Study of the Variability in Upper and Lower Airway Morphology in Sprague–Dawley Rats Using Modern Micro‐CT Scan‐Based Segmentation Techniques

Abstract

Animal models are being used extensively in pre-clinical and safety assessment studies to assess the effectiveness and safety of new chemical entities and delivery systems. Although never entirely replacing the need for animal testing, the use of computer simulations could eventually reduce the amount of animals needed for research purposes and refine the data acquired from the animal studies. Computational fluid dynamics is a powerful tool that makes it possible to simulate flow and particle behavior in animal or patient-specific respiratory models, for purposes of inhaled delivery. This tool requires an accurate representation of the respiratory system, respiration and dose delivery attributes. The aim of this study is to develop a representative airway model of the Sprague-Dawley rat using static and dynamic micro-CT scans. The entire respiratory tract was modeled, from the snout and nares down to the central airways at the point where no distinction could be made between intraluminal air and the surrounding tissue. For the selection of the representative model, variables such as upper airway movement, segmentation length, airway volume and size are taken into account. Dynamic scans of the nostril region were used to illustrate the characteristic morphology of this region in anaesthetized animals. It could be concluded from this study that it was possible to construct a highly detailed representative model of a Sprague-Dawley rat based on imaging modalities such as micro-CT scans.

Comparison of hyperpolarized 3He MRI with Xe‐enhanced computed tomography imaging for ventilation mapping of rat lung

“…The error bars in Fig. 2 indicate the representative standard deviation of repeated scans and the full lines are the best fits to the data points based on Equations [2] and [4], respectively. The differences in signal dependence versus breath number for the two methods should be noted.…”

“…It should be noted in Equation [2] that the effect of subsequent RF pulses on residual gas (q) is described by the summation factor P sin a kþ1 ð Þq k . The flip angle a kþ1 is defined according to the expression:…”

“…The remaining pixels were used to create a mask which was then applied to all images in the series. The ventilation parameter r was estimated on a pixel-by-pixel basis by fitting with Equations [2] and [4] for MR and CT data, respectively, using Matlab R2007b (The MathWorks, Natick, MA, USA) to yield parametric ventilation r maps.…”

“…In particular, to observe regional changes, longitudinally and noninvasively, microimaging may play an important role in the development of airway models (2), in the detection of disease earlier and in assisting with the development of new therapeutic approaches (3). Both MR and CT have demonstrated anatomical changes associated with alveolar destruction (i.e.…”

Bronchial tree Architecture in Mammals of Diverse Body Mass

“…As there is no specific rule to nominate some lung structures of rat and pig, authors utilized terms in their publications (Nakakuki, 1983(Nakakuki, , 1994. Human bronchia anatomy is well known (Williams, 1995) as the lung anatomy of the pig (Nakakuki, 1975;Hare, 1986;Dyce et al, 1997;Dondelinger et al, 1998;Mouton et al, 1999;Maina & Gils, 2001) and rat (De Backer et al, 2009;Nakakuki, 1983;Yeh et al, 1979). Weibel & Gomez (1962) cited that each bronchus divide in two distal bronchia corresponding to a pattern nominated dichotomic which is frequently observed in nature.…”