Magnetic resonance imaging of chemical species with a spectral model

A magnetic resonance imaging apparatus for imaging at least first and second chemical species, the apparatus comprising a magnetic resonance imaging scanner for acquiring magnetic resonance image data, the scanner being operable for:

• acquiring first and second echo data at two different echo times employing a two-point DIXON acquisition resulting in a first acquired complex dataset and a second acquired complex dataset,
• modelling the first acquired complex dataset and second acquired complex dataset by employing a spectral signal model of at least one of the chemical species, said modelling resulting in a first modelled complex dataset and a second modelled complex dataset, said first modelled complex dataset and the second modelled complex dataset having a first phasor and a second phasor and separate signal datasets for the first and second chemical species, the modelling of the first acquired complex data set and the second acquired complex dataset employing a linear combination of the separate first and second acquired complex datasets for the two chemical species multiplied by the first phasor and the second phasor, respectively, weights for the linear combination being derived from the spectral signal model of at least one of the first and second chemical species;
• determining the magnitude of the first and second acquired complex datasets and retrieving an initial estimate of the separate first and second acquired complex datasets for the two chemical species based on the first and second modelled complex datasets;
• deriving from the first and second acquired complex datasets and the initial estimate of the first and second complex datasets for the two chemical species at least one solution for the first and second phasors based on the first and second modelled complex datasets;
• determining from the first and second acquired complex datasets and one solution for the first and second phasors a final estimate of separate first and second signal complex datasets for the two chemical species;
• reconstructing at least one of the separate first and second complex datasets into an image, and
• displaying at least one of the images on a display device.

A magnetic resonance imaging apparatus for generating an image of at least a single chemical species of an object including at least first and second chemical species, the imaging apparatus comprising:

• at least one computer processor configured to:
• using a two-point DIXON acquisition technique, receive first and second echo data generated at two different echo times from a magnetic resonance imaging scanner;
• reconstruct the first and second echo data into first and second acquired image datasets,
• model the first and second acquired image datasets by employing a multi-peak spectral model of at least one of the two chemical species to generate first and second modelled image datasets and first and second phasors for the first and second chemical species, the modelling of the first and second acquired image datasets including linearly combining the first and second acquired image datasets for the two chemical species multiplied by the first and second phasors, weights for the linear combination being derived from the multi-peak spectral model of at least one of the first and second chemical species,
• determine a magnitude of the first and second acquired complex datasets and retrieve an initial estimate of the separate signal datasets for the two chemical species based on the first and second modelled complex datasets,
• derive from the first and second acquired complex datasets and the initial estimate of the separate signal datasets for the two chemical species at least one solution for the first and second phasors based on the first and second modelled complex datasets,
• minimize a residuum between the first and second acquired image datasets and the first and second modelled image datasets to generate a first chemical species image and a second chemical species image;
• a display device configured to display at least one of the first and second species images.

A magnetic resonance imaging apparatus for generating an image of at least a single chemical species of an object including at least first and second chemical species, the imaging apparatus comprising:

• at least one computer processor configured to:
• using a two-point acquisition technique, receive first and second echo data generated at only two different echo times from a magnetic resonance imaging scanner, the first echo data including first echo k-space data and the second echo data including second echo k-space data,
• model the first and second echo k-space data by employing a multi-peak spectral model of at least one of the two chemical species to generate first and second modelled k-space data and first and second phasors for the first and second chemical species, the modelling of the first and second echo k-space data including linearly combining the first and second k-space data multiplied by the first and second phasors, weights for the linear combination being derived from the multi-peak spectral signal model of at least one of the first and second chemical species,
• minimize a residuum between the first and second echo k-space data and the first and second modelled k-space data to generate first chemical species k-space data and a second chemical species k-space data,
• determine a magnitude of the first and second acquired complex datasets and retrieve an initial estimate of the separate signal datasets for the two chemical species based on the first and second modelled complex datasets,
• derive from the first and second acquired complex datasets and the initial estimate of the separate signal datasets for the two chemical species at least one solution for the first and second phasors based on the first and second modelled complex datasets,
• reconstruct at least one of the first and second species k-space data into an image;
• a display device configured to display the at least one image.