Department of Radiological Sciences, King Saud University, Riyadh, Saudi Arabia.
Br J Radiol. 2013 Oct;86(1030):20130318. doi: 10.1259/bjr.20130318. Epub 2013 Aug 9.
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).
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.
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.
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.
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.
镥-89（89Zr）正电子发射断层扫描（PET）因其复杂的衰变方案而变得复杂。在这项研究中，我们定量了89Zr 的有效剂量，并将其与氟-18 氟脱氧葡萄糖（18F-FDG）进行了比较。
使用 MCNPX 通过蒙特卡罗模拟计算了利雅得 PET/CT 设施中的有效剂量分布。在模拟中，对正电子韧致辐射、湮没光子、89Zr 的延迟伽马射线以及 18F-FDG 的这些发射进行了建模，但忽略了低能特征 X 射线。
基于注射的活动，89Zr 的剂量高于 18F-FDG。然而，由于注射活动的差异，89Zr 的每扫描剂量在靠近患者时变得低于 18F-FDG。在走廊和控制室，由于屏蔽材料的衰减差异，89Zr 的剂量远高于 18F-FDG。
与 18F-FDG 相比，来自 89Zr 标记免疫 PET 放射性药物的高能光子会导致患者房间外的工作人员受到更高的有效剂量。相反，尽管 89Zr 的给药活性较低，但它会导致靠近患者的工作人员的剂量与 18F-FDG 相当或更低。这个有趣的结果在 PET/CT 设施的辐射防护考虑中提出了明显矛盾的含义。
据我们所知，使用 89Zr 的 PET/CT 单位的工作人员和公众的辐射暴露尚未得到调查。本研究的最终结果将导致该设施的最佳设计，以便常规使用 89Zr。
