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  • Variable density signal sampling
    Publication number: 20060062486
    Abstract: An optimal sampling pattern for variable density sampling of a continuous signal uses a statistical knowledge of the signal to determine an autocorrelation matrix from which a basis set is identified. Sampling is performed at locations determined from an eigenvector matrix, and the sampled output provides coefficients for the basis set. The reconstructed signal output is a summation of the multiplication of the coefficients and the basis set.
    Type: Application
    Filed: September 17, 2004
    Publication date: March 23, 2006
    Applicant: The Board of Trustees of the Lean Stanford Junior University
    Inventors: Jin Lee, Brad Osgood, Dwight Nishimura
  • Artifact reduction in SSFP MRI using weighted sum of combined signals
    Publication number: 20050030023
    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: Application
    Filed: August 5, 2003
    Publication date: February 10, 2005
    Inventors: Neal Bangerter, Dwight Nishimura
  • ARTIFACT REDUCTION IN STEADY-STATE FREE PRECESSION IMAGING
    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
  • Variable density signal sampling
    Patent number: 7330602
    Abstract: An optimal sampling pattern for variable density sampling of a continuous signal uses a statistical knowledge of the signal to determine an autocorrelation matrix from which a basis set is identified. Sampling is performed at locations determined from an eigenvector matrix, and the sampled output provides coefficients for the basis set. The reconstructed signal output is a summation of the multiplication of the coefficients and the basis set.
    Type: Grant
    Filed: September 17, 2004
    Date of Patent: February 12, 2008
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Jin Hung Lee, Brad Osgood, Dwight G. Nishimura
  • Multi-coil reconstruction of MRI signals using linear phase multiplied data with separate demodulators for each coil
    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
  • Partial flyback echo-planar imaging
    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
  • Deep Learning Method for Nonstationary Image Artifact Correction
    Publication number: 20190277935
    Abstract: A method for magnetic resonance imaging corrects non-stationary off-resonance image artifacts. A magnetic resonance imaging (MRI) apparatus performs an imaging acquisition using non-Cartesian trajectories and processes the imaging acquisitions to produce a final image. The processing includes reconstructing a complex-valued image and using a convolutional neural network (CNN) to correct for non-stationary off-resonance artifacts in the image. The CNN is preferably a residual network with multiple residual layers.
    Type: Application
    Filed: March 9, 2018
    Publication date: September 12, 2019
    Inventors: David Y. Zeng, Dwight G. Nishimura, Shreyas S. Vasanawala, Joseph Y. Cheng
  • Moving material projection imaging system using nuclear magnetic resonance
    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
  • Artifact reduction in steady-state free precession imaging
    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
  • Artifact reduction in SSFP MRI using weighted sum of combined signals
    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
  • ENHANCED SPECTRAL SELECTIVITY FOR STEADY-STATE FREE PRECESSION IMAGING
    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
  • Deep learning method for nonstationary image artifact correction
    Patent number: 11681001
    Abstract: A method for magnetic resonance imaging corrects non-stationary off-resonance image artifacts. A magnetic resonance imaging (MRI) apparatus performs an imaging acquisition using non-Cartesian trajectories and processes the imaging acquisitions to produce a final image. The processing includes reconstructing a complex-valued image and using a convolutional neural network (CNN) to correct for non-stationary off-resonance artifacts in the image. The CNN is preferably a residual network with multiple residual layers.
    Type: Grant
    Filed: March 9, 2018
    Date of Patent: June 20, 2023
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: David Y. Zeng, Dwight G Nishimura, Shreyas S. Vasanawala, Joseph Y. Cheng
  • Rapid measurement of time-averaged blood flow using ungated spiral phase-contrast MRI
    Publication number: 20030199750
    Abstract: Pulsatile flow is measured using magnetic resonance imaging without cardiac gating using a phase-contrast excitation method to rapidly quantify blood flow and using a spiral k-space trajectory for image data read-out to mitigate deleterious effects of pulsatility. Post-processing of the read-out data provides a cumulative-average velocity plot from which a period of a cardiac cycle is obtained. Time-averaged blood flow rates can be rapidly and robustly measured and is more repeatable than conventional gated techniques.
    Type: Application
    Filed: April 17, 2002
    Publication date: October 23, 2003
    Applicant: THE BOARD OF TRUSTEES OF THE LELAND STANFORD JUNIOR UNIVERSITY
    Inventors: Jong B. Park, Dwight G. Nishimura
  • Partial k-space reconstruction for radial k-space trajectories in magnetic resonance imaging
    Publication number: 20040258326
    Abstract: A modified projection on convex sets (POCS) algorithm and method for partial k-space reconstruction using low resolution phase maps for scaling full sets of reconstructed k-space data. The algorithm can be used with partial k-space trajectories in which the trajectories share a common point such as the origin of k-space, including variable-density spiral trajectories, projection reconstruction trajectories with a semicircle region acquisition, and projection reconstruction trajectories with every other spike acquired.
    Type: Application
    Filed: June 17, 2003
    Publication date: December 23, 2004
    Applicant: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Jin Hyung Lee, John M. Pauly, Dwight G. Nishimura
  • Magnetic resonance imaging of short T.sub.2 species
    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
  • Multiple pulse excitation in NMR imaging
    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
  • Partial k-space reconstruction for radial k-space trajectories in magnetic resonance imaging
    Patent number: 7277597
    Abstract: A modified projection on convex sets (POCS) algorithm and method for partial k-space reconstruction using low resolution phase maps for scaling full sets of reconstructed k-space data. The algorithm can be used with partial k-space trajectories in which the trajectories share a common point such as the origin of k-space, including variable-density spiral trajectories, projection reconstruction trajectories with a semicircle region acquisition, and projection reconstruction trajectories with every other spike acquired.
    Type: Grant
    Filed: June 17, 2003
    Date of Patent: October 2, 2007
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Jin Hyung Lee, John M. Pauly, Dwight G. Nishimura
  • Rapid measurement of time-averaged blood flow using ungated spiral phase-contrast MRI
    Patent number: 6957097
    Abstract: Pulsatile flow is measured using magnetic resonance imaging without cardiac gating using a phase-contrast excitation method to rapidly quantify blood flow and using a spiral k-space trajectory for image data read-out to mitigate deleterious effects of pulsatility. Post-processing of the read-out data provides a cumulative-average velocity plot from which a period of a cardiac cycle is obtained. Time-averaged blood flow rates can be rapidly and robustly measured and is more repeatable than conventional gated techniques.
    Type: Grant
    Filed: April 17, 2002
    Date of Patent: October 18, 2005
    Assignee: The Board of Trustees of the Leland Stanford Junior University
    Inventors: Jong B. Park, Dwight B. Nishimura
  • SYSTEM AND METHOD OF PARALLEL IMAGING WITH CALIBRATION TO A SEPARATE COIL
    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
  • Enhanced spectral selectivity for steady-state free precession imaging
    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
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