6～21MeV高能电子束深度剂量曲线测定方法的研究  

The Determination of Electron Beam Depth Dose Curve from Depth Ionization Curve at 6 to 21 MeV Nominal Energy

作　　者：任青[1,2] 夏兵[1,2] 李丹[1,2] 

机构地区：[1]中国医科大学第一临床学院放疗科 [2]沈阳军区总医院放疗科

出　　处：《中国医科大学学报》1999年第3期217-219,共3页Journal of China Medical University

摘　　要：目的：探讨电子束深度剂量曲线的测定方法，为临床选择电子束治疗方案提供物理基础。方法：在电子直线加速器上分别测量６、９、１２、１５、１８、２１ＭｅＶ六档标称能量，经φ３、φ４、φ５圆形及固定１０×１０ｃｍ限光筒后输出的电子束深度电离曲线。采用Ｅ０＝２．３３Ｒ５０，ｉ及Ｅ０＝０．８１８＋１．９３５Ｒ５０，ｉ＋０．０４０（Ｒ５０，ｉ）２分别计算平均入射能量Ｅ０，并推导出利用Ｓｗ，ａ、Ｐｕ或ＣＥ从百分深度电离量直接计算百分深度剂量的公式。结果：所引用二种Ｅ０计算公式的差异在２．１％之内，该差异对参考点剂量及深度剂量曲线几乎没有影响。通过对所获得深度剂量曲线与深度电离曲线的比较看到：其８５％峰值深度Ｒ８５，ｄ及半峰值深度Ｒ５０，ｄ均大于深度电离曲线上的对应值，且该差别随平均入射能量的增加而加大。结论：深度剂量曲线应在测得深度电离曲线后，经计算平均入射能量Ｅ０，查出对应深度的Ｓｗ，ａ、Ｐｕ或ＣＥ，进而由百分深度电离量求得。Objective: Our aim was to investigate a method for drawing the electron beam depth dose curve from depth ionization curve. Methods: We Measured the depth ionization curve from a Siemens Primus accelerator with 345 and 1010 cm applicators at a nominal energy of 6 to 21 MeV.The formula 0=2.33R50,i and 0=0.818+1.935R50,i+0.040(R50,i)2 were used to calculate the mean injection energy, respectively. We derived relative dose at a depth R from relative ionization by applying the conversation factors Sw,a( 0,R) Pu or CE( 0,R). Results: The difference of E0 derived from two formulas was within the range of 2.1%,which would have little influence on the determination of depth dose curve and the absorbed dose at reference depth. The depth Rmax,dwas higher or equal to Rmax,i.While depth R was higher than Rmax,d,the obtained depth dose curve was higher than depth ionization curve, and the difference between two curves became larger with an increase in depth R, also in mean injection energy. A reverse phenomen was observed while depth R was lower than Rmzx,d. Conclusion: The depth dose curve could be obtained from the depth ionization curve by the factors Sw,a( 0, R)Puor CE(0,R).

关 键 词：电子束剂量学 深度剂量曲线 深度电离曲线 

分 类 号：R815[医药卫生—放射医学] R144.1[医药卫生—临床医学]