Quantification of radiation exposure to patients and surrounding people after oncologic PET/CT imaging with ¹⁸F-FDG

Objectives Integrated PET/CT imaging with ¹⁸F-FDG has been frequently used in cancer patients and its inevitable radiation exposure to patients has been considered acceptable based on high benefit-cost ratio. Recently, radiation exposure and its protection have been refocused since the Fukushima nuclear disaster in Japan, 2011. In the current study, we estimated radiation dose to patients and surrounding people including caregivers and health care providers after ¹⁸F-FDG PET/CT imaging for reassurance of radiation safety and optimized PET/CT imaging protocol.

Methods 78 patients diagnosed with various cancers underwent whole-body PET/CT (Discovery 600, GE) imaging after injection of ¹⁸F-FDG. Effective radiation dose to patients was calculated by using injected dose of ¹⁸F-FDG and dose-length product (DLP) displayed on the CT radiation report. External radiation dose from the patients was measured by 4 Landauer OSLN dosimeters placed in a line 1 m away from the longitudinal axis of patients (neck, chest, abdomen, and proximal thigh) for about 60 min while patients had a rest prior to PET/CT imaging. Whole-body radiation dose rate was calculated according to the revised Inlight OSLN whole body dose algorithm (2008).

Results All patients underwent PET scan about 60 min after injection of 333 ± 25.9MBq (9.0 ± 0.7 mCi) of ¹⁸F-FDG and helical CT scan (tube voltage = 120 kVp, tube current = auto, noise index = 18). Estimated effective radiation doses (mSv) from PET and CT were 6.4 ± 0.5 and 8.8 ± 2.5, respectively. Estimated whole-body radiation dose rates (μSv/min) at 1 m away from the patients (neck, chest, abdomen, and proximal thigh) were 0.34, 0.36, 0.35, and 0.30, respectively.

Conclusions Internal and external radiation doses after ¹⁸F-FDG PET/CT imaging were quantitatively evaluated. To minimize radiation exposure to caregivers and health care providers as well as patients, further studies would be required on optimized protocol of PET/CT imaging and behavioral guidelines.