Varian Medical Affairs, Palo Alto, California, USA.
Department of Radiation Oncology, University of California, Los Angeles, California, USA.
J Appl Clin Med Phys. 2024 May;25(5):e14295. doi: 10.1002/acm2.14295. Epub 2024 Feb 9.
PURPOSE/OBJECTIVE: Field size limitations on Halcyon and Ethos treatment machines largely preclude use of the conventional monoisocentric three-field technique for breast/chest wall and regional lymph nodes. We present an alternative, IMRT-based planning approach that facilitates treatment on Halcyon and Ethos while preserving plan quality.
MATERIALS/METHODS: Eight breast and regional node cases (four left-sided, four right-sided) were planned for an Ethos machine using a 15-17 field IMRT technique. Institutional plan quality metrics for CTV and PTV coverage and OAR sparing were assessed. Five plans (four right-sided, one left-sided) were also planned using a hybrid 3D multisocenter technique. CTV coverage and OAR sparing were compared to the IMRT plans. Eclipse scripting tools were developed to aid in beam placement and plan evaluation through a set of dosimetric scorecards, and both are shared publicly.
On average, the IMRT plans achieved breast CTV and PTV coverage at 50 Gy of 97.9% and 95.7%, respectively. Supraclavicular CTV and PTV coverages at 45 Gy were 100% and 95.5%. Axillary lymph node CTV and PTV coverages at 45 Gy were 100% and 97.1%, and IMN CTV coverage at 45 Gy was 99.2%. Mean ipsilateral lung V20 Gy was 19.3%, and average mean heart dose was 1.6 Gy for right-sided cases and 3.0 Gy for left-sided. In comparison to the hybrid 3D plans, IMRT plans achieved higher breast and supraclavicular CTV coverage (99.9% vs. 98.6% and 99.9% vs. 93.4%), higher IMN coverage (99.6% vs. 78.2%), and lower ipsilateral lung V20 Gy (19.6% vs. 28.2%).
Institutional plan quality benchmarks were achieved for all eight cases using the IMRT-based planning approach. The IMRT-based planning approach offered superior conformity and OAR sparing than a competing hybrid 3D approach.
目的/目标：Halcyon 和 Ethos 治疗机的射野大小限制很大程度上排除了常规的单中心三野技术在乳房/胸壁和区域淋巴结中的应用。我们提出了一种替代的、基于调强放疗的计划方法，该方法可以在 Halcyon 和 Ethos 上进行治疗，同时保持计划质量。
材料/方法：对 8 例乳腺癌和区域淋巴结病例（左侧 4 例，右侧 4 例）进行了 Ethos 机器的计划，采用了 15-17 野调强放疗技术。评估了机构计划的关键靶区（CTV）和计划靶区（PTV）覆盖和 OAR 保护的质量指标。还使用混合 3D 多中心技术对 5 例（右侧 4 例，左侧 1 例）病例进行了计划。比较了 CTV 覆盖和 OAR 保护情况。开发了 Eclipse 脚本工具，通过一组剂量学记分卡来辅助光束放置和计划评估，并公开共享。
平均而言，调强放疗计划在 50Gy 时实现了 97.9%和 95.7%的乳房 CTV 和 PTV 覆盖，锁骨上 CTV 和 PTV 覆盖率分别为 100%和 95.5%。腋淋巴结 CTV 和 PTV 覆盖率分别为 100%和 97.1%，IMN CTV 覆盖率为 45Gy 时为 99.2%。平均同侧肺 V20Gy 为 19.3%，右侧病例的平均心脏剂量为 1.6Gy，左侧病例为 3.0Gy。与混合 3D 计划相比，调强放疗计划实现了更高的乳房和锁骨上 CTV 覆盖率（99.9%对 98.6%和 99.9%对 93.4%）、更高的 IMN 覆盖率（99.6%对 78.2%）和更低的同侧肺 V20Gy（19.6%对 28.2%）。
使用基于调强放疗的计划方法，所有 8 例病例均达到了机构计划质量基准。基于调强放疗的计划方法在适形度和 OAR 保护方面优于竞争的混合 3D 方法。
