Abstract：Objective To explore the impact of field size variation of medical electronic linear accelerator on X-ray energy dose,
spectrum and mean energy, to provide theoretical basis for accelerator spectrum measurement as a quality control method for
field operation accuracy. Methods The EGSnrc program based on Monte Carlo algorithm was used for ionizing radiation transfer
simulation, and BEAMnrc was used to build the head model of the Varian TrueBeam series accelerator, and the square field was
set from 1 cm×1 cm to 10 cm×10 cm. BEAMdp was used to call the phase space file generated by its calculation to analyze the
results of energy fluence, energy spectrum and mean energy. Results The size of the field had a great influence on the energy fluence
and spectrum structure. With the same energy, the larger the field, the higher the general peak value of the injection. In the selected
field, the maximum energy difference was 98.9%, and the maximum energy spectrum difference was 99.0%. Under the flattening
filter (FF) mode, the energy range of high injection volume was 0.5~1.2 MeV, and the peak was about 0.33 MeV. The energy range
of the high injection volume was 0.3~1.0 MeV and the peak was about 0.26 MeV under the flattening filter free (FFF) mode. At the
same time, the impact of field size on the average energy was not obvious, FF mode was about 1.4 MeV, FFF mode was about 1.2 MeV.
Conclusion The energy fluence and energy spectrum of different fields of the medical electron linear accelerator have certain
specificity, and the analysis of the energy fluence andenergy spectrum can be used as an auxiliary means to judge the accuracy of the
accelerator field operation.
陈兴强，黄顺平，肖杨，向君昭. 医用电子直线加速器射野能谱特性研究[J]. 中国医疗设备, 2023, 38(7): 80-85.
CHEN Xingqiang, HUANG Shunping, XIAO Yang, XIANG Junzhao. Research on the Characteristics of the Radiation Spectral of the Medical Linear Accelerator. China Medical Devices, 2023, 38(7): 80-85.
