Department of Physics, Texas A&M University, College Station, TX 77843.
Department of Nuclear Engineering, Texas A&M University, College Station, TX 77843.
Health Phys. 2021 May 1;120(5):559-572. doi: 10.1097/HP.0000000000001382.
Radiation dose estimations in the human body are performed using computational reference phantoms, which are anatomical representations of the human body. In previous studies, dose reconstructions have been performed focusing primarily on phantoms in an upright posture, which limits the accuracy of the dose estimations for postures observed in realistic work settings. In this work, the International Commission on Radiological Protection (ICRP) Publication 103 recommendations for monoenergetic neutron plane sources directed downward from above the head (cranial) and upward from below the feet (caudal) for adult female and male reference phantoms were used to calculate organ absorbed and effective dose coefficients. The Phantom with Moving Arms and Legs (PIMAL) and the Monte Carlo N-Particle (MCNP) radiation transport code were used to compute organ-absorbed dose and effective dose coefficients for the upright, half-bent (45°), and full-bent (90°) phantom postures. The doses calculated for each of the articulated positions were compared to those calculated for the upright posture by computing the ratios of the coefficients (45°/upright and 90°/upright). These ratios were used to assess the effectiveness of upright phantoms in providing a comparable estimate when conducting dose estimations and dose reconstructions for articulated positions. This work compiling neutron cranial and caudal posture-specific dose coefficients completes the series of dose coefficients computed for posture-specific ICRP Publication 116 irradiation geometries for monoenergetic photons and neutrons, in addition to cranial and caudal monoenergetic photons. Results reported demonstrated that organ-absorbed dose coefficients for most of the organs in the CRA and CAU irradiation geometries were significantly higher for the bent phantoms than for the upright phantom. Since the upright phantom underestimates the organ-absorbed dose, this demonstrates the impact of posture while performing dose calculations. Organ doses reported in past neutron dose coefficient data were found to omit effects from neutron resonances at energies of 0.435, 1.0, and 3.21 MeV from 16O in tissue. Reported data notes as high as 60% underestimation for neutron organ-absorbed doses, specifically at the neutron resonance energy region omitted by smoothing. Ongoing studies are examining the effect of resonances on reported neutron organ-absorbed dose coefficients in ICRP 116 geometries.
人体辐射剂量估算采用计算参考体模进行，这些体模是人体解剖结构的代表。在之前的研究中，剂量重建主要集中在直立姿势的体模上，这限制了对实际工作环境中观察到的姿势的剂量估算的准确性。在这项工作中，使用了国际辐射防护委员会（ICRP）出版物 103 中关于来自头顶上方（颅侧）和脚下方（尾侧）的单能中子平面源的推荐值，对成年女性和男性参考体模进行计算，以得出器官吸收剂量和有效剂量系数。使用 Phantom with Moving Arms and Legs（PIMAL）和 Monte Carlo N-Particle（MCNP）辐射传输代码，计算了直立、半弯曲（45°）和全弯曲（90°）体模姿势的器官吸收剂量和有效剂量系数。通过计算各关节位置的系数比值（45°/直立和 90°/直立），将计算得到的各关节位置的剂量与直立位置的剂量进行比较。这些比值用于评估在进行关节位置的剂量估算和剂量重建时，直立体模提供可比估计的有效性。这项工作编译了特定于中子颅侧和尾侧姿势的剂量系数，完成了为特定于姿势的 ICRP 出版物 116 辐射几何形状计算的单能光子和中子的特定于姿势的剂量系数系列，此外还有颅侧和尾侧单能光子的剂量系数。报告的结果表明，在 CRA 和 CAU 照射几何形状中，大多数器官的器官吸收剂量系数对于弯曲体模明显高于直立体模。由于直立体模低估了器官吸收剂量，这表明在进行剂量计算时姿势的影响。在过去的中子剂量系数数据中报告的器官剂量被发现忽略了在组织中 16O 的 0.435、1.0 和 3.21 MeV 中子共振的影响。报告的数据注释指出，在平滑忽略的中子共振能区，中子器官吸收剂量的低估高达 60%。正在进行的研究正在检查在 ICRP 116 几何形状中，共振对报告的中子器官吸收剂量系数的影响。
