Tumour tracking is an advanced radiotherapy technique for precise treatment of tumours subject to organ motion. In this work, we addressed crucial aspects of dose delivery for its realisation in pencil beam scanning proton therapy, exploring the momentum acceptance and global achromaticity of a Gantry beamline to perform continuous energy regulation with a standard upstream degrader. This novel approach is validated on simulation data from three geometric phantoms of increasing complexity and one liver cancer patient using 4D dose calculations. Results from a standard high-to-low beamline ramping scheme were compared to alternative energy meandering schemes including combinations with rescanning. Target coverage and dose conformity were generally well recovered with tumour tracking even though for particularly small targets, large variations are reported for the different approaches. Meandering in energy while rescanning has a positive impact on target homogeneity and similarly, hot spots outside the targets are mitigated with a relatively fast convergence rate for most tracking scenarios, halving the volume of hot spots after as little as 3 rescans. This work investigates the yet unexplored potential of having a large momentum acceptance in medical beam line, and provides an alternative to take tumour tracking with particle therapy closer to clinical translation.

肿瘤追踪是一种先进的放射治疗技术，用于精确治疗受器官运动影响的肿瘤。在这项工作中，我们解决了剂量传递在笔形束扫描质子治疗中实现的关键方面，探索了龙门光束线的动量接受和全局消色差，以使用标准上游降解器进行连续能量调节。这种新颖的方法在来自三个日益复杂的几何模型和一个肝癌患者的模拟数据上得到了验证，使用 4D 剂量计算。将标准从高到低光束线渐变方案的结果与包括与重新扫描组合的替代能量蜿蜒方案进行了比较。即使对于特别小的目标，目标覆盖率和剂量一致性通常可以通过肿瘤追踪得到很好的恢复，不同的方法报告了很大的差异。重新扫描时的能量蜿蜒对目标均匀性有积极影响，同样，对于大多数跟踪场景，目标外部的热点以相对较快的收敛速度得到缓解，只需重新扫描 3 次，热点数量就会减半。这项工作研究了在医学光束线中具有大动量接受度的尚未开发的潜力，并提供了一种替代方法，使粒子治疗的肿瘤跟踪更接近临床转化。