A three-dimensional model of the human airway tree: application for airway-parenchymal interaction

A three-dimensional (3D) model of the human airway tree is proposed based on a deterministic algorithm that can generate a branching duct system in an organ. The algorithm based on two principles: (1) the amount of fluid delivery through a branch is proportional to the volume of the region supplied by the branch; and (2) the terminal branches are arranged homogeneously within the organ. These principles define the basic process of branching: the generation of the dimensions and directionality of the two daughter branches is governed by the properties of the parent branch and the region the parent supplies. The algorithm is composed of nine basic rules and four complementary rules. When the contour of an organ and the position of the trunk are specified, branches are successively generated by the algorithm. Applied to the human lung, the algorithm generates a 3D airway tree which consists of about 54,000 branches. The tree is a fractal structure and its morphometric characteristics of the model are in good agreement with those reported in the literature. The algorithm and the 3D airway model are useful for studying structure function relationship in the lung such as airway-parenchymal interaction and simulated CT imaging.