头颅CT偏中心定位对扫描图像质量的影响  

Effect of Miscentering Location on Image Quality in Computed Tomography for Head

作　　者：韩林梅[1] 俞琴[1] HAN Linmei;YU Qin(Department of CT/MRI,No.7 Peoples Hospital of Chengdu,Chengdu 610041,P.R.China)

机构地区：[1]成都市第七人民医院CT/MRI室

出　　处：《临床放射学杂志》2019年第12期2420-2424,共5页Journal of Clinical Radiology

摘　　要：目的探讨头颅CT偏中心定位对扫描图像质量的影响,以期为头颅扫描定位规范化的必要性提供理论依据。方法使用GE公司提供的标准头颅水模在GE LIGHTSPEED 64 VCT进行头颅CT扫描,通过对检查床高度的调整,模拟实现偏中心情况。将偏下(最低位置)、偏上(最高位置)、视野(FOV)低位临界位置、FOV高位临界位置及ISO中心位置分别记录为A^E组。对A^E组分别使用HEAD FOV模式和MEDIUM FOV模式进行轴扫及螺旋扫描,螺旋扫描记为A'~E'组,HEAD FOV模式FOV大小为25 cm和32 cm,MEDIUM FOV模式FOV大小为25 cm、32 cm和36 cm。对A^E每组第2幅图像选取3个距ISO中心远近不同的感兴趣区(ROI)对其CT值进行测量,计算其信噪比(SNR)及噪声水平(SD)。结果采用SPSS 17.0软件进行统计分析,A^C组两种模式下不同的ROI SNR及SD差异有统计学意义(P<0.05),D、E组差异无统计学意义(P>0.05),ROI中心SNR比ROI偏中心SNR高达40.27%,ROI偏中心SD比ROI中心高达46.28%。结论偏中心定位会导致扫描图像SNR下降、SD水平升高,要能得到最优的图像质量和最低的辐射剂量须将头颅定位于ISO中心,且须使用HEAD FOV扫描模式。Objective To investigate the effect of head CT off-center positioning on the quality of scan images,and to provide a theoretical basis for the necessity of standardized head scan positioning.Methods The head CT scan was per-formed on GE LIGHTSPEED 64 VCT using a standard head water model provided by GE.The height of the examination ta-ble was adjusted to simulate the off-center position.Record the lower(lowest position),upper(highest position),FOV low critical position,FOV high critical position and ISO center position as A B C D E group,respectively.For group A^E,use HEAD FOV mode and MEDIUM FOV mode for axial scan and helical scan.The helical scan is recorded as A'B'C'D'E'group.The head FOV mode FOV size is 25 cm and 32 cm.FOV sizes are 25 cm,32 cm and 36 cm.For the second im-age of each group of A^E,three areas of interest with different distances from theisocenter were selected to measure its CT value,and its signal-to-noise ratio and noise level were calculated.Results Using SPSS17.0 statistical analysis,the differences in SNR and SD of different regions of interest in the two modes of group A^C were statistically significant(P<0.05),and the differences in group D and E were not statistically significant(P>0.05).In the central region of inter-est the SNR is as high as 40.27%off-center,and the SD on the off-center area ofinterest is 46.28%.Conclusion Off-center positioning will cause the SNR of the scanned image to decrease and the SD level to increase.To obtain the best im-age quality and the lowest radiation dose,the head must be positioned at the isocenter,and the HEAD FOV scanning mode must be used.

关 键 词：偏中心 信噪比 噪声水平 图像质量 

分 类 号：R816.1[医药卫生—放射医学]