目的:该研究通过三种先进的加速器的日志文件评估了叶片定位偏差的差异,并建立了不同类型加速器叶片定位偏差的具体评估参数。
方法:从三部曲中收集了总共420个治疗计划和5个连续的治疗日志文件,TrueBeam和Halcyon加速器。MillenniumMLC配备了三部曲和TrueBeam加速器。在Halcyon加速器上采用了无锯齿设计和双层MLC。在每个加速器上随机选择70个IMRT和70个VMAT计划。所有计划的治疗部位包括头颈部,胸部,乳房,骨盆和其他部位。2100个日志文件的解析任务由Sun核公司的SunCheck软件进行。最大叶均方根(RMS)误差,对第95百分位误差和不同叶片定位误差的百分比进行统计分析。这些评估参数与加速器性能参数(最大叶片速度,平均叶片速度,机架和弧角)进行了分析。
结果:在IMRT和VMAT计划中,三部曲的平均最大叶片RMS误差为0.44±0.09mm和0.79±0.07mm,分别,高于TrueBeam的0.03±0.01毫米,0.03±0.01毫米,Halcyon的0.05±0.01毫米,0.07±0.01mm。在第95百分位数误差中显示了类似的数据结果。最大叶片RMS误差与第95百分位数误差密切相关(皮尔逊指数>0.5)。对于所有加速器,VMAT中的叶片定位偏差均高于IMRT中的叶片定位偏差。在TrueBeam和Halcyon,在IMRT和VMAT计划中未发现1毫米以上的叶片位置误差。叶片定位偏差的主要影响因素是叶片速度,与机架和弧角没有很强的相关性。
结论:与质量保证指南相比,应拧紧三个加速器的MLC定位偏差公差。对于IMRT和VMAT技术,对于三部曲加速器,建议将第95百分位误差和最大RMS误差分别收紧至1.5和1mm。在TrueBeam和Halcyon加速器中,第95百分位误差和最大RMS误差为1和0.5mm,分别,被认为是合适的。
OBJECTIVE: The study evaluated the differences in leaf positioning deviations by the log files of three advanced accelerators with two delivery techniques, and established specific assessment parameters of leaf positioning deviations for different types of accelerators.
METHODS: A total of 420 treatment plans with 5 consecutive treatment log files were collected from the Trilogy,
TrueBeam and Halcyon accelerators. Millennium MLC was equipped on the Trilogy and
TrueBeam accelerators. A jawless design and dual-layer MLC were adopted on the Halcyon accelerator. 70 IMRT and 70 VMAT plans were selected randomly on each accelerator. The treatment sites of all plans included head and neck, chest, breast, pelvis and other sites. The parsing tasks for 2100 log files were proceeded by SunCheck software from Sun Nuclear Corporation. The maximum leaf root mean square (RMS) errors, 95th percentile errors and percentages of different leaf positioning errors were statistically analyzed. The correlations between these evaluation parameters and accelerator performance parameters (maximum leaf speed, mean leaf speed, gantry and arc angle) were analyzed.
RESULTS: The average maximum leaf RMS errors of the Trilogy in the IMRT and VMAT plans were 0.44 ± 0.09 mm and 0.79 ± 0.07 mm, respectively, which were higher than the
TrueBeam\'s 0.03 ± 0.01 mm, 0.03 ± 0.01 mm and the Halcyon\'s 0.05 ± 0.01 mm, 0.07 ± 0.01 mm. Similar data results were shown in the 95th percentile error. The maximum leaf RMS errors were strongly correlated with the 95th percentile errors (Pearson index > 0.5). The leaf positioning deviations in VMAT were higher than those in IMRT for all accelerators. In
TrueBeam and Halcyon, leaf position errors above 1 mm were not found in IMRT and VMAT plans. The main influencing factor of leaf positioning deviation was the leaf speed, which has no strong correlation with gantry and arc angles.
CONCLUSIONS: Compared with the quality assurance guidelines, the MLC positioning deviations tolerances of the three accelerators should be tightened. For both IMRT and VMAT techniques, the 95th percentile error and the maximum RMS error are suggested to be tightened to 1.5 and 1 mm respectively for the Trilogy accelerator. In
TrueBeam and Halcyon accelerators, the 95th percentile error and maximum RMS error of 1 and 0.5 mm, respectively, are considered appropriate.