Correlation between Emphysema Volume and Small Shadow Density on CT and the Lung Function in Pneumoconiosis

Objective: To compare the influence of emphysema and lung small shadow on the lung function of patients with pneumoconiosis. Methods: We selected 96 patients who were admitted to the Taihe Hospital (Shiyan city) for pneumoconiosis complicated by emphysema between 2015 and 2020. Chest computed tomography (CT) and lung function assessments were performed. The low attenuation volumes (LAV%) of the whole lung; left and right lungs; and upper, middle, and lower lobes of each lung were quantified using 64-slice spiral CT (GE Optima CT680). Based on the LAV% of the whole lung, the patients were divided into groups A (LAV%<15%), B (LAV%: 15%–30%), and C (LAV% >30%). The small shadow density (SSD) of the whole lung; left and right lungs; and upper, middle, and lower lung fields was calculated by applying the criteria for evaluating SSD on chest radiographs to CT images. The correlation between SSD and lung function was also analyzed. Results: The SSD of the whole lung was negatively correlated with the forced expiratory volume in the first second (FEV1), total lung capacity (TLC), peak expiratory flow (PEF), maximum expiratory flow after 75% of the forced vital capacity (FVC) has not been exhaled (MEF75%), and maximum expiratory flow after 25% of the FVC has not been exhaled (MEF25%), and it was positively correlated with residual volume (RV)/TLC. LAV% was negatively correlated with FEV1, ratio of FEV to FEV1 (FEV1%), carbon monoxide diffusion capacity (DLCO), PEF, MEF75%, maximum expiratory flow after 50％ of the FVC has not been exhaled (MEF50%), and MEF25% in the whole lung; left and right lungs; and upper, middle, and lower lung lobes; however, it was positively correlated with RV and RV/TLC%. When LAV% was >30%, the correlation between LAV% and FEV1, FEV1%, DLCO, RV/TLC, PEF, MEF75%, MEF50%, and MEF25% was stronger in group C than in groups A and B. A certain degree of correlation was observed between the SSD in the lungs and the ventilation function and volume parameters; however, the correlation between SSD and the diffusion function was weak. Conclusion: The degree of emphysema and SSD in patients with pneumoconiosis have a certain degree of correlation with the lung function; however, the SSD of emphysema has a relatively better correlation with the lung function. It can be used to evaluate the degree of lung injury in patients with pneumoconiosis to a certain extent and is worthy of clinical application.