The Impact of COVID-19 Vaccination on Pediatric Patients: Insights from F-18 FDG PET/MRI Imaging on June 14, 2025 ChildCancer COVIDVaccineEffects FDGImaging MedicalImaging NuclearMedicine PediatricCOVIDVaccine PediatricRadiology PETMRI ThymicActivation VaccineLymphadenopathy +