Royal Brisbane and Women's Hospital, Herston, QLD 4029, Australia; Queensland University of Technology, Brisbane, QLD 4001, Australia.
Royal Brisbane and Women's Hospital, Herston, QLD 4029, Australia; Queensland University of Technology, Brisbane, QLD 4001, Australia.
Phys Med. 2020 Oct;78:166-172. doi: 10.1016/j.ejmp.2020.09.021. Epub 2020 Oct 6.
This work presents a novel method of visualising the results of patient-specific quality assurance (QA) for modulated radiotherapy treatment plans, using a three-dimensional distribution of gamma pass rates, referred to as the "gamma surface". The method was developed to aid in comparing borderline and failing QA plans, and to better compare patient-specific QA results between departments.
Gamma surface plots were created for a representative sample of situations encountered during patient-specific QA. To produce a gamma surface plot, for each QA result, gamma pass rates were plotted as a heat map, with dose difference on one axis and distance-to-agreement on the other. This involved the calculation of 100 × 100 gamma pass rates over a dose difference and distance-to-agreement grid. As examples, five 220 × 680 arrays of dose points from radiotherapy treatment plans were compared against measurement data consisting of 21 × 66 arrays of dose points spaced 10 mm apart.
The gamma surface plots facilitated the rapid evaluation of criteria combinations for each plan, clearly highlighting the difference between plans that are modelled and delivered well, and those that are not. Large scale features were also evident in each surface, hinting at potential over-modulation, systematic dose errors, and small or large scale areas of disagreement in the distributions.
Gamma surface plots are a useful tool for investigating QA failures and borderline results, and have the capacity to grant insights into treatment plan QA performance that may otherwise be missed.
本研究提出了一种新的方法，用于可视化个体化调强放射治疗计划质量保证（QA）的结果，使用三维伽马通过率分布，称为“伽马曲面”。该方法旨在帮助比较边缘和失败的 QA 计划，并更好地比较不同科室之间的个体化 QA 结果。
为患者特定 QA 中遇到的代表性情况创建了伽马曲面图。为了生成伽马曲面图，对于每个 QA 结果，伽马通过率以热图的形式绘制，一个轴是剂量差异，另一个轴是剂量差异和协议差异。这涉及到在剂量差异和协议差异网格上计算 100×100 个伽马通过率。例如，将 220×680 个剂量点的数组与由 21×66 个剂量点组成的测量数据进行比较，这些剂量点之间的间隔为 10mm。
伽马曲面图便于快速评估每个计划的标准组合，清楚地突出了建模和交付良好的计划与未建模和交付良好的计划之间的区别。每个曲面图上还存在大尺度特征，暗示潜在的过度调制、系统剂量误差以及分布中存在小或大尺度的不一致区域。
伽马曲面图是调查 QA 失败和边缘结果的有用工具，并且有可能深入了解治疗计划 QA 性能，否则可能会被忽略。
