目的　应用3.0T MR扩散张量成像（DTI）和白质纤维成像技术（DTT），研究脑干小脑上脚纤维（SCP）交叉的微观结构和特性。  方法　Siemens 3.0T MR对20例健康志愿者行头颅轴位DTI (b=0和b=1000)检查, 应用工作站纤维束跟踪软件三维重建脑干SCP纤维交叉，选择参数：FA为0.08、角度阈值为80°、体素为1.2 mm×1.2 mm×3 mm。测量SCP和SCP交叉的各向异性分数（FA）值,比较两者之间的差异。  结果    脑干SCP纤维交叉出现三种不同形态：(1)交叉，占65％（13例）；(2)对吻，占25％（5例）；(3)分叉，占10％（2例）。SCP交叉和SCP的FA值分别为：0.40±0.13和0.65±0.08，两者之间差异有统计学意义（t=7.22，P＜0.05）    结论    DTT三维重建技术能显示脑干SCP交叉纤维束的解剖类型，3.0T MR对于活体脑干交叉纤维束的研究有较好的临床应用价值。

Objective　 To investigate the features of decussation of the superior cerebellar peduncle(SCP) by diffusion tensor imaging(DTI) and diffusion tensor tractography(DTT) on 3.0T MR.　Methods　Twenty healthy volunteers were examined on SIEMENS 3.0T MRI diffusion tensor imaging (DTI) (b0=0 s/mm2, b1 =1000 s/mm2) ; post processing were made in SIEMENS Leonardo workstation using SIEMENS Standard 6 directions software to reconstruct the white matter fibers with fractional anisotropy (FA) threshold value 0.08, angle threshold value 80°and voxel size 1.2 mm×1.2 mm×3 mm. The FA of decussation of SCP was compared with that of the fiber of SCP by paired t-test.　Results　 There were three kinds of MR fiber tracking appearances at decussation of SCP of brainstem on MRI diffusion tensor tractography(DTT). Decussation of SCP of 20 cases was classified as follows: ①crossing fiber, accounting for 65% (13 cases); ②＞＜ kissing fiber, accounting for 25% (5 cases); ③ Y forking fiber, accounting for 10% (2 cases). There was  statistically significant difference in FA value (t=7.22, 0.40±0.13 and 0.65±0.08，P＜0.05) between decussation of SCP and that of the fiber of SCP. Conclusions　3.0T MR would be a useful technology for demonstrating the anatomic features of decussation of SCP of the brainstem, while DTT 3D-reconstruction is valuable for demonstrating the distribution of the crossing fibers in the brainstem during clinical application.