IMRT dose shaping with regionally variable penalty scheme
IMRT dose shaping with regionally variable penalty scheme
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DOI：
10.1118/1.1556610
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发表时间：
2003-04-01
期刊：
影响因子：
3.8
通讯作者：
Xing, L
中科院分区：
文献类型：
--
作者：
Cotrutz, C;Xing, L
目前可用的逆计划系统的一个众所周知的缺陷是难以微调最终剂量分布。在实践中，在计划靶体积或有危险的器官中，仅仅几个不满意的区域就会阻止强度调制放射治疗（IMRT）计划在临床上被接受，这并不罕见。这项工作的目的是介绍一种机制，控制区域剂量后的常规IMRT计划，并证明其临床效用。在目标函数中引入了两类重要因子来模拟不同临床目标的权衡。第一个是传统的结构相关重要因子，它量化了基础结构的权衡。第二种类型是体素相关的重要性因子，它“调节”结构中不同体素的重要性。计划分两个主要步骤进行。首先执行传统的逆规划，其中以试错方式确定与结构相关的重要因素。下一阶段的规划涉及微调区域剂量，以满足具体的临床需要。为了实现这一目标，需要修改剂量的体素可以在等剂量布局或相应的剂量-体积直方图（DVH）曲线上以图形方式确定。然后调整这些体素的重要性值，以增加/减少相应区域的惩罚。该技术应用于两个临床病例。发现肿瘤热点和临界结构最大剂量都可以通过改变区域惩罚来控制。一到三个试验就足以使传统的最佳剂量分布调整到符合临床期望。因此，引入体素相关的惩罚方案为IMRT剂量分布的绘制和雕刻提供了有效的手段。(C) 2003年美国医学物理学家协会。
A commonly known deficiency of currently available inverse planning systems is the difficulty in fine-tuning the final dose distribution. In practice, it is not uncommon that just a few unsatisfactory regions in the planning target volume or an organ at risk prevent an intensity modulated radiation therapy (IMRT) plan from being clinically acceptable. The purpose of this work is to introduce a mechanism for controlling the regional doses after a conventional IMRT plan is obtained and to demonstrate its clinical utility. Two types of importance factors are introduced in the objective function to model the tradeoffs of different clinical objectives. The first is the conventional structure-dependent importance factor, which quantifies the interstructure tradeoff. The second type is the voxel-dependent importance factor which "modulates" the importance of different voxels within a structure. The planning proceeds in two major steps. First a conventional inverse planning is performed, where the structure-dependent importance factors are determined in a trial-and-error fashion. The next level of planning involves fine-tuning the regional doses to meet specific clinical requirements. To achieve this, the voxels where doses need to be modified are identified either graphically on the isodose layouts, or on the corresponding dose-volume histogram (DVH) curves. The importance value of these voxels is then adjusted to increase/decrease the penalty at the corresponding regions. The technique is applied to two clinical cases. It was found that both tumor hot spots and critical structure maximal doses can be easily controlled by varying the regional penalty. One to three trials were sufficient for the conventionally optimized dose distributions to be adjusted to meet clinical expectation. Thus introducing the voxel-dependent penalty scheme provides an effective means for IMRT dose distributions painting and sculpting. (C) 2003 American Association of Physicists in Medicine.