高能光子相对输出因子的测量与分析  

Measurement and Analysis of Relative Output Factor for High Energy Photons

作　　者：蔡汉飞[1,2] 裴元吉[1] 沈学明[2] 李贵[1,3] 

机构地区：[1]中国科学技术大学核科学技术学院,安徽合肥230027 [2]蚌埠医学院第一附属医院,安徽蚌埠233004 [3]中国科学院等离子体物理研究所,安徽合肥230031

出　　处：《中国医学物理学杂志》2009年第4期1273-1276,1290,共5页Chinese Journal of Medical Physics

摘　　要：目的:研究不同探测器和使用方法对高能光子相对输出因子测量结果的影响。方法:分别使用PTW30006、PTW31006电离室和GAFCHROMIC EBT胶片测量ELEKTA Precise加速器光子相对输出因子。结果:照射野大于等于4cm×4cm时,胶片和PTW30006电离室测量结果相对偏差小于±1.0%。归一到5cm×5cm照射野时,边长为2cm、3cm、4cm、6cm和10cm方野,胶片和PTW31006电离室测量结果相对偏差分别为2.2%、0.6%、0.3%、0.3%和-1.7%。随照射面积增大,PTW31006与PTW30006电离室测量结果偏离程度不断加大,40cm×40cm时偏高约8.2%。结论:合理选择胶片数字化设备和使用方法,GAFCHROMIC EBT胶片可以用于所有照射野相对输出因子的测量或作为电离室法测量结果的有益补充和参考。Objective： It was to explore the influences on results of relative output factor （ROF） measurement caused by different detectors and methods, and to evaluate the feasibility and reliability of GAFCHROMIC EBT film used for measuring ROFs of high energy photons. Methods： PTW chambers （type 30006 and 31006） and GAFCHROMIC EBT film were applied to measure ROFs for ELEKTA Precise accelerator, and to make a comparison among them. Results： For GAFCHROMIC EBT film, the expanded relative uncertainty of dose measurement was less than 2.6% at a level of 95% confidence. For field size greater than or equal to 4 cm× 4 cm, the deviations of ROFs measured by the film and the PTW 30006 chamber were less than ±1.0%. When normalized to 5 cm × 5 cm field at the same depth, the deviations of ROFs measured by the film and the FTW 31006 chamber were 2.2%, 0.6%, 0.3%, 0.3% and -1.7% for square fields of 2 cm, 3 cm, 4 cm, 6 cm and 10 cm width respectively. Again, the result was shown that the deviations of ROFs measured by the PTW 31006 chamber and the PTW 30006 chamber increased when field size increased, where the maximum deviation was 8.2% for 6 MV X-ray and 40 cm × 40 cm field size. Conclusions： Results of ROF measured by different detectors and methods indicate that they may have significantly different measured results, and hence both the detectors and methods should be carefully investigated before they are used. By choosing film digitizer and methods reasonably, the GAFCHROMIC EBT film is good for the ROF measurement, or a useful supplement and reference to the chamber.

关 键 词：相对输出因子 吸收剂量 电离室 GAFCHROMIC EBT胶片 

分 类 号：R144.1[医药卫生—公共卫生与预防医学]