simplified models have addressed these phenomena, but either have not included physiological asymmetries in lung morphology, or have not modeled the whole lung [13–23].…”

Section: Introductionmentioning

confidence: 99%

A multi-scale model of gas transport in the lung to study heterogeneous lung ventilation during the multiple-breath washout test

et al. 2019

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The multiple-breath washout (MBW) is a lung function test that measures the degree of ventilation inhomogeneity (VI). The test is used to identify small airway impairment in patients with lung diseases like cystic fibrosis. However, the physical and physiological factors that influence the test outcomes and differentiate health from disease are not well understood. Computational models have been used to better understand the interaction between anatomical structure and physiological properties of the lung, but none of them has dealt in depth with the tracer gas washout test in a whole. Thus, our aim was to create a lung model that simulates the entire MBW and investigate the role of lung morphology and tissue mechanics on the tracer gas washout procedure. To this end, we developed a multi-scale lung model to simulate the inert gas transport in airways of all size. We then applied systematically different modifications to geometrical and mechanical properties of the lung model (compliance, residual airway volume and flow resistance) which have been associated with VI. The modifications were applied to distinct parts of the model, and their effects on the gas distribution within the lung and on the gas concentration profile were assessed. We found that variability in compliance and residual volume of the airways, as well as the spatial distribution of this variability in the lung had a direct influence on gas distribution among airways and on the MBW pattern (washout duration, characteristic concentration profile during each expiration), while the effects of variable flow resistance were negligible. Based on these findings, it is possible to classify different types of inhomogeneities in the lung and relate them to specific features of the MBW pattern, which builds the basis for a more detailed association of lung function and structure.

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“…The correlation coefficient values we report here ( r ~ 0.6 and above) for the spatial pixel-by-pixel correlation of PC MRI and CFD in v AP and v FH are similar, though slightly lower than those reported for in vitro experiments with hyperpolarized 3 He gas MRI [ 40 ] and water ( 1 H) MRI ( v FH r >0.95 for central airway tree, or r = 0.86 ( r 2 = 0.74) when including upper airways) [ 41 ] in airway casts, and in vivo hyperpolarized 3 He MRI in rats (where for v FH r = 0.82 ( r 2 = 0.68) over the whole of the airways) [ 39 ]. Differences may be attributed to the lower MR signal attainable with 129 Xe compared to 3 He and 1 H, and also the intrinsic advantages of in vitro studies or in vivo studies in mechanically-ventilated animals; (i) the SNR is typically greater (often resulting from increased scan duration and/or signal averaging), (ii) flow rates can be better controlled.…”

Section: Discussionmentioning

confidence: 62%

Human upper-airway respiratory airflow: In vivo comparison of computational fluid dynamics simulations and hyperpolarized 129Xe phase contrast MRI velocimetry

et al. 2021

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Computational fluid dynamics (CFD) simulations of respiratory airflow have the potential to change the clinical assessment of regional airway function in health and disease, in pulmonary medicine and otolaryngology. For example, in diseases where multiple sites of airway obstruction occur, such as obstructive sleep apnea (OSA), CFD simulations can identify which sites of obstruction contribute most to airway resistance and may therefore be candidate sites for airway surgery. The main barrier to clinical uptake of respiratory CFD to date has been the difficulty in validating CFD results against a clinical gold standard. Invasive instrumentation of the upper airway to measure respiratory airflow velocity or pressure can disrupt the airflow and alter the subject’s natural breathing patterns. Therefore, in this study, we instead propose phase contrast (PC) velocimetry magnetic resonance imaging (MRI) of inhaled hyperpolarized 129Xe gas as a non-invasive reference to which airflow velocities calculated via CFD can be compared. To that end, we performed subject-specific CFD simulations in airway models derived from 1H MRI, and using respiratory flowrate measurements acquired synchronously with MRI. Airflow velocity vectors calculated by CFD simulations were then qualitatively and quantitatively compared to velocity maps derived from PC velocimetry MRI of inhaled hyperpolarized 129Xe gas. The results show both techniques produce similar spatial distributions of high velocity regions in the anterior-posterior and foot-head directions, indicating good qualitative agreement. Statistically significant correlations and low Bland-Altman bias between the local velocity values produced by the two techniques indicates quantitative agreement. This preliminary in vivo comparison of respiratory airway CFD and PC MRI of hyperpolarized 129Xe gas demonstrates the feasibility of PC MRI as a technique to validate respiratory CFD and forms the basis for further comprehensive validation studies. This study is therefore a first step in the pathway towards clinical adoption of respiratory CFD.

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3D phase contrast MRI in models of human airways: Validation of computational fluid dynamics simulations of steady inspiratory flow

Abstract: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1400-1409.

Cited by 19 publications

References 38 publications

Effect of upper airway on tracheobronchial fluid dynamics

Effect of upper airway on tracheobronchial fluid dynamics

A multi-scale model of gas transport in the lung to study heterogeneous lung ventilation during the multiple-breath washout test

Human upper-airway respiratory airflow: In vivo comparison of computational fluid dynamics simulations and hyperpolarized 129Xe phase contrast MRI velocimetry

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