The authors’ previous study suggested that a simple standing-type whole-body counter called FASTSCAN (Canberra, Meriden, CT, USA), widely installed throughout Japan after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in March 2011, could be used for thyroid measurements in internal dose assessment after a future radiological incident accompanied by the release of 131I into the environment. The present study performed Monte-Carlo simulations using a computational human phantom with several patterns of body surface contamination and used the results to formulate a method for probabilistic analyses of 131I thyroid activity in persons with surface contamination. The major advantage of this method is that the upper limit of the thyroid activity can be determined from the relative frequency distribution without identifying where body surface contamination remains. Therefore, this method is especially effective for use in the early phase of a radiological incident when time and resources are limited, making it difficult to physically remove all body surface contamination for the purpose of gaining more accurate population-wide thyroid screening measurements. As a case study of the FDNPP accident, the proposed method was applied to the results of in vivo measurements for a male subject with body surface contamination. In comparing the probabilistic analyses before and after removal of the subject’s contaminated work clothes, the uncertainty of the relative frequency distribution of 131I thyroid activity was reduced by their removal. Therefore, in terms of accurate estimates and avoidance of radiation exposure from their contaminated clothes, efforts to remove body surface contamination still should be made as much as possible in the chaotic situation of the early phase of a radiological incident.

中文翻译：

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用立式全身计数器直接测量表面污染人员的 131I 甲状腺活动的概率分析，作为放射事件中的紧急反应

作者之前的研究表明，在 2011 年 3 月福岛第一核电站 (FDNPP) 事故后，日本各地广泛安装了一种名为 FASTSCAN（堪培拉，梅里登，康涅狄格州，美国）的简单站立式全身计数器，可用于用于在未来发生伴随 131I 释放到环境中的放射性事件后的内部剂量评估中的甲状腺测量。本研究使用具有多种体表污染模式的计算人体模型进行了蒙特卡罗模拟，并使用结果制定了一种方法，用于对表面污染者的 131I 甲状腺活动进行概率分析。这种方法的主要优点是可以从相对频率分布中确定甲状腺活动的上限，而无需确定体表污染的位置。因此，这种方法在时间和资源有限的放射性事件的早期使用特别有效，因此难以从物理上去除所有体表污染以获得更准确的全人群甲状腺筛查测量结果。作为 FDNPP 事故的案例研究，将所提出的方法应用于体表污染男性受试者的体内测量结果。在比较对象被污染的工作服脱去前后的概率分析时，131I 甲状腺活性的相对频率分布的不确定性因它们的去除而降低。因此，在准确估计和避免被污染衣服的辐射暴露方面，在放射性事件早期的混乱情况下，仍应尽可能地消除体表污染。