人体、大鼠和小鼠甲状腺模型中的 211At 微剂量分析。

Microdosimetric analysis of 211At in thyroid models for man, rat and mouse.

机构信息

Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Cancer Center, Sahlgrenska Academy at the University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, 413 45, Sweden.

出版信息

EJNMMI Res. 2012 Jun 9;2(1):29. doi: 10.1186/2191-219X-2-29.

DOI:10.1186/2191-219X-2-29

PMID:22682159

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC3444346/

Abstract

BACKGROUND

The alpha particle emitter 211At is proposed for therapy of metastatic tumour disease. 211At is accumulated in the thyroid gland in a similar way as iodine. Dosimetric models of 211At in the thyroid are needed for radiation protection assessments for 1) patients receiving 211At-labelled pharmaceuticals where 211At may be released in vivo and 2) personnel working with 211At. Before clinical trials, preclinical studies are usually made in mice and rats. The aims of this study were to develop thyroid models for mouse, rat and man, and to compare microdosimetric properties between the models.

METHODS

A thyroid follicle model was constructed: a single layer of 6 to 10-μm thick follicle cells with centrally positioned 4 to 8 μm (diameter) spherical nuclei surrounded a 10 to 500 μm (diameter) spherical follicle lumen. Species-specific models were defined for mouse, rat and man. The source compartments for 211At were the follicle lumen, follicle cells and follicle cell nuclei. The target was the follicle cell nucleus. Simplified species-specific thyroid models were used to investigate the contribution from surrounding follicles. Monte Carlo simulations were performed using the general purpose radiation transport code MCNPX 2.6.0.

RESULTS

When 211At was homogeneously distributed within the follicle lumen, the mean specific energies per decay, 〈z〉, to the follicle cell nucleus were 2.0, 1.1 and 0.17 mGy for mouse, rat and man, respectively. Corresponding values for the single-hit mean specific energy per decay, 〈z1〉, were 1.3, 0.61 and 0.37 Gy. Assuming a homogeneous 211At concentration in the follicle lumen, <0.5%, 7%, and 45% of the emitted alpha particles were fully stopped within the follicle lumen for the respective models.

CONCLUSIONS

The results clearly show the influence of the follicle size, alpha particle range and 211At location within the thyroid follicle on the dosimetric parameters. Appropriate thyroid models are required for translation of dosimetric parameters between species.

摘要

背景

α粒子发射体 211At 被提议用于治疗转移性肿瘤疾病。211At 在甲状腺中的积累方式与碘类似。需要 211At 在甲状腺中的剂量学模型，用于 1）接受 211At 标记药物的患者的辐射防护评估，其中 211At 可能在体内释放，2）与 211At 一起工作的人员。在临床试验之前，通常在小鼠和大鼠中进行临床前研究。本研究的目的是为小鼠、大鼠和人开发甲状腺模型，并比较模型之间的微剂量学特性。

方法

构建了甲状腺滤泡模型：单层 6 至 10μm 厚的滤泡细胞，中央有 4 至 8μm（直径）的球形核，周围有 10 至 500μm（直径）的球形滤泡腔。为小鼠、大鼠和人定义了特定物种的模型。211At 的源室是滤泡腔、滤泡细胞和滤泡细胞核。靶标是滤泡细胞核。使用简化的特定物种甲状腺模型来研究来自周围滤泡的贡献。使用通用辐射传输代码 MCNPX 2.6.0 进行蒙特卡罗模拟。

结果

当 211At 均匀分布在滤泡腔中时，滤泡细胞核的每衰变平均特定能量，〈z〉，分别为小鼠、大鼠和人类的 2.0、1.1 和 0.17mGy。相应的单击中每衰变平均特定能量，〈z1〉，的值分别为 1.3、0.61 和 0.37Gy。假设滤泡腔中 211At 浓度均匀，<0.5%、7%和 45%的发射α粒子在各自的模型中完全被滤泡腔停止。