CT findings of COVID-19 in follow-up: comparison between progression and recovery

Abstract

Purpose: We aimed to retrospectively analyze the imaging changes detected in the follow-up of coronavirus disease 2019 (COVID-19) patients on thin-section computed tomography (CT).

Methods: We included 54 patients diagnosed with COVID-19. The mean interval between the initial and follow-up CT scans was 7.82±3.74 days. Patients were divided into progression and recovery groups according to their outcomes. We evaluated CT images in terms of distribution of lesions and imaging manifestations. The manifestations included ground-glass opacity (GGO), crazy-paving pattern, consolidation, irregular line, and air bronchogram sign.

Results: COVID-19 lesions showed mainly subpleural distribution, which was accompanied by bronchovascular bundle distribution in nearly 30% of the patients. The lower lobes of both lungs were the most commonly involved. In the follow-up, the progression group showed more involvement of the upper lobe of the left lung than the recovery group. GGO was the most common sign. As the disease progressed, round GGO decreased and patchy GGO increased. On follow-up CT, consolidation increased in the progression group while decreasing in the recovery group. Air bronchogram sign was more commonly observed at the initial examination (90.9%) than at follow-up (30%) in the recovery group, but there was no significant change in the progression group. Pleural effusion and lymphadenopathy were absent in the initial examination, but pleural effusion was observed in three cases after follow-up.

Conclusion: As COVID-19 progressed, round GGOs tended to evolve into patchy GGOs, consolidation increased, and pleural effusion could be occasionally observed. As COVID-19 resolved, the crazy-paving pattern and air bronchogram significantly decreased.

Figure 1. a, b

A 75-year-old man with COVID-19, in the progression group. Axial CT image (a) from the initial scan shows the round ground-glass opacities (GGOs) distributed around the subpleural area in the bilateral lower lobes. Axial image (b) from the follow-up CT obtained 8 days later shows crazy-paving pattern appear within the GGOs bilaterally in the lower lobes.

Figure 2. a, b

A 49-year-old man with COVID-19, in the progression group. Axial CT image (a) from the initial scan shows the round and patchy GGOs distributed around the subpleural area of right middle lobe and bilateral lower lobes. Crazy-paving patterns are present within GGOs. Axial image (b) from the follow-up CT obtained 13 days later shows the patchy GGOs distributed around the subpleural area of the right middle lobe, left upper lobe, and bilateral lower lobes. The GGOs, crazy-paving patterns, consolidation, and irregular lines are significantly increased.

Figure 3. a, b

A 35-year-old man with COVID-19, in the progression group. Axial CT image (a) from the initial scan shows patchy GGOs and consolidations both around the subpleural area and around bronchovascular bundle in the bilateral upper lobes and the left lower lobe. Axial image (b) from the follow-up CT obtained 4 days later shows increase in the GGOs and consolidations; also, air bronchograms appear.

Figure 4. a, b

A 74-year-old man with COVID-19, in the progression group. Axial CT image (a) from the initial scan shows that the patchy GGOs are present around subpleural area and bronchovascular bundle in the right middle and bilateral lower lobes. Air bronchogram is observed within GGOs in the middle lobe. Axial image (b) from the follow-up CT obtained 7 days later shows patchy GGOs and apparently increased air bronchograms. Pleural effusion appears on the left (arrow).

Figure 5. a, b

A 35-year-old man with COVID-19, in the recovery group. Axial CT image (a) from the initial scan shows patchy consolidation and air bronchogram in the right upper lobe. There are GGOs located around the consolidation. Axial image (b) from the follow-up CT obtained 10 days later shows that the consolidation is completely absorbed, air bronchogram is absent, and only a few GGOs remain.

Figure 6. a, b

A 72-year-old woman with COVID-19, in the recovery group. Axial CT image (a) from the initial scan shows patchy GGOs located around the subpleural area in the right middle lobe, left upper lobe and bilateral lower lobes. Air bronchograms appear within the GGOs. Axial image (b) from the follow-up CT obtained 15 days later shows GGOs obviously reduce, the air bronchograms are absent, and only a few irregular lines are present.

Figure 7. a–c

A 36-year-old woman with COVID-19, in the progression group. Axial CT image (a) from the initial scan shows a round GGO around the subpleural area in the right lower lobe. Crazy-paving pattern is present within the GGO. Follow-up axial CT images (b, c) were obtained 10 days later. Image (b) shows the round GGO gradually converting to a patchy form and extending down. An encapsulated pleural effusion (c, arrow) is present adjacent to the patchy GGO.