improved nuclear magnetic resonance imaging method using selective excitation in conjunction with driven free precession to form two or three dimensional images is disclosed the combination of these techniques enables a plane section to be selected and subsequently reconstructed from multiple angle projections by known multiple angle reconstruction techniques such as are used in x ray computed tomography alternatively the plane sections can be reconstructed using known spin warp or fourier transform zeugmatography methods to produce a map of the spin density of the material or a combination of spin density of the material or a combination of spin density and relaxation times of the material in the selected plane the improved imaging technique is particularly applicable to the detection and localization of various disease states of biological tissue which exhibit altered relaxation times application_number US 53081083 A description prior to a description of the improved nmr imaging methods employed to practice the present invention it is instructive to consider the various stages of the imaging process the four main stages are sample excitation spatial differentiation signal reception and processing and image reconstruction emphasis is placed herein on the first two of these stages during which the most novel features of the present invention come into play it is also useful at this point to provide a very brief overview of the basic nmr techniques of selective excitation multiple angle projection and spin warp imaging modified version of which are advantageously employed in the preferred embodiments of the.