Z. Chen , M.F. Moyers , Y. Deng , H.L. Chen , J. Li , Z.M. Shen , J. Lin , Q. Wang , P. Yepes
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引用次数: 2
Abstract
Objective
A procedure has been proposed for patient-specific QA that, instead of comparing a measurement to the planned dose, compares the dose calculated by an independent system to the dose calculated by the planning system. It is still prudent, however, to check the accuracy of the beam delivery. For this purpose, the DICOM records from the first treatment fraction can be compared to the planned treatment using an in-house developed planning system.
Methods
Totally 1,398 patient portals were subjected to the new QA procedure. The dose distribution for each portal was first recalculated on a water phantom by two treatment planning systems and the dose distributions were compared. When agreement was observed, the patient was allowed to start treatment without a measurement. The record from the first day was imported into an in-house planning system which was used to evaluate the delivery for errors and calculate the delivered dose distribution and compare it to the planned dose distribution.
Results
A total of 266 portals passed a strict comparison between the clinical and QA dose calculations and directly used for treatment without measurements. For those portals, the comparison of the delivery records to the plan showed that 99% of spot positions deviated less than 0.2 mm and 99.7% of spot metersets deviated by less than 0.3%. On the other hand, 64 portals showed spot size deviations greater than the tolerance of ± 15% with some as large as ±25%. For 32 portals in which the record was used to calculate the delivered dose distribution, the Gamma passing rates between the planned and delivered distributions were always above 95% using a 2% dose difference and 2 mm distance-to-agreement criteria.
Conclusions
The new QA process has been implemented slowly with strict constraints. The amount of beam time required has been reduced while maintaining safety.
目的提出了一种针对患者的质量保证程序，该程序不是将测量值与计划剂量进行比较，而是将独立系统计算的剂量与计划系统计算的剂量进行比较。然而，检查光束传送的准确性仍然是谨慎的。为此，可以使用内部开发的计划系统将第一次处理段的DICOM记录与计划处理进行比较。方法采用新质量保证程序对1398例患者进行质量保证。首先通过两种治疗计划系统在水影上重新计算每个入口的剂量分布，并比较剂量分布。当观察到一致时，允许患者开始治疗而不进行测量。第一天的记录被输入到一个内部计划系统中，该系统用于评估交付的错误，计算交付的剂量分布，并将其与计划的剂量分布进行比较。结果266个入口通过了临床剂量计算与QA剂量计算的严格比较，不经测量直接用于治疗。对这些门户网站，将交货记录与计划进行比较，发现99%的站点位置偏差小于0.2 mm, 99.7%的站点测量偏差小于0.3%。另一方面，64个孔的斑点尺寸偏差大于±15%的公差，有的大到±25%。对于使用记录计算递送剂量分布的32个入口，使用2%的剂量差和2mm距离-一致性标准，计划和递送分布之间的Gamma通过率始终在95%以上。结论新的质量保证流程在严格的约束下实施缓慢。在保持安全的同时，减少了所需的梁时间。
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