Interplay effects in proton scanning for lung: a 4D Monte Carlo study assessing the impact of tumor and beam delivery parameters.
Interplay effects in proton scanning for lung: a 4D Monte Carlo study assessing the impact of tumor and beam delivery parameters.
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DOI：
10.1088/0031-9155/58/12/4137
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发表时间：
2013-06-21
影响因子：
3.5
通讯作者：
Paganetti H
中科院分区：
文献类型：
--
作者：
Dowdell S;Grassberger C;Sharp GC;Paganetti H
肿瘤和扫描质子束之间的相对运动导致剂量分布的退化（相互作用效应）。本研究探讨了光束扫描参数和相互作用效应之间的关系，目的是找到最小化相互作用的参数。使用不同肿瘤大小（50.4 - 167.1cc）和运动幅度（2.9 - 30.1mm）的5名肺癌患者的4DCT几何结构进行了笔形束扫描质子治疗的4D Monte Carlo模拟。治疗计划假设以35 × 2.5Gy（RBE）分次输送。5名患者的光斑尺寸、改变射束能量的时间（τ es）、磁体稳定所需的时间（τ ss）、初始呼吸相位、光斑间距、扫描方向、扫描速度、射束电流和患者呼吸周期各不相同。模拟进行了一个单一的馏分和传统的分馏的近似。对于所考虑的患者，无法单独使用上下（SI）运动幅度预测相互作用效应。较大的斑点尺寸（σ~9 - 16 mm）对相互作用不太敏感，在单个部分中给出99.0 ± 4.4%（1个标准差）的等效均匀剂量（EUD），而较小的斑点（σ~2 - 4 mm）为86.1 ± 13.1%。较小的斑点尺寸使EUD值低至处方剂量的65.3%。减小光斑间距改善了靶剂量均匀性。初始呼吸阶段可能对相互作用产生显著影响，特别是对于较短的输送时间。当扫描平行或垂直于运动主轴时，没有明显的益处。较长的呼吸周期降低了EUD。一般来说，较长的交货时间导致较低的相互作用的影响。常规分次在相互作用方面显示出显著的改善，对于较小和较大的斑点尺寸，EUD分别为处方剂量的至少84.7%和100.0%。相互作用效应是高度患者特异性的，取决于运动幅度、肿瘤位置和递送参数。在一个单一的分数的剂量分布的大退化进行了观察，但使用传统的分割显着改善。
Relative motion between a tumor and a scanning proton beam results in a degradation of the dose distribution (interplay effect). This study investigates the relationship between beam scanning parameters and the interplay effect, with the goal of finding parameters that minimize interplay. 4D Monte Carlo simulations of pencil beam scanning proton therapy treatments were performed using the 4DCT geometry of 5 lung cancer patients of varying tumor size (50.4–167.1cc) and motion amplitude (2.9–30.1mm). Treatments were planned assuming delivery in 35×2.5Gy(RBE) fractions. The spot size, time to change the beam energy (τes), time required for magnet settling (τss), initial breathing phase, spot spacing, scanning direction, scanning speed, beam current and patient breathing period were varied for each of the 5 patients. Simulations were performed for a single fraction and an approximation of conventional fractionation. For the patients considered, the interplay effect could not be predicted using the superior-inferior (SI) motion amplitude alone. Larger spot sizes (σ ~9–16mm) were less susceptible to interplay, giving an equivalent uniform dose (EUD) of 99.0±4.4% (1 standard deviation) in a single fraction compared to 86.1±13.1% for smaller spots (σ ~2–4mm). The smaller spot sizes gave EUD values as low as 65.3% of the prescription dose in a single fraction. Reducing the spot spacing improved the target dose homogeneity. The initial breathing phase can have a significant effect on the interplay, particularly for shorter delivery times. No clear benefit was evident when scanning either parallel or perpendicular to the predominant axis of motion. Longer breathing periods decreased the EUD. In general, longer delivery times led to lower interplay effects. Conventional fractionation showed significant improvement in terms of interplay, giving a EUD of at least 84.7% and 100.0% of the prescription dose for the small and larger spot sizes respectively. The interplay effect is highly patient specific, depending on the motion amplitude, tumor location and the delivery parameters. Large degradations of the dose distribution in a single fraction were observed, but improved significantly using conventional fractionation.
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DOI：
10.1016/j.ijrobp.2009.06.091
发表时间：
2010-03-01
影响因子：
7
作者：
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影响因子：
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DOI：
10.1016/j.ijrobp.2010.02.059
发表时间：
2011-01-01
影响因子：
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