Commissariat a L'energie Atomique Et Aux Energies Alternatives

Commissariat a L'energie Atomique

Centre National De La Recherche Scientifique

Université´ D'aix-Marseille

Michel Luong

Guillaume Ferrand

Eric Giacomini

Alain France

Xavier Hanus

Michel Desmons

Franck Lethimonier

Nicolas Boulant

Alexandre Vignaud

Stefan Enoch

Vincent Gras

Alexis Amadon

Redha Abdeddaim

Gérard Tayeb

Elodie Georget

Edouard Chazel

A method of designing a pulse sequence for parallel-transmission MRI includes a) for each one of a plurality of subjects, estimating a linear adjustment transformation (L), converting amplitude maps of RF fields generated by respective transmit channels of a MRI apparatus into respective standardized maps; and b) determining RF waveforms (P) minimizing a discrepancy between subject-specific distributions of flip-angles of nuclear spin and a target distribution, averaged over said subjects, the subject-specific distributions corresponding to the flip-angle distributions achieved by applying a superposition of RF fields, each having a temporal profile described by one of said RF waveforms and a spatial amplitude distribution described by a respective standardized map determined for the subject. A method and an apparatus for performing parallel-transmission MRI using such a pulse sequence are provided.

Method of designing a pulse sequence for parallel-transmission MRI, and a method of performing parallel-transmission MRI using such a pulse sequence

An antenna array includes a plurality of linear electromagnetic resonators having longitudinal axes oriented parallel to one another and not aligned, and at least one decoupling device arranged between two the linear electromagnetic resonators, wherein the decoupling device comprises a plurality of open-loop electromagnetic resonators that are matched to a frequency located in the bandwidth of the two the adjacent linear electromagnetic resonators, that are electrically insulated and that are arranged in a plurality of planes that are not parallel to a plane containing the longitudinal axes of the two the linear electromagnetic resonators. Nuclear magnetic resonance imaging apparatus comprising such an antenna array is also provided.

Antenna array, in particular for magnetic resonance imaging, comprising linear electromagnetic resonators and at least one decoupling device

A device for measuring the unloaded quality factor of a resonant cavity which has an input port to accept incident power and an output port to measure the dissipated power, wherein the device includes: a transmission line designed to be coupled to the input port of the resonant cavity to be characterized, which has a coupling coefficient &#x3b2;and which is designed to transmit an incident power generated by a power generator; a switch located upstream of the transmission line at a distance from the cavity which is equivalent to (2n+1)&#x3bb;/4, where n is a whole number equal to or greater than zero and &#x3bb;the wavelength of the wave guided by the transmission line, the switch allowing the coupling coefficient &#x3b2;at the input port to the cavity to be modified at the time of the measurement of the unloaded quality factor of the cavity.

Device for measuring the quality factor of a cavity, in particular a superconducting cavity perturbed by resonant electron discharges

A patch resonator for nuclear magnetic resonance device includes a ground plane, a conductive element, a dielectric element positioned between the ground plane and the conductive element, the resonator being able to transmit a circularly polarized radiofrequency signal when the resonator is supplied by a first transmission line connected to the conductive element via a first connection point and able to receive alternatively a radiofrequency signal circularly polarized in the opposite direction when the resonator is connected to a second transmission line via a second connection point, the resonator including a switch mounted in parallel on each transmission line at a distance from the ground plane corresponding to (2n+1)&#x3bb;/4 with n a natural integer, and &#x3bb; the wavelength of the guided wave in the transmission line at the operating frequency of the resonator, the switch making it possible to electrically connect/disconnect the transmission lines from the conductive element.

Circularly polarized transceiver for magnetic resonance imaging

A multiple-channel antenna includes a first loop resonator including a radiating element forming a loop; a second resonator adjacent to the first loop resonator including a radiating element; wherein the radiating element of the first loop resonator has a main surface defined along a first median plane; a secondary surface defined along a second median plane, the secondary surface delimiting an appendix of the radiating element placed facing the second resonator and having an inclination relative to the median plane of the main surface and wherein the second resonator is a linear resonator with a straight radiating element.

High frequency multiple-channel antenna, particularly for a nuclear magnetic resonance imaging device

A method of making a compact control module of a high frequency antenna for a magnetic resonance imaging device including M control elements and N radiating elements, N greater than M, the control module represented by a control matrix {tilde over (P)}, approximately equal to a control matrix P to control the radiating elements, the method including: decomposing the control matrix {tilde over (P)} into a product of two matrices H&#xd7;L; the matrix L with dimensions M&#xd7;M capable of transforming M signals Vtransmitted by M control elements into M signals V, in amplitude and in phase; the matrix H with dimensions N&#xd7;M receiving the M signals Vas inputs; producing the matrix FI with a number of stages less than a number of stages necessary for implementation of the matrix P; and using the matrix L starting from implementation of the matrix H determined during the producing.

Method of producing a compact control module for a high frequency antenna for a nuclear magnetic resonance imaging device

A linear resonator of a high-frequency antenna suitable for emitting a radiofrequency energisation signal and for receiving a radiofrequency relaxation signal, the linear resonator includes a radiating element to emit af radiofrequency energisation signal and receive a radiofrequency relaxation signal. The resonator also includes: a balun circuit including a power-supply line and two coupling lines; a substrate made of a dielectric material, supporting the radiating element which contains the balun circuit; two contact points connecting the balun circuit to the radiating element, the contact points being formed by one of the ends of the coupling lines extending out of the substrate, the distance separating the two contact points being selected so as to ensure the impedance matching of the resonator; and a chip floorplan separating the coupling lines from the radiating element.

Linear resonator of a high-frequency antenna for a nuclear magnetic resonance imaging apparatus

A method for creating a module for controlling a magnetic resonance imaging apparatus antenna, the method including: determining magnetic field distribution mapping B; constructing a matrix {tilde over (B)} from the selection of a plurality of x*m points Bsuch that {tilde over (B)}&#x2212;Bdetermining the singular vectors of the matrix {tilde over (B)} by singular value decomposition; and arranging a coupling means and/or phase-shifting means, forming said control module, such that a signal Sooutputted from the control module is a function of the equation with Sibeing the input signal.

Method for creating a module for controlling a high-frequency antenna for a nuclear magnetic resonance imaging apparatus

A high frequency cavity resonator for nuclear magnetic resonance, including: a set of transmission lines; and a shield surrounding these transmission lines, wherein each of these transmission lines includes a straight bar which is divided into elongated cylindrical segments, these segments being or being made electrically conducting, the bar being provided with thin solid dielectric elements inserted between the segments.

High-frequency resonant cavity for nuclear magnetic resonance, using radio-frequency transmission lines

Transmission line and high frequency cavity resonator using such transmission lines, particularly for Nuclear Magnetic Resonance. This transmission line comprises a straight and segmented () bar, these segments being (or being made) electrically conducting, the bar being provided with dielectric elements () inserted between the segments.

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Sceaux, France

Michel Luong