Simulations to design an online motion compensation system for scanned particle beams
Simulations to design an online motion compensation system for scanned particle beams
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DOI：
10.1088/0031-9155/51/14/016
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发表时间：
2006-07-21
影响因子：
3.5
通讯作者：
Kraft, Gerhard
中科院分区：
文献类型：
--
作者：
Groezinger, Sven Oliver;Rietzel, Eike;Kraft, Gerhard
呼吸诱导的靶区运动是调强放射治疗中的一个主要问题。射束分段连续输送以形成总剂量分布。在存在运动的情况下，来自不同段的剂量沉积之间的空间关系将丢失。通常，这会导致过量和剂量不足。除了从光子治疗已知的目标运动和动态射束递送之间的这种相互作用效应之外，内部密度的变化对强度调制带电粒子治疗的递送剂量具有影响。在这项研究中，我们分析了光栅扫描的碳离子束和目标运动之间的相互作用效果。此外，在线运动策略的潜力进行了评估，在几个模拟。使用临床治疗计划软件的扩展版本计算有和无运动补偿的移动靶的剂量分布。对于运动补偿，每个单独的离子笔束在横向和纵向上跟踪计划的目标位置。模拟目标平移和旋转，包括内部密度的变化。模拟呼吸的靶运动导致递送剂量分布的严重退化。例如，对于+/- 15 mm的运动幅度，只有47%的靶体积接收了80%的计划剂量。由此产生的剂量分布的不可预测性证明了不同的运动参数。另一方面，运动补偿允许的剂量分布的移动目标相比，静态目标。即使是有限的补偿精度（标准偏差类似于2 mm），引入模拟实时目标跟踪的可能限制，导致剂量均匀性损失小于3%。
Respiration-induced target motion is a major problem in intensity-modulated radiation therapy. Beam segments are delivered serially to form the total dose distribution. In the presence of motion, the spatial relation between dose deposition from different segments will be lost. Usually, this results in over-and underdosage. Besides such interplay effects between target motion and dynamic beam delivery as known from photon therapy, changes in internal density have an impact on delivered dose for intensity-modulated charged particle therapy. In this study, we have analysed interplay effects between raster scanned carbon ion beams and target motion. Furthermore, the potential of an online motion strategy was assessed in several simulations. An extended version of the clinical treatment planning software was used to calculate dose distributions to moving targets with and without motion compensation. For motion compensation, each individual ion pencil beam tracked the planned target position in the lateral aswell as longitudinal direction. Target translations and rotations, including changes in internal density, were simulated. Target motion simulating breathing resulted in severe degradation of delivered dose distributions. For example, for motion amplitudes of +/- 15 mm, only 47% of the target volume received 80% of the planned dose. Unpredictability of resulting dose distributions was demonstrated by varying motion parameters. On the other hand, motion compensation allowed for dose distributions for moving targets comparable to those for static targets. Even limited compensation precision (standard deviation similar to 2 mm), introduced to simulate possible limitations of real-time target tracking, resulted in less than 3% loss in dose homogeneity.