标题： 质子笔形束扫描对移动靶区实时再优化的剂量学影响 显示英文标题

标题： Dosimetric impact of real-time re-optimization of proton pencil-beam scanning for moving targets

摘要： 在治疗移动肿瘤时，通过笔形束扫描（PBS）精确传递质子治疗受到交错效应的挑战。尽管已经提出了几种4D优化方法，但最有益的运动管理技术仍然是一个开放性问题。在本研究中，我们希望调查在治疗过程中根据患者呼吸模式的变化进行实时重新优化PBS点权重的剂量学影响，以及对此变化的预期。我们模拟了基于滚动时域控制原理的实时自适应框架在PBS中的实现。我们将患者运动视为由一维振幅信号和4DCT表征，以模拟不同频率的呼吸。该框架跟踪信号并预测未来运动，且预测时间越长，不确定性越大。在每次传递能量层之后，该框架根据传递的剂量和预测的运动重新优化下一层的点权重。对于三位肺癌患者，我们生成了500种可变呼吸模式，以评估该框架的剂量学结果，并将其与之前提出的非自适应方法的实现进行比较。与最佳的非自适应方法相比，自适应框架在接近最差呼吸情景（第5百分位）中将CTV D98从处方剂量的96.4%提高到98.9%，并通过平均四分位距减少超过80%显著减少了变化。目标覆盖的改善没有通常损害目标剂量均匀性或OAR剂量。该研究表明，基于在传递过程中重新优化点权重的运动自适应方法，有望显著提高给定快速准确的患者运动模型的PBS剂量学性能。 显示英文摘要

摘要： When treating moving tumors, the precise delivery of proton therapy by pencil beam scanning (PBS) is challenged by the interplay effect. Although several 4D-optimization methods have been proposed, what is the most beneficial motion management technique is still an open question. In this study, we wish to investigate the dosimetric impact of re-optimizing the PBS spot weights during the treatment delivery in response to, and in anticipation of, variations in the patient's breathing pattern. We simulate for PBS the implementation of a real-time adaptive framework based on principles from receding horizon control. We consider the patient motion as characterized by a one-dimensional amplitude signal and a 4DCT, to simulate breathing of variable frequency. The framework tracks the signal and predicts the future motion with uncertainty increasing with the length of the prediction horizon. After each delivered energy layer, the framework re-optimizes the spot weights of the next layer based on the delivered dose and the predicted motion. For three lung patients, we generate 500 variable breathing patterns to evaluate the dosimetric results of the framework and compare them to those of implementations of previously proposed non-adaptive methods. Compared to the best non-adaptive method, the adaptive framework improves the CTV D98 in the near-worst breathing scenario (5th percentile), from 96.4 to 98.9 % of the prescribed dose and considerably reduces the variation as measured by a mean decrease in the inter-quartile range by more than 80 %. The target coverage improvements are achieved without generally compromising target dose homogeneity or OAR dose. The study indicates that a motion-adaptive approach based on re-optimization of spot weights during delivery has the potential to substantially improve the dosimetric performance of PBS given fast and accurate models of patient motion.