Commissariat &#xc0; L'&#xc9;nergie Atomique Et Aux &#xc9;nergies Alternatives

Inria Institut National De Recherche En Informatique Et En Automatique

Alexis Amadon

Nicolas Boulant

Vincent Gras

Michel Luong

Alexandre Vignaud

Bertrand Thirion

Bruno Pinho-meneses

Raphaël Tomi-Tricot

Martijn Cloos

A method of designing/manufacturing a static-magnetic-field shimming coil system for magnetic resonance imaging, includes determining an optimal stream function, defined on a reference surface enclosing a region of interest, for each member of a cohort of magnetic resonance imaging subjects; performing a Principal Component Analysis of the stream functions; determining at least one coil wiring pattern defined on the reference surface by discretizing at least a most significant principal component of the stream functions. A static-magnetic-field shimming coil system suitable to be obtained by the method at least one hollow dielectric support element having a cavity containing the region of interest and a surface having a shape corresponding to the reference surface or, where appropriate, one the additional surface; and a set of conducting elements deposed on or affixed to the surface of the dielectric support, forming the or one the coil wiring pattern.

Static-magnetic-field shimming coil system for magnetic resonance imaging

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

A computer-implemented method of building a database of pulse sequences for parallel-transmission magnetic resonance imaging, includes a) for each of a plurality of subjects, determining an optimal sequence for the subject; b) for each subject, computing the values of the or of a different cost or merit function obtained by playing the optimal sequences for all the subjects; c) aggregating the subjects into a plurality of clusters using a clustering algorithm taking the values, or functions thereof, as metrics; d) for each cluster, determining an averaged optimal sequence for the cluster; e) receiving, as input, a set of features characterizing an imaging subject, comprising at least a morphological feature of the subject; f) associating the subject to one pulse sequence of the database based on the set of features using the computer-implemented classifier algorithm; and g) performing magnetic resonance imaging using the pulse sequence. A magnetic resonance imaging apparatus for carrying out steps e)-g) of such a method is also provided.

Computer-implemented method of building a database of pulse sequences for magnetic resonance imaging, and a method of performing magnetic resonance imaging using such a database

A method of exciting nuclear spins in a body, the method comprising the steps of: (a) immerging said body (PB) in a static magnetic field (B) for aligning nuclear spins along a magnetization axis (z), said static magnetic field being substantially uniform over at least a volume of interest (VOI) of said body; (b) exposing said body, or at least said volume of interest, to a time-varying magnetic field gradient having components (G, G, G) directed along at least three non-coplanar directions (x, y, z) and to a transverse radio-frequency field (B), whereby said time-varying magnetic field gradient defines a three-dimensional trajectory in k-space constituted by segments linking discrete points (k-k), and said transverse radio-frequency field deposits radio-frequency energy along at least part of said trajectory for flipping said nuclear spins by a same predetermined flip angle, independently from their position within said volume of interest. A method of performing magnetic resonance imaging comprising a step of exciting nuclear spins in a body to be imaged, characterized in that said step is performed by carrying out a method. A magnetic resonance imaging scanner for carrying out such a method.

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Gif sur Yvette, France

Alexis Amadon