Introduction
Coronavirus disease 2019 (COVID-19), a highly infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was firstly reported in Wuhan, Hubei Province, China, and rapidly spreads to other domestic cities and countries beyond China [1]. On January 30, 2020, the World Health Organization (WHO) declared this ongoing outbreak as a global public health emergency and raised the risk of COVID-19 to very high at the global level on February 28, 2020 [2]. A total of 88,948 COVID-19 cases with 3043 deaths were confirmed as of March 2, 2020, of which 80,174 were from China and 8774 were from other 64 countries [3]. In COVID-19 diagnosis, real-time reverse transcription polymerase chain reaction (RT-PCR) of viral nucleic acid is regarded as the reference standard; however, recent studies addressed the importance of chest computed tomography (CT) examination in COVID-19 patients with false negative RT-PCR results [4, 5], and reported the CT sensitivity as 98% [6]. Additionally, according to the official diagnosis and treatment protocol (6th edition) declared by the National Health Commission of China [7], CT examination is of great significance not only in diagnosing COVID-19 but also in monitoring disease progression and evaluating therapeutic efficacy.
Bilateral distribution of ground glass opacities (GGO) with or without consolidation in posterior and peripheral lungs was the cardinal hallmark of COVID-19 [8, 9]. However, with further analysis of increasing cases, a diversity of interesting CT imaging features were found, including crazy paving pattern, airway changes, reversed halo sign etc. [10–12], which may shed light on the possible mechanism of lung injury in COVID-19. A recent editorial by Kay et al [13] also encouraged researchers to focus the many faces of COVID-19 for its better recognition and accurate diagnosis.
Therefore, with a comprehensive review of published studies and the experience of COVID-19 imaging interpretation in frontline, we aim to review the typical and relatively atypical CT manifestations of COVID-19 in a pictorial fashion and help radiologists to familiarize these possible imaging features of COVID-19.