Abstract: A method and an apparatus for a locally resolved investigation of a speci, wherein the specimen is exposed to a constant magnetic field and a variable combination of three gradient magnetic fields directed substantially perpendicularly to each other and to a sequence of high-frequency (RF) pulses which contains three successive pulses with flip angles not equal to .vertline.m Pi.vertline., and signals corresponding to a magnetic resonance of spin moments, in particular nuclear spin moments in said specimen are detected. The interval (tau) between the first and the second pulse is greater than T.sub.2eff and smaller than 5T.sub.2, and that the interval (T-tau) between the second and the third pulse is greater than T.sub.2eff and smaller than 5T.sub.1, whereinm is an integer,T.sub.1 is the spin-lattice relaxation time,T.sub.2 is the spin-spin relaxation time andT.sub.2eff is the effective spin-spin relaxation time of the spins to be determined in the specimen.

Abstract: A fast low angle shot ("FLASH") NMR method is described, which uses radio frequency excitation pulses having a flip angle substantially less than 90 degrees, and subsequent reading gradient reversal for producing a gradient echo signal. The small flip angle pulses create an equilibrium state between longitudinal and transverse magnetization, which allows to apply the radio frequency pulses repeatedly with high repetition rate to produce gradient echo signals of essentially equal strength, without any intervening delay for magnetization restoration or recovery.