优选颈髓扩散张量磁共振成像扫描参数

Optimization of the Scan Parameters for Diffusion Tensor Imaging of Cervical Cord

目的:探索颈髓扩散张量磁共振成像(DTI)的最佳扫描参数。方法:对40名成年健康志愿者行颈髓扩散张量成像,比较不同扫描参数[b值、扩散敏感梯度方向数及激励次数(NEX)、层厚]对图像质量的影响。第1组,b值分别取400,700,1 000 s/mm2;第2组,扩散敏感梯度方向数分别取6,13,25个;第3组,激励次数分别取2,4,8;第4组,层厚分别取2,3,4 mm。结果:在4种不同扫描参数的比较中,b值为700 s/mm2的图像质量较b值为400 s/mm2和1 000 s/mm2的好(P<0.05);方向为25时的图像质量较方向为6和13的图像质量好(P<0.05);NEX为4的图像质量较NEX为2和8的好(P<0.05);层厚为4 mm的图像质量较层厚2 mm和3 mm的好(P<0.05)。结论:b值为700 s/mm2、扩散敏感梯度方向为25个、NEX为4和层厚为4 mm是颈髓DTI的最佳扫描参数,适用于临床研究颈髓的细微结构。

Objective： To search for the optimal scanning parameters for diffusion tensor imaging（DTI） in the clinical study of the cervical cord. Methods： Diffusion tensor imaging of the cervical cord was performed in 40 healthy adult volunteers. Different parameters including b values, the numbers of the diffusion sensitive gradient directions, the numbers of excitations and slice thickness were evaluated and their effects on the quality of the images were compared. In group 1, DTI was performed on the cervical spinal cord with different b-values 400, 700 and 1 000 s/mm^2; then with different numbers of diffusion gradient directions 6, 13 and 25 mm in group 2; different numbers of excitations 2, 4 and 8 in group 3;and different slice thicknesses 2, 3, and 4 mm in group 4. Results： In the comparison of the four different parameters, DTI using a b-value of 700s/mm^2 showed a better imaging quality than those with the b-values of 400 s/mm^2 and 1000 s/ mm^2（P〈0.05）; DTI using directions of 25 showed significantly better imaging quality than those with the directions of 6 and 13（P〈0.05）; DTI using excitations of 4 showed better imaging quality than those with 2 and 8 excitations（P〈0.05） ; DTI using a slice thickness of 4 mm showed better imaging quality than those with slice thickness of 2 mm and 3 mm （P〈0. 05）. Conclusion： Optimal parameters for DTI in the cervical spinal cord included a b value 700 s/mm^2 , 25 diffusion gradient directions, 4 excitations and a slice thickness of 4 mm and those were the best parameters in the clinical study of the micro-structures of cervical cord.