Estimation of dose to a bystander from F-18 FDG patients using Monte Carlo simulation in clinical exposure scenarios

The radiation exposure to bystanders from nuclear medicine patients is a common concern raised in nuclear medicine departments. The GATE (Geant4 Application for Tomographic Emission) Monte Carlo radiation transport application was used to estimate the dose to a bystander. Two voxelised phantoms were utilised in a GATE Monte Carlo simulation as the radiation source and target. The absorbed dose to the target phantom from radiation emitted by the source phantom was calculated. Three experimental setups of increasing complexity, with the last one replicating clinical dose rate measurements, were used to validate the simulation results. Four clinical scenarios were simulated to estimate the dose to a healthcare worker from F-18 FDG patients: an ultrasound procedure, two surgical procedures (head and chest), and a face-to-face consultation. The mean absorbed dose to the foetus was also estimated using the same method and pregnant female phantoms as target for ultrasound scan scenario. The effective dose to a healthcare worker from an FDG PET patient who has had 250 MBq of FDG injection 3 h post procedures was estimated as: 18.1 ± 0.1 µSv for 30-minute ultrasound scan, 36.5 ± 0.3 µSv for 1-hour chest surgical procedure, and 9.3 ± 0.1 µSv for 15-minute face to face consultation scenario. This method can be easily extended to estimate the dose to bystanders from nuclear medicine patients injected with various radioisotopes in different clinical scenarios.