Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1988-10-24
1990-02-20
Tokar, Michael J.
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
324307, G01R 3320
Patent
active
049029720
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and an apparatus for causing nuclear magnetic resonance of an object and, more particularly, to a method and an apparatus for causing nuclear magnetic resonance of an object which are suitable for diagnosing living bodies by nuclear magnetic resonance.
BACKGROUND ART
Nuclear magnetic resonance has been used in the field of structural analysis, as well as studies on physical properties. In recent years, this phenomenon finds its use also in the field of medical diagnosis. Medical diagnostic apparatus making use of nuclear magnetic resonance signal for medical diagnosis are generally referred to as nuclear magnetic resonance imaging apparatus or magnetic resonance imaging apparatus.
In a typical nuclear magnetic resonance imaging apparatus which is well known, a magnetic field gradient G.sub.z is applied to a static magnetic field in a first predetermined period and, in this period, selective high-frequency 90.degree. pulses are applied to the object disposed in the static magnetic field. As a result, a slice of the object perpendicular to the Z-axis is selectively excited. Namely, falling of nuclear spins onto the Y-axis takes place in the slice. The fallen nuclear spins are gradually dispersed.
Subsequently, the magnetic field gradient G.sub.z and selective high-frequency 180.degree. pulses are applied so that the nuclear spins in the excited slice are inverted. In consequence, the dispersed nuclear spins gradually converge, whereby a spin echo signal is generated from the whole slice as a nuclear magnetic resonance signal.
In the period intermediate between the application of the selective high-frequency 90.degree. pulse and the selective high-frequency 180.degree. pulse, a magnetic field gradient G.sub.Y is applied to the static field and, after the application of the 180.degree. pulse, the magnetic field gradient G.sub.x is applied to the static magnetic field, and the spin echo signal generated from the whole slice is read during the application of the magnetic field gradient G.sub.x.
The described steps are executed N times to that N spin echo signals are generated. In the mean time, however, the magnetic field gradient G.sub.Y is varied in such a manner that the time integration value is changed at the same rate in each time. The magnetic field gradient G.sub.Y is referred to as "magnetic field gradient for phase encoding". Further, G.sub.x is for frequency encoding and is called a read magnetic field gradient. Sampling is executed to obtain N samples of each of N spin echo signals, and two-dimensional Fourier transformation is applied to each of N spin echo signals each having N sample signals, so that a nuclear magnetic resonance image constituted by N.times.N element signals is obtained. The number N is typically set to be 256.
In general, the center of the display image of the nuclear magnetic resonance imaging system coincides with the center of the gradient magnetic field which is given by the magnetic field gradients G.sub.Y and G.sub.x. It is therefore not easy to obtain an enlarged image of an image portion which does not coincide with the center of the gradient magnetic field.
Japanese Patent Laid-Open No. 207045/1985 discloses an art which is intended to overcome the above-described problem.
According to this method, an axis which interconnects the center of the gradient magnetic field and the center of the image portion to be enlarged (imaging center) is selected as a frequency axis, while an axis perpendicular to this frequency axis is selected as a phase encode axis. Then, the detected nuclear magnetic resonance signal is subjected to homo-dyne detection by employing, as a reference signal, an image center resonance frequency which is determined from the distance between the image center and the center of the gradient magnetic field and the magnitude of the reading magnetic field gradient, so that the field of view is shifted along the frequency encoding axis.
This art, however, has the following disadvantages.
(1) It is nece
REFERENCES:
patent: 4593247 (1986-06-01), Glover
patent: 4644278 (1987-02-01), Sano et al.
patent: 4689567 (1987-08-01), Maudsley
Aritomi Toshiaki
Koizumi Hideaki
Takeda Ryuzaburo
Hitachi , Ltd.
Tokar Michael J.
LandOfFree
Method and apparatus for causing nuclear magnetic resonance of a 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 causing nuclear magnetic resonance of a, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for causing nuclear magnetic resonance of a will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1618395