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Updated: Jun 25, 2025
Whole-body PET/MRI of Pediatric Patients: The Details That Matter
Published on: December 19, 2017
Patient-specific radiation dose for Chinese pediatric patients undergoing whole-body PET/CT examinations
Haoran Jia1, Mengjia Xue1, Xianru Li2
1Institute of Radiation Medicine, Fudan University, 2094 Xietu Road, Shanghai 200032, People's Republic of China.
Insights
This study reveals significant differences in radiation absorbed doses from 18F-FDG PET scans between Chinese and Caucasian children. Patient-specific models highlight anatomical and biological variations impacting effective dose calculations.
Area of Science:
- Nuclear Medicine
- Medical Physics
- Radiology
Background:
- Estimating radiation absorbed dose in pediatric patients undergoing 18F-FDG PET/CT is crucial due to anatomical and physiological differences from adults.
- Existing dosimetry models, often based on Caucasian data (e.g., ICRP 128), may not accurately reflect absorbed doses in diverse pediatric populations like Chinese children.
Purpose of the Study:
- To determine patient-specific absorbed radiation doses from 18F-FDG PET/CT in Chinese pediatric patients.
- To compare these doses with those of Caucasian children and identify factors contributing to observed differences.
- To evaluate the impact of anatomical and pharmacokinetic variations on radiation dosimetry in pediatric populations.
Main Methods:
- Retrospective analysis of 29 Chinese pediatric patients undergoing 18F-FDG PET/CT.
- Construction of patient-specific phantoms using CT and PET imaging for organ segmentation.
- Application of a biokinetic compartment model to calculate cumulated activities and Monte Carlo simulations for absorbed dose estimation.
- Regression analysis to correlate time-integrated activity coefficients (TIACs) and organ doses with patient characteristics.
Main Results:
- Time-integrated activity coefficients and organ doses (for 12 organs) correlated with patient weight.
- Younger children exhibited higher 18F-FDG uptake in the brain compared to adults.
- Significant differences in absorbed and effective doses were observed between Chinese and Caucasian children, attributed to distinct anatomical and pharmacokinetic profiles.
- PET contributed more to the organ dose than CT, particularly in the brain and bladder. Average effective dose from PET was 7.8 mSv, compared to 4.5 mSv from CT.
Conclusions:
- This study provides the first patient-specific radiation dose estimations for Chinese pediatric patients undergoing 18F-FDG PET/CT.
- Significant discrepancies exist in TIACs and absorbed doses compared to established models (ICRP 128), highlighting the need for population-specific dosimetry.
- Racial and age-related differences in anatomy and pharmacokinetics necessitate tailored dosimetry approaches, as adult data applied to children introduces considerable uncertainty.
Abstract:
Objective.To assess potential variations in the absorbed dose between Chinese and Caucasian children exposed to18F-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.Approach.Data of 29 Chinese pediatric patients undergoing whole-body18F-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.Main results.TIACs of all the organs in our 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 of18F-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 4.5 mSv (± 1.12 mSv), 7.8 mSv (± 3.2 mSv) and 12.3 mSv (± 3.5 mSv) from CT, PET and their sum respectively. PET contributed 1.7 times higher than CT.Significance.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. Substantial differences in absorbed and effective doses were observed between Chinese and Caucasian children across all age groups. These disparities are attributed to markedly distinct anatomical and pharmacokinetic characteristics among adults and pediatric patients, and different racial groups. The application of data derived from adults to pediatric patients introduces considerable uncertainty. Our methodology offers a valuable approach not only for estimating pharmacokinetic characteristics and patient-specific radiation doses in pediatric patients undergoing18F-FDG studies but also for other cohorts with similar characteristics.
