Abstract
Objective: Positron emission tomography (PET) using zirconium-89 (Zr-89) is complicated by its complex decay scheme. In this study, we quantified the effective dose from Zr-89 and compared it with fluorine-18 fludeoxyglucose (F-18-FDG).
Methods: Effective dose distribution in a PET/CT facility in Riyadh was calculated by Monte Carlo simulations using MCNPX. The positron bremsstrahlung, the annihilation photons, the delayed gammas from Zr-89 and those emissions from F-18-FDG were modelled in the simulations but low-energy characteristic X-rays were ignored.
Results: On the basis of injected activity, the dose from Zr-89 was higher than that of F-18-FDG. However, the dose per scan from Zr-89 became less than that from F-18-FDG near the patient, owing to the difference in injected activities. In the corridor and control rooms, the Zr-89 dose was much higher than F-18-FDG, owing to the difference in attenuation by the shielding materials.
Conclusion: The presence of the high-energy photons from Zr-89-labelled immuno-PET radiopharmaceuticals causes a significantly higher effective dose than F-18-FDG to the staff outside the patient room. Conversely, despite the low administered activity of Zr-89, it gives rise to a comparable or even lower dose than F-18-FDG to the staff near the patient. This interesting result raises apparently contradictory implications in the radiation protection considerations of a PET/CT facility.
Advances in knowledge: To the best of our knowledge, radiation exposure to staff and public in the PET/CT unit using Zr-89 has not been investigated. The ultimate output of this study will lead to the optimal design of the facility for routine use of Zr-89.