Evolution of (18)F-FDG PET/CT Findings in Patients After COVID-19: An Initial Investigation

The aim of this study was to assess the temporal evolution of pulmonary (18)F-FDG uptake in patients with coronavirus disease 2019 (COVID-19) and post–COVID-19 lung disease (PCLD). Methods: Using our hospital’s clinical electronic records, we retrospectively identified 23 acute COVID-19, 18 PCLD, and 9 completely recovered (18)F-FDG PET/CT patients during the 2 peaks of the U.K. pandemic. Pulmonary (18)F-FDG uptake was measured as a lung target-to-background ratio (TBR(lung) = SUV(max)/SUV(min)) and compared with temporal stage. Results: In acute COVID-19, less than 3 wk after infection, TBR(lung) was strongly correlated with time after infection (r(s) = 0.81, P < 0.001) and was significantly higher in the late stage than in the early stage (P = 0.001). In PCLD, TBR(lung) was lower in patients treated with high-dose steroids (P = 0.003) and in asymptomatic patients (P < 0.001). Conclusion: Pulmonary (18)F-FDG uptake in COVID-19 increases with time after infection. In PCLD, pulmonary (18)F-FDG uptake rises despite viral clearance, suggesting ongoing inflammation. There was lower pulmonary (18)F-FDG uptake in PCLD patients treated with steroids.