利用EGS4程序对复合耙的初步研究

为了使X射线能谱硬化以利于放射治疗，国外中、高能医用加速器较多采用复合靶技术。本工作利用EGS4程序对复合靶进行了初步研究，模拟了不同能量电子入射到复合靶所产生光子和电子的剂量分布。计算表明：采用结构为2mm厚钨靶片，再加上3mm厚的铜或10mm厚的石墨作过滤片的复合靶后，电子剂量降为仅用钨靶剂量的10％，光子剂量仍保持最佳值，且光子的平均能量得到提高。此复合靶达到硬化X射线和降低电子污染的预期目标。

PRIMARY STUDIES ON A COMPOSITE TARGET BY EGS4 CODE

The technology of composite targets is applied in many mid- and high-energy band medical accelerators to harden the energy spectrum of X rays for radiotherapy treatment. Primary studies of composite targets by EGS4 code are presented. The dose distributions of electrons and X ray are given by simulation computation. After using composite targets that are made up of 2 mm tungsten and a filter of 3 mm copper or 10 mm graphite, in contrast to simple targets, the dose of electrons reduce to 10%, the dose of X rays keeps optimal, and the average energy of X rays rises. Composite targets can be used to harden X rays and reduce electron pollution.