Search Patents
  • Multiple measurement noise reducing system using space-variant filters
    Patent number: 4503461
    Abstract: Extraneous signals or artifacts are reduced in a multiple measurement noise reducing system such as an X-ray imaging system by processing a plurality of measurements to obtain a first image signal of an object representing a desired parameter such as a blood vessel, processing the plurality of measurements to provide a second image signal having increased signal-to-noise, low pass filtering the first image signal, high pass filtering the second image signal, and then combining the two filtered signals. The filter frequencies are varied in response to the presence of artifacts to minimize effects of the artifact on the combined signal.
    Type: Grant
    Filed: February 22, 1983
    Date of Patent: March 5, 1985
    Assignee: The Board of Trustees of the Leland, Stanford Junior University
    Inventor: Dwight G. Nishimura
  • Inversion recovery MRI
    Patent number: 5588431
    Abstract: Multiple inversion recovery flow imaging employs at least four spin inversion pulses following saturation of static nuclei spins to null nuclei in static material having different spin-lattice relaxation times (T.sub.1) with the inversion pulses being spaced in time to substantially reduce the longitudinal magnetization of the T.sub.1 species present. The saturation of static nuclei spins includes applying a sequence of saturation pulses with adjacent pulses being separated by a diphasing gradient to avoid refocusing coherence. The detection of signals includes applying at least one RF read-out pulse near the nulling point.
    Type: Grant
    Filed: August 17, 1995
    Date of Patent: December 31, 1996
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Sanjay Mani, Dwight G. Nishimura, Steven M. Conolly, John M. Pauly
  • Magnetic resonance imaging using driven equilibrium fourier transform
    Patent number: 6219571
    Abstract: A new technique for imaging a material with a high T2/T1 ratio such as articular cartilage uses driven equilibrium Fourier transform (DEFT), a method of enhancing signal strength without waiting for full T1 recovery. Compared to other methods, DEFT imaging provides a good combination of bright cartilage and high contrast between cartilage and surrounding tissue. Both theoretical predictions and images show that DEFT is a valuable method for imaging articular cartilage when compared to spoiled gradient recalled acquisition in the steady-state (SPGR) or fast spin echo (FSE). T2-decay, T1 recovery, echo time, magnetization density, proton density, and equilibrium density per proton are related by a derived equation.
    Type: Grant
    Filed: March 29, 1999
    Date of Patent: April 17, 2001
    Assignee: Board of Trustees of the Leland Stanford Junior University
    Inventors: Brian A. Hargreaves, Dwight G. Nishimura
  • System and method of parallel imaging with calibration to a separate coil
    Patent number: 7492153
    Abstract: An RF coil assembly includes a plurality of RF source coils and an RF target coil separate from the plurality of RF source coils. A computer is programmed to acquire MR data of an imaging object from each of the plurality of RF source coils and to acquire MR data of the imaging object from the RF target coil. The computer is further programmed to calculate a set of weights based on a relationship between MR data acquired from each RF source coil and MR data acquired from the RF target coil and to reconstruct an image based on an application of the set of weights to at least a portion of the MR data acquired from each of the plurality of RF source coils.
    Type: Grant
    Filed: June 4, 2007
    Date of Patent: February 17, 2009
    Assignees: General Electric Company, Board of Trustees of the Leland Stanford, Jr. University
    Inventors: Anja C. S. Brau, Philip James Beatty, Dwight G. Nishimura
  • Linear combination steady-state free precession MRI
    Patent number: 6307368
    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).
    Type: Grant
    Filed: May 14, 1999
    Date of Patent: October 23, 2001
    Assignee: Board of Trustees of the Leland Stanford Junior University
    Inventors: Shreyas S. Vasanawala, John M. Pauly, Dwight G. Nishimura
  • Multiple measurement noise reducing system using artifact edge identification and selective signal processing
    Patent number: 4499493
    Abstract: Disclosed is a multiple measurement multiple energy X-ray imaging system in which a plurality of measurements are processed to provide a first image signal representing a desired parameter of an object and in which the plurality of measurements are processed to provide a second processed image signal having greater signal-to-noise ratio than the first processed image signal but in which extraneous artifacts may be introduced into the signal. The spatial location of edges of the extraneous artifacts are determined. The first processed image signal and the second processed image signal are combined to provide an improved image signal except at the spatial locations of the extraneous artifacts where the first processed image signal is used for the image signal thereby eliminating the extraneous artifact from the displayed image.
    Type: Grant
    Filed: February 22, 1983
    Date of Patent: February 12, 1985
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventor: Dwight G. Nishimura
  • Variable density fourier velocity encoding MR imaging
    Patent number: 6650115
    Abstract: Real time spatially localized velocity distribution is measured using magnetic resonance techniques by first exciting a column-shaped region using a 2D RF excitation pulse. A cyclical readout gradient is then played along the excited column's axis while the magnetic resonance signal is continuously sampled to create a 2D sample set of velocity frequency vs. spatial frequencies in the same direction. If the cyclical readout gradient, for example a sawtooth-shaped gradient, has lobes of increasing area, the spacing between samples in the velocity-frequency direction is increased to emphasize sampling at low velocity-frequency and to more coarsely sample high velocity-frequencies. The sequence can be repeated to collect a time series of velocity-position images, which can then be sampled to create a velocity-time image at a single location.
    Type: Grant
    Filed: October 12, 2001
    Date of Patent: November 18, 2003
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Julie Camille DiCarlo, Dwight G. Nishimura
  • MRI method and apparatus for selective image suppression of material based on T1 and T2 relation times
    Patent number: 5655531
    Abstract: The selective imaging of an object having two materials with different relaxation times (T1 or T2) is provided by using a driven equilibrium sequence (T2 weighted preparation sequence) followed by an inversion recovery sequence. In the driven equilibrium sequence the object is placed in a static magnetic field along a longitudinal axis, an excitation pulse is applied to tip nuclei spins into a transverse plane, and at least one refocusing pulse is applied to produce a spin echo having a magnetization component as a function of relaxation time. At least one pulse is then applied to the object to drive the spin echo to an inverted position along the longitudinal axis. A readout excitation is then applied at a later time when the longitudinal magnetization of one material is substantially reduced. In one embodiment, an inversion pulse is applied prior to the T2 weighted preparation sequence.
    Type: Grant
    Filed: May 15, 1995
    Date of Patent: August 12, 1997
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Dwight G. Nishimura, Jean H. Brittain
  • Catalyzing the transient response in steady-state MRI sequences
    Patent number: 6452387
    Abstract: A steady-state condition for tipped nuclear spins is accelerated or catalyzed by first determining magnetization magnitude of the steady state and the scaling magnetization along one axis (Mz) to at least approximate the determined magnetization magnitude. Then the scaled magnetization is rotated to coincide with a real-valued eigenvector extension of the tipped steady-state magnetization. Any error vector will then decay to the steady-state condition without oscillation. In one embodiment, the magnetic resonance imaging utilizes steady-state free precession (SSFP). The scaling and rotating steps are followed by the steps of applying read-out magnetic gradients and detecting magnetic resonance signals from the tipped nuclear spins. The magnetization magnitude is determined by eigenvector analysis, and the eigenvector extension is a real-valued eigenvector determined in the analysis.
    Type: Grant
    Filed: March 7, 2001
    Date of Patent: September 17, 2002
    Assignee: Board of Trustees of the Leland Stanford Junior University
    Inventors: Brain A. Hargreaves, Shreyas Vasanawala, John M. Pauly, Dwight G. Nishimura
  • Multiple repetition time steady-state free precession imaging
    Patent number: 7560925
    Abstract: A method of providing selective spectral suppression in balanced SSFP magnetic resonance imaging for a first and second species is provided. A plurality of balanced SSFP images are acquired. Each acquisition includes applying RF excitations in a sequence of TR intervals with each being applied in an associated TR interval. The sequence of TR intervals includes at least one data acquisition TR interval and at least two secondary TR intervals each having a duration that is shorter than the data acquisition TR interval. A first secondary TR interval precedes the data acquisition TR interval and a second secondary TR interval follows the data acquisition TR interval. The duration of the second secondary TR interval is substantially equal to the first secondary TR interval such that the sequence of TR intervals is substantially symmetric with respect to duration about a center point of the sequence of TR intervals.
    Type: Grant
    Filed: May 1, 2008
    Date of Patent: July 14, 2009
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Dwight G. Nishimura, Tolga Cukur
  • MRI RF Pulse Sequence for Multidimensional Outer Volume Suppression
    Publication number: 20180292489
    Abstract: A magnetic resonance imaging (MRI) techniques uses a T2-preparation outer volume suppression (OVS) pulse sequence to reduce the longitudinal magnetization outside a region of interest. A region is excited that includes the region of interest, radiofrequency (RF) signals are detected, and MRI images generated from the RF detected signals. The T2-preparation OVS pulse sequence includes, sequentially: a first tip-down excitation pulse, a first refocusing excitation pulse, a first tip-up excitation pulse that is selective spatially and/or spectrally, a second tip-down excitation pulse that is 180° out of phase with respect to the first tip-down excitation pulse, a second refocusing excitation pulse, and a second tip-up excitation pulse that is selective spatially and/or spectrally.
    Type: Application
    Filed: April 7, 2017
    Publication date: October 11, 2018
    Inventors: David Y. Zeng, Dwight G. Nishimura
  • Diminishing variance process for real-time reduction of motion artifacts in MRI
    Patent number: 5427101
    Abstract: A method whereby motion can be detected in real time during the acquisition of MRI data. This enables the implementation of several algorithms to reduce or eliminate this motion from an image as it is being acquired. The method is an extension of the acceptance/rejection method algorithm called the diminishing variance algorithm (DVA). With this method, a complete set of preliminary data is acquired along with information about the relative motion position of each frame of data. After all the preliminary data is acquired, the position information is used to determine which lines are most corrupted by motion. Frames of data are then reacquired, starting with the most corrupted frame. The position information is continually updated in an iterative process, therefore each subsequent reacquisition is always done on the worst frame of data. The algorithm has been implemented on several different types of sequences, and preliminary in vivo studies indicate that motion artifacts are dramatically reduced.
    Type: Grant
    Filed: August 4, 1994
    Date of Patent: June 27, 1995
    Assignee: Board of Trustees of the Leland Stanford Junior University
    Inventors: Todd S. Sachs, Craig H. Meyer, Dwight G. Nishimura
  • NMR imaging of blood flow by moment variation of magnetic gradients
    Patent number: 4718424
    Abstract: Selective material projection imaging in which static and flowing material are distinguishable utilizes magnetic gradients whose waveforms have selective moments. The effects of the magnetic field gradients are utilized in obtaining data for a plurality of images whereby the subtraction of image data will result in selected material imaging. The zero moment of a magnetic gradient waveform affects the phase of static material and the phase of moving material, while the first moment of a magnetic gradient waveform affects the phase of constant velocity moving material but not the phase of static material. The second moment of a magnetic gradient waveform affects the phase of varying velocity moving material but not the phase of static material or constant velocity material. The nuclear spins of a region of a body can be excited under different conditions of an applied magnetic field gradient so that data under the different conditions can be subtracted to eliminate selected material.
    Type: Grant
    Filed: August 7, 1986
    Date of Patent: January 12, 1988
    Assignee: Stanford University
    Inventor: Dwight G. Nishimura
  • MRI RF pulse sequence for multidimensional outer volume suppression
    Patent number: 10690739
    Abstract: A magnetic resonance imaging (MRI) techniques uses a T2-preparation outer volume suppression (OVS) pulse sequence to reduce the longitudinal magnetization outside a region of interest. A region is excited that includes the region of interest, radiofrequency (RF) signals are detected, and MRI images generated from the RF detected signals. The T2-preparation OVS pulse sequence includes, sequentially: a first tip-down excitation pulse, a first refocusing excitation pulse, a first tip-up excitation pulse that is selective spatially and/or spectrally, a second tip-down excitation pulse that is 180° out of phase with respect to the first tip-down excitation pulse, a second refocusing excitation pulse, and a second tip-up excitation pulse that is selective spatially and/or spectrally.
    Type: Grant
    Filed: April 7, 2017
    Date of Patent: June 23, 2020
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: David Y Zeng, Dwight G Nishimura
  • Magnetic resonance imaging of short T.sub.2 species with improved contrast
    Patent number: 5150053
    Abstract: Magnetic resonance signals for imaging species having short spin-spin relaxation times (T.sub.2) are obtained without the need for a refocusing lobe. A series of RF excitation pulses are applied to the species with magnetic resonance signals being detected after each RF excitation pulse is applied. The magnetic resonance signals are then combined to provide the imaging signals. In one embodiment, each RF excitation pulse is half of a conventional slice-selective pulse with each pulse being slewed to zero. Contrast between the imaged short T.sub.2 species and longer T.sub.2 species can be enhanced by first applying an RF signal having sufficient amplitude to excite the longer T.sub.2 species but insufficient amplitude to excite the short T.sub.2 species whereby the longer T.sub.2 species are tipped by the RF signal. A magnetic gradient can then be applied to dephase the tipped nuclei of the longer T.sub.2 species. The imaging signals are then obtained from magnetic resonance signals from the short T.sub.
    Type: Grant
    Filed: January 25, 1991
    Date of Patent: September 22, 1992
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: John M. Pauly, Steven M. Conolly, Dwight G. Nishimura
  • NMR imaging of moving material using variable spatially selected excitation
    Patent number: 4836209
    Abstract: A method of imaging material flowing through a slab in a body using magnetic resonance techniques includes placing the body in a magnetic field including a first magnetic (z) gradient for slab thickness selection. A first rf pulse (180.degree.) is applied to the body at a frequency band and of sufficient strength to flip nuclear spins located essentially in the slab. After allowing moving material in the slab to flow from the slab, a second rf (90.degree.) pulse is applied to the body at a frequency band of sufficient strength to flip the nuclear spins in the slab for generating a signal. First image date in an X-Z plane is obtained from the nuclear spins flipped by the second 90.degree. rf pulse. Thereafter, a third 180.degree. rf pulse is applied to the body. In one embodiment the third rf pulse is non-selective and is of sufficient strength to flip nuclear spins in the body including but not limited to the slab. Moving material is again allowed to flow from the slab, and a fourth 90.degree.
    Type: Grant
    Filed: May 11, 1988
    Date of Patent: June 6, 1989
    Assignee: Stanford University
    Inventor: Dwight G. Nishimura
  • Controller for vehicle transmission with auxiliary transmission
    Patent number: 4697475
    Abstract: A controller for the hydraulic clutch of two speed auxiliary transmission connected in series with the main transmission and engine of a vehicle wherein the hydraulic clutch is applied for the higher speed drive and released for the lower speed drive which is through a one-way clutch that overruns in the higher speed drive operation. The controller is responsive to engine throttle opening to apply the hydraulic clutch for throttle openings below a predetermined amount to allow braking of the vehicle by the engine during deceleration rather than coasting by the overrunning of the one-way clutch.
    Type: Grant
    Filed: September 26, 1984
    Date of Patent: October 6, 1987
    Assignee: Honda Giken Kogyo Kabushiki Kaisha
    Inventors: Sadanori Nishimura, Noboru Sekine
  • Manual with auxiliary transmission
    Patent number: 4674358
    Abstract: A vehicular transmission in which a multiple speed manual transmission of the two parallel shaft type has an auxiliary transmission connected in series between the two shafts for some of the multiple speeds. The auxiliary transmission providing a high speed and a low speed. The auxiliary transmission includes gearing for providing the high or low speeds to the gears on one of the shafts. A hydraulic clutch and a one-way clutch in said auxiliary transmission selectively connect the high or low speed gearing, with the one-way clutch engaging when the hydraulic clutch is disengaged and being overrun when the hydraulic clutch is engaged.
    Type: Grant
    Filed: September 18, 1986
    Date of Patent: June 23, 1987
    Assignee: Honda Giken Kogyo Kabushiki Kaisha
    Inventor: Sadanori Nishimura
  • Compact transmission apparatus for a vehicle
    Patent number: 4793213
    Abstract: A compact transmission apparatus for a vehicle of the type wherein an input shaft and an output shaft are provided in parallel in a casing with the shaft supported at a middle wall and the front wall of the casing. Various speed driving trains are provided in the order from front to rear of third speed, second speed, fourth speed, reverse and first speed. The second speed driving train utilizes a front clutch mechanism of a double-type clutch, while the fourth speed driving train uses the rear clutch mechanism of the double-type clutch. The driving gear of the reverse driving train is made integral with the driving gear of the fourth speed driving train. A selection mechanism is provided between the driven gears of the reverse driving train and the fourth speed driving train to select for forward, highest speed movement or reverse movement.
    Type: Grant
    Filed: May 13, 1982
    Date of Patent: December 27, 1988
    Assignee: Honda Giken Kogyo Kabushiki Kaisha
    Inventor: Sadanori Nishimura
  • Control system for hydraulic transmission
    Patent number: 4570511
    Abstract: A control system for a hydraulic transmission for a vehicle powered by an internal combustion engine has a low speed clutch and a high speed clutch, both actuated hydraulically. An oil draining line is connected to a low speed clutch when a control valve assembly is in its high speed position. The control valve assembly has an orifice and a drain oil control valve arranged in parallel. The valve is moved toward closed position when there is an increase in the throttle valve opening of the engine driving the hydraulic transmission. The drain oil control valve includes a valve having an intermediate throttling position between open and closed positions. The drain oil control valve is moved to its open position when oil pressure fed to the high speed clutch increases to a predetermined pressure, which pressure varies in response to the opening of the engine throttle valve.
    Type: Grant
    Filed: October 15, 1982
    Date of Patent: February 18, 1986
    Assignee: Honda Giken Kogyo Kabushiki Kaisha
    Inventors: Sadanori Nishimura, Masakazu Maezono
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