[Quantitative calculation of drugs distribution parameter in the brain extracellular space by using MRI tracer]

To build a mathematical model to simulate the drug distribution accompanying with diffusion, distribution and clearance in the brain extracellular space (ECS).

Magnetic resonance imaging (MRI) technology was used to monitor changes in the signal-intensity-related tracer gadolinium-diethylene triamine pentaacetic acidm(Gd-DTPA), as an external drug which was injected into the rat brain, and then the mathematical model was built by using the data to establish the diffusion, distribution and clearance process of Gd-DTPA in the brain ECS. The model equation was resolved by Laplace transform. In the sphere coordinates, the linear regressive model was adopted to obtain the estimation method of diffusion coefficient, clearance rate of drugs distribution in the brain ECS.

The diffusion coefficient D and the clearance rate k were obtained as (2.73±0.364)×10(-4) mm(2)/s and (1.40±0.206)×10(-5) /s, respectively.

The proposed method can accurately reflect the isotropic drug distribution in the brain ECS, and can serve as the foundation to further solve problems about the orthotropic distribution in the brain ECS.