Comments Abstract
Coronavirus disease (COVID-19) is an illness caused by a novel coronavirus that has rapidly escalated into a global pandemic leading to an urgent medical effort to better characterize this disease biologically, clinically, and by imaging. In this review, we present the current approach to imaging of COVID-19 pneumonia. We focus on the appropriate use of thoracic imaging modalities to guide clinical management. We also describe radiologic findings that are considered typical, atypical, and generally not compatible with COVID-19. Furthermore, we review imaging examples of COVID-19 imaging mimics, such as organizing pneumonia, eosinophilic pneumonia, and other viral infections.
In December of 2019, a novel coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing a disease known as coronavirus disease (COVID-19), emerged in Wuhan, China, and quickly spread to become a global pandemic. This virus has typical, but not specific, clinical and imaging characteristics that have spurred interest in devising criteria for estimating the likelihood of infection in an effort to improve the care of these patients, help in the identification of associated morbidities, and optimize the use of global healthcare resources in an effort to address concerns about potential overwhelming of healthcare systems. The appropriate use of imaging in this setting has been a topic of debate in the medical community and continues to evolve as we learn more about this novel disease.
There are a number of disease characteristics that influence and drive the use of imaging, including the reported false-negative rate of SARS-CoV-2 reverse transcriptase–polymerase chain reaction (RT-PCR) testing, which may prompt repeat PCR testing, and possibly imaging, in patients in whom there is a strong clinical suspicion of COVID-19. In addition, COVID-19 is associated with an increasing number of recognized serious thoracic complications, such as pulmonary arterial embolism, acute respiratory distress syndrome (ARDS), and superimposed bacterial pneumonia, all scenarios in which imaging plays a role in either diagnosis or follow-up. In this review, we will examine the current literature and discuss the evidence for recent imaging guidelines concerning the use of imaging in the diagnosis and management of COVID-19 in the chest.
Clinical severity of COVID-19 infection is variable and multifactorial with the majority of patients presenting with mild symptoms, most commonly fever and dry cough. Others mount an intense immunologic response to the virus accelerated by the release of inflammatory cytokines, which in turn can ultimately lead to acute hypoxemic respiratory failure and multisystem collapse. Susceptibility to this overly robust immunologic response is not fully understood and is thought to be multifactorial with variables such as the patient’s human leukocyte antigen complexes, release of inflammatory cytokines, and extent of T-cell activation potentially playing a role (1–3).
Current standard of care for evaluation of suspected COVID-19 is RT-PCR testing for detection of viral RNA in nasal, nasopharyngeal, or oral secretions. More recently, rapid COVID-19 serology for N-protein immunoglobulin M or immunoglobulin G antibodies in human peripheral blood has become available and generates results in minutes rather than hours. However, they are not currently recommended for use in the acute setting by the Centers for Disease Control and Prevention likely because they detect the immune response to the virus, which may lag after the clinical manifestations (4), the immune response is variable and can persist after acute infection, and the sensitivity and specificity of these tests is also highly variable.
A major caveat with currently available COVID-19 testing is the wide range of test characteristics that limit its effectiveness for disease detection. For example, sensitivity ranges from 38% to 88% with reported specificity approaching 100% for detection of infection with RT-PCR (3, 5–9). In addition to variability introduced by the type of test, the accuracy of COVID-19 testing may be also influenced by the site of sample collection (e.g., nasopharyngeal vs. oropharyngeal), method of sample collection (e.g., swab vs. bronchoalveolar lavage, with the latter, which may be more accurate but more invasive and may put health workers at increased risk, being recommended in the setting of progressive severe disease and negative upper respiratory specimens), and timing of sampling relative to development of symptoms (10–13). Thus, a single negative result must be evaluated with caution, and indeed, a repeat test may be necessary to increase diagnostic yield. However, even two negative RT-PCR results have been reported in up to 21% of patients that were eventually diagnosed with active COVID-19 infection in a study by Xiao and colleagues (14).
False-negative results have consequences; inadequate contact precautions may be undertaken and patients may unknowingly spread the infection to others. The disease may also rapidly escalate, particularly in those who are at high risk for serious disease, such as the elderly (15), and those with underlying comorbidities including cancer (16) and chronic lung, heart, and renal disease (17), all organs at risk because of organ-specific ACE-2 (angiotensin-converting enzyme) receptor expression (18).
Recently published Fleischner Society guidelines on imaging use for patients with COVID-19 do not recommend imaging in patients without known risk factors for disease progression presenting with mild symptoms regardless of RT-PCR results. The guidelines additionally do not recommend daily chest radiographs in stable intubated patients with COVID-19. In patients with moderate to severe symptoms, imaging of the chest is recommended regardless of pretest probability of COVID-19, except in resource-constrained settings where imaging should be reserved for patients with high pretest probability of disease. In addition, imaging is recommended in the setting of worsening respiratory status in patients with confirmed disease and may be indicated if alternative diagnoses are sought (19).
In patients with suspected COVID-19 in whom imaging of the chest is indicated, the choice between chest radiograph or computed tomography (CT) depends on the preferences of the clinical care team, the clinical question to be answered, the policy of the local radiology department, and the availability of local imaging resources. In addition, although the findings of COVID-19 are not specific on either modality, chest CT is more sensitive than chest radiography in the detection of COVID-19 pneumonia (20) and may be preferred in certain clinical settings. CT has been demonstrated to detect disease in asymptomatic patients, and there is some evidence that CT can outperform the sensitivity of COVID-19 testing with RT-PCR (21, 22), although this is controversial (12). At this time, CT may play a role as an adjunct to COVID-19 RT-PCR testing, with more research needed to establish the optimal role of CT in patients suspected of COVID-19 infection (23).
In cases of known or suspected COVID-19, chest radiography may be useful if the clinical question is to assess the extent of disease and in many centers will be the initial tool of radiologic patient assessment (24). For initial detection of COVID-19 infection, the overall sensitivity of chest radiography is 69–75%, with lower sensitivity earlier in the course of disease. Because the severity of imaging findings peaks around 10–12 days from onset of symptoms, the specificity and positive predictive value of radiographic findings are highly dependent on the overall prevalence of disease and timing of imaging relative to start of symptoms (20, 25, 26). Chest radiography may assist in risk stratification for development of severe disease; two recent publications suggest that scoring systems based on radiographic findings reporting results can predict the need for hospitalization and intubation (15, 20, 27–29). In addition to assessing the pulmonary changes of COVID-19 infection, chest radiographs are used for monitoring of medical support devices in critically ill patients and to assess for potential complications of COVID-19 infection such as pneumothorax or superimposed bacterial pneumonia. Portable chest radiography is also more widely available and the equipment is easier to sanitize after use compared with CT. Additionally, radiographs can be obtained through a glass barrier, which reduces exposure of radiology technologists to COVID-19–positive patients (30).
As mentioned above, the initial chest radiograph may be normal even in the setting of severe disease. The imaging findings of COVID-19 on chest radiography, when present, include both interstitial and alveolar patterns, although both patterns may coexist in a subset of patients, similar to CT. Interstitial abnormalities most commonly include reticular and reticulonodular pattern, whereas most common alveolar findings include subtle hazy pulmonary opacities (correlating to ground-glass opacities on CT), with or without consolidations (31–33). The most commonly reported distribution is bilateral and peripheral with a lower lobe predominance (Figure 1); unilateral distribution of disease is possible but less common. When there is progression to more severe disease, these pulmonary opacities become more diffuse and coalescent and are sometimes accompanied by coarsening of the interstitial markings suggesting the presence of acute lung injury. The presence of pleural effusions or cavitation in the affected lung is uncommon (20, 29, 34).
Figure 1. Imaging findings of COVID-19 pneumonia on chest radiography. A 71-year-old male with a 4-day history of weakness, poor appetite, myalgias, and low-grade fever with possible contact history to a person known to have COVID-19. (A) Chest radiography demonstrates a focal peripheral opacity in the left mid-lung zone (white arrow). Because of a negative respiratory pathogen panel and concern for alternative diagnoses, a CT was ordered. (B and C) Axial unenhanced chest CT performed the same day revealed bilateral, peripheral, and predominantly ground-glass opacities (arrows) and was considered to be consistent with a high probability of COVID-19 pneumonia. Reverse transcriptase–polymerase chain reaction confirmed COVID-19 infection. (D) A chest radiograph obtained 9 days later revealed more extensive bilateral, basilar predominant, peripheral opacities (arrows). COVID-19 = coronavirus disease; CT = computed tomography.
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The probability of positive CT findings of COVID-19 pneumonia increases with symptom duration (sensitivity, 70–97%) (21, 35); therefore, a negative CT exam does not exclude COVID-19 infection, particularly when imaging occurs within the first 2 days of infection (5). The severity of imaging findings on CT also correlates with the likelihood of initial positivity of the RT-PCR result, with consolidative opacities less likely to be present in patients with an initially negative RT-PCR result (22). The reported specificity of CT for COVID-19 pneumonia is highly variable (7–100%), attributed in part to the variable prevalence of other diseases with overlapping imaging features with COVID-19 pneumonia. In addition, owing to the rapid dissemination of medical data needed in the setting of this novel pandemic, some studies suffer from biases and shortcomings in study design that may yield apparently higher specificities of CT for COVID-19 (12, 21, 23, 35). In addition to detecting pulmonary findings of COVID-19 pneumonia, CT is also valuable for characterizing associated complications of this disease, including detecting pulmonary arterial embolism on contrast-enhanced CT, and has higher sensitivity than chest radiographs for assessment of the likelihood of ARDS or superimposed bacterial pneumonia. CT is also valuable in suggesting alternative diagnoses, such as aspiration pneumonia or pulmonary edema, which may be indistinguishable from COVID-19 on chest radiography.
Point-of-care ultrasound (POCUS), performed at the bedside with ultraportable handheld probes, has become more common during this pandemic, particularly in parts of the world where access to CT is limited or there is greater availability of handheld ultrasound devices. Historically, POCUS had been primarily used in the emergency department, in intensive care units, in the setting of trauma, and in places with limited imaging resources. However, more recently, POCUS is increasingly being integrated into care provided by practitioners of general internal medicine, hospitalist medicine, and family medicine (36, 37). Chest ultrasound to detect pericardial effusion, pleural effusion, interstitial edema, pneumothorax, and consolidation has been reported to have a diagnostic accuracy as high as 90–100% for emergent lung findings (38, 39). Although the data are still maturing in the field, chest ultrasound may be more sensitive and specific than chest radiography, and less so than chest CT, for the detection of pulmonary complications in ventilated patients with acute respiratory failure (40).
In the setting of the COVID-19 infection, POCUS may similarly have a role in detecting coexisting conditions or suggesting alternative diagnoses. For example, POCUS may have utility in diagnosing moderate to severe ARDS (41), which can complicate COVID-19 pneumonia. In addition, there are findings typical of COVID-19 pneumonia on POCUS including the appearance of B lines, which reflect the presence of an interstitial abnormality, or presence of subpleural consolidation (Figure 2), although these findings are nonspecific. Although the positive predictive value of imaging findings of COVID-19 infection on POCUS will be influenced by prevalence of disease (42–44), there is some limited evidence to suggest that POCUS can be useful in the management of patients suspected of COVID-19 infection in certain clinical settings (34, 37).
Figure 2. Point-of-care ultrasonography of the chest. (A) Normal sonographic findings of the lung including a thin pleural line (large arrow) and horizontal reverberation artifact called A-lines (thin arrows). (B) A lung ultrasound of a 73-year-old male who presented with acute hypoxemic respiratory failure and acute respiratory distress syndrome related to COVID-19 pneumonia. Solid arrows indicate coalescent B-lines that extend to the bottom of the viewing screen, obliterating A-line artifacts in their path. The open arrow demonstrated rare A-line artifacts persistent in some of the lung. (C) A magnified image of the superficial aspect of image B shows irregular pleura and subpleural consolidation seen in COVID-19 pneumonia. COVID-19 = coronavirus disease.
[More] [Minimize]As a result, POCUS has been explored during this COVID-19 pandemic in healthcare settings where imaging resources are overwhelmed or limited, when patients are too ill to be transported to the radiology department for imaging, or when patients are rapidly deteriorating, offering a “one-stop shop” for assessment of lung, heart, and potential venous thromboembolism (45). Anecdotally, at our institution, emergency physicians are using quantitative data from thoracic ultrasound to assess for the extent of lung involvement in patients with COVID-19, and intensivists are using POCUS to assess for changes in pulmonary consolidation that might aid in predicting outcomes.
In an effort to provide clinical reports that convey the degree of confidence of COVID-19 pneumonia in patients under investigation, several groups have proposed CT reporting criteria and scoring systems for COVID-19 (25, 46–48). Familiarity with these systems provides an understanding of the common CT imaging findings of COVID-19 pneumonia, may increase confidence for this diagnosis, when present, and highlights findings that suggest an alternative diagnosis. As an example to illustrate these points, we will examine the Radiological Society of North America (RSNA) consensus criteria for CT reporting in the setting of suspected COVID-19 pneumonia considering typical and less common manifestations on CT (46).
The typical findings of COVID-19 pneumonia on CT include a peripheral distribution of bilateral rounded ground-glass opacities, which was reported to be present in up to 88% of disease. A variable component of consolidation can also be present and usually develops later in the course of the disease (49, 50). In some cases, there are intralobular lines within these ground-glass opacities forming an imaging pattern known as “crazy paving,” which is also seen in a range of other pulmonary conditions including pulmonary edema. Less commonly, COVID-19 pneumonia can assume a “reverse halo sign” (5), an imaging appearance originally described for cryptogenic organizing pneumonia and that can be observed in a range of other conditions (51). The reverse halo sign is characterized by a central region of ground-glass opacity surrounded by a rim of more dense opacity and, when present, occurs late in the course of the disease (52). With worsening disease, there is often increased pulmonary consolidation and ground-glass opacification, which becomes more extensive and confluent (Figure 3). When ground-glass opacities are present on CT without a definitive peripheral distribution or rounded morphology or they are predominantly consolidative opacities, the RSNA consensus guidelines recommend that this be considered of intermediate confidence for COVID-19 pneumonia. In the setting of intermediate-confidence imaging findings, an alternate diagnosis should be sought if clinical confidence is low for COVID-19 infection.
Figure 3. CT imaging findings of COVID-19 pneumonia in a 53-year-old male with a 2-week history of progressive shortness of breath, dry cough, headache, myalgias, and diarrhea. He also reported recurrent low-grade fevers over the prior week and had pulse oximetry of 80–90%. A reverse transcriptase–polymerase chain reaction test for COVID-19 was performed in an urgent care and was pending (later confirmed to be positive). Given the hypoxia, an unenhanced chest CT was obtained; axial (A) and coronal (B) images revealed bilateral peripheral ground-glass opacities (arrow) in a lower lobe predominance, some with round configuration. A reverse halo sign is seen (arrowhead). (C and D) Unenhanced axial CT images obtained 8 days after initial CT for the same patient demonstrate progression of disease with more extensive, confluent opacities and a more prominent consolidative component and small bilateral pleural effusions (arrows). COVID-19 = coronavirus disease; CT = computed tomography.
[More] [Minimize]Finally, there are several CT imaging findings that are common in other pulmonary infections but are considered atypical for COVID-19. For example, discrete centrilobular nodules, such as “tree-in-bud opacities,” seen in the setting of infectious or noninfectious bronchiolitis have not been commonly reported in COVID-19 imaging literature to date. The presence of a single lobar consolidation is typical of bacterial or aspiration pneumonia (53) but rarely seen in COVID-19 pneumonia. Similarly, lung cavitation within consolidation on CT is more likely a result of a necrotizing pneumonia of bacterial or fungal origin and can also be seen in some noninfectious processes such as vasculitis (54). The presence of bilateral smooth interlobular septal thickening with pleural effusion suggests pulmonary edema. Thoracic lymphadenopathy is reported to be uncommon with COVID-19 pneumonia (49). Finally, the presence of a few sparse ground-glass opacities as the only finding on CT is also considered atypical for COVID-19 pneumonia. In these cases of CT findings atypical for COVID-19 pneumonia, the RSNA guidelines recommend that an alternate diagnosis should be considered.
In addition to the RSNA consensus guidelines, several other COVID-19 CT imaging reporting criteria have been proposed (25, 47, 48). For example, Prokop and colleagues (47) proposed a set of CT reporting criteria, termed the COVID-19 Reporting and Data System, with a reported area under the curve of 0.91 (95% confidence interval, 0.85–0.97) for predicting RT-PCR outcome when using a five-grade scale of diagnostic confidence. In this COVID-19 Reporting and Data System, similar to the RSNA criteria, the presence of bilateral ground-glass opacities, with or without consolidations, in peripheral or juxtafissural distribution, was considered most characteristic of COVID-19 pneumonia and had the highest correlation with a subsequent positive RT-PCR.
Another set of CT imaging reporting criteria proposed by Salehi and colleagues (48) used data from 37 CT imaging reports on COVID-19–positive patients to compose a lexicon and reporting system (COVID-RADS) with a three-tiered grading scale (low, moderate, or high level) to describe the level of suspicion for pulmonary involvement by COVID-19. As with other COVID-19 CT imaging reporting criteria, the presence of multifocal ground-glass opacities, with or without consolidations, was considered as having a high clinical suspicion for COVID-19 infection. In addition, features reported to be more common late in COVID-19 pneumonia include a consolidation-predominant pattern, linear opacities, crazy-paving pattern, or “melted sugar sign,” the latter term referring to the gradual resorption of consolidations regressing back to ground-glass opacities (55). Recently proposed CT imaging guidelines by the Canadian Association of Radiologists described by Dennie and colleagues (25) also recommends a three-tiered system for categorizing CT, and also chest radiograph, imaging findings. In the Canadian guidelines, these categories are recommended to be defined as “typical,” “nonspecific,” and “negative” for COVID-19 pneumonia.
In summary, there are multiple CT reporting guidelines and scoring systems that have been developed to aid clinical management by providing familiarity with the imaging findings typical and atypical for COVID-19 pneumonia and provide confidence levels of likelihood of disease. The accuracy of these criteria has yet to be rigorously studied, and these guidelines will likely continue to evolve as we learn more about this disease.
There are a number of disease entities that can have an imaging appearance that closely resembles COVID-19 pneumonia, for example, organizing pneumonia, either cryptogenic or on the basis of known etiology of lung injury such as drug toxicity or vaping (56), and acute eosinophilic pneumonia (57). Similar to COVID-19 infection, these entities manifest as ground-glass or consolidative pulmonary opacities, can be rounded in configuration, and classically occur in a peripheral distribution (58). In addition, organizing pneumonia and eosinophilic pneumonia can assume the “reverse halo” or “atoll sign” (51) that has been described to sometimes occur in COVID-19 pneumonia (5). These entities can be indistinguishable from COVID-19 although may be suggested if pulmonary opacities are shown to be slowly changing (e.g., over several months), are steroid responsive, or occur in a clinical setting more suggestive of an alternate diagnosis to COVID-19 pneumonia, such as when repeat RT-PCR for SARS-CoV-2 is consistently negative. Although acute eosinophilic pneumonia can be quite rapid in evolution on imaging, this diagnosis may be suggested by a concomitant peripheral eosinophilia or high eosinophilic count on cytological analysis of bronchoalveolar lavage samples. Finally, although other viral pneumonias may have imaging features that overlap with COVID-19, a clear peribronchial distribution and presence of bronchiolitis is suggestive of an alternate diagnosis noting that viral superinfection is rare and the presence of atypical imaging features in a patient with proven COVID-19 should raise the possibility of bacterial superinfection. (Figure 4).
Figure 4. CT imaging mimics of COVID-19 pneumonia. Axial images from contrast-enhanced CT (A–C) and unenhanced CT (D) of the chest, each in different patients, all demonstrating CT imaging findings of bilateral multifocal ground-glass opacities of variable extent similar to the reported imaging features of COVID-19 pneumonia. (A) A 36-year-old female with headache, dry cough, chest pain, myalgias, and low-grade fever. Workup included negative respiratory viral panel, two serial reverse transcriptase–polymerase chain reaction (RT-PCR) tests for COVID-19 that were negative. Bronchoalveolar lavage revealed eosinophilia. The patient improved on steroid treatment in keeping with the diagnosis of acute eosinophilic pneumonia. (B) An 18-year-old male with shortness of breath, cough, fever, and chest pain. Three sequential RT-PCR tests for COVID-19 were negative. Upon further questioning, symptom onset began approximately 24 hours after vaping a tetrahydrocannabinol product. The follow-up CT obtained a month later (not shown) revealed near complete resolution of opacities. The leading consideration for the pulmonary findings for this patient is vaping-related acute lung injury. (C) A 49-year-old female with 4 days of fever, chest pain, cough, and abdominal pain. Viral serology was positive for Influenza A. RT-PCR for COVID-19 was negative. (D) A 62-year-old female with history of invasive ductal breast carcinoma that presented with dyspnea and nonresolving pleuritic cough. Pulmonary biopsy revealed organizing pneumonia clinically favored to be induced by therapy with paclitaxel. COVID-19 = coronavirus disease; CT = computed tomography.
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The role of imaging after diagnosis of COVID-19 pneumonia is evolving with a goal to conserve resources and limit exposure of hospital personnel to potential infection. Sequential imaging may be indicated for management of the disease, particularly for inpatients who are at higher risk of morbidity and mortality, or when a superimposed process or associated complications are suspected. As with diagnosis of COVID-19, portable chest radiography is preferred to minimize the demands on the healthcare system and mitigate exposure to healthcare professionals, again noting that routine imaging in stable patients is not indicated and should be primarily reserved for clinically deteriorating patients (8). As with other viral pneumonias, patients with infection with COVID-19 are at risk for superimposed infections. The presence of imaging findings such as lobar consolidation, centrilobular nodules particularly in a tree-in-bud pattern, or cavitary consolidation should raise the possibility of superinfection (59, 60). Finally, although it is beyond the scope of this review of imaging pulmonary infection with COVID-19, cross-sectional imaging of the abdomen, pelvis, and brain may also be indicated in appropriate clinical context given that COVID-19 can trigger injury to the myocardium, kidneys, gastrointestinal tract, brain, and vasculature resulting in complications such as the increased risk of thromboembolic disease leading to stroke and pulmonary artery embolism (Figure 5) (61–63).
Figure 5. Imaging of complications of COVID-19 pneumonia. Coronal (A) and sagittal (B and C) multiplanar reformatted images from a contrast-enhanced chest computed tomography obtained using a pulmonary artery embolism (PE) protocol in a 71-year-old male with known COVID-19 pneumonia for 1 week, who originally presented with shortness of breath and hypoxia. Images demonstrate subsegmental filling defects in the right-sided pulmonary arteries, compatible with subsegmental PE (white arrows). In addition, ground-glass opacities, denser consolidation, and perilobular consolidation were present in the lungs, in keeping with advanced pneumonia. Axial magnetic resonance imaging of the brain with including diffusion-weighted imaging (D), apparent diffusion coefficient map (E), and fluid-attenuated inversion recovery (F) images in a different patient with COVID-19 pneumonia who returned with left upper extremity weakness a month after hospitalization. Restricted diffusion (images D and E) and parenchymal edema (image F) compatible with acute PCA territory infarction in the right temporal and occipital lobes. COVID-19 = coronavirus disease; PCA = posterior cerebral artery.
[More] [Minimize]As of this writing, it is currently unclear for how long after infection it is useful to obtain imaging in patients known to have COVID-19 pneumonia. However, the pattern and course of pulmonary changes on CT correlate with clinical course and may be useful in management of this disease (64). Also, little is known about the long-term pulmonary consequences of COVID-19 infection, and this will likely be a focus of future research. Given the correlation of imaging findings with clinical severity of disease, imaging will also likely play a role in the assessment of efficacy of future treatment interventions for this disease.
The modest sensitivity and specificity of chest radiography for the detection of COVID-19 pneumonia in patients suspected of infection has led to interest in the development of artificial intelligence models for analyzing chest radiographs and CT. Although this is still in preclinical development, recently published work suggests that this type of approach may be successful and may provide enhanced accuracy in reporting (65), with similar efforts also underway for CT imaging (66). Given the potential mimics of COVID-19 on imaging, one goal of such efforts is to provide support for the interpreting radiologists to enhance accuracy in diagnostic reporting that can be implemented across institutions, levels of diagnostic radiology experience, and community prevalence of COVID-19. The use of advanced imaging modalities in the chest, such as dual-energy CT, has been described and will likely be the focus of future research potentially contributing to the understanding of the pathophysiology of this disease (67).
Imaging plays a central role in the management of patients with known or suspected COVID-19 pneumonia. COVID-19 pneumonia has a suggestive appearance on chest radiograph, chest ultrasound, and CT, and the use of imaging is contingent on the clinical question being asked, prevalence of the virus in the patient population, patient risk factors, and healthcare resources. The specific imaging aspects of COVID-19 pneumonia are only beginning to emerge, and our current understanding is rapidly evolving with increasing medical experience in this pandemic. CT reporting guidelines have been suggested to assist clinical decision-making, although the accuracy and utility of these reporting criteria have yet to be established. A scientifically rigorous assessment of these imaging reporting criteria, and their impact on patient management, lags behind the rapid spread of this pandemic. As in many pulmonary infections, imaging is already a firmly established clinical tool, although its use must be optimized in these times of newly strained medical resources. The increasing knowledge of facets of COVID-19 imaging greatly aids in recognizing and managing COVID-19–related disease and may facilitate our understanding of how COVID-19 differs from other forms of lung injury.
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