Nuclear magnetic resonance method and apparatus

摘要

A method of nuclear magnetic resonance imaging of a body in which the spins of a chosen nucleus in a selected slice of the body are rotated through an angle appreciably greater than 90 DEG . Two r.f. pulses, each accompanied by a magnetic field having a gradient in a direction parallel to the equilibrium axis of magnetic alignment of the spins are applied in sequence. Each e.f. pulse is at the Larmor frequency for the nuclei in the slice in the presence of the associated field gradient and each r.f. pulse is effective to rotate the spins by not greater than 90 DEG . The r.f. pulses together are sufficient to rotate the spins through the desired angle, the gradients of the magnetic fields being in opposite directions.