COVID-19: Chest Computed Tomography Imaging Patterns in Assessment of Disease Progression and Severity
Authors: Thammegowda Sachin , Das Sudha Kiran , Ramachandra Raghu , Ramachandraiah Shashikiran , Honnegowda Shashank 
Published: March 2022

Introduction: Chest Computed Tomography (CT) plays an important role in the diagnosis and management of Corona Virus Disease (COVID-19) infection. A better understanding of the chest CT imaging findings in COVID-19 disease may help in accurate diagnosis and staging of the disease. The temporal changes in the chest CT imaging findings follows a specific pattern which helps in identification of disease progression or recovery from the illness. Aim: To evaluate the chest CT imaging findings of COVID-19 patients during the course of disease. Materials and Methods: This was a retrospective observational study in which 110 hospitalised patients with COVID-19 disease were evaluated for chest CT imaging findings and severity of the infection. Chest CT findings with respect to duration of symptoms onset were divided into early phase disease (<5 days of symptom onset), intermediate phase (5-12 days) and late phase disease (>12 days of symptom onset). Based on visual assessment, CT severity score was given depending on the percentage of each lobe involved in bilateral lung parenchyma. Descriptive statistics were expressed using percentage, range, means and Standard Deviation (mean±SD). Results: A total of 110 COVID-19 positive patients (79 males and 31 females) with mean age of 48.33±9.18 years (range between 22-84 years) were included in the study. CT chest was performed during the different time periods of hospital stay ranging from 2 to 16 days. Early phase disease constituted 53 (48.18%) patients, 21 (19.09%) patients in the intermediate phase and 36 (32.72%) patients were in the late phase. Nineteen (17.27%) patients in the early phase disease (<5 days) had a normal scan. Out of 91 chest CT positive patients, 13 patients (14.28%) were asymptomatic and 78 patients were symptomatic (85.71%). Among the CT positive patients, early phase disease constituted 34 (37.36%) patients, 21 (23.07%) patients were in the intermediate phase and 36 (39.56%) patients in the late phase disease. Early phase disease was predominantly characterised by Ground Glass Opacities (GGOs) which were seen in 27 patients (79.41%), gradual conversion of these GGOs into consolidations during the intermediate phase. Consolidations with fibrotic bands were predominant imaging patterns during the late phase disease seen in 21 patients (58.33%). Mean CT severity score during the early, intermediate and late phase diseases were 4.14±2.12, 14.71±4.80 and 11.08±4.68, respectively. Along with few existing signs described in COVID-19 disease, two signs during the late phase disease were observed such as target sign in 5 patients (13.88%) and centipede sign in 13 patients (36.11%). Splenomegaly was an additional extrapulmonary finding seen in 27 patients (24.5%) which has not been described previously. Conclusion: Specific imaging patterns during the course of COVID- 19 illness provide an information regarding the stage of the illness and disease severity. Ideal timing of chest CT is found to be during the intermediate phase of disease (5-12 days of symptom onset), since most of the lesions evolve in this period and provide accurate disease severity which in turn helps in treatment planning.