Department of Chemical and Biochemical Engineering, The University of Western Ontario, London, Ontario, N6A5B9, Canada.
Phys Med Biol. 2013 Mar 21;58(6):1823-38. doi: 10.1088/0031-9155/58/6/1823. Epub 2013 Feb 26.
The ferrous-xylenol orange-gelatin (FXG) dosimeter is widely used for three-dimensional ionizing radiation field mapping through optical scanning. Upon irradiation, the ferrous iron (Fe(2+)) is oxidized to ferric iron (Fe(3+)), which forms an intensely coloured complex with xylenol orange (XO). XO also acts as a diffusion-limiting additive; however, its presence may cause rapid auto-oxidation of Fe(2+) during storage and low stability of the dose response. In this work, phenanthroline-type ligands were added to FXG system in a bid to bind the ferrous iron in a stable complex and minimize the rate of the auto-oxidation, whereas glyoxal was used as a chemical cross-linker, aiming to minimize the ferric iron diffusion. It was found that addition of either 1,10-phenanthroline or 5-nitro-1,10-phenanthroline can improve the auto-oxidation behaviour of the gels. However, the initial background absorbance was slightly increased, and the sensitivity of the dosimeters was decreased. Doping with glyoxal led to a moderate decrease of the diffusion only in those gels that also contained a phenanthroline-type ligand, and did not affect the initial dose response. Glyoxal also afforded an extended period of stable background absorbance level after an initial period of bleaching of the gel. Following re-irradiation, most glyoxal-containing dosimeters showed an excellent linearity of the dose response, albeit at a decreased sensitivity. We recommend further testing of FXG dosimeters, doped with phenanthroline-type ligands and glyoxal as a means for controlling the dose response and improving the long-term storage properties of the gels and the potential for dose fractionation.
亚铁-二甲苯酚橙-明胶（FXG）剂量计通过光学扫描广泛用于三维离子辐射场测绘。辐照后，亚铁（Fe(2+)）被氧化为三价铁（Fe(3+)），后者与二甲苯酚橙（XO）形成强烈显色络合物。XO 还作为扩散限制添加剂；然而，其存在可能导致 Fe(2+)在储存过程中的快速自氧化和剂量响应的低稳定性。在这项工作中，向 FXG 系统中添加菲啰啉型配体，以将亚铁稳定地形成配合物，并最小化自氧化速率，而乙二醛则用作化学交联剂，旨在最小化三价铁的扩散。结果发现，添加 1,10-菲啰啉或 5-硝基-1,10-菲啰啉均可改善凝胶的自氧化行为。然而，初始背景吸光度略有增加，剂量计的灵敏度降低。仅在含有菲啰啉型配体的凝胶中，添加乙二醛会导致扩散适度降低，而不会影响初始剂量响应。乙二醛还可以在凝胶初始褪色后提供稳定背景吸光度水平的延长稳定期。再辐照后，大多数含有乙二醛的剂量计表现出剂量响应的优异线性度，尽管灵敏度降低。我们建议进一步测试 FXG 剂量计，掺杂菲啰啉型配体和乙二醛作为控制剂量响应和改善凝胶的长期储存性能以及剂量分割潜力的手段。
