Evaluating radiation exposure risks from patient urine in a PET-CT center: should concerns arise?

Introduction and ObjectivesFluorine-18 fluorodeoxyglucose (18F-FDG) is used to stage various malignancies, with approximately 30% of non-metabolized 18F-FDG being excreted through urine. Patients are advised to drink 500 mL–1 L of water to increase urine production so that they can empty their bladder whilst still at the facility to reduce the radiation dose to the bladder wall; this makes their urine radioactive. This study aims to assess the radiation dose rates from a toilet at a positron emission tomography/computed tomography (PET/CT) center.MethodsRadiation dose measurements were conducted using a portable digital rate meter (6150AD-6 Automess) with a measuring range of 1 µSv/h to 10 mSv/h (energy range 60 keV to 1.2 MeV). The measurements were carried out over a 5-day period. The background radiation was recorded between 8:00–8:30 am. Dose rate measurements were taken daily at 9 am at several places in the toilet: on the seat, on the cistern lid, and approximately 1 m to the left and right of the chamber. Additional daily measurements carried out at 10 am, 11 am, and 12 pm. The annual cumulative dose was estimated based on a five-day working week for 42 working weeks, 8 hours per day.ResultsThe measured weekly dose rate from the toilet was 14.40 ± 0.020 µSv/h. The approximate annual dose over 42 working weeks was 0.63 ± 0.001 mSv/year.ConclusionsThe estimated annual radiation dose from the toilet (0.63 mSv/year) is well below the recommended dose limits for members of the public (1 mSv/year) and radiation workers (20 mSv/year) by the International Commission on Radiological Protection (ICRP). Therefore, there is no significant concern regarding an exposure from patient urine in this setting.