甲状腺计数器多尺寸刻度模型研究

目的 为提高甲状腺计数器对大量公众放射性碘（如¹³¹I等）摄入量测量的准确性，开展了甲状腺计数器多尺寸刻度模型研究。方法 首先根据中国成年男性参考人体素模型、不同年龄段人群颈部尺寸和甲状腺质量等数据，建立了涵盖1～15岁儿童、青少年以及成年人的不同年龄段的多尺寸颈部（甲状腺）模型，该模型包含了人体颈部甲状腺、气管、食道、颈椎、骨髓等主要器官和组织；然后使用蒙特卡罗方法模拟了碘化钠型甲状腺计数器对不同类型、不同尺寸刻度模型的探测效率响应。结果 在测量距离为20 cm时，甲状腺计数器对本文建立的成年男性颈部模型TM、IAEA/ANSI颈部模型及中国成年男性参考人颈部体素模型CRAM-neck的探测效率相对偏离小于2%，而对不同尺寸颈部模型的探测效率相对偏离为1%～30%，且模型尺寸差异越大所引起的探测效率相对偏离越大。结论 在测量距离为20 cm时，本文建立的成年男性颈部模型TM可等效IAEA/ANSI颈部模型，而且刻度模型尺寸的差异对甲状腺计数器的探测效率影响较大。因此，建立各年龄段人群，尤其是儿童的颈部（甲状腺）刻度模型对提高测量的准确性有重要意义。

Research on multi-sized phantoms for thyroid counting calibration

Objective In order to improve the accuracy of thyroid counter measurement for radioiodine (such as ¹³¹I) ingested by large amounts of public, multi-sized phantoms for thyroid counting calibration were studied.Method Firstly, multi-sized neck (thyroid) phantoms corresponding to 1～15-year-old children, adolescents and adults were designed according to the data of Chinese reference adult male voxel (CRAM) model, neck size and thyroid mass in different age groups population, and these phantoms included the main organs and tissues of the human neck, such as the thyroid, trachea, esophagus, cervical spine, and bone marrow. Then the Monte Carlo method was used to simulate the detection efficiency response of the NaI (Tl) type thyroid counter to phantoms with different types and sizes.Result When the measurement distance was 20 cm, the relative biases of thyroid counter detection efficiency for IAEA/ANSI neck phantom, CRAM-neck phantom and the adult male neck phantom (TM) were less than 2%, but the relative biases of detection efficiency for different sized neck phantoms were 1%～30%.Conclusion The adult male neck phantom (TM) and IAEA/ANSI neck phantom are equivalent as the measurement distance was 20 cm，and the difference in the size of the calibration phantoms has a big influence on the detection efficiency of thyroid counters. Therefore, it is of great significance for improving the accuracy of measurement to develop neck (thyroid) phantoms corresponding to all age groups, especially for children.