Abstract The need to quantify the uptake of 131I in the thyroid of the exposed population or workers is one of the main concerns to take into account in case of nuclear or radiological emergencies. In such scenarios, due to the high volatility and rapid intake by inhalation of 131I, it is very important a rapid identification of the exposed individuals to know their level of internal contamination in order to establish action protocols and countermeasures. In vivo measurements of 131I in the thyroid by gamma spectrometry at Whole Body Counters (WBC) is the recommended technique, but it is difficult to manage in case of a large number of individuals potentially exposed. It is known that gamma cameras located in the nuclear medicine services are available at most hospitals and could be used as an alternative method in order to provide support in the emergency response. Thus, this work describes a methodology to calibrate this kind of equipment with anthropometric phantoms to carry out direct measurement of 131I in thyroid for the quantification of internal contamination of the exposed population. A Gamma Camera (GC) of a public hospital from Madrid, H.U. La Paz, was calibrated for such purpose taking into account that a realistic geometry (10 cm distance from GC to phantom) and a rapid screening (counting time of 300 s with collimators removed) of internally contaminated individuals is necessary at early stage response. The calibration factors obtained for 131I vary with thyroid size being in the range of 0.0459 to 0.0541 cps·Bq-1. The minimum detectable activity (MDA) also varies with the thyroid size of the phantoms being in the range of 67 Bq to 79 Bq. An estimation of minimum detectable effective dose for children (E(70)) and adults (E(50)) has been carried out, taking into account such MDA values. Results show that, assuming a scenario of acute inhalation of 131I by members of the public, this methodology allows estimating doses far below 1 mSv three days after the intake. Moreover, the validation of the methodology has been carried out by participating in an international intercomparison exercise (CATHYMARA project, EC-OPERRA 2016–2017) for the in vivo measurement of 131I in thyroid to the exposed population in emergencies.

中文翻译：

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校准带有儿童和成人甲状腺颈部模型的 SPECT-CT 伽马相机，用于在核紧急情况下对暴露人群中的放射性碘进行体内监测

摘要 需要对暴露人群或工人的甲状腺中 131I 的摄取进行量化，这是在核或放射紧急情况下需要考虑的主要问题之一。在这种情况下，由于吸入 131I 的高挥发性和快速摄入，快速识别暴露个体以了解他们的内部污染水平以制定行动方案和对策非常重要。在全身计数器 (WBC) 上通过伽马光谱法对甲状腺中的 131I 进行体内测量是推荐的技术，但在可能接触大量个体的情况下很难管理。众所周知，大多数医院都可以使用位于核医学服务中的伽马照相机，并且可以将其用作替代方法，以便在应急响应中提供支持。因此，这项工作描述了一种用人体测量模型校准此类设备的方法，以直接测量甲状腺中的 131I，以量化暴露人群的内部污染。马德里胡拉巴斯公立医院的伽玛相机 (GC) 为此目的进行了校准，考虑到真实的几何形状（从 GC 到幻影的距离为 10 厘米）和快速筛选（使用准直器的计数时间为 300 秒）移除）内部受污染的个体在早期反应中是必要的。为 131I 获得的校准因子随甲状腺大小在 0 范围内变化。0459 至 0.0541 cps·Bq-1。最小可检测活动 (MDA) 也随着幻影的甲状腺大小在 67 Bq 到 79 Bq 的范围内变化。考虑到此类 MDA 值，已对儿童 (E(70)) 和成人 (E(50)) 的最小可检测有效剂量进行了估计。结果表明，假设公众成员急性吸入 131I，这种方法允许在摄入三天后估计远低于 1 毫希沃特的剂量。此外，通过参加国际比对演习（CATHYMARA 项目，EC-OPERRA 2016-2017）对该方法进行了验证，该演习用于在紧急情况下对暴露人群进行甲状腺中 131I 的体内测量。最低可检测活动 (MDA) 也随着幻影的甲状腺大小在 67 Bq 到 79 Bq 的范围内变化。考虑到此类 MDA 值，已对儿童 (E(70)) 和成人 (E(50)) 的最小可检测有效剂量进行了估计。结果表明，假设公众成员急性吸入 131I，这种方法允许在摄入三天后估计远低于 1 毫希沃特的剂量。此外，通过参加国际比对演习（CATHYMARA 项目，EC-OPERRA 2016-2017）对该方法进行了验证，该演习用于在紧急情况下对暴露人群进行甲状腺 131I 的体内测量。最小可检测活动 (MDA) 也随着幻影的甲状腺大小在 67 Bq 到 79 Bq 的范围内变化。考虑到此类 MDA 值，已经对儿童 (E(70)) 和成人 (E(50)) 的最小可检测有效剂量进行了估计。结果表明，假设公众成员急性吸入 131I，这种方法允许在摄入三天后估计远低于 1 毫希沃特的剂量。此外，通过参加国际比对演习（CATHYMARA 项目，EC-OPERRA 2016-2017）对该方法进行了验证，该演习用于在紧急情况下对暴露人群进行甲状腺中 131I 的体内测量。考虑到此类 MDA 值。结果表明，假设公众成员急性吸入 131I，这种方法允许在摄入三天后估计远低于 1 毫希沃特的剂量。此外，通过参加国际比对演习（CATHYMARA 项目，EC-OPERRA 2016-2017）对该方法进行了验证，该演习用于在紧急情况下对暴露人群进行甲状腺中 131I 的体内测量。考虑到此类 MDA 值。结果表明，假设公众成员急性吸入 131I，这种方法允许在摄入三天后估计远低于 1 毫希沃特的剂量。此外，通过参加国际比对演习（CATHYMARA 项目，EC-OPERRA 2016-2017）对该方法进行了验证，该演习用于在紧急情况下对暴露人群进行甲状腺中 131I 的体内测量。