Method and apparatus for accelerated magnetic resonance imaging

1. A method for magnetic resonance (MR) imaging, comprising:

operating an MR scanner, while an examination subject is situated therein, to execute an MR data acquisition sequence wherein MR data are acquired from an examination region of the examination subject with a plurality of different MR contrasts at respectively different points in time, and entering the MR data for each MR contrast at k-space points in an electronic memory, representing k-space;

in said MR data acquisition sequence, operating the MR scanner to prepare nuclear spins in the examination region prior to each acquisition of MR data for each of said MR contrasts;

in said MR data acquisition sequence, operating the MR scanner to enter the MR data for each MR contrast at respective k-space points so that k-space is undersampled according to a respective undersampling scheme, with each undersampling scheme for each of said MR contrasts being different;

from a computer, accessing said MR data from said electronic memory and calculating a result image from the MR data, said result image being comprised of pixels having respective pixel values that indicate a value of a magnetic parameter in said examination region; and

making said result image available in electronic format an output of the computer as a data file.

2. A method as claimed in claim 1 wherein each of said different undersampling schemes has a same acceleration factor along same directions in k-space.

3. A method as claimed in claim 2 wherein said acceleration factor is greater than 4.

4. A method as claimed in claim 2 wherein said acceleration factor is greater than 7.

5. A method as claimed in claim 1 wherein the respective, different undersampling schemes of the magnetic resonance contrasts are shifted with respect to each other to cause MR data acquired for at least one MR contrast to be shifted by a k-space point along a k-space trajectory.

6. A method as claimed in claim 1 wherein said k-space points are arranged along a k-space trajectory, and wherein the respective undersampling schemes for acquisitions of different MR contrasts that are acquired at adjacent points in time are shifted by one k-space point along said k-space trajectory in a k-space direction for which an acceleration factor is greater than one.

7. A method as claimed in claim 1 wherein said k-space points are arranged along a Cartesian k-space trajectory in k-space, and within a distance along said Cartesian k-space trajectory between k-space points for which said MR data are acquired according to a respective undersampling scheme is constant and corresponds to an acceleration factor for the respective undersampling scheme.

8. A method as claimed in claim 1 comprising reconstructing each pixel of said result image using a parallel imaging technique.

9. A method as claimed in claim 1 comprising calculating each pixel of the result image using an interconnected optimization.

10. A method as claimed in claim 1 comprising calculating said result image by, for each pixel, determining said magnetic parameter as a pixel value by adapting a signal model to at least one of respective MR data of the different MR contrasts or to reconstructed data obtained with a parallel imaging technique.

11. A method as claimed in claim 10 comprising calculating each pixel of the result image using an interconnected optimization.

12. A method as claimed in claim 1 comprising preparing said nuclear spins by operating said MR scanner in said MR data acquisition sequence to radiate a radio-frequency inversion pulse, and selecting said magnetic parameter from the group consisting of T1 relaxation time, T2 relaxation time, saturation magnetization, and flip angle.

13. A method as claimed in claim 1 comprising preparing said magnetization of nuclear spins by operating said MR scanner in said MR data acquisition sequence to radiate a radio-frequency excitation pulse, and wherein said magnetic parameter is a fraction of a spin species in said examination region.

14. A method as claimed in claim 13 comprising selecting said spin species from the group consisting of fat and water.

15. A method as claimed in claim 13 comprising determining said magnetic parameter for a plurality of pixels in said result image by performing a phase unwrapping for phase correction of the respective pixel, with said phase unwrapping accounting for a non-linear optimization of said plurality of pixels in said result image that are adjacent to the respective pixel.

16. A magnetic resonance (MR) apparatus comprising:

an MR scanner;

an electronic memory;

a control computer configured to operate the MR scanner, while an examination subject is situated therein, to execute an MR data acquisition sequence wherein MR data are acquired from an examination region of the examination subject with a plurality of different MR contrasts at respectively different points in time, and entering the MR data for each MR contrast at k-space points in said electronic memory, representing k-space;

said control computer being configured to operate the MR scanner in said MR data acquisition sequence to prepare nuclear spins in the examination region prior to each acquisition of MR data for each of said MR contrasts;

said control computer being configured to operate the MR scanner in said MR data acquisition sequence to enter the MR data for each MR contrast at respective k-space points so that k-space is undersampled according to a respective undersampling scheme, with each undersampling scheme for each of said MR contrasts being different;

a computer configured to access said MR data from said electronic memory and to calculate a result image from the MR data, said result image being comprised of pixels having respective pixel values that indicate a value of a magnetic parameter in said examination region; and

said computer being configured to make said result image available in electronic format an output of the computer as a data file.

17. A magnetic resonance (MR) apparatus comprising:

an MR scanner;

an electronic memory;

a control computer configured to operate the MR scanner, while an examination subject is situated therein, to execute an MR data acquisition sequence wherein MR data are acquired from an examination region of the examination subject with a plurality of different MR contrasts at respectively different points in time, and entering the MR data for each MR contrast at k-space points in said electronic memory representing k-space;

said control computer being configured to operate the MR scanner in said MR data acquisition sequence to prepare nuclear spins in the examination region prior to each acquisition of MR data for each of said MR contrasts;

said control computer being configured to operate the MR scanner in said MR data acquisition sequence to enter the MR data for each MR contrast at respective k-space points so that k-space is undersampled according to a respective undersampling scheme, with each undersampling scheme for each of said MR contrasts being different;

a computer configured to access said MR data from said electronic memory and to calculate a result image from the MR data using a parallel imaging technique for each pixel of the result image, said result image then being comprised of pixels having respective pixel values that indicate a value of a magnetic parameter in said examination region;

said computer being configured to calculate each pixel of the result image using an interconnected optimization and by, for each pixel, determining said magnetic parameter as a pixel value by adapting a signal model to at least one of respective MR data of the different MR contrasts or to reconstructed data obtained with a parallel imaging technique; and

said computer being configured to make said result image available in electronic format an output of the computer as a data file.