Random-walk technique for simulating NMR measurements and 2D NMR maps of porous media with relaxing and permeable boundaries.

摘要: Abstract We revisit random-walk methods to simulate the NMR response of fluids in porous media. Simulations reproduce effects diffusion within external inhomogeneous background magnetic fields, imperfect and finite-duration B1 pulses, T1/T2 contrasts, relaxing or permeable boundaries. The simulation approach consolidates existing numerical used biology engineering into a single formulation that expands on magnetic-dipole equivalent spin packets. When exhibit low contrasts when CPMG pulse sequences are acquire measurements, we verify classical models neglect T1 accurately surface magnetization decays saturated granular media regardless diffusion/relaxation regime. Currently, analytical expressions exist only for case arbitrary pore shapes fast-diffusion limit. However, include several components fields strongly inhomogeneous, show simulations results obtained using complete set Bloch’s equations differ substantially from those models. In addition, our reproduces echoes stemming coherent-pathway calculations. is especially suited generate parametric multi-dimensional T1/T2/D maps improve characterization structures saturating fluids.