Dewji Shaheen, Reed K Lisa, Hiller Mauritius
Center for Radiation Protection Knowledge, Environmental Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN, 37831-6335, USA.
Nuclear and Radiological Engineering Program, Georgia Institute of Technology, 770 State Street, Atlanta, GA, 30332-0745, USA.
Radiat Environ Biophys. 2017 Aug;56(3):277-291. doi: 10.1007/s00411-017-0698-1. Epub 2017 Jun 22.
Computational phantoms with articulated arms and legs have been constructed to enable the estimation of radiation dose in different postures. Through a graphical user interface, the Phantom wIth Moving Arms and Legs (PIMAL) version 4.1.0 software can be employed to articulate the posture of a phantom and generate a corresponding input deck for the Monte Carlo N-Particle (MCNP) radiation transport code. In this work, photon fluence-to-dose coefficients were computed using PIMAL to compare organ and effective doses for a stylized phantom in the standard upright position with those for phantoms in realistic work postures. The articulated phantoms represent working positions including fully and half bent torsos with extended arms for both the male and female reference adults. Dose coefficients are compared for both the upright and bent positions across monoenergetic photon energies: 0.05, 0.1, 0.5, 1.0, and 5.0 MeV. Additionally, the organ doses are compared across the International Commission on Radiological Protection's standard external radiation exposure geometries: antero-posterior, postero-anterior, left and right lateral, and isotropic (AP, PA, LLAT, RLAT, and ISO). For the AP and PA irradiation geometries, differences in organ doses compared to the upright phantom become more profound with increasing bending angles and have doses largely overestimated for all organs except the brain in AP and bladder in PA. In LLAT and RLAT irradiation geometries, energy deposition for organs is more likely to be underestimated compared to the upright phantom, with no overall change despite increased bending angle. The ISO source geometry did not cause a significant difference in absorbed organ dose between the different phantoms, regardless of position. Organ and effective fluence-to-dose coefficients are tabulated. In the AP geometry, the effective dose at the 45° bent position is overestimated compared to the upright phantom below 1 MeV by as much as 27% and 82% in the 90° position. The effective dose in the 45° bent position was comparable to that in the 90° bent position for the LLAT and RLAT irradiation geometries. However, the upright phantom underestimates the effective dose to PIMAL in the LLAT and RLAT geometries by as much as 30% at 50 keV.
已经构建了带有可活动手臂和腿部的计算体模，以估计不同姿势下的辐射剂量。通过图形用户界面，可以使用“带移动手臂和腿部的体模（PIMAL）”4.1.0版软件来调整体模的姿势，并为蒙特卡罗N粒子（MCNP）辐射传输代码生成相应的输入文件。在这项工作中，使用PIMAL计算光子注量到剂量系数，以比较标准直立姿势下的简化体模与实际工作姿势下体模的器官剂量和有效剂量。这些可活动体模代表了包括男性和女性参考成人的完全弯曲和半弯曲躯干且手臂伸展的工作姿势。比较了单能光子能量为0.05、0.1、0.5、1.0和5.0 MeV时直立和弯曲位置的剂量系数。此外，还比较了国际放射防护委员会标准外照射几何条件下的器官剂量：前后、后前、左右侧和各向同性（AP、PA、LLAT、RLAT和ISO）。对于AP和PA照射几何条件，与直立体模相比，器官剂量差异随着弯曲角度的增加而变得更加显著，并且除了AP中的脑和PA中的膀胱外，所有器官的剂量大多被高估。在LLAT和RLAT照射几何条件下，与直立体模相比，器官的能量沉积更可能被低估，尽管弯曲角度增加，但总体没有变化。无论位置如何，ISO源几何条件在不同体模之间的吸收器官剂量上没有引起显著差异。列出了器官和有效注量到剂量系数。在AP几何条件下，低于1 MeV时，45°弯曲位置的有效剂量与直立体模相比被高估，在90°位置高估多达27%和82%。对于LLAT和RLAT照射几何条件，45°弯曲位置的有效剂量与90°弯曲位置的有效剂量相当。然而，在50 keV时，直立体模在LLAT和RLAT几何条件下低估了对PIMAL的有效剂量多达30%。
