螺旋CT图像噪声影响因素的实验分析

Helical CT image noise :experimental study of influencing factors

目的 通过实验,分析影响CT图像噪声的因素及其原因。方法 应用GEHispeedCTi及其附带QA体模1套。采用不同直径模体,不同的mA值、kV值、层厚、螺距、扫描时间、重建算法、重建矩阵和重建视野等扫描参数,分别进行螺旋和轴面扫描,测量其标准偏差并分析。结果 CT图像噪声随着mA值、kV值、层厚、扫描时间、重建视野的增大而减小,随着体模直径、重建矩阵的增大而增大;图像噪声与mAs的平方根、层厚的平方根均成反比;高分辨重建算法引起较大噪声;多数情况下,螺旋扫描图像噪声略大于相应轴面扫描图像。其他条件相同时,螺距越大,噪声越大。结论影响CT图像噪声的因素很多,正确全面地理解,对于做好CT的QA、QC工作,对于正确评价、比较CT性能十分重要。

Objective TostudytheinfluencingfactorsofhelicalCTimagenoisebyexperimental analysis.Methods GEHispeedCTihelicalCTscanneranditsQAphantomswereemployed .Withdifferent phantoms,axialandhelicalscanweredonewithdifferentscanparametersincludingmA ,kV ,slicethickness , scantime ,reconstructionalgorithm ,matrixandFOV ,andalloftheseCTstandarddeviationweremeasuredand analyzed.Results ThenoisedecreasedwithmA ,kV ,slicethickness,scantimeandFOV ,increasedwith matrixanddiameterofthephantoms .ThenoisewasinverselyrelatedwiththesquarerootofmAs,andthesquare rootofslicethickness .Thereconstructionalgorithmofhighresolutionresultedinhighernoise.Mostly,helical imagenoisewashigherthanthatofaxialscan .Underthesameotherscanparameters,thebiggerpitchresultedin highernoise .Conclusion TheCTimagenoiseisinfluencedbymanyfactors.Itisveryimportanttounderstand andexplainthesefactors ,becauseitisrelatedtoQAandQC ,andbetterperformanceofCT .