Method and device for correcting organ motion artifacts in MRI systems

• US 6,894,494 B2
• Filed: 06/30/2003
• Issued: 05/17/2005
• Est. Priority Date: 11/25/2002
• Status: Expired due to Fees

• Current Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Original Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Inventors: Wrobel, Miroslaw, Dhanantwari, Amar, Freibert, Andreas, Stergiopoulos, Stergios, Younis, Waheed
• Primary Examiner(s): Shrivastav, Brij B.
• Application Number:
  US10/608,141
• Publication Number:
  US 20040102695A1
• Time in Patent Office: 687 Days
• Field of Search: 324/309, 324/307, 324/318, 324/322, 600/410, 600/422, 600/421, 128/653.2
• US Class Current: 324/309
• CPC Class Codes: G01R 33/56325 Cine imaging
• CPC Class Codes: G01R 33/5673 Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker

Abstract

The present invention relates to a signal processing method and system for correcting organ motion artifacts for cardiac and brain imaging. A plurality of sets of MRI measurement data indicative of at least an image of an object is received. Each set corresponds to one row k_x of a k-space matrix of at least a k-space matrix. For each set a k-space matrix of the at least a k-space matrix is determined for allocation thereto based on motion information of the object occurring during acquisition of the plurality of sets of the MRI measurement data. In a following step a location within the allocated k-space matrix corresponding to a row of the k-space matrix allocated thereto is determined for each set. At least a k-space matrix is then generated by re-arranging the plurality of sets. Each of the at least a k-space matrix comprises the sets of the plurality of sets of the MRI measurement data allocated thereto. Inverse Fourier transforming of the plurality of k-space matrices provides at least a reconstructed image. Through careful selection of the phases of the cardiac and respiratory cycles and corresponding ranges MRI data acquisition periods are of the order of seconds or a few minutes. Furthermore, integration of motion artifact free MRI images of different phases of organ motion using the coherent k-space synthesis according to the invention allows provision of an animation showing different phases of a cardiac or lung cycle. In an embodiment for correcting motion artifacts for brain imaging a motion vector describing translational and rotational motion of a patient'"'"'s head is tracked during the MRI data acquisition process. The motion artifacts are then corrected based on coherent k-space synthesis using the motion vector data.

Claims

1. A method for motion correcting MRI measurement data comprising the steps of:

a) receiving a plurality of sets of the MRI measurement data indicative of at least an image of an object, each set corresponding to one row k_x of a k-space matrix of at least a k-space matrix;

b) selecting for each set of the plurality of sets of the MRI measurements a k-space matrix of the at least a k-space matrix for allocation thereto;

c) determining for each set of the plurality of sets of the MRI measurement data a location within the k-space matrix allocated thereto; and

,

d) generating at least a k-space matrix based on the sets of the plurality of sets of the MRI measurement data allocated thereto.

2. A method for motion correcting MRI measurement data as defined in claim 1 comprising the step of:

b1) determining the k-space matrix of the at least a k-space matrix for selection based on motion data indicative of the motion of the object occurring during acquisition of the plurality of sets of the MRI measurement data.

3. A method for motion correcting MRI measurement data as defined in claim 2 wherein the motion is a periodic motion with a period of P_c seconds.

4. A method for motion correcting MRI measurement data as defined in claim 3 wherein step (b1) the k-space matrix is determined in accordance with i=mod(n−

1, P_cƒ

_s)+1 with i indicating the k-space matrix, n indicating the set, and ƒ

_s being the sampling frequency of the MRI data acquisition process in Hz.

5. A method for motion correcting MRI measurement data as defined in claim 4 wherein step (c) the location is determined in accordance with r=mod(n−

1, N)+1 with r indicating the location within the allocated k-space matrix, and N indicating the total number of rows in the allocated k-space matrix.

6. A method for motion correcting MRI measurement data as defined in claim 5 wherein the parameters P_c and ƒ

_s are such that the greatest common divisor of P_cƒ

_s and N is one.

7. A method for motion correcting MRI measurement data as defined in claim 6 wherein N is a radix 2 number and P_cƒ

_s is an odd integer.

8. A method for motion correcting MRI measurement data as defined in claim 7 wherein the steps of (b) and (c) comprise the steps of:

allocating a first set k_x[1] to a 1^st k-space matrix as the first row forming a first element (1,

     1) of a 2D array having P_cƒ

_s rows and N columns;

continuously filling the elements of the 2D array with subsequent sets by increasing each of row number and column number of the 2D array elements by 1 until all elements of the 2D array are filled;

filling an element in the 1^st row of a same column with a subsequent set after filling an element in the P_cƒ

_s^th row; and

,

filling an element in the 1^st column of a same row with a subsequent set after filling an element in the N^th column.

9. A method for motion correcting MRI measurement data as defined in claim 2 wherein the motion comprises two periodic motions.

10. A method for motion correcting MRI measurement data as defined in claim 9 wherein the two periodic motions are cardiac motion and respiratory motion.

11. A method for motion correcting MRI measurement data as defined in claim 10 wherein the period P_c is determined in accordance with $P_c=\frac{n}{f_{\mathrm{ecg}}}=\frac{m}{f_{\mathrm{breath}}}$

with ƒ

_ecg and ƒ

_breath being the cardiac and respiratory frequencies, respectively, and m and n are integers.

12. A method for motion correcting MRI measurement data as defined in claim 11 wherein for a given cardiac frequency ƒ

_ecg the respiratory frequency ƒ

_breath is determined in accordance with $f_{\mathrm{breath}}=\frac{m}{n}<br><br>f_{\mathrm{ecg}}.$

13. A method for motion correcting MRI measurement data as defined in claim 2 comprising the step of:

receiving motion data indicative of a motion signal acquired from the object simultaneously with the plurality of sets of MRI measurements.

14. A method for motion correcting MRI measurement data as defined in claim 13 wherein the motion signal is indicative of cardiac and respiratory motion of the object.

15. A method for motion correcting MRI measurement data as defined in claim 14 wherein the motion signal of cardiac motion is an ECG signal.

16. A method for motion correcting MRI measurement data as defined in claim 14 comprising the steps of:

selecting phases of cardiac and respiratory cycles and determining respective ranges based on the motion data; and

,

selecting sets of the plurality of sets of the MRI measurement data being acquired during the selected phases of cardiac and respiratory cycles and falling within the ranges.

17. A method for motion correcting MRI measurement data as defined in claim 13 wherein the motion of the object is a rigid body motion and wherein the motion signal is indicative of translational and rotational motion of the object.

18. A method for motion correcting MRI measurement data as defined in claim 17 comprising the steps of:

inverse Fourier transforming the at least a k-space matrix producing at least a reconstructed image portion of the at least an image;

transforming the at least a reconstructed image portion for correcting at least one of translational and rotational motion; and

,

superposing the at least a transformed image portion producing the at least an image.

19. A method for motion correcting MRI measurement data as defined in claim 18 comprising the step of processing the at least a transformed image portion to coincide with a grid location of the at least an image.

20. A method according to claim 18 wherein the step of transforming is performed for correcting for both rotational and translational motion.

21. A method for motion correcting MRI measurement data as defined in claim 20 comprising the step of processing the at least a transformed image portion to coincide with a grid location of the at least an image.

22. A method for motion correcting MRI measurement data as defined in claim 1 comprising the step of reconstructing at least an image by inverse Fourier transforming the at least a k-space matrix.

23. A method for motion correcting MRI measurement data as defined in claim 22 wherein the at least an image comprises a sequence of images.

24. A method for motion correcting MRI measurement data comprising the steps of:

receiving a plurality of sets of the MRI measurement data indicative of an image of an object, each set corresponding to one row k_x of a k-space matrix;

receiving cardiac and respiratory signal data, the cardiac and respiratory signal data being acquired simultaneously with the MRI measurement data from the object;

selecting phases of cardiac and respiratory cycles and determining respective ranges based on the cardiac and respiratory signal data;

selecting sets of the plurality of sets of the MRI measurement data being acquired during the selected phases of cardiac and respiratory cycles and falling within the determined ranges;

determining for each selected set of the plurality of sets of the MRI measurement data a location within a k-space matrix corresponding to a row of the k-space matrix allocated thereto;

generating the k-space matrix based on the allocated sets; and

,

reconstructing an image by inverse Fourier transforming the k-space matrix.

25. A method for motion correcting MRI measurement data as defined in claim 24 comprising the step of selecting a different phase of the cardiac and/or respiratory cycles if the k-space matrix is not filled completely.

26. A method for motion correcting MRI measurement data as defined in claim 24 comprising the step of increasing the ranges of the selected phases if the k-space matrix is not filled completely.

27. A method for motion correcting MRI measurement data as defined in claim 24 comprising the step of filling missing elements of the k-space matrix by interpolating between measurements of adjacent elements.

28. A method for motion correcting MRI measurement data as defined in claim 24 wherein the range of the selected phase of the cardiac cycle is determined along time axis.

29. A method for motion correcting MRI measurement data as defined in claim 27 wherein the range of the selected phase of the respiratory cycle is determined along chest volume axis.

30. A method for motion correcting MRI measurement data as defined in claim 24 wherein the exhale phase of the respiratory cycle is selected.

31. A method for motion correcting MRI measurement data as defined in claim 24 wherein the diastole phase of the cardiac cycle is selected.

32. A method for motion correcting MRI measurement data as defined in claim 30 wherein the diastole phase of the cardiac cycle is selected.

33. A system for motion correcting MRI measurement data comprising a storage medium having stored therein executable commands for execution on a processor, the processor when executing the commands performing the steps of:

receiving a plurality of sets of the MRI measurement data indicative of at least an image of an object, each set corresponding to one row k_x of a k-space matrix of at least a k-space matrix;

receiving motion data indicative of a motion signal acquired from the object simultaneously with the plurality of sets of MRI measurements;

selecting each set of the plurality of sets of the MRI measurements a k-space matrix of the at least a k-space matrix for allocation thereto;

determining for each set of the plurality of sets of the MRI measurement data a location within the k-space matrix allocated thereto; and

,

generating at least a k-space matrix based on the sets of the plurality of sets of the MRI measurement data allocated thereto.

34. A system for motion correcting MRI measurement data as defined in claim 33 wherein the storage medium comprises executable commands for execution on a processor, the processor when executing the commands performing the step of determining the k-space matrix of the at least a k-space matrix for selection based on the motion data.

35. A system for motion correcting MRI measurement data as defined in claim 34 comprising:

a first port for receiving the plurality of sets of the MRI measurement data;

a second port for receiving the motion data; and

,

a processor in data communication with the first port, the second port and the storage medium, the processor for executing the executable commands for processing the plurality of sets of the MRI measurement data.

36. A system for motion correcting MRI measurement data as defined in claim 35 wherein the storage medium comprises executable commands for execution on the processor, the processor when executing the commands performing the step of:

reconstructing at least an image by inverse Fourier transforming the at least a k-space matrix.

37. A system for motion correcting MRI measurement data as defined in claim 36 comprising a display in data communication with the processor for displaying the at least an image.

38. A system for motion correcting MRI measurement data as defined in claim 37 comprising a MRI system for acquiring the plurality of sets of MRI measurements from the object and for providing measurement data indicative thereof, the MRI system for being in data communication with the first port.

39. A system for motion correcting MRI measurement data as defined in claim 38 comprising a motion sensing system for acquiring a motion signal from the object and for providing motion data indicative thereof, the motion sensing system for being in data communication with the second port.

40. A system for motion correcting MRI measurement data as defined in claim 39 comprising:

a first sensor for sensing cardiac motion of the object; and

,

a second sensor for sensing respiratory motion of the object.

41. A system for motion correcting MRI measurement data as defined in claim 39 wherein the motion sensing system comprises a sensor for acquiring a motion signal indicative of translational and rotational motion of the object.