Simulations of NMR-detected diffusion in suspensions of red cells: the "signatures" in q-space plots of various lattice arrangements

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Abstract
Coherence effects from pulsed field-gradient spin-echo (PGSE) nuclear magnetic resonance diffusion experiments have been observed and characterized for diffusants in many heterogeneous systems, ranging from porous materials to cell suspensions. The resulting coherence patterns appear in plots of the normalized PGSE signal intensities as a function of the spatial wave vector q in a so-called q-space plot. The origin of these phenomena and their mathematical and physical underpinnings are now well established. We have conducted a number of studies of diffusion-coherence phenomena in suspensions of red blood cells and have made extensive use of computer simulations of molecular diffusion in virtual lattices of cells to aid in the interpretation and analysis of experimental data. In the current work we extended the canonical model used in these studies to investigate the effect that varying the packing arrangement of cells in the suspension has on the coherence patterns, as seen in q-space plots. We show that changes in the packing arrangement of cells are reflected in the q-space plots and in the results of diffusion tensor analysis and thus we speculate upon the possible clinical importance of these findings.