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US 5,184,073 AGranted
Method for correcting phase errors in a nuclear magnetic resonance signal and device for realizing same
AssigneesHitachi Medical Corporation, Hitachi, Ltd.
InventorsHiroyuki Takeuchi, Tatsuo Nozokido, Chikako Nakamura
Life of this patent
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Abstract
A method for correcting phase errors in a nuclear magnetic resonance signal is disclosed, by which central frequencies of NMR signals are measured directly before and directly after or in addition in a course of a normal measurement for obtaining an NMR signal for imaging and an amount of phase error is obtained for each of the NMR signals for imaging by using a difference between the central frequencies and a measurement time for each of the NMR signals for imaging.
Claims14
A method for correcting phase errors in a nuclear magnetic resonance signal comprising the steps of:
- (a) measuring a first NMR signal in a pulse sequence, where at least neither phase encoding pulse nor frequency encoding pulse is applied to a body to be examined, directly before a normal measurement for obtaining an NMR signal for imaging is effected;
- (b) obtaining a frequency spectrum for said first NMR signal and a first central frequency giving a peak of said frequency spectrum;
- (c) effecting said normal measurement according to a predetermined pulse sequence;
- (d) measuring a second NMR signal in a pulse sequence, where at least neither said phase encoding pulse nor said frequency encoding pulse is applied thereto, directly after said normal measurement;
- (e) obtaining a frequency spectrum for said second NMR signal and a second central frequency giving a peak of said frequency spectrum;
- (f) obtaining an amount of phase error for each of said NMR signals for imaging by using a difference between said first central frequency and said second central frequency and a measurement time for each of said NMR signals for imaging;
- (g) correcting said phase error for each of said NMR signals for imaging;
- and
- (h) reconstructing an image by using a signal corrected.
6 more elements
A method for correcting phase errors in a nuclear magnetic resonance signal comprising the steps of:
- (a) measuring a first NMR signal in a pulse sequence, where at least neither phase encoding pulse nor frequency encoding pulse is applied to a body to be examined, directly before a normal measurement for obtaining an NMR signal for imaging is effected;
- (b) obtaining a frequency spectrum for said first NMR signal and a first central frequency giving a peak of said frequency spectrum;
- (c) measuring second to (n-1)-th NMR signals, where N is an integer, in a pulse sequence, where at least neither phase encoding pulse nor frequency encoding pulse is applied thereto, once or at a plurality of different times in a course, when said normal measurement is effected according to a predetermined pulse sequence;
- (d) measuring an N-th NMR signal in a pulse sequence, where at least neither said phase encoding pulse nor said frequency encoding pulse is applied thereto, directly after said normal measurement;
- (e) obtaining frequency spectrums for said second to N-th NMR signals and second to N-th central frequencies giving respective peaks of said frequency spectrums;
- (f) obtaining an amount of phase error for each of said NMR signals for imaging by using a difference between said central frequencies and a measurement time for each of said NMR signals for imaging at closest points of time before and after each of said NMR signals for imaging obtained by said normal measurement;
- (g) correcting said phase error for each of said NMR signals for imaging;
- and
- (h) reconstructing an image by using a signal corrected.
6 more elements
A method for correcting phase errors in a nuclear magnetic resonance signal comprising the steps of:
- (a) measuring NMR signal in a pulse sequence, where at least neither phase encoding pulse nor frequency encoding pulse is applied to a body to be examined, at least directly before and directly after a normal measurement for obtaining an NMR signal for imaging is effected, to obtain central frequencies thereof;
- (b) obtaining an amount of phase error for each of said NMR signals for imaging by using a variation between said central frequencies obtained and a measurement time for each of said NMR signals for imaging to correct said phase error therefor;
- and
- (c) constructing an image by using a signal corrected.
1 more element
A device for correcting phase errors in a nuclear magnetic resonance signal comprising:
- (1) static magnetic field generating means using a permanent magnet;
- (2) means for generating gradient magnetic field in directions of three axes of a three-dimensional coordinate system;
- (3) means for measuring a first NMR signal in a pulse sequence, where at least neither phase encoding pulse nor frequency encoding pulse is applied to a body to be examined, directly before a normal measurement for obtaining an NMR signal for imaging is effected;
- (4) means for obtaining a frequency spectrum for said first NMR signal and a first central frequency giving a peak of said frequency spectrum;
- (5) control means for effecting said normal measurement according to a predetermined pulse sequence;
- (6) means for measuring a second NMR signal in a pulse sequence, where at least neither said phase encoding pulse nor said frequency encoding pulse is applied thereto, directly after said normal measurement;
- (7) means for obtaining a frequency spectrum for said second NMR signal and a second central frequency giving a peak of said frequency spectrum;
- (8) means for obtaining an amount of phase error for each of said NMR signals for imaging by using a difference between said first central frequency and said second central frequency and a measurement time for each of said NMR signals for imaging;
- (9) means for correcting said phase error for each of said NMR signals for imaging;
- and
- (10) means for reconstructing an image by using said NMR signals corrected.
8 more elements
A device for correcting phase errors in a nuclear magnetic resonance signal comprising:
- (1) static magnetic field generating means using a permanent magnet;
- (2) means for generating gradient magnetic fields in directions of three axes of a three-dimensional coordinate system;
- (3) means for measuring a first NMR signal in a pulse sequence, where at least neither phase encoding pulse nor frequency encoding pulse is applied to a body to be examined, directly before a normal measurement for obtaining an NMR signal for imaging is effected;
- (4) means for obtaining a frequency spectrum for said first NMR signal and a first central frequency giving a peak of said frequency spectrum;
- (5) means for measuring second to (N-1)-th NMR signals, where N is an integer, in a pulse sequence, where at least neither phase encoding pulse nor frequency encoding pulse is applied thereto, once or at a plurality of different times in a course, when said normal measurement is effected according to a predetermined pulse sequence;
- (6) means for measuring an N-th NMR signal in a pulse sequence, where at least neither said phase encoding pulse nor said frequency encoding pulse is applied thereto, directly after said normal measurement;
- (7) means for obtaining frequency spectrums for said second to N-th NMR signals and second to N-th central frequencies giving respective peaks of said frequency spectrums;
- (8) means for obtaining an amount of phase error for each of said NMR signals for imaging by using a difference between said central frequencies and a measurement time for each of said NMR signals for imaging at closest points of time before and after each of said NMR signals for imaging obtained by said normal measurement;
- (9) means for correcting said phase error for each of said NMR signals for imaging;
- and
- (10) means for reconstructing an image by using said NMR signals corrected.
8 more elements
A device for correcting phase errors in a nuclear magnetic resonance signal comprising:
- (1) means for measuring NMR signal in a pulse sequence, where at least neither phase encoding pulse nor frequency encoding pulse is applied to a body to be examined, at least directly before and directly after a normal measurement for obtaining an NMR signal for imaging is effected, to obtain central frequencies thereof;
- (2) means for obtaining an amount of phase error for each of said NMR signals for imaging by using a variation between said central frequencies obtained and a measurement time for each of said NMR signals for imaging to correct said phase error therefor;
- and
- (3) means for reconstructing an image by using said NMR signals corrected.
1 more element
Dependencies are inferred from the claim text.