6MV医用直线电子加速器束流中心方向调整方法的研究

Investigation of Beam Alignment of 6 MV Medical Linear Accelerator

目的:在对6 MV低能电子直线加速器的加速管安装调试过程中,找出一种简单易行的束流调整方法,使束流调整后辐射野的均整度和方形X-辐射野的对称性指标符合国家标准GB15213-94《医用电子加速器性能及试验方法》的要求。方法:经过分析发现束流对称性(SYM)误差产生的原因分为两部分:束流的方向相对于辐射头轴线发生角度Δθ偏离和束流入射位置相对于辐射头轴线发生ΔX偏离,通过试验得到Δθ和ΔX对SYM数值变化的曲线,通过修正加速管连接法兰盘的平行度和同轴度对束流进行调整,并用水箱测量一定深度处辐射野内剂量的均匀性对调整结果进行检查和分析。结果和结论:使用5支加速管进行试验,束流调整前的对称性值在1.0%至2.9%之间,束流调整后的对称性值在0.8%~1.0%之间。达到了束流调整的目地,并且本方法在多台电子直线加速器上使用,结果证明了该方法的有效性和结果的精确性。

Objective: During installation and adjusting of accelerator tube for 6 MV medical linear accelerator(LINAC),an easy method was invented judged by parallelism and the coaxiality evaluation of the accelerating waveguide connection plate.Methods:The beam direction deviated the accelerator main axis Δθ and the deviation of the beam center ΔX were adjusted.The dose profiles got by the water tank scanner system were used to verify the revising by their flatness and symmetry.Results and Conclusions: The method has been used to adjusting the several accelerator tubes,and the results showed its effective and accuracy enough.