Venning A J, Hill B, Brindha S, Healy B J, Baldock C
School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, Qld 4001, Australia.
Phys Med Biol. 2005 Aug 21;50(16):3875-88. doi: 10.1088/0031-9155/50/16/015. Epub 2005 Aug 2.
Investigation of the normoxic PAGAT polymer gel dosimeter has been undertaken. The concentrations of the chemical components of the gel were varied and its response to ionizing radiation evaluated. Using MRI, the formulation to give the maximum change in the transverse relaxation rate R2 was determined to be 4.5% N, N'-methylene-bis-acrylamide (bis), 4.5% acrylamide (AA), 5% gelatine, 5 mM tetrakis (hydroxymethyl) phosphonium chloride (THPC), 0.01 mM hydroquinone (HQ) and 86% H2O. The optimal post-manufacture irradiation and post-irradiation imaging times were both determined to be 12 h. The R2-dose response was linear up to 7 Gy with R2-dose sensitivities of (0.183 +/- 0.005) s(-1) Gy(-1), (0.182 +/- 0.005) s(-1) Gy(-1) and (0.192 +/- 0.005) s(-1) Gy(-1) when imaged at 12 h, 7 days and 24 days post-irradiation, respectively. The R2-dose sensitivities were within the range of previously published values for the hypoxic PAG formulations. For the imaging parameters used in this study the optimum dose resolution was achieved for low doses. The normalized R2 edge response showed a high degree of spatial stability over a 24 day period. This study has shown that the normoxic PAGAT polymer gel has the properties of a dosimetric tool, which can be used in clinical radiotherapy. The PAGAT polymer gel has been shown to have similar qualities to the PAG polymer gel, while offering the significant advantage of simplification of the manufacturing procedure.
已对常氧PAGAT聚合物凝胶剂量计进行了研究。改变了凝胶化学成分的浓度，并评估了其对电离辐射的响应。通过磁共振成像（MRI），确定能使横向弛豫率R2产生最大变化的配方为：4.5%的N，N'-亚甲基双丙烯酰胺（双丙烯酰胺）、4.5%的丙烯酰胺（AA）、5%的明胶、5 mM的四（羟甲基）氯化鏻（THPC）、0.01 mM的对苯二酚（HQ）和86%的水。确定最佳的制造后辐照时间和辐照后成像时间均为12小时。在高达7 Gy的剂量范围内，R2-剂量响应呈线性，在辐照后12小时、7天和24天成像时，R2-剂量敏感度分别为(0.183±0.005) s(-1) Gy(-1)、(0.182±0.005) s(-1) Gy(-1)和(0.192±0.005) s(-1) Gy(-1)。这些R2-剂量敏感度在先前公布的低氧PAG配方值范围内。对于本研究中使用的成像参数，低剂量时可实现最佳剂量分辨率。归一化的R2边缘响应在24天内显示出高度的空间稳定性。本研究表明，常氧PAGAT聚合物凝胶具有剂量测定工具的特性，可用于临床放射治疗。已证明PAGAT聚合物凝胶具有与PAG聚合物凝胶相似的品质，同时具有简化制造程序的显著优势。
