Relationship Between the Branching Pattern of Airways and the Spatial Arrangement of Pulmonary Acini — A Re-Examination from a Fractal Point of View

Abstract

The upper lobe of the left lung, surgically removed from an adult for a small carcinoma, was subjected to serial slicing and computer assisted 3-D reconstruction of airways and acini. A fractal dimension of the airways of about 1.74 was obtained applying a 3-D box-counting to the graphics data. At the same time, volumetry was performed of the acinus, the structural and functional unit of the lung, using the same software. The volumes obtained from a total of 130 acini proved to be comparatively uniform, showing a normal type distribution with a mean of 173 ± 38 mm ³. The volume of acini had no correlation with their location in the lung or with the generation number of the terminal bronchioles supplying them, and this was considered to be reflecting a homogeneous 3-D arrangement of acini in the organ. Furthermore, a simple 3-D model of lung was introduced to analyze the relationship between the branching pattern of airways and the volume of acini supplied by them. It was shown that the self-similarity of the spatial distribution of airways is consistent with a volumetrically homogenized space division of the lung.