Pictorial guide for variants of Covid-19: CT imaging and interpretation

Abstract

Typical radiologic images of Covid-19 pneumonia consists in a wide spectrum of chest manifestations, which range from peripheral predominant ground-glass opacities to an organizing pneumonia pattern, with additional features including crazy-paving, consolidations, fibrotic streaks and linear opacities. With variants imaging profile of Covid-19 evolves, producing relatively atypical/indeterminate CT pattern of pulmonary involvement, which overlap with imaging features of a variety of other respiratory diseases, including infections, drug reaction and hypersensitivity pneumonia. Our knowledge of these radiological findings is incomplete and there is a need to strengthen the recognition of the many faces of Covid-19 pneumonia.

Figure 1.

Axial CT images (a, b) of a 34-year-old male infected by SARS-CoV-2 α variant (3 days since symptoms onset). CT showed centrally and peripherally located multifocal GGO opacities with mainly involvement of upper lobes.

Figure 2.

A 54-year-old female COVID −19 patient (2 days since symptoms onset) infected by Omicron variant. CT scan shows single ground glass opacity with rounded appearance, in the right upper lobe.

Figure 3.

A 78-year-old male arriving at the emergency department with fever. Axial (a) and coronal reformatted (b) CT images documented a subpleural GGO in right lower lobe. Notably, there were signs of consolidation in the context of the lesion. The real-time reverse transcription polymerase chain reaction test was positive for Sars-Cov-2 infection. Subsequent genetic sequencing detected α variant. GGO, ground-glass opacity.

Figure 4.

A 57-year-old COVID-19 patient (δ variant) presenting fever and dry cough for 3 days. Axial (a) and coronal (b) reformatted CT images showed pneumonia with isolated lobar consolidation in the right lower lobe.

Figure 5.

A 32-year-old female infected with COVID-19 (δ Variant): axial unenhanced CT image showed focus of central ground glass nodule surrounded by an inner ring of air and an outer ring of ground glass (white circle). This appearance ressembles a bullseye.

Figure 6.

The “bullseye sign” in a 44-year-old male COVID-19 patient (Omicron variant) with fever and dry cough for 7 days.

Figure 7.

Axial CT image of a 25-year-old male Covid-19 patient (γ variant) showed perifissural small centrilobular nodules connected to linear branching opacities (white box), in right upper lobe.

Figure 8.

Axial CT image of a 78-year-old male Covid-19 patient (α variant), showed tree-in-bud opacities in right upper lobe with bronchial wall thickening.

Figure 9.

CT images of a 58-year-old male patient with confirmed COVID-19 pneumonia (γ variant). Axial (a) and coronal reformatted (b) images showed diffuse lung involvement with ill-defined centrilobular GGO and subpleural sparing. GGO, ground-glass opacity.

Figure 10.

A 42-year-old female COVID-19 patient (γ variant) presenting fever and chills for 4 days. Axial (a) and coronal reformatted (b) images showed bilateral ill-defined centrilobular GGO. GGO, ground-glass opacity.

Figure 11.

Axial CT image of a 68-year-old patient with COVID-19 pneumonia (δ variant), with symptoms for 4 days, showed bilateral extensive consolidations. The patient died 5 days later.

Figure 12.

Axial CT image slices of a female COVID-19 patient (α Variant) of 81-year-old. a) CT scan, performed after 1 day from symptoms onset, showed a mixed pattern of GGO and consolidation in upper lobes with peribronchovascular involvement. b) CT obtained after 5 days from symtoms onset. Lesions increased with higher density and superimposed thickening of the interlobular septum in both lungs, with predominant dorsal consolidations.

Figure 13.

Evolution of CT findings in a 56-year-old female COVID-19 patient (δ variant). (a) CT scan, performed after 3 days from symptom onset, showed GGO with superimposed inter- and intralobular septal thickening (crazy-paving pattern) in upper lobes. (b) Scan obtained on day 7 from symptom onset, showed peripheral consolidations. In apical segment of right lower lobe, CT demonstrated rounded consolidation with cavitation in context.

Figure 14.

A 53-year-old female COVID-19 patient (Omicron variant), presenting with dry cough, dyspnea and fever up to 39° for 3 days. Axial CT image showed large amount of pericardial effusion.