MSCT不同机型对辐射剂量及图像质量的影响：GE4层螺旋CT与64层螺旋CT的对照研究  

The effects of different models of MSCT on radiation dose and image quality：experimental contrast research of GE 4slice spiral CT and GE 64slice spiral CT

作　　者：李登维[1] 肖正远[1] 唐光才[1] 兰永树[1] 

机构地区：[1]泸州医学院附属医院CT室,四川泸州646000

出　　处：《实用放射学杂志》2012年第5期767-770,783,共5页Journal of Practical Radiology

基　　金：四川省卫生厅基金资助项目（编号：11048）.

摘　　要：目的 探讨不同的MSCT对辐射剂量及图像质量的影响.方法 采用相同的扫描条件分别以GE 4层螺旋CT（4 SCT）和64层螺旋CT（64 SCT）对质量控制（QA）体模进行轴向扫描和螺旋扫描.扫描后机器生成的辐射剂量数据中有总曝光时间（totime）、CT容积剂量指数（CTDIvol）、剂量长度乘积（DLP）、有效射线率;通过对图像伪影、低对比度分辨率、高对比度分辨率、实际层厚的观察以及对水的CT值及标准偏差、均匀性值的测量来评价图像质量.比较2种机型的辐射剂量和图像质量,并对DLP进行统计学处理.结果 64 SCT螺距因子0.5311的总曝光时间较长,两机器其余组合的总曝光时间比较接近;4 SCT各组合的CTDIvol、DLP较低,而有效射线率更高,但两种机器的DLP无统计学差异（t=1.60,P=0.143）.除4 SCT螺旋扫描外,其余扫描均无明显图像伪影;两机型轴向扫描图像的高对比分辨率均可达20 lp/cm,螺旋扫描略低于20 lp/cm,特别是64 SCT 大螺距因子扫描更低;4 SCT轴向扫描图像的低对比分辨率能可观察到第2小孔,螺旋扫描观察的孔径更大到第5孔,64 SCT能观察到第2小孔;轴向扫描图像的实际层厚更接近于标称层厚,而螺旋扫描则大于标称层厚;两机器水的CT值均在1 HU以内,标准偏差均在5 HU以内,均匀性值均〈1,随层厚的变薄,噪声增加,均匀性值变化不大.结论在相同的扫描条件下,64 SCT的辐射剂量更大、图像质量更高.Objective To discuss the effect of different models of MSCT on radiation dose and image quality. Methods quality assurance（QA） phantom was scanned with the same scanning parameters using GE 4 SCT and 64 SCT scanner. Total exposure time （to-time）, CT dose index （CTDIvol） , dose length product （DLP） , the effective radiation rate were obtained from the machine gen crated information after scanning . The image quality was judged by the parameter such as image artifact ,density resolution ,spatial resolution ,efficient, actual thickness of the observed, CT value of water and standard deviation and uniformity . Tile radiation dose and image quality of two models machine were compared and DLP was analysed with t test . Results Total exposure time of 64 SCT with pitch ratio of 0. 531 ： 1 was longer , the remaining two combinations of the machine were closer . Each combination of 4 SCT had lower CTDIvol , DI.P but higher efficiency of ray . DI.P of the two CT machines with t test was no statistical significance （t= 1.60,P=0.143） . All images had no obvious false shade except 4 SCT helical scans. The spatial resolution of two models with axial scanning could be reached 20 lp/cm , helical scanning was lower than 20 lp/cm , especially 64 SCT with large pitch ratio was even lower. Images of 4 SCT axial scanning could detect the second hole, helical scanning had bigger holes and could detect the fifth hole. Images of 64 SCT scanning could detect the second hole. Valid layer thickness was close m nominal layer thickness at axial scanning, while valid layer thickness was larger than nominal layer thickness at helical scanning. CT values of water in two machines were both less than 1, the standard deviations were less than S, the value, of uniformity were 〈1, the noise increased with the thickness thinning but little change in the value of uniformity. Conclusion 64 SCT scanning produces more radiation dose,hut has higher image quality in comparison with 4 SCT scanning with the same scanning parameters.

关 键 词：辐射剂量 图像质量 体层摄影术 X线计算机 

分 类 号：R812[医药卫生—放射医学] R814.42[医药卫生—临床医学]