The present invention relates to a method of measuring the nuclear magnetic resonance in selected areas of a body for two- or three-dimensional image recording (NMR tomography) comprising the steps of exposing initially the nuclear spins of a selected type present in the selected areas of the body to a static magnetic field and at least one superimposed gradient field, and exciting them selectively by means of a pulse sequence which causes the nuclear spins to supply in a single pass a plurality of successive induction signals, and processing thereafter by calculation the induction signals corresponding to each other as regards their succession in time, to form sets of image signals proportional to the induction signals in associated volume elements of the body so that a single measurement provides a plurality of image signal sets corresponding to a sequence of section images differing by the intensity of the induction signals which vary according to the relaxation time T.sub.1 or T.sub.2.
A method of this type has been known already from German Patent Publication No. 32 09 810. According to the known method, the individual image signal sets are used for generating separate cross-sectional images supplying different details because the intensities of the induction signals obtained from different areas of the body in which the relaxation time T.sub.1 and/or T.sub.2 are different, vary differently with time. In addition, it has been known from German Patent Publication No. 32 09 810 to calculate from the variation of the image signals associated with the individual image points the relaxation time T.sub.1 and/or T.sub.2, and on the one hand to represent only areas having a specific relaxation time and, on the other hand, to correct the intensity of all image points of the individual images using the exponential-functions corresponding to the relaxation times and, thus, to achieve an improvement of the signal-to-noise ratio and, thus, of the image quality without any prolongation of the measuring time.
Although the known method offers the possibility to obtain images of high quality and of different information content, it is still not satisfactory in practical use. The preparation of a greater number of images requires a lot of documentation work. In addition, the interpretation of a number of different images requires a particularly high standard of experience. To permit correct interpretation of the images, a profound knowledge of the physical processes encountered in the generation of the images is required. However, NMR tomography is on the way to becoming a means of diagnosis which the medical specialist should be able to use without particular knowledge of such physical processes. Accordingly, it is the object of the present invention to provide a method which permits the generation of a single image providing the fullest possible, yet clear and easily understandable information.
USPTO Backgrounds
USPTO Backgrounds