Varian, Inc.

Varian Associates, Inc.

Other

Diasonics Cardio/imaging, Inc.

Conductus, Inc.

Agilent Technologies, Inc.

Weston A Anderson

Richard Stacy Withers

Wai Ha Wong

Lloyd Douglas Clark

Gerald M Fisher

James Finnigan

James T Arnold

William L Beaver

David H Humber

Gordon R Lavering

John E Richardson

Luiz Felipe Fuks

Kevin A Delin

Vincent Y Kotsubo

Robert E Nast

William W Brey

Coriolan I Frum

Joseph Murphy

Wai H Wong

Atholl Gibson

Alexander Layton Funk

William G Turnbull

Howard Dw Hill

Luis Felipe Fuks

Jack J Duffield

Bruce E Waller

Seiji Unno

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.

RF-switched superconducting resonators and methods of switching thereof

RF electric fields produced by electric potential differences in NMR probe coil windings may penetrate the NMR sample and sample tube causing sensitivity loss and noise in NMR spectroscopy. Counter-wound spiral coils placed on the opposite surfaces of a planar substrate or on two adjacent planar substrates produce electric potentials that minimize the electric field over the sample region, thereby increasing the sensitivity of the NMR probe. Alternatively counter-wound spiral coils placed adjacent to each other on the outer surface of two concentric cylindrical surfaces that surround the NMR sample minimize the electric field over the sample region. The electric potential of the spiral coils is reduced by adjusting a length of at least one coil.

NMR spiral RF probe coil pair with low external electric field

Enhanced nuclear polarization of a magnetic resonance sample provides greater detection sensitivity over conventional NMR spectroscopy due to a method and an apparatus of increasing the detection sensitivity. Molecules capable of forming photo-excited triplet states are combined in a solution with a NMR sample. While in a uniform magnetic field the solution is frozen, optical radiation is applied to produce photo-excited triplet states molecules and a microwave radiation is applied to stimulate transitions of one of the triplet lines producing dynamic polarization of the nuclei in the magnetic resonance sample. The frozen sample is then rapidly melted and a NMR analysis is performed.

Method and apparatus for increasing the detection sensitivity in a high resolution NMR analysis

The disclosure describes a variable capacitor device, which is formed by a linear motor and a variable capacitor having at least one stator electrode and a movable electrode. A piezoelectric transducer of the linear motor is frictionally coupled to the movable electrode. Application of electrical signals to the piezoelectric transducer of the linear motor produces a motion of the surface of the piezoelectric transducer. The frictional coupling between the piezoelectric transducer surface and the movable electrode transmits a fraction of piezoelectric transducer motion to the movable piston electrode thereby changing the capacity of the variable capacitor. The amount and sign of the capacitance change is selectable by the operator through control of the electrical signals applied to the piezoelectric transducer.

Variable capacitor adjustable by linear motor

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.

NMR probe having an inner quadrature detection coil combined with a spiral wound outer coil for irradiation

An insertable wand is used in a multi-nuclear NMR probe enabling the probe to detect and obtain data from various combinations of nuclei. The particular combination of frequencies is determined by various electrical components, and parts within the wand that are designed to cooperate with a tube, to form an adjustable &frac14; wave assembly. The adjustable &frac14; wave assembly component in the wand comprises a metal rod with an adjustable conductive collar and spring contacts such that when inserted into the tube, the rod and the tube to form an adjustable &frac14; wave circuit or a &frac14; wave shorted stub. The tube may form part of the wand or the probe. When the wand is plugged into the probe, the combination of the NMR coil within the probe and the adjustable &frac14; wave shorted stub provides means for the NMR circuit to resonate at two separate frequencies.

Multinuclear wands

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. For the case when the number of cells is greater than the number of shim coils, a least square method is applied utilizing the equation and matrix factors to determine the current values which produce the least errors in the cells.

Method of shim optimization

An NMR sample, frozen in a tube and having achieved a specified higher degree of polarization for an NMR experiment, is rapidly heated and melted before it loses a significant portion of the achieved polarization and still retains 10% or more. The heating may be achieved by passing an electric current, or currents, through a heating wire, or wires, provided to the tube, or by placing the tube inside a furnace provided with an electric radiator. NMR experiments with high sensitivity can be carried out with such a sample still retaining a high level of polarization.

Method and apparatus for rapid heating of NMR samples

A multiple tuned birdcage coil structure has a plurality of birdcage coils arranged coaxially one inside another around a central axis. Each of the birdcage coils has two conductor rings separated along the central axis and a plurality of mutually separated and parallel linearly elongated conductor legs and generates B field which rotates around the central axis by a specified twist angle between the two rings. The twist angles of different ones of these birdcage coils are different by an integral multiple of 360 degrees such that the assembled birdcage coils are mutually inductively transparent. Such a multiple tuned birdcage coil structure may be formed by assembling individually prepared single tuned birdcage coils each having a specified twist angle with a cylindrically shaped insulating bodies in between. A double tuned birdcage coil structure with two birdcage coils may be produced by providing a single printed circuit substrate with metallic sheets laminated on an insulating sheet, etching the metallic sheets to form appropriate patterns, rolling the substrate into a cylindrical form and soldering together appropriate portions of ring-forming parts to form conductor rings directly connected to or capacitively coupled to spirally birdcage legs.

Multiple tuned birdcage coils

Low-temperature (cryogenic) radio-frequency (RF) coils for nuclear magnetic resonance (NMR) applications include composite multi-layered structures including an internal normal metal layer clad on both sides by external high-purity annealed aluminum layers. The magnetic susceptibilities of the internal and external layers are opposite in sign, and the thicknesses of the layers are chosen such that the composite structure has a net magnetic susceptibility equal to that of its surroundings (vacuum or support material). The internal layer can have a higher resistivity and magnetoresistance than the external layers. The use of high-purity, annealed aluminum for the external layers allows relatively high Q-factors for the cryogenic coils.

Clad metal foils for low temperature NMR probe RF coils

An apparatus for tuning and/or matching a RF coil in a NMR probe comprising a first variable capacitor electrically connected to the coil and a first motor capable of coupling to the first variable capacitor. The first motor when coupled to the first capacitor adjusts a capacitance associated with the first capacitor. The first motor is capable of operating in a strong magnetic field and is capable of not disturbing homogeneity of said magnetic field when said motor is not operating. The apparatus may further include a second variable capacitor and a second motor. The first motor is further capable of coupling to the second capacitor for adjusting a capacitance associated with the second capacitor. The second motor moves the first motor between coupling with the first capacitor and coupling with the second capacitor. The mechanism may be employed to manipulate variable inductive loads for tuning and/or matching.

Motor driven tuning and matching of RF coils in an NMR probe

A z-axis magnetic field gradient coil for nuclear magnetic resonance (NMR) spectrometry includes an etched double-sided flexible sheet having via connections running through the sheet. The vias interconnect two conductive patterns formed on opposite sides of the sheet. Each z-axis current lead is adjacent to another z-axis current lead oriented in the opposite direction, such that the z-axis current components of the two patterns cancel each other. The resulting net current component is in the x-y plane, and generates the desired z-axis magnetic field gradient.

Etched z-axis gradient coils for magnetic resonance

The present invention provides apparatus for utilizing planar HTS probe coils in substantially coplanar coil sets, each set comprised of a plurality of coils, two such similar sets being positioned on opposite sides of the sample to form a plurality of coil pairs. The coil pairs may be used for excitation of the sample, for receiving the NMR response signal or for both. A feature of the invention is the ability afforded to adjust the coupling between coil pairs to a minimum value to thereby prevent interaction between coil pairs having simultaneously applied high power signals and weak NMR response signals.

Coplanar RF probe coil arrangement for multifrequency excitation

A method and apparatus which utilizes the hysteritic behavior of type II superconductors for reducing the effective magnetic susceptibility of high temperature superconducting materials used close to the sample region in nuclear magnetic system probes. The method is particularly applicable to receiver coils. Reducing the magnetic susceptibility of superconducting receiver coils enables the improved sensitivity they inherently provide to be realized without loss of resolution resulting from line broadening caused by susceptibility discontinuities of materials near the sample region of the probe.

Magnetic susceptibility control of superconducting materials in nuclear

Net magnetic flux trapped in an NMR high temperature superconducting RF probe coil magnetically coupled with a main excitation DC magnetic field of an NMR device of which the probe is a part is reduced by moving the probe coil relative to the main magnetic field axis. There is a resulting interaction between the moving probe coil and the main excitation DC magnetic field to induce a current in the probe coil. The induced current reduces the net magnetic flux trapped in the probe coil. The probe coil is moved so the induced current is an AC current having an envelope with decreasing amplitude as a function of time. An electromechanical drive, produced by a magnetic field or an electrostatic field or a piezoelectric transducer attached to a substrate carrying the probe coil, provides oscillatory movement of the probe coil.

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Palo Alto, CA, United States of America

Weston A Anderson