Toshiba Medical Systems Corporation

Koninklijke Philips Corporation N.v.

Kabushiki Kaisha Toshiba

Picker International, Inc.

Canon Medical Systems Corporation

Wayne R Dannels

Andrew James Wheaton

Michael R Thompson

Dee H Wu

Michael Andrew Morich

Haiying Liu

David A Lampman

Mark J Loncar

David Leslie Foxall

Anuj Sharma

Thomas R McBride

William Sattin

Christopher K Anand

Takashi Shigeta

John Carlon

Robert Gauss

Yansun Xu

Larry Kasuboski

Heidi A Schlitt

Ad L Moerland

Chun Jiang Xiao

Leonard J Cikotte

Deepak V Bhat

To achieve a uniform magnetic field in an MRI system, fitting can be performed using a partially differentiated residue phase map, differentiated shim functions, radial weights, a regularization factor, a discontinuity mask, and/or a signal intensity mask to determine coefficients for shim functions. The fitting can be performed iteratively, where the regularization factor is stronger and the radial weights focus on areas of higher confidence during earlier iterations. During later iterations, the regularization factor gradually gets weaker and the radial weights gradually focus on areas of lower confidence.

System and method for robust shimming for magnetic resonance imaging

Magnetic resonance imaging (MRI) systems and methods to determine and/or correct slice leakage and/or residual aliasing in the image domain in accelerated MRI imaging. Some implementations process one slice of MRI image domain data by input to a sensitivity encoding (SENSE) un-aliasing matrix built from predetermined RF signal reception sensitivity maps, thereby producing SENSE-decoded MRI image domain data for one pass-through image slice and at least one extra slice, and determine inter-slice leakage and/or in-plane residual aliasing based on content of the at least one extra output slice from the SENSE-decoded MRI image domain data. Some implementations correct slice leakage in reconstructed images by generating a fractional leakage matrix of inter-slice leakage measurements, and by multiplying the inverted fractional leakage matrix with uncorrected reconstructed images.

Correcting residual aliasing in accelerated magnetic resonance imaging

A magnetic resonance imaging (MRI) system, method and/or computer readable medium is configured to effect improved parallel MR imaging with reduced unfolding artifacts by using either or both of:

Parallel MRI with spatially misregistered signal

An MRI system according to an embodiment includes an MRI sequence controller and an MRI system controller. Serving as a prescan unit, the MRI sequence controller performs a prescan for acquiring a sensitivity distribution of a coil. Serving as a main scan unit, the MRI sequence controller performs a main scan for acquiring signals of a magnetic resonance image. Serving as a corrector, the MRI system controller corrects the sensitivity distribution in accordance with a distortion that is contained in the magnetic resonance image and that results from the performing of the main scan. Serving as a generator, the MRI system controller generates an output magnetic resonance image using the corrected sensitivity distribution.

Magnetic resonance imaging apparatus

Described herein is an apparatus and method for reducing artifacts in MRI images. The method includes acquiring a first set of data by under-sampling a first portion of a k-space at a first rate, and a second set of data by under-sampling a second portion of the k-space at a second rate. The method generates a first intermediate image and a second intermediate image based on the acquired first set of data and the acquired second set of data, respectively, and constructs a difference image including artifacts based on the generated first intermediate image and second intermediate image. The method includes reconstructing a final image, by selectively combining the first intermediate image with the second intermediate image, wherein the combining is based on identifying, for each artifact included in the difference image, one of the first intermediate image and the second intermediate image as being a source of the artifact.

Apparatus and method for reducing artifacts in MRI images

Magnetic resonance imaging (MRI) systems and methods to effect accelerated MR image reconstruction for undersampled data acquisitions with radial strip acquisitions of k-space are described. The improved MR image reconstruction is performed by acquiring k-space data in accordance with a data acquisition pattern which comprises a plurality of strips leaving a plurality of undersampled areas therebetween that do not have another undersampled area in a diametrically opposed position of k-space. The acquired k-space data is then used to generate an MR image.

Accelerated MRI using radial strips and undersampling of k-space

In one embodiment a magnetic resonance imaging method includes the steps of comparing a first image and a second image to determine whether there is a distorted region present in the first image or the second image, each of the first image and second image having a total field of view that is the distance of the image along an axis, assigning an affected field of view to a width of the distorted region, determining an acceleration factor by dividing the total field of view of one or both of the first image and the second image by the affected field of view, acquiring sampled image data according to the acceleration factor of one or both of the first image and the second image and applying a mask to a third image in the affected field of view.

Magnetic resonance imaging method and magnetic resonance imaging apparatus

Eddy current fields in a magnetic resonance imaging (MRI) system are mapped by acquiring MRI data from an object located in an imaging volume of the MRI system. An MRI data acquisition sequence is preceded by a pre-sequence including (a) a gradient magnetic field transition that stimulates eddy current fields in the MRI system, and (b) a spatial modulation grid tag module that sensitizes a spatially resolved MR image of the acquired MRI data to the stimulated eddy current fields that existed during the spatial modulation grid tag module. The eddy-sensitized MR image is processed to calculate a spatially resolved map of fields produced by the eddy currents.

Mapping eddy current fields in MRI system

A magnetic resonance imaging apparatus according to an embodiment includes sequence controlling circuitry and image generating circuitry. The sequence controlling circuitry executes a pulse sequence which applies a excitation pulse and then continuously applies a readout gradient magnetic field with alternating polarity thereof and acquires echo signals continuously generated by the pulse sequence from a plurality of receive channels. The image generating circuitry corrects the echo signals so as to generate an image, correcting the echo signals for all of the receive channels collectively on the basis of phase differences between echo signals corresponding to even lines of k-space and echo signals corresponding to odd lines of k-space, and corrects the echo signals for each of the receive channels individually on the basis of magnitude differences between echo signals corresponding to the even lines of k-space and echo signals corresponding to the odd lines of k-space.

Magnetic resonance imaging apparatus and magnetic resonance imaging method

A magnetic resonance imaging (MRI) system, method and/or computer readable medium is configured to effect MR imaging with reduced artifact by generating one or more image reconstruction maps from one or more prescans, acquiring a main scan dataset from a main MRI scan of an object, warping one or more image reconstruction maps to have geometric distortions substantially corresponding to geometric distortions in the main scan dataset, and forming a diagnostic MR image of the object using the main scan dataset and the warped one or more image reconstruction maps.

Magnetic resonance imaging with consistent geometries

A magnetic resonance imaging (MRI) system, method and/or computer readable medium is configured to effect MR imaging with reduced ghosting artifacts by operations including determining spatially varying signal magnitude differences associated with first and second parts of a reference MR data, and reconstructing a diagnostic image based upon a first and a second parts of main scan data and the determined spatially varying signal magnitude differences. The first parts of the reference data and main scan data is acquired using a first readout gradient, and the second parts of the reference data and main scan data is acquired using a second readout gradient that is different from the first readout gradient.

MRI ghosting correction using unequal magnitudes ratio

A magnetic resonance imaging (MRI) system is used to produce an image representative of the vasculature of a subject by applying a non-contrast MRI pulse sequence to acquire MRI k-space data from non-stationary nuclei flowing in a selected spatial region of a subject after nuclei within the region have been subjected to spatially non-uniform pre-saturation of nuclear magnetic resonance (NMR) magnetization. Such pre-saturation suppresses subsequent MRI signals emanating from background nuclei located within said region during said pre-saturation, while enhancing MRI signal from flowing nuclei therewithin as a function of speed, slice thickness and elapsed time until image capture as a function of the spatially shaped profile of non-uniform pre-saturation across the imaged volume. Thus, acquired MRI k-space data can then be used to reconstruct an image representing vasculature of the subject.

Spatially shaped pre-saturation profile for enhanced non-contrast MRA

An MRI MAP prescan data from a predetermined imaged patient volume is decomposed to produce a transmit RF field inhomogeneity map and a receive RF field inhomogeneity map for the imaged patient volume based on a three-dimensional geometrical model of the inhomogeneity maps. At least one of the transmit RF field inhomogeneity map and the receive RF field inhomogeneity map is used to generate intensity-corrected target MRI diagnostic scan image data representing the imaged patient volume.

Spatial intensity correction for RF shading non-uniformities in MRI

Magnetic resonance imaging (MRI) produces an image representative of flowing nuclei within a subject. For each of plural MRI data acquisition sequences, a non-contrast pulsed ASL (arterial spin labeling) pre-sequence is applied to flowing nuclei in a tagging region during a tagging period (that occurs prior to MRI data acquisition from a selected downstream image region). The ASL pre-sequence includes plural different elapsed tagging times at which a radio frequency (RF) nuclear magnetic resonant (NMR) nutation tagging pulse occurs or does not occur in accordance with different predetermined patterns for corresponding different data acquisition sequences. Acquired MRI data is decoded in accordance with such predetermined patterns to detect MRI signals emanating from different cohorts of flowing nuclei that have been subjected to different combinations of nutation pulses. Acquired MRI data is used to reconstruct at least one image representing flowing nuclei within the selected image region.

Pulsed ASL using tagging pulse pattern encoding/decoding of flowing nuclei cohorts

Frequency filtering of spatially modulated or 'tagged' MRI data in the spatial frequency k-space domain with subsequent 2DFT to the spatial domain and pixel-by-pixel arithmetic calculations provide robust data that can be used to derive B1 and/or B0 maps for an MRI system.

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Mentor, OH, United States of America

Wayne R Dannels