多丝电离室(DAVID)系统对加速器射束的影响

摘要

Abjective: Through measuring the parameters of the accelerator beams under two conditions of uninstalled and installed DAVID system,to analyze DAVID system's influence on the beams. Methods: We chosed the Siemens ARTISTE Linear Accelerator which was allocated with a 160 MLC multi-leaf collimator, and the 6 MV X-ray was used. The model number of the multi-wire ionization chamber was T34084. Utilizing the equipments like 3D water tank and semiconductor detector to measure PDD, profile, TPR2010 and the absorbed dose underwater 5 cm under the conditions of uninstalled and installed DAVID system, we analyzed DAVID system's influence on the PDD, flatness, symmetry and actinogen of accelerator beams, and calculated the attenuation coefficient of DAVID system. Results: Under the two conditions of uninstalled and installed DAVID system, the R100 deviation of the three fields (5 cm×5 cm 、10 cm×10 cm and 20 cm×20 cm) lay between 0.6 mm ～1.3 mm, R80 deviation of them lay between 0.13 mm～0.66 mm, and R50 deviation lay between 0.38 mm～1.12 mm. The R100, R80, and R50 deviation of the fields of 40 cmx40 cm were 3.12 mm, 3.31 mm and 2.04 mm; The QI deviations were 0.0020, 0.0045, 0.0101, and 0.0061; The flatness deviation in the x and y direction was between 0.10%～0.58%; The symmetry deviation lay between 0.04%～0.26%; And the TPR2010 deviation was 0.002. The beams went across DAVID system and attenuated 7.67% of the dose. Conclusions: The comprehensive structure and making materials of DAVID system have little effect on the PDD, symmetry, flatness, and TPR2010 of the 6 MV X-ray beams, but the beams attenuate the dose when going across DAVID system.%目的:通过测量未安装和已安装DAVID系统两种情况下加速器射束的参数,分析DAVID系统对射束的影响.方法:西门子ARTISTE直线加速器,配备160叶多叶光栅,选择6 MV的X线.多丝电离室(DAVID),型号为T34084.利用三维水箱、半导体探测器等仪器测量未安装和已安装DAVID系统两种条件下PDD、profile、TPR20/10和水下5 cm吸收剂量,分析DAVID系统对加速器射线束PDD、平坦度、对称性、射线质的影响,并计算出DAVID系统的衰减系数.结果:无和有DAVID两种条件下,5 cm×5 cm、10 cm×10 cm和20 cm×20 cm三个射野R100偏差在0.6 mm～1.3 mm,R80偏差在0.13 mm～0.66 mm,R50偏差在0.38 mm～1.12 mm;40 cm×40 cm的射野R100、R80和R50的偏差分别为3.12 mm、3.31mm和2.04 mm; QI的偏差分别为0.0020、0.0045、0.0101、0.0061;x和y方向平坦度偏差在0.10％～0.58％,对称性偏差在0.04％～0.26％；TPR20/10的偏差0.002.射线穿过DAVID,使剂量衰减了7.67％.结论:DAVID系统的复杂结构和材料对6MV的X射线束的PDD、对称性、平坦度和TPR20/10影响甚微,最主要的是射线经过DAVID系统造成了剂量的衰减.