Patent application number | Description | Published |
20090256570 | Method For Joint Sparsity-Enforced K-Space Trajectory and Radiofrequency Pulse Design - A system and method is provided for simultaneously designing a radiofrequency (“RF”) pulse waveform and a magnetic field gradient waveform in a magnetic resonance imaging (“MRI”) system. The method includes determining a desired pattern of RF excitation and determining, from the desired pattern of RF excitation, a plurality of k-space locations indicative of the magnetic field gradient waveform and a plurality of complex weighting factors indicative of RF energy deposited at each k-space location. The method also includes calculating, from the determined k-space locations, the magnetic field gradient waveform and calculating, from the complex weighting factors, the RF pulse waveform that will produce the desired pattern of RF excitation when produced with the calculated magnetic field gradient. | 10-15-2009 |
20100066361 | METHOD FOR FAST MAGNETIC RESONANCE RADIOFREQUENCY COIL TRANSMISSION PROFILE MAPPING - A system and method for producing an image indicative of characteristics of a radiofrequency (“RF”) coil with a magnetic resonance imaging (“MRI”) system is disclosed. The method includes acquiring MR signals while performing a pulse sequence with the MRI system and driving the RF coil at a selected transmission power. This process is repeated a plurality of times to drive the RF coil at a different transmission powers during each repetition. A plurality of images are reconstructed from the acquired MR signals and an image indicative of RF reception characteristics of the RF coil is produced from the reconstructed images. Subsequently, an image indicative of RF transmission characteristics of the RF coil is produced using the image indicative of the RF receiver response. More specifically, only one data acquisition is necessary for each RF coil element to produce the image indicative of the RF transmission characteristics for that coil element. | 03-18-2010 |
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 |
20130088225 | System for Reconstructing MRI Images Acquired in Parallel - A system for parallel image processing in MR imaging comprises multiple MR imaging RF coils for individually receiving MR imaging data representing a slice of patient anatomy. An MR imaging system uses the multiple RF coils for acquiring corresponding multiple image data sets of the slice. An image data processor comprises at least one processing device conditioned for, deriving a first set of weights for generating a calibration data set comprising a subset of k-space data of composite image data representing the multiple image data sets. The at least one processing device uses the calibration data set in generating a first MR image data set, deriving a second set of weights using the calibration data set and the generated first MR image data set and uses the second set of weights in generating a second MR image data set representing a single image having a reduced set of data components relative to the first composite MR image data set. | 04-11-2013 |
20130187650 | DYNAMIC B0 FIELD DETECTION BY MAGNETIC RESONANCE NAVIGATORS, AND CORRECTION FOR MULTICHANNEL RECEPTION AND/OR TRANSMISSION RF COIL CONFIGURATIONS - In a method for calculating a B | 07-25-2013 |
20130207652 | System for Accelerated Magnetic Resonance Imaging Using Parallel Coils - An MR imaging system uses multiple RF coils for acquiring corresponding multiple image data sets of a slice or volume of patient anatomy. An image data processor comprises at least one processing device conditioned for, deriving a first set of weights for weighted combination of k-space data of the multiple image data sets for generating a calibration data set comprising a subset of k-space data of composite image data representing the multiple image data sets. The image data processor uses the calibration data set in generating a first MR image data set, deriving the parameters of a probability distribution in response to the first set of weights and the first MR image data set and deriving a second set of weights and second MR image data set together using the probability distribution. | 08-15-2013 |
20140292337 | Decoupling of Parallel Transmission Arrays in Magnetic Resonance Imaging - A method of determining a decoupling matrix of a decoupling system for an array of coils of a parallel transmission magnetic resonance imaging (MRI) system includes obtaining impedance matrix data for the array of coils without the decoupling system, determining, based on the impedance matrix data for the array of coils, an objective function representative of deviation from a decoupled operating condition for the array of coils in which the array of coils are decoupled via the decoupling system, and defining, with a processor, a decoupling matrix representative of a set of impedances of the decoupling system with an iterative procedure that optimizes elements of the decoupling matrix to minimize the objective function and reach the decoupled operating condition. | 10-02-2014 |
Patent application number | Description | Published |
20080281183 | STIMULUS INDUCED ROTARY SATURATION FOR MAGNETIC RESONANCE FUNCTIONAL IMAGING - Spin-lock T | 11-13-2008 |
20090123384 | METHOD FOR MAGNETIC RESONANCE IMAGING USING STIMULUS INDUCED ROTARY SATURATION WITH A CONTRAST AGENT - A method and system for producing an image of a subject with a magnetic resonance imaging (MRI) system, in which the presence of a contrast agent is detected using a spin-lock pulse sequence, is described. More specifically, a contrast agent that induces saturation of magnetic resonance signals responsive to a spin-lock condition is administered to a subject. A spin-lock condition is subsequently established to saturate spins in proximity to the contrast agent. Image data is then acquired with an imaging pulse sequence and images indicative of the presence of the contrast agent are reconstructed. | 05-14-2009 |
20100026298 | Method for imaging Acoustically induced rotary saturation with a magnetic resonance imaging system - A method for producing a magnetic resonance image indicative of mechanical waves applied to a subject is provided. Mechanical waves are applied to the subject at a selected frequency to induce oscillatory motion in tissues within the subject at the same frequency. A spin-lock radiofrequency pulse, having a resonance frequency matched to that of the induced oscillatory motion, is applied to the subject. This results in a spin-lock condition, during which transverse magnetization experiences rotary saturation resulting from magnetic field fluctuations produced by the oscillatory motion. Image data is acquired from the saturated transverse magnetization and images are reconstructed. As a result of the rotary saturation, these images exhibit darkening in those voxel locations affected by the oscillatory motion. In this manner, an image indicative of the applied mechanical waves is produced. | 02-04-2010 |
20100052679 | Coil Array Mode Compression For Parallel Transmission Magnetic Resonance Imaging - A method for target-dependent, sparsity-enforced selection for choosing a substantially optimal connection of radiofrequency (“RF”) transmitters to the elements of the RF coil array is provided. In particular, a method is provided that selects the linear combinations of the “N” spatial mode profiles of a transmission RF coil array, such that the k-space trajectory and pulse duration acceleration capabilities of the array are advantageously utilized. A sparsity-enforcement method that determines a subset of the available spatial modes for a parallel transmission RF coil array is employed to this end. In this manner, the utilization of the encoding power of a highly-parallel N-mode coil array in a system with only “P” available excitation channels is enabled. | 03-04-2010 |
20100090693 | METHOD AND APPARATUS FOR CONTROLLING T1 RECOVERY PROCESS IN MAGNETIC RESONANCE MEASUREMENTS - Radiation damping (RD) is employed to hasten the recovery of longitudinal magnetization after RF excitation and signal readout in a magnetic resonance measurement cycle. A switch driven by the pulse sequence that performs the measurement cycle energizes a feedback RF coil driven by an amplified and phase shifted portion of the received MR signal. The recovery of longitudinal magnetization is thus under direct control of the MR system and enables the reduction of the otherwise inefficient waiting times that are required for natural T1 recovery of the excited spin magnetization. This enables shortened acquisition times, improved sensitivity, better spatial and temporal resolution, and reduction of motion artifacts that result from long acquisition times. | 04-15-2010 |
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 |
20100289494 | System and Method for Mode Mixing in Magnetic Resonance Imaging - The present invention provides a system and method for using a hardware-based compression of signals acquired with an magnetic resonance imaging (MRI) system. This allows a first multi-channel MR signal to be compressed to a second multi-channel MR signal having fewer channels than the first MR signal. This system and method reduces the number of RF receivers needed to achieve the sensitivity encoding benefits associated with highly parallel detection in MRI. Furthermore, the system and method reduces bottlenecks connection an MRI system's RF receiver and reconstruction computer and reduces the computational burden of image reconstruction. | 11-18-2010 |
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 |
20120256626 | PARALLEL TRANSMISSION RF PULSE DESIGN WITH LOCAL SAR CONSTRAINTS - A method of designing a parallel transmission radio frequency (RF) pulse for a magnetic resonance imaging (MRI) system includes compressing a model for a subject to be scanned by the MRI system into a plurality of voxel clusters, each voxel cluster defining a virtual observation point with a peak sensitivity to local specific absorption rate (SAR) for the voxel cluster, and defining the parallel transmission RF pulse based on an approximation of a minimization criterion having a local SAR component based on the peak sensitivity of each virtual observation point, the approximation comprising a weighted sum of the local SAR values for each virtual observation point. | 10-11-2012 |
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 |
20130063143 | Local SAR Constrained Parallel Transmission RF Pulse in Magnetic Resonance Imaging - A method of designing a parallel transmission radio frequency (RF) pulse for a magnetic resonance imaging (MRI) system includes compressing a model for a subject to be scanned by the MRI system into a plurality of virtual observation points within the model based on comparisons of peak sensitivity to local specific absorption rate (SAR), and defining the parallel transmission RF pulse that minimizes a weighted average of local SAR values with an iterative procedure that optimizes a set of weighting factors for the plurality of virtual observation points to maximize the minimized weighted average. | 03-14-2013 |
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 |
20130178734 | METHOD FOR MAGNETIC RESONANCE IMAGING USING SATURATION HARMONIC INDUCED ROTARY SATURATION - A system and method for producing an image of a subject with a magnetic resonance imaging system, in which the image depicts an image contrast indicative of rotary saturation produced in response to magnetic particles administered to the subject, are provided. An agent that includes magnetic particles is administered to the subject. An electromagnetic drive field is applied to the subject at a drive frequency so that the magnetic particles produce magnetic fields that oscillate at the drive frequency and harmonics thereof. A spin-lock field is then established at a spin-lock frequency that is a harmonic of the drive frequency in order to produce rotary saturation of nuclear spins affected by the magnetic fields produced by the magnetic particles. Image data is then acquired from the subject using the MRI system, from which an image of the subject that depicts an image contrast indicative of the produced rotary saturation is reconstructed. | 07-11-2013 |
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 |
20140111202 | System and Method for Portable Magnetic Resonance Imaging Using a Rotating Array of Magnets - 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. | 04-24-2014 |