Abstract: Systems and methods for magnetic resonance imaging (“MRI”) that address the geometric distortions and blurring common to conventional echo planar imaging (“EPI”) sequences, and that provide new temporal signal evolution information across the EPI readout, are described. Echo planar time-resolved imaging (“EPTI”) schemes are described to implement an accelerated sampling of a hybrid space spanned by the phase encoding dimension and the temporal dimension. In general, each EPTI shot covers a segment of this hybrid space using a zigzag trajectory with an interleaved acceleration in the phase-encoding direction. The hybrid space may be undersampled and a tilted reconstruction kernel used to synthesize additional data samples.

Abstract: Systems and methods for accelerated magnetic resonance imaging using a tilted reconstruction kernel to synthesize unsampled k-space data in phase encoded and point spread function (“PSF”) encoded k-space data are provided. Images reconstructed from the data have reduced B0-related distortions and reduced T2* blurring. In general, data are acquired with systematically optimized undersampling of the PSF and phase encoding subspace. Parallel imaging reconstruction is implemented with a B0 inhomogeneity informed approach to achieve greater than twenty-fold acceleration of the PSF encoding dimension. A tilted reconstruction kernel is used to exploit the correlations in the phase encoding-PSF encoding subspace.

Abstract: Systems and methods for accelerated diffusion-weighted magnetic resonance imaging using a tilted reconstruction kernel to synthesize unsampled k-space data in phase encoded and point spread function (“PSF”) encoded k-space data are provided. Images reconstructed from the data have reduced B0-related distortions and reduced T2* blurring. In general, data are acquired with systematically optimized undersampling of the PSF and phase encoding subspace. Parallel imaging reconstruction is implemented with a B0 inhomogeneity informed approach to achieve greater than twenty-fold acceleration of the PSF encoding dimension. A tilted reconstruction kernel is used to exploit the correlations in the phase encoding-PSF encoding subspace. Self-navigated phase corrections are computed from the acquired data and used to synthesize the unsampled k-space data.

Abstract: Systems and methods for simultaneous multislice (“SMS”} magnetic resonance imaging (“MRI”}, in which a random blip gradient encoding scheme is utilized to impart a different phase to each of a plurality of different slice locations. Because of the random blip gradient encoding, the amount of the imparted phase is randomized for each phase encoding step in a Cartesian k-space trajectory. This data acquisition strategy leads to incoherent aliasing artifacts across the simultaneously excited slices. Images of the individual slices can be reconstructed using a compressed sensing framework.

Abstract: A method for maximizing the signal-to-noise ratio (“SNR”) in a combined image produced using a parallel magnetic resonance imaging (“MRI”) technique is provided. The image combination used in such techniques require an accurate estimate of the noise covariance. Typically, the thermal noise covariance matrix is used as this estimate; however, in several applications, including accelerated parallel imaging and functional MRI, the noise covariance across the coil channels differs substantially from the thermal noise covariance. By combining the individual channels with more accurate estimates of the channel noise covariance, SNR in the combined data is significantly increased. This improved combination employs a regularization of noise covariance on a per-voxel basis.

Abstract: Systems and methods for estimating the actual k-space trajectory implemented when acquiring data with a magnetic resonance imaging (“MRI”) system while jointly reconstructing an image from that acquired data are described. An objective function that accounts for deviations between the actual k-space trajectory and a designed k-space trajectory while also accounting for the target image is optimized. To reduce the computational burden of the optimization, a reduced model for the parameters associated with the k-space trajectory deviation and the target image can be implemented.

Abstract: A portable magnetic resonance imaging (“MRI”) system that uses static magnetic field inhomogeneities in the main magnet for encoding the spatial location of nuclear spins is provided. Also provided is a spatial-encoding scheme for a low-field, low-power consumption, light-weight, and easily transportable MRI system. In general, the portable MRI system spatially encodes images using spatial inhomogeneities in the polarizing magnetic field rather than using gradient fields. Thus, an inhomogeneous static field is used to polarize, readout, and encode an image of the object. To provide spatial encoding, the magnet is rotated around the object to generate a number of differently encoded measurements. An image is then reconstructed by solving for the object most consistent with the data.

Abstract: Systems and methods for controlling a magnetic resonance imaging (MRI) system to simultaneously excite multiple different slice locations. A multiband (MB) radio frequency (RF) pulse waveform is combined with an RF pulse waveform that results in periodic excitation of the slice locations, such as a power independent of a number of slices (PINS) RF pulse waveform. Before combination, the MB RF pulse waveform is preferably transformed to traverse the excitation k-space trajectory defined by a plurality of slice-encoding gradient blips. The combined RF pulse waveform is used to generate an RF excitation field generated while the plurality of slice-encoding gradient blips are played out. The portions of the combined RF pulse associated with the MB RF pulse are played out during the gradient blips, and the portions associated with the PINS RF pulse are played out between the gradient blips.

Abstract: Described here are systems and methods for using excited slice profiles to improve the point spread function (“PSF”) of super-resolution slices in SLIDER acquisitions while preserving all of the advantages of the SLIDER technique. The techniques described here may generally be referred to as “Generalized SLIDER” (“g-SLIDER”).

Abstract: Described here are a system and method for designing radio frequency (“RF”) pulses for parallel transmission (“pTx”) applications, and particularly pTx applications in magnetization transfer (“MT”) magnetic resonance imaging (“MRI”). The concept of “SAR hopping” is implemented using a constrained optimization problem that simultaneously designs multiple RF sub-pulses to maximize power deposition in a bound proton pool while also minimizing local SAR across multiple bound proton pool excitation frequencies. This results in the set of RF waveforms that yield the best excitation profiles for all pulses while ensuring that the local SAR of the average of all pulses is below the regulatory limit imposed by the FDA. Pulses are designed simultaneously while constraining local SAR, global SAR, and peak voltage, explicitly.

Abstract: Described here are systems and methods for performing magnetic resonance imaging (“MRI”) using radio frequency (“RF”) phase gradients to provide spatial encoding of magnetic resonance signals rather than the conventional magnetic field gradients. Particularly, the systems and methods described here implement swept RF pulses (e.g., wideband, uniform rate, and smooth transition (“WURST”) RF pulses) and a quadratic phase correction to enable RF phase gradient encoding in inhomogeneous background (B0) magnetic fields.

Abstract: Described here are systems and methods for retrospectively estimating and correcting for rigid-body motion by using a joint optimization technique to jointly solve for motion parameters and the underlying image. This method is implemented for magnetic resonance imaging (“MRI”), but can also be adapted for other imaging modalities.

Abstract: A method for imaging a subject with a magnetic resonance imaging (MRI) system using controlled aliasing is provided. A radio frequency (RF) excitation field is applied to excite the spins in a volume-of-interest that may include multiple slice locations. Using the MRI system, a readout magnetic field gradient is established following the application of the RF excitation field to form echo signals. These echo signal receive a differential encoding by way of establishing, while the readout gradient is established, alternating magnetic field gradients along two directions, such as the partition-encoding and phase-encoding directions. Image data is acquired from the formed echo signals and images of the subject are reconstructed from the acquired image data.

Abstract: Spin-lock T1?-weighted images of a subject are acquired and processed to produce an image that is indicative of bioelectromagnetic activity in the subject. A spin-lock RF field B1? is produced such that the Larmor frequency in the rotating frame corresponds to the expected frequency of the bioelectromagnetic activity. As a result, the magnetic field fluctuations generated by the bioelectromagnetic currents shorten the T1? of the surrounding tissue, creating a contrast mechanism that is seen as a reduced MR signal in the T1?-weighted image that is produced.

Abstract: Systems and methods for simultaneously acquiring high-resolution images of a subject from multiple different slice locations using magnetic resonance imaging (“MRI”) are described. The present invention overcomes the aforementioned drawbacks by providing method for producing a plurality of images of a subject with a magnetic resonance imaging (“MRI”) system. A radio frequency (RF) excitation field is applied by the MRI system to a portion of a subject that includes a plurality of slice locations. First data are simultaneously acquired from each of the plurality of slice locations by the MRI system.

Abstract: A portable magnetic resonance imaging (“MRI”) system that uses static magnetic field inhomogeneities in the main magnet for encoding the spatial location of nuclear spins is provided. Also provided is a spatial-encoding scheme for a low-field, low-power consumption, light-weight, and easily transportable MRI system. In general, the portable MRI system spatially encodes images using spatial inhomogeneities in the polarizing magnetic field rather than using gradient fields. Thus, an inhomogeneous static field is used to polarize, readout, and encode an image of the object. To provide spatial encoding, the magnet is rotated around the object to generate a number of differently encoded measurements. An image is then reconstructed by solving for the object most consistent with the data.

Abstract: A system and method for medical imaging using a magnetic resonance imaging system includes performing a segmented echo planar imaging (EPI) pulse sequence. The pulse sequence includes performing multiple radio frequency (RF) excitation pulses designed to excite multiple imaging slices across the subject simultaneously. A gradient encoding scheme applied along the slice-encoding direction is implemented to impart controlled phase shifts to the different imaging slices. Additionally, the multiple RF excitation pulses can be designed to further control an overlap of imaging data acquired from adjacent slices of the multiple imaging slices based on a selected offset. The acquired imaging data is reconstructed using a parallel imaging reconstruction method that separates overlapped slices in the imaging data to provide a series of images with respective images for each of the multiple imaging slices across the subject.

Abstract: A method for multi-slice magnetic resonance imaging, in which image data is acquired simultaneously from multiple slice locations using a radio frequency coil array, is provided. By way of example, a modified EPI pulse sequence is provided, and includes a series of magnetic gradient field “blips” that are applied along a slice-encoding direction contemporaneously with phase-encoding blips common to EPI sequences. The slice-encoding blips are designed such that phase accruals along the phase-encoding direction are substantially mitigated, while providing that signal information for each sequentially adjacent slice location is cumulatively shifted by a percentage of the imaging FOV. This percentage FOV shift in the image domain provides for more reliable separation of the aliased signal information using parallel image reconstruction methods such as SENSE.

Abstract: Described here are a system and method for designing radio frequency (“RF”) pulses for parallel transmission (“pTx”) applications, and particularly pTx applications in magnetization transfer (“MT”) magnetic resonance imaging (“MRI”). The concept of “SAR hopping” is implemented using a constrained optimization problem that simultaneously designs multiple RF sub-pulses to maximize power deposition in a bound proton pool while also minimizing local SAR across multiple bound proton pool excitation frequencies. This results in the set of RF waveforms that yield the best excitation profiles for all pulses while ensuring that the local SAR of the average of all pulses is below the regulatory limit imposed by the FDA. Pulses are designed simultaneously while constraining local SAR, global SAR, and peak voltage, explicitly.

Abstract: Described here are systems and methods for using excited slice profiles to improve the point spread function (“PSF”) of super-resolution slices in SLIDER acquisitions while preserving all of the advantages of the SLIDER technique. The techniques described here may generally be referred to as “Generalized SLIDER” (“g-SLIDER”).