Depth and refocusing pulses for use with inhomogeneous radiofrequency coils in nuclear magnetic resonance spectroscopy

摘要

In a pulsed nuclear magnetic resonance method of analysis, a series of phase cycled radiofrequency pulses of the form 2&thgr;; &thgr; . +-.x!; (2&thgr; .+-.,.+-.y!).sub.4, called a depth pulse scheme, may be applied using an irradiation coil which provides an inhomogeneous radiofrequency field across the sample volume, so that signals may only be detected from sample regions where the pulse angle &thgr; is close to m&pgr;/2, where m is an odd integer. However, signals from regions where &thgr;=3&pgr;/2 or 5&pgr;/2, if such regions exist, can be eliminated by varying some of the pulses from their ideal &thgr; of 2&thgr; values. The sample discrimination afforded by means of these pulse schemes may be improved by using static or pulsed magnetic field gradients or by using more than one radiofrequency coil.