Yale University

Siemens Healthcare Gmbh

The Ohio State University

Robert Todd Constable

Gigi Galiana

Markus Vester

Stefan Popescu

Peter Speier

Jason Stockmann

Lick-Kong Tam

Edgar Mueller

Jinghua Wang

Zhong-Lin Lu

Edgar Müller

Yuqing Wan

Gigi Galiana Stadtler

A method for magnetic resonance imaging uses an electromagnet [], which may have open geometry, to generate a spatially nonuniform magnetic field within an imaging region []. The current through the electromagnet is controlled to repeatedly cycle the nonuniform magnetic field between a high strength for polarizing spins and a low strength for spatial encoding and readout. Using RF coils [], excitation pulses are generated at a frequency that selects a non-planar isofield slice for imaging. The RF coils are also used to generate refocusing pulses for imaging and to generate spatial encoding pulses, which may be nonlinear. Magnetic resonance signals originating from the selected non-planar isofield slice of the nonuniform magnetic field in the imaging region [] are detected using the RF coils [] in parallel receive mode. MRI images are reconstructed from the parallel received magnetic resonance signals, e.g., using algebraic reconstruction.

MRI system using nonuniform magnetic fields

A system includes a magnetic resonance gradient accessory within an MRI system. The MRI system includes a magnet housing, a superconducting magnet generating a magnet field B0 to which a patient is subjected, shim coils, RF coils, receiver coils, magnetic gradient coils, and a patient table. The magnetic resonance gradient accessory creates local magnetic gradient fields critical to image generation and provides for diffusion encoding of a specific body region.

Magnetic resonance gradient accessory providing tailored gradients for diffusion encoding

A magnet assembly for magnetic resonance imaging is used to generate the basic magnetic field with a strength needed to produce the steady state or equilibrium position of nuclei or nuclear spins in magnetic resonance imaging. This magnet, or a part thereof, is vibrated or tilted or otherwise periodically moved so as to change its position and thereby generate a time-varying gradient field, which is used to enter the acquired magnetic resonance signals as raw data into k-space.

Magnetic resonance imaging with spatial encoding by fast moving or vibrating magnetic field generator components

A magnetic resonance scanner has a base, a C-arm mounted on the base, the C-arm having an inner surface curved in a C-shape, the C-shape defining a plane, a magnet mounted on the inner curved surface of the C-arm, the magnet generating a basic magnetic field for magnetic resonance imaging, and a drive mechanism mechanically connected to the magnet. The drive mechanism rotates the magnet around an axis that is orthogonal to the plane so as to selectively position the magnet in at least two magnet positions that are respectively above and beneath a patient, who is situated in the C-arm along or parallel to the axis.

Resonance data acquisition scanner with rotating basic field magnet

Efficient encoding of signals in an MRI image is achieved through a combination of parallel receiver coils, and nonlinear gradient encoding that varies dynamically in such a manner as to impose a unique phase/frequency time varying signal on each pixel in the field of view. Any redundancies are designed such that they are easily resolved by the receiver coil sensitivity profiles. Since each voxel has an essentially identifiable complex temporal signal, spatial localization is easily achieved with only a single echo acquisition.

Single-echo imaging with nonlinear magnetic gradients

Methods for correcting inhomogeneities of magnetic resonance (MR) images and for evaluating the performance of the inhomogeneity correction. The contribution of both transmit field and receiver sensitivity to signal inhomogeneity have been separately considered and quantified. As a result, their negative contributions can be fully corrected. The correction method can greatly enhance the accuracy and precision of MRI techniques and improve the detection sensitivity of pathophysiological changes. The performance of signal inhomogeneity correction methods has been evaluated and confirmed using phantom and in vivo human brain experiments. The present methodologies are readily applicable to correct signal intensity inhomogeneity artifacts produced in different imaging modalities, such as computer tomography, X-ray, ultrasound, and transmission electron microscopy.

Signal inhomogeneity correction and performance evaluation apparatus

In a method of magnetic resonance imaging, a set of nonlinear, mutually orthogonal magnetic gradient encoding fields are sequentially and separately generated in an imaging region []. Using multiple receiver coils having nonuniform sensitivity profiles, echo data representing signal intensities in the imaging region is sequentially acquired as the magnetic gradient encoding fields are sequentially generated []. A reconstructed image of the imaging region is computed from the acquired echo data [], and the reconstructed image is then be stored and/or displayed on a display monitor [

Accelerated MRI with nonlinear spatial encoding gradients

In MRI by excitation of nuclear spins and measurement of RF signals induced by these spins in the presence of spatially-varying encoding magnetic fields, signal localization is performed through recombination of measurements obtained in parallel by each coil in an encircling array of RF receiver coils. Through the use of magnetic gradient fields that vary both as first-order and second-order Z2 spherical harmonics with position, radially-symmetric magnetic encoding fields are created that are complementary to the spatial variation of the encircling receiver coils. The resultant hybrid encoding functions comprised of spatially-varying coil profiles and gradient fields permits unambiguous localization of signal contributed by spins. Using hybrid encoding functions in which the gradient shapes are thusly tailored to the encircling array of coil profiles, images are acquired in less time than is achievable from a conventional acquisition employing only first-order gradient fields with an encircling coil array.

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Madison, CT, United States of America

Robert Todd Constable