Abstract: The present disclosure provides systems and methods for measuring a concentration of a contrast agent using magnetic resonance imaging (MRI). The method includes acquiring pre- and post-contrast data from a volume of a subject, where the pre-contrast data is acquired before a contrast agent is administered and the post-contrast data is acquired after the contrast agent is administered. Pre- and post-contrast resonance frequency maps are then computed, where the pre-contrast frequency map is based on one or more pre-contrast resonance frequency values, and the post-contrast resonance frequency map is based on one or more post-contrast resonance frequency values. The pre- and post-contrast frequency maps are then used to generate a resonance frequency change map that is subsequently used to generate a contrast agent concentration map that indicates a concentration of the contrast agent that was present at each voxel in the volume at the second time.

Abstract: Systems and methods for generating a three-dimensional image of an object from multiple two-dimensional images acquired using a magnetic resonance imaging (“MRI”) system are provided. The three-dimensional image has high spatial resolution in all three spatial dimensions. The multiple two-dimensional images can be acquired in one or more orientations (e.g., axial, coronal, sagittal, oblique). The in-plane resolution of these images can be several times finer than the through-plane resolution (i.e., the slice thickness). The images are Fourier transformed along their respective slice orientation direction and processed using the slice profile to generate a Fourier representation of the three-dimensional image with the target spatial resolution. Inverse Fourier transforming this Fourier representation generates the desired three-dimensional image.

Abstract: Systems and methods for generating a three-dimensional image of an object from multiple two-dimensional images acquired using a magnetic resonance imaging (“MRI”) system are provided. The three-dimensional image has high spatial resolution in all three spatial dimensions. The multiple two-dimensional images can be acquired in one or more orientations (e.g., axial, coronal, sagittal, oblique). The in-plane resolution of these images can be several times finer than the through-plane resolution (i.e., the slice thickness). The images are Fourier transformed along their respective slice orientation direction and processed using the slice profile to generate a Fourier representation of the three- dimensional image with the target spatial resolution. Inverse Fourier transforming this Fourier representation generates the desired three-dimensional image.

Abstract: The present disclosure provides systems and methods for measuring a concentration of a contrast agent using magnetic resonance imaging (MRI). The method includes acquiring pre- and post-contrast data from a volume of a subject, where the pre-contrast data is acquired before a contrast agent is administered and the post-contrast data is acquired after the contrast agent is administered. A pre- and post-contrast resonance frequency map are then computed, where the pre-contrast frequency map is based on one or more pre-contrast resonance frequency values, and the post-contrast resonance frequency map is based on one or more post-contrast resonance frequency values. The pre- and post-contrast frequencies maps are then used to generate a resonance frequency change map that is subsequently used to generate a contrast agent concentration map that indicate a concentration of the contrast agent that was present at each voxel in the volume at the second time.

Abstract: Accelerated dynamic magnetic resonance imaging (“MRI”) methods in which low-rank matrix completion is implemented as a pre-processing step to fill undersampled accelerated k-space while retaining both spatial and temporal resolution are described. The undersampled k-space data are acquired using multilevel sampling, in which both uniform undersampling and non-uniform undersampling are combined to achieve high temporal resolution while retaining spatial resolution.

Abstract: A method of producing a series of vasculature images over an extended field of view (FOV) larger than an FOV of an MRI system includes acquiring initial time-resolved image data from the vasculature and, during the acquiring process, reconstructing, in substantially real-time, a series of three-dimensional (3D) tracking images of the initial portion of the vasculature illustrating a current position of a contrast bolus in the vasculature as the contrast bolus passes through the initial portion of the vasculature. Based on a current position of the contrast bolus, the subject is moved to a subsequent imaging station to acquire subsequent time-resolved image data and reconstruct subsequent 3D tracking images of subsequent portions of the vasculature. This process is repeated and then an image is assembled that extends over the extended FOV using the initial time-resolved image data and the subsequent time-resolved image data.

Abstract: A system and method for performing parallel magnetic resonance angiography includes controlling operation of a magnetic gradient system and an RF system to perform a calibration data pulse sequence to begin acquiring calibration data for use in a parallel imaging reconstruction process after receiving an indication that the subject has received a dose of a contrast agent. The acquisition of the calibration data is discontinued before the contrast agent reaches a peak concentration within a region of interest (ROI) of the subject and operation of the magnetic gradient system and RF system is controlled to perform an imaging pulse sequence in accordance with a parallel imaging acquisition to begin acquiring image data from the ROI. The image data is reconstructed into an image of the ROI using the calibration data.

Abstract: A system and method are provided for producing a magnetic resonance image of a subject with a magnetic resonance imaging (MRI) system. The method includes acquiring k-space image data from a subject arranged in an MRI system by performing a pulse sequence. To perform the pulse sequence the MRI system divides k-space into a plurality of radially-extending sectors extending along a radial direction away from an origin of k-space. The plurality of radially-extending sectors include a width transverse to the radial direction that is defined by a vane angle chosen to be greater than a floating point precision of the trigonometric functions that define the radially-extending sectors. The MRI system acquires imaging data from at least the radially-extending sectors to undersample the periphery of k-space by only sampling k-space within the plurality of radial sectors and reconstructs an image of the subject using the imaging data.

Abstract: A method for three-dimensional parallel magnetic resonance imaging (MRI) using an MRI system is provided. The method includes determining in-plane acceleration factors that optimize a selected criterion, such as an image quality criterion defined by maximal noise amplification in a reconstructed image. The estimated in-plane acceleration factors are used to establish a k-space sampling pattern, which is used to acquire k-space data. An image is reconstructed from the acquired k-space data using a parallel image reconstruction technique.

Abstract: A system and method are provided for producing a magnetic resonance image of a subject with a magnetic resonance imaging (MRI) system. The method includes acquiring k-space image data from a subject arranged in an MRI system by performing a pulse sequence. To perform the pulse sequence the MRI system divides k-space into a plurality of radially-extending sectors extending along a radial direction away from an origin of k-space. The plurality of radially-extending sectors include a width transverse to the radial direction that is defined by a vane angle chosen to be greater than a floating point precision of the trigonometric functions that define the radially-extending sectors. The MRI system acquires imaging data from at least the radially-extending sectors to undersample the periphery of k-space by only sampling k-space within the plurality of radial sectors and reconstructs an image of the subject using the imaging data.

Abstract: A method for producing a time-series of images of a subject with a magnetic resonance imaging (MRI) system is provided. The MRI system is used to acquire a time-series undersampled k-space data set, in which a selected number of k-space data subsets in the time-series data set includes both image data and calibration data. Moreover, the calibration data in each of these selected number of k-space data subsets includes a portion of a desired total amount of calibration data. For example, each of these selected number of k-space data subsets include calibration data that is acquired by sampling a different partition of a calibration data sampling pattern. A time-series of images of the subject is then produced by reconstructing images of the subject from the acquired time-series of undersampled k-space data sets. These images are substantially free of undersampling artifacts.

Abstract: A method for performing magnetic resonance angiography and perfusion imaging using the same pulse sequence is provided. Time-resolved image data is acquired as a contrast agent passes through a subject. This image data is acquired by sampling Cartesian points in k-space that are contained within either a central region of k-space, or one of a plurality of different sets of radial sectors extending outwards from the central region. The image data is combined to form individual image frame data sets that are then reconstructed to produce a time series of image frames. From this time series, MR angiograms and perfusion maps are produced. With the added acquisition of calibration data, T1 relaxation parameters are estimated and quantitative perfusion maps produced.

Abstract: A system and method for creating at least one angiographic image using a magnetic resonance imaging (MRI) system includes acquiring, with the MRI system and using parallel imaging techniques, a pre-contrast image data set and a post-contrast image data set of a portion of a subject having a vascular structure extending therethrough and subtracting the pre-contrast and the post-contrast image data set to generate a difference angiogram data set. The method includes reconstructing the difference angiogram data set into at least one aliased angiogram, creating a region of interest (ROI) mask from an image of the portion of the subject, and indicating a masking border surrounding the vascular structure and substantially excluding tissues surrounding the vascular structure. The method then includes de-aliasing the at least one aliased angiogram using the ROI mask to create an angiogram of the portion of the subject.

Abstract: A method for three-dimensional parallel magnetic resonance imaging (MRI) using an MRI system is provided. The method includes determining in-plane acceleration factors that optimize a selected criterion, such as an image quality criterion defined by maximal noise amplification in a reconstructed image. The estimated in-plane acceleration factors are used to establish a k-space sampling pattern, which is used to acquire k-space data. An image is reconstructed from the acquired k-space data using a parallel image reconstruction technique.

Abstract: A system and method for creating at least one angiographic image using a magnetic resonance imaging (MRI) system includes acquiring, with the MRI system and using parallel imaging techniques, a pre-contrast image data set and a post-contrast image data set of a portion of a subject having a vascular structure extending therethrough and subtracting the pre-contrast and the post-contrast image data set to generate a difference angiogram data set. The method includes reconstructing the difference angiogram data set into at least one aliased angiogram, creating a region of interest (ROI) mask from an image of the portion of the subject, and indicating a masking border surrounding the vascular structure and substantially excluding tissues surrounding the vascular structure. The method then includes de-aliasing the at least one aliased angiogram using the ROI mask to create an angiogram of the portion of the subject.

Abstract: A method for performing magnetic resonance angiography and perfusion imaging using the same pulse sequence is provided. Time-resolved image data is acquired as a contrast agent passes through a subject. This image data is acquired by sampling Cartesian points in k-space that are contained within either a central region of k-space, or one of a plurality of different sets of radial sectors extending outwards from the central region. The image data is combined to form individual image frame data sets that are then reconstructed to produce a time series of image frames. From this time series, MR angiograms and perfusion maps are produced. With the added acquisition of calibration data, T1 relaxation parameters are estimated and quantitative perfusion maps produced.

Abstract: The present invention provides an MRI system for imaging of a subject over extended field-of-view (FOV) that employs both accelerated data acquisition, which is employed while the subject is stationary, and traditional data acquisition, which is employed while the subject is moved through the MRI system. This approach provides improved spatial resolution and time efficiency compared to traditional extended FOV imaging techniques.

Abstract: A system and method for performing parallel magnetic resonance angiography includes controlling operation of a magnetic gradient system and an RF system to perform a calibration data pulse sequence to begin acquiring calibration data for use in a parallel imaging reconstruction process after receiving an indication that the subject has received a dose of a contrast agent. The acquisition of the calibration data is discontinued before the contrast agent reaches a peak concentration within a region of interest (ROI) of the subject and operation of the magnetic gradient system and RF system is controlled to perform an imaging pulse sequence in accordance with a parallel imaging acquisition to begin acquiring image data from the ROI. The image data is reconstructed into an image of the ROI using the calibration data.

Abstract: An improved self-calibration method for accelerated magnetic resonance imaging (MRI) using inversion recovery pulse sequences allows calibration data for determining coil sensitivity profiles to be acquired by employing a calibration pulse sequence within the delay time of an inversion recovery pulse sequence. The calibration pulse sequence includes a constrained number of calibration pulses having small flip angles so that acceptable longitudinal magnetization recovery is provided.

Abstract: A method for producing a time-series of images of a subject with a magnetic resonance imaging (MRI) system is provided. The MRI system is used to acquire a time-series undersampled k-space data set, in which a selected number of k-space data subsets in the time-series data set includes both image data and calibration data. Moreover, the calibration data in each of these selected number of k-space data subsets includes a portion of a desired total amount of calibration data. For example, each of these selected number of k-space data subsets include calibration data that is acquired by sampling a different partition of a calibration data sampling pattern. A time-series of images of the subject is then produced by reconstructing images of the subject from the acquired time-series of undersampled k-space data sets. These images are substantially free of undersampling artifacts.