Brill A B, Stabin M, Bouville A, Ron E
Vanderbilt University, Nashville, Tennessee 37232, USA.
Radiat Res. 2006 Jul;166(1 Pt 2):128-40. doi: 10.1667/RR3558.1.
In many medical applications involving the administration of iodine-131 ((131)I) in the form of iodide (I(-)), most of the dose is delivered to the thyroid gland. To reliably estimate the thyroid absorbed dose, the following data are required: the thyroid gland size (i.e. mass), the fractional uptake of (131)I by the thyroid, the spatial distribution of (131)I within the thyroid, and the length of time (131)I is retained in the thyroid before it is released back to blood, distributed in other organs and tissues, and excreted from the body. Estimation of absorbed dose to nonthyroid tissues likewise requires knowledge of the time course of activity in each organ. Such data are rarely available, however, and therefore dose calculations are generally based on reference models. The MIRD and ICRP have published metabolic models and have calculated absorbed doses per unit intake for many nuclides and radioactive pharmaceuticals. Given the activity taken into the body, one can use such models and make reasonable calculations for average organ doses. When normal retention and excretion pathways are altered, the baseline models need to be modified, and the resulting organ dose estimates are subject to larger errors. This paper describes the historical evolution of radioactive isotopes in medical diagnosis and therapy. We nonmathematically summarize the methods used in current practice to estimate absorbed dose and summarize some of the risk data that have emerged from medical studies of patients with special attention to dose and effects observed in those who received (131)I-iodide in diagnosis and/or therapy.
在许多涉及以碘化物（I⁻）形式给予碘 - 131（¹³¹I）的医学应用中，大部分剂量会输送到甲状腺。为了可靠地估计甲状腺吸收剂量，需要以下数据：甲状腺大小（即质量）、甲状腺对¹³¹I的摄取分数、¹³¹I在甲状腺内的空间分布，以及¹³¹I在释放回血液、分布到其他器官和组织并从体内排出之前在甲状腺中保留的时间长度。同样，估计非甲状腺组织的吸收剂量需要了解每个器官中放射性活度随时间的变化过程。然而，此类数据很少可得，因此剂量计算通常基于参考模型。医学内照射剂量（MIRD）委员会和国际辐射防护委员会（ICRP）已经发布了代谢模型，并计算了许多核素和放射性药物每单位摄入量的吸收剂量。给定摄入体内的放射性活度，人们可以使用此类模型并对平均器官剂量进行合理计算。当正常的滞留和排泄途径发生改变时，需要修改基线模型，并且由此得出的器官剂量估计会有较大误差。本文描述了放射性同位素在医学诊断和治疗中的历史演变。我们以非数学方式总结了当前实践中用于估计吸收剂量的方法，并总结了一些医学研究中出现的风险数据，特别关注了在诊断和/或治疗中接受¹³¹I - 碘化物的患者所观察到的剂量和效应。
