Interleaved Single Magnetic Resonance Sequence for MR Quantification

• US 20110018537A1
• Filed: 07/24/2009
• Published: 01/27/2011
• Est. Priority Date: 07/24/2009
• Status: Active Grant

• Current Assignee: SyntheticMR AB
• Original Assignee: SyntheticMR AB
• Inventors: Warntjes, Marcel
• Granted Patent: US 9,041,393 B2
• Time in Patent Office: Days
• 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, comprising

in a first phase, using a slice-selective pre-pulse to saturate or invert a spin magnetization of a first slice n;

and

in a second phase, using a slice-selective, multi-echo acquisition of a second slice m;

wherein the first and second phases are interleaved in a sequence, and n and m are integers in a range 1 . . . x.

2. The method of claim 1, wherein the sequence is repeated a number of times where a delay between the pre-pulse and the acquisition on each particular slice is varied.

3. The method of claim 1, wherein the pre-pulse has a flip angle θ

in the range 90-180 degrees where 90 degrees corresponds to a saturation pre-pulse and 180 degrees corresponds to an inversion pre-pulse.

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

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

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

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

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

b with a variation of a echo times and a variation of b delay times after the pre-pulse.

9. The method of claim 8, wherein an increasing image intensity of the matrix of images as a function of delay time after the pre-pulse is used to determine a T1 relaxation for each image pixel of the imaged object.

10. The method of claim 8, wherein a decreasing image intensity of the matrix of images as a function of echo time is used to determine a T2 relaxation for each image pixel of the imaged object.

11. The method of claim 8, wherein the ratio between the lowest and highest image intensity as a function of delay time after the pre-pulse is used to estimate a B1 field for each image pixel of the imaged object.

12. The method of claim 8, wherein a proton density for each image pixel of an imaged object is estimated by correcting an image intensity for the T1, T2 and B1 effects.

13. A system for generating magnetic resonance images (MRI) using a magnetic resonance (MR) sequence on a set of a number of x slices, wherein the sequence includes at least two interleaved phases, the sequence comprising a slice-selective pre-pulse to saturate or invert a spin magnetization of a first slice n, and a slice-selective, multi-echo acquisition of a second slice m, where both n and m are integers in the range 1 . . . x.

14. The system of claim 13, wherein the system is configured to repeat the sequence a number of times where the delay between the pre-pulse and the acquisition on each particular slice is varied.

15. The system of claim 13, wherein the system is configured to generate a pre-pulse having a flip angle θ

in the range 90-180 degrees, where 90 degrees corresponds to a saturation pre-pulse and 180 degrees corresponds to an inversion pre-pulse.

16. The system of claim 13, wherein the system is configured to let the acquisition correspond to a multi-echo spin echo acquisition including refocusing pulses between the echo read-outs.

17. The system of claim 13, wherein the system is configured to let the acquisition correspond to a multi-echo gradient echo acquisition without refocusing pulses between the echo read-outs.

18. The system of claim 13, wherein the system is configured to let each echo read-out generate a single k-space line for k-space.

19. The system of claim 13, wherein the system is configured to let each echo read-out generate multiple k-space lines for k-space using the Echo-Planar Imaging (EPI) technique.

20. The system of claim 13, further comprising a module for generating a matrix of images with size a×

b with a variation of a echo times and a variation of b delay times after the pre-pulse.

21. The system of claim 20, further comprising a module for determining a T1 relaxation for each image pixel of an imaged object based on an increasing image intensity of the matrix of images as a function of delay time after the pre-pulse.

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

23. The system of claim 20, further comprising a module for determining a B1 field for each image pixel of the imaged object based on the ratio between the lowest and highest image intensity as a function of delay time after the pre-pulse.

24. The system of claim 20, further comprising a module for determining a proton density for each image pixel of the imaged object by correcting the image intensity for the T1, T2 and B1 effects.

25. A computer program product comprising computer program segments for processing a set of a number of x magnetic resonance (MR) slices, wherein the processing comprises in a first phase, using a slice-selective pre-pulse to saturate or invert a spin magnetization of a first slice n;

and in a second phase, using a slice-selective, multi-echo acquisition of a second slice m;

the first and second phases are interleaved in a sequence, and n and m are integers in a range 1 . . . x.