Evaluation of gantry angle during respiratory‐gated VMAT using triggered kilovoltage x‐ray image
Evaluation of gantry angle during respiratory‐gated VMAT using triggered kilovoltage x‐ray image
复制标题
使用触发千伏 X 射线图像评估呼吸门控 VMAT 期间的机架角度
DOI：
10.1002/acm2.12683
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发表时间：
2019
影响因子：
2.1
通讯作者：
Hara Ryusuke
中科院分区：
文献类型：
--
作者：
Miyasaka Ryohei;Saitoh Hidetoshi;Kawachi Toru;Katayose Tetsurou;Cho SangYong;Yamauchi Ryohei;Hara Ryusuke
呼吸门控容积调制弧治疗（门控VMAT）涉及剂量输送过程的进一步复杂性，因为机架旋转必须根据门控信号重复停止和重新开始。在以前的研究中，机架旋转性能是通过计划和机器日志之间的差异来评价的。然而，一些报告指出，日志分析并不能充分复制机器的性能。在本报告中，建议使用触发千伏成像和带有16个滚珠轴承的圆柱体模，对机架角度与门控开启或门控关闭之间的关系进行基于测量的质量保证。为了进行分析，开发了一个估计和校正体模偏移的内部程序。在机器日志和所提出的方法之间比较了静态和门控弧输送中的机架角度。机架在静态输送中的整个运动范围内每5度设置一次，并在门控弧输送中以三种速度（2、4和6度s-1）旋转，门控间隔不同（1.5或3.0 s）。在静态输送中，日志和拟定方法之间的角度差的平均值和标准差为−0.05度± 0.12度。角度差的平均值在±0.10度范围内，门控弧形输送的最大差异为0.41度。日志记录了编码器的输出，因此可以忽略误校准和机械下垂。然而，所提出的方法将帮助用户检测由于门控VMAT中机架重复停止和重新启动而导致的机械问题。
Respiratory‐gated volumetric modulated arc therapy (gated VMAT) involves further complexities to the dose delivery process because the gantry rotation must repeatedly stop and restart according to the gating signals. In previous studies, the gantry rotation performances were evaluated by the difference between the plan and the machine log. However, several reports pointed out that log analysis does not sufficiently replicate the machine performance. In this report, a measurement‐based quality assurance of the relation between the gantry angle and gate‐on or gate‐off using triggered kilovoltage imaging and a cylinder phantom with 16 ball bearings is proposed. For the analysis, an in‐house program that estimates and corrects the phantom offset was developed. The gantry angle in static and gated arc delivery was compared between the machine log and the proposed method. The gantry was set every 5 deg through its full motion range in static delivery, and rotated at three speeds (2, 4 and 6 deg s‐1) with different gating intervals (1.5 or 3.0 s) in gated arc delivery. The mean and standard deviation of the angular differences between the log and the proposed method was −0.05 deg ± 0.12 deg in static delivery. The mean of the angular difference was within ±0.10 deg and the largest difference was 0.41 deg in gated arc delivery. The log records the output of the encoder so that miscalibration and mechanical sagging will be disregarded. However, the proposed method will help the users to detect the mechanical issues due to the repeated gantry stops and restarts in gated VMAT.