Morphological Characterization of Acinar Cluster in Mouse Lung Using a Multiscale-based Segmentation Algorithm on Synchrotron Micro-CT Images

Understanding the three-dimensional morphology of pulmonary acini is essential when exploring the biomechanics of respiratory function. In this study, we characterized the morphology of individual acini and a cluster of acini stemming from the same terminal conducting airway using a quantitative approach based on the semi-automatic segmentation of synchrotron micro-CT images of mouse lung. The volume and surface area of five clusters of mouse acini including 50 individual acini were estimated based on the voxel and surface mesh of segmented acini at FRC. The pathway length and width were estimated for one cluster including 15 acini based on the skeleton of segmented acini. The acinar volume was 0.09 ± 0.07 mm³ (mean ± SD), and the surface area was 6.82 ± 4.49 mm², in agreement with previous studies. The volume of the acinar clusters was 0.89 ± 0.34 mm³, and the surface area was 68.18 ± 17.66 mm². The largest volume acinus per cluster was found in the distal region of the terminal conducting airway, and apparent respiratory bronchioles were observed only in large-volume acini. The generation number of pathways per acinus was 8 ± 2 (range: 6–12). The pathway length at lower generations (generations 2–6) increased with the generation number in a single cluster, while did not significantly change at lower generations in some acinar groups. The pathway width increased with increasing generation numbers. Our approach characterized the quantitative morphology of pulmonary acinar clusters in mouse lung, and the results can be used in further biomechanical simulation studies. Anat Rec, 299:1424–1434, 2016.