Effect of patient bladder voiding on radiation dose rates measured around patients undergoing PET/CT imaging using 18F-FDG

Accurate dose rate estimates is important for radiation protection specialists conducting risk assessments and performing dose reconstruction in cases of accidental exposures. Objectives: The objectives of this work was to experimentally evaluate the bladder voiding factor effect on the dose rate measured from patients undergoing PET/CT imaging studies using 18F-FDG by directly measuring the dose rate immediately before and after voiding, and compare the results with the current scientific literature. Results: The bladder voiding effect had a dose rate reduction factor of about 12% between dose rates measured before and after voiding. This measured reduction factor agreed with the 15% reported by the AAPM Task Group 108. We have also measured dose rates at one meter from 50 patients and found an average dose rate per unit activity of 93.7 μSv/hr/GBq. Our dose rate results were in excellent agreement with the results of current published data (92 μSv/hr/GBq, AAPM Task Group 108). Conclusions: The presented data can be applied in radiation protection optimization procedures, especially for the protection of the care givers from patients undergoing 18F-FDG PET/CT imaging when they are considered as external radiation source or hazard to others. The provided information will benefit medical physicist working in nuclear medicine and radiation safety policy makers.