Normal human airway dimensions and branching geometry assessed via QCT for 5 standardized paths

Background: We seek to establish baseline computed tomography (CT)-based airway measures for 5 standardized paths into the lung that include segmental bronchi RB1, RB4, RB10, LB1, LB10, incl. differences between normal male (M) and female (F). Methods : 56 normal subjects (34 female, 22 male) of 100 imaged using a standardized CT protocol: std kernel, 0.5mm slice thick., 100mAs, 120kV, breath-hold at 90% vital cap. have been analyzed to date. Subjs age range: 20 - 70. Data analysis included airway segmentation, labeling (incl. sub-segmental), and measurements (Apollo® 2.0, VIDA Diagn.). All steps were automated but visually verified by human experts and edited as needed to assure data quality. Results : Common lumen diameter (D) and wall thickness (WT) were observed across the population, with segment specific differences. M and F subjects differ significantly in most but not all segments, with D in M being bigger where significant. E.g., 1.12 mm D diff. in RB1, 0.45 mm in LB1, but no significant diff. in RB4. WT are generally greater in M than in F. Unique branching patterns (lumen dimension & branching angles) common across the population were observed for sub-segmental branches in LB/RB 3, RB9, LB/RB10 (monopodal rather than bipodal, with the latter being dominant in the rest of the human airway tree). Path-based Pi10 measurements to date have not differed significantly, between individual sub-trees or between F and M. Conclusions: A common monopodial branching pattern has been identified for 3 branches. Normative measures for a standardized set of paths into the normal human lung have been established and provide a basis for evaluating changes associated with pathologic processes.