Estimation of Effective Dose Received by Caregivers During [¹⁸F]FDG PET/CT Studies

Caregivers who assist patients during [¹⁸F]FDG PET/CT are exposed to ionizing radiation, particularly when close physical support is required. Limited real-world data are available about the actual doses received by caregivers during routine clinical practice. This study aimed to estimate effective doses received by caregivers and determine whether exposures remained below the 1-mSv dose constraint recommended by the Australian Radiation Protection and Nuclear Safety Agency for caregivers during diagnostic procedures, consistent with International Commission on Radiological Protection recommendations. Methods: This prospective observational study included caregivers accompanying patients undergoing [¹⁸F]FDG PET/CT. Each caregiver wore a calibrated electronic pocket dosimeter that measured the personal dose equivalent in soft tissue at a depth of 10 mm below the point where the dosimeter is worn (H_p(10)), clipped to the mid-chest throughout the uptake period and during imaging. Patients received weight-based [¹⁸F]FDG activity (3.7-5.2 MBq/kg) and remained in individual uptake cubicles to minimize exposure from other injected patients. Caregiver-patient distance, measurement time, and H_p(10) were recorded. Correlations were evaluated using the Spearman rank correlation coefficient. Group comparisons were analyzed using the Kruskal-Wallis test with a Dunn post hoc analysis, and dose predictors were assessed using a generalized linear model with a γ-distribution. Results: Thirty-nine caregiver-patient pairs were included, with complete dosimetry data available for all participants. Caregivers received measurable but low H_p(10) values, although exposure varied widely on the basis of proximity and measurement time. The median caregiver dose was 0.12 mSv (interquartile range, 0.04-0.54 mSv). A strong positive correlation was observed between H_p(10) and time spent with the patient (Spearman ρ = 0.617), whereas a strong inverse correlation was observed between H_p(10) and caregiver-patient distance (Spearman ρ = -0.914). Caregivers positioned closest to patients, particularly those assisting pediatric patients, received the highest doses. Group comparisons by distance category demonstrated significant differences in exposure. Multivariate modeling confirmed that time, distance, and patient age independently contributed to caregiver dose. Conclusion: Caregiver radiation exposure during patient [¹⁸F]FDG PET/CT was low and remained within acceptable limits (<1 mSv) but varied considerably with caregiver-patient proximity and the time spent with the patient. These findings confirm that caregiver radiation exposure is strongly influenced by the time spent with the patient and the distance maintained, although close physical support is often unavoidable.