Sub voxel resolution magnetic resonance fingerprinting imaging

A non-transitory computer-readable program product comprising machine executable instructions for execution by a processor controlling a magnetic resonance imaging system, wherein execution of the machine executable instructions causes the processor to:

• acquire magnetic resonance fingerprinting (MRF) data by controlling the magnetic resonance imaging system with MRF pulse sequence commands, wherein the MRF pulse sequence commands cause the magnetic resonance imaging system to acquire the MRF data according to a magnetic resonance fingerprinting protocol, wherein the pulse sequence commands are configured for acquiring the MRF data in two dimensional slices, wherein the two dimensional slices have a slice selection direction, wherein the pulse sequence commands comprises a train of pulse sequence repetitions, wherein the train of pulse sequence repetitions comprises a sampling event where the MRF data is repeatedly sampled;
• and
• construct a series at least one magnetic resonance parameter value for each voxel of the two-dimensional slices using the MRF data, wherein each of the series corresponds to the sampling event of each pulse sequence repetition;
• and
• calculate a composition of each of a set of predetermined substances within two or more sub-voxels for each voxel of the two-dimensional slices using a sub-voxel MRF dictionary for each of the two or more sub-voxels and the series of the at least one magnetic resonance parameter value, wherein the sub-voxels divide each voxel in the slice selection direction, wherein the sub-voxel MRF dictionary comprises separate fingerprints calculated by integrating over distinct parts of an excitation pulse profile for each of the two or more sub-voxels, wherein the composition within the two or more sub-voxels is calculated by determining the contribution from each of the two or more sub-voxels using linear optimization;
• and
• wherein any one of the following:
• the excitation pulse profile has a symmetric flip angle distribution and has an anti-symmetric phase distribution,
• the pulse sequence commands specify a radio-frequency pulse, wherein the radio-frequency pulse is asymmetric, and
• combinations thereof.

A method of operating a magnetic resonance imaging system, wherein the method comprises:

• acquiring magnetic resonance fingerprinting (MRF) magnetic resonance data by controlling the magnetic resonance imaging system with MRF pulse sequence commands, wherein the MRF pulse sequence commands cause the magnetic resonance imaging system to acquire the MRF magnetic resonance data according to a magnetic resonance fingerprinting protocol, wherein the pulse sequence commands are configured for acquiring the MRF magnetic resonance data in two dimensional slices, wherein the two dimensional slices have a slice selection direction, wherein the pulse sequence commands comprises a train of pulse sequence repetitions, wherein the train of pulse sequence repetitions comprises a sampling event where the MRF magnetic resonance data is repeatedly sampled;
• and
• constructing a series of at least one magnetic resonance parameter value for each voxel of the two-dimensional slices using the MRF magnetic resonance data, wherein each of the series corresponds to the sampling event of each pulse sequence repetition;
• and
• calculating a composition of each of a set of predetermined substances within two or more sub-voxels for each voxel of the two dimensional slices using a sub-voxel magnetic resonance fingerprinting dictionary for each of the two or more sub-voxels and the series of the at least one magnetic resonance parameter value, wherein sub-voxels divide each voxel in the slice selection direction, wherein the sub-voxel magnetic resonance fingerprinting dictionary comprises separate fingerprints calculated by integrating over distinct parts of an excitation pulse profile for each of the two or more sub-voxels, wherein the composition within the two or more sub-voxels is calculated by determining the contribution from each of the two or more sub-voxels using linear optimization wherein any one of the following:
• the excitation pulse profile has a symmetric flip angle distribution and has an anti-symmetric phase distribution;
• the pulse sequence commands specify a radio-frequency pulse, wherein the radio-frequency pulse is asymmetric;
• and
• combinations thereof.