Browsing by Author "Van de Moortele, Tristan"
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Item Magnetic resonance velocimetry of the human airways(2015-04-22) Van de Moortele, TristanItem Morphological and functional properties of the conducting human airways investigated by in vivo CT and in vitro MRI(2017-10-26) Van de Moortele, Tristan; Wendt, Christine H.; Coletti, FilippoThe 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.Item Morphological properties of the conducting human airways by in vivo CT(2017-10-26) Van de Moortele, Tristan; Coletti, Filippo; Wendt, Christine; fcoletti@umn.edu; Coletti, FilippoBranch by branch morphometric data of human airways as presented in the article "Morphological and functional properties of the conducting human airways investigated by in vivo CT and in vitro MRI." We investigate the airway tree structure obtained by CT from a cohort of subjects with normal lung function, from 36 healthy non-smoking subjects from the COPDGene study (Regan et al. 2010).Item Morphology and Three-Dimensional Inhalation Flow in Human Airways in Healthy and Diseased Subjects(2017-09) Van de Moortele, TristanWe investigate experimentally the relation between anatomical structure and respiratory function in healthy and diseased airways. Computed Tomography (CT) scans of human lungs are analyzed from the data base of a large multi-institution clinical study on Chronic Obstructive Pulmonary Disease (COPD). Through segmentation, the 3D volumes of the airways are determined at total lung capacity. A geometric analysis provides data on the morphometry of the airways, including the length and diameter of branches, the child-to-parent diameter ratio, and branching angles. While several geometric parameters are confirmed to match past studies for healthy subjects, previously unreported trends are reported on the length of branches. Specifically, in most dichotomous airway bifurcation, the branch of smaller diameter tends to be significantly longer than the one of larger diameter. Additionally, the branch diameter tends to be smaller in diseased airways than in healthy airways up to the 7th generation of bronchial branching. 3D fractal analysis is also performed on the airway volume. Fractal dimensions of 1.89 and 1.83 are found for healthy non-smokers and declining COPD subjects, respectively, furthering the belief that COPD (and lung disease in general) significantly affects the morphometry of the airways already in early stages of the disease. To investigate the inspiratory flow, 3D flow models of the airways are generated using Computer Aided Design (CAD) software and 3D printed. Using Magnetic Resonance Velocimetry (MRV), 3-component 3D flow fields are acquired for steady inhalation at Reynolds number Re ~ 2000 defined at the trachea. Analysis of the flow data reveals that diseased subjects may experience greater secondary flow strength in their conducting airways, especially in deeper generations.