Department of Radiation Oncology, The First Medical Center of PLA General Hospital, Beijing, 100853, China.
Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Kowloon, Hong Kong.
Radiat Oncol. 2021 Oct 29;16(1):206. doi: 10.1186/s13014-021-01932-0.
In the existing application of beam-matched multiroom proton therapy system, the model based on the commissioning data from the leading treatment room was used as the shared model. The purpose of this study is to investigate the ability of independently-tuned room-specific beam models of beam-matched gantries to reproduce the agreement between gantries' performance when considering the errors introduced by the modeling process.
Raw measurements of two gantries' dosimetric characteristics were quantitatively compared to ensure their agreement after initially beam-matched. Two gantries' beam model parameters, as well as the model-based computed dosimetric characteristics, were analyzed to study the introduced errors and gantries' post-modeling consistency. We forced two gantries to share the same beam model. The model-sharing patient-specific quality assurance (QA) tasks were retrospectively performed with 36 cancer patients to study the clinical impact of beam model discrepancies.
Intra-gantry comparisons demonstrate that the modeling process introduced the errors to a certain extent indeed, which made the model-based reproduced results deviate from the raw measurements. Among them, the deviation introduced to the IDD curves was generally larger than that to the beam spots during modeling. Cross-gantry comparisons show that, from the beam model perspective, the introduced deviations deteriorated the high agreement of the dosimetric characteristics originally shown between two beam-matched gantries, but the cross-gantry discrepancy was still within the clinically acceptable tolerance. In model-sharing patient-specific QA, for the particular gantry, the beam model usage for intensity-modulated proton therapy (IMPT) QA plan generation had no significant effect on the actual delivering performance. All reached a high level of 95.0% passing rate with a 3 mm/3% criterion.
It was preliminary recognized that among beam-matched gantries, the independently-tuned room-specific beam model from any gantry is reasonable to be chosen as the shared beam model without affecting the treatment efficacy.
在现有的束流匹配多室质子治疗系统的应用中，使用来自主导治疗室的调试数据的基于模型的方法作为共享模型。本研究的目的是研究束流匹配龙门架的独立调整的特定房间的束流模型在考虑建模过程引入的误差的情况下，再现龙门架性能之间一致性的能力。
对两个龙门架的剂量学特性的原始测量值进行定量比较，以确保在初始束流匹配后其性能一致。分析两个龙门架的束流模型参数以及基于模型的计算剂量学特性，以研究引入的误差和龙门架的建模后一致性。我们强制两个龙门架共享相同的束流模型。回顾性地对 36 名癌症患者进行模型共享的患者特定质量保证（QA）任务，以研究束流模型差异的临床影响。
内部龙门架比较表明，建模过程确实在一定程度上引入了误差，这使得基于模型的再现结果偏离了原始测量值。其中，在建模过程中，IDD 曲线引入的偏差通常大于束斑引入的偏差。跨龙门架比较表明，从束流模型的角度来看，引入的偏差恶化了原本在两个束流匹配的龙门架之间显示的剂量学特性的高度一致性，但跨龙门架的差异仍在临床可接受的容限内。在模型共享的患者特定 QA 中，对于特定的龙门架，强度调制质子治疗（IMPT）QA 计划生成中束流模型的使用对实际输送性能没有显著影响。所有计划都达到了很高的水平，95.0%的通过率，使用 3mm/3%的标准。
初步认识到，在束流匹配的龙门架中，任何龙门架的独立调整的特定房间的束流模型都可以合理地被选择作为共享束流模型，而不会影响治疗效果。
