Novotny J, Spevacek V, Dvorak P, Novotny J, Cechak T
Department of Stereotactic and Radiation Neurosurgery, Hospital Na Homolce, Roentgenova 2, 150 30 Prague 5, The Czech Republic.
Med Phys. 2001 Nov;28(11):2379-86. doi: 10.1118/1.1414307.
The purpose of this study was to evaluate dependence of BANG-2 polymer-gel dosimeter sensitivity on different photon and electron energies as well as on different mean dose rates expressed as repetition rates for a standard clinically used linear accelerator. The sensitivity of the dosimeter was represented by the slope of calibration curve in the linear region measured for each modality. A calibration curve (in the linear region) based on five dosimeters (four irradiated and one background) was obtained for each photon and electron energy and different repetition rates. Dosimeter sensitivity dependence on energy was studied for 4, 6, and 18 MV x-ray photons and for nominal electron energies 9, 12, 16, and 20 MeV. Dosimeter sensitivity dependence on mean dose rate was separately studied for electron and photon beams with the use of repetition rates 80, 160, 240, 320, and 400 MU min(-1). Evaluation of dosimeters was performed on Siemens MAGNETOM EXPERT 1T scanner in the head coil. A multiecho sequence with 16 equidistant echoes was used for the evaluation of irradiated polymer-gel dosimeters. The parameters of the sequence were as follows: TR 2000 ms, TE 22.5-360.0 ms, slice thickness 5 mm, FOV 255 mm, one acquisition. There was observed a trend in polymer-gel dosimeter sensitivity dependence on the quality index of high energy x-ray beams used and on mean electron energy absorbed in the center of the dosimeter. Polymer-gel dosimeter sensitivity was decreasing with increasing photon or electron energy. There was observed no trend in polymer-gel dosimeter sensitivity dependence on mean dose rate expressed as a repetition rate for both photon and electron beams.
本研究的目的是评估BANG-2聚合物凝胶剂量计的灵敏度对不同光子和电子能量的依赖性，以及对以标准临床使用的直线加速器的重复率表示的不同平均剂量率的依赖性。剂量计的灵敏度由针对每种模态在测量的线性区域内校准曲线的斜率表示。针对每个光子和电子能量以及不同的重复率，基于五个剂量计（四个受辐照的和一个本底的）获得了一条校准曲线（在线性区域内）。研究了4、6和18 MV的X射线光子以及标称电子能量为9、12、16和20 MeV时剂量计灵敏度对能量的依赖性。使用80、160、240、320和400 MU min⁻¹的重复率，分别研究了电子束和光子束中剂量计灵敏度对平均剂量率的依赖性。在西门子MAGNETOM EXPERT 1T扫描仪的头部线圈中对剂量计进行评估。使用具有16个等距回波的多回波序列来评估受辐照的聚合物凝胶剂量计。该序列的参数如下：TR 2000 ms，TE 22.5 - 360.0 ms，层厚5 mm，视野255 mm，一次采集。观察到聚合物凝胶剂量计的灵敏度对所使用的高能X射线束的质量指标以及剂量计中心吸收的平均电子能量存在依赖性趋势。聚合物凝胶剂量计的灵敏度随光子或电子能量的增加而降低。对于光子束和电子束，未观察到聚合物凝胶剂量计的灵敏度对以重复率表示的平均剂量率存在依赖性趋势。
