Mechanical forces affect the alveolar shape, depend on location and tissue composition and vary during the respiratory cycle. This study performs alveolar morphomics in different lobes of human lungs using models generated from 3D microCT images. Cylindrical tissue samples (1.6x2 cm) were extracted from two non-transplantable donor lungs (one ex-smoker and one smoker, 3 samples per subject) that were air inflated and frozen solid in liquid nitrogen vapor. Samples were scanned with microCT (11 µm/voxel). Within representative cubic regions of interest (5.5 mm edge length), alveoli were segmented to produce corresponding 3D models from which quantitative data were obtained. The surface of segmented alveoli (n=23,587) was divided into individual planar surfaces (facets) and angles between facet normals were calculated. Moreover, the number of neighboring alveoli was estimated for every alveolus. The main results are: Higher mean alveolar volumes and surface sizes in both upper lung lobes compared with the lower lobes. An increasing number of facets from top to bottom, as well as a decreasing number of median alveolar neighbors from the upper lobes to the lower lobes, an increasing ratio of alveolar entrance size to the surface size of the alveoli from top to bottom and larger median angles between facet normals in the upper lobes of both lungs than in the lower lobes. By using this new approach of analyzing alveolar 3D data, which enables the estimation of facet, neighbor and shape characteristics, we aimed to establish the baseline measures for in-depth studies of mechanical conditions and morphology.
