Effective dose to staff members in a positron emission tomography/CT facility using zirconium-89.
OBJECTIVE
Positron emission tomography (PET) using zirconium-89 ((89)Zr) is complicated by its complex decay scheme. In this study, we quantified the effective dose from (89)Zr and compared it with fluorine-18 fludeoxyglucose ((18)F-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 (89)Zr and those emissions from (18)F-FDG were modelled in the simulations but low-energy characteristic X-rays were ignored.


RESULTS
On the basis of injected activity, the dose from (89)Zr was higher than that of (18)F-FDG. However, the dose per scan from (89)Zr became less than that from (18)F-FDG near the patient, owing to the difference in injected activities. In the corridor and control rooms, the (89)Zr dose was much higher than (18)F-FDG, owing to the difference in attenuation by the shielding materials.


CONCLUSIONS
The presence of the high-energy photons from (89)Zr-labelled immuno-PET radiopharmaceuticals causes a significantly higher effective dose than (18)F-FDG to the staff outside the patient room. Conversely, despite the low administered activity of (89)Zr, it gives rise to a comparable or even lower dose than (18)F-FDG to the staff near the patient. This interesting result raises apparently contradictory implications in the radiation protection considerations of a PET/CT facility.


CONCLUSIONS
To the best of our knowledge, radiation exposure to staff and public in the PET/CT unit using (89)Zr has not been investigated. The ultimate output of this study will lead to the optimal design of the facility for routine use of (89)Zr.
Department of Radiological Sciences, King Saud University, Riyadh, Saudi Arabia. kalzimami@ksu.edu.sa
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D005160:Facility Design and Construction; D019788:Fluorodeoxyglucose F18; D006801:Humans; D009010:Monte Carlo Method; D016273:Occupational Exposure; D019047:Phantoms, Imaging; D017785:Photons; D049268:Positron-Emission Tomography / Q000379:methods*; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000379:methods*; D011835:Radiation Protection; D011868:Radioisotopes; D011872:Radiology Department, Hospital; D019275:Radiopharmaceuticals; D014055:Tomography, Emission-Computed / Q000379:methods; D015040:Zirconium
D011868:Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D015040:Zirconium