Characterization of Flow Distribution in the Blood Compartment of Hollow Fiber Hemodialyzers with Contrast-Enhanced Spin Echo Magnetic Resonance Imaging

Abstract

An optimized flow distribution is quintessential for hemodialyzers in order to maximize the mass transfer efficiency through the diffusion process. It is important to observe the flow pattern and the concentration profile within the hemodialyzer when evaluating its function. Thus experimental knowledge which can evaluate the above two parameters plays a significant part in the optimization of these modules. The objective of the present study was to propose an experimental method for evaluating the flow distribution pattern in the blood compartment of a hollow-fiber hemodialyzer using a contrast-enhanced spin echo T₁-weighted magnetic resonance imaging (MRI) technique by tracing the concentration profiles and theoretical interpretation. Considering a parabolic flow profile inside the hollow fibers, the relative signal intensities along the axial direction of the five types of hemodialyzers were measured after injecting the Gd-DTPA contrast solution into the blood inlet. Although uniformly decreasing concentration profiles towards the outlet ports were observed during the analysis, the calculated mean and standard deviation (SD) of all average relative signal intensities indicated that there were variations in concentration distribution between the transverse sections of the same hemodialyzer. However, most of these variabilities were found to be within one SD of this mean value. These results suggested that the contrast-enhanced MRI technique can provide a significant tool for characterizing flow distribution in hemodialyzers, both qualitatively and quantitatively.