Airway Morphology From High Resolution Computed Tomography in Healthy Subjects and Patients With Moderate Persistent Asthma

Abstract

Models of the human respiratory tract developed in the past were based on measurements made on human tracheobronchial airways of healthy subjects. With the exception of a few morphometric characteristics such as the bronchial wall thickness (WT), very little has been published concerning the effects of disease on the tree structure and geometrical features. In this study, a commercial software package was used to segment the airway tree of seven healthy and six moderately persistent asthmatic patients from high resolution computed tomography images. The process was assessed with regards to the treatment of the images of the asthmatic group. The in vivo results for the bronchial length, diameter, WT, branching, and rotation angles are reported and compared per generation for different lobes. Furthermore, some popular mathematical relationships between these morphometric characteristics were examined in order to verify their validity for both groups. Our results suggest that, even though some relationships agree very well with previously published data, the compartmentalization of airways into lobes and the presence of disease may significantly affect the tree geometry, while the tree structure and airway connectivity is only slightly affected by the disease. Anat Rec, 296:852–866, 2013. © 2013 Wiley Periodicals, Inc.

The Creation and Statistical Evaluation of a Deterministic Model of the Human Bronchial Tree from HRCT Images

“…The HR for the major and minor daughters was measured to be HR maj = 0.914±0.087 and HR min = 0.663±0.184. The former is only marginally lower to the one predicted by Tawhai et al [31] while HR min is almost identical to the results of both [31] and [34]. Finally, in their implementation of the model, [32] calculated min and max HR of 0.81 and 0.85, with zero std.…”

“…Montaudon et al [53] found this value to vary between 0.65 and 0.97 while [34] measured HR = 0.72 for the first 6 generations. The HR for the major and minor daughters was measured to be HR maj = 0.914±0.087 and HR min = 0.663±0.184.…”

“…The lung and lobar volumes were also segmented to provide our algorithm with the necessary confining spaces. The manual and semi-automatic use of the PW2 software package as a research tool is explained in [34]. The airway tree model itself was developed using MATLAB v8.4 (R2014b) (The Mathworks Inc, Natick, MA).…”

“…The parent-child diameter ratio, known as the Homothety Ratio (HR), was reported in the literature [22,23,31] as where D is the diameter. Furthermore, a relationship connecting the length and diameter of an airway was investigated in the literature [34,39] and was summarized by Sauret et al [40] as the rule of thumb, …”

“…Because of the irregular shape of the confining space and its subdivisions, the centers of volume can be positioned so that the resulting branch angle is highly variable, with θ ranging between 5°-80° [34]. However, θ is usually below 60° [41] and an optimal value has been calculated at 37.28° based on fundamental physical principles [41–44].…”