Taranenko Valery, Xu X George
Nuclear Engineering and Engineering Physics Program, Rensselaer Polytechnic Institute, 110 Eighth St, Troy, NY 12180, USA.
Phys Med Biol. 2008 Mar 7;53(5):1425-46. doi: 10.1088/0031-9155/53/5/017. Epub 2008 Feb 19.
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.
保护胎儿免受外部中子照射是一项重要任务。本文报告了使用RPI - P怀孕女性模型和MCNPX代码得出的外部中子束对胎儿和母体器官的一组吸收剂量转换系数。新开发的怀孕女性模型代表每个孕期末期包含胎儿及其大脑和骨骼的成年女性。器官质量经过调整，使其与参考值的匹配度在1%以内。对于3毫米的立方体素大小，这些模型由针对35个器官的1000万至1500万个体素组成。考虑了六种标准配置（前后位、后前位、左后斜位、右后斜位、旋转位和等中心位）以及0.001电子伏特至100吉电子伏特源能量的外部单能中子束。将结果与基于简化解剖模型的先前数据进行了比较。剂量差异取决于源几何形状、能量和孕期：对于整个胎儿，差异从20%到140%不等，对于胎儿大脑，差异高达100%。解剖学差异是器官剂量差异的主要原因。首次研究了孕期母体器官剂量对解剖学变化的依赖性。与三个月模型相比，九个月模型中胎盘的剂量最多增加了220%，而对于相同模型的前后位源，胰腺、小肠和大肠的剂量减少了60%。提供了胎儿和27个母体器官的剂量转换系数表格。
