Magnetic resonance imaging apparatus and magnetic resonance imaging data processing method

1. A magnetic resonance imaging apparatus comprising:

a phase difference calculation unit configured to perform a one-dimensional Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal data collected during a dynamic EPI NMR image scanning process which also collects a complete set of image data including phase-encoded image data, and to determine a phase difference with respect to time based on a one-dimensional Fourier transform of only the extracted complex non-phase-encoded data not obtained in a pre-scanning process; and

a correction unit configured to correct said complete set of image data for non-uniformity of a static magnetic field caused by the dynamic scanning, based upon said determined phase difference.

2. A magnetic resonance imaging apparatus according to claim 1 , wherein the correction unit is configured to indirectly correct for non-uniformity of the static magnetic field.

3. A magnetic resonance imaging apparatus according to claim 1 , wherein the correction unit is configured to directly correct for non-uniformity of the static magnetic field.

4. A magnetic resonance imaging apparatus comprising:

a phase difference calculation unit configured to perform a one-dimensional Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal data collected during dynamic EPI NMR image scanning which also collects a complete set of image data including phase-encoded data, and to determine a phase difference with respect to time based on a one-dimensional Fourier transform of only the complex non-phase-encoded data not obtained in a pre-scanning process; and

an image position shift unit configured to correct said complete set of image data for image position based upon said determined phase difference.

5. A magnetic resonance imaging apparatus according to claim 4 , wherein the image position shift unit is configured to correct for image position by determining a frequency shift amount based on said determined phase difference and a phase shift of the complex data.

6. A magnetic resonance imaging apparatus according to claim 4 , further including a representative phase difference calculation unit configured to perform a weighted addition depending upon signal intensities, of pixels in a read-out direction.

7. A magnetic resonance imaging apparatus according to claim 4 , further including a phase difference correction value calculation unit configured to perform a correction process for an error based on a phase difference caused by sensitivity variations between surface coils of a phased array coil used as an MRI RF coil.

8. A magnetic resonance imaging apparatus according to claim 4 , further including a phase difference smoothing unit configured to perform a smoothing process based on said determined phase difference by use of a running mean value.

9. A magnetic resonance imaging apparatus according to claim 4 , further including a phase difference smoothing unit performing an error correction process by excluding a value based on said determined phase difference being outside a preset threshold, and performing a smoothing process based on the phase difference by use of a running mean value.

10. A magnetic resonance imaging apparatus according to claim 4 , further including a slice-directional-error processing unit configured to perform an error correction process by detecting as an abnormal value a value exceeding a predetermined limit value based on a phase difference associated with each slice and replacing the abnormal value with a value obtained based on a normal phase difference expected for that slice.

11. A magnetic resonance imaging apparatus according to claim 4 , further including a slice-common phase difference calculation unit for summing up weighted values based on the phase differences of slices depending upon slice signal intensities.

12. A magnetic resonance imaging apparatus according to claim 4 , further including a frequency shift alert unit for providing alert information to an output device when the value based on the determined phase difference exceeds a preset threshold.

13. A magnetic resonance imaging apparatus according to claim 4 , wherein the non-phase-encoded complex data is provided as complex NMR image data used for imaging and located in k-space to include a k-space center.

14. A magnetic resonance imaging apparatus according to claim 4 , further including a resonant frequency correction unit for determining a frequency shift amount based on the phase difference and frequency shift of an RF signal to be transmitted from the RF coil.

15. A magnetic resonance imaging apparatus comprising:

a phase difference calculation unit configured to perform a one-dimensional Fourier transform on non-phase-encoded complex data extracted from nuclear magnetic resonant signal data collected during dynamic EPI NMR image scanning which also collects a complete set of image data including phase-encoded image data, and determining a phase difference for said complete set of image data with respect to time based on a one-dimensional Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

a resonant frequency correction unit for determining a frequency shift based on the phase difference and frequency shift of an RF signal to be transmitted from an MRI RF coil.

16. A magnetic resonance imaging apparatus according to claim 15 , further including a representative phase difference calculation unit configured to perform a weighted addition, depending upon signal intensities, of pixels in a read out direction.

17. A magnetic resonance imaging apparatus according to claim 15 , further including a phase difference correction value calculation unit configured to perform an error correction process based on the phase difference caused by sensitivity variations between surface coils of a phased array coil used as an MRI RF coil.

18. A magnetic resonance imaging apparatus according to claim 15 , further including a phase difference smoothing unit configured to perform a smoothing process based on the phase difference by use of a running mean value.

19. A magnetic resonance imaging apparatus according to claim 15 , further including a phase difference smoothing unit performing an error correction process by excluding a value based on the phase difference being outside a preset threshold, and performing a smoothing process based on the phase difference by use of a running mean value.

20. A magnetic resonance imaging apparatus according to claim 15 , further including a slice-directional-error processing unit configured to perform an error correction process by detecting an abnormal value based on a phase difference associated with each slice beyond a predetermined limit and replacing the abnormal value with a value obtained based on a normal phase difference expected for that slice.

21. A magnetic resonance imaging apparatus according to claim 15 , further including a slice-common phase difference calculation unit for summing up weighted values based on the slice phase differences by weighting depending upon slice signal intensities.

22. A magnetic resonance imaging apparatus according to claim 15 , further including a frequency shift alert unit for providing alert information to an output device when the phase difference value exceeds a preset threshold.

23. A magnetic resonance imaging apparatus according to claim 15 , wherein the non-phase-encoded complex data is provided as complex NMR image data for use in MR imaging and including complex image data located at a k-space center.

24. A magnetic resonance imaging data processing method comprising:

performing a one-dimensional Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal data collected during dynamic EPI NMR image scanning which also collects a complete set of image data including phase-encoded image data;

determining a phase difference with respect to time based on a one-dimensional Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

correcting said complete set of image data for non-uniformity of static magnetic field, based upon the determined phase difference.

25. A magnetic resonance imaging data processing method comprising:

performing a one-dimensional Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal data collected during dynamic EPI scanning which also collects a complete set of image data including phase-encoded image data;

determining a phase difference with respect to time based on a one-dimensional Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

correcting said complete set of image data for image position based upon the determined phase difference.

26. A magnetic resonance imaging data processing method comprising:

performing a one-dimensional Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal data collected during dynamic EPI scanning which also collects a complete set of image data including phase-encoded image data;

determining a phase difference with respect to time based on a one-dimensional Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process;

determining a frequency shift based on the determined phase difference;

determining an RF frequency correction amount of an RF signal to be transmitted from an RF coil depending upon the determined frequency shift; and

correcting sequence information for said complete set of image data based upon a determined RF frequency correction amount.

27. A magnetic resonance imaging apparatus comprising:

a phase difference calculation unit configured to perform a one-dimensional Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal data collected during dynamic scanning according to an echo planar imaging (EPI) sequence which also collects a complete set of image data including phase-encoded image data, and to determine a phase difference with respect to time based on a one-dimensional Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

a correction unit configured to correct said complete set of image data for non-uniformity of static magnetic field caused by dynamic scanning, based upon the determined phase difference.

28. A magnetic resonance imaging apparatus comprising:

a phase difference calculation unit configured to perform a one-dimensional Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal data collected during dynamic scanning according to an echo planar imaging sequence which also collects a complete set of image data including phase-encoded image data, and to determine a phase difference with respect to time based on a one-dimensional Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

an image position shift unit configured to correct said complete set of image data for image position based upon the determined phase difference.

29. A magnetic resonance imaging apparatus comprising:

a phase difference calculation unit configured to perform a one-dimensional Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal data collected during dynamic scanning according to an echo planar imaging sequence which also collects a complete set of image data including phase-encoded image data, and to determine a phase difference for said complete set of image data with respect to time based on a one-dimensional Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

a resonant frequency correction unit for determining a frequency shift amount based on the determined phase difference and shifting an RF signal frequency to be transmitted from an RF coil.

30. A magnetic resonance imaging data processing method comprising:

performing a one-dimensional Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal data collected during dynamic scanning according to an echo planar imaging sequence which also collects a complete set of image data including phase-encoded image data;

determining a phase difference with respect to time based on a one-dimensional Fourier transform of only complex non-phase-encoded data not obtained in a pre-scanning process; and

correcting said complete set of image data for non-uniformity of static magnetic field caused by dynamic scanning, based upon the determined phase difference.

31. A magnetic resonance imaging data processing method comprising:

performing a one-dimensional Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal data collected during dynamic scanning according to an echo planar imaging sequence which also collects a complete set of image data including phase-encoded image data;

determining a phase difference with respect to time based on a one-dimensional Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

correcting said complete set of image data for image position based upon the determined phase difference.

32. A magnetic resonance imaging data processing method comprising:

performing a one-dimensional Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal data collected during dynamic scanning according to an echo planar imaging sequence which also collects a complete set of image data including phase-encoded image data;

determining a phase difference with respect to time based on a one-dimensional Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process;

determining a frequency shift amount based on the determined phase difference;

determining a correction for an RF signal frequency to be transmitted from the RF coil depending upon a determined frequency shift amount; and

correcting sequence information for said complete set of image data based upon a determined RF signal frequency correction amount.

33. A magnetic resonance imaging apparatus comprising:

a phase difference calculation unit configured to perform a Fourier transform on non-phase-encoded complex data extracted from complex nuclear resonant signal image data collected during an EPI dynamic scan which also collects a complete set of image data including phase-encoded image data and to determine a phase difference with respect to time for said complete set of image data based on a Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

a correction unit configured to correct said complete set of image data for non-uniformity of static magnetic field depending upon the determined phase difference.

34. A magnetic resonance imaging apparatus comprising:

a phase difference calculation unit configured to perform a Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal image data collected during an EPI dynamic scan which also collects a complete set of image data including phase-encoded image data and to determine a phase difference for said complete set of image data with respect to time based on a Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

an image position shift unit configured to correct said complete set of image data for image position depending upon the determined phase difference.

35. A magnetic resonance imaging apparatus comprising:

a phase difference calculation unit configured to perform a Fourier transform on non-phase-encoded complex data extracted from complex nuclear resonant signal image data collected during an EPI dynamic scan which also collects a complete set of image data including phase-encoded image data and to determine a phase difference for said complete set of image data with respect to time based on a Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

a resonant frequency correction unit for determining a frequency shift amount for said complete set of image data based on the determined phase difference and shifting an RF signal frequency to be transmitted from an RF coil.

36. A magnetic resonance imaging data processing method comprising:

performing a Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal image data collected during an EPI dynamic scan which also collects a complete set of image data including phase-encoded image data;

determining a phase difference with respect to time for said complete set of image data based on a Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

correcting said complete set of image data for non-uniformity of static magnetic field depending upon the determined phase difference.

37. A magnetic resonance imaging data processing method comprising:

performing a Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal image data collected during an EPI dynamic scan which also collects a complete set of image data including phase-encoded image data;

determining a phase difference for said complete set of image data with respect to time based on a Fourier transform of only the non-phase-encoded complex data not obtained in a pre-scanning process; and

correcting said complete set of image data for image position based upon the determined phase difference.

38. A magnetic resonance imaging data processing method comprising:

performing a Fourier transform on non-phase-encoded complex data extracted from complex nuclear magnetic resonant signal image data collected during an EPI dynamic scan which also collects a complete set of image data including phase-encoded image data;

determining a phase difference with respect to time for said complete set of image data based on a Fourier transform of only the non-phase encoded complex data not obtained in a pre-scanning process;

determining a frequency shift amount based on the determined phase difference;

determining a correction for an RF signal frequency to be transmitted from an RF coil depending upon a determined frequency shift amount; and

correcting sequence information for said complete set of image data based upon a determined frequency RF signal frequency correction.