Abstract: An inspection system including a radio frequency (RF) subsystem and a quadrupole resonance (QR) tube array coil. The RF subsystem may include a variable frequency RF source to provide RF excitation signals at a frequency generally corresponding to predetermined, characteristic QR frequencies of a specimen. The QR tube array coil may be implemented using a plurality of conductive tubes defining a cavity of predetermined volume. Typically, the plurality of conductive tubes are spaced at a distance relative to one another to form at least two non-conductive gaps between tubes in the array. After RF excitation signals are applied to the specimen within the cavity, the QR tube array coil may generate a QR output signal responsive to QR signals generated by the specimen.

Abstract: 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 (“sandwiched”) between the two separated solenoidal sections of the first coil in a region where the combined opposing magnetic fields cancel to become a null.

Abstract: 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 (“sandwiched”) between the two separated solenoidal sections of the first coil in a region where the combined opposing magnetic fields cancel to become a null.

Abstract: 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 (“sandwiched”) between the two separated solenoidal sections of the first coil in a region where the combined opposing magnetic fields cancel to become a null.

Abstract: 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 B0 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.

Abstract: 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 (“sandwiched”) between the two separated solenoidal sections of the first coil in a region where the combined opposing magnetic fields cancel to become a null.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: In addition to the usual winding of an MRI RF receive coil, a second, opposite sense, winding is connected to the same pair of RF output terminals and linked to at least part of the same space as the first winding. One or more serially connected RF switches in the second winding selectively connect it in circuit only during transmission of NMR RF nutation pulses. Under these conditions, any transmitted RF fields linked to the first winding are also linked to the second winding. Accordingly, any induced RF currents flowing in the receive coil windings produce self-cancelling effects in the tissue being imaged (thereby reducing possible distortion of the desired transmit fields being used for NMR nutation purposes).