Yao J Y, Ranganathan G
Siemens Medical Systems Inc., Concord, California 94520.
Med Phys. 1994 Jun;21(6):809-16. doi: 10.1118/1.597326.
A wedge filter is one of the most commonly used beam modifying devices. The introduction of a wedge filter alters both the distribution of the primary photon fluence and the first and second scatter patterns. The effect of the wedge filter is normally expressed in terms of an exponential attenuation function that is used to modify the primary photon fluence. This paper describes a new three-dimensional (3-D) wedged field dose calculation algorithm. This algorithm automatically takes into account (1) the scatter distribution pattern correction due to the effect of wedge filters and (2) the fixed primary photon fluence correction, by utilizing a tissue maximum ratio table calculated from the measured percent depth dose of the wedge, a measured in-plane scan and a measured cross-plane scan of the largest rectangular wedge field size. As a result, the calculation accuracy achieved by this algorithm is better than the calculation accuracy achieved by other algorithms. The results show better than 1% accuracy of the wedge central axis percent depth dose calculation and better than 3% accuracy of the off-axis dose calculation when compared with measurements.
楔形滤过器是最常用的射束修正装置之一。楔形滤过器的引入会改变原发射线光子注量的分布以及首次和二次散射模式。楔形滤过器的效果通常用指数衰减函数来表示，该函数用于修正原发射线光子注量。本文描述了一种新的三维（3-D）楔形野剂量计算算法。该算法通过利用根据楔形野的测量深度剂量百分比、最大矩形楔形野尺寸的测量平面内扫描和测量横断面扫描计算得出的组织最大剂量比表，自动考虑（1）楔形滤过器效应引起的散射分布模式校正，以及（2）固定的原发射线光子注量校正。因此，该算法实现的计算精度优于其他算法。结果表明，与测量值相比，楔形野中心轴深度剂量计算的精度优于1%，离轴剂量计算的精度优于3%。
