De-Colle C, Nachbar M, Mӧnnich D, Boeke S, Gani C, Weidner N, Heinrich V, Winter J, Tsitsekidis S, Dohm O, Zips D, Thorwarth D
Department of Radiation Oncology, University Hospital and Medical Faculty, Eberhard Karls University Tübingen, Tübingen, Germany.
Section for Biomedical Physics, Department of Radiation Oncology, University Hospital and Medical Faculty, Eberhard Karls University Tübingen, Tübingen, Germany.
Clin Transl Radiat Oncol. 2021 Jan 22;27:103-108. doi: 10.1016/j.ctro.2020.12.005. eCollection 2021 Mar.
The hybrid magnetic resonance linear accelerator (MRL) has the potential to test novel concepts in breast cancer patients such as daily MR-guided real-time plan adaptation. Before starting clinical trials, preparatory studies for example of the MR-dependent electron stream effect (ESE) are necessary.
To prospectively investigate the ESE, data from 11 patients treated with partial breast irradiation (PBI) at the 1.5 T MRL were evaluated. A bolus was placed on the chin and dosimetry results were compared with the dose simulated by the treatment planning system (TPS). The same measurements were carried out for three patients treated at a conventional linac. Toxicity and cosmesis were evaluated.
Median doses measured and simulated on top/ underneath the bolus were 1.91 / 0.62 Gy and 2.82 / 0.63 Gy, respectively. Median differences between calculations and measurements were 0.8 Gy and 0.1 Gy. At the conventional linac, median measured doses on top/ underneath the bolus were 0.98 and 1.37 Gy. No acute toxicity exceeding grade 2 was recorded. Cosmesis was good or excellent and patient reported outcome measures were mostly scored as none or mild.
The dose due to the ESE is low, correctly predicted by the TPS and effectively minimized by a bolus.
混合磁共振直线加速器（MRL）有潜力在乳腺癌患者中测试新的概念，如每日磁共振引导下的实时计划调整。在开始临床试验之前，需要进行一些预备研究，例如对磁共振相关电子流效应（ESE）的研究。
为前瞻性研究ESE，对11例在1.5T MRL上接受部分乳腺照射（PBI）治疗的患者的数据进行评估。在患者下巴处放置一个匀整器，并将剂量测定结果与治疗计划系统（TPS）模拟的剂量进行比较。对在传统直线加速器上治疗的3例患者进行同样的测量。评估毒性和美容效果。
在匀整器上方/下方测量和模拟的中位剂量分别为1.91 / 0.62 Gy和2.82 / 0.63 Gy。计算值与测量值之间的中位差异分别为0.8 Gy和0.1 Gy。在传统直线加速器上，匀整器上方/下方的中位测量剂量分别为0.98和1.37 Gy。未记录到超过2级的急性毒性。美容效果良好或极佳，患者报告的结局指标大多评分为无或轻度。
ESE导致的剂量较低，TPS能正确预测，且通过匀整器可有效将其最小化。
