Patient-specific radiation dose for Chinese pediatric patients undergoing whole-body PET/CT examinations

Abstract

Purpose: 
To assess potential variations in the absorbed dose between Chinese and Caucasian children exposed to 18F-FDG PET scan and to investigate the factors contributing to dose differences, this work employed patient-specific phantoms and our compartment model for calculating the patient-specific absorbed dose in Chinese children. 
Methods: Data of 29 Chinese pediatric patients undergoing whole-body 18F-FDG PET/CT studies were retrospectively collected, including PET images for activity distributions and corresponding CT images for organ segmentation and phantom construction. A biokinetic compartment model was implemented to obtain cumulated activities. Absorbed radiation dose for both CT and PET component were calculated using Monte Carlo simulations. Regression models were fitted to time integrated activity coefficient (TIAC) and organ absorbed dose for each patient.
Results: TIACs of all the organs in compartment model and the organ dose for 12 organs were correlated with patients’ weight. Young children have significantly large uptake in brain compared to adults. The distinctions of anatomical and biological characteristics between Chinese and Caucasian children contribute to variations in the absorbed dose of 18F-FDG PET scans. PET contributed more in organ dose than CT did in most organs, especially in brain and bladder. The average effective dose (± SD) was 4.48 mSv (± 1.12 mSv), 7.04 mSv (± 2.49 mSv) and 11.52 mSv (± 3.20 mSv) from CT, PET and their sum respectively. PET contributed 1.57 times higher than CT.
Conclusions: 
To the best of our knowledge, this work represents the first attempt to estimate patient-specific radiation doses from PET/CT for Chinese pediatric patients. TIACs derived from our methodology in both age groups exhibited significant differences from the that reported in ICRP 128. Our methodology offers valuable approach not only for estimating pharmacokinetic characteristics and patient-specific doses in pediatric patients undergoing 18F-FDG studies but also for other cohorts with similar characteristics.