Measurement of capillary flow using nuclear magnetic resonance
First Claim
1. A method for providing an image of a sample, wherein individual elements of said image have intensities corresponding to the quantity of slowly flowing fluids contained in said sample, said method comprising the steps of:
- (a) generating a first image using an imaging technique wherein;
a first magnetization spatial periodicity is established;
a detected NMR signal from slowly flowing fluids is dependent on the value of said first magnetization spatial periodicity, and a detected NMR signal from stationary material is not substantially dependent on said first magnetization spatial periodicity; and
fast flowing fluids to not substantially contribute to the intensities of first image elements;
(b) adjusting a magnetization spatial periodicity control parameter comprising an interpulse interval;
(c) generating a second image using an imaging technique wherein;
a second magnetization spatial periodicity is established;
a detected NMR signal from slowly flowing fluids is dependent on the value of said second magnetization spatial periodicity, and a detected NMR signal from stationary material is not substantially dependent on said second magnetization spatial periodicity; and
fast flowing fluids do not substantially contribute to the intensities of second image elements; and
(d) mathematically manipulating said first and second images to produce a third image the intensity of whose elements are determined substantially solely by the nuclear magnetic resonance of nuclei in slowly flowing fluids in said sample.
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Abstract
An improved method for measuring very slow flow rates using nuclear magnetic resonance techniques is disclosed. The basic technique is that of steady state free precession, in which a sequence of radio frequency pulses are applied to nuclei in a magnetic field having a substantial gradient, so that a driven equilibrium state is obtained and which is characterized by a spatial periodicity in the magnetization response of the nuclei. Two images are generated. The two images may be generated using different time intervals between the application of the radio frequency pulses. Alternatively, the two images may be generated using different effective gradients. The spatial periodicity, and the NMR response of flowing nuclei to the spatial periodicity, is thus different during the two image formations. One image is subtracted from the other, which cancels signals from static nuclei in the signal, while relatively fast flowing nuclei, namely in the larger blood vessels or the like, never reach the equilibrium state. The subtraction difference is therefore proportional only to nuclei which are part of relatively slowly flowing liquids, such as in capillary blood flow in organs.
39 Citations
42 Claims
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1. A method for providing an image of a sample, wherein individual elements of said image have intensities corresponding to the quantity of slowly flowing fluids contained in said sample, said method comprising the steps of:
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(a) generating a first image using an imaging technique wherein; a first magnetization spatial periodicity is established; a detected NMR signal from slowly flowing fluids is dependent on the value of said first magnetization spatial periodicity, and a detected NMR signal from stationary material is not substantially dependent on said first magnetization spatial periodicity; and fast flowing fluids to not substantially contribute to the intensities of first image elements; (b) adjusting a magnetization spatial periodicity control parameter comprising an interpulse interval; (c) generating a second image using an imaging technique wherein; a second magnetization spatial periodicity is established; a detected NMR signal from slowly flowing fluids is dependent on the value of said second magnetization spatial periodicity, and a detected NMR signal from stationary material is not substantially dependent on said second magnetization spatial periodicity; and fast flowing fluids do not substantially contribute to the intensities of second image elements; and (d) mathematically manipulating said first and second images to produce a third image the intensity of whose elements are determined substantially solely by the nuclear magnetic resonance of nuclei in slowly flowing fluids in said sample.
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2. A method for providing an image of a sample, wherein individual elements of said image have intensities corresponding to the quantity of slowly flowing fluids contained in said sample, said method comprising the steps of:
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(a) generating a first image using an imaging technique wherein; a first magnetization spatial periodicity is established; a detected NMR signal from slowly flowing fluids is dependent on the value of said first magnetization spatial periodicity, and a detected NMR signal from stationary material is not substantially dependent on said first magnetization spatial periodicity; and fast flowing fluids do not substantially contribute to the intensities of first image elements; (b) adjusting a magnetization spatial periodicity control parameter comprising an effective gradient; (c) generating a second image using an imaging technique wherein; a second magnetization spatial periodicity is established; a detected NMR signal from slowly flowing fluids is dependent on the value of said second magnetization spatial periodicity, and a detected NMR signal from stationary material is not substantially dependent on said second magnetization spatial periodicity; and fast flowing fluids do not substantially contribute to the intensities of second image elements; and (d) mathematically manipulating said first and second images to produce a third image the intensity of whose elements are determined substantially solely by the nuclear magnetic resonance of nuclei in slowly flowing fluids in said sample.
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3. A method for providing an image of a sample, wherein individual elements of said image have intensities corresponding to the quantity of slowly flowing fluids contained in said sample, said method comprising the steps of:
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(a) generating a first image using an imaging technique wherein; a first magnetization spatial periodicity is established; a detected NMR signal from slowly flowing fluids is dependent on the value of said first magnetization spatial periodicity, and a detected NMR signal from stationary material is not substantially dependent on said first magnetization spatial periodicity; and fast flowing fluids to not substantially contribute to the intensities of first image elements; (b) adjusting a magnetization spatial periodicity control parameter; (c) generating a second image using an imaging technique wherein; a second magnetization spatial periodicity is established; a detected NMR signal from slowly flowing fluids is dependent on the value of said second magnetization spatial periodicity, and a detected NMR signal from stationary material is not substantially dependent on said second magnetization spatial periodicity; and fast flowing fluids do not substantially contribute to the intensities of second image elements; and (d) mathematically manipulating said first and second images to produce a third image the intensity of whose elements are determined substantially solely by the nuclear magnetic resonance of nuclei in slowly flowing fluids in said sample. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. An apparatus for providing an image of a sample, wherein individual elements of said image have intensities corresponding to the quantity of slowly flowing fluids contained within said sample, said apparatus comprising:
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imaging means for generating images in which substantially no contribution is made to the image element intensities by fast flowing fluids; means for adjusting a magnetization spatial periodicity control parameter comprising an interpulse interval, for allowing said imaging means to generate two images using an imaging technique wherein; respectively different magnetization spatial periodicities are established during the generation of said two images; a detected NMR signal from slowly flowing fluids is dependent on the value of said magnetization spatial periodicity; and a detected NMR signal from stationary material is not substantially dependent on the value of said magnetization spatial periodicity; and means for mathematically manipulating said two images to produce a third image whose image element intensities are determined substantially solely by the nuclear magnetic resonance of nuclei in slowly flowing fluids in said sample.
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23. An apparatus for providing an image of a sample, wherein individual elements of said image have intensities corresponding to the quantity of slowly flowing fluids contained within said sample, said apparatus comprising:
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imaging means for generating images in which substantially no contribution is made to the image element intensities by fast flowing fluids; means for adjusting a magnetization spatial periodicity control parameter comprising an effective gradient, for allowing said imaging means to generate two images using an imaging technique wherein; respectively different magnetization spatial periodicities are established during the generation of said two images; a detected NMR signal from slowly flowing fluids is dependent on the values of said magnetization spatial periodicity; and a detected NMR signal from stationary material is not substantially dependent on the value of said magnetization spatial periodicity; and means for mathematically manipulating said two images to produce a thrd image whose image element intensities are determined substantially solely by the nuclear magnetic resonance of nuclei in slowly flowing fluids in said sample.
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24. An apparatus for providing an image of a sample, wherein individual elements of said image have intensities corresponding to the quantity of slowly flowing fluids contained within said sample, said apparatus comprising:
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imaging means for generating images in which substantially no contribution is made to the image element intensities by fast flowing fluids; means for adjusting a magnetization spatial periodicity control parameter for allowing said imaging means to generate two images using an imaging technique wherein; respectively different magnetization spatial periodicities are established during the generation of said two images; a detected NMR signal from slowly flowing fluids is dependent on the value of said magnetization spatial periodicity; and a detected NMR signal from stationary material is not substantially dependent on the value of said magnetization spatial periodicity; and means for mathematically manipulating said two images to produce a third image whose image element intensities are determined substantially solely by the nuclear magnetic resonance of nuclei in slowly flowing fluids in said sample. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification