Key Laboratory of Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, China.
Department of Radiation Oncology, Radiation Oncology Key Laboratory of Sichuan Province, Sichuan Cancer Hospital & Institute, Chengdu, China.
J Appl Clin Med Phys. 2019 Oct;20(10):43-52. doi: 10.1002/acm2.12712. Epub 2019 Sep 21.
Postmastectomy radiation therapy is technically difficult and can be considered one of the most complex techniques concerning patient setup reproducibility. Slight patient setup variations - particularly when high-conformal treatment techniques are used - can adversely affect the accuracy of the delivered dose and the patient outcome. This research aims to investigate the inter-fraction setup variations occurring in two different scenarios of clinical practice: at the reference and at the current patient setups, when an image-guided system is used or not used, respectively. The results were used with the secondary aim of assessing the robustness of the patient setup procedure in use. Forty eight patients treated with volumetric modulated arc and intensity modulated therapies were included in this study. EPID-based in vivo dosimetry (IVD) was performed at the reference setup concomitantly with the weekly cone beam computed tomography acquisition and during the daily current setup. Three indices were analyzed: the ratio between the reconstructed and planned isocenter doses, % and the mean value of from a transit dosimetry based on a two-dimensional -analysis of the electronic portal images using 5% and 5 mm as dose difference and distance to agreement gamma criteria; they were considered in tolerance if was within 5%, % > 90% and < 0.4. One thousand and sixteen EPID-based IVD were analyzed and 6.3% resulted out of the tolerance level. Setup errors represented the main cause of this off tolerance with an occurrence rate of 72.2%. The percentage of results out of tolerance obtained at the current setup was three times greater (9.5% vs 3.1%) than the one obtained at the reference setup, indicating weaknesses in the setup procedure. This study highlights an EPID-based IVD system's utility in the radiotherapy routine as part of the patient's treatment quality controls and to optimize (or confirm) the performed setup procedures' accuracy.
术后放疗技术难度较大，可以被认为是与患者摆位重复性相关的最复杂技术之一。即使采用高适形治疗技术，患者摆位的轻微变化也可能会对剂量的准确性和患者的治疗效果产生不利影响。 本研究旨在分别在使用和不使用图像引导系统的参考和当前患者摆位两种临床情况下，研究分次间摆位变化。该研究的结果还用于评估当前使用的患者摆位程序的稳健性。本研究共纳入了 48 例接受容积调强弧形和调强治疗的患者。在参考摆位时同时进行基于 EPID 的体内剂量测量（IVD），每周采集锥形束 CT 数据，并在日常的当前摆位时进行测量。分析了三个指标：重建与计划等中心剂量的比值（ ）、 ％ 和基于二维 的剂量传输测量（通过对电子射野影像的 5 ％和 5mm 剂量差异和符合度距离的 -分析）的平均值（ ）；当 在 5％以内， ％>90％， ＜0.4 时，认为结果在容差范围内。共分析了 1016 次基于 EPID 的 IVD，其中 6.3％超出容差。摆位误差是超出容差的主要原因，发生率为 72.2％。与参考摆位相比，当前摆位超出容限的结果百分比（9.5％比 3.1％）高了三倍，这表明摆位程序存在弱点。本研究突出了基于 EPID 的 IVD 系统在放射治疗常规中的实用性，可作为患者治疗质量控制的一部分，并优化（或确认）已执行的摆位程序的准确性。
