An image-based skeletal tissue model for the ICRP reference newborn
An image-based skeletal tissue model for the ICRP reference newborn
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DOI：
10.1088/0031-9155/54/14/009
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发表时间：
2009-07-21
影响因子：
3.5
通讯作者：
Bolch, Wesley
中科院分区：
文献类型：
--
作者：
Pafundi, Deanna;Lee, Choonsik;Bolch, Wesley
混合幻影代表了第三代人体解剖学计算模型，用于外部和内部辐射照射剂量评估。最近，我们提出了第一个由非均匀有理b样条曲面和多边形网格曲面构成的ICRP参考新生儿的全身混合模型（Lee et al . 2007 Phys.）。医学生物学，52 3309-33)。该模型中的骨骼包括软骨和纤维结缔组织区域，其余部分为皮质骨和小梁骨、活跃骨髓和其他骨骼组织的均匀混合物。在目前的研究中，我们提出了一个综合的ICRP参考新生儿骨骼组织模型，以允许在混合幽灵集（男性和女性）中骨骼的异质表示，明确包括皮质骨的描绘，以便对入射到新生儿骨骼上的低能光子正确建模骨髓屏蔽效应。组织模型的数据来源有三个方面。首先，从整具尸体的CT图像分析中获得均匀骨的骨骼位置相关体积。其次，在尸检时选取新生儿骨标本，对其进行显微ct图像分析，得出骨髓腔和骨小梁三维微结构模型参数。第三，选择ICRP出版物70和89中给出的数据来匹配骨组织总质量的参考值。发现活性骨髓分布与ICRP先前给出的分布合理一致。然而，在当前和ICRP新生儿骨组织模型之间，总骨骼和骨小梁和皮质骨的部位特异性质量存在显著差异。后者采用与年龄无关的80%/20%的皮质骨和小梁骨作为参考新生儿。在目前的研究中，基于新生儿CT和微型CT骨骼图像分析，使用接近40%/60%的比例。当考虑针对新生儿矿物骨的放射性核素的局部骨髓剂量测定时，这些矿物骨成分的变化可能具有重要的剂量学意义。
Hybrid phantoms represent a third generation of computational models of human anatomy needed for dose assessment in both external and internal radiation exposures. Recently, we presented the first whole-body hybrid phantom of the ICRP reference newborn with a skeleton constructed from both non-uniform rational B-spline and polygon-mesh surfaces (Lee et al 2007 Phys. Med. Biol. 52 3309-33). The skeleton in that model included regions of cartilage and fibrous connective tissue, with the remainder given as a homogenous mixture of cortical and trabecular bone, active marrow and miscellaneous skeletal tissues. In the present study, we present a comprehensive skeletal tissue model of the ICRP reference newborn to permit a heterogeneous representation of the skeleton in that hybrid phantom set-both male and female-that explicitly includes a delineation of cortical bone so that marrow shielding effects are correctly modeled for low-energy photons incident upon the newborn skeleton. Data sources for the tissue model were threefold. First, skeletal site-dependent volumes of homogeneous bone were obtained from whole-cadaver CT image analyses. Second, selected newborn bone specimens were acquired at autopsy and subjected to micro-CT image analysis to derive model parameters of the marrow cavity and bone trabecular 3D microarchitecture. Third, data given in ICRP Publications 70 and 89 were selected to match reference values on total skeletal tissue mass. Active marrow distributions were found to be in reasonable agreement with those given previously by the ICRP. However, significant differences were seen in total skeletal and site-specific masses of trabecular and cortical bone between the current and ICRP newborn skeletal tissue models. The latter utilizes an age-independent ratio of 80%/20% cortical and trabecular bone for the reference newborn. In the current study, a ratio closer to 40%/60% is used based upon newborn CT and micro-CT skeletal image analyses. These changes in mineral bone composition may have significant dosimetric implications when considering localized marrow dosimetry for radionuclides that target mineral bone in the newborn child.