Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1986-02-21
1987-09-15
Tokar, Michael J.
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
324307, G01R 3320
Patent
active
046942513
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and apparatus for nuclear magnetic resonance imaging. More particularly, the present invention relates to a method and apparatus for nuclear magnetic resonance imaging whereby deterioration of image quality as a result of variation with time of the static magnetic field can be eliminated.
BACKGROUND ART
With a resistive magnet type of nuclear magnetic resonance imaging apparatus, a static magnetic field is generated by passing a fixed drive current through a static magnetic field coil. If the resultant static magnetic field is stable, then the 2-dimensional reverse Fourier transform can be applied to the measured data for thereby correctly reconstructing a image of the body of an individual under diagnosis, with an image of good quality being obtained.
However even if the power source used to generate the static magnetic field is extremely stable, so that stable constant-current drive is applied, the static magnetic field can vary by several p.p.m due to changes in the shape of the static magnetic field coil as a result of variations in the ambient temperature. For this reason, artifacts will be produced in the image which is obtained, rendering it impossible to derive a satisfactory 2-dimensional Fourier image of the body which is under diagnosis.
Proposals have been made in the prior art for producing nuclear magnetic resonance imaging which will overcome this problem, specifically in Japanese Patent Provisional Publication No. 57-66346 and in Japanese Patent Provisional Publication No. 57-192541. In the case of Japanese Patent Provisional Publication No. 57-66346, a standard specimen is disposed within the static magnetic field, and the amount of variation of the static magnetic field is derived on the basis of an NMR signal which is detected from the standard specimen. The measured data which is obtained for the body which is under diagnosis is corrected, based upon the amount of variation of the static magnetic field that is obtained in this way. However with this method, it is necessary to employ a standard specimen, and a measurement unit for the standard specimen. In the case of Japanese Patent Provisional Publication No. 52-192541, an NMR signal is detected upon cessation of application of a gradient magnetic field to the body which is under diagnosis, and the amount of variation of the static magnetic field is obtained from this NMR signal, whereby the current that is passed through the static magnetic field correction coil is controlled such as to bring the amount of variation of the static magnetic field to zero. With this method it is not necessary to use a test specimen or a measurement unit for the test specimen. However due to the fact that it is necessary to halt application of the gradient magnetic field in order to measure the NMR signal produced by the body which is under diagnosis at the time of cessation of the gradient magnetic field, the measurement sequence must be different from the normal sequence, i.e. a special measurement sequence must be adopted.
DISCLOSURE OF INVENTION
It is an objective of the present invention to provide a method and apparatus for nuclear magnetic resonance imaging whereby it is not necessary to employ a standard specimen and a measurement unit for such a standard specimen, or to utilize a special measurement sequence, in order to obtain the amount of variation of the static magnetic field.
The present invention constitutes a method and apparatus whereby measured data is obtained with the effects of variation with time of the static magnetic field being eliminated therefrom, and employs the scan sequence for the Fourier transform imaging.
The view data G(k,t) for the body which is under diagnosis is measured under the condition that the phase of spin within the body under diagnosis is twisted in one direction by a specific amount. The view data G(-k,t) is then measured under the condition that the phase of spin within the body under diagnosis is twisted in the opposite direction to the aforem
REFERENCES:
patent: 4486709 (1984-12-01), Bendall
patent: 4506222 (1985-03-01), Edelstein
patent: 4527124 (1985-07-01), Van Uijen
patent: 4532474 (1985-07-01), Edelstein
patent: 4602214 (1986-07-01), Edelstein
Hoshino Kazuya
Yoshitome Eiji
Kojima Moonray
Tokar Michael J.
Yokogawa Medical Systems Limited
LandOfFree
Method and apparatus for nuclear magnetic resonance imaging does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for nuclear magnetic resonance imaging, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for nuclear magnetic resonance imaging will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1388010