Background: PET CT exams frequently use 18F fluorodeoxyglucose (FDG); however, the positron-emitting florin produces a comparatively high amount of gamma radiation (511 keV), which raises concerns for both public and occupational safety. The aim of this study was to measure the external radiation dose rate from patients injected with F-18 fluorodeoxyglucose (FDG) and to determine proper, non-invasive, simple methods to reduce the external radiation dose after the F-18 FDG positron emission tomography/computed tomography (PET/CT) procedure.
Patients and Methods: Our present study included 60 (M/F = 27/33) patients who were referred to nuclear medicine department for F-18 FDG PET/CT imaging. Patients were injected 7.5±1.8 mCi (range: 5.7-9.3 mCi). The study patients were divided into two groups: one group not receiving any water and second group B receiving 1000 ml of water. Dose rates were measured to both groups at a distance of 1m using a Geiger-Müller probe at 4 different time points: 1) Just after the PET/CT imaging pre-voiding, 2) post-voiding and 3) after 30 min 4) after 60 min later just before discharge of patients from PET/CT department. Statistical analysis was performed to evaluate the differences between measurements
Results: Radiation dose rate measurements taken at a distance of 1 meter were to the group 1(without hydration) 28± 7 µSv/h just after the scan pre-voiding, 24± 7 µSv/h post voiding, 21± 7 µSv/h after 30 min and 19±7µSv/h after 60 min later. Group 2 (with hydration) 30 ±8 µSv/h just after the scan pre-voiding,25± 8 µSv/h post voiding,18± 6µSv/h after 30 min and,14± 5 µSv/h after 60 min later. Conclusion: waiting 60 minutes after a PET scan significantly reduced the external radiation dose in all patients undergoing PET scan. Further reductions in the rate of radiation exposure after hydration in second group of patients.