McGowan S E, Albertini F, Thomas S J, Lomax A J
Department of Oncology, University of Cambridge, Cambridge, UK.
Phys Med Biol. 2015 Apr 7;60(7):2671-84. doi: 10.1088/0031-9155/60/7/2671. Epub 2015 Mar 13.
We aim to define a site-specific robustness protocol to be used during the clinical plan evaluation process. Plan robustness of 16 skull base IMPT plans to systematic range and random set-up errors have been retrospectively and systematically analysed. This was determined by calculating the error-bar dose distribution (ebDD) for all the plans and by defining some metrics used to define protocols aiding the plan assessment. Additionally, an example of how to clinically use the defined robustness database is given whereby a plan with sub-optimal brainstem robustness was identified. The advantage of using different beam arrangements to improve the plan robustness was analysed. Using the ebDD it was found range errors had a smaller effect on dose distribution than the corresponding set-up error in a single fraction, and that organs at risk were most robust to the range errors, whereas the target was more robust to set-up errors. A database was created to aid planners in terms of plan robustness aims in these volumes. This resulted in the definition of site-specific robustness protocols. The use of robustness constraints allowed for the identification of a specific patient that may have benefited from a treatment of greater individuality. A new beam arrangement showed to be preferential when balancing conformality and robustness for this case. The ebDD and error-bar volume histogram proved effective in analysing plan robustness. The process of retrospective analysis could be used to establish site-specific robustness planning protocols in proton therapy. These protocols allow the planner to determine plans that, although delivering a dosimetrically adequate dose distribution, have resulted in sub-optimal robustness to these uncertainties. For these cases the use of different beam start conditions may improve the plan robustness to set-up and range uncertainties.
我们旨在定义一种特定部位的稳健性协议，以便在临床计划评估过程中使用。对16个颅底调强质子治疗（IMPT）计划针对系统范围和随机摆位误差的计划稳健性进行了回顾性和系统性分析。这是通过计算所有计划的误差条剂量分布（ebDD）以及定义一些用于定义辅助计划评估的协议的指标来确定的。此外，给出了一个临床使用所定义的稳健性数据库的示例，借此识别出一个脑干稳健性欠佳的计划。分析了使用不同射束排列来提高计划稳健性的优势。利用ebDD发现，在单次分割中，范围误差对剂量分布的影响小于相应的摆位误差，并且危及器官对范围误差最为稳健，而靶区对摆位误差更为稳健。创建了一个数据库，以帮助计划制定者实现这些靶区的计划稳健性目标。这导致了特定部位稳健性协议的定义。使用稳健性约束能够识别出可能从更具个性化的治疗中获益的特定患者。对于这种情况，在平衡适形性和稳健性时，一种新的射束排列显示出更具优势。ebDD和误差条体积直方图在分析计划稳健性方面被证明是有效的。回顾性分析过程可用于建立质子治疗中特定部位的稳健性计划协议。这些协议使计划制定者能够确定那些虽然提供了剂量学上合适的剂量分布，但对这些不确定性的稳健性欠佳的计划。对于这些情况，使用不同的射束起始条件可能会提高计划对摆位和范围不确定性的稳健性。
