Irregularity of airway branching in a mouse bronchial tree: A 3-D morphometric study

Limited information on the degree of irregularity of branching patterns of a bronchial tree may obscure the cause of heterogeneous distribution of the lesions in a variety of lung diseases. We reconstructed three dimensional (3-D) images from hilum to terminal bronchioles of a mouse lung, and define d the irregularity of airway branching by diameter-based morphometric analy sis. The relative diameter ratios of a daughter to the parent branch (D1/D0 ) and those of a minor to major daughter branches (D1/D2) were calculated, and irregular dichotomies were found to be distributed in 48% of bifurcatio ns. D1/D0 is well correlated with D1/D2, and is proved to indicate regular and irregular branching, as well as D1/D2. Irregular branches with D1/D0 sm aller than 0.4 correspond to typical lateral branches, taking off from majo r bronchi. Our novel 3-D morphometric analysis showed the first portrayal o f the 3-D structures of mouse bronchial airways, which provides a quantitat ive description of branching patterns leading to the correlation with distr ibution of lesions in the diseased lung.