BackgroundRescanning is a common technique used in proton pencil beam scanning to mitigate the interplay effect. Advances in machine operating parameters across different generations of particle therapy systems have led to improvements in beam delivery time (BDT). However, the potential impact of these improvements on the effectiveness of rescanning remains an underexplored area in the existing research.MethodsWe systematically investigated the impact of proton machine operating parameters on the effectiveness of layer rescanning in mitigating interplay effect during lung SBRT treatment, using the CIRS phantom. Focused on the Hitachi synchrotron particle therapy system, we explored machine operating parameters from our institution's current (2015) and upcoming systems (2025A and 2025B). Accumulated dynamic 4D dose were reconstructed to assess the interplay effect and layer rescanning effectiveness.ResultsAchieving target coverage and dose homogeneity within 2% deviation required 6, 6, and 20 times layer rescanning for the 2015, 2025A, and 2025B machine parameters, respectively. Beyond this point, further increasing the number of layer rescanning did not further improve the dose distribution. BDTs without rescanning were 50.4, 24.4, and 11.4 s for 2015, 2025A, and 2025B, respectively. However, after incorporating proper number of layer rescanning (six for 2015 and 2025A, 20 for 2025B), BDTs increased to 67.0, 39.6, and 42.3 s for 2015, 2025A, and 2025B machine parameters. Our data also demonstrated the potential problem of false negative and false positive if the randomness of the respiratory phase at which the beam is initiated is not considered in the evaluation of interplay effect.ConclusionThe effectiveness of layer rescanning for mitigating interplay effect is affected by machine operating parameters. Therefore, past clinical experiences may not be applicable to modern machines.

中文翻译：

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质子 PBS 机器操作参数对分层重新扫描有效性的影响，以减轻肺部 SBRT 治疗中的相互作用效应

背景重新扫描是质子笔形束扫描中用于减轻相互作用效应的常用技术。不同代粒子治疗系统的机器操作参数的进步导致了射束传输时间 (BDT) 的改善。然而，这些改进对重新扫描有效性的潜在影响仍然是现有研究中尚未探索的领域。方法我们使用 CIRS 系统地研究了质子机操作参数对分层重新扫描在减轻肺部 SBRT 治疗期间相互作用效应的有效性的影响幻影。我们以日立同步加速器粒子治疗系统为重点，探索了我们机构当前（2015 年）和即将推出的系统（2025A 和 2025B）的机器运行参数。重建累积的动态4D剂量，以评估相互作用效应和分层重新扫描有效性。结果对于2015、2025A和2025B机器参数，要实现目标覆盖和剂量均匀性在2%偏差内，分别需要6次、6次和20次分层重新扫描。除此之外，进一步增加层数重新扫描的数量并不能进一步改善剂量分布。 2015 年、2025A 和 2025B 未重新扫描的 BDT 分别为 50.4、24.4 和 11.4 秒。然而，在纳入适当数量的层重新扫描（2015 年和 2025A 为 6 层，2025B 为 20 层）后，2015 年、2025A 和 2025B 机器参数的 BDT 增加到 67.0、39.6 和 42.3 秒。我们的数据还表明，如果在评估相互作用效应时不考虑启动波束的呼吸阶段的随机性，则可能存在假阴性和假阳性的潜在问题。结论层重新扫描减轻相互作用效应的有效性受到机器操作的影响参数。因此，过去的临床经验可能不适用于现代机器。