DTI和fMRI在正常成人视觉系统的联合应用研究

目的:联合应用BOLD-fMRI及DTI两种技术,用量化的指标研究正常成人视觉皮质激活区域的弥散特征以及与之相连视放射的弥散特性之间的关系,评价此种方法在显示脑区连接方面的价值。材料和方法:10名正常志愿者行视觉刺激下的fMRI扫描,应用闪烁的棋盘方格作为任务刺激,同时扫描层厚与位置相同的DTI图像。用SPM99处理fMRI图像,DTVⅡ软件处理DTI图像。将脑的激活图叠加于FA或DEC图,分别测量视放射以及视觉皮质激活区域的FA值,并将二者进行比较。结果:10例均见双侧初级视觉皮质V1以及V2区的激活;5例伴有V5区即视觉运动区(MT区)的激活,其中3例可见外侧膝状体(LGN)的激活信号。视放射FA均值与激活区的FA均值比较有显著性差异(P<0.001)。将激活图叠加于DEC图后,直观显示了前后走行的视放射纤维连接激活的LGN与激活的视皮质。结论:联合fMRI与DTI方法发现BOLD信号主要位于具有各向同性特征的灰质区域,更有助于BOLD的定位;可以直观显示不同脑区之间的纤维连接,有助于研究脑结构与功能之间的关系。

Study the Relationship of both Structure and Function in Visual System by Combining DTI and fMRI

Purpose: To demonstrate the feasibility of combining DTI and fMRI maps to show fiber tract anatomy in relation to activations and to quantitate anisotropy in white matter tracts and functionally activated regions. Materials and Methods: DTI and fMRI were performed in 10 normal volunteers. Functional activity was generated using flashing checkerbord (12 visual angle) at 8 Hz. The activated maps were overlayed upon FA maps and DEC maps using the software of MRIcro. FA values were measured within activated regions and in the optic radiations.Results: All subjects showed activations in primary visual cortex, and with V5 activations in 5 and LGN activations in 3. FA values within activated reagions were much lower than that of optic radiations.Overlay of fMRI maps on to DEC maps showed that the optic radiation fiber tracts linked the activated LGN and primary visual cortices directly in 3 cases.Conclusion:Activated regions had lower FA value than optic radiation, supporting that most BOLD signal changes occurs within the relatively isotropic cotical grey matter.The combination of both techniques can also help demonstrating functional connectivity between different cortices and subcortical areas directly.