Patent application number | Description | Published |
20100134105 | Method For Reducing Maximum Local Specific Absorption Rate In Magnetic Resonance Imaging - A method for reducing maximum local specific absorption rate (“SAR”) in a magnetic resonance imaging (“MRI”) system is disclosed. More specifically, a plurality of candidate radio frequency (“RF”) pulses are designed and the manner in which they are applied to a subject is determined such that the maximum local SAR is substantially reduced relative to applying the candidate RF pulse that produces the lowest maximum local SAR alone. Put another way, this “time-multiplexing” of a set of RF pulses that each produce approximately the same excitation pattern yields a lower maximum local SAR than does transmitting the individual RF pulse having the lowest local SAR over many repetition times (“TRs”). A convex optimization method is utilized to determine the manner in which the RF pulses are multiplexed in time such that a substantially lower maximum local SAR is achieved. | 06-03-2010 |
20100156411 | METHOD FOR PRODUCING SPECTRAL-SPATIAL PARALLEL RF EXCITATION PULSES FOR MAGNETIC RESONANCE IMAGING - A method for producing a spatially and spectrally selective radiofrequency (“RF”) excitation pulse includes establishing a desired spatial RF excitation pattern and establishing a desired spectral RF excitation pattern. The method also includes estimating an RF transmission profile map indicative of the transmission characteristics of an RF coil and determining, from the desired spatial and spectral excitation patterns and the estimated RF transmission profile map, at least one magnetic field gradient waveform indicative of locations in k-space to which RF energy is to be deposited. The method further includes determining, from the established spatial and spectral excitation patterns, the estimated RF transmission profile map, and the determined at least one gradient waveform, at least one RF excitation pulse waveform that will produce the desired spatial and spectral excitation patterns. | 06-24-2010 |
20110254548 | METHOD FOR SIMULTANEOUS MULTI-SLICE MAGNETIC RESONANCE IMAGING - 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. In addition, the mitigation of phase accruals in the phase-encoding direction provides for the substantial suppression of pixel tilt and blurring in the reconstructed images. | 10-20-2011 |
20130181710 | Method for Simultaneous Multi-Slice Magnetic Resonance Imaging - 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. In addition, the mitigation of phase accruals in the phase-encoding direction provides for the substantial suppression of pixel tilt and blurring in the reconstructed images. | 07-18-2013 |
20150323633 | SYSTEMS AND METHODS FOR FAST MAGNETIC RESONANCE IMAGE RECONSTRUCTION USING A HEIRARCHICALLY SEMISEPARABLE SOLVER - Systems and methods for reconstructing images using a hierarchically semiseparable (“HSS”) solver to compactly represent the inverse encoding matrix used in the reconstruction are provided. The reconstruction method includes solving for the actual inverse of the encoding matrix using a direct (i.e., non-iterative) HSS solver. This approach is contrary to conventional reconstruction methods that repetitively evaluate forward models (e.g., compressed sensing or parallel imaging forward models). | 11-12-2015 |
20150346300 | Magnetic Resonance Fingerprinting (MRF) With Simultaneous Multivolume Acquisition - Magnetic resonance fingerprinting (MRF) with simultaneous multivolume acquisition (SMVA) is described. One example nuclear magnetic resonance (NMR) apparatus includes an NMR logic that repetitively and variably samples (k, t, E) spaces associated with different volumes (e.g., slices) in an object to simultaneously acquire sets of NMR signals that are associated with different points in the (k, t, E) spaces. Sampling is performed with t and/or E varying in a non-constant way. The NMR apparatus may also include a signal logic that produces an NMR signal evolution from the NMR signals and compares the NMR signal evolution to reference signal evolutions. Since different volumes are excited differently, resulting signal evolutions can be acquired simultaneously from the different volumes and NMR parameters may be simultaneously determined for the multiple volumes, which reduces acquisition time and parameter map creation time. | 12-03-2015 |
Patent application number | Description | Published |
20130002249 | Method for Reducing Local Specific Absorption Rate In Magnetic Resonance Imaging Using Radio Frequency Coil Array Dark Modes - A method for reducing local specific absorption rate (“SAR”) during imaging of a subject with a magnetic resonance imaging (“MRI”) system is provided. A radio frequency (“RF”) excitation pattern is selected for an RF coil array to be used during the imaging. In this RF excitation pattern, locations in which local SAR exceeds a preselected threshold value are identified. Examples of threshold values include regulatory limits on local SAR. Using the identified local SAR hotspot locations, a cancellation electric field pattern that is defined by so-called “dark modes” of the coil array is determined. Imaging of the subject commences using the RF coil array and the MRI system, in which the RF coil array is used to simultaneously produce an RF excitation field and a cancellation electric field using the respective field patterns. This simultaneous production of the RF excitation and cancellation electric fields reduces local SAR at the hotspot locations. | 01-03-2013 |
20130015854 | METHOD AND PROCESSOR AND MAGNETIC RESONANCE APPARATUS FOR DESIGNING RF PULSES TO MITIGATE OFF-RESONANCE EFFECTSAANM Adalsteinsson; ElfarAACI BelmonttAAST MAAACO USAAGP Adalsteinsson; Elfar Belmontt MA USAANM Fautz; Hans-PeterAACI ForchheimAACO DEAAGP Fautz; Hans-Peter Forchheim DEAANM Setsompop; KawinAACI CharlestownAAST MAAACO USAAGP Setsompop; Kawin Charlestown MA USAANM Wald; LawrenceAACI CambridgeAAST MAAACO USAAGP Wald; Lawrence Cambridge MA US - In a magnetic resonance apparatus and operating method therefor, and in a processor that is programmed to design RF pulses for operating such a magnetic resonance apparatus, the RF pulses are designed to mitigate off-resonance effects caused by inhomogeneity of the basic (B0) magnetic field in the magnetic resonance apparatus. The RF pulses of a parallel transmit array are designed with different spatial phase distributions, that deviate from a constant phase from pulse-to-pulse, with the absolute value of the difference between respective spatial phase distributions of any two successively radiated RF pulses corresponding to the off-resonance that is caused by B0-inhomogeneity during the time between the radiation of the successive pulses. Additionally, or separately, currents supplied to the shim coils can be taken into account in the design of the RF pulses as an additional degree of freedom, with the shimming of the basic magnetic field produced by the shim currents deviating from shim currents designed to ideally produce a homogenous B0 field. | 01-17-2013 |
20130099784 | Method for Magnetic Resonance Imaging with Controlled Aliasing - 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. | 04-25-2013 |
20150177353 | Method for Magnetic Resonance Imaging with Controlled Aliasing - 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. | 06-25-2015 |
20150310639 | SYSTEMS AND METHODS FOR FAST RECONSTRUCTION FOR QUANTITATIVE SUSCEPTIBILITY MAPPING USING MAGNETIC RESONANCE IMAGING - Described here are systems and methods for quantitative susceptibility mapping (“QSM”) using magnetic resonance imaging (“MRI”). Susceptibility maps are reconstructed from phase images using an automatic regularization technique based in part on variable splitting. Two different regularization parameters are used, one, λ, that controls the smoothness of the final susceptibility map and one, μ, that controls the convergence speed of the reconstruction. For instance, the regularization parameters can be determined using an L-curve heuristic to find the parameters that yield the maximum curvature on the L-curve. The μ parameter can be determined based on an l | 10-29-2015 |
20150323634 | Methods, Systems and Apparatuses for Rapid Segmented, Accelerated, and Simultaneous Multi-Slice Echo Planar Imaging - A method for accelerated segmented magnetic resonance (MR) image data acquisition includes using a plurality of RF pulses to excite one or more slices of an anatomical area of interest according to a predetermined slice acceleration factor. Next, a collapsed image comprising the slices is acquired using a consecutive segment acquisition process. Then, a parallel image reconstruction method is applied to the collapsed image to separate the collapsed image into a plurality of slice images. | 11-12-2015 |
20150346301 | Fast Group Matching For Magnetic Resonance Fingerprinting Reconstruction - Methods, apparatus, and other embodiments associated with producing a quantitative parameter map using magnetic resonance fingerprinting (MRF) are described. One example apparatus includes a data store that stores a grouped set of MRF signal evolutions, including a group representative signal and a low-rank representative, a set of logics that collects a received signal evolution from a tissue experiencing nuclear magnetic resonance (NMR) in response to an MRF excitation, a correlation logic that computes a correlation between a portion of the received signal evolution and a portion of a group representative signal, a pruning logic that generates a pruned grouped set, and a matching logic that determines matching quantitative parameters based on the received signal evolution and the low-rank representative. | 12-03-2015 |