MRI-based Estimation of Patient-specific Cerebrospinal Fluid Velocity across Breathing Techniques

Research has shown that disruptions of normal cerebrospinal fluid (CSF) flow may contribute to the progression of Alzheimer’s disease. The pulsatory nature of CSF flow has not been adequately characterized and is influenced by cardiac, respiratory, and low-frequency oscillations. To investigate the temporal behavior of CSF flow in the brain, we developed a novel estimation of CSF velocity using MRI-derived parameters. Using over 10-minutes of continuous functional MRI (fMRI) data coupled with breathing protocols, we measure the amplitude oscillations in a given voxel attributable to the inflow of fluid between time-points. A history of bi-directional flow-related oscillations in fMRI amplitude is obtained by placing a voxel at the centroid of the 4^th ventricle and performing the same scan for outflow. The maximum fMRI amplitude across all breathing protocols is used to estimate the maximum resolvable velocity corresponding to fresh fluid filling the voxel between time-points. We scale the temporal amplitude by the measured maximum amplitude to estimate patient-specific, temporally-resolved, axial flow speed. Velocities are compared across breathing protocols to estimate the effect of breathing on CSF flow as well as provide in-vivo estimations of velocity in the 4^th ventricle.