中文摘要：

目的：观察钆喷酸葡胺（Gd-DTPA）在脑细胞外间隙（brain extracellular space,ECS）中扩散的磁共振成像（magnetic resonance imaging,MRI）表现与规律,探讨应用MRI示踪法对ECS进行定量分析的可行性。方法：将8只雄性SD大鼠（280 g～320 g）麻醉后,参考脑立体定位图谱,选取冠状位苍白球为中心层面,以尾状核为靶点进行穿刺定位,导入Gd-DTPA2μL。于导入后1、3、6、9、12 h分别进行MRI扫描,观察MRI表现,测量示踪剂导入侧所在脑区与对侧相应脑区MR信号强度随时间的变化规律。于12 h MRI扫描结束后,对大鼠进行行为学评分。结果：MRI图像证实6只大鼠Gd-DTPA导入点位于尾状核区,2只位于外囊区。Gd-DTPA在尾状核区导入后呈均匀扩散,3 h扩散到达同侧大脑皮层,扩散后主要分布在大脑中动脉供血区的脑组织。随着扩散范围的增大,尾状核区的MRI信号强度逐渐下降,3 h后各个时间点相对MRI信号强度ΔS与1 h时ΔS间差异存在统计学意义（t=95.63,P〈0.01）,3 h后的各组ΔS间差异无统计学意义（P〉0.05）。ΔS的衰减规律呈指数形式[y=1.7886x^-0.1776（R^2=0.94）]。导入外囊区的Gd-DTPA在1 h的MRI上呈弧形沿白质纤维扩散,表现为各向异性。在3 h后呈扇形向相邻脑区扩散,6 h时扩散到达同侧皮层区。结论：应用MRI示踪法可动态观察Gd-DTPA在细胞外间隙的扩散与清除衰减规律,是在活体对ECS解剖与生理学参数进行定量研究的可行方法。

英文摘要：

Objective：To observe the diffusion of Gd-DTPA in brain extracellular space（ECS） by magnetic resonance imaging（MRI） and investigate the feasibility of ECS measurement by using MRI tracer method in vivo.Methods： 2 μL Gd-DTPA was introduced into ECS by caudate nucleus according to stereotaxic atlas in 8 Sprague Dawley（SD） rats（male,280~320 g）.The MRI scans were performed at 1 h,3 h,6 h,9 h and 12 h respectively after administration.MRI appearances of Gd-DTPA diffusion and distribution was observed and compared.The MRI signal enhancement was measured at each time point.The neuroethology assessment was performed after MRI scanning at 12 h.Results： The injection was accurate at the center of the caudate nucleus in 6 rats,while,at the capsula externa in other 2 rats.Gd-DTPA diffused isotropically after it was introduced into caudate nucleus,which spread into lateral cortex at 3 h.The MRI signal enhancement distributed mainly in the middle cerebral artery territory.A significant difference was found between the signal enhancement ratio at 1 h and that at 3 h in the original point of caudate nucleus（t=95.63,P〈0.01）,and the signal enhancement attenuated following the exponential power function y=1.7886x^-0.1776（R2=0.94）.In 2 rats with the injection point at capsula externa,Gd-DTPA diffused anisotropically along the fiber track of white matter during 1 h to 3 h,and spread into the lateral cortex at 6 h.Conclusion： The diffusion and clearance of Gd-DTPA in brain ECS could be monitored and measured quantitatively in vivo by MRI tracer method.