Lobaugh Megan L, Spitz Henry B, Glover Samuel E
*University of Cincinnati, Nuclear and Radiological Engineering Program, 598 Rhodes Hall, Cincinnati, OH 45221-0072; †Currently at Lawrence Livermore National Laboratory, Livermore, CA 94550.
Health Phys. 2015 Jan;108(1):67-75. doi: 10.1097/HP.0000000000000168.
Radioactive material deposited in multiple organs of the body is likely to confound a result of an in vivo measurement performed over the lungs, the most frequently monitored organ for occupational exposure. The significance of this interference was evaluated by measuring anthropometric torso phantoms containing lungs, liver, skeleton, and axillary lymph nodes, each with a precisely known quantity of 241Am uniformly distributed in the organs. Arrays of multiple high-resolution germanium detectors were positioned over organs within the torso phantom containing 241Am or over proximal organs without activity to determine the degree of measurement confounding due to photons emitted from other source organs. A set of four mathematical response functions describes the measured count rate with detectors positioned over each of the relevant organs and 241Am contained in the measured organ or one of the other organs selected as a confounder. Simultaneous solution of these equations by matrix algebra, where the diagonal terms of the matrix are calibration factors for a direct measurement of activity in an organ and the off-diagonal terms reflect the contribution (i.e., interference or cross-talk) produced by 241Am in a confounding organ, yields the activity deposited in each of the relevant organs. The matrix solution described in this paper represents a method for adjusting a result of 241Am measured directly in one organ for interferences that may arise from 241Am deposited elsewhere and represents a technically valid procedure to aid in evaluating internal dose based upon in vivo measurements for those radioactive materials known to deposit in multiple organs.
沉积在身体多个器官中的放射性物质可能会混淆对肺部进行的体内测量结果，肺部是职业暴露中最常监测的器官。通过测量包含肺、肝、骨骼和腋窝淋巴结的人体测量躯干模型来评估这种干扰的重要性，每个模型的器官中都均匀分布有精确已知量的241Am。多个高分辨率锗探测器阵列被放置在含有241Am的躯干模型内的器官上方，或放置在无放射性的近端器官上方，以确定由于其他源器官发射的光子导致的测量混淆程度。一组四个数学响应函数描述了探测器放置在每个相关器官上方且测量器官或被选为混杂因素的其他器官之一中含有241Am时的测量计数率。通过矩阵代数同时求解这些方程，其中矩阵的对角项是器官中活性直接测量的校准因子，非对角项反映了241Am在混杂器官中产生的贡献（即干扰或串扰），从而得出沉积在每个相关器官中的活性。本文所述的矩阵解法代表了一种针对在一个器官中直接测量的241Am结果进行调整的方法，以应对可能由沉积在其他部位的241Am产生的干扰，并且代表了一种技术上有效的程序，有助于基于对已知沉积在多个器官中的放射性物质的体内测量来评估内照射剂量。
