Quantitative analysis of volumetric paired thin section multi detector computed tomography scans and pulmonary function tests in patients with severe emphysema

Purpose: To investigate relationship between volumetric three-dimensional CT-data sets obtained in inspiration and expiration and pulmonary function tests. Material and methods: Thirty-seven patients (19-w, 18-m, mean age [±SD] 62 ± 9 years) with severe emphysema due to COPD (GOLD IV) were included in this retrospective study. All scans were performed during inspiration and expiration in every patient on same standard 16-channel-multi-detector-CT (MDCT). MDCT-data were analyzed with MeVisPULMO3D software to give following parameters: lung volume (LV), emphysema index (EI), emphysema volume (EV), and core to peel distribution for whole lung, each whole lung, each lung lobe separately. Four clusters with different emphysema volumes (>2, 8, 65, 120 mm³) were calculated. These results were correlated with body mass index (BMI), forced expiratory volume in 1 second (FEV1), inspiratory vital capacity (VCin), residual volume (RV), total lung capacity (TLC), RV/TLC and 6-minute walk. Results: Inspiratory LV correlated well with TLC (r=0.92, p<0.001), expiratory LV with RV (r=0.93, p<0.001), RV/TLC with inspiratory/expiratory-LV (r=0.68, p<0.001). FEV1 correlated with change of core volume (r=-0.48, p=0.002), VCin with change of peel volume (r=0.46, p=0.003). The mean inspiratory EI of 37 ± 9 decreased by 25 ± 9 % (p<0.001) during expiration resulting in a change of EV by 930ml ± 370ml (p<0.001). On the basis of the lobar distribution of emphysema we divided patients into predominantly upper-lobe (ULD) and lower-lobe disease (LLD). LLD-patients had lower RV (p=0.01) and greater VCin (p=0.002) in comparison with ULD-patients. The change of large emphysema clusters correlated with RV/TLC (r=-0.65, p<0.001) and inspiratory/expiratory-LV ( r=-0.54, p<0.001). Conclusion: The results obtained from analysis of MDCTscans reflect differently functional changes. While inspiratory data sets reflect better anatomic changes, expiratory scans are closer related to the pulmonary function test results. Volumetric core to peel and cluster analysis provide better insights into the regional hyperinflation areas.