Department of Medical Physics and Biomedical Engineering, University College London, London, UK.
Department of Radiotherapy Physics, University College London Hospitals NHS Foundation Trust, London, UK.
Med Phys. 2019 Mar;46(3):1150-1162. doi: 10.1002/mp.13382. Epub 2019 Feb 1.
In pencil beam scanning proton therapy, target coverage is achieved by scanning the pencil beam laterally in the x- and y-directions and delivering spots of dose to positions at a given radiological depth (layer). Dose is delivered to the spots on different layers by pencil beams of different energy until the entire volume has been irradiated. The aim of this study is to investigate the implementation of proton planning parameters (spot spacing, layer spacing and margins) in four commercial proton treatment planning systems (TPSs): Eclipse, Pinnacle , RayStation and XiO.
Using identical beam data in each TPS, plans were created on uniform material synthetic phantoms with cubic targets. The following parameters were systematically varied in each TPS to observe their different implementations: spot spacing, layer spacing and margin. Additionally, plans were created in Eclipse to investigate the impact of these parameters on plan delivery and optimal values are suggested.
It was found that all systems except Eclipse use a variable layer spacing per beam, based on the Bragg peak width of each energy layer. It is recommended that if this cannot be used, then a constant value of 5 mm will ensure good dose homogeneity. Only RayStation varies the spot spacing according to the variable spot size with depth. If a constant spot spacing is to be used, a value of 5 mm is recommended as a good compromise between dose homogeneity, plan robustness and planning time. It was found that both Pinnacle and RayStation position spots outside of the defined volume (target plus margin).
All four systems are capable of delivering uniform dose distributions to simple targets, but their implementation of the various planning parameters is different. In this paper comparisons are made between the four systems and recommendations are made as to the values that will provide the best compromise in dose homogeneity and planning time.
在铅笔束扫描质子治疗中，通过在 x 和 y 方向上横向扫描铅笔束，并将剂量点输送到给定放射深度（层）的位置，从而实现靶区覆盖。通过不同能量的铅笔束将剂量输送到不同层的点，直到整个体积都被照射。本研究的目的是研究在四个商业质子治疗计划系统（TPS）中实施质子计划参数（点间距、层间距和边界）：Eclipse、Pinnacle、RayStation 和 XiO。
在每个 TPS 中使用相同的光束数据，在均匀材料合成体模上创建具有立方靶区的计划。在每个 TPS 中系统地改变以下参数，以观察它们的不同实现：点间距、层间距和边界。此外，在 Eclipse 中创建了计划，以研究这些参数对计划交付的影响，并建议了最佳值。
发现除了 Eclipse 之外，所有系统都根据每个能量层的布拉格峰宽度使用可变的层间距。建议如果不能使用此功能，则使用 5mm 的恒定值将确保良好的剂量均匀性。只有 RayStation 根据深度变化的可变点大小来改变点间距。如果要使用恒定的点间距，则建议使用 5mm 的值，这是在剂量均匀性、计划稳健性和计划时间之间取得良好折衷的好方法。发现 Pinnacle 和 RayStation 都将点定位在定义的体积（靶区加边界）之外。
所有四个系统都能够为简单靶区提供均匀的剂量分布，但它们对各种计划参数的实现方式不同。本文对四个系统进行了比较，并提出了在剂量均匀性和计划时间方面提供最佳折衷的建议值。
