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研究了医用直线加速器的主要部件对X射线能谱的影响。利用蒙特卡罗软件包EGSnrc/BEAMnrc针对Varian600C医用直线加速器,模拟完整及分别去除初级准直器、均整器和次级准直器条件下的相空间文件,通过相空间文件分析程序Beamdp对相空间文件进行分析,分别得到相应条件下的X射线能谱。均整器对能谱的影响非常大,对比于无均整器的情况,有均整器时,平均能量上升了48.9%;但初级准直器、次级准直器对能谱的影响小,平均能量的变化小于1%。在射野内,对比于无均整器的情况,有均整器时,能量注量降低了52.4%,但其空间分布变均匀,非平坦度从15.09%变为1.82%;对比于无初级准直器的情况,有初级准直器时,能量注量上升了1.58%;而对比于无次级准直器的情况,有次级准直器时,能量注量下降了2.00%。均整器对X射线的能谱的影响起主要作用,它能够使X射线的平均能量上升和射野内能量注量的分布变均匀。初级准直器对X射线能谱影响小但对X射线的散射不可忽略,而次级准直器对X射线能谱的影响小而且对X射线的散射作用可以忽略,这些结果对加速器X射线束流模型的建立有一定的参考意义。
The influence of the main components of the medical linear accelerator on the X-ray energy spectrum was studied. The Monte Carlo software package EGSnrc / BEAMnrc was used to simulate the Varian600C medical linear accelerator and to simulate the phase space file under the condition of primary collimator, homogenizer and secondary collimator. Through the phase file analysis program Beamdp, Documents were analyzed, respectively, under the corresponding conditions of X-ray energy spectrum. The average energy of the homogenizer has a great influence on the energy spectrum. Compared with the non-homogenizer, the average energy increases by 48.9% when there is a homogenizer. However, the effects of the primary and secondary collimators on the energy spectrum are small and the average energy Less than 1% change. In the field of radiation, compared with the case of no homogenizer, when the homogenizer is equipped, the fluence of the energy reducer is reduced by 52.4%, but the spatial distribution becomes even and the non-flatness changes from 15.09% to 1.82%. Compared with the non-primary collimator In the case of a primary collimator, the energy fluence increased by 1.58%, whereas in the case of a secondary collimator, the fluence decreased by 2.00% with the secondary collimator. The homogenizer plays a major role in the energy spectrum of X-ray. It can make the average energy of X-ray rise and the distribution of energy fluence in the field uniform. The primary collimator has a small effect on the energy spectrum of X-ray but does not scatter the X-ray. The secondary collimator has little effect on X-ray spectrum and has negligible effect on X-ray scattering. The establishment of the beam model has a certain reference value.