Abstract: The present invention is directed to an elliptical birdcage coil which reduces time and effort upon manufacturing and production cost, with less variations in performance. There is provided a high frequency coil unit made up of the elliptical birdcage coil having plural capacitors arranged at least on either of the ring conductors and the rung conductors, the capacitance of the plural capacitors being uniform with respect to each conductor type on which the capacitors are placed. In this elliptical birdcage coil, a value of inductance and arrangement of the ring conductors and the rung conductors are determined in such a manner that the capacitance of the capacitors becomes identical with respect to each conductor type on which the capacitors are arranged.

Abstract: Provided is an antenna such as a TEM-type antenna and a microstrip-type antenna that has rung conductors and a shield conductor to electrically connect and use them. A holding member that maintains a shape of the shield conductor is composed by assembling ribs and thin walls. An inner holding member is a structural material. Holes are provided on at least either one of the shield conductor and the holding member adhered thereto or the inner holding member, which can adjoin conductors from the outside of the cylindrical antenna through the said holes during the antenna production.

Abstract: There is provided a technique for securing a large examination space in a tunnel type MRI device without inviting increase of manufacturing cost and without significantly reducing irradiation efficiency or uniformity of the irradiation intensity distribution in an imaging region. Between rungs of a partially cylindrical RF coil, which coil corresponds to a cylindrical RF coil of which part is removed, there are disposed half-loops generating magnetic fields, which are synthesized with magnetic fields generated by loops constituted by adjacent rungs of the partially cylindrical RF coil and rings connecting the rungs to generate a circularly polarized or elliptically polarized magnetic field. Further, high-frequency signals of the same reference frequency having a desired amplitude ratio and phase difference are supplied to the partially cylindrical RF coils and half-loops.

Abstract: There is provided a technique for improving quality of images obtained with an MRI apparatus by using the geometric structures of the conventional RF transmission coil and RF reception coil and without increasing burden on patients or MRI technicians. A conductor loop of an RF reception coil disposed between a subject and an RF transmission coil is used also as a loop for magnetic field adjustment in order to shield or enhance a rotating magnetic field B1 generated by the RF transmission coil. Further, the conductor loop operated as a conductor loop for magnetic field adjustment among the conductor loops constituting the RF reception coil is driven so that inhomogeneity of the rotating magnetic field B1 is reduced.

Abstract: There is provided a technique for securing a comfortable examination space in a tunnel type MRI apparatus without increasing the manufacturing cost of the MRI apparatus and sacrificing performance thereof. In an RF coil provided with a hollow-shaped outer conductive element and a strip-shaped conductive element disposed along the outer conductive element in the axial direction, meander lines constituting the strip-shaped conductive element are disposed at uneven distances from the outer conductive element to secure an internal space. In order to obtain uniform sensitivity at the center of the RF coil, the strip-shaped conductive element is constituted with N of connected meander lines, and length of the strip-shaped conductive element is adjusted so that, in the strip-shaped conductive element resonating at resonance frequency of the antenna, nodes are formed in a number of (M+1)×N?1, wherein M is 0 or a natural number of 1 or larger.

Abstract: In order to provide a technique in which, in the TEM type antenna, the uniformity of sensitivity in the internal portion of the antenna can be maintained with simple configuration, without scarifying the internal space of the antenna, regardless of a size, a shape and a location of a load, and also regardless of locations of the constitutional members of the antenna, the TEM type antenna includes rung conductors which branch out into plural pieces in the middle portion and join into one piece in the two end portions. In other words, the rung conductor having a void space in the middle portion of the rung conductor in the longitudinal direction is provided. The adjacent rung conductors are disposed to be further closer to each other in the middle portion, and to maintain the same distance as that in the related art in the end portion.

Abstract: With an MRI apparatus using a transmission coil having multiple channels, a region desired to be diagnosed is efficiently imaged with high image quality. The MRI apparatus comprises a region setting means for setting a region in an imaging region, of which high quality image is desired to be obtained, as a first region, and an optimization means for determining at least one of amplitude and phase of a radio frequency wave transmitted to each of the multiple channels as a radio frequency magnetic field condition, and the optimization means determines the radio frequency magnetic field condition so that at least one of specific absorption ratio and signal value of a region that generates artifacts is not higher than a predetermined value defined for each, under a uniformity constraint condition that uniformity of radio frequency magnetic field distribution in the first region is not lower than a predetermined value.

Abstract: Manufacture cost and maintenance cost of RF coils of MRI devices are reduced without any limitation concerning size of the coils. By constituting an antenna device for magnetic resonance imaging devices with a cylindrical outer conductor, a looped ribbon-shaped conductor disposed inside the cylindrical outer conductor along the cylindrical surface, and a feed point for transmission and/or reception between the cylindrical conductor and the ribbon-shaped conductor, and disposing the ribbon-shaped conductor so that length thereof can be readily adjusted, there is provided an antenna device for magnetic resonance imaging devices that generates a magnetic field component perpendicular to the central axis of the cylinder at a desired resonance frequency and shows sensitivity without using capacitors and without being imposed any limitation concerning size in the diametral direction of the cylinder.

Abstract: With minimizing extension of imaging time, the B1 non-uniformity reducing effect of RF shimming is maximized for an imaging section of an arbitrary axis direction and an arbitrary position. B1 distributions are measured for only several sections of one predetermined direction, and a radio frequency magnetic field condition that maximizes the B1 non-uniformity reducing effect for an imaging section of an arbitrary direction and an arbitrary position is calculated from the B1 distribution data.

Abstract: In order to provide a technique which can suppress coupling to homogenize the spatial distribution of an RF magnetic field and can improve penetration of the RF magnetic field into the subject, pad-like electric field conductors having a predetermined area are provided outside both ends of a rung conductor as a part of a configuration which forms a loop-like circuit and is driven as an antenna. An antenna device includes a sheet-like conductor, a rung conductor which is arranged at a predetermined distance from the sheet-like conductor, two electric field conductors which are arranged in both end portions of the rung conductor at a predetermined distance from the sheet-like conductor, and connection terminals which are transmission and reception terminals provided in the rung conductor and the sheet-like conductor. The rung conductor and the sheet-like conductor configure a loop circuit which resonates at a preset frequency.

Abstract: There is provided a high-frequency coil of an MRI device, which can easily and highly reproducibly reduce electromagnetic coupling between adjacent surface coils among a plurality of surface coils disposed with intervals. An electromagnetic decoupling coil that can generate a magnetic flux for canceling a magnetic flux generated by one of the adjacent surface coils and interlinking with the other surface coil is disposed between the adjacent surface coils. The electromagnetic decoupling coil is provided with a capacitor, and is tuned by means of the capacitor so that the electromagnetic coupling should be minimized in such a range that the resonance frequency thereof should be lower than the resonance frequency of the surface coils.

Abstract: The present invention is directed to an elliptical birdcage coil which reduces time and effort upon manufacturing and production cost, with less variations in performance. There is provided a high frequency coil unit made up of the elliptical birdcage coil having plural capacitors arranged at least on either of the ring conductors and the rung conductors, the capacitance of the plural capacitors being uniform with respect to each conductor type on which the capacitors are placed. In this elliptical birdcage coil, a value of inductance and arrangement of the ring conductors and the rung conductors are determined in such a manner that the capacitance of the capacitors becomes identical with respect to each conductor type on which the capacitors are arranged.

Abstract: An RF coil is provided with a hollow-shaped outer conductive element and strip-shaped conductive elements disposed along the outer conductive element in the axial direction. The strip-shaped conductive elements are disposed with uneven intervals to secure an internal space at a position where the strip-shaped conductive elements are not disposed. In order to obtain uniform sensitivity at the center section of the RF coil, the strip-shaped conductive elements and the outer conductive element are electrically connected via capacitors of which capacitances are adjusted so that a magnetic field component perpendicular to the center axis should be generated at a desired resonance frequency, and the strip-shaped conductive elements are axisymmetrically disposed with respect to the center axis of the outer conductive element. As a result, a comfortable examination space in a tunnel type MRI apparatus is achieved without increasing the manufacturing cost of the MRI apparatus.

Abstract: There is provided a technique for suppressing increase of SAR without sacrificing sensitivity in RF coils used in MRI apparatuses. The present invention provides an antenna device comprising a sheet-shaped conductor and a ribbon-shaped conductor disposed on the subject side with respect to the sheet-shaped conductor with a predetermined distance from the sheet-shaped conductor. The ribbon-shaped conductor has a meandering shape, and is adjusted so as to resonate at transmission and reception frequencies, and it is constituted so that distance to the sheet-shaped conductor becomes smaller at both end part thereof along the static magnetic field direction compared with the distance to the sheet-shaped conductor at the center thereof. Moreover, the ribbon-shaped conductor is constituted so as to have a smaller width, as the distance to the sheet-shaped conductor becomes smaller.

Abstract: A technique is provided to reserve large examination space in the tunnel type MRI apparatus, without increasing production cost nor reducing significantly irradiation efficiency and homogeneity in an irradiation distribution within an imaging region. The present invention provides an RF coil unit in which four partial cylindrical coils are placed with a gap therebetween in the circumferential direction inside a cylindrical RF shield, in such a manner that two pairs of the partial cylindrical coils are opposed to each other, and magnetic fields produced by the individual partial cylindrical coils are combined, thereby producing a circularly polarized wave field or an elliptically polarized wave field.

Abstract: There is provided a technique for improving quality of images obtained with an MRI apparatus by using the geometric structures of the conventional RF transmission coil and RF reception coil and without increasing burden on patients or MRI technicians. A conductor loop of an RF reception coil disposed between a subject and an RF transmission coil is used also as a loop for magnetic field adjustment in order to shield or enhance a rotating magnetic field B1 generated by the RF transmission coil. Further, the conductor loop operated as a conductor loop for magnetic field adjustment among the conductor loops constituting the RF reception coil is driven so that inhomogeneity of the rotating magnetic field B1 is reduced.

Abstract: There is provided a technique for securing a comfortable examination space in a tunnel type MRI apparatus without increasing the manufacturing cost of the MRI apparatus and sacrificing performance thereof. In an RF coil provided with a hollow-shaped outer conductive element and a strip-shaped conductive element disposed along the outer conductive element in the axial direction, meander lines constituting the strip-shaped conductive element are disposed at uneven distances from the outer conductive element to secure an internal space. In order to obtain uniform sensitivity at the center of the RF coil, the strip-shaped conductive element is constituted with N of connected meander lines, and length of the strip-shaped conductive element is adjusted so that, in the strip-shaped conductive element resonating at resonance frequency of the antenna, nodes are formed in a number of (M+1)×N?1, wherein M is 0 or a natural number of 1 or larger.

Abstract: There is provided a technique for securing a large examination space in a tunnel type MRI device without inviting increase of manufacturing cost and without significantly reducing irradiation efficiency or uniformity of the irradiation intensity distribution in an imaging region. Between rungs of a partially cylindrical RF coil, which coil corresponds to a cylindrical RF coil of which part is removed, there are disposed half-loops generating magnetic fields, which are synthesized with magnetic fields generated by loops constituted by adjacent rungs of the partially cylindrical RF coil and rings connecting the rungs to generate a circularly polarized or elliptically polarized magnetic field. Further, high-frequency signals of the same reference frequency having a desired amplitude ratio and phase difference are supplied to the partially cylindrical RF coils and half-loops.

Abstract: An RF coil for MR Imaging that can change a resonance frequency easily and instantaneously in response to a nuclide to be imaged without exchange and adjustment and that also causes only small lowering of sensitivity. The RF coil has a sub coil for changing a resonance frequency of the transmitting/receiving RF coil for transmitting and receiving an MR signal between itself and a nuclide that is an object to be imaged. The sub coil is equipped with a switch, and at the time of switching-on, shifts the resonance frequency of the RF coil by changing an inductance value of the RF coil in a noncontact manner using inductance coupling.

Abstract: An MRI apparatus comprises a waveform controlling means for calculating a radio frequency pulse and applying the pulse to an irradiating means, and the waveform controlling means reads out a radio frequency pulse waveform vector from a first memory means which memorizes multiple radio frequency pulse waveform vectors, calculates a simulated irradiation pattern, and calculates a radio frequency pulse waveform which gives the minimum value of weighted sum of squares of differences of absolute values and squares of differences of phases for an ideal irradiation pattern and the simulated irradiation pattern. An RF pulse waveform showing superior ideal irradiation pattern reproducibility and providing reduced power of the RF waveform is formed, and safety of MRI subject is improved by performing imaging using such an RF pulse.