Complex quotient nuclear magnetic resonance imaging
First Claim
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1. In a nuclear magnetic resonance imaging system, including a magnet for producing a magnetic field in which an imaging subject is to be located, a radio frequency coil and a gradient field coil, apparatus comprising:
- means for collecting a first sequence of NMR signals, including means for applying a first excitation pulse sequence, means for applying a given gradient field, and means for detecting and storing said first sequence of NMR signals;
means for collecting a second sequence of NMR signals, including means for applying a second excitation pulse sequence, means for applying said given gradient field, and means for detecting and storing said second sequence of NMR signals;
means for performing a two-dimensional Fourier transform of said first and second sequences, respectively, to form first and second images having data values at spatially defined image locations; and
means for forming a ratio of data values of said first and second images at each spatially defined image location.
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Abstract
In an NMR imaging system, an image plane is scanned and NMR signals are collected over a plurality of image lines. The experiment is repeated, with the timing of the excitation pulses changed. Images are formed by performing Fourier transformations of the signal values. A ratio image is then formed by performing a complex division of the two images on a pixel by pixel basis. The ratio values cancel phase error effects in the image data and the use of complex numbers maintains the proper pixel polarity.
15 Citations
12 Claims
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1. In a nuclear magnetic resonance imaging system, including a magnet for producing a magnetic field in which an imaging subject is to be located, a radio frequency coil and a gradient field coil, apparatus comprising:
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means for collecting a first sequence of NMR signals, including means for applying a first excitation pulse sequence, means for applying a given gradient field, and means for detecting and storing said first sequence of NMR signals; means for collecting a second sequence of NMR signals, including means for applying a second excitation pulse sequence, means for applying said given gradient field, and means for detecting and storing said second sequence of NMR signals; means for performing a two-dimensional Fourier transform of said first and second sequences, respectively, to form first and second images having data values at spatially defined image locations; and means for forming a ratio of data values of said first and second images at each spatially defined image location. - View Dependent Claims (2, 3, 4)
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5. In a nuclear magnetic resonance imaging system, including a magnet for producing a magnetic field in which an imaging subject is to be located, a radio frequency coil and a gradient field coil, apparatus comprising:
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means for collecting a first sequence of NMR signals, including means for applying a first excitation pulse sequence, means for applying a given gradient field, and means for detecting and storing said first sequence of NMR signals; means for collecting a second sequence of NMR signals, including means for applying a second excitation pulse sequence, means for applying said given gradient field, and means for detecting and storing said second sequence of NMR signals; means for performing a two-dimensional Fourier transform of said first and second sequences, respectively, to form first and second images having data values at spatially defined image locations; and means for forming a ratio of data value of said first and second images at each spatially defined image location. wherein said given gradient field extends in two-dimensions; and wherein said first excitation pulse sequence acquires NMR signals by saturation recovery, and wherein said second excitation pulse sequence acquires NMR signals by inversion recovery. - View Dependent Claims (6, 7, 8)
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9. In a nuclear magnetic resonance imaging system, a method for reducing the effects of phase errors in an NMR image comprising the steps of:
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(a) collecting a first sequence of NMR signals by applying a first excitation pulse sequence and a given gradient field and detecting and storing said first sequence of NMR signals; (b) collecting a second sequence of NMR signals by applying a second excitation pulse sequence and said given gradient field and detecting and storing said second sequence of NMR signals; (c) performing at least a two-dimensional Fourier transformation of said first and second sequences, respectively, to form first and second spatially representative images of complex pixel values; and (d) forming a ratio of said complex pixel values at each corresponding image location.
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10. In a nuclear magnetic resonance imaging system, a method for reducing the effects of phase errors in an NMR image comprising the steps of:
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(a) collecting a first sequence of NMR signals by applying a first excitation pulse sequence and a given gradient field and detecting and storing said first sequence of NMR signals; (b) collecting a second sequence of NMR signals by applying a second excitation pulse sequence and said given gradient field and detecting and storing said second sequence of NMR signals; (c) performing at least a two-dimensional Fourier transformation of said first and second sequences, respectively, to form first and second spatially representative images of complex pixel values; and (d) forming a ratio of said complex pixel values at each corresponding image location, wherein step (a) comprises collecting a sequence of NMR signals by saturation recovery, step (b) comprises collecting a sequence of NMR signals by inversion recovery, and step (d) comprises forming a complex ratio of a complex inversion recovery pixel divided by a complex saturation recovery pixel at each corresponding image location. - View Dependent Claims (11, 12)
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Specification