Morphology and Three-Dimensional Inhalation Flow in Human Airways in Healthy and Diseased Subjects

University of Minnesota M.S. thesis.September 2017. Major: Aerospace Engineering and Mechanics. Advisor: Filippo Coletti. 1 computer file (PDF); vi, 53 pages.We 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

Sub Millimeter Analysis of Specificity of SE, GE, and ASE BOLD Responses in the Human Visual Cortex

Sub-millimeter spatial resolution applications are becoming of increasing interest in fMRI. Several animal and human studies have successfully mapped high resolution functional organizations. However, it is not known which fMRI technique (which depends on field strength), maximizes contrast to noise as well as specificity to capillaries for sub-millimeter functional mapping. In this work we examine this problem by comparing functional maps, at 0.5mm in plane resolution, of gradient echo BOLD, spin echo BOLD, and asymmetric echo BOLD in human visual cortex at 7 Tesla

The Diderot meteorite: The second chassignite

The Diderot meteorite is a dunite discovered in Sahara. The martian origin is unambiguous and Diderot shares strong petrographical similarities with Chassigny

γ-H2AX foci as in vivo effect biomarker in children emphasize the importance to minimize x-ray doses in paediatric CT imaging

Objectives: Investigation of DNA damage induced by CT x-rays in paediatric patients versus patient dose in a multicentre setting. Methods: From 51 paediatric patients (median age, 3.8 years) who underwent an abdomen or chest CT examination in one of the five participating radiology departments, blood samples were taken before and shortly after the examination. DNA damage was estimated by scoring gamma-H2AX foci in peripheral blood T lymphocytes. Patient-specific organ and tissue doses were calculated with a validated Monte Carlo program. Individual lifetime attributable risks (LAR) for cancer incidence and mortality were estimated according to the BEIR VII risk models. Results: Despite the low CT doses, a median increase of 0.13 gamma-H2AX foci/cell was observed. Plotting the induced gamma-H2AX foci versus blood dose indicated a low-dose hypersensitivity, supported also by an in vitro dose-response study. Differences in dose levels between radiology centres were reflected in differences in DNA damage. LAR of cancer mortality for the paediatric chest CT and abdomen CT cohort was 0.08 and 0.13% respectively. Conclusion: CT x-rays induce DNA damage in paediatric patients even at low doses and the level of DNA damage is reduced by application of more effective CT dose reduction techniques and paediatric protocols

Le diagnostic précoce des troubles du comportement externalisé est-il fiable ? Mise à l’épreuve d’une procédure multi informateurs et multi méthodes

peer reviewedCette contribution questionne la fiabilité du diagnostic précoce des troubles du comportement externalisé chez l’enfant. Les données concernant le comportement de 118 enfants ont été collectées par questionnaires et observation auprès de leurs parents, leurs enseignants et les cliniciens lors du recrutement et après 12 mois. Les résultats montrent des variations importantes dans le nombre d’enfants atteignant un seuil clinique selon l’informateur et la méthode considérés. Une méthode combinant les évaluations des informateurs pour obtenir un diagnostic valide est éprouvée. Les résultats plaident en faveur d’une procédure multi-informateurs et multiméthodes dont les implications sont discutées sur le plan clinique et de la recherche.H2M childre

Morphological and functional properties of the conducting human airways investigated by in vivo CT and in vitro MRI

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.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