Abstract: Magnetic resonance imaging data of a volume of interest is collected by applying a radio frequency pulse (70, 96) and following the pulse with gradients applied along three axes (x,y,z). The gradients along x and y-axes are generally sinusoidal, which sinusoids increase and decrease in magnitude to define beat patterns of a common period. The period of the first and second gradients is an integer multiple of the gradient along the z-axis. In the embodiment of FIGS. 2A and 2B, the beats of the first and second gradients increase linearly and the third gradient oscillates in a linearly expanding generally sinusoidal pattern such that k-space is traversed by a trajectory that spirals around a series of spheres (50, 52, 54, 56, 58, 60) of progressively smaller radius. Blips or spikes (78) are preferably applied between each half cycle of the third gradient to step the trajectory to the radius of the next concentric sphere. In the embodiment of FIGS.

Abstract: B.sub.1 (RF) gradient echo pulse sequences are combined with frequency-selective pulse sequences to selectively suppress a solvent resonance signal by preventing the formation of an echo for the solvent resonance, while allowing the formation of an echo for the sample resonances under study. The RF gradient pulses may be planar or radial pulses. A pulse sequence for suppressing a solvent resonance signal in NMR experiments comprises a pair of (RF) gradient pulses which sandwich a selective inversion pulse sequence. In accordance with one embodiment of the invention, the RF gradient pulses are anti-symmetric (have opposite phase) and the selective inversion pulse sequence comprises a homogeneous frequency-selective inversion pulse, such as a .pi. pulse, applied in time between the two RF gradient pulses.

Abstract: A local gradient coil for use in magnetic resonance imaging provides a system of windings that produces a non-monotonic gradient field. The non-monotonic field provides spatially separate regions experiencing similar gradients and thus does not uniquely identify spatially separate spins. Multiple receiving coils positioned near each of the regions of similar gradient field strength are used to receive the multiple NMR signals. A determination of the sensitivity of these receiving coils may be used to determine the contribution from each spin to the signal produced by each coil thus allowing the superimposed signals to be separated.

Abstract: A generation of magnetic fields for a nuclear magnetic resonance imaging capable of preventing the occurrence of the cross-talk between coils for generating the magnetic fields easily. A coil system having a plurality of channels for generating magnetic fields is provided, and currents to drive the coil system is supplied from a power source. A controller generates the control signals indicating desired currents to be supplied from the power source to the coil system in an absence of cross-talks among the channels of the coil system, and then the cross-talks among the channels of the coil system are compensated by supplying the power source with cross-talk compensated control signals for controlling the currents to be supplied from the the power source to the coil system, where the cross-talk compensated control signals are obtained by adding the control signals with cross-talk compensation components derived according to predetermined cross-talk characteristics of the channels of the coil system.

Abstract: A method and apparatus for detecting spin transitions for a paramagnetic substance that are induced in the absence of a magnetic field. The method includes the steps of placing a substance under investigation in a high magnetic field. The magnetic field is then rapidly turned off and then reenergized. An ESR signal obtained after the magnetic field is reenergized is used as a baseline. This process is then repeated except that when the magnetic field strength is reduced to zero, the substance is exposed to radio frequency (rf) electromagnetic energy. Any spin transitions induced in the substance by absorption of the rf energy are detected by comparing the resulting ESR signal, detected when the magnetic is reenergized, to the baseline ESR signal.

Abstract: A high-speed magnetic resonance spectroscopic imaging method for obtaining information relating to an object placed in a space by irradiating the object placed in the space applied with a static magnetic field and field gradients in three different directions so as to excite a nuclear spin in the object. At least one of the field gradients is applied while inverting a sign thereof periodically and a magnetic resonance signal generated by excitation of the nuclear spin is measured. A Fourier transform is applied to the measured magnetic resonance signal thereby to obtain a chemical shift image and a measurement spectral bandwidth is set to a value not larger than a frequency difference between two different chemical shifts having frequencies remotest from each other among a plurality of chemical shifts intended to be measured, the measurement spectral bandwidth being determined by a reciprocal of an inversion period of the field gradient which is applied while inverting a sign thereof periodically.

Abstract: An MRI system includes a noise filter which receives each acquired NMR signal during a scan and detects short-duration noise pulses by sensing the signal level in a band of frequencies outside the imaging bandwidth. A blanking circuit suppresses the NMR signal during the time interval each noise pulse is detected to remove the noise pulse prior to image reconstruction.

Abstract: Nuclear spins are excited in an examination subject by a sequence of radio-frequency pulses that are emitted in under the influence of slice selection gradients, with n different slices of the examination subject being excited. Due to read-out gradients, n gradient echoes respectively allocated to a slice are generated such that each gradient echo allocated to a radio-frequency pulse comes to lie between two successive radio-frequency pulses. Further slices can thus be excited within the echo time of a gradient echo of a specific slice. A T.sub.2.sup.* contrast image can thus be obtained with a significantly shorter examination time than was heretofore achievable.

Abstract: A flow differentiation scheme is disclosed for magnetic resonance imaging (MRI) of fluid flow in regions of turbulent flow. The flow differentiation scheme comprises the steps of (1) obtaining a first magnetic resonance (MR) image of the region, (2) obtaining a second MR image of the same region with an imaging parameter or imaging sequence altered, and (3) logically differentiating the first and second images with respect to flow to create a difference image. The process may be enhanced by superimposing one of the original images, upon an image that has been flow differentiated. As a result, a substantial amount of the static signal is suppressed producing superior angiograms of diseased and undiseased blood vessels. Additionally, the scheme can be used to image any fluid flow in any body or thing.

Abstract: For shortening the measuring time to obtain an image identifying blood flow in a subject using magnetic resonance imaging, the number of phase-coding steps is reduced compared to a number of steps required for generating a quadratic observation window, given a constant, maximum amplitude of the phase-coding gradient. The reduction is to such an extent that only the blood vessel under observation is essentially acquired in phase-coding direction. Neighboring regions are saturated in order to avoid image artifacts. Given a correspondingly low number of phase-coding steps, a measurement of blood flow is possible in real-time presentation or, given an ECG triggered measuring sequence, a measurement of blood flow is possible in a greatly shortened overall measuring time.

Abstract: A method and apparatus is disclosed for efficient processing of nuclear magnetic resonance (NMR) echo trains in well logging. Apriori information about the nature of the expected signals is used to obtain an approximation of the signal using a set of pre-selected basis functions. A singular value decomposition (SVD) is applied to a matrix incorporating information about the basis functions, and is stored off-line in a memory. During the actual measurement, the apparatus estimates a parameter related to the SNR of the received NMR echo trains and uses it to determine a signal approximation model in conjunction with the SVD of the basis function matrix. This approximation is used to determine in real time attributes of the earth formation being investigated.

Abstract: Hybrid imaging (HI) sequences used for magnetic resonance (MR) imaging and inherently degraded by T2 effects and additive measurement noise are enhanced. Wiener filter and linear prediction (LP) technique is used to process HI MR signals in the spatial frequency domain (K-space) and the hybrid domain respectively. Based on the average amplitude symmetry constraint of the spin echo signal, the amplitude frequency response function of the T2 distortion is estimated and used in the Wiener filter for a global T2 amplitude restoration. Then a linear prediction technique is utilized to obtain local signal amplitude and phase estimates around discontinuities of the frequency response function of the equivalent T2 distortion filter. These estimates are used to make local amplitude and phase corrections. The effectiveness of this combined technique in correcting T2 distortion and reducing the measurement noise is analyzed and demonstrated using experiments on both phantoms and humans.

Abstract: A method of simultaneously imaging multiple components of velocity of moving materials within a subject employs magnetic resonance. Velocity encoding is performed by computing differences of data obtained with modulated motion encoding magnetic field gradient pulses. Distributions of velocity are measured responsive to a motion sensitive phase encoding gradient pulse.

Abstract: A method for using a remotely positionable MRI device to construct an image of a slice of in situ biological tissue includes creating and combining NMR images of subslices of the total slice of tissue to be imaged. More specifically, with the device positioned to record nuclei spin echoes from the slice of tissue to be imaged, the slice is divided into n different subslices and these subslices are imaged using a particular Larmor frequency for each subslice. In accordance with the present invention, n is an integer having a value less than T.sub.1 /T.sub.2, where T.sub.1 is the spin lattice relaxation time of the nuclei being imaged and T.sub.2 is the spin-spin relaxation time of the nuclei being imaged (n is approximately equal to 10). All n subslice images are then combined to create the image for the slice.

Abstract: In magnetic resonance imaging, prepared first is a three-dimensional image data consisting of a plurality of tomographic image data of a diagnostic portion of an object being examined. Then, data of a pilot image in the three-dimensional image data are designated, and the pilot image is displayed. Then, a linear ROI (region of interest) is placed on the displayed pilot image. Then, image data of a cross-section are edited from the three-dimensional image data, the cross-section passing through the linear ROI in a space of the three-dimensional image data. On the basis of the edited image data of the cross-section, a prediction image for scan is displayed.

Abstract: Magnetic resonance is excited in selected portions of a subject disposed within a temporally uniform magnetic field of a magnetic resonance imaging system. A quadrature coil assembly (30) receives radio frequency magnetic resonance signals from the subject. Commonly, the quadrature coil fails to receive signals in true quadrature over the entire examination region. Resonance signals from a first coil (32) and a second, orthogonal coil (34) are received (40, 42), digitized (44, 46), and Fourier transformed (50, 52) into complex images. Each complex image includes an array or grid of vector data values having a magnitude and a direction or phase angle. If the quadrature coil was truly quadrature over the entire region of interest, the data values of both complex images would be a unit vectors. The vector of one image would be offset by 90.degree. from the vectors of the other.

Abstract: A variable geometry coil system includes a single fixed horizontal coil and a vertically oriented pair of movable coils interconnected through an electronic matrix to allow for a multi-mode system which enables either the vertical pair or the horizontal coil to function alone or to enable a quadrature combination of the coils for optimum signal performance. The vertical coil pair includes two matched coils which are loaded to reduce their tuning sharpness so as to eliminate the need for clinical tuning prior to utilization. Signal losses incurred by the Q reduction are compensated for by including an integrated preamplifier at the signal output.

Abstract: In an image reconstruction method in a nuclear magnetic resonance imaging apparatus, the method comprises first and second steps to get detected data S.sub.I for at least about half of region inclusive of an origin and data S.sub.IV in a region symmetric with respect to a line passing through an origin on one of axes from the detected region in the acquired data space and parallel to the other axis, respectively, third and fourth steps to perform inverse Fourier transform on the data S.sub.I and S.sub.

Abstract: An EPR imager and spectrometer includes pulse generating system for generating broadband pulses having an RF carrier frequency that is not highly absorbed by biological samples. The pulse generating system includes up and down chirp convertors for frequency modulating a carrier frequency pulse and compressing the frequency modulated pulse to form a broadband excitation pulse of high energy. Such a machine could form the basis of a clinical imaging device capable of high sensitivity to free radical species in human patients.

Abstract: A local coil for use with an MRI system to acquire images of a patient's legs includes a vertically disposed central coil positioned between the legs, and a pair of horizontally disposed flange coils positioned above and below the legs. In one embodiment of the central coil is a phased array of two coils, and the four coils are connected to the respective inputs of a four channel receiver, and in a second embodiment, the signals from the three coils are combined before application to the input of a single-channel receiver.