Speaker
Description
Fluid transport through brain tissue is important for removing harmful metabolic waste. Experiments on rodents indicate the presence of an active waste efflux system that transports harmful solutes by diffusion and advection. In humans, the existence of this system is still debated. The effective diffusivity within human brain tissue has been estimated using contrast-enhanced magnetic resonance imaging (MRI) data and inverse physics. Quantifying advection has also been attempted, although achieving reliable estimates has been more challenging. Recent modeling results, validated on rodent data, highlight the importance of determining the barrier properties at the brain boundary and its effect on the waste efflux system.
Here, we develop a data-driven method to estimate the effective diffusivity of fluid through the boundary of the human brain. We fit a one-dimensional diffusion model to contrast-enhanced MRI data from 980 samples, collected from 14 participants over 22 hours. This is achieved by mapping the gyrified three-dimensional geometry of each sample to a one-dimensional space identified by tissue depth. Using these results, we estimate a non-dimensional boundary parameter that recently has been identified to be essential for waste clearance but has not previously been estimated for humans.
