title: Fluence-to-absorbed-dose conversion coefficients for neutron beams from 0.001 eV to 100 GeV calculated for a set of pregnant female and fetus models.
abstract: Protection of fetuses against external neutron exposure is an important task. This paper reports a set of absorbed dose conversion coefficients for fetal and maternal organs for external neutron beams using the RPI-P pregnant female models and the MCNPX code. The newly developed pregnant female models represent an adult female with a fetus including its brain and skeleton at the end of each trimester. The organ masses were adjusted to match the reference values within 1%. For the 3 mm cubic voxel size, the models consist of 10-15 million voxels for 35 organs. External monoenergetic neutron beams of six standard configurations (AP, PA, LLAT, RLAT, ROT and ISO) and source energies 0.001 eV-100 GeV were considered. The results are compared with previous data that are based on simplified anatomical models. The differences in dose depend on source geometry, energy and gestation periods: from 20% up to 140% for the whole fetus, and up to 100% for the fetal brain. Anatomical differences are primarily responsible for the discrepancies in the organ doses. For the first time, the dependence of mother organ doses upon anatomical changes during pregnancy was studied. A maximum of 220% increase in dose was observed for the placenta in the nine months model compared to three months, whereas dose to the pancreas, small and large intestines decreases by 60% for the AP source for the same models. Tabulated dose conversion coefficients for the fetus and 27 maternal organs are provided.
authors.affiliation: Nuclear Engineering and Engineering Physics Program, Rensselaer Polytechnic Institute, 110 Eighth St, Troy, NY 12180, USA.
authors.forename: Valery
authors.initials: V
authors.lastname: Taranenko
authors.forename: X George
authors.initials: XG
authors.lastname: Xu
mesh_terms: D000328:Adult; D005260:Female; D005333:Fetus / Q000528:radiation effects*; D006801:Humans; D018811:Maternal Exposure; D008954:Models, Biological; D009502:Neutrons; D011247:Pregnancy; D011829:Radiation Dosage; D011835:Radiation Protection