Abstract: The present invention discloses a nonvolatile memory with spacer trapping structure, the nonvolatile memory comprising a semiconductor substrate. A gate oxide is formed on the semiconductor substrate. A gate structure is formed on the gate oxide. An isolation layer is formed over the sidewall of the gate structure. First spacers are formed on the sidewall of the isolation layer and becoming the spacer trapping structure for storing carrier. And the p-n junctions of source and drain regions are formed adjacent to the gate structure. Silicide is formed on the gate structure and the source and drain regions.

Abstract: The subject invention relates to a method and apparatus for producing stimulated MRI data. In an embodiment, a remote-controlled “smart phantom” can produce simulated data. The simulated data can be acquired from a MRI system. The subject device can generate control signals and send the generated control signals to secondary coils/probes placed in the subject smart phantom. The control signals determine the current flow in the secondary coils/probes, which act as local spin magnetization amplifiers and thus produce regions of variable contrast to noise ratio. The control signals can be generated with various parameters, such as BOLD models, different levels of contrast-to-noise ratio (CNR), signal intensities, and physiological signals. Comparisons can be made with the widely-used simulated data by computers. Validation of the subject smart phantom can be performed with both theoretical analysis and data of human subjects.

Abstract: Methods and systems formulate the impedance for decoupling capacitors of a multiple power supply printed circuit board considering plane capacitance, series resonant frequencies, parallel resonant frequencies and impedance. The impedances are evaluated at anti-resonant frequencies, which have been found to be the problematic frequencies and potentials for high impedance. Once such impedance at selected frequencies have been determined, they can be compared to target values, set for example by various system integrity or EMI standards or design parameters, to assess whether a particular DC power supply system performs properly from signal integrity or electromagnetic radiation points of view. This ability to readily assess a high probability of compliance theoretically will reduce research and development time and budget, reducing possibly many iterations of board designs and trials and error physical testing.

Abstract: In a MRI system having a FID detector unit and a computer unit for processing FID signals, phase errors introduced into the FID signal at the detector unit are corrected at the computer unit by transmitting a pilot signal from the computer unit to the detector unit, processing the pilot unit along with a detected FID signal at the detector unit, transmitting the processed signals to the computer unit, obtaining the pilot signal and FID signal at the computer unit, and combining the pilot signal and the FID signal whereby phase errors cancel.

Abstract: A method for obtaining nuclear magnetic resonance measurements includes inducing a static magnetic field in a formation fluid sample; applying an oscillating magnetic field to the fluid sample according to a preparation pulse sequence that comprises a J-edit pulse sequence for developing J modulation; and acquiring the nuclear magnetic resonance measurements using a detection sequence, wherein the detection sequence comprises at least one 180-degree pulse. The method may further include acquiring the nuclear magnetic resonance measurements a plurality of times each with a different value in a variable delay in the J-edit pulse sequence; and analyzing amplitudes of the plurality of nuclear magnetic resonance measurements as a function of the variable delay to provide J coupling information.

Abstract: In a method for the operation of a magnetic resonance apparatus having a gradient system and a radio-frequency system that, among other things, are utilized for location coding of magnetic resonance signals, magnetic resonance signals from at least parts of a region of an examination subject to be imaged are acquired in a time sequence, and a deformation of the region to be imaged occurring during the time sequence is identified and the location coding is adapted according to the identified deformation.

Abstract: A decoupling circuit for decoupling an local coil during the application of an RF excitation signal in a magnetic resonance imaging system includes a passive switching circuit for switching an inductor in parallel with a capacitive circuit in the local coil, and a discharge circuit for discharging residual currents from the circuit, therefore allowing for rapid coupling and decoupling of the local coil.

Abstract: A decoupling circuit for decoupling an local coil during the application of an RF excitation signal in a magnetic resonance imaging system includes a passive switching circuit for switching an inductor in parallel with a capacitive circuit in the local coil, and a discharge circuit for discharging residual currents from the circuit, therefore allowing for rapid coupling and decoupling of the local coil.

Abstract: In this system and method for magnetic resonance imaging, an actively shielded primary coil includes a first and second set of turns each having a prescribed number of turns about an axis, and each being symmetrically positioned radially from the axis and equidistant with respect to a mid plane perpendicular to the axis. A secondary shielding coil includes a third and fourth set of turns each having a prescribed number of turns about the axis and being symmetrically positioned radially from the axis and equidistant with respect to the mid plane. The third set of turns is positioned in close proximity to the first set of turns and outward of the first set of turns. Likewise, the fourth set of turns is positioned in close proximity to the second set of turns and outward of the second set of turns. The first and third sets of turns are in a first prescribed turns ratio and the second and fourth sets of turns are in a second prescribed turns ratio.

Abstract: An MR imaging pulse sequence provides a method for simultaneous data acquisition from more than one independently prescribed volume while providing optimized field uniformity during both the magnetization preparation and data acquisition parts of the acquisition. The method is based on the use of a multi-element array coil where individual RF coil elements are more sensitive to one of the separate volumes of interest than to the other volumes. In the example of breast imaging, one scenario would have two coil elements that are designed to be most sensitive to the signal from the left breast, and two coil elements that are designed to be most sensitive to the signal from the right breast. An optimized pulse sequence and reconstruction technique is used to simultaneously acquire two separate sagittal imaging volumes corresponding to the left and right breasts with optimized fat suppression.

Abstract: A method and apparatus are disclosed for combining the respective readout signals for a loop and butterfly coil pair of a quadrature phased array used for magnetic resonance imaging. The technique used to combine the signals introduces a 180 degree phase shift, or multiple thereof, to the loop coil signal, thereby allowing the loop coil signal to be decoupled from other loop coil signals by a low input impedance preamplifier in series with the signal.

Abstract: A method of screening a subject for the presence of lipoprotein X includes the steps of: producing a measured lipid signal lineshape of an NMR spectrum of a blood plasma or serum sample obtained from a subject; generating a calculated lineshape for the sample, the calculated lineshape being based on derived concentrations of lipoprotein components potentially present in the sample, the derived concentration of each of the lipoprotein components being the function of a reference spectrum for that component and a calculated reference coefficient, wherein one of the lipoprotein components for which a concentration is calculated is lipoprotein X; and determining the degree of correlation between the calculated lineshape of the sample and the measured lineshape spectrum of the sample.

Abstract: A detunable coil assembly includes a main coil which resonates at a specified resonance frequency and a switchable detuning coil which, when switched on, becomes inductively coupled to the main coil and serves to detune it from its resonance frequency. The detuning coil and the main coil are electrically insulated from each other. The main coil may be of a multiply tuned kind and it may be detuned from more than one of its specified resonance frequencies at the same time by switching on the detuning coil.

Abstract: A method of NMR spectroscopy or tomography, wherein a sequence of temporarily offset radio frequency pulses is applied onto a spin ensemble, is characterized in that after a sequence of pulses with flip angles &agr;1 . . . &agr;n (with &agr;1 . . . &agr;n≧0°) and phases &phgr;1 . . . &phgr;n between which spins are dephased by &phgr;1 . . . &phgr;n, a central refocusing pulse is applied as (n+1)th pulse, followed by a pulse sequence which is mirror-symmetrical to the central refocusing pulse, wherein the flip angles &agr;n+2 . . . &agr;2n+1 and phases &phgr;n+2 . . . &phgr;2n+1 of the pulses have, in comparison with the mirror-symmetrical pulses with &agr;n . . . &agr;1 and &phgr;n . . . &phgr;1, negative sign with respect to amplitude and phase and the dephasings &phgr;n+2 . . . &phgr;2n+1 which are also mirror-symmetrical to the central refocusing pulse in the sequence are equal to the respective mirror-symmetrical dephasings &phgr;n . . .

Abstract: A magnetic resonance imaging apparatus creates images by exciting magnetic resonance in selected nuclei disposed within an image region. Through the image region a main magnetic field (B0) is applied and transverse gradients are produced. At selected times a high power RF pulse is applied to the imaging region causing the selected nuclei to resonate. These magnetic resonance signals are detected by a receive coil (D1, D2) and converted into an image representation viewable on a display (24). Images are obtained by repeating the transmit and receive portions until enough image data is received to produce an image. The receive coil (D1, D2) includes first decoupler circuits (28) arranged about the coil. During the transmit portion of the cycle, the decoupler circuits sense the high power RF pulse and decouple the coil. High speed switching diodes or PIN diodes are excited by the transmit RF pulse to switch inductors (40) into the coil to decouple the receive coil.

Abstract: A magnet assembly for a small scale NMR spectroscopy apparatus suitable for laboratory or home use, generally comprising two permanent magnets facing one another so that the facing surfaces have opposite polarities, a pole cap on each of the two facing surfaces of the permanent magnets, and a plurality of radially polarized canceling magnets disposed about the permanent magnets and pole caps. The design and position of the radially polarized canceling magnets about the tapered pole caps reduces leakage of the magnetic field, to maintain the magnetic field strength and homogeneity within the test region, without a disadvantageous increase in the size, weight and cost of the NMR apparatus. A curved edge ring shim may be used to increase magnetic field homogeneity in the test region. Also provided is a method for measurement of glucose concentration in a fluid using NMR spectroscopy.

Abstract: The invention relates to the use of diffusion spectrum magnetic resonance imaging (MRI) to map complex fiber architectures in tissues. The new methods can be used to resolve intravoxel heterogeneity of diffusion in vivo with MRI of diffusion density spectra.

Abstract: An asymmetric spin-echo (ASE) sequence having a variable asymmetry (&Dgr;TE) with respect to the RF pulse is used for imaging paramagnetic, diamagnetic or ferromagnetic instruments within tissues during interventional MRI procedures. The degree of asymmetry introduced determines an apparent size of the imaged instrument. In one embodiment of the invention, the amount of asymmetry is varied as a function of the phase encoding gradient steps. In this manner, the sequence is made sensitive to local gradients in the magnetic field but left insensitive to large scale variations such as those introduced by main magnetic field inhomogeneities.

Abstract: A fast, spectrally-selective steady-state free precession (SSFP) imaging method is presented. Combining k-space data from SSFP sequences with certain phase schedules of radiofrequency excitation pulses permits manipulation of the spectral selectivity of the image. For example, lipid and water can be rapidly resolved. The contrast of each image depends on both T1 and T2, and the relative contribution of the two relaxation mechanisms to image contrast can be controlled by adjusting the flip angle. Several applications of the technique are presented, including fast musculoskeletal imaging, brain imaging, and angiography. The technique is referred to herein as linear combination steady-state free precession (LCSSFP) and fluctuating equilibrium magnetic resonance (FEMR).

Abstract: This invention includes methods for analyzing data generated by various solid-state NMR experiments, including rotational echo double resonance (REDOR), transferred echo double resonance (TEDOR), dipolar recoupling at the magic angle (DRAMA), dipolar recoupling with a windowless sequence (DRAWS), and melding of spin-locking and DRAMA (MELODRAMA). The methods are based alternately on a new analytical transform or the maximum entropy method and their multi-dimensional extensions. They permit simultaneous, multiple distance measurements of high accuracy and precision, even from nuclei with identical chemical shifts. By providing high quality easily obtained distance measurement from disordered solid state materials, this invention also improves drug discovery and design through fast determination of structures of pharmaceutical lead compounds, drug molecules, or their targets.

Abstract: A system and method for improved water and fat separation in magnetic resonance imaging (MRI) is disclosed using a set of low-resolution images to correct phase errors with overall reduced scan time and post-processing time and enhanced reliability. Several embodiments are disclosed whereby reliable water and fat separation is achieved in nearly one NEX, Two NEX, or Three NEX regular imaging times. In the one embodiment, a regular image data set having water and fat phase-shifted by 90.degree. is acquired, along with two low-resolution image data sets where water and fat are phase-shifted by 0.degree. and 180.degree. are acquired. In another embodiment, two regular image data sets having water and fat phase-shifted by 0.degree. and 180.degree. are acquired, and a low-resolution imaging data set having water and fat phase-shifted by 90.degree. is acquired.

Abstract: In a method for identifying spikes in magnetic resonance signals obtained in magnetic resonance tomography, a magnetic resonance signal is obtained and is high-pass filtered. A statistical evaluation of the high-pass filtered magnetic resonance signal is then undertaken to determine whether the high-pass filtered magnetic resonance signal contains spikes which can be differentiated from a noise signal. If so, such spikes are identified, and can be removed from the raw data so that they do not contribute to image artifacts.

Abstract: A single-tuned rf-gradient saddle coil is used for an internal NMR lock in a high-field NMR probe. The non-dipolar lock coil geometry is chosen such that its filling factor and Q are maximized subject to the constraint that its coupling coefficient to two orthogonal saddle coils is zero. Various quadrupolar and octopolar rf coils are disclosed for use in NMR probes having three or four sample coils for multi-nuclear triple resonance or homonuclear decoupling.

Abstract: The gradient read time is varied during the course of a single pulse sequence in which both proton density weighted image data and T.sub.2 -weighted image data are collected. The number of gradient refocussings after each RF refocussing pulse in a gradient spin echo pulse sequence is changed during the course of the pulse sequence.

Abstract: A quadrature local coil includes two coil sets placed on opposite sides of the patient, each coil set having a single loop and a split loop so as to be sensitive to quadrature components of a flux field substantially centered between the coil sets. Signals are developed from the loops in a manner to reduce current flow in the loops preventing coupling of the opposing loops and the degradation of the signal. The signals may be summed to produce a single signal of improved signal-to-noise ratio.

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: An NMR system performs a 2DFT or 3DFT scan using a set of steady-state free precession (SSFP) pulse sequences. A contrast preparation pulse sequence precedes each series of SSFP pulse sequences and it includes a spectrally selective RF inversion pulse timed to water to provide T.sub.1 contrast between tissues having relatively long T.sub.1 times, followed by a spectrally selective RF inversion pulse tuned to suppress the signals from fat.

Abstract: The invention relates to a method and apparatus for applying dynamic nuclear polarization and magnetic imaging to studying an object. As the saturation of an electron spin system required by dynamic nuclear polarization is proceeding, the intensity of a polarizing magnetic field over the object is different from that of a polarizing magnetic field lying over the object during the detection of an NMR signal. The apparatus is provided with means for changing the intensity of a polarizing magnetic field in a manner such that the difference between magnetic field intensities is achieved.

Abstract: A pulse sequence for operating a magnetic resonance imaging apparatus for fast calculation of images of the fat and water distribution in an examination subject includes the steps of charging the examination subject with a first radio-frequency pulse which is selective with respect to a first spectral component and charging the examination subject with a second radio-frequency pulse which is selective with respect to a second spectral component. A dephasing gradient is activated between the two radio frequency pulses. The spin system is thus phase coded in two directions. A signal with respect to the second spectral component is read out under a first read-out gradient and a signal with respect to the first spectral component is read out under a second read-out gradient. Images of the fat and water distribution in the examination subject can thus be acquired with one measuring sequence.

Abstract: A method of simultaneous multinuclear magnetic resonance imaging and spatially localized NMR spectroscopy is disclosed. Clinical implementation of the disclosed method allows routine in vivo NMR spectroscopy studies without significantly increasing the time of conventional MR imaging studies. A unique sequence of rf excitation and magnetic gradient pulses is used which allows chemical shift imaging data to be acquired simultaneously with conventional imaging data. A deconvolution method extracts the chemical shift information for analysis and display.

Abstract: A phantom for diagnosis by nuclear magnetic resonance imaging comprises a container made of a synthetic resin and a hydrogel sealingly contained in the container. The container has at least one opening into which a sample material is inserted. The hydrogel is prepared by charging an aqueous solution of a polyvinyl alcohol into the container, cooling the aqueous solution to minus 10.degree.C. or lower to obtain a cooled frozen mass and thawing the cooled frozen mass. Also disclosed is a method for determining resolution power or discrimination capacity of an NMR imaging apparatus.

Abstract: For measurements with increased accuracy in a nuclear magnetic resonance apparatus, the detection device is equipped with one or more surface coils which act as measuring coils. To avoid mutual interference between a radio-frequency transmitting coil and the measuring coil, the measuring coil is provided with a decoupling circuit. The surface coil and the decoupling circuit form a part of a tuned circuit which is tuned to a significantly higher natural frequency during activation of the transmitting coil. On the other hand, the transmitting coil is shorted during detection with the surface coil by a low resistance shorting circuit, thereby avoiding interference with the radio-frequency transmission signals.

Abstract: An NMR method for acquiring the volume localized, in vivo proton spectra of spin-spin coupled metabolites employs a series of stimulated echo pulse sequences (90-TE/2-90-t.sub.1 -90-TE/2). The value of period t.sub.1 is different for each of the pulse sequences in the series, and the NMR signals produced by the series of pulse sequences are acquired and digitized to form a two-dimensional data array. A two-dimensional Fourier transformation is performed on this data array to produce an array of data that is employed to generate a contour plot.

Abstract: A method of heteronuclear decoupling in magnetic resonance spectroscopy and a device for determining a spectrum where spectra of a first type of nucleus which is spin-coupled to a second type of nucleus are decoupled inter alia in order to obtain a higher resolution. In inter alia phosphorous spectroscopy, during signal acquisition of resonance signals of the first type of nucleus, decoupling pulses are applied to the second type of nucleus, which decoupling pulses have been modulated in amplitude as well as in frequency or phase. The decoupling pulses need hardly be optimized. Very good decoupling is achieved, notably when use is made of surface coils for the transmitter and receiver coils exhibiting a substantial field inhomogeneity. When surface coils are used, suitable decoupling is achieved across a comparatively large volume.

Abstract: A magnetic resonance imaging system is adapted to achieve the imaging of magnetic resonance signals detected from an object by applying a high frequency magnetic field and gradient field to the object in a homogeneous static field in accordance with a predetermined pattern and includes a data pick-up section and image processing section. The data pick-up section is of such a type that, with the use of a predetermined pulse sequence so time-adjusted that a phase difference between two predetermined substances somewhat differing in their magnetic resonance frequency due to a chemical shift is .pi./2 or -.pi./2 on a predetermined time, picks up all magnetic resonance data necessary for reconstruction of an image of a slice excited by the high frequency field into a magnetic resonance within a period of time in which that predetermined nuclear magnetization of the slice is relaxed due to the relaxation of a transverse magnetization.

Abstract: The magnetic resonance (MR) imaging system, in which magnetic resonance is caused on the spin of a specific nucleus using a gradient field and a excitation pulse, and, through observation of an MR signal, an image representing the density distribution of that nucleus in a target region of a body is attained, provides at least one of a density distribution image of protons in water of the body and that of protons in the body's fat. First image data comprising complex image data representing the distribution of the spin in a water phantom and second image data comprising complex image data representing the spin distribution in the body are obtained. The first and second image data are acquired in the excitation sequence in which the phase of the MR signal for the water protons is opposite to that of the fat protons. By comparing the first and second image data, it is discriminated which one of the densities of water and fat protons in the second image data is dominant.

Abstract: An NMR method for acquiring the in vivo proton spectra of spin-spin coupled metabolites employs a pair of stimulated echo pulse sequences (90-TE/2-90-t.sub.1 -90-TE/2). The period TE/2 is set to optimize the signal components produced by the coupled spins of the metabolites. The value of period t.sub.1 is different for the two pulse sequences and the difference between the two resulting NMR echo signals provides the desired spectra.

Abstract: To eliminate homonuclear couplings along the .omega..sub.1 axis in 2D spectroscopy, a time reversal pulse (5, 6) is inserted into the pulse sequence that is generally employed for experiments of this type, which time reversal pulse divides the evolution period t.sub.1 that is required for experiments of this type into two equal portions. The time reversal pulse is intended to cause the spin moments to rotate about an angle .beta..sub.n and is preferably composed of two 90.degree. pulses, the first of which has a phase of .beta..sub.n +.phi..sub.q and the second a phase of .pi.+.phi..sub.q. The phase of the RF oscillation of the pulse that precedes the time reversal must be shifted by an angle of .beta..sub.n.

Abstract: A method of mapping the local distribution of the coupling constant J and for the application of this method, as for example, for examining the dynamic properties of an object. The object is excited with a first (90.degree.) excitation pulse. A magnetic field gradient is applied to the object and after a first time delay, the object is subjected to a second (180.degree.) excitation pulse. A magnetic field gradient is reapplied and after a second time delay, the spin echo signal is obtained. The sequence is repeated by changing the first and second delay times and changing the time integrals of the magnetic field gradients in accordance with the selected NMR imaging method. The second excitation pulse is preferably maintained at the midway point of the time between the first excitation pulse and the spin echo. The method may be used to analyze metabolic or physiological properties by using tracers with nuclei having coupling constants differing from the nuclei normally present in the object.

Abstract: A two-dimensional nuclear magnetic resonance spectrometry which comprises the following steps to facilitate phase correction:(a) taking the Fourier transform of the set S(t.sub.1, t.sub.2) of the free induction decay signals with respect to t.sub.2 to generate the transformed data sets of S.sub.c (t.sub.1, F.sub.1) or S.sub.s (t.sub.1, F.sub.2), the signals being stored in the memory corresponding to the values of t.sub.1 ;(b) obtaining data S.sub.c (t.sub.1000, F.sub.2) and S.sub.s (t.sub.1000, F.sub.2) whose phases have been shifted by phase angle .theta..sub.2, from the initial data S.sub.c (t.sub.1000, F.sub.2) and S.sub.s (t.sub.1000, F.sub.2) contained in two Fourier components S.sub.c (t.sub.1, F.sub.2) and S.sub.s (t.sub.1, F.sub.2) derived by the Fourier transformation made in the step (a), in such a way that the peak contained in the initial data S.sub.c (t.sub.1000, F.sub.2) and S.sub.s (t.sub.1000, F.sub.

Abstract: The invention relates to a method and system for determining an image of a nuclear magnetization distribution in a body. In known methods, particularly in nuclear spin echo techniques, a resonance signal is generated which has high dynamics. In the method according to the invention dephasing is effected which is non-linear place-dependent or which is frequency-dependent within a spectroscopy distribution, as a result of which the generated resonance signal will have a much smaller amplitude. Since the non-linear dephasing applied within the distribution is known, a correction can be made for this after the determination of the measuring signals.

Abstract: During a transmit cycle portion, a radio frequency transmitter (C) continuously generates an AC biasing signal and selectively generates a radio frequency signal. The AC biasing signal gates a first switch (10) and a second switch (32) such that the radio frequency signals from the transmitter are conducted to a magnetic resonance probe (E) but are blocked from being conducted to a receiver (F). A first filter (20) prevents the bias signals from being applied to the probe. The second switch includes a pair of crossed diodes (34, 36) which are gated conductive by the AC bias signal. A filter (72) passes the radio frequency signals but not the bias signals to ground to prevent the radio frequency signals from reaching the receiver. A filter (80) allows the bias signals to be applied across a load (88) such that the transmitter sees the load at the bias signal frequency. Another filter (40) prevents the bias signal from reaching the transmitter.

Abstract: A quadrature detection magnetic resonance imaging (MRI) RF coil is constructed from non-overlapping axially-extending conductors arrayed about the circumference of a cylinder in four circumferentially spaced-apart groupings. Axially-extending annular gaps in the fingers (e.g, at their mid-points) are bridged across by RF coupling capacitors. The outer ends of the fingers are also coupled by annular conductors having one or more conductive gaps bridged by coupling capacitance. First and second quadrature detection RF input/output ports are coupled to at least one respective finger element in each of two adjacent groups of elements.

Abstract: An automatic Q-spoiler comprising at least one Josephson tunnel junction connected in an LC circuit for flow of resonant current therethrough. When in use in a system for detecting the magnetic resonance of a gyromagnetic particle system, a high energy pulse of high frequency energy irradiating the particle system will cause the critical current through the Josephson tunnel junctions to be exceeded, causing the tunnel junctions to act as resistors and thereby damp the ringing of the high-Q detection circuit after the pulse. When the current has damped to below the critical current, the Josephson tunnel junctions revert to their zero-resistance state, restoring the Q of the detection circuit and enabling the low energy magnetic resonance signals to be detected.

Abstract: A nuclear magnetic resonance imaging method having the first step of exciting a nuclear spin in a volume of an object in a static magnetic field, the second step of applying first, second and third gradients, and the third step of producing a spin echo signal under the second gradient in accordance with the nuclear spin which has the step of applying a high frequency pulse in which the nuclear spin is approximately tilted at 116.degree. as an exciting pulse in the first step.

Abstract: An NMR spectroscopy method monitors a component of a sample, the component having two resonances in coupled together different spectral regions. The first resonance lies in a region including a resonance of a second component of a sample while the second resonance lies in a spectral region including a resonance of a third component of the sample. Two spin-echo pulse sequences each consisting of pulses of a predetermined frequency are applied, the spin-echo resonance spectra together being used to obtain the second resonance of the first component with the resonance of the third component suppressed.

Abstract: A local coil for use in NMR imaging includes a pair of loop-gap resonators which are geometrically arranged to be intrinsically isolated. The local coil also includes passive decoupling means to completely decouple the local coil during excitation. In a first embodiment, the pair of loop-gap resonators are disposed axially and the passive decoupling means comprises a pair of back-to-back diodes across the loop-gap resonators. In a second embodiment, the pair of loop-gap resonators are disposed in a plane and the passive decoupling means comprises two single turn loops inside each loop-gap resonator with back-to-back diodes across an open segment of each single turn loop. During excitation, the diodes fire thereby lowering the Q and shifting the resonant frequency of the local coil. Using a combination of intrinsic isolation and passive decoupling, the local coil is completely decoupled from the excitation field.

Abstract: A method for suppressing undesired NMR response signals from uncoupled resonances while obtaining desired NMR signals from a sample containing like nuclei which are coupled to one another, precedes each NMR response-signal-evoking excitation signal sequence with a pulse sequence having radio-frequency (RF) pulses providing a 90.degree. rotation of the spin magnetization about a first axis and then providing a 180.degree. degree rotation of the spin magnetization about a second axis, substantially orthogonal to the first axis, in the plane of magnetization rotation, prior to the alternating presence of a second 90.degree. RF pulse causing rotation about the first axis prior to the start of an associated imaging sequence. Time intervals T, of substantially alike duration related to the coupling constant J of the coupled nuclei, occur between each of the pulses; that one of the alternating sequences which is devoid of the second 90.degree.

Abstract: To produce image information from an object it is subjected to a continuous static magnetic field along a Z axis and to sets of sequences of orthogonal gradients G.sub.x, G.sub.y and G.sub.z to the magnetic field. Spins in a selected plane (the X-Z plane) are excited by selective rf pulses and an associated G.sub.y gradient and the selected spins are subjected to all three gradients of which the G.sub.z gradient provides twist or warp to each column of spins extending along the Z axis to phase-encode the columns. The spin-echo signals are read out in the presence of a G.sub.x gradient. In each set of sequences a different value of Z gradient is employed. The Fourier transformed spin-echo signals obtained from each sequence, when arranged in order of increasing G.sub.z gradient and subjected to a second Fourier transform represent the distribution of spin density in the Z direction, thus giving a two-dimensional image of the selected X-Z plane.

Abstract: In an MRI system, a passive conductive RF decoupling structure is disposed about a portion of the volume to be imaged but at a location which is proximate a sub-volume from which MRI RF responses are to suppressed. The passive decoupling structure may be a sheet of conductive material or a shorted loop of conductive material (preferably having a gap in conductivity bridged by RF bypass capacitance so as to suppress lower frequency eddy currents otherwise caused by changing magnetic gradient fields in the MRI system).