Clinical Research Directorate, Frederick National Laboratory for Cancer Research sponsored by the National Cancer Institute, Frederick MD.
Molecular Imaging Program. National Cancer Institute, National Institutes of Health, Bethesda, MD.
Health Phys. 2020 Feb;118(2):149-161. doi: 10.1097/HP.0000000000001132.
A study of Pb contamination caused by the outgassing of Rn from Ra in dry, liquid, and murine tissues samples has been made to help design proper handling procedures for Ra in preclinical biodistribution work.
Pb activity levels were measured from Ra in dry, liquid, and tissue samples using aspiration and autoradiography techniques.
Using aspiration techniques on dry samples of Ra, an average Rn outgassing rate of 51% ± 21% was measured with one measurement reaching as high as 81%. 31% ± 4% Pb contamination was measured within a 4.3 cm radius of a dry Ra source placed inside a 10-cm-diameter petri dish where the lip of the petri dish contained the Rn dissemination. Without the containment of the petri dish, Rn can reach as far as 7.8 cm from the source with trace levels spreading further. Using aspiration techniques on liquid samples of Ra, outgassing rates of Rn were 0.9% ± 0.3%. The outgassing levels in harvested organs from a biodistribution were as high as 10.1% ± 0.4% for an intraperitoneally injected mouse and 0.204% ± 0.006% for an intravenously injected mouse. The outgassing of the intravenously injected mouse carcass was less than 0.1%.
In dry form, the high levels of Rn outgassing from a Ra source necessitate the use of ventilated biohoods when handling or preparing dry Ra from source vials. The very low levels of Rn outgassing from Ra liquid sources reduces exposure to Rn by a factor of 50. Rn exposure from murine organ tissue reaches levels of 10% when handling organs from an intraperitoneal injection and less than 0.2% for an intravenous injection.
本研究旨在探讨氡（Rn）从镭（Ra）逸出对 Pb 污染的影响，以帮助设计临床前生物分布研究中 Ra 的适当处理程序。
采用吸气和放射自显影技术测量干燥、液体和组织样本中 Ra 中的 Pb 活性水平。
采用吸气技术测量干燥的 Ra 样本，Ra 的平均 Rn 逸出率为 51%±21%，其中一次测量高达 81%。在直径为 10cm 的培养皿内放置一个干燥的 Ra 源，距 Ra 源 4.3cm 半径范围内测量到 31%±4%的 Pb 污染，培养皿的边缘包含 Rn 的传播。如果不限制培养皿的传播，Rn 可以从源扩散到距离源 7.8cm 的地方，且微量的 Rn 还会进一步扩散。采用吸气技术测量液体 Ra 样本，Rn 的逸出率为 0.9%±0.3%。从生物分布中收获的器官中，腹腔注射小鼠的逸出率高达 10.1%±0.4%，静脉注射小鼠的逸出率为 0.204%±0.006%。静脉注射小鼠的尸体逸出量小于 0.1%。
在干燥形式下，Ra 源中 Rn 的高逸出率需要在处理或从源小瓶制备干燥 Ra 时使用通风生物罩。Ra 液体源中 Rn 的极低逸出率使 Rn 暴露减少了 50 倍。当处理腹腔注射的器官时，从鼠组织器官中接触到的 Rn 水平达到 10%，而静脉注射的 Rn 水平小于 0.2%。
