Method for eliminating motional artifacts in magnetic resonance imaging
First Claim
1. Magnetic resonance imaging method for obtaining an image of an object laid in a space in which a static magnetic field is applied, the method comprising the steps of:
- A) sequentially measuring a plurality of magnetic resonance views with a plurality of encodings by repeating a measurement sequence including substeps of;
a) exciting nuclear spins in said object,b) applying a phase-encoding field gradient along a first direction with programmed time integral to encode the excited spins, andc) detecting the encoded spins in the presence of a readout field gradient along a second direction to generate a magnetic resonance view,wherein measurements of magnetic resonance views with at least low-order encodings are obtained during the repetition of the measurement sequence;
B) subjecting respective magnetic resonance views to a first Fourier transformation so as to generate a plurality of projection views with a plurality of encodings forming a data matrix of a hybrid domain;
C) correcting displacements in respective projection views due to motion of the object using displacement information obtained from projection views with low-order encodings so as to generate a corrected data matrix in the hybrid domain for generating the image of the object based on the corrected projection views including low-order encodings; and
D) subjecting the corrected data matrix to a second Fourier transformation so as to generate the image of the object.
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Abstract
A magnetic resonance imaging method for obtaining an image of an object laid in a space in which a static magnetic field is applied, so as to substantially eliminate motional artifacts. The method includes sequentially measuring a plurality of magnetic resonance views with a plurality of encodings by repeating a measurement sequence of exciting nuclear spins in said object, applying a phase-encoding field gradient along a first direction with programmed time integral to encode the excited spins, and detecting the encoded spins in the presence of a readout field gradient along a second direction to generate a magnetic resonance view so that measurements of magnetic resonance views with at least low-order encoding are obtained during the repetition of the measurement sequence. Thereafter respective magnetic resonance views are subjected to a first Fourier transformation so as to generate a plurality of projection views with a plurality of encodings forming a data matrix in a hybrid domain, displacements in respective projection views due to motion of the object are corrected using displacement information obtained from projection views with low-order encodings so as to generate a corrected data matrix in the hybrid domain, and the corrected data matrix is subjected to a second Fourier transformation so as to generate the image of the object.
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Citations
19 Claims
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1. Magnetic resonance imaging method for obtaining an image of an object laid in a space in which a static magnetic field is applied, the method comprising the steps of:
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A) sequentially measuring a plurality of magnetic resonance views with a plurality of encodings by repeating a measurement sequence including substeps of; a) exciting nuclear spins in said object, b) applying a phase-encoding field gradient along a first direction with programmed time integral to encode the excited spins, and c) detecting the encoded spins in the presence of a readout field gradient along a second direction to generate a magnetic resonance view, wherein measurements of magnetic resonance views with at least low-order encodings are obtained during the repetition of the measurement sequence; B) subjecting respective magnetic resonance views to a first Fourier transformation so as to generate a plurality of projection views with a plurality of encodings forming a data matrix of a hybrid domain; C) correcting displacements in respective projection views due to motion of the object using displacement information obtained from projection views with low-order encodings so as to generate a corrected data matrix in the hybrid domain for generating the image of the object based on the corrected projection views including low-order encodings; and D) subjecting the corrected data matrix to a second Fourier transformation so as to generate the image of the object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. Magnetic resonance imaging method for obtaining an image of an object laid in a space in which a static magnetic field is applied, the method comprising the steps of:
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A) sequentially measuring a plurality of magnetic resonance views with a plurality of encodings by repeating a measurement sequence including substeps of; a) exiting nuclear spins in said object, b) applying a phase-encoding field gradient along a first direction with time integral to encode the excited spins, and c) detecting the encoded spins in the presence of a readout field gradient along a second direction to generate a magnetic resonance view, wherein measurements of extra magnetic resonance views with zero or around zero encoding are obtained between measurements of high-order magnetic resonance views; B) subjecting respective magnetic resonance views and extra magnetic resonance views to a first Fourier transformation so as to generate projection views with a plurality of encodings including the extra magnetic resonance views; C) detecting displacements in low-order projection views and in the projection views of extra magnetic resonance views caused due to motion of the object; D) estimating displacements in high-order projection views by using detected displacements in low-order projections and in projection views of extra magnetic resonance views; E) correcting detected and estimated displacements in respective projection views so as to form a data matrix of corrected projection views; and F) subjecting the data matrix to a second Fourier transformation so as to generate the image of the object.
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19. Magnetic resonance imaging method for obtaining an image of an object laid in a space in which a static magnetic field is applied, the method comprising the steps of:
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a) exciting nuclear spins in said object, b) applying a phase-encoding field gradient along a first direction with changeable time integral to encode the excited spins with a phase-encoding amount, c) detecting the encoded spins in the presence of a readout field gradient along a second direction, d) deriving a projection view from the detected spins, e) detecting displacement of the object from the derived projection view when the projection view is a low-order projection view, and f) repeating steps a) to e) while changing the phase-encoding amount to obtain a plurality of projection views with a plurality of encodings, wherein the phase-encoding amount for each repetition time is selected in accordance with an estimated displacement of the object at a repetition time which is estimated by using previously detected and previously estimated displacement data.
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Specification