Magnetic resonance angiography using undersampled 3D projection imaging

• US 6,487,435 B2
• Filed: 01/23/2001
• Issued: 11/26/2002
• Est. Priority Date: 04/10/1998
• Status: Expired due to Term

• Current Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Original Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Inventors: Barger, Andrew V., Mistretta, Charles A., Block, Walter F.
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): Shah, Devaang
• Application Number:
  US09/767,757
• Publication Number:
  US 20010027262A1
• Time in Patent Office: 672 Days
• Field of Search: 324/307, 324/309, 600/415, 600/420, 600/407, 600/419, 600/410
• US Class Current: 600/420
• CPC Class Codes: G01R 33/281 Means for the use of in vitro contrast agents G01R33/282 takes precedence; involving use of a contrast agent in MR imaging G01R33/5601; in vivo contrast agents A61K49/0002
• CPC Class Codes: G01R 33/4824 using a non-Cartesian trajectory
• CPC Class Codes: G01R 33/54 Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
• CPC Class Codes: G01R 33/561 by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences
• CPC Class Codes: G01R 33/5611 Parallel magnetic resonance imaging, e.g. sensitivity encoding [SENSE], simultaneous acquisition of spatial harmonics [SMASH], unaliasing by Fourier encoding of the overlaps using the temporal dimension [UNFOLD], k-t-broad-use linear acquisition speed-up technique [k-t-BLAST], k-t-SENSE structural details of arrays of sub-coils G01R33/3415
• CPC Class Codes: G01R 33/5619 by temporal sharing of data, e.g. keyhole, block regional interpolation scheme for k-Space [BRISK]
• CPC Class Codes: G01R 33/563 of moving material, e.g. flow contrast angiography

Abstract

A 3D projection reconstruction pulse sequence is employed to acquire CEMRA images. In one application of the invention an undersampled, high resolution abdominal CEMRA image is acquired in a single breathhold. In another application of the invention a series of undersampled image frames are acquired during a CEMRA dynamic study Each image is produced by combining peripheral k-space data from adjacent image frames with the central and peripheral k-space data of an acquired image frame.

Claims

1. A method for producing a magnetic resonance image of a patient using a magnetic resonance imaging (MRI) system, the steps comprising:

a) operating the MRI system to acquire a k-space image data set using a three-dimensional projection reconstruction pulse sequence that is repeated to sample k-space throughout a three-dimensional k-space volume V, and wherein the three-dimensional projection reconstruction pulse sequence is repeated a sufficient number of times to sample in accordance with the Nyquist condition, a central volume of k-space that is substantially smaller than the volume V but not a sufficient number of times to sample a peripheral region of k-space in accordance with the Nyquist condition; and

b) reconstructing an image using substantially the entire, undersampled acquired k-space image data set and

wherein the number of repetitions of the three-dimensional projection reconstruction pulse sequence is substantially less than one-half the number of repetitions necessary to fully sample the entire k-space volume V in accordance with the Nyquist condition.

3. The method as recited in claim 1 in which the resolution of the reconstructed image is isotropic.

4. The method as recited in claim 1 in which the pulse sequence is performed by:

i) producing an rf excitation pulse that produces transverse magnetization in spins located throughout the field of view of the reconstructed image; and

ii) acquiring an NMR signal in the presence of a readout gradient to sample k-space in a trajectory that starts at one point on an outer boundary of the sampled k-space volume, passes through the center of k-space and extends out to another point on the outer boundary of the sampled k-space volume.

5. The method as recited in claim 4 in which the sampling trajectory is a straight line.

6. The method as recited in claim 1 in which the pulse sequence is performed by:

i) producing an rf excitation pulse that produces transverse magnetization in spins located throughout the field of view of the reconstructed image;

ii) acquiring an NMR signal in the presence of a readout gradient to sample k-space in a trajectory that extends from one point on an outer boundary of the k-space volume and extends through the center of k-space; and

the method further includes the step of synthesizing from the k-space samples acquired in step ii) further k-space samples that extend the trajectory to another point on the outer boundary of the k-space volume.

7. The method as recited in claim 1 in which step b) includes performing a filtered back projection image reconstruction using the k-space image data set.

2. A method for producing a magnetic resonance image of a patient using a magnetic resonance imaging (MRI) system, the steps comprising:

a) operating the MRI system to acquire a k-space image data set using a three-dimensional projection reconstruction pulse sequence that is repeated to sample k-space thoughout a k-space volume having a radius R, and wherein the three-dimensional projection reconstruction pulse sequence is repeated a sufficient number of times to sample in accordance with the Nyquist condition, a central region of k-space having a radius r that is substantially smaller than the radius R but not a sufficient number of times to sample a peripheral region of k-space in accordance with the Nyquist condition; and

b) reconstructing an image using substantially the entire, undersampled acquired k-space image data set in which step b) includes;

i) producing a three-dimensional array of k-space data by regridding the acquired k-space data set; and

ii) performing a three-dimensional Fourier transformation on the three-dimensional array of k-space data; and

wherein the number of repetitions of three-dimensional projection reconstruction pulse sequence is substantially less than one-half the number of repetitions necessary to fully sample the entire k-space volume in accordance with the Nyquist condition.

8. A method for producing a magnetic resonance angiogram image of selected vasculature in a patient using a magnetic resonance imaging system (MRI), the steps comprising:

a) injecting the patient with a contrast agent which flows into the selected vasculature;

b) operating the MRI system to perform a three-dimensional projection reconstruction pulse sequence;

c) acquiring an NMR signal produced by spins in the selected vasculature to sample three-dimensional k-space volume along a trajectory that extends substantially radially from the center of k-space;

d) repeating steps b) and c) with a different readout gradient in three-dimensional projection reconstruction pulse sequence to sample the three-dimensional k-space volume along a different trajectory that extends substantially radially from the center of k-space;

e) producing an image data set by repeating step d) to sample k-space throughout a three-dimensional k-space volume with substantially uniform spacing between trajectories and with the spacing between acquired k-space samples from adjacent trajectories at the periphery of the sampled k-space volume being substantially more than twice the spacing necessary to satisfy the Nyquist condition; and

f) reconstructing an image of the selected vasculature using substantially all the k-space samples in the acquired image data set.

10. The method as recited in claim 8 in which the resolution of the reconstructed image is isotropic throughout the selected vasculature.

11. The method as recited in claim 8 which includes:

timing the performance of steps b) through e) such that the acquired NMR signals are enhanced by the arrival of contrast agent in the selected vasculature.

12. The method as recited in claim 8 which includes, repeating steps b) through e) to acquire additional image data sets as the contrast agent flows into the selected vasculature, and step f) includes, combining k-space samples from a plurality of acquired image data sets, and reconstructing said image using the combined k-space samples.

13. The method as recited in claim 12 in which successively acquired image data sets sample different locations in k-space and k-space samples from successive image data sets are combined and used to reconstruct said image.

14. The method as recited in claim 13 in which the k-space samples from one acquired image data set are combined with peripheral region k-space samples from a successively acquired image data set.

15. The method as recited in claim 13 in which image data sets from three different and interleaved locations in k-space are successively and repeatedly acquired, and k-space samples from three successive image data sets are combined and used to reconstruct said image.

18. The method as recited in claim 12 in which the three-dimensional projection reconstruction pulse sequence produces a velocity encoding gradient;

successively acquired image data sets are velocity encoded for spin motion along different axes; and

k-space samples from successively acquired image data sets are combined and used to reconstruct said image.

19. The method as recited in claim 18 in which image data sets with three different velocity encoding directions are successively acquired, and k-space samples from three successive image data sets are combined and used to reconstruct said image.

20. The method as recited in claim 13 in which the radial k-space sampling trajectories of the different image data sets are interleaved.

21. The method as recited in claim 8 in which the k-space sampling trajectories acquired in step c) extend from the center of k-space in substantially opposite directions therefrom and to substantially opposite points on an outer boundary of the sampled k-space volume.

9. A method for producing a magnetic resonance angiogram of selected vasculature in a patient using a magnetic resonance imaging system(MRI) system, the steps comprising:

a) injecting the patient with a contrast agent which flows into the selected vasculature;

b) operating the MRI system to perform a three-dimensional projection reconstruction pulse sequence;

c) acquiring an NMR signal produced by spins in the selected vasculature to sample k-space along a trajectory that extends substantially radially from the center of k-space;

d) repeating steps b) and c) with a different readout gradient in the three-dimensional projection reconstruction pulse sequence to sample k-space along a different trajectory that extends substantially radially from the center of k-space;

e) producing an image data set by repeating step d) to sample k-space throughout a three-dimensional k-space volume with substantially uniform spacing between trajectories and with the spacing between acquired k-space samples from adjacent trajectories at the periphery of the sampled k-space volume being substantially more than twice the spacing necessary to satisfy the Nyquist condition;

f) reconstructing an image of the selected vasculature using substantially all the k-space samples in the acquired image data set; and

in which step f) includes;

i) producing a three-dimensional array of k-space data by regridding the acquired k-space samples; and

ii) performing a three-dimensional Fourier transformation on the three-dimensional array of k-space data.

16. A method for producing a magnetic resonance angiogram of selected vasculature in a patient using a magnetic resonance imaging system (MRI) system, the steps comprising:

a) injecting the patient with a contrast agent which flows into the selected vasculature;

b) operating the MRI system to perform a three-dimensional projection reconstruction pulse sequence;

c) acquiring an NMR signal produced by spins in the selected vasculature to sample k-space along a trajectory that extends substantially radially from the center of k-space;

d) repeating steps b) and c) with a different readout gradient in the three-dimensional projection reconstruction pulse sequence to sample k-space along a different trajectory that extends substantially radially from the center of k-space;

e) producing an image data set by repeating step d) to sample k-space throughout a three-dimensional k-space volume with substantially uniform spacing between trajectories and with the spacing between acquired k-space samples from adjacent trajectories at the periphery of the sampled k-space volume being substantially more than twice the spacing necessary to satisfy the Nyquist condition; and

f) repeating steps b) through e) to acquire additional image data sets as the contrast agent flows into the selected vasculature in which successively acquired image data sets sample from three different and interleaved locations in k-space

g) combining k-space samples from a plurality of acquired image data sets and reconstructing an image using the combined k-space samples; and

in which all the k-space samples from the second of said three successive image data sets are combined with peripheral region k-space samples from the first and the third of said three successive image data sets.

17. The method as recited in claim 16 in which the spacing between k-space samples in a central region of each image data set satisfies the Nyquist condition.

22. A method for producing a magnetic resonance angiogram image of selected vasculature in a patient using a magnetic resonance imaging system (MRI), the steps comprising:

a) injecting the patient with a contrast agent which flows into the selected vasculature;

b) operating the MRI system to perform a three-dimensional projection reconstruction pulse sequence;

c) acquiring an NMR signal produced by spins in the selected vasculature to sample a three-dimensional k-space volume along a trajectory that extends substantially radially from the center of k-space;

d) repeating steps b) and c) a plurality of times with a different readout gradient in the three-dimensional projection reconstruction pulse sequence each repetition to sample a first set of trajectories;

e) repeating steps b) and c) a plurality of time with a different readout gradient in each repetition to sample a second set of trajectories;

f) repeating steps b) and c) a plurality of times with a different readout gradient in each repetition to sample a third set of trajectories;

g) combining sampled k-space data in the second set of trajectories with sampled k-space data from the first and third sets of trajectories that is located in a peripheral region of said three-dimensional k-space volume; and

h) reconstructing an image of the selected vasculature using the combined k-space data.

23. The method as recited in claim 22 which includes performing step e) at an optimal moment when the contrast flows into said selected vasculature.