摘要:
Disclosed is an NMR gated imaging apparatus in which an ultrasonic pulse signal is repeatedly transmitted toward the heart of a human body from an ultrasonic transducer to detect the position of the heart on the basis of the time of detection of a peak of an echo signal, and excitation and measurement of an NMR signal are executed only when a peak detector generates a detection output signal having a level included in a predetermined range. Thus, the NMR signal is repeatedly measured according to a programmable phase encoding amount at a limited phase of gated imaging.
摘要:
A method of finding error distribution in the static magnetic field and distribution of deviations from straight lines in the gradient magnetic fields of an NMR imaging apparatus which employs the applied spin-warp method. A phantom whose shape has been known is measured in the read-out gradient magnetic fields having different polarities to obtain two spin density distribution images. The two images are then compared with the shape of said phantom to measure the distortion distributions of the images. Error in the static magnetic field and deviations of the gradient magnetic fields from the straight lines are analyzed from the distortion distributions. From the thus obtained error distribution, furthermore, distortion induced in imaging the object is estimated, and the distortion contained in the image that is reconstructed from the spin density of the object by the spin-warp method is corrected using the thus estimated value.
摘要:
Disclosed in a nuclear magnetic resonance (NMR) based inspection apparatus using an SQUID flux meter for detecting a small NMR signal, in which a receiving coil for receiving the NMR signal from an object is connected to a mixer, which mixes a reference high-frequency signal with the NMR signal so that the NMR signal is reduced to a low-frequency signal having a differential component of frequencies of both signals, and the low-frequency signal is applied to the input coil of the SQUID flux meter so that it is converted into a voltage signal. The mixer circuit includes Schottky diodes operative at a liquid helium temperature or Josephson junctions, and the portions of apparatus from the reception coil up to the SQUID flux meter are operated in a superconductive state at a liquid helium temperature.
摘要:
An NMR imaging apparatus and method for detecting a nuclear spin resonance signal from an object, which is placed in a magnetic field, to produce images of the object. At an instant when the spins come into phase after the signal detection by a first spin excitation, RF magnetic field pulses are applied for rotating the direction of the spin to that opposite to the initial state. After that, the spin excitation and the signal direction of second time are conducted to measure the data which are different in the effect of the relaxation time from the first measurements. By repeating these sequences, it is possible to produce a plurality of images such as an intensity image or a relaxation time enhanced image.
摘要:
An NMR imaging method and apparatus of the type in which a 180-degree RF pulse is applied to generate a spin echo after the selective excitation of a spin by a 90-degree RF pulse. A dummy gradient field, which has the same direction and intensity as those of a gradient field to be applied when the spin echo is observed, is applied between said 90-degree RF pulse and said 180-degree RF pulse so that the instant of starting the application of the gradient field for signal observation is advanced to the extent corresponding to said dummy gradient field.
摘要:
An imaging apparatus using nuclear magnetic resonance is disclosed in which both an image corresponding to the projection of a nuclear spin distribution in a to-be-inspected object on a two-dimensional plane and a display mark indicating a desired measuring position are displayed on a display face of a display device such as a CRT display, the display mark is freely moved on the display face to be set at a desired position on the display face, and magnetic field generating means for generating a static magnetic field, linear gradient field, or radio frequency magnetic field is controlled on the basis of the desired position of the display mark to obtain an image of that cross section of the object which is located at a position indicated by the display mark.
摘要:
In an imaging apparatus using the nuclear magnetic resonance, a solenoid coil and a slot-resonator coil are combined with each other so as to constitute a quadrature-phase detection probe. In order to operate the slot-resonator coil at low frequency, inductance is added to the slot-resonator coil. Further in order to cut the coupling between a transmitting coil and a receiving coil in a cross coil system, a capacitor together with the added inductance to form a resonant circuit is connected in parallel to the inductance. A favorable probe can be obtained in a vertical-magnetic field type imaging apparatus.
摘要:
A testing method and apparatus by use of nuclear magnetic resonance measure, at timings influenced and not influenced from chemical shift, nuclear magnetic resonance signals taken from a sample to be tested at least one of whose values of permeability and chemical shift is known and a reference sample both of whose values of permeability and chemical shift and their spatial distribution are uniform thereby to acquire four items of image vector information. Further, the testing method and apparatus take phase differences between the items of image vector information to separately extract the phase component influenced by the permeability distribution and the phase component influenced from the chemical shift.
摘要:
An NMR imaging method for obtaining a tomographic image of an object through two-dimensional Fourier transformation imaging. After a whole image of a predetermined slice is displayed, a given field of view having a given size and located at a given position in the image is designated. On the basis of data derived from this designation, setting values for magnetic field generators and a signal detector are arithmetically determined for limiting the region in which the NMR signal is generated and the region to be imaged, whereby local imaging of the aforementioned field of view is conducted with high resolution. Further, division of an image resulting from the imaging operation is automatically corrected by exchanging positionally the divided image blocks with each other.
摘要:
In an imaging apparatus using nuclear magnetic resonance which includes apparatus for generating a static magnetic field, a linear gradient magnetic field and a radio frequency magnetic field, respectively, signal detection device for detecting the nuclear magnetic resonant signal from an object to be inspected, a computer for calculating from the detection signal an image and output device for displaying the result of calculation by the computer, the improvement wherein the size of the object to be inspected is detected by use of ultrasonic wave or light beams and a signal indicative of the detected size of the object is applied to the linear gradient magnetic field generation apparatus so as to control the intensity of the linear gradient magnetic field.