基于过程能力的CT设备长期稳定性分析

目的:运用过程能力分析方法对CT设备长期稳定性进行分析。方法:依据国家标准《X射线计算机断层摄影装置质量保证检测规范》(GB17589-2011),利用Minitab 17.0软件对3台CT设备(CT-1、CT-2和CT-3)的长期稳定性进行过程能力分析,检测项目包括水的CT值、均匀性、噪声、CT值线性、低对比度分辨力、CT剂量指数(CTDI_W)和重建层厚偏差。采用时间序列图对空间分辨力进行分析。结果:所有检测项目的测量值均符合GB17589-2011标准限值要求;大部分检测项目的长期质量控制过程处于Ⅱ级及以上水平,且过程性能指数(P_p)≥1.33;重建层厚偏差(s≤2 mm)的过程能力处于Ⅲ级及以下水平(P_p<1.33);CT-3的长期稳定性优于CT-2。结论:通过过程能力分析,可以客观地判断CT性能的长期稳定性情况。对于每台CT设备,通过定期执行稳定性检测,并利用过程能力分析检测结果的变化情况,可以判断其维护保养是否到位,更好的保障设备性能和诊疗质量。

Analysis of long term stability of CT equipment based on process capability

Objective:To analyze the long-term stability of computed tomography(CT)equipment by using the analytical method of process capability.Methods:The analysis of process capability was implemented for long-term stability of 3 CT equipment(CT-1,CT-2 and CT-3)by using Minitab 17.0 according to the national standard(GB 17589-2011).The detection items included the CT value of water,homogeneity,linear of CT value,low contrast resolution,CT dose index(CTDIw)and the deviation of the thickness of rebuilt slice.And then the time sequence chart was adopted to analyze spatial resolution.Results:The measured values of all test items met the requirements of the limiting value of national standard(GB 17589-2011),and the processes of long-term quality control of the most of test items were in II grade and above II grade(Pp≥1.33).The process capability of the deviation(s≤2mm)of rebuilt slice thickness was in III grade and under III grade(Pp<1.33),and the long-term stability of CT-3 was better than that of CT-2.Conclusion:The situation of long-term stability of CT performance can be objectively judged through the analysis of process capability.For each CT equipment,whether its maintenance achieves requirement can be judged through termly performs stability testes and uses process capability to analyze the changing situation of detection results.And these can better guarantee the equipment performance and the qualities of diagnosis and treatment.