A method of, and apparatus for, determining fluid movement using nuclear magnetic resonance.

摘要

A modified spin echo sequence is employed to identify fuild movement in a material. The volume of interest is subject to a static field along one axis (Z) and an RF magnetic excitation pulse transverse to the static field is applied which tilts the nuclear spins in the volume. The tilted nuclear spins are then allowed to precess about the uniform static field in the presence of a gradient field whereby the nuclear spins become dephased. Thereafter, a spin echo of the static spins is created by either a 180° RF pulse or reversal of the gradient field. Upon refocusing of the static nuclear spins a restoration RF pulse is applied to realign the stationary nuclear spins with the static field. Nuclear spins undergoing bulk motion as in fluid flow will be refocused to a different phase than the stationary spins so that the final RF pulse will in general leave these residual spins with a non-zero transverse magnetic moment. Such residual transverse magnetic spins are then detected to identify the fluid movement.