UC San Diego

Characterization of cerebrospinal fluid (CSF) dynamics in the central nervous system is fundamental for the study of CSF-related disorders, such as normal pressure hydrocephalus, Chiari malformation, and syringomyelia, which can help guide clinical diagnosis and treatment therapy. In this thesis, phase contrast, a non-invasive magnetic resonance imaging (MRI) technique that can map the phase accrual of the moving fluid region to velocity, is combined with rigorously derived simplified models of the CSF motion to enable patient-specific quantitative descriptions of the fluid flow and associated pressure variations for clinical use. Attention is focused on two specific problems, namely, flow in the cerebral aqueduct, a slender canal connecting the third and fourth ventricles of the brain, and flow in the spinal canal. In the former case, special attention is given to the relation between the predicted flow rate and the interventricular pressure variation, which is subsequently used in a volunteer study to obtain indirect evaluations of the transmantle pressure from direct MRI flow measurements corresponding to 77 subjects. The model for the pulsating viscous motion in the spinal canal assumes a linearly elastic compliant tube of slowly varying section, with a Darcy pressure-loss term included to model the fluid resistance introduced by the microanatomy. As shown by the preliminary computations presented here, this simple one-dimensional model can serve as a basis for quantitative analyses targeting predictions of intracranial pressure temporal fluctuations based on MRI measurements of spinal-canal anatomy and CSF flow rate. Future directions are proposed concerning both flow problems, including further validation exercises involving in-vitro and in-vivo experiments.