Respiratory gated beam delivery cannot facilitate margin reduction, unless combined with respiratory correlated image guidance
Respiratory gated beam delivery cannot facilitate margin reduction, unless combined with respiratory correlated image guidance
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DOI：
10.1016/j.radonc.2007.10.038
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发表时间：
2008-01-01
影响因子：
5.7
通讯作者：
Boyer, Arthur L.
中科院分区：
文献类型：
--
作者：
Korreman, Stine S.;Juhler-Nottrup, Trine;Boyer, Arthur L.
目的/目标：在靶区随呼吸运动的放射治疗中，射束门控是减少靶区运动的一种手段。本研究的目的是评估的安全幅度的边缘减少呼吸门控beam delivery.Materials/Methods：这项研究是基于17例肺癌患者在不同的协议在Rigshospitalet和斯坦福大学癌症中心的数据。使用基于RPM系统（Varian Medical Systems）的设备收集外部光学标记和植入基准的呼吸曲线。共861条呼吸曲线代表了10例患者30个治疗疗程的外部测量值，7例患者在单次治疗中同步进行外部/内部测量。呼吸振幅（模拟指导）和外部/内部相移的变化通过实际值的扰动来模拟。变化通过标记位置分布的中位数和标准差（SD）来描述。将门控窗口（35%占空比）回顾性应用于每次会话的呼吸数据，模拟使用市售门控系统。中位数和Ss的门控数据进行了比较，ungated data，以评估潜在的利润reductions.Results：外部呼吸数据收集在整个治疗过程中显示SD从1.6到8.1毫米，主要部分来自基线变化。门控数据的SD为1.5 - 7.7 mm，平均减少0.3 mm（6%）。门控分布比非门控分布更偏，在少数情况下，即使没有应用边际减少，也会发现门控呼吸的边际缺失。规则化的呼吸振幅，以模拟教练并没有改变这些结果显着。模拟不同的相移之间的内部和外部呼吸信号显示，SD的门控分布是相同的，为ungated或更小，但中位数值显着移动。门控分布一般不能覆盖的利润率来自非门控数据，如果相移没有accountfor.Conclusions：利润率只能减少呼吸门控放射治疗，如果呼吸基线偏移和外部/内部运动相关性的变化占。单独的选通射束输送不能促进裕度减小。在最差情况下，必须增加裕度以适应呼吸的级分间变化。(C)2007爱思唯尔爱尔兰有限公司保留所有权利。
Purpose/objective: In radiotherapy of targets moving with respiration, beam gating is offered as a means of reducing the target motion. The purpose of this study is to evaluate the safe magnitude of margin reduction for respiratory gated beam delivery.Materials/methods: The study is based on data for 17 lung cancer patients in separate protocols at Rigshospitalet and Stanford Cancer Center. Respiratory curves for external optical markers and implanted fiducials were collected using equipment based on the RPM system (Varian Medical Systems). A total of 861 respiratory curves represented external measurements over 30 fraction treatment courses for 10 patients, and synchronous external/internal measurements in single sessions for seven patients.Variations in respiratory amplitude (simulated coaching) and external/internal phase shifts were simulated by perturbation with realistic values.Variations were described by medians and standard deviations (SDs) of position distributions of the markers. Gating windows (35% duty cycle) were retrospectively applied to the respiratory data for each session, mimicking the use of commercially available gating systems. Medians and Ss of gated data were compared to those of ungated data, to assess potential margin reductions.Results: External respiratory data collected over entire treatment courses showed SDs from 1.6 to 8.1 mm, the major part arising from baseline variations. The gated data had SDs from 1.5 to 7.7 mm, with a mean reduction of 0.3 mm (6%). Gated distributions were more skewed than ungated, and in a few cases a marginal miss of gated respiration would be found even if no margin reduction was applied. Regularization of breathing amplitude to simulate coaching did not alter these results significantly.Simulation of varying phase shifts between internal and external respiratory signals showed that the SDs of gated distributions were the same as for the ungated or smaller, but the median values were markedly shifted. The gated distributions could generally not be covered by margins derived from ungated data, if the phase shift was not accounted for.Conclusions: Margins can only be reduced for respiratory gated radiotherapy, if respiratory baseline shifts and variations in external/internal motion correlation are accounted for. Gated beam delivery alone cannot facilitate margin reduction. In the worst case, margins must be increased to accommodate inter-fraction variations in respiration. (C) 2007 Elsevier Ireland Ltd. All rights reserved.