Abstract: The frictional heating of an NMR sample spinner supported on a cylindrical gas bearing inside a cylindrical bearing stator is negated by recirculating the turbine exhaust gas over the rotor surface inside the RF coil. The technique is more effective with microturbines of relatively high insentropic efficiency. Plugs extend axially into the sample container from each end so that the sample is confined to the central region beyond the gas bearing region so the thermal gradients are minimized and RF homogeneity is improved.

Abstract: The present invention is a method to rapidly determine the fluid-flow permeability of porous media with nuclear magnetic resonance (NMR). The method can be applied to measurements of permeability in fluid-saturated earth formations using NMR logging tools.

Abstract: An apparatus for determining the polarities of bonding points to locate false bonding connections including an applied voltage output circuit which outputs positive and negative voltages, a switching circuit which after a wire is connected to a bonding point impresses voltage from the applied voltage output circuit to the bonding wire, a D/A converter which outputs standard positive and negative voltages, a polarity determining comparator which determines the polarity of the bonding point by comparing the voltage detected on the bonding wire with the standard voltage, and a memory which stores such a determination result for each bonding point.

Abstract: An automatic calibration circuit for a maximum and minimum value detection apparatus including a maximum value detection circuit for detecting and outputting a maximum value of an input signal, and a minimum value detection circuit for detecting and outputting a minimum value of the input signal. In a calibration mode, a reference signal of a fixed value is automatically inputted to the maximum value detection circuit and to the minimum value detection circuit upon entry of a calibration mode. An offset voltage of at least one of the maximum value detection circuit and the minimum value detection circuit is automatically adjusted so that the maximum value and the minimum value obtained in response to the reference signal become equal.

Abstract: A series topology is provided for the magnetic-field-generating coil and storage capacitor in the circuitry driving the coil of an MRI system. The coil and capacitor thus form a series resonant circuit that can deliver a sinusoidal current through the coil at a resonant frequency. A power source and switch are connected in series with the coil and capacitor, and current flow to the coil is initiated and interrupted by closing and opening the switch.

Abstract: Elimination of truncation artifacts in Magnetic Resonance Images is accomplished by analaytically optimizing controllable parameters; i.e., filter characteristic and assymetry ratio when asymetrically sampling arid time domain filtering followed by complex conjugating the filtered data to reduce the Gibbs artifact.

Abstract: An angiogram is produced using NMR fast pulse sequences in which the views are acquired in shots preceded by a preparatory pulse sequence. Each shot is acquired twice with differing preparatory pulse sequences and the resulting NMR data is subtracted to null the stationary tissues in the reconstructed image.

Abstract: A method for measuring cross-relation rates in high-resolution nuclear magnetic resonance (NMR) spectroscopy in which in a homogeneous static magnetic field B.sub.0 in a direction of a z-axis which causes alignment of longitudinal components I.sub.Z.sup.A, I.sub.Z.sup.X of magnetization vectors I.sup.A, I.sup.X of nuclei A, X during a time interval .tau..sub.m a sample substance, preferably dissolved in liquid, with nuclei A and X having different chemical shifts .OMEGA..sub.A and .OMEGA..sub.X is irradiated with a radio-frequency (rf) field and afterwards by action of a suitable rf-pulse sequence the longitudinal magnetization is transferred into a transverse magnetization creating a rf-signal received by a detector, is characterized in that the rf field is composed by at least two weak, selective component fields, the frequencies of these fields being chosen such that the magnetization vectors I.sup.A and I.sup.

Abstract: A new pulse sequence which uses inversion recovery for lipid suppression and a spectral-spatial refocusing pulse for water suppression in spectroscopic imaging of the brain. In contrast to methods which eliminate fat by restricting the excited volume to lie completely within the brain, inversion recovery techniques allow imaging of an entire slice without such restrictions. A spectral-spatial pulse provides water suppression insensitive to a reasonable range of B.sub.0 and B.sub.1 inhomogeneities. Metabolite maps covering large volumes of the human brain can be produced with images from single and multiple slices obtained.

Abstract: A method of vector magnetic resonance measuring and imaging and associated apparatus provide for a specimen being placed in a main magnetic field, RF pulses being impinged thereon, and magnetic field gradients being superimposed thereupon, preferably with three input gradient pulses being impinged preferably simultaneously to construct a balanced system of four gradient vectors having equally strong moments Four cycles of such input gradient pulses are employed to create four magnetic gradient moments from which velocity or motion vectors are created. A receiver obtains signals from a specimen and converts them into information which is introduced into a computer. The computer converts the signals sensitized by the gradient vector moments into motional-type vector information which can be measured and imaged. Different approaches may be taken for low velocity and high velocity usages.

Abstract: MRI T1 relaxometry is performed using a single fixed strength magnetic background field for RF signal transmission and reception thus greatly simplifying RF circuitry design and/or adjustment. Switched differing strength background magnetic fields are employed at other times in the relaxometry cycle so as to predominate the NMR T1 relaxation parameter value and thus permit relaxometry determinations of T1 values versus magnetic field strength (or the equivalent corresponding NMR RF frequency) at N data points using as few as N+1 measurement cycles. Process and apparatus are disclosed for thus efficiently achieving in vivo NMR relaxometry (including magnetic resonance imaging if desired).

Abstract: An NMR angiogram is produced from two data sets acquired using a fast pulse sequence. One data set is acquired with a readout gradient having a first moment of zero at each refocusing pulse and a first value at each acquired echo signal. A second data set is acquired with a readout gradient having a first moment of zero at each refocusing pulse and a second value at each acquired echo signal. Signals from stationary tissues are suppressed with a dephasing gradient pulse in the slice select direction applied after each refocusing pulse, and a corresponding rewinder gradient pulse is applied after each acquired echo signal.

Abstract: A novel channelized, hybrid time- and space-integrating acousto-optic (AO) spectrum analyzer is described. The architecture consists of two acousto-optic cells in a crossed cell configuration. The first acousto-optic cell is a wide bandwidth device that performs space-integrating spectral analysis and channelizes signals according to carrier frequency. The second acousto-optic cell, in conjunction with a modulated source, performs time-integrating spectral analysis of the signal envelope using the chirp algorithm. One possible application of the processor is to determine the carrier frequency and pulse repetition frequency (PRF) of received radar signals.

Abstract: Image artifacts caused by flowing spins during a fast spin echo pulse sequence are suppressed by employing gradient moment nulling. The first moment of one or more gradients is nulled at each RF refocusing pulse in the sequence, and in alternative embodiments, the first moment is also nulled at each acquired NMR echo signal.

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 magnetic assembly around the examination region. The superconducting magnet includes a hollow, tubular vacuum vessel (40) which contains a plurality of annular superconducting magnets (58). These superconducting magnets are held in a liquid helium holding reservoir (60) such that they are held below their superconducting temperature. A first cold shield (44) and a second cold shield (50 ) have tubular portions between the superconducting magnets and the examination region. These cylindrical portions each include a cylinder (70) of a electrically insulating material such as reinforced plastic. Thermally conductive layers (72) are defined on each surface and are divided by etched slots or resistance portions (74) into a multiplicity of elongated narrow segments (92).

Abstract: Nuclear magnetic resonance well logging apparatus and a method of use for geophysical examination of a bore hole as the bore hole is drilled. The apparatus is connected to the drill bit to follow it through the bore hole as the bore hole is formed. The apparatus comprises a resilient, tubular, permanent magnet for generating a static magnetic field in the region of a portion of the bore hole adjacent the apparatus, which region includes materials sought to be analyzed, an antenna mounted on the magnet and connected to associated circuitry for exciting nuclei of the materials sought to be analyzed in the region, and a receiver connected to the antenna for receiving nuclear magnetic resonance signals from the excited nuclei and for providing an output signal indicative of properties of the materials sought to be analyzed.

Abstract: A method and circuit for operating a magnetic resonance imaging apparatus to produce tomograms in an arbitrary position (plane) generate logic gradients which are arbitrarily spatially oriented by a combination of a number of physical magnetic field gradients. At least one gradient coil is operated in a resonant circuit. The logic gradients do not chronologically overlap. A logic read-out gradient can have gaps (non-signal regions) in the region of its zero-axis crossings, at which time a logic phase-coding gradient can be activated.

Abstract: In addition to the usual winding of an MRI RF receive coil, a second, opposite sense, winding is connected to the same pair of RF output terminals and linked to at least part of the same space as the first winding. One or more serially connected RF switches in the second winding selectively connect it in circuit only during transmission of NMR RF nutation pulses. Under these conditions, any transmitted RF fields linked to the first winding are also linked to the second winding. Accordingly, any induced RF currents flowing in the receive coil windings produce self-cancelling effects in the tissue being imaged (thereby reducing possible distortion of the desired transmit fields being used for NMR nutation purposes).

Abstract: The fluid transport properties of a porous media are determined by NMR imaging showing the fluid transport properties such as fluid velocity, fluid acceleration, fluid jerk, translational self diffusion, sample permeability to fluid transport, etc.

Abstract: An examination region (12) is defined along a z-axis offset from a geometric center (30) of a gradient coil assembly (20). Cylinders of a non-conductive, non-magnetic material support x, y, and z-gradient coils (24, 26, 22) for causing orthogonal magnetic field gradients through the offset examination region. The z-gradient coil (FIG. 2 ) includes a plurality of distributed loop arrays with a winding pattern selected to cause a region of linear magnetic field gradients in the z-direction in a region offset toward a cylinder first end (32). The x and y-gradient coils each include two pairs of oppositely disposed windings (FIG. 3 ) which include a pair of inner spirals (96, 98) offset towards the first end of the cylinder and an outer spiral (90) extending therearound. The outer spiral bows in (92) toward the cylinder first end and fans out (94) toward the second end.