Search Patents
  • Publication number: 20080272777
    Abstract: A method of reducing artifacts in steady-state free precession (SSFP) signals for use in magnetic resonance imaging is provided. A plurality of SSFP imaging sequences is applied to an object. An imaging data for each of the SSFP imaging sequences is acquired. The imaging data is combined using a weighted combination where weights depend on a control parameter that adjusts a trade-off between banding artifact reduction and signal to noise ratio (SNR).
    Type: Application
    Filed: May 4, 2007
    Publication date: November 6, 2008
    Inventors: Tolga Cukur, Dwight G. Nishimura
  • Patent number: 5957843
    Abstract: Flyback imaging is combined with echo planar imaging (EPI) for improved readout flow properties. For increases in imaging time of 50% or less, significant improvements in imaging are realized. The partial flyback improves partial-Fourier EPI and inside-out EPI and can be applied to any EPI trajectory.
    Type: Grant
    Filed: August 14, 1995
    Date of Patent: September 28, 1999
    Assignee: Board of Trustees of the Leland Stanford Junior University
    Inventors: Gerard T. Luk Pat, Craig H. Meyer, John M. Pauly, Dwight G. Nishimura
  • Patent number: 4993414
    Abstract: A two-dimensional projection image of the NMR activity within a volume is obtained. The signals due to static material are not excited and do not appear in the projection image. The signals due to moving blood in vessels produce an isolated image of the vessels with the superimposed structure removed. Excitation systems are used which excite only moving material and return static material to equilibrium.
    Type: Grant
    Filed: August 28, 1989
    Date of Patent: February 19, 1991
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Albert Macovski, Dwight G. Nishimura
  • Patent number: 6806708
    Abstract: Imaging time using PILS is reduced by using multiple coils with localized sensitivities with each coil having a separate demodulation channel thereby permitting parallel signal processing and image reconstruction. Images from the multiple coils are then combined to form an image with a larger field of view (FOV).
    Type: Grant
    Filed: June 17, 2003
    Date of Patent: October 19, 2004
    Assignee: The Board of Trustees of the Leland Standford Junior University
    Inventors: Jin Hyung Lee, John M. Pauly, Dwight G. Nishimura
  • Patent number: 6906516
    Abstract: Artifact reduction in steady state free precession magnetic resonance imaging uses weighting of acquired image data to emphasize higher signals and then establishing an image signal based on the combined weighted signals. In one embodiment, a SSFP imaging sequence uses phase cycling and acquired image data is squared with the squared data then combined. The final image signal is based on the square root of the squared data.
    Type: Grant
    Filed: August 5, 2003
    Date of Patent: June 14, 2005
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Neal K. Bangerter, Dwight G. Nishimura
  • Patent number: 7439740
    Abstract: A method of reducing artifacts in steady-state free precession (SSFP) signals for use in magnetic resonance imaging is provided. A plurality of SSFP imaging sequences is applied to an object. An imaging data for each of the SSFP imaging sequences is acquired. The imaging data is combined using a weighted combination where weights depend on a control parameter that adjusts a trade-off between banding artifact reduction and signal to noise ratio (SNR).
    Type: Grant
    Filed: May 4, 2007
    Date of Patent: October 21, 2008
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Tolga Cukur, Dwight G. Nishimura
  • Publication number: 20080272778
    Abstract: A method of collecting image data with selective spectral suppression for at least two species is provided. A sequence of RF excitation pulses is repeatedly applied, whereby a repeated sequence of at least two substantially different spectrally selective steady-state magnetizations is established. Magnetic gradients are applied between said RF pulses. A plurality of magnetic resonance image (MRI) signals is acquired. The plurality of MRI signals is combined using a weighted combination where the weights depend on a control parameter that adjusts a trade-off between selective spectral suppression and signal-to-noise ratio (SNR).
    Type: Application
    Filed: May 4, 2007
    Publication date: November 6, 2008
    Inventors: Tolga Cukur, Dwight G. Nishimura
  • Patent number: 4672319
    Abstract: Improved nuclei excitation for NMR applications is provided by employing a sequence of RF pulses for exciting the nuclei. Non-linearities in pulse excitation are compensated by applying at least one additional RF pulse thereby improving slice definition and/or phase characteristics. In one application, one or more initial RF pulses establish an intermediate state for the nuclei from which the nuclei can be tilted to a final desired magnetic moment state by the application of a single RF pulse. The order of applying the magnetic pulses can be reversed when the flip/angle is 180 degrees.
    Type: Grant
    Filed: September 19, 1984
    Date of Patent: June 9, 1987
    Assignee: Stanford University
    Inventor: Dwight G. Nishimura
  • Patent number: 5025216
    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.
    Type: Grant
    Filed: July 28, 1989
    Date of Patent: June 18, 1991
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: John M. Pauly, Dwight G. Nishimura
  • Patent number: 7449884
    Abstract: A method of collecting image data with selective spectral suppression for at least two species is provided. A sequence of RF excitation pulses is repeatedly applied, whereby a repeated sequence of at least two substantially different spectrally selective steady-state magnetizations is established. Magnetic gradients are applied between said RF pulses. A plurality of magnetic resonance image (MRI) signals is acquired. The plurality of MRI signals is combined using a weighted combination where the weights depend on a control parameter that adjusts a trade-off between selective spectral suppression and signal-to-noise ratio (SNR).
    Type: Grant
    Filed: May 4, 2007
    Date of Patent: November 11, 2008
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Tolga Cukur, Dwight G. Nishimura
  • Publication number: 20080297152
    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: Application
    Filed: June 4, 2007
    Publication date: December 4, 2008
    Inventors: Anja C.S. Brau, Philip James Beatty, Dwight G. Nishimura
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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