Key laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China.
Institute of Medical Technology, Peking University Health Science Center, Beijing, China.
J Appl Clin Med Phys. 2024 Aug;25(8):e14376. doi: 10.1002/acm2.14376. Epub 2024 May 2.
To propose a straightforward and time-efficient quality assurance (QA) approach of beam time delay for respiratory-gated radiotherapy and validate the proposed method on typical respiratory gating systems, Catalyst™ and AlignRT™.
The QA apparatus was composed of a motion platform and a Winston-Lutz cube phantom (WL3) embedded with metal balls. The apparatus was first scanned in CT-Sim and two types of QA plans specific for beam on and beam off time delay, respectively, were designed. Static reference images and motion testing images of the WL3 cube were acquired with EPID. By comparing the position differences of the embedded metal balls in the motion and reference images, beam time delays were determined. The proposed approach was validated on three linacs with either Catalyst™ or AlignRT™ respiratory gating systems. To investigate the impact of energy and dose rate on beam time delay, a range of QA plans with Eclipse (V15.7) were devised with varying energy and dose rates.
For all energies, the beam on time delays in AlignRT™ V6.3.226, AlignRT™ V7.1.1, and Catalyst™ were 92.13 5.79 ms, 123.11 6.44 ms, and 303.44 4.28 ms, respectively. The beam off time delays in AlignRT™ V6.3.226, AlignRT™ V7.1.1, and Catalyst™ were 121.87 1.34 ms, 119.33 0.75 ms, and 97.69 2.02 ms, respectively. Furthermore, the beam on delays decreased slightly as dose rates increased for all gating systems, whereas the beam off delays remained unaffected.
The validation results demonstrate the proposed QA approach of beam time delay for respiratory-gated radiotherapy was both reproducible and time-efficient to practice for institutions to customize accordingly.
提出一种简单、省时的呼吸门控放射治疗的光束时滞质量保证（QA）方法，并验证该方法在典型的呼吸门控系统 CatalystTM 和 AlignRT™ 上的有效性。
QA 设备由运动平台和一个内置金属球的 Winston-Lutz 立方模体（WL3）组成。该设备首先在 CT-Sim 中进行扫描，并分别设计了两种特定于光束开启和关闭时滞的 QA 计划。EPID 采集 WL3 立方模体的静态参考图像和运动测试图像。通过比较运动和参考图像中嵌入金属球的位置差异，确定光束时滞。该方法在三台配备 Catalyst™ 或 AlignRT™ 呼吸门控系统的直线加速器上进行了验证。为了研究能量和剂量率对光束时滞的影响，使用 Eclipse（V15.7）设计了一系列具有不同能量和剂量率的 QA 计划。
对于所有能量，AlignRT™ V6.3.226、AlignRT™ V7.1.1 和 Catalyst™ 的光束开启时滞分别为 92.13 5.79ms、123.11 6.44ms 和 303.44 4.28ms。AlignRT™ V6.3.226、AlignRT™ V7.1.1 和 Catalyst™ 的光束关闭时滞分别为 121.87 1.34ms、119.33 0.75ms 和 97.69 2.02ms。此外，对于所有的门控系统，随着剂量率的增加，光束开启延迟略有减小，而光束关闭延迟不受影响。
验证结果表明，该方法对于呼吸门控放射治疗的光束时滞 QA 是一种可重复且省时的方法，机构可以根据需要进行定制。
