Toshiba America Mri, Inc.

Diasonics, Inc.

University of California

Kevin A Derby

James S Tropp

Leon Kaufman

K Christine Hawryszko

Mitsuaki A Arakawa

Joseph W Carlson

Barry M McCarten

William K Lu

Stephen Krasnor

A nuclear magnetic resonance imaging system is described. The nuclear magnetic resonance imaging system includes an RF transmit device formed as two rectangular coils arranged in planes orthogonal to one another and formed by two U-shaped loops. The U-shaped loops improve B.sub.1 field homogeneity in the vertical direction. The rectangular coils may be used in a four post MRI device to improve access to the body being imaged.

Spatially orthogonal rectangular coil pair suitable for vertical

In the present invention, an NMR radio-frequency coil suitable for head imaging is disclosed. The coil has a first current path for the generation of the magnetic field. The first current path lies in a first plane and has an arcuate region which is adapted to arch over the head of the patient. A second current path supplies current to the first current path. The second current path lies in a second plane which is substantially perpendicular to the first plane. The coil is suitable for use in a coupled resonator system.

NMR radio-frequency coil

A quadrature detection (QD) head coil assembly for use in magnetic resonance imaging (MRI) having a pair of orthogonally situated zero-pitch solenoidal windings is disclosed. The turns of each winding are serially connected along the solenoid surface in a predetermined axially-extending area by using dog leg connectors. Return coil connections (i.e., an RF connection between the first and last turn of each coil) is effected substantially adjacent to the dog leg interconnections so as to minimize the area of any equivalent return loop and thus to minimize the magnitude of any inter-coil coupling via such return loops. To further minimize possible inter-coil coupling, the return loops for each of the quadrature detection coils are preferably oriented so as to primarily couple to magnetic fields that are orthogonal to the main field of both the QD coils. The use of zero- pitch turfs in each solenoidal coil winding also substantially reduces possible inter-coil coupling.

MRI RF coil using zero-pitch solenoidal winding

In a phase encoded chemical shift imaging (CSI) system, phase shifting in k space is used to shift voxels so as to translate them in one or more dimensions so that one or more voxels maximally encloses an object of interest. The position of a structure of interest is located via a 1H 'scout' image, and the Shift Theorem for finite Fourier transforms is applied to shift voxel boundaries in one, two or three dimensions so as to maximally enclose the structure in a minimal number of voxels. Voxel shifts thus may be accomplished computationally by minimal manipulation of the raw data--after the patient has left the imaging facility. The resulting spectral data corresponding to the structure of interest is not as subject to dilution by spectrum of the surrounding tissue.

Fourier shifting of voxel boundaries in MR chemical shift imaging

A hybrid bird cage/Helmholtz RF coil provides a single composite RF coil for MRI spectroscopy involving at least two NMR nuclear species at respectively different RF frequencies. The bird cage portion may be tuned to the lower NMR frequency and coupled to a pair of quadrature-phase input/output ports so as to provide needed extra sensitivity and signal-to-noise ratio. At least one further RF input/output port provides coupling for a second, higher, MNR RF frequency.

Dual-tuned RF coil for MRI spectroscopy

An automated magnetic field shimming process for magnetic resonance spectroscopic imaging (MRSI) uses doubly phase encoded NMR spin echo responses in conjunction with multiple fourier transformation to derive a spectroscopic plot for each voxel in a three-dimensional array of voxels in an image volume (including portions of a living subject) which is to be subsequently subjected to MRSI using NMR FID or spin echo responses. The thus derived hydrogen peak frequency is taken as a measurement of existing static magnetic field intensity within that voxel and adjusted shim coil currents are calculated so as to reduce or minimize nonuniformity of the static magnetic field. A nonexistent pseudo shim coil having an assumed uniform shim contribution may enhance the resulting field homogeneity. The auto shimming procedure may be applied iteratively as required to achieve the predetermined degree of field uniformity.

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Kevin A Derby