中文摘要：

放射治疗计划中有关射野射束元初始强度分布优化和子野（适形野）权重优化的问题，如果充分考虑散射和约束条件的影响，将会带来一定的优化困难。为此，本文提出了基于体元分布的目标剂量的两步法解决方案，首先是只考虑约束和给定的计划靶区处方剂量而完全不考虑散射的影响优化出剂量分布，该剂量分布称之为基于体元分布的目标剂量。然后采用这个满足约束条件的目标剂量，在只考虑散射而不考虑约束条件限制的情况下进行强度（权重）的最终优化。从而把一个有约束的问题转变为了一个不含约束的问题。结果显示，基于体元分布的目标剂量应用于射野射束元初始强度分布的优化、子野（适形野）权重的优化以及剂量分布之间的相对比较具有较好的效果。

英文摘要：

Considering combined effect of phton scattering in phantom and constraint conditions for organ（s） at risk, it is difficult to optimize the intensity of beam profiles and weight of segments or conformal fields during the process of radiotherapy planning design. In this paper, a two-step method is proposed. First, the prescription dose of PTV, constraint conditions of OAR and dose matrix without considering the scattering in phantom are used to optimize the dose distribution which is called the voxel-by-voxel-based objective dose. With the new objective dose and consider- ing the scattering, the intensity or the weight could be well optimized. The second step is an optimization process without constraint conditions and the optimization can be Finished rapidly. Because the new objective dose satisfies the constraint condition in Step 1 and the dose matrix is calculated by accurately dose calculation algorithm in Step 2, the results are satisfying and credible, as verified by applying the method to a typical example.