西门子Sensation OpenCT模拟机CT值稳定性分析

Study on constancy of CT numbers of SIEMENS Sensation Open CT-simulator

目的 分析QC模体检测得到的7种物质的CT值,评估西门子Sensation Open CT模拟机CT值的稳定性。方法 使用Catphan 504模体定期对西门子Sensation Open CT模拟机进行QC检测。使用头部常规序列（HeadSeq）、放疗头部（RT_Head）和放疗腹部（RT_Abdomen）3种扫描协议辅助模体中的CTP404模块获取CT图像。使用DoseLab软件对2014—2015年间收集的72张CT图像进行分析,获取每种物质CT值（记为Y）,并对其进行统计分析。通过计算得到3种扫描协议下7种物质Y值的平均值、标准差、最大值、最小值和极差。结果 模块中空气、聚甲基戊烯、低密度聚乙烯、聚苯乙烯、丙烯酸、聚甲醛树酯、聚四氟乙烯标准差HeadSeq的分别为0.54、0.60、0.82、0.58、0.75、0.66、1.83 HU,RT_Head的分别0.08、0.69、0.86、0.66、0.80、0.89、2.49 HU,RT_Abdomen的分别为0.11、0.61、0.76、0.72、0.78、0.96、2.56 HU。在2年时间里西门子Sensation Open CT模拟机CT值较为稳定。结论 7种物质相比较,Teflon的CT值变化最大。不同扫描协议CT值的相对大小随不同物质相对电子密度的大小而变化。

Objective To evaluate the constancy of CT numbers of SIEMENS Sensation Open CT-simulator by analyzing the CT numbers of seven materials obtained from quality assurance （QA） tests. Methods QA tests for SIEMENS Sensation Open CT-simulator were performed with the Catphan504 phantom monthly. The CT images were obtained using three scan protocols （HeadSeq,RT_Head,and RT_Abdomen） for the CTP404 module in the phantom. The DoseLab software was used to analyze the 72 CT images acquired from January 2014 to December 2015,and the CT numbers （Y） of seven materials were obtained. Statistical analysis was performed on the Y data. The mean,standard deviation,maximum,minimum,and range values of Y for seven materials were calculated in three scan protocols. Results The standard deviation values of air,polymethylpentene,low-density polyethylene,polystyrene,acrylic acid,polyoxymethylene resin （Delrin）,and polytetrafluoroethylene （Teflon） were as follows：（1） HeadSeq：0.54,0.60,0.82,0.58,0.75,0.66,and 1.83 HU;（2） RT_Head：0.08,0.69,0.86,0.66,0.80,0.89,and 2.49 HU;（3） RT_Abdomen：0.11,0.61,0.76,0.72,0.78,0.96,and 2.56 HU. According to the statistical data,the constancy of CT numbers of the SIEMENS Sensation Open CT-simulator was in good condition in two years. Conclusions The variation of CT numbers of Teflon is the biggest among the seven materials. The relative values of CT numbers between different scan protocols vary with the relative electron density of materials.