Non-Invasive Measurement of Counter-Current Flows in a Hemodialyzer Using Fourier-Velocity Magnetic Resonance Imaging

Abstract

Abstract The objectives of this paper are: (1) to show the usefulness of Fourier-velocity magnetic resonance imaging (MRI) technique in validating numerical models in the design of an optimal hemodialyzer, and (2) in characterizing non-invasively the spatial counter-current flow distribution in a hemodialyzer. The relative amount of flows at different velocity range for both the blood and dialysate compartments of a CT190G hemodialyzer (Baxter Healthcare Corporation, Deerfield, IL) was measured non-invasively using the Fourier-velocity MRI technique. This technique was first validated by imaging a flow phantom. The flow phantom consisted of two parallel-Plexiglas tubes with flows introduced counter-currently in each tube. In both cases, twenty-four images were acquired at thin cross sections corresponding to the flows at the mean velocities {−24, ..., −4, −2, 0,+2, +4, ..., +22} mm/s. These images were acquired at the mid-section of both the two-parallel-Plexiglas tube and the hemodialyzer. The empirical results were found to be comparable to numerical results computed from the Navier-Stokes equations. Images of the hemodialyzer demonstrated a wide spatial flow distribution both inside the blood and dialysate compartments. A segment of the hemodialyzer had reduced intra-fiber flow indicating a region of occlusion in the blood compartment. Flow at the dialysate compartment was greater at the periphery of the hollow-fiber bundle adjacent to the housing.