Automatic beam angle selection in IMRT planning using genetic algorithm
Automatic beam angle selection in IMRT planning using genetic algorithm
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DOI：
10.1088/0031-9155/49/10/007
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发表时间：
2004-05-21
影响因子：
3.5
通讯作者：
Yao, DZ
中科院分区：
文献类型：
--
作者：
Li, YJ;Yao, J;Yao, DZ
目前，外部射束放射治疗中合适的射束角度的选择通常基于人类规划者的经验。自动选择射束角度的要求在调强放射治疗（IMRT）中尤为突出，与适形放射治疗相比，希望使用更少数量的调制射束。许多研究人员已经证明，选择合适的波束角度对于波束数量较少（小于或等于5）的方案最有价值。本文提出了一种有效的方法来研究如何通过选择合适的共面光束角度来改善剂量分布。在我们的自动光束角选择（ABAS）算法中，最佳共面光束角对应于使用这组候选光束的强度调制图计算的剂量分布的最低目标函数值。由于问题的复杂性和涉及的搜索空间较大，波束角度的选择和强度图的优化被视为两个独立的过程并迭代实施。结合免疫操作的遗传算法（GA）用于选择合适的光束角度，并且使用共轭梯度（CG）方法基于基于剂量的目标函数快速优化每个选定光束组合的强度图。采用基于笔形束的三维 (3D) 全散射卷积 (FSC) 算法进行剂量计算。使用两个具有明显最佳光束角的模拟案例来验证该技术的有效性，并使用一个更复杂的模拟前列腺肿瘤的案例和两个临床案例来测试ABAS的效率。结果表明，ABAS 有效且高效，可以在临床可接受的计算时间内改善剂量分布。
The selection of suitable beam angles in external beam radiotherapy is at present generally based upon the experience of the human planner. The requirement to automatically select beam angles is particularly highlighted in intensity-modulated radiation therapy (IMRT), in which a smaller number of modulated beams is hoped to be used, in comparison with conformal radiotherapy. It has been proved by many researchers that the selection of suitable beam angles is most valuable for a plan with a small number of beams (less than or equal to 5). In this paper an efficient method is presented to investigate how to improve the dose distributions by selecting suitable coplanar beam angles. In our automatic beam angle selection (ABAS) algorithm, the optimal coplanar beam angles correspond to the lowest objective function value of the dose distributions calculated using the intensity-modulated maps of this group of candidate beams. Due to the complexity of the problem and the large search space involved, the selection of beam angles and the optimization of intensity maps are treated as two separate processes and implemented iteratively. A genetic algorithm (GA) incorporated with an immunity operation is used to select suitable beam angles, and a conjugate gradient (CG) method is used to quickly optimize intensity maps for each selected beam combination based on a dose-based objective function. A pencil-beam-based three-dimensional (3D) full scatter convolution (FSC) algorithm is employed for the dose calculation. Two simulated cases with obvious optimal beam angles are used to verify the validity of the presented technique, and a more complicated case simulating a prostate tumour and two clinical cases are employed to test the efficiency of ABAS. The results show that ABAS is valid and efficient and can improve the dose distributions within a clinically acceptable computation time.