Morphological and functional properties of the conducting human airways investigated by in vivo CT and in vitro MRI
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Morphological and functional properties of the conducting human airways investigated by in vivo CT and in vitro MRI
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2017-10-26
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The accurate representation of the human airway anatomy is crucial for understanding and modeling the structure-function relationship in both healthy and diseased lungs. The present knowledge in this area is based on morphometric studies of excised lung casts, partially complemented by in vivo studies in which computed tomography (CT) was used on a small number of subjects. In the present study, we analyze CT scans of a cohort of healthy subjects and obtain comprehensive morphometric information down to the seventh generation of bronchial branching, including airway diameter, length, branching angle, and rotation angle. While some of the geometrical parameters (such as the child-to-parent branch diameter ratio) are found to be in line with accepted values, for others (such as the branch length-to-diameter ratio) our findings challenge the common assumptions. We also evaluate several metrics of self-similarity, including the fractal dimension of the airway tree. Additionally, we use phase-contrast magnetic resonance imaging (MRI) to obtain the volumetric flow field in the 3D printed airway model of one of the subjects during steady inhalation. This is used to relate structural and functional parameters and, in particular, to close the power-law relationship between branch flow rate and diameter. The diameter exponent is found to be significantly lower than in the usually assumed Poiseuille regime, which we attribute to the strong secondary (i.e. transverse) velocity component. The strength of the secondary velocity with respect to the axial component exceeds the levels found in idealized airway models, and persists within the first seven generations.
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Funding for this work was provided by the National Science Foundation (CBET-1453538) and the National Institutes of Health (NHLBI-R21HL129906). COPDGene was supported by Award Number R01 HL089897 and Award Number R01 HL089856 from the National Heart, Lung, and Blood Institute and by the COPD Foundation through contributions made to an Industry Advisory Board comprised of AstraZeneca, Boehringer Ingelheim, GlaxoSmithKline, Novartis, Pfizer, Siemens and Sunovion.
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Van de Moortele T., Wendt C., Coletti F. (2017). Morphological and functional properties of the conducting airways in healthy subjects investigated by in vivo CT and in vitro MRI. Journal of Applied Physiology (submitted).
Suggested citation
Van de Moortele, Tristan; Wendt, Christine H.; Coletti, Filippo. (2017). Morphological and functional properties of the conducting human airways investigated by in vivo CT and in vitro MRI. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/190800.
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