METHOD AND APPARATUS FOR RAPID NMR IMAGING USING MULTI- DIMENSIONAL RECONSTRUCTION TECHNIQUES

摘要

An imaging NMR scanner generates multi-dimensional NMR spin echo responses from selected sub-volumes of an object. 90° and 180. degree. r.f. nutation pulses are used together with a variable amplitude gradient between these nutation pulses to phase encode a second dimension in the spin echo response which is already phase-encoded in a first dimension by use of a magnetic gradient during signal readout. Two- dimensional Fourier transforms or multiple angle projection reconstruction processes are then used to generate an array of pixel value data signals representing a visual image of the point-by-point spatial distribution of nutated nuclei within the object. Image artifacts potentially caused by relatively moving elements of the object are avoided by selecting the spin echo generating sub-volumes to avoid the moving elements. High resolution images of sub-volumes of interest can be obtained by selection of a sub-volume of interest in conjunction with these reconstruction techniques. Solutions for possible aliasing artifacts are also presented as are three-dimensional reconstruction techniques using NMR spin echo responses from such selected sub-volumes.