目的:最近的全球电子束参考剂量测定标准测量包括国际原子能机构(IAEA)技术报告系列(TRS)-398和医学物理学家协会(AAPM)任务组(TG)-51协议。Muiretal.修改了基于AAPMTG-51的电子束校准校准方法。他们发现在低能量下使用圆柱形腔室给出了可接受的结果。在这项研究中,我们提出并报告了基于IAEATRS-398的电子束校准,这是世界范围内的标准参考剂量测定协议。
方法:这项工作是在6、8、10、12和15MeV的能量下进行的。电子束由ElektraSynergy平台和VersaHD线性加速器产生。使用PTW30013,IBACC13,ExradinA1Sl测量电荷读数,和ExradinA11室连接到静电计。剂量计算使用先前工作中使用更新的kQ${k_Q}$因子的电子束修正校准方程。电子束对水的吸收剂量以每监视器单位的剂量(cGy/MU)表示。因此,我们使用改进的校准方法与TRS-398比较了每监测单位剂量(D/MU)的计算.
结果:在这项工作中,通过在所有能量束中应用圆柱形腔室并使用更新的kQ${k_Q}$因子,我们成功地实现了基于TRS-398的改进的电子束校准。对于圆柱形腔室,TRS-398(Dw)的原始和修改后的校准协议之间的吸收剂量与水的比率在ElektaSynergy平台上为1.002,在VersaHD上为1.000,而对于平行板腔室,在ElektaSynergy平台上为1.013,在VersaHD上为1.014。基于这些结果,圆柱形和平行板室仍在TRS-398协议允许的公差范围内,±2%。因此,基于TRS-398的修正校准给出了可接受的结果并且更易于临床使用。
OBJECTIVE: The recently worldwide standard measurement of electron beam reference dosimetry include the International Atomic Energy Agency (IAEA) Technical Report Series (TRS)-398 and Association of Physicists in Medicine (AAPM) Task Group (TG)-51 protocols. Muir et al. have modified calibration methods for electron beam calibration based on AAPM TG-51. They found that the use of cylindrical chambers at low energy gave acceptable results. In this study, we propose and report a modified calibration for electron beam based on IAEA TRS-398, the standard reference dosimetry protocol worldwide.
METHODS: This work was carried out with energies of 6, 8, 10, 12, and 15 MeV. The electron beam is generated from Elektra Synergy Platform and Versa HD linear accelerator. The charge readings were measured with PTW 30013, IBA CC13, Exradin A1Sl, and Exradin A11 chambers connected to the electrometer. The dose calculation uses an equation of modified calibration for electron beam using the updated k Q ${k_Q}$ factor in previous work. The absorbed dose to water for electron beam is expressed in dose per monitor unit (cGy/MU). Thus, we compared dose per monitor unit (D/MU) calculation using a modified calibration to TRS-398.
RESULTS: In this work, we have succeeded in implementing the modified calibration of electron beam based on TRS-398 by applying a cylindrical chamber in all energy beams and using the updated k Q ${k_Q}$ factor. The ratio of the absorbed dose to water between original and modified calibration protocols of TRS-398 (Dw ) for the cylindrical chamber was 1.002 on the Elekta Synergy Platform and 1.000 on the Versa HD while for the parallel-plate chamber it was 1.013 on the Elekta Synergy Platform and 1.014 on the Versa HD. Based on these results, both the cylindrical and parallel-plate chambers are still within the tolerance limit allowed by the TRS-398 protocol, which is ±2%. Therefore, modified calibration based on TRS-398 gives acceptable results and is simpler to use clinically.