Department of Radiation Oncology, Stanford School of Medicine, Stanford University, Stanford, CA, USA.
RaySearch Laboratories AB, Stockholm, Sweden.
Med Phys. 2017 Jun;44(6):2544-2555. doi: 10.1002/mp.12233. Epub 2017 May 4.
The aim of this study was to evaluate the performance of very high-energy electron beams (VHEE) in comparison to clinically derived treatment plans generated with volumetric modulated arc therapy (VMAT) and proton pencil beam scanning (PPBS) technology. We developed a custom optimization script that could be applied automatically across modalities to eliminate operator bias during IMRT optimization.
Four clinical cases were selected (prostate cancer, lung cancer, pediatric brain tumor, and head and neck cancer (HNC)). The VHEE beams were calculated in the EGSnrc/DOSXYZnrc Monte Carlo code for 100 and 200 MeV beams. Treatment plans with VHEE, VMAT, and PPBS were optimized in a research version of RayStation using an in-house developed script to minimize operator bias between the different techniques.
The in-house developed script generated similar or superior plans to the clinically used plans. In the comparisons between the modalities, the integral dose was lowest for the PPBS-generated plans in all cases. For the prostate case, the 200 MeV VHEE plan showed reduced integral dose and reduced organ at risk (OAR) dose compared to the VMAT plan. For all other cases, both the 100 and the 200 MeV VHEE plans were superior to the VMAT plans, and the VHEE plans showed better conformity and lower spinal cord dose in the pediatric brain case and lower brain stem dose in the HNC case when compared to the PPBS plan.
The automated optimization developed in this study generated similar or superior plans as compared to the clinically used plan and represents an unbiased approach to compare treatment plans generated for different modalities. In the present study, we also show that VHEE plans are similar or superior to VMAT plans with reduced mean OAR dose and increased target conformity for a variety of clinical cases, and VHEE plans can even achieve reductions in OAR doses compared to PPBS plans for shallow targets. With increased VHEE energy, better conformity and even higher reductions in mean OAR doses are achieved. On the whole, VHEE was intermediate between photon VMAT and PPBS for OAR sparing.
本研究旨在评估超高能电子束（VHEE）的性能，并与容积调强弧形治疗（VMAT）和质子铅笔束扫描（PPBS）技术生成的临床治疗计划进行比较。我们开发了一个自定义优化脚本，可以跨模式自动应用，以在调强优化过程中消除操作员的偏差。
选择了四个临床病例（前列腺癌、肺癌、儿童脑肿瘤和头颈部癌症（HNC））。在 EGSnrc/DOSXYZnrc 蒙特卡罗代码中计算了 100 MeV 和 200 MeV 的 VHEE 束。在 RayStation 的研究版本中，使用内部开发的脚本对 VHEE、VMAT 和 PPBS 的治疗计划进行优化，以最大限度地减少不同技术之间的操作员偏差。
内部开发的脚本生成的计划与临床使用的计划相似或更优。在模式之间的比较中，在所有情况下，PPBS 生成的计划的整体剂量最低。对于前列腺病例，与 VMAT 计划相比，200 MeV VHEE 计划显示出更低的整体剂量和更低的危及器官（OAR）剂量。对于所有其他病例，100 MeV 和 200 MeV VHEE 计划均优于 VMAT 计划，与 PPBS 计划相比，VHEE 计划在儿科脑肿瘤病例中显示更好的适形性和更低的脊髓剂量，在 HNC 病例中显示更低的脑干剂量。
本研究中开发的自动化优化生成的计划与临床使用的计划相似或更优，代表了一种无偏见的方法来比较不同模式生成的治疗计划。在本研究中，我们还表明，VHEE 计划在各种临床情况下与 VMAT 计划相似或更优，可降低平均 OAR 剂量并提高靶区适形性，对于浅层靶区，VHEE 计划甚至可以降低 OAR 剂量与 PPBS 计划相比。随着 VHEE 能量的增加，更好的适形性甚至更高的平均 OAR 剂量降低都可以实现。总的来说，VHEE 在 OAR 保护方面介于光子 VMAT 和 PPBS 之间。
