Department of Radiation Oncology, Amsterdam UMC location Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
Cancer Center Amsterdam, Cancer Treatment and Quality of Life, Amsterdam, The Netherlands.
J Appl Clin Med Phys. 2023 Mar;24(3):e13841. doi: 10.1002/acm2.13841. Epub 2022 Dec 26.
Single-visit radiotherapy (RT) is beneficial for patients requiring pain control and can limit interruptions to systemic treatments. However, the requirement for a dedicated planning CT (pCT)-scan can result in treatment delays. We developed a workflow involving preplanning on available diagnostic CT (dCT) imaging, followed by online plan adaption using a cone-beam CT (CBCT)-scan prior to RT-delivery, in order to account for any changes in anatomy and target position.
Patients previously treated with palliative RT for bone metastases were selected from our hospital database. Patient dCT-images were deformed to treatment CBCTs in the Ethos platform (Varian Medical Systems) and a synthetic CT (sCT) generated. Treatment quality was analyzed by comparing a coverage of the V95% of the planning/clinical target volume and different organ-at-risk (OAR) doses between adapted and initial clinical treatment plans. Doses were recalculated on the CBCT and sCT in a separate treatment planning system. Adapted plan doses were measured on-couch using an anthropomorphic phantom with a Gafchromic EBT3 dosimetric film and compared to dose calculations.
All adapted treatment plans met the clinical goals for target and OARs and outperformed the original treatment plans calculated on the (daily) sCT. Differences in V95% of the target volume coverage between the initial and adapted treatments were <0.2%. Dose recalculations on CBCT and sCT were comparable, and the average gamma pass rate (3%/2 mm) of dosimetric measurements was 98.8%.
Online daily adaptive RT using dCTs instead of a dedicated pCT is feasible using the Ethos platform. This workflow has now been implemented clinically.
单次放疗（RT）有利于需要止痛控制的患者，并能限制对全身治疗的中断。然而，对专用计划 CT（pCT）-扫描的需求可能会导致治疗延迟。我们开发了一种工作流程，涉及在可用的诊断 CT（dCT）成像上进行预计划，然后在 RT 治疗前使用锥形束 CT（CBCT）-扫描进行在线计划适应，以考虑到解剖结构和目标位置的任何变化。
从我们的医院数据库中选择了先前接受姑息性 RT 治疗骨转移的患者。在 Ethos 平台（Varian Medical Systems）中将患者的 dCT 图像变形到治疗 CBCT 上，并生成合成 CT（sCT）。通过比较计划/临床靶区的 V95%覆盖范围以及不同的危及器官（OAR）剂量，分析治疗质量。在另一个治疗计划系统中，在 CBCT 和 sCT 上重新计算剂量。在具有 Gafchromic EBT3 剂量测定胶片的人体模型上进行床旁测量，并用自适应计划剂量进行测量，并与剂量计算进行比较。
所有适应治疗计划都满足了目标和 OAR 的临床目标，并且优于基于（每日）sCT 计算的原始治疗计划。初始和适应治疗之间靶区覆盖率的 V95%差异小于 0.2%。在 CBCT 和 sCT 上的剂量重新计算是可比的，剂量测量的平均伽马通过率（3%/2mm）为 98.8%。
使用 Ethos 平台使用 dCT 而不是专用的 pCT 进行在线每日自适应 RT 是可行的。该工作流程现已在临床中实施。
