CORRELATED SUSCEPTIBILITY AND DIFFUSION EFFECTS IN NMR MICROSCOPY USING BOTH PHASE-FREQUENCY ENCODING AND PHASE-PHASE ENCODING

NMR microscopy can exhibit contrasts which are characteristic of the local Brownian dynamics, the local susceptibility-related fields, and the imaging method employed. The influence of susceptibility inhomogeneity and self-diffusion in NMR imaging using both phase-frequency and phase-phase encoding have been investigated. It is shown both theoretically and experimentally that the interplay of susceptibility and self-diffusion in phase-frequency (spin-warp) imaging can lead to bright features which act as a signature for local boundaries. For phase-phase encoding, equations for the point-spread function which arises from both susceptibility inhomogeneity and diffusion are derived and it is shown that phase-phase encoding offers the possibility of overcoming both these phenomena, while achieving optimal, sensitivity-limited, resolution. (C) 1994 Academic Press, Inc.