On-the-fly removal of data inconsistency with k-space oversampling and demodulation in MRI acquisitions
First Claim
1. A method of magnetic resonance imaging comprising:
- (a) subjecting an object being imaged to a plurality of magnetic resonance imaging sequences, each imaging sequence generating a multiple echo echo-train;
(b) phase encoding each echo;
(c) collecting each echo into k-space as a plurality of sampled data points;
(d) generating a navigator echo in conjunction with each of the plurality of imaging sequences;
(e) collecting each navigator echo;
(f) determining an average amplitude of the collected navigator echoes generated in step (d); and
, (g) using the average amplitude of the collected navigator echos to adjust the sampled data points.
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Accused Products
Abstract
A plurality of multiple echo imaging sequences are generated and sampled to fill k-space. Each multiple echo sequence includes a plurality of phase and frequency encoded image data echoes and a navigator echo, preferably at the end of the sequence. The navigator echoes are separated from the image data and analyzed to determine their relative phase angle and amplitude. More specifically to a preferred embodiment, a unit vector whose orientation is indicative of navigator echo phase angle relative to a reference angle is determined for each navigator echo. An amplitude correction value indicative of the amplitude of each navigator echo relative to a reference amplitude, such as an average navigator echo amplitude, is determined. The image date is adjusted with the relative phase angle and amplitude of the navigator echo from the same multiple echo sequence.
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Citations
14 Claims
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1. A method of magnetic resonance imaging comprising:
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(a) subjecting an object being imaged to a plurality of magnetic resonance imaging sequences, each imaging sequence generating a multiple echo echo-train;
(b) phase encoding each echo;
(c) collecting each echo into k-space as a plurality of sampled data points;
(d) generating a navigator echo in conjunction with each of the plurality of imaging sequences;
(e) collecting each navigator echo;
(f) determining an average amplitude of the collected navigator echoes generated in step (d); and
,(g) using the average amplitude of the collected navigator echos to adjust the sampled data points. - View Dependent Claims (2, 3, 4, 5, 6, 7)
(h) applying a multi-dimensional Fourier transformation in k-space to reconstruct an image representation of the object.
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8. A magnetic resonance imaging apparatus comprising:
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MRI pulse sequence producing means which produce a plurality of MRI pulse sequences, each of said MRI pulse sequences inducing an MRI signal from a subject being examined, said MRI signal including (i) an echo-train containing a plurality of magnetic resonance imaging echoes and (ii) a navigator echo which follows its corresponding echo-train;
a reception system that receives the imaging echoes and the navigator echoes, said imaging echoes being loaded into an image data storage device as k-space image data and said navigator echoes being loaded into a navigator echo storage device;
a data correction processor which accesses the navigator echo storage device to determine, from navigator echoes loaded therein, image data correction factors which are used to correct the k-space image data, said image correction factors being based at least partially upon an average amplitude of the navigator echoes; and
,a reconstruction processor that accesses the image data storage device to reconstruct the image data into an image representation, the data correction processor being connected with one of the image data storage device and the reconstruction processor for correcting the image data with the image data correction factors. - View Dependent Claims (9, 10, 11)
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12. A method of magnetic resonance imaging comprising:
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(a) subjecting an object being imaged to a plurality of magnetic resonance imaging sequences, each imaging sequence generating more than one echo;
(b) phase encoding each echo;
(c) coflecting each echo into k-space as sampled data;
(d) generating a navigator echo in conjunction with each of the plurality of imaging sequences;
(e) collecting each navigator echo;
(f) determining a unit vector corresponding to each navigator echo, said unit vector having a vector angle corresponding to a phase angle of the navigator echo;
(g) determining a deviation between an amplitude of each navigator echo and an average amplitude of the navigator echoes generated in step (d);
(h) adjusting a magnitude of each unit vector in accordance with the deviation between its amplitude and the average amplitude; and
,(i) multiplying the data from each imaging sequence by the magnitude adjusted vector corresponding to the navigator echo associated with the sequence.
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13. A method of magnetic resonance imaging, said method comprising:
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(a) subjecting an imaged region of an object being imaged to a plurality of magnetic resonance imaging sequences, each imaging sequence generating a multi-echo echo-train;
(b) phase encoding each echo of the echo-train;
(c) collecting each echo into k-space as a plurality of sampled data;
(d) generating an additional navigator echo in conjunction with each of the plurality of imaging sequences;
(e) collecting each navigator echo; and
,(f) for an ith one of the imaging sequences, adjusting the sampled data by;
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14. A magnetic resonance imaging apparatus comprising:
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MRI pulse sequence producing means which produce a plurality of MRI pulse sequences, each of said MRI pulse sequences inducing an MRI signal from a subject being examined, said MRI signal including (i) an echo-train containing a plurality of magnetic resonance imaging echoes and (ii) a navigator echo;
a reception system that receives the imaging echoes and the navigator echoes, said imaging echoes being loaded into an image data storage device as k-space image data and said navigator echoes being loaded into a navigator echo storage device; and
,a data correction processor which accesses the navigator echo storage device to determine, from navigator echoes loaded therein, image data correction factors which are used to correct the k-space image data, wherein the correction processor;
(a) determines a phase angle of each navigator echo;
(b) an amplitude variance of each navigator echo relative to the amplitudes of the other navigator echoes; and
,(c) corrects the image data in accordance with (i) the determined phase angle and (ii) the determined amplitude variance determined from the navigator echo corresponding to the same echo-train as the corrected image data.
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Specification