Re-Evaluation of Patient-Sourced Radiation Doses in PET/CT.

Background: New generation PET/CT devices provide quality images using low radiopharmaceutical activities. Dose monitoring is carried out for nuclear medicine personnel, other health personnel, and companions by determining the radiation dose emitted from low-activity patients to the environment. In particular, it is necessary to revise the working conditions of the personnel according to the radiation dose exposed.

Aim: It was aimed to reevaluate the radiation dose rate transmitted to the environment from patients injected with ¹⁸F-FDG.

Materials and methods: A total of 31 patients (14F, 17M) who underwent ¹⁸F-FDG PET/CT imaging were included. The mean ¹⁸F-FDG activity of 7.26 ± 1.29 mCi was used for injection. After injection, radiation dose rates (mR/h) were measured at distances of 25, 50, 100, 150, and 200cm for 3 different periods from the level of the head, thorax, abdomen, and pelvis by using a GM counter. Additionally, biological samples such as urine and sweat were taken during 3 different periods. The activity amounts (μCi) in the samples were measured with a well-type counter.

Results: Strong correlations were calculated between normalized dose rates obtained by all regions and time. Considering the nuclear medicine staff handling time with a PET/CT patient, the average dose received by staff was calculated between a range of 0.002-0.004 mSv/pt. The radiation dose exposed to the porter and nurse was calculated as 0.049 mSv/pt for the 2^nd hour and 0.001-0.007 mSv/pt for the 4^th hour, respectively. The companion was exposed to a dose between 0.073-0.147 mSv and 0.024-0.048 mSv for public transport and private car transportation after 4-6 hours of injection (for 30-60 min of travel duration), respectively. For inpatients, the received dose for porters, serving 20min from a distance of 30cm for the 2^nd and 4^th hours after the PET/CT scan, was 0.049 mSv/pt and 0.048 mSv/pt, respectively. And for nurses serving from a 50cm distance between 1-5 minutes, these values were found to be 0.001-0.007mSv/pt, 0.001-0.007mSv/pt, and 0.001-0.006mSv/pt, respectively.

Conclusion: The radiation dose of nuclear medicine staff, porters, nurses, and companions are found to be below the recommended dose limit by the ICRP. According to our results, there is no need for any restrictions for patients, companions, or healthcare personnel in PET/CT units.