Segmental Bronchial Diameter Measurement at Inspiration-Expiration Phase by Low-dose MSCT in Healthy Volunteers

Objective: This study aimed to evaluate the normal range of quantitative CT in measuring the airway diameter at inspiration-expiration phase using 3D imaging in healthy adults. Materials and Methods: 68 healthy volunteers, including 42 males and 26 females, with the mean age of 49.3 (SD14.7) years, had undergone low-dose CT scan at full inspiration and the end of expiration. All CT scans were performed within the range from the lung apices to the diaphragm, at a tube potential of 120kVp and an effective mAs of 60. Afterwards, all CT images were analyzed using the 3D software (FUJIFILM Corporation SYNAPSE), and the airway tree was generated according to the automated region-growing technique, which was perpendicular to the cross section measurement of the segmental bronchus in bilateral lower lobes. Meanwhile, the imaging of segmental bronchus was classified as at inspiration and expiration phase in male group, and at inspiration and expiration phase in female group. Moreover, the Din-L and Din-S of the segmental bronchus were analyzed quantitatively. Difference in the segmental bronchial diameter between the inspiration and expiration phase group with the same sex was evaluated with paired-t test, while that between the male and female groups was analyzed by a 2-tailed unpaired t test. In addition, the impact of age, height, weight and BMI on Din-L and Din-S was assessed through multiple linear regression analysis. Results: 378 segmental branches in the lower lobe of lung from male group and 234 from female group were shown using the low-dose multi-slice spiral CT (MSCT) scan. All segmental bronchi were detected automatically using the 3D software. Our results suggested that, Din-L and Din-S in segmental bronchus of both male and female groups at inspiration phase were larger than those at expiration phase; and those in male group were greater than those in female group at both inspiration and expiration phases (P < 0.01). Meanwhile, the average of Din-L and Din-S was markedly related to age at both inspiration and expiration phases. Conclusions: The normal reference values and the likely ranges are determined for segmental bronchus diameter in the lower lobe of adult lung at inspiration-expiration phase. The average of Din-L and Din-S is evidently correlated with age and sex at both inspiration and expiration phases. The segmental bronchus diameter at inspiration phase in adolescents is larger than that at expiration phase.