Inter-disease variability in Dynamic Chest Radiography measurements and Pulmonary Function Tests in patients with Asthma, COPD and ILD

Introduction: Dynamic Chest Radiography (DCR) uses sequential radiographs during the respiratory cycle to generate moving images of the thorax. Automated border-detection algorithms can track moving structures. Change in projected lung area (ΔPLA) – the change in visible lung area between maximal inspiration and expiration– may be related to pulmonary function testing (PFT). Objectives: To assess whether ∆PLA differs between patients with interstitial lung disease (ILD), chronic obstructive pulmonary disease (COPD), and asthma. Methods: Three patients with a classical history, examination, and radiology of ILD, COPD or asthma underwent PFTs and DCR. Posteroanterior (PA) and lateral (L) DCR sequences were taken during tidal and deep breathing. Analysis performed using proprietary software calculated ∆PLA at maximal inspiration and end-expiration. Results: PFT results were in keeping with the patients’ disease processes. DCR-derived ∆PLA increased across the three disease groups, with the smallest in ILD (consistent with fibrosis), reduced ∆PLA in COPD (consistent with air trapping), and the largest ∆PLA in asthma. DCR measured ∆PLA provides additional information that supports PFT findings. _{*Post-bronchodilator} Conclusion: DCR-derived ∆PLA reflect important underlying disease processes, which are not easily obtainable from standard spirometry. Further work is needed to assess inter-disease variability of DCR-derived measurements and correlate with PFT.