University of Wisconsin-Madison, Department of Medical Physics 1111 Highland Ave Rm 1005, Madison, WI 53705-2275, United States of America.
National Cancer Institute, Radiation Epidemiology Branch, 9609 Medical Center Drive MSC 9776, Bethesda, MD 20892-2590, United States of America.
Phys Med Biol. 2023 Mar 2;68(5). doi: 10.1088/1361-6560/acbbb6.
Dosimetric calculations, whether for radiation protection or nuclear medicine applications, are greatly influenced by the use of computational models of humans, called anthropomorphic phantoms. As anatomical models of phantoms have evolved and expanded, thus has the need for quantifying differences among each of these representations that yield variations in organ dose coefficients, whether from external radiation sources or internal emitters. This work represents an extension of previous efforts to quantify the differences in organ positioning within the body between a stylized and voxel phantom series. Where prior work focused on the organ depth distribution vis-à-vis the surface of the phantom models, the work described here quantifies the intra-organ and inter-organ distributions through calculation of the mean chord lengths. The revised Oak Ridge National Laboratory stylized phantom series and the University of Florida/National Cancer Institute voxel phantom series including a newborn, 1-, 5-, 10- and 15 year old, and adult phantoms were compared. Organ distances in the stylized phantoms were computed using a ray-tracing technique available through Monte Carlo radiation transport simulations in MCNP6. Organ distances in the voxel phantom were found using phantom matrix manipulation. Quantification of differences in organ chord lengths between the phantom series displayed that the organs of the stylized phantom series are typically situated farther away from one another than within the voxel phantom series. The impact of this work was to characterize the intra-organ and inter-organ distributions to explain the variations in updated internal dose coefficient quantities (i.e. specific absorbed fractions) while providing relevant data defining the spatial and volumetric organ distributions in the phantoms for use in subsequent internal dosimetric computations, with prospective relevance to patient-specific individualized dosimetry, as well as informing machine learning definition of organs using these reference models.
剂量学计算，无论是用于辐射防护还是核医学应用，都受到人体计算模型（称为人体模型）的极大影响。随着模型体模的解剖模型不断发展和扩展，需要量化这些表示之间的差异，这些差异会导致器官剂量系数的变化，无论是来自外部辐射源还是内部发射体。这项工作是对以前努力的扩展，旨在量化标准体模系列和体素体模系列中器官在体内位置的差异。以前的工作主要关注器官相对于模型表面的深度分布，而这里描述的工作通过计算平均弦长来量化器官内和器官间的分布。修订后的橡树岭国家实验室标准体模系列和佛罗里达大学/国家癌症研究所体素体模系列（包括新生儿、1 岁、5 岁、10 岁和 15 岁以及成人）进行了比较。标准体模中的器官距离使用蒙特卡罗辐射传输模拟中的射线追踪技术（通过 MCNP6 提供）计算。体素体模中的器官距离通过体模矩阵操作找到。对体模系列之间器官弦长差异的量化表明，标准体模系列中的器官通常彼此之间的距离更远，而不是在体素体模系列中。这项工作的影响是描述器官内和器官间的分布，以解释更新的内部剂量系数数量（即特定吸收分数）的变化，同时提供定义体模中器官空间和体积分布的相关数据，以便在随后的内部剂量计算中使用，对特定于患者的个体化剂量学具有潜在相关性，并为使用这些参考模型定义器官的机器学习提供信息。
