General Electric Company

Advanced Mammography Systems, Inc.

Peter B Roemer

Otward M Mueller

William A Edelstein

Christopher Judson Hardy

Paul Arthur Bottomley

John Norton Park

William D Barber

Evangelos Trifon Laskaris

Charles L Dumoulin

Mark Ernest Vermilyea

Robert David Darrow

Bizhan Dorri

Ronald Dean Watkins

John F Schenck

Christopher P Yakymyshyn

John S Hickey

Jianyu Lian

Harvey E Cline

Matthew N O'Donnell

Christopher Thomas McNulty

Robert G Stevens

Robert Steven Stormont

Victor Taracila

William E Lorensen

Fraser John Laing Robb

Egidijus Edward Uzgiris

Kenneth William Rohling

Yuan Cheng

Robert Michael Vavrek

Cecil E Hayes

Stephen R MacMinn

William F Wirth

Larry Gene Turner

William McMurray

Dan Kenrick Spence

Antonio A Mogro-Campero

Perry S Frederick

Matthew G Eash

Thomas G McFarland

Kirby Gannett Vosburgh

Miguel Angel Navarro, Ii

Kenneth Marel Bradshaw

Robert D Black

Samuel M Blumenfeld

Richard L St Peters

Shuying Huang

Icko T Iben

Walter Albert Zimmermann

Douglas A Kelley

Xiaole Hong

Robert M Weisskoff

Youqing Zhang

Various methods and systems are provided for a disconnecting a receive coil from a transmit coil of a magnetic resonance (MR) system during a transmit operation. In one example, a cabling system may include a first line of coil-interfacing cable having a first set of hybrid switches, the first set of hybrid switches including a first switch, a first resonance circuit, and a second switch connected in series, and a second line of the coil-interfacing cable having a second set of hybrid switches, the first line and the second line of the coil-interfacing cable operably coupling one or more radio frequency (RF) coil elements to respective channels of the MR system. By positioning the first and the second sets of hybrid switches along different locations along the coil-interfacing cables, and simultaneously operating each set of hybrid switches, common mode currents may be interrupted along the coil-interfacing cables.

Systems and methods for disconnecting an MRI RF coil

A system and method are presented that facilitate imaging of the joints of the upper and lower extremities including, for example, the hip and shoulder as well as sections of the spine, among others. One embodiment of the invention includes a short bore cylindrical magnet with an imaging volume smaller than that of a comparable whole body system, an articulated table that allows placement of the joint to be imaged in the center of the magnet homogeneous volume while maintaining a high degree of patient comfort and openness. The gradient and RF coils may be positioned above and below the patient instead of 360 degrees surrounding the patient. A smaller RF and gradient coil is made feasible because of the reduced imaging volume.

Dedicated system for msk joint imaging

An MRI RF coil has two resonant rings disposed along an axis. The resonant rings are inductively coupled, but are otherwise electrically isolated from one another. In an assembly having two such MRI RF coils, a decoupling element (e.g., a decoupling capacitor or inductor) electrically connected between one ring of one coil and one ring of the other coil decouples the coils.

MRI RF coil

The invention is directed to a gradient coil assembly for MR imaging which includes a gradient coil set comprising inner and outer gradient coils, the inner gradient coil located within the outer gradient coil and surrounding or otherwise proximate to an imaging volume. The system further includes means for selectively energizing the inner and outer gradient coils to generate a resultant gradient field in the imaging volume. The energized inner and outer gradient coils are also disposed to collectively generate an eddy current field component in a region between the outer coil and a conductive structure spaced-apart therefrom when the inner gradient coil is displaced along an axis from a specified position with respect to the outer gradient coil. A compensation coil is selectively positioned with respect to the inner and outer gradient coils, and means are provided for applying a compensation current to the compensation coil to generate a magnetic field which substantially cancels the eddy current component, the compensation current and the displacement of the inner coil along the axis from the specified position having a specified relationship.

Misalignment compensation for MR gradient coil assembly

An electro optical circuit for transmitting an information bearing signal, such as a signal in the RF, AF or microwave frequency domains, to a predetermined location includes a laser for generating coherent light to be used as a carrier, and an electro optical modulator for receiving the information signal and the coherent light and generating first and second modulated light signals which respectively comprise the coherent light modulated by the information signal and the coherent light modulated by the inversion of the information signal. The first and second modulated light signals are supplied to a detector at the predetermined location through separate optical paths. The detector converts the first modulated light signal into a first DC component, representing the laser-generated coherent light, and into a first information component representing the information signal, and converts the second modulated light signal into a second DC component which also represents the laser-generated coherent light, and into a second information component representing the inversion of the information signal and which is thus in an anti-phase relationship with the first information component. The detector combines the first and second DC current components so that they mutually nullify each another.

Electro-optical circuit for signal transmission

A magnetic resonance system includes a cylindrical shield disposed between a quadrature RF coil and surrounding gradient coils. The shield includes a pair of copper sheets separated by an insulating dielectric sheet. A pattern formed by cuts in one copper sheet aligns with the currents induced in the shield by one of the RF quadrature fields, and a pattern formed by cuts in the other copper shield aligns with the other RF quadrature field. The copper sheets are shorted together to prevent voltage breakdowns and short cuts are made in each to prevent gradient induced eddy currents.

Double-sided RF shield for RF coil contained within gradient coils used

To generate a magnetic resonance image of a region comprised of two species of nuclei that have non-identical Larmor frequencies, the nuclei are excited and two read-out gradient pulses are generated. The relative phase offset between the two species of nuclei is different at the center of the first pulse than at the center of the second pulse. Data acquired during the two read-out pulses are processed in accordance with these relative phase offsets.

Separation of fat and water magnetic resonance images

A circuit for amplifying signals received by the receive coil of a magnetic resonance (MR) system includes a preamplifier employing an active circuit device, such as a GaAs-MESFET or HEMT. The preamplifier is located proximate to the receive coil in order to maintain as high a signal-to-noise ratio as possible for the preamplifier output signals. A capacitance is coupled to the receive coil to form an input impedance matching network for the input of the preamplifier. The preamplifier output is coupled through a fiber optic cable to remotely located MR signal processing electronics, which further processes signals received by the MR receive coil and amplified by the preamplifier.

Preamplifier circuit for magnetic resonance system

An in-situ method of extracting contaminants from a soil volume comprises applying a radiofrequency (RF) excitation signal to heat the soil with an array of electrodes. The electrodes are inserted into the contaminated volume or inserted into a matrix of holes drilled into the volume. A first row of electrodes is electrically coupled to a shield of a coaxial cable, with a second row electrically coupled to the central conductor of the coaxial cable. RF energy is applied to pairs of electrode rows through the coaxial cable and a matching network is installed in front of the electrode-row pair to maximize power flow into the electrode-row pair. This results in very evenly distributed voltages which results in even heating. A balanced-to-unbalanced transformer (balun) is installed at the input to the matching network to prevent the deposition of RF energy outside the target volume and creation of voltages that could be hazardous to personnel. The electrodes are perforated and connected to collection tubes which collect volatilized contaminant vapors and pass the vapors to a vapor treatment unit for neutralization.

Radiofrequency ground heating system for soil remediation

A magnetic field gradient apparatus for use in a magnetic resonance (MR) imaging system employing open magnets allows access to a patient while the patient is being imaged. The magnetic field gradient apparatus employs two gradient coil assemblies and a gradient coil amplifier. Each gradient coil assembly has a gradient coil carrier with at least one gradient coil disposed on it. Each gradient coil carrier is comprised of a cylinder with a flange at one end. The gradient coil assemblies are positioned in the bore of each ring of the open magnet and spaced apart from each other allowing access to the patient. The gradient coil amplifier provides current through the gradient coils to create a magnetic field gradient which has high linearity inside an imaging volume. A coil is disposed on cylinders which surround each gradient coil assembly and fit inside the bore of each ring which acts as an active shield and minimizing eddy currents in conductors outside the gradient coil assemblies.

Open gradient coils for magnetic resonance imaging

A tracking system in which radiofrequency signals emitted by an invasive device such as a catheter, are detected and used to measure the position and orientation of the invasive device. The invasive device has a transmit coil attached near its end and is driven by a low power RF source to produce a dipole electromagnetic field that can be detected by an array of receive coils distributed around a region of interest. The position and orientation of the device as determined by the tracking system are superimposed upon independently acquired Medical Diagnostic images, thereby minimizing the radiographic exposure times. One or more invasive devices can be simultaneously tracked.

Tracking system to follow the position and orientation of a device with

A magnetic resonance (MR) imaging system for use in a medical procedure employs an open main magnet allowing access to a portion of a patient within an imaging volume, for producing a main magnetic field over the imaging volume; a set of open gradient coils which provide magnetic fields gradients over the imaging volume without restricting access to the imaging volume; a radiofrequency coil set for transmitting RF energy into the imaging volume to nutate nuclear spins within the imaging volume and receive an MR response signal from the nuclear spins; and a pointing device for indicating the position and orientation of a plane in which an image is to be acquired; an image control means for operating power supplies for the gradient coils and the RF coils to acquire an MR signal from the desired imaging plane; and a computation unit for constructing an image of the desired imaging plane. The MR imaging system is intended to operate to provide images to a physician during medical procedures to guide the physician in his procedures.

Magnetic resonance imaging system with pointing device

A gradient amplifier for use in magnetic resonance imaging equipment employs a low voltage DC power supply connected in series between a pair of higher voltage DC power supplies, the latter supplies serving to provide increased power for rapid gradient switching and the former supply providing correction current to produce the desired voltage output. The high voltage DC power supplies preferably comprise multiple DC units which can be combined to provide finer steps of control prior to correction by the lower voltage supply. The low voltage DC power supply preferably comprise one or more linear amplifiers connected in series, or one or more switchmode amplifiers connected in series. The DC power supplies are controlled in an open loop manner from a gradient signal that designates the desired current for the gradient coil and the amplifiers are operated in a closed loop responding to to a feedback signal from the gradient coil.

Split gradient amplifier for an MRI system

An apparatus for microscopic imaging employing nuclear magnetic resonance is constructed from a cryogenic probe which is situated in a conventional magnetic resonance imaging system. The cryogenic probe employs a number of chambers and cryogenic liquids which cool a superconductor resonator to very low temperatures. A sample tube for containing a small specimen is heated to a temperature above its freezing point by flowing nitrogen gas over the specimen. A secondary resonant circuit is inductively coupled to the superconducting resonator. A transceiver passes RF signals to be transmitted into the specimen through the secondary resonant circuit causing the superconducting resonator to transmit the RF signal into the specimen. The resonator then acts as a receive coil and receives a signal from the specimen which is inductively passed to the secondary resonator circuit from which an image is generated. The use of superconductors having low resistance and low temperatures causes noise to be significantly reduced, and the signal-to-noise ratio to be substantially increased.

Cryogenic probe for NMR microscopy

This invention relates to refrigerated superconducting eddy current free MR magnets having integrated gradient coils. In particular, the amount of resultant eddy currents produced by the magnet are substantially reduced while reducing the size and weight, and, therefore, the cost of the superconducting magnet required to produce an acceptable MR image.

Eddy current free MRI magnet with integrated gradient coils

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Schenectady, NY, United States of America

Peter B Roemer