Interstitial pressure, volume, and flow during infusion into brain tissue.

A model of infusion-induced swelling in the brain is presented, in which gray and white matter are treated as poroelastic media. The distributions of interstitial pressure, flow, and volume are derived for steady-state and transient infusion protocols. A significant percentage increase in interstitial volume is predicted near the injection site, despite only a modest increase in tissue-averaged fluid content there. The model also can be used to estimate mechanical parameters of brain tissue, such as its hydraulic permeability, shear modulus, and Lamé constant. A solute transport equation that incorporates tissue swelling is also presented. This work suggests that knowing the distribution of swelling induced by infusion is a prerequisite to describing interstitial transport of solutes.