Accurate estimation of fetal dose from maternal intake of beta-emitting radionuclides (e.g., 131I, 177Lu, 137Cs) is essential for protecting the developing fetus and assessing its radiological risks. This study developed a comprehensive dataset of electron specific absorbed fractions (SAFs) from maternal source regions to detailed fetal target organs using the series of anatomically realistic hybrid pregnant female and fetus phantoms representing eight gestational stages (8-38 weeks). Monte Carlo radiation transport simulations were performed to compute electron SAFs for 70 maternal source regions and 55 fetal target organs across 20 energies (10 keV-10 MeV). The results revealed a strong dependence of fetal SAFs on maternal-fetal geometry, with adjacent maternal organs (e.g., amniotic fluid, urinary bladder wall) producing markedly higher SAFs than distant sources. Organ-specific analyses showed large variability among fetal targets, particularly for electrons, underscoring the need for organ-level rather than total-body dose estimation. Comparisons with previous datasets based on simplified phantoms demonstrated that anatomical realism and gestation-specific modeling substantially influence dose transfer predictions. The electron SAF dataset presented here, developed with high anatomical and energy resolution, provides an essential foundation for improving fetal internal dosimetry and supporting radiological protection decisions in medical, environmental, and emergency exposure scenarios.
Kwon et al. (Tue,) studied this question.