Patent classifications
G01R33/5617
Method and magnetic resonance apparatus to optimize a magnetic resonance data acquisition sequence
In a method to optimize a magnetic resonance sequence of a magnetic resonance apparatus, the magnetic resonance sequence includes first imaging parameters that, during acquisition of magnetic resonance images by the magnetic resonance sequence, the first imaging parameters produce acoustic noise with a first acoustic noise volume level and magnetic resonance images with image noise at a first signal-to-image noise ratio. An automatic optimization of the imaging parameters is implemented such that during acquisition of magnetic resonance images by the magnetic resonance sequence, the optimized imaging parameters produce acoustic noise with a second acoustic noise volume level and magnetic resonance images with image noise at a second signal-to-image noise ratio. The second acoustic noise volume is reduced by at least 3 dB relative to the first acoustic noise volume and the second signal-to-image noise ratio is reduced by a maximum of 35 percent relative to the first signal-to-image noise ratio.
MAGNETIC RESONANCE IMAGING APPARATUS AND MAGNETIC RESONANCE IMAGING METHOD
In a sequence of emitting a plurality of refocus RF pulses after one excitation RF pulse, in order to suppress a cusp artifact at a known magnetic field distortion generation position regardless of an imaging condition, such as a slice thickness or an FOV, between an excitation RF pulse and an initial refocus RF pulse, by generating a phase shift to transverse magnetization at the position, and by applying an extremely small dephase gradient magnetic field in the phase encoding direction and/or in the slice encoding direction, a signal value of an NMR signal (echo signal) is suppressed at the position, and the cusp artifact is deteriorated.
METHOD AND MAGNETIC RESONANCE APPARATUS FOR ACQUIRING MR DATA FROM MULTIPLE SLICES SIMULTANEOUSLY
In a method and apparatus for acquiring magnetic resonance (MR) data from a predetermined volume within an examination object, a control protocol for a gradient echo sequence is selected that specifies that gradient moments produced in said gradient echo sequence be balanced along all three spatial directions. In this gradient echo sequence a slice selection gradient is activated in a slice selection direction that produces a balanced gradient moment, with simultaneous radiation of an RF pulse that simultaneously excites nuclear spins in multiple slices of the examination object, with said excitation being repeated according to a repetition time. A phase of MR signals to be acquired from a same one of said multiple layers is varied from repetition time-to-repetition time. An additional gradient is activated in the slice selection gradient that produces an additional gradient moment that is constant over consecutive repetition times and thus overrides the condition of the gradient moments of the gradient echo sequence being balanced along said slice selection direction. The MR signals are acquired during activation of a readout gradient.
SYSTEMS AND METHODS FOR MAGNETIC RESONANCE BLACK-BLOOD THROMBUS IMAGING IN DETECTION OF CEREBRAL VENOUS THROMBOSIS
In various embodiments, the present invention teaches systems and methods for using T1-weighted black-blood MR imaging, with which a CVT can be well isolated from the surrounding tissues due to the signal suppression of flowing blood. In some embodiments, the invention teaches using black-blood imaging (3D variable-flip-angle turbo spin-echo acquisition) to directly visualize thrombi. In certain embodiments, the invention teaches using T1 weighted image contrast and isotropic sub-millimeter spatial resolution for accurate detection and staging of thrombi. In various embodiments, the invention allows for the detection of chronic thrombosis recanalization.
Method and apparatus for optimization of a pulse sequence for a magnetic resonance system
In a method and a pulse sequence optimization device to optimize a pulse sequence for a magnetic resonance system, wherein pulse sequence includes at least one refocusing pulse, a readout gradient pulse temporally situated after the refocusing pulse, and at least one readout spoiler pulse, the pulse duration of the readout gradient pulse is shortened while keeping the readout gradient moment constant, and the pulse shape of the readout spoiler pulse is adapted without changing a total spoiler moment. An optimally shortened pulse duration of the readout gradient pulse is achieved when, with the adaptation of the pulse shape of the readout spoiler pulse, a maximum amplitude of the readout spoiler pulse equals to the amplitude of the readout gradient pulse, and an edge steepness of the readout spoiler pulse is minimized.
METHOD FOR SIMULTANEOUS TIME-INTERLEAVED MULTISLICE MAGNETIC RESONANCE IMAGING
Methods for reducing scan time in magnetic resonance imaging (“MRI”), particularly when imaging three-dimensional image volumes, using a simultaneous time-interleaved multislice (“STIMS”) acquisition are described. The unused time in each repetition time (“TR”) period is exploited to provide an additional reduction in encoding time for a three-dimensional acquisition (e.g., a 3D whole brain coverage). Groups of spatially interleaved slices are excited in a single TR, with the excitation and acquisition of the groups of slices being interleaved in time.
METHOD AND APPARATUS FOR PARALLEL MAGNETIC RESONANCE DATA ACQUISITION
In a magnetic resonance (MR) apparatus and operating method, a first pulse sequence is executed in order to acquire echo signals from a target volume produced by radiation of a radio-frequency (RF) excitation pulse, thereby obtaining an original measurement dataset. A reference measurement dataset is then acquired by executing another pulse sequence immediately after acquisition of the aforementioned echo signals. These steps are repeated until the original measurement dataset has reached a predetermined degree of completeness that is still incomplete according to the Nyquist criterion. The original measurement dataset is then completed using the reference measurement dataset and a parallel acquisition technique.
Magnetic Resonance Method And Apparatus For Quantitative Simultaneous Multi-Slice Assessment Of Tissue Displacement, Deformation, And Related Biomarker Parameters
Embodiments relate to a magnetic resonance imaging (MRI) technique in which the two-dimensional (2D) Displacement Encoding with Stimulated Echoes (DENSE) imaging technique and the multiband technique are combined to provide a 2D multi-slice quantitative assessment of displacement, deformation, and mechanics indices of tissue. The scan time is equivalent to the short scan time of the conventional single slice 2D imaging while providing spatial volumetric coverage similar to three-dimensional (3D) imaging. The techniques are combined in both the sequence (i.e., data acquisition) and reconstruction sides. Quantification of tissue displacement and motion is achieved through the combination and further evaluation of tissue mechanical properties is provided by calculating different indices based on the displacement and motion values.
MR imaging using apt contrast enhancement and sampling at multiple echo times
The invention relates to a method of CEST or APT MR imaging of at least a portion of a body (10) placed in a main magnetic field B.sub.0 within the examination volume of a MR device. The method of the invention comprises the following steps: •a) subjecting the portion of the body (10) to a saturation RF pulse at a saturation frequency offset; •b) subjecting the portion of the body (10) to an imaging sequence comprising at least one excitation/refocusing RF pulse and switched magnetic field gradients, whereby MR signals are acquired from the portion of the body (10) as spin echo signals; •c) repeating steps a) and b) two or more times, wherein the saturation frequency offset and/or a echo time shift in the imaging sequence are varied, such that a different combination of saturation frequency offset and echo time shift is applied in two or more of the repetitions; •d) reconstructing a MR image and/or B.sub.0 field homogeneity corrected APT/CEST images from the acquired MR signals. Moreover, the invention relates to a MR device (1) for carrying out the method of the invention and to a computer program to be run on a MR device.
SELECTIVE SAMPLING FOR ASSESSING STRUCTURAL SPATIAL FREQUENCIES WITH SPECIFIC CONTRAST MECHANISMS
The disclosed embodiments provide a method for acquiring MR data at resolutions down to tens of microns for application in in vivo diagnosis and monitoring of pathology for which changes in fine tissue textures can be used as markers of disease onset and progression. Bone diseases, tumors, neurologic diseases, and diseases involving fibrotic growth and/or destruction are all target pathologies. Further the technique can be used in any biologic or physical system for which very high-resolution characterization of fine scale morphology is needed. The method provides rapid acquisition of signal at selected values in k-space, with multiple successive acquisitions at individual k-values taken on a time scale on the order of microseconds, within a defined tissue volume, and subsequent combination of the multiple measurements in such a way as to maximize SNR. The reduced acquisition volume, and acquisition of only signal values at select places in k-space, along selected directions, enables much higher in vivo resolution than is obtainable with current MRI techniques.