Abstract: Reception signal processing apparatus in nuclear magnetic resonance diagnostic apparatus to display as an image the distribution of the spin density or relaxation time of specific atomic nuclei existing in an object utilizing nuclear magnetic resonance phenomena including a phase demodulator for phase demodulating a nuclear magnetic resonance signal evoked by nuclear magnetic resonance phenomena in accordance with two reference waves, the phases of which are different by 90.degree., an analog-to-digital convertor for digitalizing the separated two signals obtained by the phase demodulator, and a noise correction processor for eliminating the low frequency component noises included in the demodulated signals from the phase demodulator to obtain an image without artifacts.

Abstract: A circuit arrangement is described for preventing a reaction of a coil on an external high-frequency field of predetermined frequency containing the coil due to a current induced by the field in the coil for a multiple-coil probe of a nuclear magnetic resonance apparatus wherein the coil is coupled via a high-frequency line of predetermined characteristic impedance to a switching element and a circuit unit cooperating with the coil. The electrical length of the high-frequency line between the coil and the switching element is so dimensioned that any undesired reaction of an inactive coil on the other coil(s) is eliminated.

Abstract: System of coils for producing additional fields in a magnet having pole pieces for producing images by nuclear magnetic resonance. For producing gradients Gx=(.differential.Bz/.differential.x) and Gy=(.differential.Bz/.differential.y), it comprises two layers of orthogonal windings, one on each pole piece. For producing the gradient Gz=(.differential.Bz/.differential.z), it has two systems of windings of circular symmetry and axis Oz, located on the inner facing faces of the pole pieces and traversed by currents whose direction changes between the individual pole pieces.

Abstract: Use of a switch at the end of a .lambda./4 cable inserted between the Rf coil and ground allows the coil to be tuned and detuned at will. This detune switch essentially eliminates coupling between adjacent coils permitting operation of multiple transmit coils at the same frequency. These switches have been employed to prove a previously proposed method of complete sensitive-volume localization using multiple Rf coils and depth pulse schemes. The example illustrated is the case of two coaxial coplanar surface coils. There are important uses in in-vivo spectroscopy.

Abstract: A method of obtaining a localized nuclear magnetic reasonance signal from a sample using a radiofrequency irradiation coil which provides an inhomogeneous radiofrequency field, comprisesapplying to the sample a plurality of radiofrequency pulse sequences, each pulse sequence including an excitation pulse, and at least two other pulses, the pulse sequences differing only in the phase of one or more of the said other pulses, and the phases of at least two of the said other pulses being shifted by 180.degree. in selected sequences of the said plurality, the number of sequences in the said plurality being such that a sequence exists for each possible combination of the said phase shifts for each of the said other pulses, and there being no sequences in the said plurality in which the phases of the said at least two of the said other pulses is shifted by 90.degree.,acquiring an N.M.R. signal after each pulse sequence,and combining the N.M.R. signals obtained to produce a localized N.M.R.

Abstract: An RF field generator and detector comprising an RF coil having an inductance and at least one conductor which includes at least first and second separated parts arranged to form stray capacitance between them, capacitors for impedance matching which are connected to the RF coil, and a balanced-to-unbalanced transformer by which a balanced load composed of the RF coil and the capacitors is coupled to an unbalanced RF transmitter and receiver, the stray capacitance being adjusted thereby to equivalently reduce the inductance of the RF coil.

Abstract: A local probe for use in nuclear magnetic resonance imaging includes a pair of loop-gap resonators which are connected together and positioned adjacent a region of interest. FID signals produced in the region of interest induce signals in coupling loops mounted near each loop-gap resonator, and these connect to a transmission line leading to the receiver. Three embodiments are disclosed, one best suited for imaging appendages, a second best suited for imaging the head and neck, and a third best suited for the spine.

Abstract: Methods are disclosed which provide for quantifying and characterizing the mineral content of a formation as a function of depth. Elemental data derived from logging tools are input into an element-mineral transform operation, to determine the quantity of at least one or more dominant minerals in the formation including minerals distinguishable by degree of crystallinity. From the mineral quantity information and the elemental log data, the formation minerals are further characterized. Information regarding the character and quantities of formation minerals is further used to obtain improved determinations of formation characteristics such as the cation exchange capacity and water saturation, and the grain density and formation porosity, as well as to obtain an increased understanding of the formation such as the depositional environment of the formation.

Abstract: Apparatus for collecting a plurality of samples of fluids in earth formations traversed by a wellbore includes control circuits for supplying power control signals to the subsurface instrument. The control circuits include circuitry for establishing electrical connection to the hydraulic power system of the instrument and after a preselected period of delay supplying power signals to a hydraulic pump motor and/or solenoid valve controls therein. Current is monitored by over-current protection circuitry. In the instance of a current overload, power signals are removed from the hydraulic power system and after a preselected period of delay the control circuits are disconnected from the instrument.

Abstract: NMR imaging apparatus and method is arranged so as elicit NMR image response data in a predetermined order which provides the more significant lower spatial frequency image data during an initial portion of a relatively long complete image data acquisition cycle. The remaining higher spatial frequency image data is captured during subsequent portions of the overall image data acquisition cycle. In this manner, apparent motion artifact in the resulting image is reduced. Furthermore, such a special data acquisition sequence permits image reconstruction processes to produce a recognizable image at an earlier time in the complete data gathering cycle thus permitting a more timely image display for the apparatus operator to use in monitoring and/or controlling the NMR imaging procedure.

Abstract: Radio frequency apparatus for a magnetic resonance system is provided which includes an r.f. coil and DC controlled circuitry for selectively altering the characteristics of the coil. A loading coil is provided which is selectively activated to de-Q the coil during r.f. transmission so as to minimize the loading effects of the subject and their effect on coil impedance. A switched network is provided which selectively destroys the normal resonant condition of the coil when a second r.f. coil is operative to minimize interaction between the two coils.

Abstract: A coil arrangement for producing a static magnetic field comprising a central coil and two outer coils disposed on opposite sides of the central coil. The positions and dimensions of the coils are so selected that each term contained in the Taylor series of the function of the magnetic field in the axial direction (z axis) of the coil arrangement in minimized. The current density in the central portion of the central coil is made to be higher than at other portions. The inventive coil arrangement is smaller in size, lighter in weight, and consumers a smaller amount of power than the prior art for the same magnetic strength and with a better homogeneous magnetic field.

Abstract: The azimuthal direction of the mechanical anisotropy of a material is measured by using a first transducer to transmit shear acoustic energy through the material and a second transducer, cross-polarized with respect to the first transducer, to receive the shear acoustic energy after it has traveled through the material. Amplitude and phase of the cross-polarized shear acoustic energy are measured as a function of the azimuthal rotation of the shear acoustic energy transducers with respect to the material.

Abstract: In accordance with the invention, two detection periods t.sub.2 and t.sub.2 ' are set by the use of a pulse train essentially consisting of three pulses. Free induction decay signals FIDa and FIDb obtained during the two periods, respectively, are stored in respective data files. The measurement is repeated a plurality of times while putting at least one of the three pulses of the pulse train out of phase with the others. The free induction decay signals FIDa and FIDb derived by each measurement are stored in their respective data files. After the measurements, a linear combination of the data items which are stored in the data files assigned either to the signals FIDa or to FIDb is formed. The resultant data is subjected to double Fourier transformation to obtain a two-dimensional NMR spectrum. The manner in which the data items are linearly combined is appropriately selected to obtain a desired kind of two-dimensional NMR spectrum.

Abstract: Methods are disclosed which provide for quantifying and characterizing the mineral content of a formation as a function of depth. Elemental data derived from logging tools are input into an element-mineral transform operation, preferably a matrix which is constructed using multivariate statistical analysis on previously available data, to determine the quantity of at least one or more dominant minerals in the formation. From the mineral quantity information and the elemental log data, the formation minerals are further characterized. Information regarding the character and quantities of formation minerals is further used to obtain improved determinations of formation characteristics such as the cation exchange capacity and water saturation, and the grain density and formation porosity, as well as to obtain an increased understanding of the formation such as the depositional environment of the formation.

Abstract: In an improved NMR imaging method, where three-nominally orthogonal gradient fields are generated, the quantization error of the phase encode gradient is reduced without the necessity of a digital to analog converter of higher bit capacity. This is accomplished in one embodiment by providing a second smaller gradient waveform which is relatively narrow compared to the primary gradient waveform, the ratio of the waveforms being proportional to the improved resolution. The second waveform can occur either before or after the 180.degree. excitation pulse used to produce a spin-echo signal. In another embodiment pulse width modulation is used to vary the area of the phase encode waveform in discrete increments.

Abstract: The present invention is an improved mud excluder fitted around a rotating acoustic transducer of a borehole televiewer to exclude mud from the borehole televiewer. This mud excluder has:(a) a flexible casing means attached to the borehole televiewer to form a fluid cavity adjacent to the rotating acoustic transducer,(b) an acoustically transparent fluid located within the fluid cavity,(c) an acoustic window means opposite the transducer and adjacent to the fluid cavity, and(d) a pressure compensating means within the fluid cavity to equalize the pressure within the fluid cavity with the pressure on the outside of the flexible casing means.

Abstract: A bundle type gauge carrier including a support assembly which may be loaded with a plurality of downhole gauges, the support assembly being quickly insertable in a case assembly incorporated in the pipe string used for a formation test. The gauges are grouped in the support assembly about an unobstructed central flow path, whereby each gauge is exposed to the pressure and temperature of the flowing oil and gas during a drill stem test.

Abstract: An R.F. coil system is described for generating and/or receiving at least substantially homogeneous alternating magnetic fields, notably in nuclear magnetic resonance apparatus. The system is arranged about an essentially cylindrical examination space and comprises at least four conductor segments which are oriented essentially parallel to the longitudinal central axis of the examination space. The conductor segments are arranged about the circumference of the examination space symmetrically with respect to at least one plane which extends through the longitudinal central axis and are interconnected so as to form a closed loop. The conductor segments which receive a current of the same sense with respect to the longitudinal axis, are interconnected at neighboring ends by conductor elements which are oriented essentially in the circumferential direction of the examination space so as to form conductor groups.

Abstract: The invention relates to an RF (=radio frequency) coil arrangement for an NMR examination apparatus, an object or target to be examined, e.g. a patient or part of a patient being adapted to be placed inside said coil arrangement which is adapted to excite the nuclei of a selected target area by transmitting an RF pulse substantially orthogonal to a homogeneous basic magnetic field produced by the apparatus and, thereafter, to receive and detect an NMR signal generated in the target. In order to eliminate the drawbacks of a so-called saddle coil conventionally used as an RF coil the invention is characterized in that it comprises a transfer line, continuous and wired in a manner that its various parts induce an RF field of different direction. Both in excitation and detection of signals, said transfer line can be adapted to process a magnetic field rotating in just one direction and it can be connected as an endless loop.