Preliminary CT findings of coronavirus disease 2019 (COVID-19)

Abstract

Objectives: Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This paper aims to examine the CT imaging characteristics of COVID-19.

Methods: We evaluated CT images obtained between 10 January 2019 and 16 February 2020 at Taihe Hospital. Scans were conducted 2-6 times per patient and the re-testing interval was 2-7 days. Ninety-five patients with positive SARS-CoV-2 nucleic acid test results were included in this study and we retrospectively analysed their CT imaging characteristics.

Results: Ninety-five patients underwent 2-3 SARS-CoV-2 nucleic acid tests and received a definitive diagnosis of COVID-19. Fifty-three were male and 42 were female, and their mean age was 42 ± 12 years (range: 10 months to 81 years). Sixty-nine patients (72.6%) experienced fever, fatigue, and dry cough, while 15 (15.8%) had poor appetite and fatigue, and 11 (11.6%) had a dry cough and no fever. On CT imaging, early stage patients (n = 53, 55.8%) showed peripheral subpleural ground-glass opacities; these were mainly local patches (22/53, 41.5%), while some lesions were accompanied by interlobular septal thickening. Thirty-four (35.8%) patients were classified in the 'progression stage' based on CT imaging; these patients typically showed lesions in multiple lung segments and lobes (21/34，61.8%), and an uneven increase in ground-glass opacity density accompanied by consolidation and grid-like or cord-like shadows(30.5%). Two patients (2.1%) showed a severe presentation on CT. These showed diffuse bilateral lung lesions, mixed ground-glass opacities and consolidation with cord-like interstitial thickening and air bronchograms, entire lung involvement with a "white lung" presentation, and mild pleural effusion. Six patients in remission (6.3%), visible lesion absorption, fibrotic lesions. Based on clinical signs, 71 (74.7%), 22 (23.2%), and 2 (2.1%) patients had mild or moderate, severe, and critical disease, respectively. Within the follow-up period, 93 patients recovered and were discharged, including the 53 early stage patients and 34 progression stage patients. The length of hospitalisation was 7-28 days (mean: 10 ± 3.5 days). On discharge, lesions were significantly reduced in area and had in many cases completely disappeared, while slight pulmonary fibrosis was present in some patients. One severe stage patient was still hospitalised at the end of the follow-up period and the other severe stage patient died. The overall mortality rate was 1.05%.

Conclusions: Understanding the CT imaging characteristics of COVID-19 is important for early lesion detection, determining the nature of lesions, and assessing disease severity.

Fig. 1

Early changes: A 41-year-old male COVID-19 patient with a history of occupational exposure to the disease who had experienced fever for 2 days. A) An initial plain axial chest CT image showed small patchy ground-glass opacities (arrow) located along vascular bundles in the subpleural region of the left upper lobe lingular segment; B) A plain axial CT image taken 2 days later showed that the ground-glass opacities had increased in area and density; C) A plain axial CT image taken after 9 days showed that the lesion area had significantly increased with an uneven increase in density, and an air bronchogram and vascular shadows were observed; D) A plain axial CT image taken after 15 days showed that the density of ground-glass opacities was decreased and partial absorption was observed; E) A plain axial CT image taken after 20 days showed that the lesions in the left upper lobe lingular segment were practically absorbed; a SARS-CoV-2 nucleic acid test taken at this time was negative.

Fig. 2

Early changes: A 7-year-old female COVID-19 patient who had experienced a fever and fatigue for 5 days; she had a history of contact with relatives who returned from Wuhan. A) A plain axial CT image showed cord-like consolidation in the left lower lung lobe with even density and blurred boundaries, and an air bronchogram was observed(arrow), as is seen in lobar pneumonia; B) A plain axial CT image taken 6 days later showed that the consolidation had been partially absorbed compared with the previous image and the lesion boundaries were slightly blurred; C) A plain axial CT image taken after 16 days showed that left lower lung lobe lesions had been virtually absorbed; a SARS-CoV-2 nucleic acid test taken at this time was negative.

Fig. 3

Progressive changes: A 45-year-old female COVID-19 patient who had experienced a fever for 7 days and had a sore throat, dyspnoea, and a history of a short residence in Wuhan. A, B) Plain axial CT images showed multiple bilateral subpleural ground-glass opacities(arrow); the long axis of the lesions was vertical to the thoracic wall; C, D) Plain axial CT images taken 7 days later showed diffuse bilateral subpleural and central patchy ground-glass opacities involving multiple lung lobes.

Fig. 4

Progressive changes: A 69-year-old female COVID-19 patient with a history of residence in Wuhan who reported a productive cough accompanied by systemic muscle soreness for 14 days. A–D) Plain axial CT images showed patchy ground-glass opacities and grid-like changes bilaterally in the subpleural areas of the lung periphery, with a “crazy-paving sign”(arrow); E–H) Plain axial CT images taken 3 days later showed an increased lesion area and an uneven increase in ground-glass opacities bilaterally in the lung periphery accompanied by consolidation. Ground-glass opacities and grid-like shadows were also present inside the lungs, accompanied by interlobular septal thickening.

Fig. 5

Early to Severe changes: A 67-year-old male COVID-19 patient with a history of residence in Wuhan who reported fever, fatigue, and poor appetite for 6 days. A–D) Initial plain axial chest CT images showed bilateral bronchial wall thickening and mild dilation, bilateral centrilobular emphysema, and bilateral lower lung interstitial thickening; E–H) Plain axial CT images taken 4 days later showed diffuse patchy ground-glass opacities in both lungs (arrow); in the left lung the lesions have a fan-like distribution and grid-like shadows, and vascular thickening is also seen; I–L) Plain axial CT images taken after 7 days showed a significant expansion of the lesion area with multiple patchy and grid-like shadows and areas of consolidation in both lungs; M–P) Plain axial CT images taken after 10 days showed diffuse bilateral lung lesions, with a “white lung” presentation.

Fig. 6

Mild or moderate changes: A 28-year-old male COVID-19 patient who had experienced fever for 1 day, but reported no history of contact with people from the epidemic region or confirmed COVID-19 patients. Clinical type: mild or moderate. A,B) Initial plain axial chest CT images did not show any apparent abnormalities; C,D) Plain axial CT images taken after 3 days showed patchy ground-glass opacities and cord-like shadows bilaterally in the subpleural regions(arrow); these are more significant in the left lung; E, F) Plain axial CT images taken after 6 days showed increased areas of subpleural ground-glass opacity bilaterally accompanied by consolidation and cord-like shadows, as well as interlobular septal thickening; G, H) Plain axial CT images taken after10 days showed that the lesions were mostly absorbed and there were fibrous cord-like shadows with clear boundaries in the subpleural area; a SARS-CoV-2 nucleic acid test taken at this time was negative.

Fig. 7

Severe changes: A 78-year-old female COVID-19 patient who reported an intermittent fever and cough for 1 week, and had a history of contact with family members from the epidemic region. Clinical type: severe. A,B) Plain axial chest CT images; C, D) Plain coronal chest CT images. All images showed extensive ground-glass opacities and areas of consolidation bilaterally in the lung periphery and subpleural areas (arrow); these are more significant in the lower lungs. Air bronchograms and vascular thickening shadows were also observed.