[Measurement of brain extracellular space and its physiological and pathophysiological significance].

The extracellular space (ECS) of brain is defined as an irregular channel which is located in the interstitial tissue outside the plasma membranes of neurons, and occupied by interstitial fluid (ISF). Diffusion in ECS is described by a modified diffusion equation from which several parameters can be calculated, such as the diffusion coefficient (D), the tortuosity (Lambda), the volume fraction (alpha) and the clearance of molecules. Radiolabeled tracers were used for early diffusion measurements.

[Imaging and quantitative measurement of brain extracellular space using MRI Gd-DTPA tracer method].

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 microL 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.