ICRP pregnant-female mesh-type reference computational phantoms part 2: development of maternal phantoms

Abstract

Objective. In the present study, the pregnant-female mesh-type reference computational phantoms (MRCPs) of the International Commission on Radiological Protection (ICRP) were fully developed in the tetrahedral-mesh format by constructing the maternal phantoms for 8-, 10-, 15-, 20-, 25-, 30-, 35-, and 38 week fetal ages. Approach. The reference blood-inclusive organ dataset (masses, elemental compositions, and densities) and the anthropometric data (rib cage dimensions, spinal curvature and pelvic inclination angle, breast dimensions, and anthropometric parameters) were established, which were then used to develop the maternal phantoms. During the development process, the pregnant-female MRCPs were fully developed by installing the mesh-type fetal phantoms in the maternal uterus considering the shape and position of the fetus. Main results. The dosimetric impact of the phantoms, in terms of fetal dose from maternal radionuclide intake, was investigated by calculating the photon specific absorbed fractions (SAFs) for some selected maternal organs as source regions and the entire fetal phantom as a target region. The results showed that the SAFs for the older fetus were larger than those for the younger fetus when the source-target distance is long, and the opposite trend is observed when the distance is short. These results were observed due to the growth of the fetus. Significance. The pregnant-female MRCPs will serve as the only ICRP reference phantoms representing the pregnant women and fetuses. The comprehensive SAFs dataset will be computed to calculate the ICRP reference dose coefficients for fetal members of the public.