Abstract: In an improved NMR imaging method for forming images of a subject by determining the relative densities of nuclei within the subject, three orthogonal gradient fields are generated by digitally storing three gradient waveforms for each orthogonal direction, with each waveform being individually compensated and calibrated with respect to an axis with which it is associated. Nine associated matrix multiplying functions which determine the coordinates of a desired slice in its rotated plane are also stored by an external input (by computer or by the clinician operating the system.) Then, in a sequential fashion, digital words for each gradient waveform are read out, multiplied by pairs with the appropriate multiplying function and the three terms are added to form a digital word. These words are converted to an analog value and applied to the respective gradient coils.

Abstract: There is disclosed an improved NMR imaging method utilized for forming images of a subject by determining the relative densities of nuclei within the subject. A main magnetic field is applied to the subject to create aligned nuclear spins in the nuclei. Radio frequency energy is applied to the subject at a predetermined Larmor frequency to create a radio frequency field acting in a direction substantially perpendicular to the main magnetic field. A gradient magnetic field is applied to the subject along a selected axis at a time substantially coincident to the time of application of the radio frequency energy so that the nuclei in only a thin slice of the subject are excited. The application of radio frequency energy is terminated after a predetermined time. Thereafter, two time varying balanced gradient magnetic fields are applied to the subject along two perpendicular axes, which are both perpendicular to the first magnetic gradient field.