Abstract: A magnetic resonance (MR) imaging apparatus and technique exploits spatial information inherent in a surface coil array to increase MR image acquisition speed, resolution and/or field of view. Partial signals are acquired simultaneously in the component coils of the array and formed into two or more signals corresponding to orthogonal spatial representations. In a Fourier embodiment, lines of the k-space matrix required for image production are formed using a set of separate, preferably linear combinations of the component coil signals to substitute for spatial modulations normally produced by phase encoding gradients. The signal combining may proceed in a parallel or flow-through fashion, or as post-processing, which in either case reduces the need for time-consuming gradient switching and expensive fast magnet arrangements. In the post-processing approach, stored signals are combined after the fact to yield the full data matrix.

Abstract: Potential producibility and the proportion of water and oil produced can be predicted for hydrocarbon bearing reservoirs using an isolated pore model and nuclear magnetic resonance data. The model is based on the use of two bulk volume irreducible/free fluid index cut off times, one based on small pores and the other based on large pores with a throat size that will not permit movement of fluids therefrom.

Abstract: A method is disclosed for determining a nuclear magnetic resonance characteristic and the resistivity of earth formations surrounding a borehole, including the following steps: passing a logging device through the borehole; producing, at the logging device, a static magnetic field; producing, at the logging device, electromagnetic energy having a field component in the formations that is orthogonal to the static magnetic field; receiving, at the logging device, electromagnetic energy that has passed through said formations; and determining, from the received electromagnetic energy, the nuclear magnetic resonance characteristic of the formations and the resistivity of the formations.

Abstract: An RF pulse for an NMR pulse sequence is designed in the NMR system using an inverse SLR transformation method. The polynomials required for the SLR transformation are calculated using a weighted least mean squares ("WLMS") process in which an initial weighting function is employed along with the desired pulse profile that is input by the NMR system operator. The operator can also specify the phase profile as an input to the WLMS process.

Abstract: For obtaining image information from a subject, in an excitation phase nuclear resonance signals are excited with wavelet-encoding by emitting a radio-frequency pulse under the influence of a gradient in a first direction, the pulse having an envelope that corresponds to the Fourier transforms of a wavelet function. In addition, a layer selection is achieved by the application of an oscillating gradient in a second direction. In a readout phase, a gradient echo signal is sampled under the influence of a readout gradient in a third direction. The pulse sequence can be repeated with a repetition time that is shorter than the longitudinal and transverse relaxation time, so that a steady state arises.

Abstract: In a nuclear magnetic resonance tomography apparatus and a method in the form of a pulse sequence for operating the apparatus, after an excitation of spins in a subject, two groups of nuclear magnetic resonance signals are obtained in two time intervals at different chronological spacings from the excitation time. An image is obtained on the basis of the signal differences of nuclear magnetic resonance signals of the first and second groups with corresponding locus-encoding. Signal contributions from tissues with longer T2 relaxation time can thereby be screened out.

Abstract: In a nuclear magnetic resonance tomography apparatus wherein image information are sampled in time measurement windows with a sampling grid that is not equidistant in time and are digitized, for D.C. offset compensation in at least one measurement window, the output signal of the measurement channel is sampled without a nuclear magnetic resonance signal, is digitized, and the offset data acquired in this way are stored in an offset vector. The n offset data stored in the offset vector are subtracted from the image raw data that are acquired per measurement window and allocated chronologically in the sampling grid.

Abstract: An examination table for use with an imaging device is provided with a rolling track on an upper surface of a platform. A table is supported on the rolling track for movement relative to the platform. The imaging machine includes lower coils which are supported under the table and upper coils which are supported on the platform. The table and the rolling track are made from a non-ferromagnetic material so as not to interfere with the coils. The examination table can also be used with other imaging machines such as computed tomography and x-ray machines.

Abstract: Susceptibility artifacts in slice selective volume magnetic resonance spectroscopy are reduced by applying phase encoding at a nominal resolution equal to or larger than the slice selection dimensions. In a preferred embodiment of the method, phase encoding is applied along the axes of the first and last RF slice selections. The volume of interest is contained completely within a single pixel defined by the 2D phase encoding. Unsuppressed water reference signal from the volume of interest is relatively unaffected by these artifacts and is collected without phase encoding.

Abstract: A process of controlling the blending of components to produce a product composition at a target value for least one characteristic has been developed. The process involves varying the proportion of the components, determining with each variation the change in the value of a characteristic using nuclear magnetic resonance spectroscopy, adjusting the proportion of those components to afford a new composition where the value of the characteristic is numerically closer to the target value, and repeating the steps until the target value of the characteristic is achieved. The process further includes determining blending factors to be used in existing blending equations.

Abstract: A magnetic-resonance-imaging (MRI) scanner subassembly. In one subassembly, a preferably annularly-cylindrical-shaped enclosure contains a first vacuum, and an MRI gradient coil assembly is located within the enclosure in the first vacuum. Preferably, an annularly-cylindrical housing is included which is coaxially aligned with the enclosure and contains a second vacuum which is higher than the first vacuum, and an MRI superconductive main coil is located within the housing in the second vacuum. In another subassembly, an MRI gradient coil assembly has a threshold excitation frequency, and an isolation mount assemblage supports the MRI gradient coil assembly.

Abstract: A phase unwrapping method is provided comprising a post-processing MR operation for an array of phase-related MR data elements. The method includes the steps of defining a Region of Interest, of comparing each data element with the first and second data elements which are adjacent thereto in the array, in order to generate respectively corresponding first and second gradient values. A subset of the data elements is constructed, wherein a data element is assigned to the subset only if its corresponding first and second gradient values are less than a selected threshold value VENC/2. The data element subset is employed to generate a fitted phase function having a value at the position of each data element in the array, and the value of the fitted function thereof, for a given data element, is subtracted from the measured value thereof.

Abstract: In an MR imaging method, at least radio frequency pulses for excitation are repetitiously consecutively applied in accordance with predetermined pulse sequences until measurement of NMR signals corresponding to phase encoding numbers necessary for desired image construction ends, an external trigger signal synchronous with periodical motion of an object to be inspected is received during the period of application, and a gradient magnetic field having a phase encoding amount necessary for the image construction is applied at the termination of a predetermined time following the reception of the trigger signal to fetch at least one NMR signal. When a plurality of NMR signals are desired to be fetched, a plurality of gradient magnetic fields having mutually different phase encoding amounts are applied.

Abstract: A device for automatic impedance matching of an RF transmitter or receiver in a nuclear spin tomography installation, and method for operating the device. The impedance matching device contains an RF transmitter or receiver which is coupled via a matching circuit having two actuators to a transmitting or receiving antenna respectively. Furthermore, the device has a circuit for detecting the complex reflection factor at the input of the matching circuit as well as an electronic control device with calculating circuits for adjusting the actuators. According to the invention, the calculating circuits contain units for calculating the complex reflection factor of the antenna from the detected complex reflection factor, and for calculating the setting points of the actuators for a reflection factor of zero at the input of the matching circuit.

Abstract: An MRI system is provided for improving the magnetic coupling and positional relationship between gradient coils and shim coils, thus simplifying positioning of the coils (retention of orthogonality), designing an MRI system compactly, and reducing cost. An MRI system comprises a magnet generating a static magnetic field and a gradient coil unit generating a gradient magnetic field superposed on the static magnetic field. The gradient coil unit is formed into a substantially cylindrical shape having an outer circumferential surface, and shields the gradient magnetic field from being leaked out into a radially outer space. The MRI system further comprises a shim coil unit generating a correcting magnetic field homogenizing the static magnetic field. The shim coil unit is mounted on the outer circumferential surface of the gradient coil unit in common serving as a bobbin for the shim coil unit.

Abstract: Radiation damping effects in NMR are compensated by splitting the amplified NMR signal induced in the main probe coil to obtain a correction signal, phase shifting the correction signal to obtain a feedback signal and impressing the feedback signal onto the sample through means independent of the main probe coil.

Abstract: In an MR spectroscopy method nuclear magnetization of a plurality of voxels present at an area of intersection of two slices is simultaneously excited by repeated sequences, the resultant phase encoding of the voxels is varied from one sequence to another, and a spectral distribution of nuclear magnetization in the voxels is derived from linear combinations of the MR signals generated in the individual sequences. A method is obtained wherein each sequence a first slice-selective RF pulse is generated in order to excite the transverse magnetization in one or more first slices, and subsequently a second slice-selective RF pulse is generated in order to refocus nuclear magnetization in one or more second slices which intersect the first slices at an angle other than zero, and in the various sequences the MR signals produced by the spin echos in the voxels present at the area of intersection of each first and second slice is detected and used to determine the spectral distribution of the nuclear magnetization.

Abstract: An RF shield is provided to prevent coupling between the gradient coils and the RF coil of an MR imaging system, wherein the RF field rotates around the RF coil axis. The shield includes a number of coaxial conductive cylinders, and further includes a plurality of cylinders formed of dielectric material, each dielectric cylinder positioned between adjacent conductive cylinders. Each conductive cylinder is formed from sheets of copper, each sheet having a pattern of conductive loops formed therein, and each loop having an associated gap to prevent induction of eddy currents therein by gradient magnetic fields produced by the MR system gradient coils.

Abstract: A method for actively and passively shimming a magnet having a magnetic field inhomogeneity, correction coils, and shim locations. The magnetic field is measured, and the inhomogeneity determined. The magnetic field created by a known current in each correction coil and by a known shim at each shim location is determined. Using linear programming, the optimum currents and shim sizes together are determined which minimizes the inhomogeneity plus the total currents used plus the total shim sizes used.

Abstract: A magnetic resonance imaging apparatus includes a static magnetic field forming magnet, an RF coil and a transmitter/receiver adapted to transmit a 90.degree. rf pulse and a 180.degree. rf pulse in turn to a human body under examination and receive an echo signal from the human body, gradient magnetic field forming coils and gradient magnetic field power supplies adapted to form a first slice selection gradient magnetic field simultaneously with the 90.degree. rf pulse and a second slice selection gradient magnetic field simultaneously with the 180.degree. rf pulse, a computer system adapted to reconstruct a magnetic resonance image from the echo signal, and a display unit adapted to visualize the reconstructed magnetic resonance image. The frequency bandwidth of the 90.degree. rf pulse is adjusted so that a region in which proton spins in water are excited and a region in which proton spins in fat are excited will not overlap each other.