背景:比较不同放射治疗技术的研究-例如体积调制电弧疗法(VMAT)和螺旋断层放射治疗(HT)-通常比较每种技术的一种治疗计划。通常,一些剂量指标支持一个计划,另一些支持另一个计划,所以最终的计划决策涉及主观偏好。帕累托前沿比较为比较不同的治疗技术提供了更客观的框架。帕累托前沿是所有治疗计划的集合,其中只有通过恶化另一个标准才能改善一个标准。然而,不同的帕累托前沿可以根据所选择的机器设置获得。
目的:使用帕累托前沿和盲目专家评估来比较VMAT和HT,为了解释观察到的差异,并说明使用帕累托前沿的局限性。
方法:我们使用控制商业治疗计划系统的内部脚本,为在我们的诊所接受VMAT和HT技术治疗的24名前列腺癌患者生成了Pareto前沿。我们改变了PTV的覆盖范围(100%-V95%)和直肠平均剂量,并固定膀胱和股骨头的平均剂量。为了确保公平的比较,两种治疗技术的固定平均剂量相同,选择目标函数集,使两种治疗技术的一致性指数也相同。我们使用的机器设置与我们诊所使用的相同。然后,我们使用特定指标(临床距离测量)比较了VMAT和HTPareto前沿,并使用盲法专家对队列中所有患者的治疗计划进行评估,验证了比较.此外,我们调查了观察到的VMAT和HT之间的差异,并指出了使用Pareto前沿的局限性。
结果:临床距离和盲目治疗计划比较均显示,VMAT帕累托前沿优于HT前沿。10和6MV光束能量的VMAT前沿几乎相同。HT前端通过不同的机器设置进行了改进,但仍不如VMAT战线。
结论:VMATPareto前沿比HT前沿更好,这可以通过线性加速器可以快速改变剂量率这一事实来解释。这在可能在更复杂的几何形状中消失的简单几何形状中是有利的。此外,当谈到帕累托最优计划是最好的计划时,应该谨慎,因为它们的计算取决于许多参数。
BACKGROUND: Studies comparing different radiotherapy treatment techniques-such as volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT)-typically compare one treatment plan per technique. Often, some dose metrics favor one plan and others favor the other, so the final plan decision involves subjective preferences. Pareto front comparisons provide a more objective framework for comparing different treatment techniques. A Pareto front is the set of all treatment plans where improvement in one criterion is possible only by worsening another criterion. However, different Pareto fronts can be obtained depending on the chosen machine settings.
OBJECTIVE: To compare VMAT and HT using Pareto fronts and blind expert evaluation, to explain the observed differences, and to illustrate limitations of using Pareto fronts.
METHODS: We generated Pareto fronts for twenty-four prostate cancer patients treated at our clinic for VMAT and HT techniques using an in-house script that controlled a commercial treatment planning system. We varied the PTV under-coverage (100% - V95%) and the rectum mean dose, and fixed the mean doses to the bladder and femoral heads. In order to ensure a fair comparison, those fixed mean doses were the same for the two treatment techniques and the sets of objective functions were chosen so that the conformity indexes of the two treatment techniques were also the same. We used the same machine settings as are used in our clinic. Then, we compared the VMAT and HT Pareto fronts using a specific metric (clinical distance measure) and validated the comparison using a blinded expert evaluation of treatment plans on these fronts for all patients in the cohort. Furthermore, we investigated the observed differences between VMAT and HT and pointed out limitations of using Pareto fronts.
RESULTS: Both clinical distance and blind treatment plan comparison showed that VMAT Pareto fronts were better than HT fronts. VMAT fronts for 10 and 6 MV beam energy were almost identical. HT fronts improved with different machine settings, but were still inferior to VMAT fronts.
CONCLUSIONS: That VMAT Pareto fronts are better than HT fronts may be explained by the fact that the linear accelerator can rapidly vary the dose rate. This is an advantage in simple geometries that might vanish in more complex geometries. Furthermore, one should be cautious when speaking about Pareto optimal plans as the best possible plans, as their calculation depends on many parameters.