Imaging of coronavirus disease (COVID-19): a pictorial review

Abstract

Coronavirus disease (COVID-19), caused by a highly contagious novel coronavirus, has seen a rapid surge of cases over the past 6 months spreading to more than 215 countries and posing a global threat to mankind. Reverse transcriptase-polymerase chain reaction (RT-PCR) from pharyngeal swabs is considered the gold standard for diagnosis of this disease. Portable chest radiography (CXR), point of care ultrasound, and computed tomography (CT) are crucial modalities in diagnosis and follow-up. Portable CXR can help in patients who are clinically unstable, and also to prevent the cumbersome process of steriliastion after every CT scan. However, chest CT is useful as a problem-solving tool, to look for progression and complications associated with the disease. In a few cases, in our experience (as has also been documented by others), RT-PCR was negative in early disease, and CT chest was able to detect the radiologi-cal findings raising suspicion of COVID-19. With this pictorial review, we aim to describe and illustrate the typical, and a few atypical, radiological findings of this disease.

Keywords: ARDS; computed tomography; coronavirus; ground glass opacity; pneumonia; radiograph.

Figure 1

Peripheral predominant pattern of COVID-19 pneumonia. A) Schematic diagram depicting a peripheral predominant pattern of disease. B-D) Frontal chest radiography of 3 different patients with COVID-19 show peripheral, reticular, and patchy alveolar opacities (red arrows) in both lung fields

Figure 2

Lower lobe predominant pattern of COVID-19 pneumonia. A) Schematic diagram depicting a lower lobe predominant pattern of disease. B-D) Frontal chest radiography of 3 different patients with COVID-19 show patchy opacities with lower lobe predominance (red arrows)

Figure 3

Multifocal pattern of COVID-19 pneumonia. A) Schematic diagram depicting a multifocal pattern of disease. B-D) Frontal chest radiography of 3 different patients with COVID-19 show areas of patchy alveolar opacities distributed in both lung fields (red asterisks)

Figure 4

Diffuse pattern of COVID-19 pneumonia. A) Schematic diagram depicting a diffuse pattern of disease. B-D) Frontal chest radiography of 3 different patients with clinical diagnosis of acute respiratory distress syndrome due to COVID-19 show varying degrees of parenchymal opacification in both lung fields

Figure 5

A 50-year-old man with COVID-19 pneumonia came with high-grade fever and loss of appetite for 2 days. The initial nasopharyngeal swab was negative for SARS-CoV-2. However, (A) frontal chest radiography on day 1 of presentation shows subtle ill-defined patchy opacity in the right lower zone (red arrow). B) Coronal reformatted computed tomography chest image shows a peripheral area of ground-glass opacity with interlobular septal thickening (crazy-paving appearance) in the right lower lobe. Follow-up radiographs on day 14 (C) and day 28 (D) showed subsequent resolution of the findings

Figure 6

Ultrasound (US) findings in COVID-19 pneumonia. A) Grey-scale US image of the normal lung using a linear array transducer shows a continuous thin pleural line (yellow arrowhead) with multiple reverberation artefacts parallel to it – A lines (red arrowhead). B) A 54-year-old man with COVID-19 pneumonia. US performed using a curvilinear array transducer shows multiple laser-like hyperechoic lines erasing the A lines – B lines (red arrows). C) Confluent B-lines in the same patient as (B) – Waterfall sign (red asterisk). D) A 62-year-old woman with COVID-19 pneumonia. US performed using a linear array transducer showing thickening and interruption of the pleural line (yellow arrow) with subpleural consolidation (yellow asterisk)

Figure 7

Distribution of ground-glass opacities on axial sections of high-resolution computed tomography chest in 2 different patients with COVID-19 pneumonia. A) A 37-year-old man, 3 days after symptom onset – subtle GGOs in the periphery of both lung fields (red arrows). B) A 49-year-old man, 5 days after symptom onset – multifocal GGOs (red arrows) with vascular thickening (yellow arrowhead) in both lung fields

Figure 8

Axial high-resolution computed tomography (HRCT) chest images. A) Confluent ground-glass opacities with a peripheral and subpleural distribution in both lung fields (red asterisks) in a 47-year-old woman with significant hypoxia. B) A 52-year-old man presented to the emergency room with breathlessness and poor oxygen saturation for three days. Axial HRCT image shows extensive, diffuse GGOs in both lung fields (red arrows) with few areas of spared lung parenchyma. Nasopharyngeal swabs in both patients confirmed COVID-19 pneumonia

Figure 9

A) Coned down axial high-resolution computed tomography chest image of a patient with COVID-19 shows rounded ground-glass opacity (GGO) in the right upper lobe (red arrow). B) Coned down axial computed tomography image in a different patient shows vascular thickening (red arrow), in a background of interlobular septal thickening with GGOs (crazy paving appearance). The normal calibre of a peripheral vessel is shown for comparison (yellow arrow)

Figure 10

Axial thin sections of chest high-resolution computed tomography (HRCT) of patients with COVID-19 pneumonia in first and the second week of symptoms. A) A 50-year-old man with ground-glass opacities (GGOs) and interlobular septal thickening giving a crazy paving appearance in the superior segment of the right lower lobe (red arrowheads). B) Coned down axial HRCT chest image shows patchy consolidation with a traversing patent bronchus – air bronchogram (red arrowheads) in the left lower lobe of a 26-year-old female presenting with high-grade fever. The surrounding GGO gives the appearance of a halo (halo sign). This is better depicted in (C) obtained at another level (red arrowheads). D) A 37-year-old female with COVID-19 pneumonia. HRCT chest obtained 9 days after symptom onset, shows perilobular consolidation (red arrowheads) with reticular densities in both upper lobes giving rise to a reverse halo – atoll sign (red arrow). E) Lower sections of the chest in the same patient as (D) shows ill-defined GGOs in the posterobasal segment of the right lower lobe (red arrow) with adjacent pleural thickening (red arrowheads). F) Bronchial wall thickening (red arrowhead) in a 40-year-old male. Note the subtle GGO in the medial basal segment of the right lower lobe (yellow arrowhead)

Figure 11

Rounded lucencies within an area of ground-glass opacity in 2 different patients of COVID-19 pneumonia – air bubble sign (yellow arrows). These lucencies have an imperceptible wall, which differentiates them from a normal bronchus (red arrowhead)

Figure 12

A 38-year-old diabetic female presented with two days of cough, fever, and breathlessness. A) Initial high-resolution computed tomography chest shows subtle ground-glass opacities (GGOs) in both lower lobes (red arrows). However, her condition in the ward worsened over the next 10 days. A repeat scan (B) shows multifocal dense GGOs with forming consolidations in both lung fields suggestive of severe stage of COVID-19 pneumonia

Figure 13

Typical findings of dissipative stage of COVID-19 pneumonia on high-resolution computed tomography chest. A-B) A 47-year-old man with symptoms for 12 days. Axial (A) and coronal (B) chest computed tomography (CT) images show curvilinear fibrotic lines parallel to the chest wall in both lung fields (red arrowheads) with extensive reticulations in the upper lingula (red arrow) and traction bronchiectasis (blue arrow). Also note fibrotic strands with adjacent pleural thickening and bronchiectasis in the right upper lobe (yellow arrow) as a sequalae to prior tubercular infection. C) Axial CT chest image in a 42-year-old female shows curvilinear opacities parallel to the chest wall (red arrows) with adjacent reticulations. D) Similar findings are also seen in another patient in dissipative stage of the disease (red arrow). Also note associated traction bronchiectasis in the left upper lobe (yellow arrowhead)

Figure 14

Temporal changes in a 55-year-old man with COVID-19 pneumonia on chest high-resolution computed tomography. A) Axial computed tomography (CT) chest images shows ground-glass opacities (GGOs) (red arrowhead) with interlobular septal thickening and formation of consolidations in both lung fields (red arrow). B) Follow-up chest CT performed after 1 month shows reduction in GGOs as compared to (A) with residual fibrosis (red arrows), suggesting progression to dissipation stage

Figure 15

Representative axial high-resolution computed tomography (HRCT) chest images depicting CO-RADS. A) Normal HRCT chest: CO-RADS 1. B) Centrilobular nodules with tree-in-bud configuration in the right lung (red arrowheads) – bronchiolitis, later diagnosed as active pulmonary tuberculosis. CO-RADS 2. C) Dense consolidation with air bronchogram (red arrow) and surrounding ground-glass opacity (GGO) in a patient with Klebsiella pneumonia: CO-RADS 3. D) Peribronchovascular GGOs in the left lung (blue arrows): CO-RADS 4. Nasopharyngeal swab was positive for SARS-CoV-2. E) Peripheral and subpleural predominant multifocal GGOs with interlobular septal thickening – crazy-paving appearance (red arrows) in both lungs: CO-RADS 5. This was later proven to be COVID-19 pneumonia. F) Extensive, peripheral confluent bilateral GGOs with septal thickening in a patient with acute respiratory distress syndrome secondary to COVID-19 pneumonia

Figure 16

Total Severity Score (TSS) calculation in COVID-19 pneumonia using high-resolution computed tomography chest. Axial (A) and coronal (B) chest computed tomography (CT) images in a 42-year-old man with clinically severe COVID-19 pneumonia shows multifocal peripheral ground-glass opacities and consolidations in both lungs. Sagittal reformatted images of the right lung (C) and left lung (D) show less than 25% involvement of right middle lobe (score 1); right upper and both lower lobes have a score of 2 each, and left upper lobe has a score of 3. The TSS in this patient was 10, correlating with the clinical severity

Figure 17

A 25-year-old man with COVID-19 pneumonia presenting with sudden onset breathlessness. A) Computed tomography (CT) pulmonary angiogram image shows an eccentric partial thrombus in the right descending pulmonary artery extending into the right middle lobe branch (red arrows). B) Axial CT image with lung window at the same level shows multifocal ground-glass opacities in both lung fields

Figure 18

Atypical computed tomography (CT) chest findings in COVID-19 pneumonia. A) Axial chest CT image in a 32-year-old man in dissipative stage of disease shows an enlarged right paratracheal lymph node. B) Axial high-resolution computed tomography chest image in the same patient shows interlobular septal thickening with traction bronchiectasis and ground glass opacities suggestive of progression to interstitial lung disease. C-D) Axial chest CT images in 2 different patients with COVID-19 pneumonia show small subsolid nodules (red arrows)

Figure 19

Different stages of COVID-19 pneumonia on chest high-resolution computed tomography