Abstract: A magnetic field generating assembly used in NMR apparatus includes a primary magnetic field generator for generating a primary magnetic field which is substantially homogeneous in the working region. The primary magnetic field generator is constructed such that an object to be examined can be introduced from outside the assembly into the working region in a direction transverse to the direction of magnetic flux through the working region. Gradient magnetic field coils are provided for imposing one or more magnetic field gradients through the working region. The gradient magnetic field coils are movable relative to the primary magnetic field generator for positioning locally to the position of an object to be examined in the working region.

Abstract: A magnetic field generating assembly having at least two magnetic fields in the same sense. The generators are arranged such that, in use in a working region external to the generators, the resultant magnetic field exhibits a gradient extending in a first direction and at least second order variations in the fields in directions transverse to the first direction within the working region are substantially balanced such that an NMR experiment can be performed on a sample within the working region in accordance with the related method. The magnetic electrical field generators are substantially coaxial electrical coils, wherein the axis extends in the first direction.

Abstract: Magnetic field generating apparatus having a solenoid arranged to generate a steady magnetic field gradient along its axis. The arrangement is such that in use contours of constant field are formed within the solenoid. The contours extend generally radially outwardly from the axis of the solenoid and asymmetrically with respect to the center plane of the solenoid orthogonal to its axis. Regions of substantially homogeneous magnetic field suitable for performing an NMR experiment exist about each contour, the regions having substantially constant thickness along the contours.

Abstract: An improved method for measuring very slow flow rates using nuclear magnetic resonance techniques is disclosed. The basic technique is that of steady state free precession, in which a sequence of radio frequency pulses are applied to nuclei in a magnetic field having a substantial gradient, so that a driven equilibrium state is obtained and which is characterized by a spatial periodicity in the magnetization response of the nuclei. Two images are generated. The two images may be generated using different time intervals between the application of the radio frequency pulses. Alternatively, the two images may be generated using different effective gradients. The spatial periodicity, and the NMR response of flowing nuclei to the spatial periodicity, is thus different during the two image formations. One image is subtracted from the other, which cancels signals from static nuclei in the signal, while relatively fast flowing nuclei, namely in the larger blood vessels or the like, never reach the equilibrium state.

Abstract: Method and apparatus for producing an N.M.R. picture of a plane through an object by isolating the plane using an oscillating gradient and interrogating the plane using a rotating gradient and a multiplicity of R.F. pulses which are averaged over a defined period to produce an average response which is used to produce the N.M.R. picture.