Department of Nuclear and Radiological Engineering, University of Florida, Gainesville, FL, USA.
Phys Med Biol. 2011 Aug 7;56(15):4839-79. doi: 10.1088/0031-9155/56/15/014. Epub 2011 Jul 15.
Historically, the development of computational phantoms for radiation dosimetry has primarily been directed at capturing and representing adult and pediatric anatomy, with less emphasis devoted to models of the human fetus. As concern grows over possible radiation-induced cancers from medical and non-medical exposures of the pregnant female, the need to better quantify fetal radiation doses, particularly at the organ-level, also increases. Studies such as the European Union's SOLO (Epidemiological Studies of Exposed Southern Urals Populations) hope to improve our understanding of cancer risks following chronic in utero radiation exposure. For projects such as SOLO, currently available fetal anatomic models do not provide sufficient anatomical detail for organ-level dose assessment. To address this need, two fetal hybrid computational phantoms were constructed using high-quality magnetic resonance imaging and computed tomography image sets obtained for two well-preserved fetal specimens aged 11.5 and 21 weeks post-conception. Individual soft tissue organs, bone sites and outer body contours were segmented from these images using 3D-DOCTOR™ and then imported to the 3D modeling software package Rhinoceros™ for further modeling and conversion of soft tissue organs, certain bone sites and outer body contours to deformable non-uniform rational B-spline surfaces. The two specimen-specific phantoms, along with a modified version of the 38 week UF hybrid newborn phantom, comprised a set of base phantoms from which a series of hybrid computational phantoms was derived for fetal ages 8, 10, 15, 20, 25, 30, 35 and 38 weeks post-conception. The methodology used to construct the series of phantoms accounted for the following age-dependent parameters: (1) variations in skeletal size and proportion, (2) bone-dependent variations in relative levels of bone growth, (3) variations in individual organ masses and total fetal masses and (4) statistical percentile variations in skeletal size, individual organ masses and total fetal masses. The resulting series of fetal hybrid computational phantoms is applicable to organ-level and bone-level internal and external radiation dosimetry for human fetuses of various ages and weight percentiles.
从历史上看，用于辐射剂量学的计算体模的开发主要集中在捕获和表示成人和儿科解剖结构上，而对人体胎儿模型的关注较少。随着人们对孕妇接受医疗和非医疗辐射可能导致癌症的担忧日益增加，人们越来越需要更好地量化胎儿的辐射剂量，特别是在器官水平上。欧盟的 SOLO（暴露于南部乌拉尔人群的流行病学研究）等研究希望增进我们对宫内慢性辐射暴露后癌症风险的了解。对于 SOLO 等项目，目前可用的胎儿解剖模型无法为器官水平的剂量评估提供足够的解剖细节。为了解决这一需求，使用高质量的磁共振成像和计算机断层扫描图像集构建了两个胎儿混合计算体模，这些图像集是为两个保存完好的孕 11.5 周和 21 周的胎儿标本获得的。使用 3D-DOCTOR™ 从这些图像中分割出个体软组织器官、骨部位和外体轮廓，然后将其导入 3D 建模软件包 Rhinoceros™ 进行进一步建模，并将软组织器官、某些骨部位和外体轮廓转换为可变形的非均匀有理 B 样条曲面。这两个特定于标本的体模，以及修改后的 38 周 UF 混合新生儿体模，构成了一组基础体模，从中衍生出一系列混合计算体模，用于胎儿年龄 8、10、15、20、25、30、35 和 38 周。构建一系列体模所使用的方法考虑了以下与年龄相关的参数：（1）骨骼大小和比例的变化，（2）骨骼生长相对水平的骨骼依赖性变化，（3）个体器官质量和总胎儿质量的变化，以及（4）骨骼大小、个体器官质量和总胎儿质量的统计百分位数变化。由此产生的一系列胎儿混合计算体模适用于各种年龄和体重百分位数的胎儿的器官水平和骨水平的内部和外部辐射剂量学。
