Quantitative assessment of airway dimensions in young children with cystic fibrosis lung disease using chest computed tomography

Objective: To evaluate lung disease progression using airway and artery (AA) dimensions on chest CT over 2-year interval in young CF patients longitudinally and compare to disease controls cross-sectionally. Methods: Retrospective analysis of pressure controlled end-inspiratory CTs, 12 routine baseline (CT₁) and follow up (CT₂) from AREST CF cohort; 12 disease controls with normal CT. All visible AA-pairs were measured perpendicular to the airway axis. Inner and outer airway diameters and wall (outer-inner radius) thickness were divided by adjacent arteries to compute A_inA-, A_outA-, and A_WTA-ratios, respectively. Differences between CF and control data were assessed using mixed effects models predicting AA-ratios per segmental generation (SG). Power calculations were performed with 80% power and ɑ = 0.05. Results: CF, median age CT₁ 2 years; CT₂ 3.9 years, 5 males. Controls, median age 2.9 years, 10 males. Total of 4798 AA-pairs measured. Cross-sectionally: A_inA-ratio showed no difference between controls and CF CT₁ or CT₂. A_outA-ratio was significantly higher in CF CT₁ (SG 2-4) and CT₂ (SG 2-5) compared to controls. A_WTA-ratio was increased for CF CT₁ (SG 1-5) and CT₂ (SG 2-6) compared to controls. CF longitudinally: A_inA-ratio was significantly higher at CT₂ compared to CT₁. Increase in A_outA-ratio at CT₂ compared to CT₁ was visible in SG ≥4. Sample sizes of 21 and 58 would be necessary for 50% and 30% A_outA-ratio reductions, respectively, between CF CT₂ and controls. Conclusion: AA-ratio differences were present in young CF patients relative to disease controls. A_outA-ratio as an objective parameter for bronchiectasis could reduce sample sizes for clinical trials.