Three-dimensional phase contrast imaging using interleaved projection data
First Claim
Patent Images
1. A method for producing a magnetic resonance image indicative of spin motion, the steps comprising:
- a) acquiring an NMR signal with an MRI system using a three-dimensional projection reconstruction pulse sequence which includes;
producing an RF excitation field;
producing a motion encoding gradient field GM directed along a motion encoding axis; and
acquiring an NMR signal while producing a readout gradient to sample a three-dimensional k-space volume along a trajectory that extends substantially radially from the center of k-space;
b) producing a first k-space data set by repeating step a) using different readout gradients to sample k-space throughout the three-dimensional k-space volume along different trajectories with substantially uniform spacing between trajectories;
c) producing a second k-space data set by repeating steps a), and b) using a different motion encoding gradient GM;
d) reconstructing a first phase image from the first k-space data set;
e) reconstructing a second phase image from the second k-space data set;
f) producing a velocity image by combining the first and second phase images, in which the initial motion encoding gradient field GM has a first moment +M1 and the second motion encoding gradient field GM has an opposite first moment −
M1 and step f) is performed by subtracting the first and second phase images; and
which includes repeating steps a)-c) a plurality of times using motion encoding gradient fields GM having different valued first moments +M1 and −
M1 for each repeat, producing a corresponding plurality of first k-space data sets and a corresponding plurality of second k-space data sets, and wherein step f) includes subtracting corresponding k-space data sets in said plurality of first and second k-space data sets to form a plurality of subtracted k-space data sets, and performing a one-dimensional Fourier transformation along corresponding locations in the plurality of subtracted k-space data sets to produce velocity bin data sets.
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Abstract
A three dimensional projection reconstruction pulse sequence is employed to acquire velocity encoded NMR data from which an image indicative of spin motion is reconstructed. The velocity encoding is along all three axes and it may include acquisitions at more than one velocity encoding first moment M1. When more than one first moment M1 is acquired, a 1DFT along the velocity encoding axis is performed prior to reconstructing images from the acquired NMR data.
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Citations
11 Claims
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1. A method for producing a magnetic resonance image indicative of spin motion, the steps comprising:
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a) acquiring an NMR signal with an MRI system using a three-dimensional projection reconstruction pulse sequence which includes;
producing an RF excitation field;
producing a motion encoding gradient field GM directed along a motion encoding axis; and
acquiring an NMR signal while producing a readout gradient to sample a three-dimensional k-space volume along a trajectory that extends substantially radially from the center of k-space;
b) producing a first k-space data set by repeating step a) using different readout gradients to sample k-space throughout the three-dimensional k-space volume along different trajectories with substantially uniform spacing between trajectories;
c) producing a second k-space data set by repeating steps a), and b) using a different motion encoding gradient GM;
d) reconstructing a first phase image from the first k-space data set;
e) reconstructing a second phase image from the second k-space data set;
f) producing a velocity image by combining the first and second phase images, in which the initial motion encoding gradient field GM has a first moment +M1 and the second motion encoding gradient field GM has an opposite first moment −
M1 and step f) is performed by subtracting the first and second phase images; and
which includes repeating steps a)-c) a plurality of times using motion encoding gradient fields GM having different valued first moments +M1 and −
M1 for each repeat, producing a corresponding plurality of first k-space data sets and a corresponding plurality of second k-space data sets, and wherein step f) includes subtracting corresponding k-space data sets in said plurality of first and second k-space data sets to form a plurality of subtracted k-space data sets, and performing a one-dimensional Fourier transformation along corresponding locations in the plurality of subtracted k-space data sets to produce velocity bin data sets. - View Dependent Claims (2)
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3. A method for producing images indicative of spin motion at different phases of a cardiac cycle, the steps comprising:
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a) producing a gating signal which indicates the different cardiac phases;
b) acquiring an NMR signal with an MRI system using a three-dimensional projection reconstruction pulse sequence which is performed during each of the indicated cardiac phases by;
producing an RF excitation field;
producing a motion encoding gradient field GM directed along a first motion encoding axis; and
acquiring an NMR signal while producing a readout gradient to sample a three-dimensional k-space volume along a trajectory that extends substantially radially from the center of k-space;
c) producing a first k-space data set for each cardiac phase by repeating step b) using a different readout gradient to sample a three-dimensional k-space volume with substantially uniform spacing between trajectories; and
d) reconstructing a velocity image from each of said first k-space data sets. - View Dependent Claims (4, 5, 6, 7, 8)
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9. A method for producing an image indicative of the velocity of moving spins in a subject, the steps comprising:
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a) acquiring a first k-space data set with a magnetic resonance imaging system which repeatedly performs a three-dimensional projection reconstruction pulse sequence that includes;
a)i) producing an RF excitation field;
a)ii) producing a motion encoding gradient field GM directed long a first motion encoding axis and having a first moment M1 of a first selected value;
a)iii) acquiring an NMR signal while producing a readout gradient to sample a three-dimensional k-space volume along a trajectory that extends sustantially radially from the center of k-space;
a)iv) repeating steps a)i), a)ii) and a)iii) a plurality of times using different readout gradients to sample the three-dimensional k-space volume substantially uniform in all directions from the center of k-space;
b) acquiring a second k-space data set by repeating step a) using a motion encoding gradient field GM directed along a second motion encoding axis which is perpendicular to the first motion encoding axis;
c) reconstructing a first velocity component image from the first k-space data set;
d) reconstructing a second velocity component image from the second k-space data set;
f) acquiring a plurality of first k-space data sets by repeating step a) a corresponding plurality of times, each repeat using a motion encoding gradient field GM having a different value for the first moment M1;
g) acquiring a plurality of second k-space data sets by repeating step b) a corresponding plurality of times, each repeat using a motion encoding gradient field GM having a different value for the first moment M1; and
in whichstep c) includes performing a one-dimensional Fourier transformation along corresponding locations in said plurality of first k-space data sets; and
step d) includes performing a one-dimensional Fourier transformation along corresponding locations in said plurality of second k-space data sets. - View Dependent Claims (10, 11)
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Specification