Implication of ICRP pediatric reference voxel phantoms on dose assessment of patients in radioiodine therapy

To investigate the impact of the recently released pediatric reference voxel phantoms (0-, 1-, 5-, 10-, 15-year-old males and females) of the International Commission on Radiological Protection (ICRP) on organ dose estimates for radioactive iodine (RAI) treatment in pediatric patients, we calculated and analyzed pediatric-specific iodine-131 S values (rT ← thyroid) for the 30 radiosensitive organs by conducting Monte Carlo simulations using the Geant4. The gender dependency in the S values was frequently seen for the 15-year-old phantoms with higher S values of female than male. In addition, the age dependency in the S values was observed for most target organs; that is, the S values tend to decrease for older ages (e.g., ∼120 times for the gonads between the adult and newborn) due mainly to the inter-organ distances generally longer for older ages. Moreover, we observed that the iodine-131 S values tend to be significantly greater by up to ∼145.5 times than those of the stylized phantoms that have been widely used for organ dose estimates of pediatric RAI patients. We believe that the pediatric-specific iodine-131 S values (rT ← thyroid) of the ICRP pediatric reference voxel phantoms should be beneficial to improve the dosimetry of pediatric RAI patients.