1. A method of recovering nuclear spin or NMR information from a target volume, such as a human body, placed in an at least substantially homogenous magnetic field by exciting a desired part of said target volume by means of a first radiofrequency pulse which deviates nuclear magnetization preferably 90.degree., by generating a spin echo by utilizing a second excitation pulse which preferably deviates nuclear magnetization 180.degree., by recording said spin echo, and by repeating said excitation sequence, characterized in that along one axis of the target volume at least one magnetic field gradient is sequentially and repetitively applied, at least one of the duration and amplitude of said magnetic field gradient being varied in each repetition of the sequence such that the difference between the absolute values of the time integral of said magnetic field gradient following said 180.degree. second excitation pulse and the time integral of said magnetic field gradient preceding said 180.degree. second excitation pulse differs in each repetition of the sequence.