颈髓MR扩散加权成像优化b值初步研究

Preliminary study of the optimal b values on diffusion weighted MR imaging of cervical cord

目的:探讨1.5T磁共振颈髓扩散加权成像(DWI)b值的选择及获取正常脊髓表观扩散系数(ADC值)。方法:50例健康志愿者进行颈髄DWI检查,采用单次激发平面回波(SSH-EPI-DWI)序列,扩散梯度因子b值分别取300、500和1000 s/mm2,分3组进行扫描,测量正常人颈髓ADC值并分析各组DWI图像及ADC图像质量,对比不同b值对成像效果的影响。结果:50例受检者均获得较满意的DWI和ADC图像并测得正常人颈髓ADC值。随着b值由300 s/mm2升高到1000 s/mm2,图像信号强度逐渐降低。以b值为500 s/mm2时成像效果较好,信噪比和对比度较高,伪影较少。在500s/mm2时测得的50例正常颈髓的平均ADC值为(95.70±11.01)×10-5mm2/s。结论:利用SSH-EPI-DWI序列,正常人颈髓在b值为500 s/mm2时可获得颈髓较满意的DWI和ADC图像。

Objective：To investigate the optimal b value on diffusion weighted imaging（DWI） of cervical cord at a 1.5T MR scanner and to obtain the apparent diffusion coefficient（ADC） value of normal spinal cord.Methods：Fifty healthy volunteers were included in this study.Single shot echo-planar pulse sequence was employed for DWI of cervical cord,according to different gradient factors b values=300,500 and 1000s/mm^2 were selected and image qualities of the 3 groups were evaluated and their ADC values of cervical cord were measured.The influences of image qualities by various b values were analyzed.Results：Satisfactory DWI and ADC images of the 50 volunteers and ADC values were acquired.As b value increased from 300s/mm^2 to 1000s/mm^2,the signal intensities of images gradually decreased.The image quality was better as the b value=500s/mm^2,with relative high signal noise ratio and contrast,lesser artifacts were found as well.The mean ADC values of the normal cervical cord in these 50 volunteers was（95.7±11.01）×10-5mm^2/s.Conclusion：Using the single-shot echo-planar DWI pulse sequence with b value=500s/mm^2,satisfactory DWI images and ADC values of normal cervical cord could be obtained.