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

Inria Institut National De Recherche En Informatique Et En Automatique

Vincent Gras

Nicolas Boulant

Alexis Amadon

Michel Luong

Alexandre Vignaud

Raphaël Tomi-Tricot

Bertrand Thirion

Franck Mauconduit

A method for determining a global and regular parameterization for a family of spin-excitation pulse sequences in magnetic resonance imaging, with each pulse sequence of the family being a multi-spoke type sequence suitable for selectively exciting nuclear spins in a slice of a volume of interest of a body immersed in a static magnetic field and comprising radiofrequency pulses at a Larmor frequency of the nuclear spins alternated with magnetic gradient pulses. The global parameterization minimizes a function representing a mean deviation from a setpoint of the excitation of the nuclear spins, with the mean being computed for the volume of interest and for all the possible orientations and positions of the slices. It allows a selective excitation sequence to be simply designed for a slice with a random orientation and position.

Method for generating multi-ray spin-excitation sequences and application thereof to 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 designing a pulse sequence for parallel-transmission magnetic resonance imaging comprises: a) acquiring, for each member of a cohort, inhomogeneity maps of radio-frequency fields generated within the member; b) computing, for each member of the cohort, a spatial distribution of flip angles of nuclear spins obtained using the pulse sequences, and c) computing a single cost or merit function representative of a difference between the spatial distributions of flip angles and a target distribution, and iteratively adjusting design parameters of the pulse sequences to optimize the cost or merit function; the steps b) and c) being carried out iteratively using a computer. A method of performing parallel-transmission magnetic resonance imaging on a subject using a pulse sequence designed by such a method is provided.

Method of designing pulse sequences for parallel-transmission magnetic resonance imaging, and a method of performing magnetic resonance imaging using such sequences

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Chevreuse, France

Vincent Gras