Figure 3. Dependence of ΔR₂ ^* and ΔR₂ on cellular shape and packing arrangement.

(a) Example of a cellular model using ellipsoid packing (left) and a 2D slice through the associated magnetic field perturbation for B₀ = 1.5T and Δχ = 5×10⁻⁸ (right). (b,c) The computed ΔR₂ ^* and ΔR₂ dependence on cell volume fraction and packing arrangement. For all packing arrangements, the relaxivity increases and then decreases with cell volume fraction. Ellipsoid packing yields greater relaxivity than spheres. ΔR₂ exhibits qualitatively similar behavior to ΔR₂ ^* yet with a reduced magnitude.