Abstract: In magnetic resonance imaging, a first echo train is obtained by applying a readout gradient magnetic field to a region of interest to be imaged and periodically inverting the polarity of the readout gradient magnetic field, without applying an encoding gradient magnetic field to the region of interest. A periodic change of phase shift of the first echo train is detected from the first echo train. Information indicating phase shifts of all of the echoes in the first echo train is obtained using the periodic change of phase shift. A second echo train is obtained by applying a readout gradient magnetic field and an encoding magnetic field to the region of interest and periodically inverting the polarity of the readout gradient magnetic field. Phases of echoes in the second echo train are corrected using the information indicating phase shifts of all of the echoes in the first echo train.

Abstract: A magnetic resonance imaging method and apparatus employing a pulse sequence including a periodically switched readout gradient and a phase encoding gradient to derive a series of echo signals. Prior to execution of the pulse sequence for acquiring data for imaging, a pulse sequence in which the phase encoding gradient is cancelled is executed to obtain information of deviation in position of echo peaks. Thereafter, a pulse sequence including the phase encoding gradient is executed and at this time, sampling start timings for echo data sampling in respective phase periods of the readout gradient are controlled according to the information of the echo peak deviation. Further, a phase difference between data of odd number echo signals and data of even number echo signals is compensated by rotating either of the data of the odd number echo signals or the even number echo signals by a suitable rotating angle to minimize artifacts.

Abstract: A bobbin for holding a gradient magnetic field coil, having a changeable size and sectional shape (a separable bobbin) is constituted by assembling coil supporters (a bobbin divided into a plurality of segments). The separable bobbin has coil supporters of an upper part a bottom part and a set of side surface parts and at least two supporting rods made of a nonmagnetic substance are fitted to the side surface parts of the coil supporters. Holes permitting the insertion of the supporting rods are bored in the upper and bottom parts of the coil supporters. The length d1 between both side surface parts can be made variable by adjusting the insertion length of the supporting rod into the upper and bottom parts. Accordingly, the distance between a patient and a gradient magnetic field can be reduced, and an intended gradient magnetic field intensity can be generated by a smaller current producing the gradient magnetic field than in the prior art.

Abstract: An active noise cancellation apparatus of an MRI apparatus, including a detector for detecting vibration of a bobbin or a driving signal of a magnetism generator as a noise source signal, error signal detectors for detecting actual noise near the ears of a patient, a circuit for generating a noise cancellation signal having an opposite phase to a phase of a noise signal generated by an MRI apparatus and having an amplitude proportional to the output of the error signal detectors, from the detected noise source signal and the output of the error signal detectors, and a sound generator for generating a sound wave by the noise cancellation signal.

Abstract: In a magnetic resonance imagining method, using an effect that a fluid flows out of a plane where it is selectively excited between the time of applying a 90.degree. radio frequency pulse and the time of applying of a 180.degree. radio frequency pulse, two, images are separately constructed from multiple echo signals which are sampled before applying the 180.degree. radio frequency pulse and multiple echo signals which are sampled after applying the 180.degree. radio frequency pulse. An image of the fluid flow and an image of a static part are separated from each other based on a difference between the two constructed images.

Abstract: This invention relates to a ultra-high speed nuclear magnetic resonance fluid imaging method for selectively reconstructing projected images of a fluid from an echo train generated by the use of a readout gradient magnetic field which inverses periodically. A pulse-like encoding gradient magnetic field is used in combination with a readout gradient magnetic field which inverses periodically, so as to generate an echo train containing alternately echoes whose phase change of magnetization due to a flow is emphasized and echoes whose phase change of magnetization due to the flow is corrected, and subjected sequentially to phase encoding. A data train containing only the echoes whose phase change of magnetization due to the flow is emphasized and a data train containing only the echoes whose phase change of magnetization due to the flow is corrected are formed from sampling data of these echoes, respectively, and two images are then obtained by subjecting them individually to two-dimensional Fourier transform.

Abstract: A nuclear magnetic resonance multi-echo imaging method and an apparatus therefor in which gradient field pulses having predetermined products of intensity and time are applied on both sides of an inversion pulse in at least two of three directions which are orthogonal to each other to dephase components of a magnetization vector which leads to an artifact signal and an error signal, whereby only a normal echo signal can be sampled to form a correct image.

Abstract: An NMR spectroscopic imaging method of obtaining separate spin distribution images for respective spectral components of the spectrum of an NMR signal caused by the chemical shift of nuclides of interest in an object includes providing for a transversal magnetization signal of the object placed in a static magnetic field. A position of the signal in a phase domain is translated in a K-space from the origin thereof. Further, the signal is sampled while rotating a position of the signal in the K-space plural times on a certain circle in the K-space by applying a rotating field gradient, thereby to obtain a group of signal data. Signal data trains each of which is composed of signal data present at the same position on the K-space in the signal data group obtained by the sampling during the plural signal rotations, is subjected to Fourier transformations, respectively, thereby effecting a spectral analysis of the NMR signal.

Abstract: An NMR imaging method is disclosed in which an object is measured in accordance with a pulse sequence capable of expressing a difference between two of a plurality of chemical shifts by a phase difference in a signal, that is, a pulse sequence 90.degree.-.tau..sub.a -180.degree.-.tau..sub.b -spin echo (where .tau..sub.a .noteq..tau..sub.b) to obtain spin distribution data, a histogram with respect to the phase of the spin distribution data is formed to regard a phase corresponding to that one of a plurality of peaks of the histogram which exists at one end of the histogram, as a position-independent offset phase which is contained in the spin distribution data and is peculiar to an NMR imaging apparatus, and the spin distribution data is corrected using the offset value thus obtained, to extract spin density distribution data for each of the chemical shifts from the corrected spin distribution data.

Abstract: A method for providing spin density distribution images of an object, discriminated with respect to plural chemical shifts. This method is performed by repeating a measurement sequence in a spin warp imaging method, of the spin data plural times, with a time difference .DELTA..tau. between a time interval .tau..sub.1 from spin excitation to a 180.degree. RF pulse and a time interval .tau..sub.2 from the 180.degree. RF pulse to a peak of a spin echo, altering .DELTA..tau. in the ways corresponding the number of chemical shifts to be discriminated from one another, subjecting the respective spin data to two-dimensional Fourier transform to provide plural sets of spin data for respective coordinates in a spatial domain, and solving simultaneous equations of the sets of spin data to provide spin densities corresponding to the respective chemical shifts.

Abstract: The present invention is an imaging method using three-dimensional NMR to which an echo-planar method is applied. After excitation of nuclear spins, the gradient magnetic field Gx for phase-encoding is applied and there is repeated a sequence of measuring and obtaining an echo train of spin-echoes with a constant gradient magnetic field Gx and a periodically-inverted gradient magnetic field Gy, as varying the amount of encoding, so as to obtain the three-dimensional imaging by the Fourier-conversion. Moreover, after the selective excitation of spins within an X-Y surface, a 180.degree. radio frequency pulse is applied. As varying the time difference .tau..sub..epsilon. between the interval from the excitation until the application of the 180.degree. radio frequency pulse and the interval from the application thereof until a peak of a first echo of an echo train, three-dimensional imaging is carried out with a chemical shift axis as one axis by repeating the sequence and accomplishing Fourier-conversion with .

Abstract: An NMR imaging method which provides a three-dimensional image representative of the two-dimensional distribution of nuclear spin species resolved by chemical shift or the local spectra resolved by two-dimensional location. After the excitation of nuclear spins and the phase-encoding by application of a field gradient G.sub.y, a periodically inverting field gradient G.sub.x is generated to yield a continuous echo train. The echo train is sampled and separated into data of odd-numbered echoes and data of even-numbered echoes which data are in turn reconstructed into two-dimensional data arrays, respectively. The data thus reconstructed are three-dimensional Fourier-transformed.

Abstract: 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.

Abstract: A radiation-image photographing apparatus comprises a radiation source, a radiation detector disposed in opposition to the radiation source for detecting radiation through an object to be examined and to generate an electrical signal proportional to the amount of incident radiation, a scanning device for changing the relative, positional relationship between the radiation source and the radiation detector, an analog-to-digital converter for converting the output signal from the radiation detector to a digital quantity, a memory for storing the digital signal, an arithmetic unit, and a display unit.

Abstract: A method is disclosed in which projection images of a certain cross-section of an object are produced through irradiation from various directions to the cross-section, and a three-dimensional image of the cross-section is reconstructed from the projection images. A convolution integral operation is performed on the projection images by means of a weighting function obtained from a function whose second differentiation is positive in at least a predetermined range of a spacial frequency domain and which has a positive first-differential coefficient at a point where the spacial frequency is equal to zero.

Abstract: In a system in which the tomographic image of an object under investigation is produced on the basis of the amount of absorption of radiation by the object when a source of radiation and a plurality of radiation sensitive detectors with the object interposed therebetween are rotated around the object, the output signal from at least one of the plural detectors is used to correct the radiation absorption amount. Another selected one of the plural detectors may be used for checking whether the object is positioned within a useful detection view.

Abstract: A tomographic imaging system is disclosed in which the quantity of absorption or transmittance of a transmissive radiation by or through a certain tomographic cross-section of an object under consideration is detected and the distribution of radiation absorption or transmittance in the cross-section is reconstructed through a convolution operation. A weighting function used in the convolution operation is prepared with a predetermined one of its positive orders the value of which is an integration of the weighting function from the predetermined positive order to positive infinity and a predetermined one of its negative orders the value of which is in integration of the weighting function from the predetermined negative order to negative infinity.