An NMR radio-frequency coil is made up of a plurality of conductive segments evenly spaced about the peripheries and interconnecting a pair of conductive end-cap elements. Each conductive segment includes at least one reactive element which may include a variable capacitive or inductive element.

Radio frequency field coil for NMR

Cavity resonator with improved magnetic field uniformity for high frequency operation and reduced dielectric heating in NMR imaging devices

An RF coil suitable for use in imaging systems is provided which coil has a dielectric filled cavity formed by a surrounding conducting enclosure, the conducting enclosure preferably being patterned to form continuous electrical paths around the cavity, each of which paths may be tuned to a selected resonant frequency. The patterning breaks up any currents induced in the coil and shortens path lengths to permit higher frequency, and thus higher field strength operation. The invention also includes improved mechanisms for tuning the resonant frequency of the paths, for selectively detuning the paths, for applying signal to the coil, for shortening the length of the coil and for controlling the field profile of the coil and the delivery of field to the object to the image.

RF coil for imaging system

An electromagnetic shield for an NMR radio frequency coil designed to resonate at a selected Larmor frequency. The shield includes an electrically conductive layer surrounding the coil. This electrically conductive layer has a thickness substantially the same as one skin depth at the selected Larmor frequency. As such, the conductive layer efficiently conducts radio frequency currents at the selected Larmor frequency thereby conducting and containing the radio frequency coils at the selected Larmor frequency within the coil. Simultaneously, an electrically conductive layer, due to its thinness, very inefficiently conducts eddy currents of the type induced by the lower frequency DC gradient current switching transients the gradients are utilized to magnetically localize an image slice or volume. Consequently, the conductive layer simultaneously attenuates low frequency eddy current propagation of the type induced by the switching field gradient currents in the NMR application, and therefore does not substantially shield or effect the gradient fields across the coil.

Radio frequency volume coils for imaging and spectroscopy

An NMR spectroscopy body probe is comprised of at least one surface coil, each coil having at least one turn and positioned adjacent to a first surface of an insulative member; an electric-field-reducing shield is fabricated upon the other surface of the relatively flexible substrate. The shield surface of the probe is to be positioned closest to the sample. A plurality of surface coil-bearing substrates can be stacked, one adjacent to the other with the planes thereof substantially parallel to each other and to the plane of the electric-field shield, and with each individual surface coil being separately tunable to a different nuclei species resonance frequency. Each surface coil can be utilized for both transmission and reception, or can be used for only reception of the re-radiated signal from the sample, with a separate excitation coil being provided with a radius substantially greater than the average radius of the (receiver) surface coil and positioned in the plane of any of the at least one receiving surface coils.

Nmr spectroscopy body probes with at least one surface coil

Apparatus for generating and detecting magnetic field components oscillating at a radio frequency in a direction transverse to a static magnetic field in a nuclear-magnetic-resonance (NMR) system. The apparatus has a plurality of conductive elements spaced from one another and from the axis along which the static magnetic field is directed. The relative amplitudes of alternating currents in the conductive elements are controlled to generate a spatially uniform field. A preferred embodiment uses a standing wave in a coil assembly to control relative current amplitudes, which takes advantage of the current-phase characteristics of such waves. Detection of RF magnetic fields results from an EMF generated in the coil assembly in response to the time-varying magnetic field; the high Q of the coil assembly enhances detection properties.

Robert Charles Gauss

Papers

Distributed phase rf coil

Apparatus for generating or detecting field components in a magnetic resonance system