University of California

Toshiba America Mri, Inc.

Toshiba America, Inc.

Mitsuaki A Arakawa

Leon Kaufman

Lawrence E Crooks

Barry M McCarten

Joseph W Carlson

John H Fehn

John C Hoenninger, Iii

William K Lu

John Van Heteren

Stephen Krasnor

William H Harrison

Hsu Chang

Sunyu Su

Masahiro Arakawa

David M Kramer

Jerome R Singer

Kevin A Derby

Christine Hawryszko

Ernesto Zepeda

Brenda G Nichols

Keiji Furui

Thomas McDermott

Takashi Minemura

Einar Tapio

John G Van Heteren

James V Reveaux

An inherently de-coupled sandwiched solenoidal array coil (SSAC) is disclosed for use in receiving nuclear magnetic resonance (NMR) radio frequency (RF) signals in both horizontal and vertical-field magnetic resonance imaging (MRI) systems. In its most basic configuration, the SSAC comprises two coaxial RF receive coils. The first coil of the array has two solenoidal (or loop) sections that are separated from one another along a common axis. The two sections are electrically connected in series but the conductors in each section are wound in opposite directions so that a current through the coil sets up a magnetic field of opposite polarity in each section. The second coil of the SSAC is disposed (&ldquo;sandwiched&rdquo;) between the two separated solenoidal sections of the first coil in a region where the combined opposing magnetic fields cancel to become a null. Due to the winding arrangement and geometrical symmetry, the receive coils of the array become electromagnetically &ldquo;de-coupled&rdquo; from one another while still maintaining their sensitivity toward receiving NMR signals. The multiple coil array arrangement also allows for selecting between a larger or smaller field-of-view (FOV) to avoid image fold-over problems without time penalty in image data acquisition. Alternative embodiments are disclosed which include unequal constituent coil diameters, unequal constituent coil windings, non-coaxial coil configurations, a three-coil quadrature detection (QD) SSAC arrangement, multiple SSAC arrangements, and optimized SSAC configurations for breast imaging in both horizontal and vertical-field MRI systems.

Inherently de-coupled sandwiched solenoidal array coil

An RF coil array arrangement for enhanced magnetic resonance imaging of the breast or spine regions of prone and supine patients within a vertically oriented B field is disclosed. Several RF coil array embodiments are disclosed that provide for both generating a nuclei nutation field pulse and acquiring nuclear magnetic resonance signals when functioning in an MRI apparatus environment that employs a vertical main magnetic field. A coil array may include one or more RF coils that are intended to be oriented such that their primary B field direction(s) are perpendicular to the vertical magnetic field of the MRI apparatus. Each coil array may further include one or more single loop or solenoidal coil(s) that are oriented having their central or longitudinal axis aligned parallel to the vertical main magnetic field so as to make advantageous use of non-axial field components associated with the coil(s) to further generate and receive desired NMR signal components.

RF coil array for vertical field MRI

An RF coil tuning circuit is disclosed in which two banks of parallel capacitive branches are provided. Each capacitive branch includes a fixed value capacitor, a relay and a PIN diode connected in series. An impedance of the tuning circuit is adjusted to the optimum VSWR=1 condition by first switching the eight PIN diodes to learn which open/closed condition applies the fixed value capacitors in the optimum combination. Then, the PIN diodes are all closed and the optimum combination is applied using the open/closed states of the relays.

Discrete step remotely adjustable matching circuit for MRI RF coils

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

A front end unit (32) for a magnetic resonance imaging (MRI) system (20) comprises a plurality of coil attachment ports (46) to which an RF signal or tuning signal is selectively routed thereby permitting, during operation, coils (22) to remain attached to each of the plurality of ports. A signal routing controller (28, 30) selects to which of the ports the RF signal or tuning signal is to be routed. The RF front end unit (32) is also known as the relay switch board assembly or RSB. Each port of the RF front end is attached to a different RF coil or RF coil combination. Tuning and imaging operations can be conducted for a plurality of coils in succession, without coils having to be detached from the RF front end. The signal routing controller selectively applies the RF signal (from an RF unit) or the tuning signal (from a tuning controller) to the selected coil through a signal path unique to the selected coil. Coils not selected to be operative can be detuned.

MRI front end apparatus and method of operation

A RF choke for use in shielded cable control lines between a RF receive and transmit coil and the control circuitry of a MRI system is disclosed. The RF choke is formed of conductive tubing in the shape of a coil, within which the control signal wires are housed. A capacitor is added in parallel with the conductive tubing coil to complete a resonance circuit acting as a choke to spurious RF currents.

Ground breaker for multiple control lines

A matching circuit for a RF coil on an MRI device is disclosed. The matching circuit includes a variable neutralizing inductance on the output side of the matching circuit ground breaker. All variable components are removed from the coil trace board, providing greater access to the tuning components during the MRI operation.

Parasitic compensating matching circuit integral with ground breaker for

A four-post MRI system used in conjunction with a X-wing transmission coil is disclosed in which the post of the system and the upper and lower gradient coil assemblies are covered in a RF reflective material. The covering may be in applied foil such as copper or aluminum, or may be a screen of conductive metal, or may be a spray-on conductive metal.

RF shield for four-post vertical field magnet used for MRI

An RF front end unit (32) for a magnetic resonance imaging (MRI) system (20) has transmit and receive channels to which a plurality of coils (22) can remain attached during operation (including RF coils having differing types of matching circuits), and facilitates switching between a plurality of attached coils. Methods and apparatus are additionally provided for selectively tuning differing RF coils, including both high power coils (22B, 22C) and varactor-tuned coils (22D). The tuning of a high power coil involves using a remote impedance match tuning network (RTU) (26) for a coarse tuning operation and, if necessary, a fine tuning operation. In performing the coarse tuning operation separately for In-Phase ('I') and Quadrature ('Q') channels, a tuning controller (60) determines the effective load impedance of each of the RF coil channels by quadrature demodulation of their reflected signals. The tuning controller (60) then evaluates a computerized model of the impedance match tuning network in order to determine and set coarse values for the adjustable impedances of the RTU. In tuning varactor coils, the tuning controller chooses a starting point for the varactor coil tune and then executes a two-dimensional bisection search operation to locate a candidate for the tuned point. The bisection search is followed by a starburst operation for examining the magnitude of reflected signals at points in a starburst or asterisk pattern about the candidate point.

Method and apparatus for tuning MRI RF coils

A front end unit (32) for a magnetic resonance imaging (MRI) system (20) comprises a plurality of coil attachment ports (46) to which an RF signal or tuning signal is selectively routed thereby permitting, during operation, coils (22) to remain attached to each of the plurality of ports. A signal routing controller (28, 30) selects to which of the ports the RF signal or tuning signal is to be routed. The RF front end Knit (32) is also known as the relay switchboard assembly or RSB. Each port of the RF front end is attached to a different RF coil or RF coil combination. Tuning and imaging operations can be conducted for a plurality of coils in succession, without coils having to be detached from the RF front end. The signal routing controller selectively applies the RF signal (from an RF unit) or the tuning signal (from a tuning controller) to the selected coil through a signal path unique to the selected coil. Coils not selected to be operative can be detuned.

A local frequency generator employing a single crystal oscillator, latches and direct digital synthesizer circuits digitally produces all signals needed in the transmitter channel of a MRI system to generate MRI transmitter RF pulses. The local frequency generator is operable in both the single side band and double side band modes and has the capability of switching between the modes. The generator is constructed with a phase resetting capability for providing the plural output frequencies needed for making plural MRI slices.

MRI multi-frequency DSB and SSB RF synthesizer

An RF coil sub-assembly for a transverse magnet MRI system includes substantially co-planar serially-connected turns mounted on a common substrate. Preferably, half of the turns are directed clockwise, while the other half are directed counter clockwise to produce a plurality of equal commonly directed currents along spaced apart parallel conductors. A low-loss expanded dielectric spacer is used to mount the RF coils within a pre-existing depression formed by the annular magnetic shims of a transverse magnet structure thus substantially eliminating any obstruction to the image volume for at least the RF transmit coils.

RF coil providing reduced obstruction access to image volume in

A very small sized and highly efficient RF ground breaker for use in magnetic resonance imaging (MRI) is constructed on a printed circuit board. A variable capacitor is used to tune the ground breaker to block the desired radio frequency signals from passing along the outside of a coaxial cable conductor. Preferably, the printed circuit board is double-sided with the ground breaker components being mounted on both sides and with RF conductors being mounted within recesses and serving to interconnect printed circuit traces from one side of the circuit board with those on the other side. In a double ground breaker version, undesirable coupling between proximate RF ground breaker components associated with separate channels are purposely intercoupled by capacitance designed to substantially cancel unwanted inter-channel coupling effects.

Growing community of inventors

Hillsborough, CA, United States of America

Mitsuaki A Arakawa