Abstract: Pulsed NMR system for industrial measurements comprising sample throughput system (P, LI, V1, V2) and user system controls (104) to establish digitized free induction decay (FID) curves (C), from which fast Gaussian, slower modified Gaussian and exponential components are determined using a Marquardt-Levenberg iteration technique, and using regression techniques to correlate the FID curve components to the physical quantities of the target nuclei.

Abstract: Pulsed NMR system for industrial measurements comprising sample throughout system (P, LI, V1, V2) and user system controls (104) to establish digitized free induction decay curves (C), from which Abragam, Gaussianand exponential components are determined using a Marquardt-Levenberg iteration technique, and using regression techniques to correlate the curve components to the target nuclei.

Abstract: A method is provided for carrying out proton magnetic resonance thermal analysis measurements. To this end, the method provides locating a sample within a coil forming part of an RF tuned circuit and applying a magnetic field to the sample. The sample is heated in accordance with a predetermined temperature regime. Pulsed RF energy is applied to the coil to generate a pulsed RF electromagnetic field which is applied to the sample. The magnitude of the magnetic field is adjusted to insure that the NMR frequency of the sample is substantially identical to the RF frequency. The resonant frequency of the tuned circuit is adjusted to compensate for temperature induced changes in the tuned circuit components and the sample. The energy of the pulsed RF energy is adjusted to obtain an optimum output from the RF tuned circuit. The RF tuned circuit output is recorded as a function of either time or temperature of the sample.

Abstract: A method for enhancing the sensitivity of gradient-recalled echo imaging for T2* effects in dynamic magnetic resonance imaging which involves the step of delaying gradient-recalled echoes so that the gradient-recalled echoes are subjected to magnetic susceptibility effects for an extended period of time. The gradient-recalled echoes are delayed beyond a subsequent radio frequency pulse by applying an additional gradient which dephases any gradient-recalled echo of spins that are excited in the radio frequency repetition time period in which said gradient-recalled echoes are produced.

Abstract: A magnetic resonance imaging method capable of discriminating the flow directions of fluids, such as bloodstreams, and suitable for MR angiography first selectively excites two side regions, which are located in the vicinity of a region to be imaged including fluids in an object to be examined, and which include first and second fluids flowing into the region to be imaged along different directions, by using RF pulses (90.degree. pulses) different from each other in phase by 90.degree.. A spin in one side region is rotated to the x'-axis direction in a rotating coordinate system, and that in the other side region is rotated to the y'-axis direction in the system. A 180.degree. pulse is applied to the region to be imaged to invert the polarity of a spin, thereby generating MR signals. The acquired MR signals are subjected to quadrature detection, and MR images are reconstructed for both a real-part component and an imaginary-part component different from each other in phase by 90.degree..

Abstract: A superconducting magnetic imaging apparatus includes a vacuum vessel (40) having a central helium reservoir (48) in which superconducting magnetic coil windings (44) are maintained at a superconducting temperature. The vacuum vessel defines an internal bore (42) within which a self-shielded gradient coil assembly (14) and an RF coil (22) are received. The self-shielded coil assembly includes an inner former (60) which defines an imaging region (12) within which an imaged portion of the patient are received. X and y-gradient coils having winding patterns (62) are bonded to the former (60) forming an integral structure. A z-gradient coil (70) is mounted to mechanical reinforcement structure (72) to be held in a spaced relationship from the x and y-gradient coils with an air gap (74) in between. This facilitates the dissipation of heat generated by the large current pulses applied to the x and y-gradient coils.

Abstract: A magnetic resonance experiment is described in which a sample under test is subjected to a sequence of gradient magnetic fields and RF pulses and resultant pulse echoes are monitored. At least one of the RF pulses comprises a prefocused, phase-modulated, time-asymmetric RF pulse.

Abstract: A superconducting means for MRI including seven to nine small superconducting coils situated in such a manner that the number of turns of these coils becomes progressively greater towards the outside, and preventing the occurrence of 2nd to 16th order inhomogeneous fields.

Abstract: A device for coupling a radio frequency transceiver of an MRI system utilizes a tunable hybrid network. The network is formed of fixed value capacitors connected to transmission lines that provide inductive reactance to the network. The connection of the components is such that an input signal applied to one node produces a pair of signals in quadrature at two other nodes. In order to insure that the pair of signals have the proper phase and amplitude relationship a fixed capacitor is connected across specific pairs of the transmission lines. The point of connection of that capacitor to the transmission lines is chosen to properly tune the network.

Abstract: A capacitance measuring circuit uses only a DC voltage source to perform the capacitance measurement. For this purpose, the circuit is arranged to charge an unknown capacitor which is being measured from a DC source and to discharge the capacitor through a constant current circuit such that the discharge voltage across the capacitor decreases linearly from its initial value to a predetermined, final value. The measurement circuit monitors the time taken by the capacitor to discharge in order to determine the capacitance value.

Abstract: In a magnetic resonance imaging tomography apparatus having a transmission antenna for exciting nuclear spins in an examination subject, and a reception antenna in the form of a local coil, the feeder for the local coil is provided with decoupling elements. The decoupling elements prevent a coupling of the electrical field of the transmission antenna with the feeder for the local coil.

Abstract: A resonator is provided for electron spin resonance spectroscopy. The resonator comprises a first wall element which delimits a cavity and which is in releasable contact with other wall element delimiting the cavity. The connection between the first wall element and at least one of the additional wall elements is effected only by spring force (single figure).

Abstract: A resonator is provided for electron spin resonance spectroscopy. It comprises a resonant element comprising a cavity, and a predetermined oscillation mode is capable of propagating in the cavity. The resonator comprises further a coupling element comprising a waveguide section. Finally, the resonator is equipped with a tuning arrangement for coupling an electromagnetic wave in the waveguide section with the oscillation mode in the cavity. The tuning arrangement comprises at least one conductive wafer, which is arranged at the free end of a tuning rod projecting into the waveguide section and is adapted for displacement in the direction of a longitudinal axis of the tuning rod. The wafer further coacts with a coupling element disposed between the waveguide section and the cavity. Two wafers are arranged on either side of the coupling element, in the direction of the longitudinal axis, and can be displaced in opposite senses relative to the coupling element.

Abstract: A local coil assembly includes an RF coil disposed inside a cylindrical form and a pair of z-axis gradient coils wound around the outside of the cylindrical form. First and second pairs of gradient coils are mounted on opposite sides and extend radially outward from the cylindrical form. These pairs of gradient coils produce a gradient field perpendicular to the z-axis with minimal effect on the operation of the RF coil.

Abstract: RF coils for a nuclear magnetic resonance device having following features separated or combined at an intersecting portion of two conductive loops disposed so that sensitive directions thereof are substantially perpendicular to a direction of a static magnetic field and that the conductive loops intersect each other with a predetermined interval; (1) conductors of conductive loops are narrowed; (2) neighborhood of intersecting portion is grounded; and (3) a member having a small dielectric constant is put inside of an intersecting portion.

Abstract: A digital data propagation delay margin monitoring circuit that includes (a) a digital data propagation unit having a send flip-flop, a combinatorial delay, and a receive flip-flop; and (b) a margin detection circuit having a test flip-flop that receives the same input as the receive flip-flop and is configured to have a set up time margin or a hold time margin that is less than the set up margin or hold time margin of the receive flip-flop by a predetermined amount, depending upon which margin is being monitored. The outputs of the receive flip-flop and the test flip-flop are compared by a comparison circuit which provides an indication of when the outputs of the receive flip-flop and the test flip-flop are different, which indicates that the monitored margin of the receive flip-flop has been reduced to a predetermined margin or less.

Abstract: A nuclear magnetic resonance (NMR) logging system includes a NMR logging tool adapted to be disposed in a borehole and a processing system adapted to be disposed on the surface of the borehole, the logging tool including a microcomputer, the processing system including a computer; and a signal processing system in accordance with the present invention having a first part stored in the downhole microcomputer of the logging tool and a second part stored in the surface oriented computer of the processing system. In the downhole microcomputer, using the first part of the signal processing system, a plurality of signal plus noise amplitudes are produced from a set of measured spin echo data, and a plurality N.sub.w of the window sums I.sub.m,m+1 are produced from the signal plus noise ampltudes, the window sums being transmitted uphole to the processing system.

Abstract: A method of electron spin resonance enhanced magnetic resonance imaging of a paramagnetic substance-containing sample wherein an image of at least part of the sample is generated from a data set produced by manipulation of enhanced free induction decay signals detected under at least two different sets of operational parameters. The operating parameters which are varied to produce the different sets include the timing of the exposure of the sample to magnetic field gradients and spin resonance stimulating radiations and, optionally, also the amplitude and frequency distribution of the electron spin resonance stimulating radiations. The manipulation of the detected signals produces, for individual image elements, a normalized signal representative of the difference between signals for that element under the different sets of operational parameters.

Abstract: An examination region (12) is defined within the bore of a superconducting magnet assembly (10). An RF coil (22) and gradient magnetic field coils (14) are disposed within the bore of the superconducting magnet assembly around the examination region. The superconducting magnet includes a hollow, cylindrical vacuum vessel (40). An annular, liquid helium holding low temperature reservoir (60) extends centrally through the vacuum vessel, but is sealed therefrom such that liquid helium is not drawn into the vacuum. A plurality of annular superconducting magnets (56) are received in the low temperature reservoir immersed in the liquid helium. A first cold shield (44) and a second cold shield (50) are mounted in the vacuum vessel surrounding the low temperature reservoir. A main magnetic field shield coil (66) is disposed in the low temperature reservoir outside of the annular superconducting magnets for canceling the magnetic field generated by the annular magnets surrounding the magnet.

Abstract: A cylindrical whole body MRI z gradient coil having multiple windings which are individually wound about a cylindrical support structure such that the windings are evenly distributed in azimuthal angle and interleaved with one another. The windings are preferably spaced in azimuthal angle by 360.degree./N, where N is the number of windings. In such a design, there is no net gradient along any transverse direction and the homogeneity of the gradient field in the transverse direction is thereby improved due to the resultant cancellation in terms proportional to the transverse field gradients. The multiple windings may be selectively connected in series or parallel in accordance with the output impedance and inductance of the current supply.