Abstract: A single-sided magnet and magnetic resonance imaging (“MRI”) system are portable and lightweight, enabling use as a point-of care (“POC”) MRI device. The portable MRI system includes a magnet assembly containing layers of magnet blocks, such as rare-earth magnet blocks. The magnet blocks are arranged in concentric rings in each layer, and surround a central aperture extending through the magnet assembly. The central aperture is sized to allow a medical instrument, such as a needle, to pass through the central aperture. The portable MRI system can therefore be used for image guidance in lumbar puncture (“LP”) and other medical procedures.

Abstract: A method for assessing peripheral nerve stimulation (PNS) for a coil geometry includes retrieving a PNS Huygens' P-matrix for a body model. The PNS Huygens' P-matrix is defined on a Huygens' surface enclosing the body model. The method further includes generating a coil specific PNS P-matrix for the coil geometry based on at least the PNS Huygens' P-matrix for the body model, determining at least one PNS threshold for the coil geometry based on the coil specific PNS P-matrix, and storing the at least one PNS threshold in a storage device.

Abstract: Asymmetric, single-channel radio frequency (“RF”) coils are provided for use with portable or other low-field magnetic resonance imaging (“MRI”) systems. In general, the asymmetric, single-channel RF coils make use of asymmetric, optimized winding configurations in order to reduce B1+ inhomogeneities and to reduce signal sensitivity outside of the desired imaging field-of-view (“FOV”).

Abstract: Electromagnetic interference (“EMI”) is mitigated for portable magnetic resonance imaging (“MRI”) systems using postprocessing interference suppression techniques that make use of EMI detectors external to the MRI system imaging volume to detect EMI signals and remove them from acquired magnetic resonance data. EMI correction models, including static transfer function-based models, dynamic transfer function-based models, correction weight-based models, or parallel imaging kernel-based models can be used to remove the EMI-related artifacts from the magnetic resonance data.

Abstract: Electromagnetic interference (“EMI”) is mitigated for portable magnetic resonance imaging (“MRI”) systems using postprocessing interference suppression techniques that make use of EMI detectors external to the MRI system imaging volume to detect EMI signals and remove them from acquired magnetic resonance data. EMI correction models, including static transfer function-based models, dynamic transfer function-based models, correction weight-based models, or parallel imaging kernel-based models can be used to remove the EMI-related artifacts from the magnetic resonance data.

Abstract: A method for acquiring a magnetic resonance image dataset of a field-of-view using an imaging protocol includes acquiring a low-resolution scout image dataset of the field-of-view, and sets of one or more additional k-space lines within a central region of k-space at regular intervals during the imaging protocol. A contrast of the low-resolution scout image dataset and a contrast of the sets of one or more additional k-space lines are matched and are independent of a contrast of the magnetic resonance image dataset. The low-resolution scout image dataset and the sets of one or more additional k-space lines are acquired after an at least approximately matched magnetization preparation and matched recovery times.

Abstract: A method for acquiring a magnetic resonance image dataset of a subject is disclosed, wherein k-space is sampled during the acquisition in a plurality of k-space lines having different positions in the phase encoding direction. The method includes: sampling a first part of k-space by acquiring a number of k-space lines; determining a subject motion trajectory including motion data of the subject at one or several time points during the acquisition; associating the motion data with the positions along the phase encoding direction(s) of the k-space lines which were or will be acquired at the time points of the motion data; analyzing the distribution of the motion data in k-space and calculating a metric of variation of the motion data; and selecting the positions of the k-space lines of a next part of k-space to be acquired in the imaging protocol, depending on the metric of variation.

Abstract: Systems and methods for designing and manufacturing electromagnetic coils for use with a magnetic resonance imaging (“MRI”) system are described. More particularly, described here are methods for designing and manufacturing gradient coils for producing magnetic field gradients with greater peripheral nerve stimulation (“PNS”) thresholds relative to conventional gradient coils. The gradient coil design is constrained using an oracle penalty that is computed to account for a PNS requirement for the coil. In other applications, the oracle penalty can be used to optimize driving patterns for an electromagnetic stimulation system, such that a target PNS requirement is achieved.

Abstract: A system and method are described for MRI excitation pulse design. The system can include a magnetic system that produces a main magnetic field over a portion of a subject for MRI imaging. The system can also include an RF system configured to transmit and receive an RF or B1+ field across at least a target region within the subject. The system may further include a gradient system configured to spatially encode the B1+ field using a gradient waveform. The system may also include a control system, which can be configured to control the RF system in order to generate an RF excitation pulse. The excitation pulse includes freely-shaped RF waveforms, gradient waveforms and, potentially shim array waveforms, selected by penalizing deviation of a flip-angle from a target distribution in order to achieve a target magnetization profile. The method can be applied to 3D and 2D slice-selective excitation and refocusing.

Abstract: A magnet assembly for a portable magnetic resonance imaging (MRI) system includes a former having a plurality of slots and a plurality of magnet blocks configured to create a single-sided permanent magnet. Each of the plurality of magnet blocks are positioned in one of the plurality of slots of the former. The arrangement of the plurality of magnet blocks is configured to optimize homogeneity over a target field of view for brain imaging and to form a cap-shaped configuration to be positioned on a head of a subject.

Abstract: Asymmetric, single-channel radio frequency (“RF”) coils are provided for use with portable or other low-field magnetic resonance imaging (“MRI”) systems. In general, the asymmetric, single-channel RF coils make use of asymmetric, optimized winding configurations in order to reduce B1+ inhomogeneities and to reduce signal sensitivity outside of the desired imaging field-of-view (“FOV”).

Abstract: Electromagnetic interference (“EMI”) is mitigated for portable magnetic resonance imaging (“MRI”) systems using postprocessing interference suppression techniques that make use of EMI detectors external to the MRI system imaging volume to detect EMI signals and remove them from acquired magnetic resonance data. EMI correction models, including static transfer function-based models, dynamic transfer function-based models, correction weight-based models, or parallel imaging kernel-based models can be used to remove the EMI-related artifacts from the magnetic resonance data.

Abstract: A single-sided magnet and magnetic resonance imaging (“MRI”) system are portable and lightweight, enabling use as a point-of care (“POC”) MRI device. The portable MRI system includes a magnet assembly containing layers of magnet blocks, such as rare-earth magnet blocks. The magnet blocks are arranged in concentric rings in each layer, and surround a central aperture extending through the magnet assembly. The central aperture is sized to allow a medical instrument, such as a needle, to pass through the central aperture. The portable MRI system can therefore be used for image guidance in lumbar puncture (“LP”) and other medical procedures.

Abstract: Systems and methods are provided for improving MRI data acquisition efficiency while providing more detailed information with high resolution and isotropic resolution without gaps. Improved data acquisition efficiency may be achieved by implementing a machine learning algorithm with a hardware processor and a memory to estimate imperfections in fast imaging sequences, such as a multi-shot echo planar imaging (MS-EPI) sequence. These imperfections, such as patient motion, physiological noise, and phase variations, may be difficult to model or otherwise estimate using standard physics-based reconstructions.

Abstract: Provided herein are systems and methods for development and use of a perfusion apparatus comprising a biological phantom created from an ex vivo placenta. In some embodiments, a system is provided for perfusing an ex vivo placenta to be imaged using a magnetic resonance imaging (MRI) device, the system comprising a chamber configured to house the ex vivo placenta therein, the chamber including a first partition separating the chamber into a first portion and a second portion, wherein the ex vivo placenta is housed at least partially in the first portion, and at least one first inlet disposed in the second portion for receiving at least one first tube, the at least one first tube being configured to couple at least one first pump to a fetal compartment of the ex vivo placenta when present in the chamber.

Abstract: Systems and methods for designing and manufacturing electromagnetic coils for use with a magnetic resonance imaging (“MRI”) system are described. More particularly, described here are methods for designing and manufacturing gradient coils for producing magnetic field gradients with greater peripheral nerve stimulation (“PNS”) thresholds relative to conventional gradient coils. The gradient coil design is constrained using an oracle penalty that is computed to account for a PNS requirement for the coil. In other applications, the oracle penalty can be used to optimize driving patterns for an electromagnetic stimulation system, such that a target PNS requirement is achieved.

Abstract: Systems and methods are provided for improving MRI data acquisition efficiency while providing more detailed information with high resolution and isotropic resolution without gaps. Improved data acquisition efficiency may be achieved by implementing a machine learning algorithm with a hardware processor and a memory to estimate imperfections in fast imaging sequences, such as a multi-shot echo planar imaging (MS-EPI) sequence. These imperfections, such as patient motion, physiological noise, and phase variations, may be difficult to model or otherwise estimate using standard physics-based reconstructions.

Abstract: A method for assessing peripheral nerve stimulation (PNS) for a coil geometry includes retrieving a PNS Huygens' P-matrix for a body model. The PNS Huygens' P-matrix is defined on a Huygens' surface enclosing the body model. The method further includes generating a coil specific PNS P-matrix for the coil geometry based on at least the PNS Huygens' P-matrix for the body model, determining at least one PNS threshold for the coil geometry based on the coil specific PNS P-matrix, and storing the at least one PNS threshold in a storage device.

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: A conductive lead apparatus for an implantable medical device includes a first conductor having a first outer diameter and a length, a high-dielectric constant layer having a second outer diameter and disposed around the first outer diameter of the first conductor, and a second conductor disposed around the second outer diameter of the high dielectric constant layer. The first conductor, high dielectric constant layer and the second conductor form a distributed capacitance along the length of the first conductor.