Hiroko Kitaoka and Ryuji Takaki
Department of Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
(Received January 25, 1999; Accepted June 21, 1999)
Keywords: Fractal, Lung Development, Airway, Branching, Self-Similarity
Abstract. In order to characterize quantitatively the development of the fetal lung, we applied the method of fractal geometry to 3D images of human fetal airways reconstructed from serial histologic sections. Four human fetal right lungs were subjected, whose cranio-rump lengths were 103 mm, 132 mm, 145 mm, and 190 mm, respectively. The former and the latter two corresponded to the pseudogladular stages and the canalicular stages, respectively. Fractal analysis with 3D box-counting method was made for four cubes with side 0.432 mm. The means of fractal dimensions of the former two were 1.7, that of the third was 2.1, and the last was non-fractal. These results show that a self-similar branching growth remains in the pseudoglandular stage and a surface-increasing growth occurs in the canalicular stage. This transition of growth modes may correspond to the functional difference between the airway completed in the pseudoglandular stage and the air space developing in the canalicular stage.