Abstract: A method is disclosed for superimposing field strength gradients on the image produced by an NMR imager by using a preparation step of tipping the spins of the volume elements with a 90.degree. wait 90.degree. RF pulse sequence for each data collection pass and performing the image encoding and data collection required to obtain the desired data set and transforming the data set into a planar image. A method is also disclosed for superimposing gradients on such an image indicative of the accuracy of the tipping process of an NMR imager.

Abstract: A method of tuning an NMR spectrometer is disclosed that includes the step of locating a specimen in a stationary magnetic field, generating a 90.degree. alternating magnetic field excitation pulse at the Larmor frequency of the selected nuclei of the specimen followed by one or more 180.degree. alternating magnetic field refocusing pulses of preselected duration at fixed time intervals having the same phase relationships using a free-running oscillator that is turned off between pulses, measuring the primary echo train of a selected nuclear magnetic resonance signal, changing the strength of the stationary magnetic field to change the Larmor frequency of the selected nuclei, repeating the pulsing step and the measuring step until the maximum primary echo is obtained, and while holding the stationary field at that strength, measuring the desired nuclear magnetic resonance characteristic using the spin-echo method and the free-running oscillator to supply the pulses.