Phase contrast imaging using interleaved projection data
AssigneeWisconsin Alumni Research Foundation
InventorsCharles A. Mistretta, Andrew V. Barger
Life of this patent
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Abstract
A magnetic resonance angiogram (MRA) is acquired using a pulse sequence that samples k-space at a projection angle. The acquired NMR signal is sensitized to spin motion with a bipolar motion encoding gradient and the pulse sequence is repeated to sample k-space at a set of different projection angles. A phase image is reconstructed from the acquired NMR signals using a filtered backprojection technique. Additional sets of projections with different motion encoding directions are acquired at interleaved projection angles, and the reconstructed phase images are combined to provide a velocity image.
Claims12
A method for producing a magnetic resonance image indicative of spin motion, the steps comprising:
- a) acquiring a first series of NMR signals with an MRI system using a pulse sequence which produces:
- an RF excitation field that produces transverse magnetization in the spins;
- a first motion encoding a gradient field GM that imparts a phase shift indicative of spin motion in a first direction;
- acquiring an NMR signal in the presence of a readout gradient;
- wherein the direction of the readout gradient is rotated from one pulse sequence to the next such that the acquired first series of NMR signals sample k-space at a corresponding first series of different projeciton angles;
- b) acquiring a second series of NMR signals with the MRI system using a pulse sequence which produces:
- an RF excitation field that produces transverse magnetization in the spins;
- a second motion encoding gradient field GM that imparts a phase shift indicative of spin motion in a second direction;
- acquiring an NMR signal in the presence of a readout gradient;
- wherein the direction of the readout gradient is rotated from one pulse sequence to the next such that the acquired second series of NMR signals sample k-space at a corresponding second series of different projection angles which are different from the first series of projection angles produced in step a);
- c) reconstructing a first velocity image from the first series of NMR signals;
- d) reconstructing a second velocity image from the second series of NMR signals;
- and
- e) combining the two velocity images to produce the image indicative of spin motion.
Dependencies are inferred from the claim text.