大脑白质纤维磁共振弥散张量成像扫描参数研究

Study of the scanning parameters for MR diffusion tensor of cerebral white matter fiber

目的：探讨不同的磁共振弥散张量成像（diffusion tensor imaging,DTI）扫描参数对大脑白质纤维弥散张量图像的影响,以期获得最佳的扫描参数。方法：21例正常志愿者（男11例,女10例;年龄16-63岁,平均38.7岁）参加了该项研究。随机分为3组：b值组、弥散敏感梯度方向组和层厚/层间距组。各组分别应用不同的DTI扫描参数,第1组b值组：可变参数是b值,分别为300、1 000、3 000 s/mm^2mm,不变参数是：层厚/层间距5 mm/0 mm,弥散敏感梯度方向数21。第2组弥散敏感梯度方向组：可变参数是弥散敏感梯度方向数,分别为6、13、21,不变参数是：层厚/层间距5 mm/0 mm,b值为1 000 s/mm^2。第3组层厚/层间距组,可变参数是层厚/层间距,分别为8 mm/2 mm5、mm/0 mm、3.5 mm/0 mm,不变参数是：b值为1 000 s/mm^2,弥散敏感梯度方向数为21。将所成FA图像和DEC图分为3个不同的等级,进行评价。结果：不同的扫描参数所成大脑白质纤维弥散张量图像的质量是不相同的。在b值组,以低b值所成图像较佳,其中以b值=1 000 s/mm^2为最佳,而高b值所成图像噪声较大。施加的弥散敏感梯度方向数并非越多越好,13个方向与21个方向所成图像没有明显差别,6个方向所成图像质量较差。层厚/层间距对图像的影响最大,层厚越厚,图像的信噪比越大。结论：在临床工作中,比较实用的大脑白质纤维弥散张量成像扫描参数为：b值=1 000 s/mm^2,弥散敏感梯度方向数为13,层厚/层间距为5 mm/0 mm。

Objective：To search for the best scanning parameters for MR diffusion tensor imaging in the study of the cerebral white matter fiber. Methods：Twenty-one healthy adult volunteers （11 men, 10 women; age range 16 - 63 years; mean age 38. 7 years） randomly divided into three groups, were performed with MR diffusion tensor imaging. Different parameters including b value, number of the diffusion sensitive gradient direction, and slice thickness were applied on the three groups. The first group （b value） .. variable parameter is b value, 300, 1000, 3000 s/mm^2 ; invariable parameter were the number of the diffusion sensitive gradient direction 21 and slice/interval thickness 5mm/0mm, the second group （number of the diffusion sensitive gradient direction） .. variable parameter was the number of the diffusion sensitive gradient direction, 6, 13, 21; invariable parameter were b value 1000 s/mm^2 and slice/interval thickness 5 mm/0 mm; the third group （slice/interval thickness）., variable parameter was slice/interval thickness, 8 mm/2 mm, 5 mm/0 mm, 3.5 mm/0 mm, invariable parameter were b value 1000 s/ mm^2 and the number of the diffusion sensitive gradient direction 21. Different parameter impaction on the FA maps and DEC maps were evaluated. Results.. Different parameters result in different quality of the FA and DEC map. It was better when b vab ue= 1000 s/mm^2 was used, and noise become greater when b balue=3000 s/mm^2. The quality of the image was not parellel to the direction number. Slice/interval thickness had the greatest impaction on the SNR of the images. Conclusion：Cerebral white matter fiber; Diffusion tensor imaging; Scan parameter