Ramos V S, Crispim V R, Brandão L E B
Universidade Federal do Rio de Janeiro, UFRJ/CT/COPPE/Programa de Engenharia Nuclear, Av. Horácio Macedo, 2030, Bloco G, Sala 206, Cidade Universitária, CEP: 21941-914, Rio de Janeiro-RJ, Brazil.
Appl Radiat Isot. 2013 Dec;82:111-8. doi: 10.1016/j.apradiso.2013.07.029. Epub 2013 Aug 7.
In Nuclear Medicine, radioiodine, in various chemical forms, is a key tracer used in diagnostic practices and/or therapy. Medical professionals may incorporate radioactive iodine during the preparation of the dose to be administered to the patient. In radioactive iodine therapy doses ranging from 3.7 to 7.4 GBq per patient are employed. Thus, aiming at reducing the risk of occupational contamination, we developed a low cost filter to be installed at the exit of the exhaust system (where doses of radioiodine are handled within fume hoods, and new filters will be installed at their exit), using domestic technology. The effectiveness of radioactive iodine retention by silver impregnated silica [10%] crystals and natural activated carbon was verified using radiotracer techniques. The results showed that natural activated carbon and silver impregnated silica are effective for I2 capture with large or small amounts of substrate but the use of activated carbon is restricted due to its low flash point (423 K). Besides, when poisoned by organic solvents, this flash point may become lower, causing explosions if absorbing large amounts of nitrates. To hold the CH3I gas, it was necessary to use natural activated carbon since it was not absorbed by SiO2+Ag crystals. We concluded that, for an exhaust flow range of (145 ± 2)m(3)/h, a double stage filter using SiO2+Ag in the first stage and natural activated carbon in the second stage is sufficient to meet radiological safety requirements.
在核医学中，各种化学形式的放射性碘是诊断实践和/或治疗中使用的关键示踪剂。医学专业人员在制备给患者施用的剂量时可能会加入放射性碘。在放射性碘治疗中，每位患者使用的剂量范围为3.7至7.4吉贝可。因此，为了降低职业污染风险，我们利用国内技术开发了一种低成本过滤器，安装在排气系统出口处（在通风橱内处理放射性碘剂量的地方，并在其出口处安装新的过滤器）。使用放射性示踪技术验证了含银[10%]硅胶晶体和天然活性炭对放射性碘的保留效果。结果表明，天然活性炭和含银硅胶对大量或少量底物的I2捕获均有效，但由于活性炭闪点低（423K），其使用受到限制。此外，当被有机溶剂中毒时，该闪点可能会降低，如果吸收大量硝酸盐会导致爆炸。为了捕获CH3I气体，必须使用天然活性炭，因为它不会被SiO2+Ag晶体吸收。我们得出结论，对于（145±2）立方米/小时的排气流量范围，采用第一阶段为SiO2+Ag、第二阶段为天然活性炭的两级过滤器足以满足放射安全要求。
