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 |