Algorithm and performance of a clinical IMRT beam-angle optimization system
Algorithm and performance of a clinical IMRT beam-angle optimization system
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DOI：
10.1088/0031-9155/48/19/007
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发表时间：
2003-10-07
影响因子：
3.5
通讯作者：
Mohan, R
中科院分区：
文献类型：
--
作者：
Djajaputra, D;Wu, QW;Mohan, R
本文介绍了该算法，并检查了调强放射治疗（IMRT）射束角度优化（BAO）系统的性能。在该算法中，使用快速模拟退火（FSA）算法从一组预定义的方向中选择连续的波束角度组。对每个生成的射束集合执行IMRT射束轮廓优化。IMRT优化加速使用一个快速的剂量计算方法，利用预先计算的剂量核。在开始FSA算法之前，为每个预定义波束构建紧凑核。然后在快速剂量计算引擎中使用这些内核执行BAO期间的IMRT优化。该技术允许比使用卷积剂量计算引擎的类似优化快两个数量级以上地执行IMRT优化。IMRT系统中存在的任何类型的优化标准都可以用于该BAO系统中。本研究使用基于临床相关剂量体积（DV）标准的目标函数。这便于BAO计划和由计划器产生的相应计划之间的比较，因为后者通常使用基于DV的目标函数进行优化。一个简单的前列腺病例和一个复杂的头颈部（HN）病例被用来评估这种BAO方法的有效性和性能。对于前列腺的情况下，我们比较了三个，五个和七个共面波束的BAO结果与相同数量的等间距共面波束。对于HN的情况下，我们比较了七个和九个非共面光束与九个等间距共面光束的BAO结果。在每种情况下，允许BAO算法搜索多达1000个不同的波束集。在400 MHz工作站上，前列腺患者BAO完成时间为1-2 h，头颈部患者BAO完成时间为13-17 h。没有先验波束选择标准已被用于实现这一性能。在前列腺和头部和颈部的情况下，BAO被证明是提供计划质量的改善超过了等间距的光束。DV为基础的目标函数的使用也使我们能够研究的依赖BAO的DV标准中使用的优化提供的计划质量的改善。我们发现，BAO是特别有用的情况下，需要强大的DV标准。该BAO系统的主要优点是其速度快，并可直接连接到临床IMRT系统。
This paper describes the algorithm and examines the performance of an intensity-modulated radiation therapy (IMRT) beam-angle optimization (BAO) system. In this algorithm successive sets of beam angles are selected from a set of predefined directions using a fast simulated annealing (FSA) algorithm. An IMRT beam-profile optimization is performed on each generated set of beams. The IMRT optimization is accelerated by using a fast dose calculation method that utilizes a precomputed dose kernel. A compact kernel is constructed for each of the predefined beams prior to starting the FSA algorithm. The IMRT optimizations during the BAO are then performed using these kernels in a fast dose calculation engine. This technique allows the IMRT optimization to be performed more than two orders of magnitude faster than a similar optimization that uses a convolution dose calculation engine. Any type of optimization criterion present in the IMRT system can be used in this BAO system. An objective function based on clinically-relevant dose-volume (DV) criteria is used in this study. This facilitates the comparison between a BAO plan and the corresponding plan produced by a planner since the latter is usually optimized using a DV-based objective function. A simple prostate case and a complex head-and-neck (HN) case were used to evaluate the usefulness and performance of this BAO method. For the prostate case we compared the BAO results for three, five and seven coplanar beams with those of the same number of equispaced coplanar beams. For the HN case we compare the BAO results for seven and nine non-coplanar beams with that for nine equispaced coplanar beams. In each case the BAO algorithm was allowed to search up to 1000 different sets of beams. The BAO for the prostate cases were finished in about 1-2 h on a moderate 400 MHz workstation while that for the head-and-neck cases were completed in 13-17 h on a 750 MHz machine. No a priori beam-selection criteria have been used in achieving this performance. In both the prostate and the head-and-neck cases, BAO is shown to provide improvements in plan quality over that of the equispaced beams. The use of DV-based objective function also allows us to study the dependence of the improvement of plan quality offered by BAO on the DV criteria used in the optimization. We found that BAO is especially useful for cases that require strong DV criteria. The main advantages of this BAO system are its speed and its direct link to a clinical IMRT system.