人脑皮质脊髓束三维概率图及其可重复性研究

目的 应用DTI成像及纤维概率追踪显示技术探索人脑皮质脊髓束的三维空间形态及个体变异,确定皮质脊髓束的空间位置,为皮质脊髓束功能解剖研究提供形态学依据.方法 选择15例健康自愿者进行3T MRI扫描,获取T1和DTI图像(12个方向, b=1000 s/mm2).应用FSL软件FDT工具包处理数据并完成全脑白质纤维概率追踪,在彩色FA图上根据不同纤维方向轮廓勾画出皮质脊髓束的轮廓(在大脑脚以及内囊后肢的蓝色区域),将其作为ROI进行纤维概率追踪得到皮质脊髓束概率图.将各受试者T1图像配准到ICBM152-T1模板,然后根据其配准参数文件将各个体皮质脊髓束转换到标准空间,定量分析皮质脊髓束的可重复性及个体变异 .结果 皮质脊髓束在MNI标准空间中的空间分布广,左侧皮质脊髓束X坐标为-58 到 1, Y坐标为 20 到 -56,Z坐标为 -20 到 80; 右侧皮质脊髓束X坐标为 2 到 54,Y坐标为12到-51, Z坐标为 -20 到 76.皮质脊髓束可重复性在内囊处最高,右侧皮质脊髓束可重复性高于左侧,但无显著性差异.左侧皮质脊髓束平均体积 (57 416.67±1944.56)mm3,右侧平均体积(54 421.58±1232.43)mm3.结论 应用 DTI成像及纤维概率追踪显示技术可以更准确地分析皮质脊髓束的三维形态及空间坐标,为相关神经系统疾病的研究和功能神经外科手术定位提供直观可信的形态学依据.

Probabilistic maps and reproducibility of the corticospinal tract by diffusion tensor imaging

Objective To study the probabilistic maps and the reproducibility of the corticospinal tract, providing the 3D anatomical data of the corticospinal tract to the neurosurgical planning. Methods Diffusion weighted images were acquired in 15 healthy volunteers (3.0T Siemens sonata, 12 diffusion directions, b=1000 s/mm², 36 slices, thickness 3 mm), high-resolution T1-weighted images were acquired with a 3D MPRAGE sequence (TR/TE/FA=2600 ms/3.93 ms/8°, matrix=256×240, 1 mm thickness). Pre-processing of DTI data included eddy current correction and computations of the diffusion tensor elements and fractional anisotropy (FA) maps used FSL software. The masks outlined by blue color at the peduncle and the posterior limb of the internal capsule in the FA color map using Fslview. In the color maps, red, green and blue colors were assigned to right-left, anterior-posterior, and superior-inferior orientations, respectively. T1 images were registered to the ICBM152-T1 template then the diffusion space transferred to the standard space, the masks served as the seeds and waypoints for probabilistic tractography. The probability maps were generated as a quantitative measure of reproducibility for each voxel of the stereotaxic space. Results The probability maps of the corticospinal tract showed on the axial sections and on the coronal sections in the ICBM152-T1 template, the color bars indicated the relative frequency of voxels containing the corticospinal tract from 0 to 100% (yellow) at the 20% step. The coordinates of corticospinal tract in the anatomical MNI space (orientation according the AC-PC line) showed that X was from -58 to 1 in the left and 2 to 54 in the right, Y was from 20 to -56 in the left and from 12 to -51 in the right, Z was -20 to 80 in the left and -20 to 76 in the right. The mean volume of the left corticospinal tract was (57 416.67±1944.56) mm³; the right corticospinal tract was (54 421.58±1232.43) mm³. The degree of intersubject reproducibility shifted along its course with the highest reproducibility in the internal capsule, the reproducibility of the corticospinal tract was higher in the right than that in the left hemisphere. Conclusion The results show that diffusion tensor tractography can establish the 3D probability maps of the corticospinal tract, the degree of intersubject reproducibility of the corticospinal tract is consistent with previous architectonic report. The maps are useful for evaluating and identifying the corticospinal tract in DTI, providing anatomical information to preoperative planning and improve the accuracy of surgical risk assessments preoperatively. For the future, it is valuable to establish the probabilistic maps of the major fiber tracts by diffusion tensor tractography and combine DTI tractogrhphy-based white matter images with architectonic probabilistic maps.