OA203] Assessment of radiation exposure in a newly formed nuclear medicine department

Abstract

Purpose In an oncology nuclear medicine department, radioisotopes are not only used for tumor detecting, staging, evaluation of therapy response but also for therapeutic purposes. This study documents the radiation exposure of departmental staff, related to cyclotron operation and service during the production and injection of 18F radiopharmaceuticals for PET/CT examination. In addition, it investigates exposure in a multiple holding tank system used for the storage of 131I waste generated from patients undergoing thyroid therapy, in order to optimize environmental protection procedures. Methods Measurements for the dose rates of neutrons and photons in the room of ABT-BG-75 self-shielded mini-cyclotron were recorded during bombardment for 18F-FDG production using a neutron detector and a scintillation dosimeter. The correlation between the duration of bombardment and required time to reach a dose rate equal to background level was investigated. An electronic dosimeter was used to record staff exposure for 18F production, dispensing, administration and imaging using PET-CT. Finally, the decay rate of 131I waste was measured using a dose rate meter positioned in the decay tank system of the radioactive iodine isolation ward. Results The time required for the cyclotron room to reach background level following completion of bombardment (3 × 50 min each) was approximately 2 h. The dose rate from neutrons was found to be negligible and from photons was less than 7.5 μ Sv/h. Therefore, personnel can safely enter the room during bombardment. The staff mean whole-body dose per 18F-administered patient was 1–2 μ Sv, depending on patient condition. The values obtained from the 131I radioactive waste stored in a delay tank system were comparable with theoretical values. Conclusion This study is useful for optimizing radiation exposure in an oncology nuclear medicine department. It is shown that during 18F production exposure is mostly attributed to photons. The level of the dose permits staff entry into the cyclotron room. Staff responsible for administration received 1–2 μ Sv per 18F-patient, considered to be on the lower end of the acceptable limit for a radiation worker. The study also documents the decay rate of 131I waste over the period which the suggested activity level for release in the environment is reached.