On the interplay effects with proton scanning beams in stage III lung cancer
On the interplay effects with proton scanning beams in stage III lung cancer
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DOI：
10.1118/1.4862076
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发表时间：
2014-02-01
期刊：
影响因子：
3.8
通讯作者：
Zhang, Xiaodong
中科院分区：
文献类型：
--
作者：
Li, Yupeng;Kardar, Laleh;Zhang, Xiaodong
目的：为评估点扫描质子束和呼吸运动之间的相互作用的剂量学影响的强度调制质子治疗（IMPT）为III期肺癌，方法：11例患者从112例III期非小细胞肺癌，以及代表112例患者的分布在目标的大小和运动。根据作者的临床方案定义临床靶体积（CTV）和计划靶体积（PTV）。均匀和现实的呼吸模式被认为是沿着与定期和hypofractionation的情况。在对应于点被输送的呼吸相位的计算机断层扫描（CT）图像上完全计算点贡献的剂量，然后将其累积到4DCT的参考相位，以生成动态剂量，该动态剂量提供了在相互作用效应的影响下可能输送的剂量的估计。将不同分数的动态剂量分布与相应的4D复合剂量进行比较，4D复合剂量是在4DCT图像集的呼吸相位上分别计算的剂量的等加权平均值。在常规分馏下，在所有35个分次输送后，4D复合剂量和动态剂量之间CTV覆盖率的平均和最大差异不超过0.2%和0.9%。脊髓、心脏V40、食管V55和肺V20的最大剂量的两种剂量分布之间的最大差异分别为1.2戈伊、0.1%、0.8%和0.4%。尽管观察到与相对于运动的小CTV相关的单次剂量差异相对较大，但作者的生物学反应计算表明，这种分次间剂量变化可能具有有限的生物学影响。假设一个hypofractionation的情况下，4D复合和动态剂量之间的差异被很好地限制，甚至为单一fractions.Conclusions：尽管存在相互作用的影响，提供的剂量可以可靠地估计使用4D复合剂量。一般来说，相互作用效应可能不是作者所在机构使用IMPT治疗肺癌的主要问题。所描述的相互作用分析工具可用于提供治疗递送的额外置信度。(C)2014年美国医学物理学家协会。
Purpose: To assess the dosimetric impact of interplay between spot-scanning proton beam and respiratory motion in intensity-modulated proton therapy (IMPT) for stage III lung cancer.Methods: Eleven patients were sampled from 112 patients with stage III nonsmall cell lung cancer to well represent the distribution of 112 patients in terms of target size and motion. Clinical target volumes (CTVs) and planning target volumes (PTVs) were defined according to the authors' clinical protocol. Uniform and realistic breathing patterns were considered along with regular-and hypofractionation scenarios. The dose contributed by a spot was fully calculated on the computed tomography (CT) images corresponding to the respiratory phase that the spot is delivered, and then accumulated to the reference phase of the 4DCT to generate the dynamic dose that provides an estimation of what might be delivered under the influence of interplay effect. The dynamic dose distributions at different numbers of fractions were compared with the corresponding 4D composite dose which is the equally weighted average of the doses, respectively, computed on respiratory phases of a 4DCT image set.Results: Under regular fractionation, the average and maximum differences in CTV coverage between the 4D composite and dynamic doses after delivery of all 35 fractions were no more than 0.2% and 0.9%, respectively. The maximum differences between the two dose distributions for the maximum dose to the spinal cord, heart V40, esophagus V55, and lung V20 were 1.2 Gy, 0.1%, 0.8%, and 0.4%, respectively. Although relatively large differences in single fraction, correlated with small CTVs relative to motions, were observed, the authors' biological response calculations suggested that this interfractional dose variation may have limited biological impact. Assuming a hypofractionation scenario, the differences between the 4D composite and dynamic doses were well confined even for single fraction.Conclusions: Despite the presence of interplay effect, the delivered dose may be reliably estimated using the 4D composite dose. In general the interplay effect may not be a primary concern with IMPT for lung cancers for the authors' institution. The described interplay analysis tool may be usedto provide additional confidence in treatment delivery. (C) 2014 American Association of Physicists in Medicine.