NMR flow imaging using bi-phasic excitation field gradients
First Claim
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1. In a gyromagnetic resonance instrument which performs a measurement cycle in which a FID signal produced by gyromagnetic material having a transverse magnetic moment is detected and processed to produce an indication of the amount of transverse magnetization, the improvement comprising:
- an oscillator for producing an excitation signal at the Larmor frequency of the gyromagnetic material;
an excitation field gradient coil coupled to the oscillator and mounted in the instrument to produce a transversely directed magnetic field at the Larmor frequency which has a magnitude gradient in a preset direction; and
control means for producing a motion sensitized FID signal by controlling the excitation signal applied to the excitation field gradient coils such that a bi-phasic excitation field gradient is applied to the gyromagnetic material.
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Abstract
An NMR zeugmatographic scanner is modified to provide flow images. A motion sensitizing, bi-phasic excitation field gradient is applied during each measurement cycle to produce transverse magnetization in paramagnetic nuclei which are moving in the direction of the gradient. The resulting free induction signal is processed using an inverse Fourier transformation to produce images of flowing paramagnetic nuclei.
21 Citations
7 Claims
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1. In a gyromagnetic resonance instrument which performs a measurement cycle in which a FID signal produced by gyromagnetic material having a transverse magnetic moment is detected and processed to produce an indication of the amount of transverse magnetization, the improvement comprising:
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an oscillator for producing an excitation signal at the Larmor frequency of the gyromagnetic material; an excitation field gradient coil coupled to the oscillator and mounted in the instrument to produce a transversely directed magnetic field at the Larmor frequency which has a magnitude gradient in a preset direction; and control means for producing a motion sensitized FID signal by controlling the excitation signal applied to the excitation field gradient coils such that a bi-phasic excitation field gradient is applied to the gyromagnetic material. - View Dependent Claims (2, 3)
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4. In an NMR scanner for producing images from data collected during measurement cycles, a method for producing data during such a measurement cycle which indicates motion in gyromagnetic material, the steps comprising:
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applying a first bi-phasic excitation field gradient to the gyromagnetic material; receiving the FID signal which is produced by the gyromagnetic material in response to the first bi-phasic excitation field gradient; storing the received FID signal; applying a second bi-phasic excitation field gradient to the gyromagnetic material; applying a homogeneous transverse excitation field to the gyromagnetic material; receiving the FID signal which is produced by the gyromagnetic material in response to the homogeneous transverse excitation field; and storing the received FID signal. - View Dependent Claims (5, 6, 7)
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Specification