Magnetic resonance-based method and system for determination of oxygen saturation in flowing blood

Patent metadata

Field	Value
Publication number	US-9310451-B2
Application number	US-201113576676-A
Country	US
Kind code	B2
Filing date	Apr 15, 2011
Priority date	Apr 16, 2010
Publication date	Apr 12, 2016
Grant date	Apr 12, 2016

Abstract

A method and system for determination of oxygen saturation in blood flowing in a vessel using magnetic resonance (MR). An MR image sequence is acquired with different echo time (TE) encoding, and different Fourier velocity encoding (FVE). A Fourier transformation is applied along the velocity dimension to determine a velocity distribution of tissue signals in each voxel of the image sequence. Tissue signals indicative of moving tissues are separated from tissue signals indicative of static tissue, based on the velocity distribution. Oxygen saturation in blood may then be determined using only the tissue signals indicative of flowing blood.

First claim

The invention claimed is:

1. A method for measuring oxygen saturation in blood flowing in a vessel using magnetic resonance (MR), the method comprising:
obtaining by at least one processor non-transitory signals representing an MR image sequence of the vessel from an MR acquisition device, the MR image sequence including a plurality of image data sets with different echo time (TE) encoding, and different Fourier velocity encoding (FVE), the FVE being obtained using different bipolar gradients having different amplitudes to encode respective different velocities for each TE, the FVE defining a velocity dimension in the MR image sequence;
for each TE, applying by the at least one processor a Fourier transformation along the velocity dimension to measure a velocity distribution of non-transitory tissue signals in each voxel of the MR image sequence;
measuring by the at least one processor non-transitory tissue signals indicative of flowing blood apart from non-transitory tissue signals indicative of static tissue, based on the velocity distribution; and

determining measuring by the at least one processor oxygen saturation in blood using only the non-transitory tissue signals indicative of flowing blood;
outputting by the at least one processor non-transitory signals representative of the measured oxygen saturation to make available to a user or a device.

2. The method of claim 1 further comprising:
a display device for displaying the non-transitory signals representative of the measured oxygen saturation to the user.

3. The method of claim 1 wherein each bipolar gradient is aligned with the direction of flow, perpendicular to an imaging plane.

4. The method of claim 1 wherein, for acquisition of each image data, the respective bipolar gradient are applied immediately after a spectral-spatial RF pulse and induces a velocity-dependent phase shift in proton spins.

5. The method of claim 1 wherein measuring oxygen saturation in blood comprises measuring T2 decay based on the non-transitory tissue signals indicative of flowing blood only.

6. The method of claim 1 wherein the non-transitory tissue signals indicative of flowing blood is measured based on a velocity distribution having a range of non-zero velocities and the non-transitory tissue signals indicative of static tissue is measured based on a velocity distribution having a peak at zero velocity.

7. The method of claim 1 further comprising measuring, using at least one of the velocity distribution and the oxygen saturation, one of: a mean flow rate, a mean oxygen flux, and a mean velocity over time.

8. The method of claim 1 further comprising applying a plurality of pulse sequences including TE and FVE for acquiring the MR image sequence.

9. A system for measuring oxygen saturation in blood flowing in a vessel using magnetic resonance (MR), the system comprising:
an MR acquisition device for acquiring non-transitory signals representing an MR image sequence of the vessel, the MR image sequence including a plurality of image data sets with different echo time (TE) encoding, and different Fourier velocity encoding (FVE), the FVE being obtained using different bipolar gradients having different amplitudes to encode respective different velocities for each TE, the FVE defining a velocity dimension in the MR image sequence;
at least one processor for executing instructions configured to:
receive the non-transitory signals from the MR acquisition device;
for each TE, apply a Fourier transformation along the velocity dimension to measure a velocity distribution of non-transitory tissue signals in each voxel of the MR image sequence;
measure non-transitory tissue signals indicative of flowing blood apart from non-transitory tissue signals indicative of static tissue, based on the velocity distribution;
measure oxygen saturation in blood using only the non-transitory tissue signals indicative of flowing blood; and
output non-transitory signals representative of the measured oxygen saturation to make available to a user or a device.

10. The system of claim 9 further comprising a display device for displaying to the user at least one of: the velocity distribution, the measured non-transitory tissue signals indicative of flowing blood, and the measured oxygen saturation in blood.

11. The system of claim 10 wherein the MR image acquisition device is configured to apply a plurality of pulse sequences including TE and FVE for acquiring the MR image sequence.

12. The system of claim 10 wherein the MR image acquisition device is configured to align each bipolar gradient with the direction of flow, perpendicular to an imaging plane.

13. The system of claim 10 wherein the MR image acquisition device is configured to apply the bipolar gradient immediately after a spectral-spatial RF pulse, and wherein the bipolar gradient induces a velocity-dependent phase shift in proton spins.

14. The system of claim 9 wherein measuring oxygen saturation in blood comprises measuring T2 decay based on the tissue signals indicative of flowing blood only.

15. The system of claim 9 wherein the tissue signals indicative of flowing blood is measured based on a velocity distribution having a range of non-zero velocities and the non-transitory tissue signals indicative of static tissue is measured based on a velocity distribution having a peak at zero velocity.

16. The system of claim 9 wherein the at least one processor is configured to further execute instructions to cause the system to measure, using at least one of the velocity distribution and the oxygen saturation, one of: a mean flow rate, a mean oxygen flux, and a mean velocity over time.

17. A non-transient computer readable medium for storing program instructions that, when executed by at least one processor causes the at least one processor to perform a method for measuring oxygen saturation in blood flowing in a vessel using magnetic resonance (MR), comprising:
obtaining non-transitory signals representing an MR image sequence of the vessel from an MR acquisition device, the MR image sequence including a plurality of image data sets with different echo time (TE) encoding, and different Fourier velocity encoding (FVE), the FVE being obtained using different bipolar gradients having different amplitudes to encode respective different velocities for each TE, the FVE defining a velocity dimension in the MR image sequence;
for each TE, applying a Fourier transformation along the velocity dimension to measure a velocity distribution of non-transitory tissue signals in each voxel of the MR image sequence;
measuring non-transitory tissue signals indicative of flowing blood apart from non-transitory tissue signals indicative of static tissue, based on the velocity distribution;
measuring oxygen saturation in blood using only the non-transitory tissue signals indicative of flowing blood; and
making available non-transitory signals representative of the measured oxygen saturation.

18. The non-transient computer readable medium of claim 16 further comprising program instructions that, when executed by at least one processor, causes the at least one processor to perform the method further comprising:
outputting the non-transitory signals representative of the measured oxygen saturation for display on a display device.

19. The non-transient computer readable medium of claim 16 wherein each bipolar gradient is aligned with the direction of flow, perpendicular to an imaging plane.

20. The non-transient computer readable medium

Assignees

• Wernik Christopher
• Swaminathan Venkat
• Wright Graham
• Macgowan Christopher
• Hospital For Sick Children
• Sunnybrook Health Sciences Ct

Inventors

• Wernik Christopher
• Swaminathan Venkat
• Wright Graham
• Macgowan Christopher

Classifications

• A61B5/1128

  using image analysis (A61B5/1127 takes precedence) · CPC title

• G01R33/56509

  due to motion, displacement or flow, e.g. gradient moment nulling (G01R33/567 takes precedence) · CPC title

• G01R33/483 Primary

  with selection of signals or spectra from particular regions of the volume, e.g. in vivo spectroscopy · CPC title

• G01R33/50

  based on the determination of relaxation times {, e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences} · CPC title

• G01R33/28

  Details of apparatus provided for in groups G01R33/44 - G01R33/64 · CPC title