Hitachi Medical Corporation

Hitachi, Ltd.

Hitachi Microcomputer Engineering, Ltd.

Hitachi, Ltd. , Hitachi Medical Corporation

Hiroshi Nishimura

Hiroyuki Takeuchi

Akira Maeda

Tetsuo Yokoyama

Shinji Kawasaki

Takashi Kasama

Tetsuhiko Takahashi

Yoshitaka Bito

Etsuji Yamamoto

Hitoshi Arai

Osamu Miyazaki

Shigeru Watanabe

Chitose Nakaya

Isao Horiba

Hitoshi Yoshino

Akihiro Miyajima

In an MR imaging method, at least radio frequency pulses for excitation are repetitiously consecutively applied in accordance with predetermined pulse sequences until measurement of NMR signals corresponding to phase encoding numbers necessary for desired image construction ends, an external trigger signal synchronous with periodical motion of an object to be inspected is received during the period of application, and a gradient magnetic field having a phase encoding amount necessary for the image construction is applied at the termination of a predetermined time following the reception of the trigger signal to fetch at least one NMR signal. When a plurality of NMR signals are desired to be fetched, a plurality of gradient magnetic fields having mutually different phase encoding amounts are applied. This process is repeated until measurement of NMR signals corresponding to phase encoding numbers necessary for desired image construction ends and an image at a desired phase of the periodical motion of the inspected object is constructed using the thus fetched NMR signals.

Method and apparatus for MR imaging without a flashing phenomenon of an

A gradient magnetic field generation apparatus for generating a gradient magnetic field in a space in which an inspection object is placed includes at least one gradient magnetic field coil and a retaining member of the coil which undergoes deformation vibration by an electromagnetic force generated when a current is caused to flow through the coil. This apparatus generates noise and vibration whenever a pulse current is applied to the coil, because an electromagnetic force develops in the coil due to the pulse current and the coil as well as the retaining member of the coil undergo deformation and vibration. Therefore, a force which inhibits this deformation and vibration is applied to the retaining member so as to prevent deformation and vibration of the coil and the retaining member and to keep their shapes constant. In a preferred embodiment, a piezoelectric device is fixed to the retaining member without damping, and the force for inhibiting deformation and vibration of the retaining member is applied by controlling a voltage applied to the piezoelectric device.

Quiet magnetic resonance imaging apparatus

A radio frequency pulse to excite nuclei constituting an object to be imaged, a slice selecting gradient magnetic field pulse applied when the radio frequency magnetic field pulse is applied, a phase encoding gradient magnetic pulse, a frequency encoding gradient magnetic field pulse are applied to the object to be imaged placed in a static magnetic field. Then the generated nuclear magnetic resonance signals are detected many times to form an image of the internal structure of the object to be imaged using the detected signals. In this occasion, the amplitude of the slice selecting gradient magnetic field pulse or the width of the radio frequency pulse is changed corresponding to the amount of phase encoding given by the phase encoding gradient magnetic field pulse. In multi-slice imaging for detecting the signals from a plurality of slices spatially laminated, part of the signals are used in common between the slices adjacent to each other when two-dimensional images of those slices are reconstructed.

Magnetic resonance imaging method and apparatus

In an image reconstruction method in a nuclear magnetic resonance imaging apparatus, the method comprises first and second steps to get detected data S.sub.I for at least about half of region inclusive of an origin and data S.sub.IV in a region symmetric with respect to a line passing through an origin on one of axes from the detected region in the acquired data space and parallel to the other axis, respectively, third and fourth steps to perform inverse Fourier transform on the data S.sub.I and S.sub.IV, respectively, a fifth step to get a complex conjugate value of the result obtained from Step 3, a sixth step to get a complex conjugate value of the result obtained from Step 4, a seventh step to calculate a phase map from the results obtained from the second, third, fourth, fifth and sixth steps, an eighth step to multiply the result obtained from step 6 by the phase map obtained from step 7 and to obtain a phase corrected data, and a ninth step to sum the result obtained from the third step and the result obtained from the eighth step. The method can thus obtain the whole reconstructed image.

Image reconstruction method in nuclear magnetic resonance imaging

A method and apparatus for compensating for nonuniformity of a static magnetic field in a MRI system wherein one of X-, Y- and Z-axes of a Cartesian coordinate system is selected as a phase encoding direction, a region of a field of view is selectively excited by applying a high frequency pulse of a predetermined angle to an object under inspection, and an NMR signal is measured by applying a phase encoding gradient magnetic field and a frequency encoding gradient magnetic field after application of the high frequency pulse for a plurality of times while changing the phase encoding gradient magnetic field. A peak value is detected of the measurement data obtained for determining a phase encoding quantity at which the peak value can be obtained, an intensity and a polarity of a linear component of nonuniformity components of the static magnetic field in the direction selected is determined by obtaining an intensity and a polarity of the phase encoding gradient magnetic field corresponding to the peak value, and a pulse sequence for measuring the NMR signal is executed by applying a gradient magnetic field added with a compensating gradient magnetic field having the same intensity as the linear component and a polarity opposite to the linear component to a gradient magnetic field applied in the selected direction.

Method and apparatus for compensating for nonuniformity of static

In one aspect of correcting phase distortion in an MR imaging system at high speed and with high precision, partial regions having any shapes are established on a complex image reconstruction, linear phase distortion is estimated for every partial region and the phase distortion of the whole image is corrected by use of the estimated phase distortion. In another aspect, a plurality of phase distortion patterns are measured in advance through phantom imaging and stored. The phase distortion pattern is invariable and hence it is not necessary to perform the measurement for each impage processed. Phase distortion included in data acquired through imaging is corrected by representing it as a summation of the plurality of phase distortion patterns with weighting factors.

Method and apparatus for correction of phase distortion in MR imaging

An image reconstruction method for a magnetic resonance imaging device is disclosed, by which phase distortions of a magnetic resonance signal are stored in the form of a table prepared previously, by using a phase encode amount and an imaging region size as parameters; the phase distortions of the magnetic resonance signal are corrected on the basis of the phase distortions stored in the table for the measured magnetic resonance signal or the phase distortions varying for every line are presumed from the difference in the phase between the phase of hypothetical data including no phase distortions and the phase of measured data; and the phase distortions of the measured magnetic resonance signal are corrected by using this presumed value.

Image reconstruction method for a magnetic resonance imaging device and

A CT image processor for use in X-ray computerized tomographic system including an X-ray source for providing fan beams on an object being examined, a multichannel X-ray detector for detecting the fan beams transmitted through the object and a processor for reproducing a sectional image of the object including circuitry for obtaining a back projection of the signal obtained from the multichannel radioactive ray detectors, the processor circuitry also having means for rearranging the order of the fan beams into parallel beams and for effecting scaled-up interpolative operations based on the projected image signal so as to use the scaled-down interpolated data for the back projection.

CT image processor using data expansion for reducing structural noise in

A computerized tomography system which includes an X-ray generator for producing X-rays, an X-ray detector array for detecting the X-rays transmitted through a subject, and a subject bed. The X-ray tube and the X-ray detectors are opposed to each other, and the X-ray beams are irradiated upon the subject in a sectorial manner at a large number of angles to scan the subject while the X-ray tube and the X-ray detectors are being revolved around the subject, the X-ray tube and X-ray detectors remaining opposed to each other the during revolution. The system includes a system for rapidly and continuously revolving a frame bearing the X-ray tube, a system for moving the subject bed perpendicularly to a plane of revolution of the X-ray tube and for moving the subject bed synchronously with the revolution of the X-ray tube, a system for scanning the subject along with the movement of the subject bed in a spiral with respect to a coordinate system positioned about an imaginary axis passing through the subject, and a system for obtaining a reconstructed tomogram of an arbitrary cross-section within a range from a position corresponding to a beginning of the spiral scanning to a position corresponding to an end of the spiral scanning. A method of operating the computerized tomography system is also provided.

CT system for spirally scanning subject on a movable bed synchronized to

An NMR imaging device comprises a circuit for applying a static magnetic field to an object to be examined, a circuit for applying gradient magnetic fields to the object, a circuit for applying radio frequency pulses to the object to cause nuclear magnetic resonance (NMR) in atomic nuclei of atoms constituting tissue of the object, a circuit for detecting the NMR signals thus generated, and means for Fourier-transforming the NMR signals to reconstruct an NMR image. In this NMR imaging device, only a gradient magnetic field in the slice direction is applied to the object without applying a gradient magnetic field in the frequency encode direction and a gradient magnetic field in the phase encode direction, 90 degree and 180 degree radio frequency pulses are applied to the object at predetermined intervals, the NMR signals thus generated are detected and Fourier-transformed, and a static magnetic field intensity is detected from the resultant frequency spectrum to provide a suitable parameter for imaging, thereby providing the NMR image free from any position deviation.

Method for correcting position deviation due to static magnetic field

A CT scanner including a scanning device including (a) device for rotating an x-ray source around an object to be examined, the x-ray source radiating x-rays, while the x-ray source is being rotated, in the form of fan beams covering a region of the object to be examined, and (b) a multielement x-ray detector for detecting x-ray fan beams transmitted through the object to thus collect data around the irradiated object; an arithmetic device for arithmetically reconstructing the distribution of the x-ray absorption coefficients of the object across a measured cross-section from the data; and a display for displaying the distribution where the arithmetic device includes a device for producing data equivalent to data derived from parallel beams not regularly spaced apart from each other from the collected data around the irradiated object, a device for subjecting the produced data to filtering, and a device for correcting inhomogeneity in the data equivalent to data derived from parallel beams not regularly spaced and for back-projecting the image of the distribution.

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Kashiwa, Japan

Hiroshi Nishimura