Covid-19 imaging: A narrative review

Abstract

Background: The 2019 novel coronavirus disease (COVID-19) imaging data is dispersed in numerous publications. A cohesive literature review is to be assembled.

Objective: To summarize the existing literature on Covid-19 pneumonia imaging including precautionary measures for radiology departments, Chest CT's role in diagnosis and management, imaging findings of Covid-19 patients including children and pregnant women, artificial intelligence applications and practical recommendations.

Methods: A systematic literature search of PubMed/med line electronic databases.

Results: The radiology department's staff is on the front line of the novel coronavirus outbreak. Strict adherence to precautionary measures is the main defense against infection's spread. Although nucleic acid testing is Covid-19's pneumonia diagnosis gold standard; kits shortage and low sensitivity led to the implementation of the highly sensitive chest computed tomography amidst initial diagnostic tools. Initial Covid-19 CT features comprise bilateral, peripheral or posterior, multilobar ground-glass opacities, predominantly in the lower lobes. Consolidations superimposed on ground-glass opacifications are found in few cases, preponderantly in the elderly. In later disease stages, GGO transformation into multifocal consolidations, thickened interlobular and intralobular lines, crazy paving, traction bronchiectasis, pleural thickening, and subpleural bands are reported. Standardized CT reporting is recommended to guide radiologists. While lung ultrasound, pulmonary MRI, and PET CT are not Covid-19 pneumonia's first-line investigative diagnostic modalities, their characteristic findings and clinical value are outlined. Artificial intelligence's role in strengthening available imaging tools is discussed.

Conclusion: This review offers an exhaustive analysis of the current literature on imaging role and findings in COVID-19 pneumonia.

Keywords: COVID-19; Chest; Computed tomography (CT); Imaging; Novel coronavirus; Sars-Cov2.

Graphical abstract

Fig. 1

Covid-19 imaging features in patients with a positive RT-PCR at different disease stages. Unenhanced axial CT images of the lung show.

1. (a) A left upper lobe unifocal rounded ground glass opacity;

2. (b) Patchy peripheral ground glass opacity with vascular dilatation (Black circle);

3. (c) Multifocal, bilateral subpleural ground glass opacities with traction bronchiectasis (Black circle);

4. (d) Extensive bilateral ground glass opacities associated with thickened interlobular and intralobular septa (Crazy paving) alongside with peripheral consolidations;

5. (e) Subpleural band in advanced-phase disease (Black arrow).

Fig. 2

Covid-19 pneumonia's chest CT imaging features' changes over time.

1. (a,b) Early stage: Ground glass opacities involving the lower lobes with partial crazy paving;

2. (c) Progressive stage: Ground glass opacities extension and increased crazy paving;

3. (d,e) Peak stage: Consolidative opacities, sub-pleural lines (Black arrow) and bronchiectasis.

Fig. 3

A 40 year-old-patient with a history of ten days of fever and coughing presented to the emergency department with an 86% O2 saturation and a 32/min respiratory rate. Frontal chest radiography (a) revealed extensive multilobar consolidations. Chest CT axial (b) and coronal (c) images showed typical severe peak-stage Covid-19 pneumonia imaging features with extensive ground glass opacities, crazy paving pattern, multilobar consolidations and bronchiectasis.

Fig. 4

Axial chest CT image in a patient with severe advanced stage Covid-19 pneumonia complicated by right pneumothorax, pneumomediastinum and sub-cutaneous emphysema under mechanical ventilation.

Fig. 5

Typical Covid-19 imaging features in a 45-year-old woman with a positive RT-PCR. Unenhanced axial (a, b), sagittal (c) and coronal (d) CT images of the lung show multifocal, bilateral, posterior and peripheral rounded consolidations surrounded by ground glass opacities.

Fig. 6

Axial CT image showing bilateral posterior, peripheral, and rounded ground glass opacities in a patient with organizing pneumonia secondary to dermatomyositis; typical Covid-19 imaging features.

Fig. 7

‘Indeterminate Covid-19 appearance’ Chest CT images in 2 patients showing ground glass opacities and consolidations with no specific distribution nor morphology in a case of.

1. (a,b) Acute eosinophilic pneumonia associating interlobular septal thickening, lower lobes air space consolidations and pleural effusions (*).

2. (c,d) Extensive, multifocal, bilateral consolidation in a case of diffuse alveolar hemorrhage.

Fig. 8

Atypical Covid-19 C T features. Unenhanced axial chest CT images showing segmental consolidations with no ground glass opacities, cavitation alongside with centrilobular and tree-in-bud nodules in an active tuberculous infection (a,b).

Fig. 9

Frontal chest radiography showing bilateral air space consolidations in a Covid-19 patient.