Lobe Distribution Of Emphysema And The Correlation Analysis Of Pulmonary Function In Emphysema Patients Using Multi-spiral CT

Objectives:To determine the capability of quantitative low attenuation areas volume percentage (LAA%) of every lung lobe to assess pulmonary function loss and disease severity in pulmonary COPD patients and to assess the degrade of emphysema in each lobe. To investigate the correlation coefficients between LAA%of the lobes and the PFT results.Methods:Sixty patients with COPD (COPD group) and thirty healthy people (control group) underwent pulmonary function test (PFT), and to formulate the standards of enrollment and elimination. The diagnosis and classification of COPD refers to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guideline (2011). Chest64-MSCT routine scanning at full inspiration was performed. Those CT raw data were reconstructed to0.625mm section thicknesses using a standard lung kernel, and then were sent to workstation adw4.5rt. For the quantitative assessment, percentage of low attenuation areas of whole lung and every lung lobes:whole lung LAA%, right lung LAA%, right upper lobe LAA%, right middle lobe LAA%, right lower lobe LAA%, left lung LAA%,left supper lobe LAA%, left lower lobe LAA%were automatically calculated by the post processing software (Thoracic VCAR). To study the correlation between these CT parameters and FEV1%predicted, FEV1/FVC, DLCO%predicted, RV/TLC. SPSS software v19.0(SPSS Inc, Chicago, Illinois, USA) was used for all calculations and statistical evaluations. The differences of CT measurements between the two groups were tested by analysis of covariance (ANCOVA), with age, BMI and sex as covariates and correction factors for PFT. Pearson correlation analysis was performed to evaluate the relationship between lung function parameters and the CT measurements, differences in the means of emphysema between lobes. All P-values are two-sided and p<0.05was considered significant.Results:General information:From June2012to June2013, a total of60consecutive patients (mean age67years old; age range42-88years old) with COPD and30normal cases were enrolled in this study, who all were male and current smokers. In COPD group,12cases are GOLD1,20cases are GOLD2,16cases are GOLD3, and12cases are GOLD4.Correlations of LAA%with PFT Results:FEV1%predicted and FEV1/FVC had significant correlation with these parameters. DLCO%predicted、RV/TLC had significant correlation with these parameters, aside from middle and inferior lobe of right lung LAA%. Superior lobe of left lung LAA%have the highest correlation with FEV1、DLCO RV/TLC. However, FEV1/FVC have the highest correlation with inferior lobe of right lung LAA%(r=-0.35, p<0.05)Comparison among COPD groups and non-COPD group:The LAA%of right upper lobe (p<0.05), Right lung (p<0.05) and total lung (p<0.05) were significantly different between the non-COPD group and GOLD1. Differences were significant between non-COPD group and GOLD2, GOLD3and GOLD4.Differences were significant except for LAA%of RUL between GOLD1and GOLD4. And differences were significant except for LAA%of RML between GOLD2and GOLD4. There was no significant difference between GOLD1and GOLD2, GOLD2and GOLD3, GOLD3and GOLD4.Conclusions:Diffusing capacity (r=-0.56,p<0.01) was closely correlated with the extent of emphysema in both upper lobes. Airflow limitation (r=-0.38,p<0.01;r=-0.35,p<0.01) were closely correlated with the extent of emphysema in both lower lobes, whereas the LAA%of both lower lobes showed no correlations with DLCO%predicted and RV/TLC. The low attenuation areas volume percentage of whole lung and each lobe were reflected the lung function impairment in COPD patients.