医用直线加速器矩形野散射因子的简便计算方法

Simple Calculation Method to Scatter Factor to the Rectangular Field of Linear Accelerator

目的 建立一种适合于临床应用的加速器散射因子 Sc.p的简便计算方法。方法 ( 1 )通过测量方野的散射因子 ,建立方野散射因子与射野边长的拟合公式 ;( 2 )利用 Kim的经验公式 ,计算矩形野的等效方边长 ;( 3)应用已拟合的方野散射因子公式计算矩形野的散射因子 ,并与矩形野的测量结果进行比较。结果 采用该方法计算医用加速器散射因子的最大误差在 0 .5%以下 ,而采用面积 -周长比原理确定的等效方边长 ,最大误差达到 3%左右。结论 该方法可用于简便快速地确定方野和矩形野的散射因子 ,精确度高 。

Objective To design up a simple method to calculate the scatter factor Sc,p of X ray linear accelerator,which can be implemented in clinical works.Methods Firstly,the scatter factors of square fields have been measured and the relation between the scatter factor and the length of fields has been made;Secondly,the equivalent square fields of rectangular fields are calculated according to the formula established by kim. The scatter factors of rectangular fields are determined according to the relation between the scatter factor and the length of fields,and compared with the measured Sc,p value for rectangular fields.Results The most error is lower than 0.5% to apply the method to calculate the scatter factors,however the most error is about 3% according to the principle of area-linear rate. Conclusion The scatter factors can be determined quickly and correctly,and can be suitable for clinical daily practice.