Cheon Wonjoong, Lee Young Kyu, Seol Yunji, Park Chan-Beom, Tan Hong Qi, Choi Kyu Hye, Kang Young-Nam, Choi Byung Ock
Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.
Department of Radiation Oncology, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Republic of Korea.
J Appl Clin Med Phys. 2025 Jul;26(7):e70101. doi: 10.1002/acm2.70101. Epub 2025 Apr 8.
As medical linear accelerator technology advances, enabling higher dose rate deliveries, hypofractionation regimens has increased. This necessitates respiratory gating systems that synchronize radiation delivery with tumor position, requiring simple rigorous quality assurance (QA) to ensure treatment accuracy and patient safety.
This study aimed to propose log-based QA for respiratory-gated radiation therapy using the respiratory gating system and treatment machine.
4D CT scans were performed with a Varian motion phantom using a Varian Respiratory Gating for Scanner (RGSC). A treatment plan using 25%-75% respiratory phases with 100 MU was created and delivered to a solid water phantom. Treatment logs containing respiratory signals, beam on/off flags, and frame information were extracted from the treatment planning system's offline review. Log file analyses were conducted using in-house softwares to assess temporal synchronization between respiratory phases and beam triggers. Output measurements using a calibrated ion chamber (FC65G) were performed to evaluate dosimetric accuracy. Additionally, EPID images were acquired in cine mode and analyzed frame-by-frame to independently verify beam delivery timing.
Log file analysis revealed precise temporal synchronization, with mean time differences of 0.03 s ± 0.05 s between the planned 25% phase and beam-on, and -0.04 s ± 0.05 s between 75% phase and beam-off. The log-derived beam-on duration (2.61 s ± 0.02 s) closely matched the planned duration (2.66 s ± 0.00 s). Three-month log data showed consistent temporal accuracy, with trigger-on times remaining stable at 2.60 s ± 0.01 s across all measurements. Supporting ion chamber measurements confirmed dosimetric agreement between gating and non-gating modes (difference: 0.05 cGy ± 0.09 cGy) CONCLUSIONS: The proposed log file-based QA method demonstrated high accuracy and reproducibility in assessing respiratory gating performance. This approach provides an efficient, objective method for standardizing QA procedures in respiratory-gated radiation therapy, enhancing treatment accuracy and patient safety.
随着医用直线加速器技术的进步，能够实现更高剂量率的照射，大分割放疗方案有所增加。这就需要呼吸门控系统将放疗与肿瘤位置同步，需要进行简单而严格的质量保证（QA）以确保治疗准确性和患者安全。
本研究旨在提出使用呼吸门控系统和治疗机器对呼吸门控放射治疗进行基于日志的质量保证。
使用瓦里安呼吸门控扫描器（RGSC）对瓦里安运动体模进行4D CT扫描。创建一个使用25%-75%呼吸相位且剂量为100 MU的治疗计划，并将其施用于固体水模体。从治疗计划系统的离线审查中提取包含呼吸信号、射束开/关标志和帧信息的治疗日志。使用内部软件进行日志文件分析，以评估呼吸相位与射束触发之间的时间同步。使用校准的电离室（FC65G）进行输出测量，以评估剂量准确性。此外，以电影模式采集EPID图像并逐帧分析，以独立验证射束输出时间。
日志文件分析显示时间同步精确，计划的25%相位与射束开启之间的平均时间差为0.03 s±0.05 s，75%相位与射束关闭之间的平均时间差为-0.04 s±0.05 s。日志得出的射束开启持续时间（2.61 s±0.02 s）与计划持续时间（2.66 s±0.00 s）密切匹配。三个月的日志数据显示时间准确性一致，所有测量中触发开启时间稳定在2.60 s±0.01 s。支持性的电离室测量证实了门控模式与非门控模式之间的剂量一致性（差异：0.05 cGy±0.09 cGy）。结论：所提出的基于日志文件的质量保证方法在评估呼吸门控性能方面显示出高准确性和可重复性。这种方法为呼吸门控放射治疗的质量保证程序标准化提供了一种高效、客观的方法，提高了治疗准确性和患者安全性。
