模拟定位CT的机型及扫描参数对CT值和噪声的影响

摘要

Objective To evaluate the impact of different types of CT simulators and scanning parameters on CT values and image noise.Methods The CIRS-062M electron density phantom was scanned with 3 different CT simulators,namely Siemens SOMATOM Definition AS,Philips Briliance Big Bore,and GE Discovery CT590 RT,and the CT value-electron density (CT-ED) curves were established to compare the scanning results.With different scanning parameter settings,Siemens SOMATOM Definition AS was used to scan the CIRS-062M electron density phantom to analyze the effect of tube voltage,tube current,slice thickness,reconstruction algorithm,and position of the phantom in the gantry on CT value and image noise.Results The 3 CT scanners showed only trivial differences in the CT values of the low-density phantoms of the tissue-equivalent inserts,but the differences were obvious in high-density phantoms;the image noise was comparable among the 3 CT scanners.Variations of the tube voltage produced significant effects on the CT values of high-density phantoms and on the image noise;the scanning position affected the CT values of tissue-equivalent inserts but not the image noise.Variations in the tube current,slice thickness,or reconstruction algorithm did not obviously affect the CT-ED curves,but produced significant effects on image noise.Conclusion The type of CT scanners and scanning parameters setting can affect the accuracy of the CT value.Appropriate quality assurance and control measures should be implemented in routine CT simulations.%目的:探讨模拟定位CT的机型及扫描参数对CT值和噪声的影响.方法:分别使用Siemens SOMATOM Definition AS、Philips Briliance Big Bore和GE Discovery CT590 RT CT模拟定位机扫描CIRS-062M电子密度模体,建立CT值-电子密度曲线,比较不同CT机的扫描结果;使用Siemens SOMATOM Definition AS型CT模拟定位机采用不同扫描参数对CIRS-062M电子密度模体进行扫描,分析管电压、管电流、扫描层厚、重建算法、扫描位置对CT值和噪声的影响.结果:不同CT模拟定位机得到的各组织等效插件的CT值在低密度部分基本一致,高密度部分差异较大,图像噪声差异不明显;管电压对高密度组织的CT值及图像噪声影响显著;扫描位置对各组织等效插件的CT值有不同程度的影响,对图像噪声影响不明显;管电流、扫描层厚、重建算法对CT值-电子密度曲线影响不大,但对噪声的影响较显著.结论:CT机型和扫描参数会影响CT值的准确性,模拟定位时需要严谨的质量保证和控制措施.