Department of Radiation Oncology, Strahlenklinik, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Universitätsstraße 27, 91054, Erlangen, Germany.
Comprehensive Cancer Center Erlangen-EMN (CCC ER-EMN), Erlangen, Germany.
Strahlenther Onkol. 2023 Aug;199(8):739-748. doi: 10.1007/s00066-023-02090-w. Epub 2023 Jun 7.
Auxiliary devices such as immobilization systems should be considered in synthetic CT (sCT)-based treatment planning (TP) for MRI-only brain radiotherapy (RT). A method for auxiliary device definition in the sCT is introduced, and its dosimetric impact on the sCT-based TP is addressed.
T1-VIBE DIXON was acquired in an RT setup. Ten datasets were retrospectively used for sCT generation. Silicone markers were used to determine the auxiliary devices' relative position. An auxiliary structure template (AST) was created in the TP system and placed manually on the MRI. Various RT mask characteristics were simulated in the sCT and investigated by recalculating the CT-based clinical plan on the sCT. The influence of auxiliary devices was investigated by creating static fields aimed at artificial planning target volumes (PTVs) in the CT and recalculated in the sCT. The dose covering 50% of the PTV (D) deviation percentage between CT-based/recalculated plan (∆D[%]) was evaluated.
Defining an optimal RT mask yielded a ∆D[%] of 0.2 ± 1.03% for the PTV and between -1.6 ± 3.4% and 1.1 ± 2.0% for OARs. Evaluating each static field, the largest ∆D[%] was delivered by AST positioning inaccuracy (max: 3.5 ± 2.4%), followed by the RT table (max: 3.6 ± 1.2%) and the RT mask (max: 3.0 ± 0.8% [anterior], 1.6 ± 0.4% [rest]). No correlation between ∆D[%] and beam depth was found for the sum of opposing beams, except for (45° + 315°).
This study evaluated the integration of auxiliary devices and their dosimetric influence on sCT-based TP. The AST can be easily integrated into the sCT-based TP. Further, we found that the dosimetric impact was within an acceptable range for an MRI-only workflow.
在仅基于 MRI 的脑部放射治疗（RT）的合成 CT（sCT）治疗计划（TP）中，应考虑使用固定系统等辅助设备。本文介绍了一种在 sCT 中定义辅助设备的方法，并研究了其对基于 sCT 的 TP 的剂量学影响。
在 RT 设置中采集 T1-VIBE DIXON。回顾性使用 10 个数据集生成 sCT。使用硅酮标记物确定辅助设备的相对位置。在 TP 系统中创建辅助结构模板（AST），并手动放置在 MRI 上。在 sCT 中模拟各种 RT 掩模特性，并通过在 sCT 上重新计算 CT 基础临床计划进行研究。通过在 CT 中创建针对人工计划靶区（PTV）的静态场并在 sCT 中重新计算来研究辅助设备的影响。评估了 PTV 覆盖 50%的剂量（D）与基于 CT/重新计算计划（∆D[%]）的偏差百分比。
定义最佳 RT 掩模可使 PTV 的 ∆D[%]为 0.2±1.03%，OAR 的 ∆D[%]为-1.6±3.4%至 1.1±2.0%。评估每个静态场，AST 定位不准确的 ∆D[%]最大（最大：3.5±2.4%），其次是 RT 台（最大：3.6±1.2%）和 RT 掩模（最大：3.0±0.8%[前]，1.6±0.4%[余]）。除了（45°+315°）之外，对于对向束的总和，没有发现∆D[%]与射束深度之间存在相关性。
本研究评估了辅助设备的整合及其对基于 sCT 的 TP 的剂量学影响。AST 可以轻松集成到基于 sCT 的 TP 中。此外，我们发现剂量学影响在仅基于 MRI 的工作流程的可接受范围内。
