Abstract：
OBJECTIVE: We aimed to show the framework of the six-sigma methodology (SSM) that can be used to determine the limits of QC tests for the linear accelerator (Linac). Limits for QC tests are individually determined using the SSM.
METHODS: The SSM is based on the define-measure-analyze-improve-control (DMAIC) stages to improve the process. In the \"define\" stage, the limits of QC tests were determined. In the \"measure\" stage, a retrospective collection of daily QC data using a Machine Performance Check platform was performed from January 2020 to December 2022. In the \"analyze\" stage, the process of determining the limits was proposed using statistical analyses and process capability indices. In the \"improve\" stage, the capability index was used to calculate the action limits. The tolerance limit was established using the larger one of the control limits in the individual control chart (I-chart). In the \"control\" stage, daily QC data were collected prospectively from January 2023 to May 2023 to monitor the effect of action limits and tolerance limits.
RESULTS: A total of 798 sets of QC data including beam, isocenter, collimation, couch, and gantry tests were collected and analyzed. The Collimation Rotation offset test had the min-Cp, min-Cpk, min-Pp, and min-Ppk at 2.53, 1.99, 1.59, and 1.25, respectively. The Couch Rtn test had the max-Cp, max-Cpk, max-Pp, and max-Ppk at 31.5, 29.9, 23.4, and 22.2, respectively. There are three QC tests with higher action limits than the original tolerance. Some data on the I-chart of the beam output change, isocenter KV offset, and jaw X1 exceeded the lower tolerance and action limit, which indicated that a system deviation occurred and reminded the physicist to take action to improve the process.
CONCLUSIONS: The SSM is an excellent framework to use in determining the limits of QC tests. The process capability index is an important parameter that provides quantitative information on determining the limits of QC tests.
METHODS: The SSM is based on the define-measure-analyze-improve-control (DMAIC) stages to improve the process. In the \"define\" stage, the limits of QC tests were determined. In the \"measure\" stage, a retrospective collection of daily QC data using a Machine Performance Check platform was performed from January 2020 to December 2022. In the \"analyze\" stage, the process of determining the limits was proposed using statistical analyses and process capability indices. In the \"improve\" stage, the capability index was used to calculate the action limits. The tolerance limit was established using the larger one of the control limits in the individual control chart (I-chart). In the \"control\" stage, daily QC data were collected prospectively from January 2023 to May 2023 to monitor the effect of action limits and tolerance limits.
RESULTS: A total of 798 sets of QC data including beam, isocenter, collimation, couch, and gantry tests were collected and analyzed. The Collimation Rotation offset test had the min-Cp, min-Cpk, min-Pp, and min-Ppk at 2.53, 1.99, 1.59, and 1.25, respectively. The Couch Rtn test had the max-Cp, max-Cpk, max-Pp, and max-Ppk at 31.5, 29.9, 23.4, and 22.2, respectively. There are three QC tests with higher action limits than the original tolerance. Some data on the I-chart of the beam output change, isocenter KV offset, and jaw X1 exceeded the lower tolerance and action limit, which indicated that a system deviation occurred and reminded the physicist to take action to improve the process.
CONCLUSIONS: The SSM is an excellent framework to use in determining the limits of QC tests. The process capability index is an important parameter that provides quantitative information on determining the limits of QC tests.
摘要：
目的：我们旨在展示六西格玛方法学（SSM）的框架，该框架可用于确定线性加速器（直线加速器）的QC测试极限。使用SSM单独确定QC测试的限制。
方法：SSM基于定义-测量-分析-改进-控制（DMAIC）阶段来改进过程。在“定义”阶段，确定了QC测试的极限。在“测量”阶段，从2020年1月至2022年12月,使用机器性能检查平台对日常QC数据进行回顾性收集.在“分析”阶段，使用统计分析和过程能力指数提出了确定极限的过程。在“改善”阶段，能力指数被用来计算行动极限。使用单个控制图（I-chart）中较大的一个控制极限来建立公差极限。在“控制”阶段，我们前瞻性地收集了2023年1月至2023年5月的每日质量控制数据,以监测作用限度和耐受限度的影响.
结果：总共798套QC数据，包括梁，等中心,准直,沙发,和龙门测试进行了收集和分析。准直旋转偏移测试的最小Cp，min-Cpk,min-Pp,和min-Ppk分别为2.53、1.99、1.59和1.25。CouchRtn测试的最大Cp,max-Cpk,max-Pp,和max-Ppk分别为31.5、29.9、23.4和22.2。有三个QC测试的作用极限高于原始公差。光束输出变化的I形图上的一些数据，等中心KV偏移，并且钳口X1超出了较低的公差和动作极限，这表明系统发生了偏差，并提醒物理学家采取行动改善过程。
结论：SSM是一个很好的框架，可用于确定QC测试的极限。过程能力指数是一个重要的参数，它为确定QC测试的极限提供了定量信息。
方法：SSM基于定义-测量-分析-改进-控制（DMAIC）阶段来改进过程。在“定义”阶段，确定了QC测试的极限。在“测量”阶段，从2020年1月至2022年12月,使用机器性能检查平台对日常QC数据进行回顾性收集.在“分析”阶段，使用统计分析和过程能力指数提出了确定极限的过程。在“改善”阶段，能力指数被用来计算行动极限。使用单个控制图（I-chart）中较大的一个控制极限来建立公差极限。在“控制”阶段，我们前瞻性地收集了2023年1月至2023年5月的每日质量控制数据,以监测作用限度和耐受限度的影响.
结果：总共798套QC数据，包括梁，等中心,准直,沙发,和龙门测试进行了收集和分析。准直旋转偏移测试的最小Cp，min-Cpk,min-Pp,和min-Ppk分别为2.53、1.99、1.59和1.25。CouchRtn测试的最大Cp,max-Cpk,max-Pp,和max-Ppk分别为31.5、29.9、23.4和22.2。有三个QC测试的作用极限高于原始公差。光束输出变化的I形图上的一些数据，等中心KV偏移，并且钳口X1超出了较低的公差和动作极限，这表明系统发生了偏差，并提醒物理学家采取行动改善过程。
结论：SSM是一个很好的框架，可用于确定QC测试的极限。过程能力指数是一个重要的参数，它为确定QC测试的极限提供了定量信息。
