NMR measurements using recursive RF excitation
First Claim
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1. In an NMR system for acquiring an NMR echo signal by executing a pulse sequence in which a first RF excitation pulse produces transverse magnetization in spins subject to a polarizing magnetic field and an NMR echo signal is subsequently produced and acquired by a receiver, the improvement comprising:
- means for storing the acquired NMR echo signal;
means coupled to the storing means for producing an RF excitation waveform that has a shape which is determined by the acquired NMR echo signal; and
means coupled to the last named means for executing a pulse sequence in which an RF excitation pulse has a waveform determined by the acquired NMR echo signal from a previous pulse sequence.
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Abstract
An NMR echo signal is produced in a recursive process in which one or more pulse sequences are executed and the NMR echo signal produced by each pulse sequence is employed to shape the RF excitation pulse employed in the subsequent pulse sequence. The series of NMR echo signals produced by this recursive process are progressively modified to enhance the signals produced by prominent features in the subject.
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Citations
13 Claims
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1. In an NMR system for acquiring an NMR echo signal by executing a pulse sequence in which a first RF excitation pulse produces transverse magnetization in spins subject to a polarizing magnetic field and an NMR echo signal is subsequently produced and acquired by a receiver, the improvement comprising:
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means for storing the acquired NMR echo signal; means coupled to the storing means for producing an RF excitation waveform that has a shape which is determined by the acquired NMR echo signal; and means coupled to the last named means for executing a pulse sequence in which an RF excitation pulse has a waveform determined by the acquired NMR echo signal from a previous pulse sequence.
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2. A method for producing an NMR echo signal in an NMR system, which includes:
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producing transverse magnetization in spins subjected to a polarizing magnetic field by generating an RF excitation pulse; acquiring an NMR echo signal which is produced as a result of the transverse magnetization; employing the acquired NMR echo signal to determine the shape of a subsequent RF excitation pulse; producing further transverse magnetization in spins subjected to the polarizing magnetic field by generating said subsequent RF excitation pulse and acquiring a further NMR echo signal produced as a result of the further transverse magnetization. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9)
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10. In an NMR system a method for acquiring NMR data for producing an image, the steps comprising:
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a) producing a selective presaturation RF pulse by; i) producing transverse magnetization in spins subjected to a polarizing magnetic field by generating an RF excitation pulse; ii) acquiring an NMR signal which is produced as a result of the transverse magnetization; and iii) employing the acquired NMR signal to determine the shape of the selective presaturation RF pulse; b) applying the selective presaturation RF pulse to the spins subjected to the polarizing magnetic field; and c) performing a pulse sequence to acquire an NMR signal from the spins subjected to the polarizing magnetic field, the NMR signal being used to produce an image. - View Dependent Claims (11, 12, 13)
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Specification