Magnetic resonance system and method to generate a magnetic resonance image of an examination subject

1. A method to generate a magnetic resonance (MR) image of an examination subject, comprising:

providing a processor with information representing a spatial sensitivity of a receiver coil element of a receiver coil array, comprising a plurality of receiver coil elements, in an MR data acquisition scanner that will be used to acquire MR data from an examination subject, from which MR data an MR image of the examination subject will be generated;

in said processor, automatically generating a mask for each receiver coil element of said receiver coil array dependent on said spatial sensitivity of that respective receiver coil element, in order to mask a region of said MR image using said mask, said region being a region of said MR image in which that respective receiver coil element has at least one predetermined sensitivity;

from said processor, operating said MR data acquisition scanner to generate at least one RF excitation pulse and at least one magnetic field gradient in order to acquire said MR data from the examination subject with each receiver coil element of said receiver coil array;

in said processor, generating, for each receiver coil element, a preliminary MR image using only the MR data acquired with that respective receiver coil element;

in said processor, applying, for each receiver coil element, said mask to the preliminary MR image for that respective receiver coil element in order to generate an MR image for that respective receiver coil element; and

in said processor, generating said MR image of the examination subject by assembling said MR images generated for the respective receiver coil elements, and making said MR image available as a data file at an output of said processor.

2. A method as claimed in claim 1 comprising generating said mask by:

in said processor, generating, for each receiver coil element a special MR image from only said MR data acquired by that respective receiver coil element, said special MR image being comprised of pixels each having a respective pixel value; and

generating said mask for that respective receiver coil element dependent on a maximum pixel value in said special MR image for that respective receiver coil element.

3. A method as claimed in claim 2 wherein each preliminary MR image is also comprised of a plurality of pixels, each having a respective pixel value, and wherein said method comprises, for each receiver coil element:

in said processor, generating a threshold pixel value as a predetermined percentage of said maximum pixel value;

in said processor, generating a pixel value curve by interpolating respective pixel values of the pixels of said special MR image; and

in said processor, generating a mask value for each pixel of said preliminary MR image by assigning said mask value for a respective pixel a first value when, according to said pixel value curve, the pixel value of the respective pixel of the preliminary MR image is below said threshold pixel value, and otherwise assigning said mask value for the respective pixel of said preliminary MR image a second value, that is different from said first value.

4. A method as claimed in claim 3 comprising enlarging each mask for each respective receiver coil element with a dilation procedure comprising:

for each respective pixel in said preliminary MR image, determining (a) whether said mask has said second value as a mask value and (b) whether a pixel adjacent to the respective pixel has said second mask value; and

if either (a) or (b) is determined to exist, assigning the mask said second value for the respective pixel.

5. A method as claimed in claim 3 comprising lowpass filtering each mask to smooth discontinuous transitions between said first and second values.

6. A method as claimed in claim 2 comprising generating said special MR image by operating said MR data acquisition scanner with a gradient echo sequence with Cartesian scanning of k-space.

7. A method as claimed in claim 2 comprising generating said special MR image with a resolution of a maximum of 64 pixels per 0.5 m of length of the examination subject.

8. A method as claimed in claim 1 comprising generating each mask for each respective receiver coil element by:

in said processor, generating a special MR image from only said MR data acquired by that respective receiver coil element, said special MR image being comprised of pixels each having a respective pixel value;

determining a frequency distribution that, for all respective pixel values of the special MR image, indicates a frequency at which each pixel value of the special MR image occurs; and

in said processor, generating each mask dependent on said frequency distribution in the respective special MR image for that respective receiver coil element.

9. A method as claimed in claim 8 wherein each preliminary MR image is also comprised of pixels each having a respective pixel value, and comprising:

in said processor, determining the two highest relative maxima of said frequency distribution;

in said processor, determining a threshold pixel value that is between respective pixel values of the two pixels corresponding to said two highest relative maxima of said frequency distribution; and

in said processor, generating a mask value for each pixel of said preliminary MR image by assigning said mask value for a respective pixel a first value when, according to said pixel value curve, the pixel value of the respective pixel of the preliminary MR image is below said threshold pixel value, and otherwise assigning said mask value for the respective pixel of said preliminary MR image a second value, that is different from said first value.

10. A method as claimed in claim 9 comprising enlarging each mask with a dilation procedure comprising:

for each respective pixel in said preliminary MR image, determining (a) whether said mask has said second value as a mask value and (b) whether a pixel adjacent to the respective pixel has said second mask value; and

if either (a) or (b) is determined to exist, assigning the mask said second value for the respective pixel.

11. A method as claimed in claim 9 comprising lowpass filtering each mask to smooth discontinuous transitions between said first and second values.

12. A method as claimed in claim 8 comprising generating said special MR image by operating said MR data acquisition scanner with a gradient echo sequence with Cartesian scanning of k-space.

13. A method as claimed in claim 8 comprising generating said special MR image with a resolution of a maximum of 64 pixels per 0.5 m of length of the examination subject.

14. A method as claimed in claim 2 wherein said preliminary MR image is also comprised of a plurality of pixels, each having a respective pixel value, and wherein said method comprises, for each receiver coil element:

in said processor, generating a threshold pixel value as a predetermined percentage of said maximum pixel value;

in said processor, determining a p-quantile of the pixel values of said special MR image wherein p*100 percent of the pixels of the special MR image have a lower pixel value than a pixel value of said p-quantile, wherein p is a shortfall proportion of said p-quantile; and

in said processor, generating said mask dependent on said p-quantile.

15. A method as claimed in claim 14 wherein said preliminary MR image is also comprised of a plurality of pixels, each having a respective pixel value, and wherein said method comprises, for each receiver coil element:

in said processor, generating a mask value for each pixel of said preliminary MR image by assigning said mask value for a respective pixel a first value when, according to said pixel value curve, the pixel value of the respective pixel of the preliminary MR image is below said pixel value of said p-quantile, and otherwise assigning said mask value for the respective pixel of said preliminary MR image a second value, that is different from said first value.

16. A method as claimed in claim 15 comprising enlarging each mask with a dilation procedure comprising:

for each respective pixel in said preliminary MR image, determining (a) whether said mask has said second value as a mask value and (b) whether a pixel adjacent to the respective pixel has said second mask value; and

if either (a) or (b) is determined to exist, assigning the mask said second value for the respective pixel.

17. A method as claimed in claim 14 comprising lowpass filtering each mask to smooth discontinuous transitions between said first and second values.

18. A method as claimed in claim 14 comprising generating said special MR image by operating said MR data acquisition unit with a gradient echo sequence with Cartesian scanning of k-space.

19. A method as claimed in claim 14 comprising generating said special MR image with a resolution of a maximum of 64 pixels per 0.5 m of length of the examination subject.

20. A method as claimed in claim 1 comprising, in said processor, enlarging said mask by implementing a dilation procedure.

21. A magnetic resonance apparatus to generate a magnetic resonance (MR) image of an examination subject, comprising:

an MR data acquisition scanner having a receiver coil array comprising a plurality of receiver coil elements;

a processor provided with information representing a spatial sensitivity of the receiver coil element of the receiver coil array that will be used to acquire MR data from an examination subject, from which MR data an MR image of the examination subject will be generated;

said processor being configured to automatically generate a mask for each receiver coil element dependent on said spatial sensitivity of that respective receiver coil element, in order to mask a region of said MR image using said mask, said region being a region of said MR image in which that respective receiver coil element has at least one predetermined sensitivity;

said processor being configured to operate said MR data acquisition apparatus to generate at least one RF excitation pulse and at least one magnetic field gradient in order to acquire said MR data from the examination subject with said receiver coil elements of said receiver coil array;

said processor being configured to generate a preliminary MR image for each receiver coil element using only the MR data acquired with that respective receiver coil element;

said processor being configured to apply said mask for each receiver coil element to the preliminary MR image for that respective receiver coil element in order to generate an MR image for that respective receiver coil element; and

said processor being configured to generate said MR image of the examination subject by assembling said MR images generated for the respective receiver coil elements, and to make said MR image available as a data file at an output of said processor.

22. A non-transitory, computer-readable data storage medium encoded with programming instructions, said data storage medium being loaded into a computerized processing and control system of a magnetic resonance (MR) apparatus that also comprises an MR data acquisition scanner comprising a receiver coil array comprising a plurality of receiver coil elements, said programming instructions causing said computerized control and processing system to:

receive information representing a spatial sensitivity of each receiver coil element of the MR data acquisition scanner that will be used to acquire MR data from an examination subject, from which MR data an MR image of the examination subject will be generated;

generate a mask for each receiver coil element dependent on said spatial sensitivity of that respective receiver coil element, in order to mask a region of said MR image using said mask, said region being a region of said MR image in which that respective receiver coil element has at least one predetermined sensitivity;

operate said MR data acquisition scanner to generate at least one RF excitation pulse and at least one magnetic field gradient in order to acquire said MR data from the examination subject with said receiver coil elements of the receiver coil array;

generate a preliminary MR image for each receiver coil element using only the MR data acquired with that respective receiver coil element;

apply said mask for each receiver coil element to said preliminary MR image for that respective receiver coil element in order to generate an MR image for that respective receiver coil element; and

generate said MR image of the examination subject by assembling said MR images for the respective receiver coil elements, and make said MR image available as a data file at an output of said control and processing system.