Fig. 7.
A simple PFG sequence, where two opposing gradients which are separated by a certain duration causes the magnetization vectors to first rotate and later return to their original phase value for stationary protons, causing a net phase accumulation only for nonstationary protons. Two variants of this simple PFG pulse sequence are also given: pulsed gradient spin-echo (PGSE) sequence with the introduction of a spin echo and the pulsed gradient stimulated echo (PGSTE) sequence, which stores one component of the magnetization along longitudinal magnetization (see Section II-E for details).