Nuclear magnetic resonance flow imaging
First Claim
1. A method of acquiring an NMR signal providing motional information of a sample comprising the steps of:
- (a) applying an r.f. excitation signal to said sample for the subsequent production of an NMR signal;
(b) applying spatial encoding gradient fields to said sample in a pulse sequence in which the gradient pulse train of a gradient in the direction in which motion is to be encoded exhibits a zero value first moment with respect to the timing of an r.f. excitation signal;
(c) applying a motion encoding gradient field to said sample to encode motion in a given direction which is produced in response to a two-pulse gradient pulse sequence which exhibits a zero value zero moment and a non-zero value first moment; and
(d) after the above steps, acquiring NMR signal information.
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Accused Products
Abstract
The effects of particle motion or flow within a sample may be measured by applying a motion-encoding gradient to the sample, along with spatial encoding gradients. The motion-encoding gradient applies two gradient fields of respective opposite sense to the spins of the sample so as to encode motion as a net phase component resulting from the two fields. Two image data sequences, one with motion encoding and one without, may be compared to measure the effects of motion, or a plurality of image data sequences may be taken, each with a different value motion-encoding gradient. A Fourier transformation performed on the sequence data in the latter case with respect to the variation in the motion-encoding gradient pulses will yield a plurality of images, each representing the amount of material which exhibits a different velocity.
39 Citations
16 Claims
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1. A method of acquiring an NMR signal providing motional information of a sample comprising the steps of:
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(a) applying an r.f. excitation signal to said sample for the subsequent production of an NMR signal; (b) applying spatial encoding gradient fields to said sample in a pulse sequence in which the gradient pulse train of a gradient in the direction in which motion is to be encoded exhibits a zero value first moment with respect to the timing of an r.f. excitation signal; (c) applying a motion encoding gradient field to said sample to encode motion in a given direction which is produced in response to a two-pulse gradient pulse sequence which exhibits a zero value zero moment and a non-zero value first moment; and (d) after the above steps, acquiring NMR signal information. - View Dependent Claims (2, 3, 4)
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5. A method of measuring motion in a sample in an NMR imaging system comprising the steps of:
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(a) acquiring a first sequence of NMR data from said sample by applying r.f. pulses and spatial encoding gradient fields to said sample in the absence of an effective motion-encoding gradient, and reading the resulting NMR signals; (b) performing a Fourier transform on said first sequence of NMR data with respect to said spatial encoding gradient characteristics; (c) acquiring a second sequence of NMR data from said sample by applying r.f. pulses, spatial encoding gradient fields, and a motion-encoding gradient to said sample, and reading the resulting NMR signals; (d) performing a Fourier transform on said second sequence of NMR data with respect to said spatial encoding gradient characteristics; (e) forming a ratio image on a pixel-by-pixel basis by dividing pixels of said Fourier-transformed second sequence by respective pixels of said Fourier-transformed first sequence; wherein said ratio image is representative of motion in said sample. - View Dependent Claims (6, 7, 8)
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9. A method of measuring motion in a sample in an NMR imaging system comprising the steps of:
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(a) applying a sequence of excitation pulses, spatial-encoding gradients, and a first motion-encoding gradient to said sample, said first motion-encoding gradient being applied by means of a gradient pulse train which exhibits a first, non-zero value first moment; and
acquiring NMR signals resulting from the application of said sequence of pulses and gradients;(b) applying at least one further sequence of excitation pulses, spatial-encoding gradients, and a second motion-encoding gradient to said sample, said second motion-encoding gradient being applied by means of a gradient pulse train which exhibits a second, non-zero value first moment, and acquiring NMR signals resulting from the application of said sequence of pulses and gradients; (c) performing a Fourier transform on said NMR signal information acquired in each of steps (a) and (b), respectively, with respect to said spatial encoding gradient characteristics; and (d) performing a Fourier transform on said acquired information with respect to the variation in the first moment of said motion-encoding gradient pulse train, whereby a plurality of images, each representing an amount of material in said sample with a different velocity value, are formed. - View Dependent Claims (10, 11, 12, 13)
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14. A method of acquiring an NMR signal providing motional information of a sample comprising the steps of:
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(a) applying an r.f. excitation signal to said sample for the subsequent production of an NMR signal; (b) applying spatial encoding gradient fields to said sample, one of said gradient fields being in the direction of a motion-encoding gradient and developed in response to a gradient pulse sequence exhibiting a zero value first moment; (c) applying motion-encoding gradients to said sample which are developed in response to a gradient pulse sequence exhibiting a zero value zero moment and a non-zero first moment; and (d) acquiring NMR signal information. - View Dependent Claims (15, 16)
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Specification