Lepag M, Jayasakera P M, Bäck S A, Baldock C
Centre for Medical, Health and Environmental Physics, Queensland University of Technology, Brisbane, Australia.
Phys Med Biol. 2001 Oct;46(10):2665-80. doi: 10.1088/0031-9155/46/10/310.
Polymer gel dosimeters of different formulations were manufactured from different monomers of acrylamide, acrylic acid, methacrylic acid, 1-vinyl-2-pyrrolidinone, 2-hydroxyethyl methacrylate and 2-hydroxyethyl acrylate. Gelatin and agarose were used as the gelling agents and N,N'-methylene-bis-acrylamide was used as a co-monomer in each polymer gel dosimeter. The T2 dependence of each dosimeter was analysed using a model of fast exchange of magnetization. The influence of the half-dose and the apparent T2 of the polymer-proton pool on the dose resolution (Dpdelta) were examined. Comparisons are made with the commonly employed R2-dose sensitivity. Differences exist suggesting that experiments reported in the literature using what were thought to be more optimal dosimeters may not actually be so. Based on Dpdelta of each formulation, conclusions are drawn on the optimal formulation required for a specific range of absorbed doses. In addition, information about the extent of polymerization of the monomers used along with some characteristics of the polymer network formed are reported. The influence of the concentration of monomers and gelling agent was subsequently evaluated using a model of fast exchange of magnetization. Based on these calculations, further improvement in Dpdelta can be expected.
不同配方的聚合物凝胶剂量计由丙烯酰胺、丙烯酸、甲基丙烯酸、1-乙烯基-2-吡咯烷酮、甲基丙烯酸2-羟乙酯和丙烯酸2-羟乙酯等不同单体制成。明胶和琼脂糖用作胶凝剂，N,N'-亚甲基双丙烯酰胺在每种聚合物凝胶剂量计中用作共聚单体。使用磁化快速交换模型分析了每个剂量计的T2依赖性。研究了聚合物-质子池的半剂量和表观T2对剂量分辨率（Dpdelta）的影响。与常用的R2剂量敏感性进行了比较。存在差异表明，文献中报道的使用被认为是更优剂量计的实验可能实际上并非如此。基于每种配方的Dpdelta，得出了特定吸收剂量范围内所需的最佳配方。此外，还报告了所用单体的聚合程度以及形成的聚合物网络的一些特性的信息。随后使用磁化快速交换模型评估了单体和胶凝剂浓度的影响。基于这些计算，可以预期Dpdelta会有进一步的改善。
