Abstract: A transverse volume magnetic resonance (MR) coil includes a cylindrical geometry of electrical conductors configured for generating a B1 field comprising nth mode spatial harmonics along a first transverse axis in a transverse plane orthogonal to a central axis of the coil, while being uniform along a second transverse axis orthogonal to the first transverse axis in the transverse plane, where n is an integer ranging from 1 or greater. The coil may be included with other coils in an array coil. The coil may be utilized to detect geometric echoes resulting from excitation of an MR sample.

Abstract: According to one aspect, a magnetic resonance imaging (MRI) scanner includes a short birdcage (e.g. millipede) distributed-capacitance radio-frequency (RF) coil formed from one or more patterned planar conductive foils. The transverse extent (e.g. diameter) of the coil is at least a factor of 3, for example about a factor of 10, larger than the longitudinal (z-axis) extent of the coil. Flux-return gaps may be provided between the sample measurement volume defined by the coil and RF shields adjacent to the sample measurement volume, to confine the RF magnetic field to the sample measurement volume. Exemplary coils described herein are particularly suited for very high-frequency MRI measurements.

Abstract: A magnetic resonance imaging (MRI) apparatus comprises a plurality of cylindrical electromagnetic coils arranged in a coaxial configuration around a sample region. The coils are used to capture resonance signals from a sample at different times according to a geometric echo effect. The measurements can then be combined to produce an MRI signal.

Abstract: According to one aspect, a magnetic resonance imaging (MRI) scanner includes a short birdcage (e.g. millipede) distributed-capacitance radio-frequency (RF) coil formed from one or more patterned planar conductive foils. The transverse extent (e.g. diameter) of the coil is at least a factor of 3, for example about a factor of 10, larger than the longitudinal (z-axis) extent of the coil. Flux-return gaps may be provided between the sample measurement volume defined by the coil and RF shields adjacent to the sample measurement volume, to confine the RF magnetic field to the sample measurement volume. Exemplary coils described herein are particularly suited for very high-frequency MRI measurements.

Abstract: A low pass RF ladder coil, which is named as a millipede surface coil, comprises a first and a second conductor end strips running parallel to each other. A set of rung elements are placed between them, alternate rung elements are connected to the first and second strip respectively. The number and spacing of the rung elements are sufficient for resonating the coil at the desired imaging frequency. This millipede surface coil may have 100 or more rung elements. Fixed and variable capacitors are provided for separately tuning and matching the first and second mode resonant frequencies, and for coupling and impedance matching the two modes to external circuits. An active detuning is provided that detunes the ladder coil when a separate RF coil is transmitting.

Abstract: A low pass RF ladder coil, which is named as a millipede surface coil, comprises a first and a second conductor end strips running parallel to each other. A set of rung elements are placed between them, alternate rung elements are connected to the first and second strip respectively. The number and spacing of the rung elements are sufficient for resonating the coil at the desired imaging frequency. This millipede surface coil may have 100 or more rung elements. Fixed and variable capacitors are provided for separately tuning and matching the first and second mode resonant frequencies, and for coupling and impedance matching the two modes to external circuits. An active detuning is provided that detunes the ladder coil when a separate RF coil is transmitting.

Abstract: A multimode resonator resonating at two or more frequencies is operated at cryogenic temperatures and composed of a superconducting material or a normal metal with a superconducting section serving as a RF superconducting switch. The multimode resonator is coupled to a NMR spectrometer and a RF switch power source, wherein its one frequency is selected to correspond to the operating frequency of the NMR spectrometer and at least a second frequency is tuned to a frequency of RF switch power source, unrelated to the spectrometer frequency, therefore power at this frequency does not perturb the operation of the spectrometer. When activated, the RF switch power source induces a current sufficient to approach or exceeds the critical current in one or more sections of the superconducting material of the multimode resonator, thereby increasing its resistance and reducing the Q factor of the multimode resonator.

Abstract: A multimode resonator resonating at two or more frequencies is operated at cryogenic temperatures and composed of a superconducting material or a normal metal with a superconducting section serving as a RF superconducting switch. The multimode resonator is coupled to a NMR spectrometer and a RF switch power source, wherein its one frequency is selected to correspond to the operating frequency of the NMR spectrometer and at least a second frequency is tuned to a frequency of RF switch power source, unrelated to the spectrometer frequency, therefore power at this frequency does not perturb the operation of the spectrometer. When activated, the RF switch power source induces a current sufficient to approach or exceeds the critical current in one or more sections of the superconducting material of the multimode resonator, thereby increasing its resistance and reducing the Q factor of the multimode resonator.

Abstract: A switchable birdcage coil functioning as a transmitter coil and a separate RF surface coil functioning as the receiver coil are utilize in NMR and MRI apparatus. To prevent the switchable birdcage coil from absorbing energy by coupling to the receiver coil or by absorbing power from the RF field produced by the precessing nuclear spins, one or more of the reactive elements of the birdcage coil are switched from a normal reactive impedance state to a high impedance state. The high impedance state is formed by switchably combining the reactive element with a complementary reactive element thereby forming parallel resonant high impedance circuit that is tuned to resonate at the NMR frequency.

Abstract: NMR coils are formed from transmission line comprising a tuned LC circuit determined substantially from the distributed capacitance and inductance of the transmission line operated in common mode. Introduction of gaps staggered between opposite conductors of 2-conductor transmission line contribute a desired distributed capacitance with reduced effective inductance to sustain resonant behavior at higher frequency than achievable with conventionally tuned coils and with relaxation of dimensional constraints as the resonant half wavelength approaches coil dimensions.

Abstract: A high resolution NMR probe having two or more resonators, an inner resonator which is closely coupled to a sample and is used to stimulate and receive a response from one nuclear species, and an outer resonator to induce transitions in another nuclear species, wherein the resonators may be provided with cooling capability and may be made of superconducting material, and wherein the inner resonator may be a saddle coil or a birdcage coil with capability of being tuned, and wherein the outer resonator may be one or more spiral wound saddle coil.

Abstract: NMR coils are formed from transmission line comprising a tuned LC circuit determined substantially from the distributed capacitance and inductance of the transmission line operated in common mode. Introduction of gaps staggered between opposite conductors of 2-conductor transmission line contribute a desired distributed capacitance with reduced effective inductance to sustain resonant behavior at higher frequency than achievable with conventionally tuned coils and with relaxation of dimensional constraints as the resonant half wavelength approaches coil dimensions.

Abstract: A multimode RF probe for use with a sample oriented at an angle &thgr; to a polarizing field B0 produces a resultant RF magnetic field exhibiting enhanced coupling to the sample. The multiple modes are furnished by a quadrature coil, or a solenoidal coil in combination with either a saddle coil or quadrature coil.

Abstract: A high resolution NMR probe having two or more resonators, an inner resonator which is closely coupled to a sample and is used to stimulate and receive a response from one nuclear species, and an outer resonator to induce transitions in another nuclear species, wherein the resonators may be provided with cooling capability and may be made of superconducting material, and wherein the inner resonator may be a saddle coil or a birdcage coil with capability of being tuned, and wherein the outer resonator may be one or more spiral wound saddle coil.

Abstract: A method of optimizing effects of a shim system on static magnetic field in an imaging system or liquid spectroscopy system, wherein for each cell of a probe disposed within the magnetic field, the resonant frequency is obtained without any current being supplied to any shim coil, then for each cell, the resonant frequency thereof is obtained by a current being supplied to one shim without any current being supplied to the other shims, and a factor is obtained for each cell due only to the magnetic field produced by current supplied to the one shim, and the resulting difference divided by the current supplied to the shim is obtained for each cell for each separate shim current, from the data an equation is derived relating the field at each cell to the individual shim current. For the case when the number of cells is equal to or less than the number of shim coils, this equation is inverted to give the shim current values to produce the same field at all cells.

Abstract: Superconducting birdcage coil with low-pass and high-pass coil configurations are formed by using strips each with an elongated sapphire substrate with a layer of a high temperature superconductor (HTS) material grown in a wavy pattern over its entire length on one of its main surfaces. A low-pass coil is formed with a pair of ring elements made of an electrically conductive metal and a plurality of such strips arranged parallel to one another and interconnecting these ring elements at junctions which are spaced peripherally along each of the rings. At each of the junctions, the ring element and the HTS layer form a capacitance. A high-pass coil is formed by a plurality of such strips each with electrodes of the HTS material also grown at two end positions separated from each other on the other main surface of its sapphire substrates. These strips are arranged parallel to each other and sequentially around a central axis, each lying in a plane which includes the center axis.

Abstract: A multimode RF probe for use with a sample oriented at an angle &thgr; to a polarizing field B0 produces a resultant RF magnetic field exhibiting enhanced coupling to the sample. The multiple modes are furnished by a quadrature coil, or a solenoidal coil in combination with either a saddle coil or quadrature coil.

Abstract: A birdcage resonator has a pair of conductor rings separated from each other along a central axis and a plural number of axially disposed conductor rungs, which extend between the rings and are evenly spaced around the central axis. Each of the rungs has a sectional shape with thickness or a radial extension comparable to or greater than its width or its azimuthal extension. Measures of the width and thickness of the rungs may be determined by using them as parameters to calculate the values of Q factor from an analytical procedure to locate parameter value ranges corresponding to maximal Q. Geometric calculations for filling factor yield ranges of parameters providing for compromise parameter values. Saddle coils have been found to exhibit similar enhancement of Q with radially oriented conductor cross section.

Abstract: A birdcage resonator has a pair of conductor rings separated from each other along a central axis and a plural number of axially disposed conductor rungs, which extend between the rings and are evenly spaced around the central axis. Each of the rungs has a sectional shape with thickness or a radial extension comparable to or greater than its width or its azimuthal extension. Measures of the width and thickness of the rungs may be determined by using them as parameters to calculate the values of Q factor from an analytical procedure to locate parameter value ranges corresponding to maximal Q. Geometric calculations for filling factor yield ranges of parameters providing for compromise parameter values. Saddle coils have been found to exhibit similar enhancement of Q with radially oriented conductor cross section.

Abstract: A phase-shifted coil comprises nested concentric spiral portions, the terminals of which are progressively offset. Separately tuned concentric such coils of different dimensions exhibit relatively close intercoil clearance in one dimension and relatively large clearances in the orthogonal dimension provide different flux return characteristics for selective RF coupling.