电子束矩形野输出因子等效转换方法的对比实验研究

Experimental study on the accuracy of output factor calculation for rectangular inserts of electron beams

目的 比较方根式、一维式和面积周长比 3种方法计算的电子束矩形照射野输出因子的精确性和可行性。方法 用电离室法对不同大小限光筒不同能量下 8个特定矩形照射野输出因子实测和用 3种方法计算 ,比较此 3种方法与实测值偏差。结果 (1 )同一能量下 ,面积周长比法偏差较大 ,一维式和方根式偏差较小 ;(2 )电子束限光筒大小、射线能量和矩形照射野大小对 3种方法计算的矩形照射野输出因子有一定影响。结论 面积周长比法计算矩形照射野输出因子偏差较大 ,建议不予采用。一维式和方根式法精度较高 ,一维式法优于方根式法 。

Objective To compare the accuracy of output factor calculation for rectangular inserts of electron beams by using three kinds of algorisms: square root, one dimensional formula and area periphery ration. Methods The differences between the values of output factor calculated by these three algorithms mentioned above and the results measured by ionization chamber for seven rectangular inserts were compared. Results When beam energy was fixed, the difference between calculated and measured output factors was larger for area periphery ration algorithm than that of the square root or one dimensional formula algorithms. The electron cone size, beam energy and rectangular inserts size all had some effect on the value of output factor calculated by the three algorithms. Conclusions The area periphery ration algorithm is not recommended for clinical use because of its great deviation. One dimensional formula and square root algorisms possess a good accuracy. One dimensional formula is superior to square root algorithm, but square root algorithm is more practical for clinical use.