Chest CT findings of COVID-19 pneumonia by duration of symptoms

Abstract

Purpose: To evaluate lung abnormalities on thin-section computed tomographic (CT) scans in patients with COVID-19 and correlate findings to duration of symptoms.

Methods: In total, 348 CT scans in 112 patients were classified according to the time after the onset of the initial symptoms, namely stage-1 (0-4 days); stage-2 (5-9 days); stage-3 (10-14 days); stage-4 (15-21 days); stage-5 (22-28 days); and stage-6 (＞28 days). Each lung lobe was evaluated for extent affected by ground-glass opacities (GGO), crazy-paving pattern and consolidation, in five categories of percentual severity. Summation of scores from all five lung lobes provided the total CT score (maximal CT score, 25).

Results: The predominant patterns of lung abnormalities were GGOs, crazy-paving pattern, consolidation and linear opacities. The frequency of crazy-paving pattern, consolidation and linear opacities peaked at stage-3 (62.7 %), stage-4 (75.0 %) and stage-5 (83.1 %), respectively, and decreased thereafter. Total CT scores increased from stage-1 to stage-2 (2.8 ± 3.1, vs. 6.5 ± 4.6, respectively, P < 0.01), and thereafter remained high. The lower lobes were more inclined to be involved with higher CT scores except for stage-1. At stage-6 98.1 % of CT scans still showed abnormalities (CT score 7.5 ± 4.1).

Conclusion: Thin-section CT could provide semi-quantitative analysis of pulmonary damage severity. This disease changed rapidly at the early stage, then tended to be stable and lasted for a long time.

Keywords: COVID-19; Computed tomographic; Crazy-paving pattern; Ground-glass opacities.

Fig. 1

Male, 48 years, transverse thin-section CT scan. (a) 4 days after the onset of initial symptoms (stage-1): subpleural GGO (arrow) in the right lower lobe. (b) 8 days after the onset of initial symptoms (stage-2): more severe lesions with GGO and crazy-paving pattern (arrow) in the right lower lobe. (c) 12 days after the onset of initial symptoms (stage-3): again increased severity of GGO and crazy-paving pattern (white arrow) in the right lower lobe, and GGO (black arrow) also appeared in the left lower lobe. (d) 18 days after the onset of initial symptoms (stage-4): The predominant pattern of abnormality was consolidation (thick white arrow), accompanied by a small GGO (thin black arrow) in both lower lobes. (e) 26 days after the onset of initial symptoms (stage-5): the extent of the lesions was reduced with consolidation (thick white arrow) and linear opacities (thin black arrow) in the right lower lobe, and crazy-paving pattern (thick white arrow) and linear opacities (thin black arrow) in the left lower lobe. (f) 38 days after the onset of initial symptoms (stage-6): There was no significant change in the extent and composition of lesions compared with the directly prior CT result, with consolidation (thick white arrow) and linear opacities (thin black arrow) in the right lower lobe, and crazy-paving pattern (thick white arrow) and linear opacities (thin black arrow) in the left lower lobe.

Fig. 2

Female, 41 years, transverse thin-section CT scan. (a) 0 day after the onset of initial symptoms (stage-1): pure GGO in the right upper lobe near the hilum (arrow). (b) 7 days after the onset of initial symptoms (stage-2): increased severity of the lesions with GGO (thin arrow), crazy-paving pattern (thin arrow) and consolidation (thick arrow). (c) 14 days after the onset of initial symptoms (stage-3): reduced extent of GGO (thin white arrow) and consolidation (thick white arrow), and linear opacities appeared (thin black arrow). (d) 25 days after the onset of initial symptoms (stage-5): only a small residual pure GGO (arrow).

Fig. 3

The frequency of GGO, crazy-paving pattern, consolidation and linear opacities at six stages.

Fig. 4

(a) The total CT scores of all stages based the period between the onset of initial symptoms and the CT scans. (b) The number of involved lobes of all stages based the period between the onset of initial symptoms and the CT scans.