Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
J Appl Clin Med Phys. 2023 Apr;24(4):e13918. doi: 10.1002/acm2.13918. Epub 2023 Feb 2.
Ethos CBCT-based adaptive radiotherapy (ART) system can generate an online adaptive plan by re-optimizing the initial reference plan based on the patient anatomy at the treatment. The optimization process is fully automated without any room for human intervention. Due to the change in anatomy, the ART plan can be significantly different from the initial plan in terms of plan parameters such as the aperture shapes and number of monitor units (MUs). In this study, we investigated the feasibility of using calculation-based patient specific QA for ART plans in conjunction with measurement-based and calculation-based QA for initial plans to establish an action level for the online ART patient-specific QA.
A cohort of 98 cases treated on CBCT-based ART system were collected for this study. We performed measurement-based QA using ArcCheck and calculation-based QA using Mobius for both the initial plan and the ART plan for analysis. For online the ART plan, Mobius calculation was conducted prior to the delivery, while ArcCheck measurement was delivered on the same day after the treatment. We first investigated the modulation factors (MFs) and MU numbers of the initial plans and ART plans, respectively. The γ passing rates of initial and ART plan QA were analyzed. Then action limits were derived for QA calculation and measurement for both initial and online ART plans, respectively, from 30 randomly selected patient cases, and were evaluated using the other 68 patient cases.
The difference in MF between initial plan and ART-plan was 12.9% ± 12.7% which demonstrates their significant difference in plan parameters. Based on the patient QA results, pre-treatment calculation and measurement results are generally well aligned with ArcCheck measurement results for online ART plans, illustrating their feasibility as an indicator of failure in online ART QA measurements. Furthermore, using 30 randomly selected patient cases, the γ analysis action limit derived for initial plans and ART plans are 89.6% and 90.4% in ArcCheck QA (2%/2 mm) and are 92.4% and 93.6% in Mobius QA(3%/2 mm), respectively. According to the calculated action limits, the ArcCheck measurements for all the initial and ART plans passed QA successfully while the Mobius calculation action limits flagged seven and four failure cases respectively for initial plans and ART plans, respectively.
An ART plan can be substantially different from the initial plan, and therefore a separate session of ART plan QA is needed to ensure treatment safety and quality. The pre-treatment QA calculation via Mobius can serve as a reliable indicator of failure in online ART plan QA. However, given that Ethos ART system is still relatively new, ArcCheck measurement of initial plan is still in practice. It may be skipped as we gain more experience and have better understanding of the system.
Ethos CBCT 基于自适应放疗（ART）系统可以通过基于治疗时患者解剖结构重新优化初始参考计划来生成在线自适应计划。优化过程是全自动的，无需人为干预。由于解剖结构的变化，ART 计划在计划参数方面（如孔径形状和监控器单位数量（MUs））可能与初始计划有很大的不同。在这项研究中，我们研究了使用基于计算的患者特定质量保证（QA）来结合基于测量和基于计算的初始计划 QA 为 ART 计划建立在线 ART 患者特定 QA 的行动水平的可行性。
本研究收集了 98 例基于 CBCT 的 ART 系统治疗的病例。我们使用 ArcCheck 进行基于测量的 QA，并使用 Mobius 进行基于计算的 QA，分别对初始计划和 ART 计划进行分析。对于在线 ART 计划，在治疗前进行 Mobius 计算，而在治疗当天进行 ArcCheck 测量。我们首先分别研究了初始计划和 ART 计划的调制因子（MF）和 MU 数量。分析了初始和 ART 计划 QA 的γ通过率。然后，从 30 例随机选择的患者病例中分别为初始和在线 ART 计划的 QA 计算和测量得出行动限值，并使用其他 68 例患者病例进行评估。
初始计划和 ART 计划之间的 MF 差异为 12.9%±12.7%，表明它们在计划参数方面存在显著差异。基于患者 QA 结果，治疗前计算和测量结果与在线 ART 计划的 ArcCheck 测量结果基本一致，表明它们作为在线 ART QA 测量失败的指标具有可行性。此外，使用 30 例随机选择的患者病例，初始计划和 ART 计划的γ分析行动限值分别为 89.6%和 90.4%（ArcCheck QA：2%/2mm）和 92.4%和 93.6%（Mobius QA：3%/2mm）。根据计算得出的行动限值，所有初始和 ART 计划的 ArcCheck 测量均通过 QA，而 Mobius 计算行动限值分别标记了初始计划和 ART 计划的 7 个和 4 个失败病例。
ART 计划可能与初始计划有很大的不同，因此需要单独进行 ART 计划 QA 以确保治疗的安全性和质量。通过 Mobius 进行治疗前 QA 计算可以作为在线 ART 计划 QA 失败的可靠指标。然而，鉴于 Ethos ART 系统仍然相对较新，初始计划的 ArcCheck 测量仍在实践中。随着我们获得更多经验并对系统有了更好的理解，它可能会被跳过。
