Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD, United States of America.
J Radiol Prot. 2023 May 25;43(2). doi: 10.1088/1361-6498/acd648.
Use of radioactive iodine (RAI) for thyroid cancer patients is accompanied by elevated risks of radiation-induced adverse effects due to significant radiation exposure of normal tissues or organs other than the thyroid. The health risk estimation for thyroid cancer patients should thus be preceded by estimating normal tissue doses. Although organ dose estimation for a large cohort often relies on absorbed dose coefficients (i.e. absorbed dose per unit activity administered, mGy MBq) based on population models, no data are available for thyroid cancer patients. In the current study, we calculated absorbed dose coefficients specific for adult thyroid cancer patients undergoing RAI treatment after recombinant human TSH (rhTSH) administration or thyroid hormone withdrawal (THW). We first adjusted the transfer rates in the biokinetic model previously developed for THW patients for use in rhTSH patients. We then implemented the biokinetic models for thyroid cancer patients coupled withvalues from the International Commission on Radiological Protection (ICRP) reference voxel phantoms to calculate absorbed dose coefficients. The biokinetic model for rhTSH patients predicted the extrathyroidal iodine decreasing noticeably faster than in the model for THW patients (calculated half-times of 12 and 15 h for rhTSH administration and THW, respectively). All dose coefficients for rhTSH patients were lower than those for THW patients with the ratio (rhTSH administration/THW) ranging from 0.60 to 0.95 (mean = 0.67). The ratio of the absorbed dose coefficients in the current study to the ICRP dose coefficients, which were derived from models for normal subjects, varied widely from 0.21 to 7.19, stressing the importance of using the dose coefficients for thyroid cancer patients. The results of this study will provide medical physicists and dosimetrists with scientific evidence to protect patients from excess exposure or to assess radiation-induced health risks caused by RAI treatment.
放射性碘（RAI）在甲状腺癌患者中的应用伴随着因甲状腺以外的正常组织或器官受到显著辐射而导致辐射诱导不良反应的风险增加。因此，在对甲状腺癌患者进行健康风险评估之前，应先估算正常组织剂量。虽然对大样本量患者的器官剂量估算通常依赖于基于人群模型的吸收剂量系数（即单位给予活度的吸收剂量，mGy MBq），但目前尚无甲状腺癌患者的数据。在本研究中，我们针对接受 rhTSH（rhTSH）给药或甲状腺激素抑制（THW）后的甲状腺癌患者，计算了特定的 RAI 治疗的吸收剂量系数。我们首先调整了之前针对 THW 患者开发的生物动力学模型中的转移率，以用于 rhTSH 患者。然后，我们将甲状腺癌患者的生物动力学模型与 ICRP 参考体素模型相结合，以计算吸收剂量系数。rhTSH 患者的生物动力学模型预测甲状腺外碘的减少速度明显快于 THW 患者（rhTSH 给药和 THW 的计算半衰期分别为 12 和 15 小时）。rhTSH 患者的所有剂量系数均低于 THW 患者，比值（rhTSH 给药/THW）范围为 0.60 至 0.95（平均值为 0.67）。与来自正常个体模型的 ICRP 剂量系数相比，当前研究中的吸收剂量系数的比值变化范围从 0.21 到 7.19，这强调了使用甲状腺癌患者剂量系数的重要性。这项研究的结果将为医学物理学家和剂量师提供科学依据，以保护患者免受过度暴露或评估 RAI 治疗引起的辐射诱导健康风险。
