Background: Recently, CT findings have been widely reported to be associated with the clinical severity of COVID-19. However, few studies have reported the correlation between CT findings and long-term outcomes in patients with COVID-19. Case presentation: Herein, we conducted a 167 day long-term follow-up of CT examination on 11 patients with COVID-19 to evaluate their long-term prognosis, particularly in severe cases. We found that the course of COVID-19 can be divided into four stages according to the characteristics of CT images: 1) early stage (1–4 days), with chest CT showing quasi-circular ground-glass shadows and fine mesh shadows; 2) progressive stage (5–10 days), showing lesion spread through the axial interstitium along the bronchi and gradual diffusion to the whole lung; 3) recovery stage (11–74 days), showing gradual absorption of the fibre cord, ground-glass, and consolidation shadows; and 4) normal stage (74 days later), indicating no serious permanent lung injuries. Conclusions: Our data indicate that chest CT can enable early detection of COVID-19 and determination of the different stages of COVID-19. Furthermore, mild cases tended to have better prognosis, whereas severe cases still showed cord-like fibrosis in the lungs in follow-up at the 167th day after symptom onset.

Background Since December 2019, the COVID-19 infection broke out in many parts of the world with confirmed and death cases rapidly increasing, which posed a great threat to human life and health. Current nucleic acid detection and antibody testing for the SARS-CoV-2 were the main methods for diagnosis of COVID-19, but not so sensitive, with high false negative rate and missed diagnosis rate. Imaging changes of COVID-19 not only precede symptomatic changes, but also have different imaging characteristics in different periods. We conducted 74 days of dynamic chest CT imaging observation on COVID-19 patients in Hebei province, aiming to understand the dynamic characteristics of the chest CT changes of COVID-19, so as to find the source of infection early, take early intervention measures, and judge the prognosis. Methods Chest CT examinations at intervals 1 to 4 days were conducted for 11 patients with a diagnosis of COVID-19. On the 74th day after onset, chest CT was reexamined to analyze the characteristics of chest CT in each stage. Results Of the 11 cases, 1 case was imported from Wuhan, 10 cases were infected for family clustering after close contact with confirmed COVID-19 cases. There were 3 ordinary cases, 3 severe cases and 5 critical cases. Among them, 2 critical cases died for old age and complications of underlying diseases, while 9 cases were cured by April 7, 2020. The changes of chest CT imaging in 1 child appeared prior to the clinical symptoms. 1–4 days after onset of the initial symptom were the early stages: Chest CT was mainly characterized by single lung quasi-circular ground glass shadow and fine mesh shadow. 5–10 days were the progressive stages: The lesion spread along the axial interstitium of the bronchi and gradually diffused to the whole lung, and reach the peak on day 6 to 9, which was characterized by consolidation, paving stone sign, halo sign, reversed halo sign, and even ‘white lung’ for the critical patients. The recovery stages began on day 11 after onset: The fiber cord, ground glass and consolidation shadow were gradually absorbed. After 74 days of follow-up, no serious permanent lung injury was found. Conclusion Chest CT could determine the different stages of COVID-19. Dynamic follow-up chest CT showed a good prognosis of COVID-19 in Hebei Province, China