The correlation between the paired inspiratory and expiratory three-dimensional quantitative CT and pulmonary function test in chronic obstructive pulmonary disease

Abstract

Objective To investigate the correlation between the paired inspiratory and expiratory quantitative CT and pulmonary function tests (PFTs) in patients with chronic obstructive pulmonary disease (COPD). Methods A total of 84 patients with COPD were enrolled.For each patient,CT scan was performed in deep inspiration and expiration.Using automatic post-processing software,a three-dimension quantitative measurement was employed to assess the CT parameters of emphysema and air trapping.The correlation between CT and PFT was evaluated by the Spearman rank correlation test and multivariate linear regression analysis. Results The percent 1[Perc1,(-984.28±17.93) HU] and percent 15[Perc15,(-948.35±22.26) HU] from the CT parameters of emphysema were positively correlated with the forced expiratory volume in 1 second predicted (FEV 1%,48.69±23,47),the ratio of forced expiratory volume in 1 second over forced vital capacity[FEV1/FVC,(45.89±15.36) %,r=0.45—0.67,P<0.01],was negatively correlated with the ratio of residual volume to total lung capacity[RV/TLC,(61.32±14.48) %].The other CT parameters of emphysema index (EI) and the parameters of air trapping,the change in relative lung volume with attenuation values from-860 to-950 HU[RVC-860—-950,(17.66±22.36) %],the expiration to inspiration ratio of mean lung density (MLDex/in,0.93±0.06),the expiration to inspiration ratio of lung volume (LVex/in,0.71±0.14) had negative correlations with log FEV1%,FEV1/FVC (r=-0.48—-0.69,P<0.01) and positive correlations with RV/TLC (r=0.41—0.66,P<0.01).The further univariate linear regressions showed that EI,Perc1,Perc15,RVC-860—-950,MLDex/in,LVex/inwere correlated with the parameters of PFTs (Rsquare values of the regression equation,ranged from 0.27 to 0.66,P<0.01).After the pairwise combinations of the parameters of emphysema and air trapping,multivariate stepwise regressions showed betterRsquare values from 0.66 to 0.85. Conclusions CT parameters of emphysema and air trapping can reflect pulmonary function in COPD patients.The combinations of the two types of CT parameters are more correlated with the PFTs parameters. Key words: Lung diseases,obstructive; Respiratory function tests; Tomography,X-ray computed