Evolution of CT characteristics of pulmonary lesions
Figure 1 depicts the evolution of CT features of pulmonary lesions in different time intervals from disease onset. Significant differences were found among the time intervals in the proportion of pulmonary lesions that are (1) pure GGO (χ2 = 37.97, p = 0.01), (2) mixed attenuation (GGO and consolidation) (χ2 = 12.80, p < 0.01), (3) mixed attenuation with reticular/linear opacities (χ2 = 20.57, p < 0.01), and (4) consolidation with reticular/linear opacities (χ2 = 32.49, p < 0.01) and pure consolidation (χ2 = 10.37, p = 0.03). A significant linear decrease in the proportions of pure GGO lesions (y = 0.55–0.08x, p < 0.01) and mixed attenuation lesions (y = 0.31–0.03x, p = 0.01) and a significant linear increase in the proportions of lesion with reticular/linear opacities (mixed attenuation + linear opacities (y = 0.08 + 0.04x, p < 0.01) and consolidation + linear opacities (y = − 0.03 + 0.04x, p < 0.01)) were observed over time.
Fig. 1 Evolution of CT characteristics of pulmonary lesions in patients with COVID-19. The time intervals after disease onset (days) were divided into 5 groups, i.e., days 0–3 (lesion number = 114), days 4–7 (lesion number = 241), days 8–10 (lesion number = 189), days 11–14 (lesion number = 178), and days 15–21 (lesion number = 95). GGO, ground glass opacities; mixed attenuation = ground glass opacities + consolidation