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4820987 Magnetic resonance imaging apparatus comprising an activatable birdcage RF coil
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IV
frequency pulse, mutually orthogonal phaseencoding and readout gradients are alternately applied in the image plane to effect a traversal through spatial frequency domain (k-space). In a preferred embodiment of the invention, the readout gradient is applied as a continuous sinusoidal wave, resulting in a slight overlap between the phase-encoding and readout gradients. If phase errors vary slowly in time, only a partial k-space trajectory is required. Chemical shift is eliminated either by the application of a suppression pulse of RF field or by tailoring the frequency spectrum of the rephasing pulse so as to preclude rephasing of one or other of the chemical moieties.
4818943 PHANTOM FOR IMAGING SYSTEMS Ramesh Chandra assigned to New York University A phantom for evaluating and calibrating a nuclear magnetic resonance imaging system. The phantom includes a cylindrical housing having a central axis and defining a hollow region therein. The phantom also includes a first conical wall member and a second conical wall member which are congruous to each other and secured to one another at their respective bases. The conical wall members are disposed within and separate the hollow region into a first region outside of the conical wall members and a second region within the conical wall members. The first region is filled with a first predetermined fluid and the second region is filled with a second predetermined fluid. Preferably each conical wall member is symmetrical about central axis and has its apex disposed along the central axis.
4820983 METHOD AND APPARATUS FOR PERFORMING AN NMR EXPERIMENT Max R Bendall, David Queensland, Australia
T Pegg, Burbank,
In a method for NMR excitation of a sample, an Rf pulse is applied to an irradiation coil (6) proximate the sample, in the presence of an external DC magnetic field and an adiabatic passage is performed wherein the Rf pulse is controlled such that: See Patentfor Tabular Presentation PS
See Patent for Tabular Presentation PS See Patent for Tabular Presentation PS where s = S/A, where S is the frequency offset of a nucleus from the center of the spectrum, and where v allows for variation of Bl throughout the sample, DeltaH is the resonance offset of the nuclear spins, and Bl is the rf field of a spin-lock pulse.
4820985 APPARATUS FOR TUNING AN NMR FIELD COIL Matthew G Eash assigned to General Electric Company A coil assembly for radio frequency NMR imaging is designed to resonate at a desired frequency. The assembly includes a cylindrical field coil having a pair of conductive end loops disposed in a spaced-apart relation along a central axis. A plurality of conductive segments electrically interconnect the conductive end loops at periodic points around their periphery. These conductive segments include reactive elements which cause the field coil to resonate at a given frequency. A magnetic shield is disposed about the field coil. A plurality of reactive shunts are coupled between different locations about the periphery of the field coil and a common electrical node, such as the shield. Each of the reactive shunts is variable to increase or decrease the resonant frequency of the field coil, thereby tuning it to the desired frequency.
4820987 MAGNETIC RESONANCE IMAGING APPARATUS COMPRISING AN ACTIVATABLE BIRDCAGE RF COIL Wilhelmus R M Mens, Eindhoven, Netherlands assigned to U S Philips Corporation A so-called birdcage coil must be quickly deactivated after having generated an RF magnetic field, so as not to disturb the detection of the generated spin resonance signals by the surface coil (or another coil). To this end, semiconductor switches are included in some of the rod conductors of the birdcage coil. The switches are arranged substantially halfway along the rod conductors, because the RF voltage exhibits a zero crossing at that area. As a result, the semiconductor switches can operate with a low voltage. It has been found that the interruption of
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the rod conductors which are situated in one symmetry half of the birdcage coil and which carry most current in that half suffices for substantial deactivation.
4820988 MAGNETIC GRADIENT COIL SET FOR NUCLEAR MAGNETIC RESONACE SYSTEM HAVING SUBSTANTIALLY DIFFERENT COIL-PATIENT SPACINGS Lawrence E Crooks, Joseph W Carlson assigned to The Regents of the University of California In a gradient coil set for a magnetic resonance system, the y gradient coils are located substantially closer to the patient than are the x and z gradient coils. As a result, one may design the y gradient coils to produce a stronger y gradient, to have reduced inductance or otherwise better tailor the magnetic/electrical properties of the gradient coil set for MRI imaging sequences. In the exemplary embodiment, at least portions of the y gradient coils have a first spacing from the z-axis while the x and z gradient coils have a second substantially larger spacing from the zaxis. Furthermore, while the x and z gradient coils are centered about the z-axis in the patient access space, alternate sides of the y gradient coil set are centered about respectively off-set centers vertically displaced from the z-axis center of the patient access area. The result is a substantially rectangular or elliptical patient access opening with horizontal dimensions defined by the x, z coils sets and vertical dimensions defined by the y coil set.
4821213 SYSTEM FOR THE SIMULTANEOUS DISPLAY OF TWO OR MORE INTERNAL SURFACES WITHIN A SOLID OBJECT Harvey E Cline, Siegwalt Ludke, William E Lorensen assigned to General Electric Co A dual pipeline architecture for a system for preprocessing image data gathered from such systems as magnetic resonance imaging and computer axial tomography scanners. In one simultaneously operable dual pipeline, normal vectors are computed for each voxel element in
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accordance with the dividing cubes vector generation system. In another pipeline, circuitry is provided for generating surface identification indicia which are associated with unit normal vectors produced by the former pipeline. Data are supplied to a graphics processor for the production of shaded two-dimensional images representative of three-dimensional surfaces from various view angles. The system is particularly useful in medical diagnostic applications and is particularly useful in planning surgical procedures.
4822594 CONTRAST ENHANCING AGENTS FOR MAGNETIC RESONANCE IMAGES Wendell A Gibby A saccharide matrix containing chelating agents. In a preferred embodiment the chelating agents, for example, EDTA or DTPA, bind metals having at least one unpaired electron. Such compositions are useful for enhancing the contrast of Magnetic Resonance images.
4825159 METHOD FOR OPERATING A NUCLEAR MAGNETIC RESONANCE TOMOGRAPHY APPARATUS Arnulf Oppelt, Hubertus Fischer, Helmut Barfuss, Spardorf, Federal Republic Of Germany assigned to Siemens Aktiengesellschaft An examination subject is irradiated with a sequence of RF pulses. Negative gradient pulses Gz3 and Gy4, as well as a phase-coding gradient Gx2 are generated preceding each RF pulse. Negative gradient pulses Gz2 and Gyl, as well as a phase-coding gradient Gx 1, are generated following each RF pulse. The phase-coding gradient Gxl is inverted relative to the phase-coding gradient Gx2. The negative gradient pulse Gyl is followed by a positive gradient pulse Gy2 which serves as a read-out gradient during which a first signal Sl is received. A positive gradient pulse Gy3 is generated preceding the negative gradient pulse Gy4, the positive gradient pulse Gy3 serving as a read-out gradient during which a second signal S2 is received. Two signals having different T2 weighting are thus obtained in each
IV
frequency pulse, mutually orthogonal phaseencoding and readout gradients are alternately applied in the image plane to effect a traversal through spatial frequency domain (k-space). In a preferred embodiment of the invention, the readout gradient is applied as a continuous sinusoidal wave, resulting in a slight overlap between the phase-encoding and readout gradients. If phase errors vary slowly in time, only a partial k-space trajectory is required. Chemical shift is eliminated either by the application of a suppression pulse of RF field or by tailoring the frequency spectrum of the rephasing pulse so as to preclude rephasing of one or other of the chemical moieties.
4818943 PHANTOM FOR IMAGING SYSTEMS Ramesh Chandra assigned to New York University A phantom for evaluating and calibrating a nuclear magnetic resonance imaging system. The phantom includes a cylindrical housing having a central axis and defining a hollow region therein. The phantom also includes a first conical wall member and a second conical wall member which are congruous to each other and secured to one another at their respective bases. The conical wall members are disposed within and separate the hollow region into a first region outside of the conical wall members and a second region within the conical wall members. The first region is filled with a first predetermined fluid and the second region is filled with a second predetermined fluid. Preferably each conical wall member is symmetrical about central axis and has its apex disposed along the central axis.
4820983 METHOD AND APPARATUS FOR PERFORMING AN NMR EXPERIMENT Max R Bendall, David Queensland, Australia
T Pegg, Burbank,
In a method for NMR excitation of a sample, an Rf pulse is applied to an irradiation coil (6) proximate the sample, in the presence of an external DC magnetic field and an adiabatic passage is performed wherein the Rf pulse is controlled such that: See Patentfor Tabular Presentation PS
See Patent for Tabular Presentation PS See Patent for Tabular Presentation PS where s = S/A, where S is the frequency offset of a nucleus from the center of the spectrum, and where v allows for variation of Bl throughout the sample, DeltaH is the resonance offset of the nuclear spins, and Bl is the rf field of a spin-lock pulse.
4820985 APPARATUS FOR TUNING AN NMR FIELD COIL Matthew G Eash assigned to General Electric Company A coil assembly for radio frequency NMR imaging is designed to resonate at a desired frequency. The assembly includes a cylindrical field coil having a pair of conductive end loops disposed in a spaced-apart relation along a central axis. A plurality of conductive segments electrically interconnect the conductive end loops at periodic points around their periphery. These conductive segments include reactive elements which cause the field coil to resonate at a given frequency. A magnetic shield is disposed about the field coil. A plurality of reactive shunts are coupled between different locations about the periphery of the field coil and a common electrical node, such as the shield. Each of the reactive shunts is variable to increase or decrease the resonant frequency of the field coil, thereby tuning it to the desired frequency.
4820987 MAGNETIC RESONANCE IMAGING APPARATUS COMPRISING AN ACTIVATABLE BIRDCAGE RF COIL Wilhelmus R M Mens, Eindhoven, Netherlands assigned to U S Philips Corporation A so-called birdcage coil must be quickly deactivated after having generated an RF magnetic field, so as not to disturb the detection of the generated spin resonance signals by the surface coil (or another coil). To this end, semiconductor switches are included in some of the rod conductors of the birdcage coil. The switches are arranged substantially halfway along the rod conductors, because the RF voltage exhibits a zero crossing at that area. As a result, the semiconductor switches can operate with a low voltage. It has been found that the interruption of
New Patents
the rod conductors which are situated in one symmetry half of the birdcage coil and which carry most current in that half suffices for substantial deactivation.
4820988 MAGNETIC GRADIENT COIL SET FOR NUCLEAR MAGNETIC RESONACE SYSTEM HAVING SUBSTANTIALLY DIFFERENT COIL-PATIENT SPACINGS Lawrence E Crooks, Joseph W Carlson assigned to The Regents of the University of California In a gradient coil set for a magnetic resonance system, the y gradient coils are located substantially closer to the patient than are the x and z gradient coils. As a result, one may design the y gradient coils to produce a stronger y gradient, to have reduced inductance or otherwise better tailor the magnetic/electrical properties of the gradient coil set for MRI imaging sequences. In the exemplary embodiment, at least portions of the y gradient coils have a first spacing from the z-axis while the x and z gradient coils have a second substantially larger spacing from the zaxis. Furthermore, while the x and z gradient coils are centered about the z-axis in the patient access space, alternate sides of the y gradient coil set are centered about respectively off-set centers vertically displaced from the z-axis center of the patient access area. The result is a substantially rectangular or elliptical patient access opening with horizontal dimensions defined by the x, z coils sets and vertical dimensions defined by the y coil set.
4821213 SYSTEM FOR THE SIMULTANEOUS DISPLAY OF TWO OR MORE INTERNAL SURFACES WITHIN A SOLID OBJECT Harvey E Cline, Siegwalt Ludke, William E Lorensen assigned to General Electric Co A dual pipeline architecture for a system for preprocessing image data gathered from such systems as magnetic resonance imaging and computer axial tomography scanners. In one simultaneously operable dual pipeline, normal vectors are computed for each voxel element in
V
accordance with the dividing cubes vector generation system. In another pipeline, circuitry is provided for generating surface identification indicia which are associated with unit normal vectors produced by the former pipeline. Data are supplied to a graphics processor for the production of shaded two-dimensional images representative of three-dimensional surfaces from various view angles. The system is particularly useful in medical diagnostic applications and is particularly useful in planning surgical procedures.
4822594 CONTRAST ENHANCING AGENTS FOR MAGNETIC RESONANCE IMAGES Wendell A Gibby A saccharide matrix containing chelating agents. In a preferred embodiment the chelating agents, for example, EDTA or DTPA, bind metals having at least one unpaired electron. Such compositions are useful for enhancing the contrast of Magnetic Resonance images.
4825159 METHOD FOR OPERATING A NUCLEAR MAGNETIC RESONANCE TOMOGRAPHY APPARATUS Arnulf Oppelt, Hubertus Fischer, Helmut Barfuss, Spardorf, Federal Republic Of Germany assigned to Siemens Aktiengesellschaft An examination subject is irradiated with a sequence of RF pulses. Negative gradient pulses Gz3 and Gy4, as well as a phase-coding gradient Gx2 are generated preceding each RF pulse. Negative gradient pulses Gz2 and Gyl, as well as a phase-coding gradient Gx 1, are generated following each RF pulse. The phase-coding gradient Gxl is inverted relative to the phase-coding gradient Gx2. The negative gradient pulse Gyl is followed by a positive gradient pulse Gy2 which serves as a read-out gradient during which a first signal Sl is received. A positive gradient pulse Gy3 is generated preceding the negative gradient pulse Gy4, the positive gradient pulse Gy3 serving as a read-out gradient during which a second signal S2 is received. Two signals having different T2 weighting are thus obtained in each