A new quantitative index of lobar air trapping in chronic obstructive pulmonary disease (COPD): Comparison with conventional methods

Abstract Purpose To determine the usefulness of newly-proposed index (attenuation–volume index, AVI: increase in mean value of lung attenuation (MVLA) divided by volume decrease ratio (VDR)) for quantitative assessment of lobar air trapping (LAT) using expiratory/inspiratory (E/I) computed tomography (CT) by minimizing influence of respiratory level. Materials and methods Institutional review board approved study protocol. Twenty-one moderate or severe COPD (group A), 16 mild COPD (group B) and 26 normal volunteers (group C) underwent both E/I scans via 320-row CT and pulmonary functional test (PFT). Volume image data were automatically segmented into six lung lobes with minimal manual intervention. AVI, pixel index (PI), air trapping ratio (ATR) and relative volume change (RVC 860–950 ) were calculated in total lung (TL) and each lobe. Four indices in TL were correlated with both PFT result and VDR and those in TL and each lobe were compared between three groups. Results Similar to ATR, AVI correlated with both FEV 1 /FVC ( r  = 0.772, p r  = −0.726, p 860–950 was significantly larger than that of AVI. Conclusion AVI can be a more suitable CT index for quantitative evaluation of LAT, minimizing influence of respiratory level.