Dynamic Chest Radiography as an Alternative to Pulmonary Function Tests for Chronic Obstructive Pulmonary Disease

Background Pulmonary function tests (PFTs) are the clinical standard for diagnosing chronic obstructive pulmonary disease (COPD) but face limitations in accessibility and complexity. Dynamic chest radiography (DCR) is an emerging technique that enables dynamic pulmonary function assessment with low radiation exposure, suggesting potential as an alternative to PFTs. However, its diagnostic validity remains unproven. Purpose To determine whether DCR is an efficacious alternative approach to PFTs for COPD screening. Materials and Methods This prospective single-center observational study enrolled participants with or without COPD from November 2022 to July 2024. Correlations between DCR parameters and PFT indexes were assessed using Pearson correlation. Receiver operating characteristic analysis was used to evaluate diagnostic performance. The least absolute shrinkage and selection operator (LASSO) and multivariable logistic regression were used to select features and build and train predictive models, which were tested on an internal test set. A nomogram was used to visualize COPD probability, calibrated using the Hosmer-Lemeshow test. Results This study included 553 participants (median age, 60 years [IQR, 53-67 years]; 355 men; 198 women; 191 with COPD, 362 controls). DCR parameters were positively correlated with PFT indexes in participants with COPD: The combined bilateral (right and left lungs) rate of change in projected lung area (ΔPLA) during deep breathing was correlated with forced expiratory volume in 1 second (FEV₁) percent predicted (r = 0.650; P < .001) and the ratio of FEV₁ to forced vital capacity (r = 0.638; P < .001). The diagnostic performance of bilateral ΔPLA during deep breathing was high in the internal test set (area under the receiver operating characteristic curve [AUC], 0.78 [95% CI: 0.72, 0.85]). Three DCR features were selected to construct the DCR model, which performed well in the internal test set (AUC, 0.82 [95% CI: 0.75, 0.89]). The combined model incorporating a DCR parameter and smoking status demonstrated high diagnostic performance (internal test set: AUC, 0.85 [95% CI: 0.78, 0.92]). Conclusion A DCR-based nomogram demonstrated robust diagnostic performance in identifying COPD, suggesting that DCR represents an efficacious alternative approach to standard PFTs for COPD screening. ClinicalTrials.gov Identifier: NCT06653413 © The Author(s) 2025. Published by the Radiological Society of North America under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Hatabu et al in this issue.