Tumor trailing strategy for intensity-modulated radiation therapy of moving targets
Tumor trailing strategy for intensity-modulated radiation therapy of moving targets
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DOI：
10.1118/1.2900108
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发表时间：
2008-05-01
期刊：
影响因子：
3.8
通讯作者：
Bortfeld, Thomas
中科院分区：
文献类型：
--
作者：
Trofimov, Alexei;Vrancic, Christian;Bortfeld, Thomas
在癌症的放射治疗过程期间的内部器官运动影响递送剂量的分布，并且通常降低其对靶体积的适形性。先前提出的旨在减轻强度调制放射治疗（IMRT）中内部运动的影响的方法包括靶边缘的扩展、运动相关递送（例如，呼吸门控、肿瘤跟踪），以及采用运动的概率描述的自适应治疗计划优化。我们描述并测试了肿瘤跟踪策略，该策略利用了运动自适应治疗计划和交付方法的协同作用。我们将（刚性）目标运动视为相对快的循环分量（例如，呼吸的）和缓慢的非周期性趋势（例如，呼气基线的漂移）。在跟踪方法中，这两个运动分量被解耦并单独处理。采用实时运动监控来识别“慢”换档，然后通过应用设置调整来校正。输送并不精确地跟踪目标位置，而是由于移位发生、被可靠地检测到以及随后被校正之间的时间延迟而跟踪系统趋势。利用鲁棒的运动自适应治疗规划来考虑“快速”循环运动，其允许运动参数的可变性（例如，潮气量的平均值和极值、呼吸的可变周期和呼气持续时间）。门控调强放射治疗的运动替代数据用于提供运动自适应规划的概率分布数据，并用于测试识别运动特征系统趋势的算法。在临床直线加速器上将样品IMRT场输送到可编程移动体模。剂量测量进行了商业二维离子室阵列。结果表明，通过减少分次内运动变异性，拖尾策略增强了运动自适应规划方法的相关性和适用性，并提高了在存在不规则运动的情况下对靶的输送剂量的适形性。跟踪策略可以应用于延迟门控治疗，其中对慢动作的校正可以增加占空比，而稳健的概率规划可以改善门控窗口内的剩余运动的管理。类似地，拖尾可以改善对表现出可检测的低幅度的目标运动的患者的治疗中的剂量适形性，这被认为不足以提供使用经门控治疗的临床指征（例如，小于10 mm的峰-峰运动）。实施肿瘤跟踪的机械限制不如实时跟踪的严格，并且相同的技术可以用于两者。(C)2008年美国医学物理学家协会。
Internal organ motion during the course of radiation therapy of cancer affects the distribution of the delivered dose and, generally, reduces its conformality to the targeted volume. Previously proposed approaches aimed at mitigating the effect of internal motion in intensity-modulated radiation therapy (IMRT) included expansion of the target margins, motion-correlated delivery (e.g., respiratory gating, tumor tracking), and adaptive treatment plan optimization employing a probabilistic description of motion. We describe and test the tumor trailing strategy, which utilizes the synergy of motion-adaptive treatment planning and delivery methods. We regard the (rigid) target motion as a superposition of a relatively fast cyclic component (e.g., respiratory) and slow aperiodic trends (e.g., the drift of exhalation baseline). In the trailing approach, these two components of motion are decoupled and dealt with separately. Real-time motion monitoring is employed to identify the "slow" shifts, which are then corrected by applying setup adjustments. The delivery does not track the target position exactly, but trails the systematic trend due to the delay between the time a shift occurs, is reliably detected, and, subsequently, corrected. The "fast" cyclic motion is accounted for with a robust motion-adaptive treatment planning, which allows for variability in motion parameters (e.g., mean and extrema of the tidal volume, variable period of respiration, and expiratory duration). Motion-surrogate data from gated IMRT treatments were used to provide probability distribution data for motion-adaptive planning and to test algorithms that identified systematic trends in the character of motion. Sample IMRT fields were delivered on a clinical linear accelerator to a programmable moving phantom. Dose measurements were performed with a commercial two-dimensional ion-chamber array. The results indicate that by reducing intrafractional motion variability, the trailing strategy enhances relevance and applicability of motion-adaptive planning methods, and improves conformality of the delivered dose to the target in the presence of irregular motion. Trailing strategy can be applied to respiratory-gated treatments, in which the correction for the slow motion can increase the duty cycle, while robust probabilistic planning can improve management of the residual motion within the gate window. Similarly, trailing may improve the dose conformality in treatment of patients who exhibit detectable target motion of low amplitude, which is considered insufficient to provide a clinical indication for the use of respiratory-gated treatment (e.g., peak-to-peak motion of less than 10 mm). The mechanical limitations of implementing tumor trailing are less rigorous than those of real-time tracking, and the same technology could be used for both. (C) 2008 American Association of Physicists in Medicine.