The imaging quantification of multiple organs by dynamic ¹⁸F-FDG PET/CT in discharged COVID-19 patients: A...

Purpose: To early identify abnormal lesions by applying the ¹⁸F-FDG PET dynamic modeling approach for discharged patients recovering from COVID-19. Methods: Seven discharged COVID-19 patients (COVID-19 group), twelve healthy volunteers (control group 1), and eight cancer patients with normal pulmonary function (control group 2) were prospectively enrolled. Control group 1 completed static ¹⁸F-FDG PET/CT only; COVID-19 group and control group 2 completed 60-min dynamic ¹⁸F-FDG PET/CT. Among COVID-19 group and control group 2, the uptake of FDG on the last frame (at 55-60 min) of dynamic scans was used for static analysis. Prior to performing scans, COVID-19 patients provided negative real-time Reverse Transcription-Polymerase Chain Reaction (rRT-PCR) of SARS-CoV-2, normal lung functions test, and normal laboratory test. Organ-to-liver standard uptake ratio (OLR, i.e. SUV_max ^{evaluated organ}/ SUV_max ^liver) from conventional static data and Patlak analysis based on the dynamic modeling to calculate the ¹⁸F-FDG net uptake rate constant (K_i) were performed. Results: Compared to the control groups, COVID-19 patients at two to three months after discharge still maintained significantly higher K_i values in multiple organs (including lung, bone marrow, lymph nodes, myocardium and liver), although results for regular OLR measurements were normal for all discharged COVID-19 patients. Taking the image of lung as an example, the differences of SUV_max images between COVID-19 group and control group were hard to distinguish. In contrast, a high ¹⁸F-FDG signal of the lung among the COVID-19 group was observed for K_i images. Conclusion: The K_i from ¹⁸F-FDG PET/CT dynamic imaging quantification might contribute to identifying residual lesions for COVID-19 survivors. Trial registration: The trial is registered with ClinicalTrials.gov, number NCT04519255 (IRB-approved number, K52-1).