The dose response of the BANG®3 polymer gel dosimeter (MGS Research Inc., Madison, CT) was studied using the OCTOPUS™ laser CT scanner (MGS Research Inc., Madison, CT). Six 17 cm diameter and 12 cm high Barex cylinders, and 18 small glass vials were used to house the gel. The gel phantoms were irradiated with 6 and 10 MV photons, as well as 12 and 16 MeV electrons using a Varian Clinac 2100EX. Three calibration methods were used to obtain the dose response curves: (a) Optical density measurements on the 18 glass vials irradiated with graded doses from 0 to 4 Gy using 6 or 10 MV large field irradiations; (b) optical-CT scanning of Barex cylinders irradiated with graded doses (0.5, 1, 1.5, and 2 Gy) from four adjacent 4×4 cm2 photon fields or 6×6 cm2 electron fields; and (c) percent depth dose (PDD) comparison of optical-CT scans with ion chamber measurements for 6×6 cm2, 12 and 16 MeV electron fields. The dose response of the BANG®3 gel was found to be linear and energy independent within the uncertainties of the experimental methods (about 3%). The slopes of the linearly fitted dose response curves (dose sensitivities) from the four field irradiations (0.0752±3%, 0.0756±3%, 0.0767±3%, and 0.0759±3% cm−1 Gy−1) and the PDD matching methods (0.0768±3% and 0.0761±3% cm−1 Gy−1) agree within 2.2%, indicating a good reproducibility of the gel dose response within phantoms of the same geometry. The dose sensitivities from the glass vial approach are different from those of the cylindrical Barex phantoms by more than 30%, owing probably to the difference in temperature inside the two types of phantoms during gel formation and irradiation, and possible oxygen contamination of the glass vial walls. The dose response curve obtained from the PDD matching approach with 16 MeV electron field was used to calibrate the gel phantom irradiated with the 12 MeV, 6×6 cm2 electron field. Three-dimensional dose distributions from the gel measurement and the Eclipse planning system (Varian Corporation, Palo Alto, CA) were compared and evaluated using 3% dose difference and 2 mm distance-to-agreement criteria.
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机译：使用OCTOPUS ™激光CT扫描仪（MGS Research Inc.，BANG ® 3聚合物凝胶剂量计（MGS Research Inc.，麦迪逊，CT）研究了剂量响应麦迪逊（CT）。六个直径17厘米，高12厘米的Barex圆筒和18个小玻璃瓶用于容纳凝胶。使用Varian Clinac 2100EX用6和10 MV光子以及12和16 MeV电子辐照凝胶体模。三种校准方法用于获得剂量响应曲线：（a）使用6或10 MV大场辐照，在从0到4 Gy分级剂量辐照的18个玻璃小瓶上进行光密度测量； （b）对来自四个相邻的4×4 cm 2 光子场或6×6 cm 的梯度剂量（0.5、1、1.5和2 Gy）照射的Barex圆柱进行光学CT扫描2 电子场； （c）比较6-6 cm 2 ，12和16 MeV电子场的光学CT扫描与离子室测量的深度剂量百分比（PDD）。在实验方法的不确定性范围内（约3％），发现BANG ® 3凝胶的剂量响应呈线性且能量无关。四个场照射（0.0752±3％，0.0756±3％，0.0767±3％和0.0759±3％）cm -1 Gy的线性拟合剂量响应曲线（剂量敏感性）的斜率 -1 ）和PDD匹配方法（0.0768±3％和0.0761±3％cm -1 Gy -1 ）在2.2％之内，表明在相同几何体模内的凝胶剂量响应具有良好的可重复性。玻璃小瓶方法的剂量敏感性与圆柱形Barex幻象的剂量敏感性相差30％以上，这可能是由于在凝胶形成和照射过程中两种类型的幻象内部的温度差异以及玻璃小瓶可能存在的氧污染墙壁。用PDD匹配法在16 MeV电子场下得到的剂量响应曲线，对12 MeV，6×6 cm 2 电子场辐照的凝胶体模进行校正。比较了凝胶测量和Eclipse规划系统（Varian Corporation，Palo Alto，CA）的三维剂量分布，并使用3％的剂量差异和2毫米的达成协议标准进行了评估。
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