Investigating cerebrospinal fluid dynamics in brain using front tracking*

Transport of solute in the brain is governed by advection and diffusion, though their relative contributions are debated. Hence, estimating the velocity fields that drive the advective transport would provide considerable insight. In vivo experiments are commonly performed wherein tracers are injected in the brain in the cerebrospinal fluid (CSF) and their distribution is imaged using the dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). We developed a three-dimensional front tracking algorithm to estimate the velocity of the CSF from the time-varying solute concentration field. The algorithm tracks the evolution of fronts, or regions of constant concentration, to estimate the CSF velocity. In the present work, we investigated the accuracy of the front tracking algorithm using synthetic data that mimics the temporal and spatial distribution of concentration in a realistic mouse brain geometry. We also used front tracking to estimate CSF velocity in real MRI scans to acquire a detailed understanding of the forces governing the tracer transport which could be extended to studying therapeutic drug delivery as well.