Interleaved single magnetic resonance sequence for MR quantification

• US 9,041,393 B2
• Filed: 07/24/2009
• Issued: 05/26/2015
• Est. Priority Date: 07/24/2009
• Status: Active Grant

• Current Assignee: SyntheticMR AB
• Original Assignee: SyntheticMR AB
• Inventors: Warntjes, Marcel
• Primary Examiner(s): Koval, Melissa
• Assistant Examiner(s): FETZNER, TIFFANY A
• Application Number:
  US12/509,022
• Publication Number:
  US 20110018537A1
• Time in Patent Office: 2,132 Days
• Field of Search: 324300-322, 382128-131, 600407-435
• US Class Current: 324/309
• CPC Class Codes: G01R 33/50 based on the determination of relaxation times , e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences
• CPC Class Codes: G01R 33/5602 by filtering or weighting based on different relaxation times within the sample, e.g. T1 weighting using an inversion pulse
• CPC Class Codes: G01R 33/5615 Echo train techniques involving acquiring plural, differently encoded, echo signals after one RF excitation, e.g. using gradient refocusing in echo planar imaging [EPI], RF refocusing in rapid acquisition with relaxation enhancement [RARE] or using both RF and gradient refocusing in gradient and spin echo imaging [GRASE]
• CPC Class Codes: G01R 33/5616 using gradient refocusing, e.g. EPI
• CPC Class Codes: G01R 33/5617 using RF refocusing, e.g. RARE

Abstract

A magnetic resonance sequence includes an interleaved slice-selective pre-pulse and a slice-selective multi-echo acquisition. This sequence is repeated with different delays between the pre-pulse and the acquisition resulting in a matrix of complex images. Based on this matrix T1 and T2 relaxations, proton density and the B1 field can be estimated. These quantified parameters enable synthetic magnetic resonance imaging (MRI) and form a robust input for tissue segmentation in computer aided diagnosis for MRI.

Claims

1. A method of processing a set of a number of x magnetic resonance (MR) slices, into a displayable form comprising:

in a pre-pulse-only stage, using only one slice-selective pre-pulse, wherein the one slice-selective pre-pulse in the pre-pulse-only stage is used in order to saturate or invert a spin magnetization of a single first slice n within the set of the number of x MR slices; and

in an acquisition stage, using a slice-selective, multi-echo acquisition of a second slice m within the set of the number of x MR slices, the single second slice m being different from the single first slice n;

wherein each of the pre-pulse-only and acquisition stages are interleaved, in a computer as part of an MR sequence, wherein n and m are integers in a range of 1 . . . x, and the MR sequence is repeated, in order to account for the set number of the x MR slices,

whereby a delay between the pre-pulse only processing stage and the acquisition stage of each particular slice is varied and an echo time of each particular slice is varied,

resulting in a plurality of displayable MR images with different respective image contrasts, varying echo times, and varying delays from the processed set number of x MR slices.

2. The method of claim 1, wherein the pre-pulse has a flip angle e is within the range of 90-180 degrees where 90 degrees corresponds to a saturation pre-pulse and 180 degrees corresponds to an inversion pre-pulse.

3. The method of claim 1, wherein the acquisition corresponds to a multi-echo spin echo acquisition including refocusing pulses which occur between the echo read-outs.

4. The method of claim 1, wherein the acquisition corresponds to a multi-echo gradient echo acquisition without refocusing pulses occurring between the echo read-outs.

5. The method of claim 1, wherein each echo read-out generates a single k-space line in k-space.

6. The method of claim 1, wherein each echo read-out generates multiple k-space lines in k-space using an Echo-Planar Imaging (EPI) technique.

7. The method of claim 1, further comprising generating a matrix of MR images with size a×

b having a variation of a echo times and having a variation of b delay times which occur after the pre-pulse only processing stage.

8. The method of claim 7, wherein an increasing image intensity of the matrix of MR images is viewable as a function of delay time after the pre-pulse only processing stage is used to determine a T1 relaxation of each MR image pixel in the imaged object.

9. The method of claim 7, wherein a decreasing image intensity of the matrix of MR images is viewable as a function of echo time, when echo time is used in order to determine a T2 relaxation of each MR image pixel in the imaged object.

10. The method of claim 7, wherein the ratio between the lowest and highest MR image intensity is found as a function of delay time after the pre-pulse only processing stage is used in order, to estimate a B1 field of each image pixel in the imaged object.

11. The method of claim 7, wherein a proton density of each image pixel in an imaged object is estimated by correcting an MR image intensity with respect to the T1, T2 and B1 effects.

12. An imaging system configured for generating displayable magnetic resonance imaging (MRI) images using a magnetic resonance (MR) sequence on a set of a number of x slices, wherein the MR sequence includes:

at least two interleaved processing stages, the MR sequence itself comprising;

a pre-pulse-only processing stage including only one slice-selective pre-pulse, the only one slice-selective pre-pulse being used in order to saturate or invert a spin magnetization of a single first slice n within the set of the number of x MR slices, and

an acquisition processing stage including a slice-selective, multi-echo acquisition of a single second slice m within the set of the number of x MR slices, the single second slice m being different from the single first slice n;

where both n and m are integers in the range of 1 . . . x, and the imaging system is configured to repeat the MR sequence, in order to account for the set number of the x MR slices, where a delay between the pre-pulse only processing stage and the acquisition stage of each particular slice is varied, and an echo time of each particular slice is also varied, resulting in a plurality of displayable MR images being generated by the imaging system with different respective image contrasts, varying echo times, and varying delays.

13. The imaging system of claim 12, wherein the system is configured to generate a pre-pulse having a flip angle e is within the range of 90-180 degrees, where 90 degrees corresponds to a saturation pre-pulse and 180 degrees corresponds to an inversion pre-pulse.

14. The imaging system of claim 12, wherein the system is configured to let the acquisition correspond to a multi-echo spin echo acquisition including refocusing pulses which occur between the echo read-outs.

15. The imaging system of claim 12, wherein the system is configured to let the acquisition correspond to a multi-echo gradient echo acquisition without refocusing pulses occurring between the echo read-outs.

16. The imaging system of claim 12, wherein the system is configured to let each echo read-out generate a single k-space line in k-space.

17. The imaging system of claim 12, wherein the system is configured to let each echo read-out generate multiple k-space lines in k-space using the Echo-Planar Imaging (EPI) technique.

18. The imaging system of claim 12, further comprising a module configured for generating a matrix of MR images with size a×

b having a variation of a echo times and having a variation of b delay times which occur after the pre-pulse only processing stage.

19. The imaging system of claim 18, further comprising a module configured for determining a T1 relaxation of each image pixel in an imaged object, based on an increasing image intensity of the matrix of MR images as a function of delay time, after the pre-pulse only processing stage occurs.

20. The imaging system of claim 18, further comprising a module configured for determining a T2 relaxation of each MR image pixel, based on a decreasing image intensity of the matrix of MR images as a function of echo time.

21. The imaging system of claim 18, further comprising a module configured for determining a B1 field of each image pixel in the imaged object, based on the ratio between the lowest and highest image intensity present, as a function of delay time, after the pre-pulse only processing stage occurs.

22. The imaging system of claim 18, further comprising a module configured for determining a proton density of each image pixel in an imaged object is estimated by correcting an image intensity with respect to the T1, T2 and B1 effects.

23. A non-transitory computer readable medium that when executed by a computer processor of a magnetic resonance imaging system causes the computer processor to initiate executing computer program segments configured for processing a set of a number of x magnetic resonance (MR) slices into a displayable form, wherein the processing comprises,

in a pre-pulse-only stage:

, using only one slice-selective pre-pulse, wherein the one slice-selective pre-pulse, in the pre-pulse-only stage, is used in order to saturate or invert a spin magnetization of a single first slice n within the set of the number of x MR slices; and

in an acquisition stage, using a slice-selective, multi-echo acquisition of a single second slice m within the set of the number of x MR slices with the single second slice m being different from the single first slice n;

the pre-pulse-only processing stage and acquisition stage are interleaved in an MR sequence, and n and m are integers in a range of 1 . . . x;

the MR sequence is repeated, in order to account for the set number of the x MR slices, where a delay occurring between the pre-pulse only processing stage and the acquisition stage of each particular MR slice is varied, and an echo time of each particular slice is also varied, resulting in the formation of a plurality of displayable MR images with different respective image contrasts, varying echo times, and varying delays from the processed set number of x MR slices.