WO2003075757A1 - Dispositif a aimant et imagerie par resonance magnetique utilisant ledit dispositif - Google Patents

Dispositif a aimant et imagerie par resonance magnetique utilisant ledit dispositif Download PDF

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Publication number
WO2003075757A1
WO2003075757A1 PCT/JP2003/002951 JP0302951W WO03075757A1 WO 2003075757 A1 WO2003075757 A1 WO 2003075757A1 JP 0302951 W JP0302951 W JP 0302951W WO 03075757 A1 WO03075757 A1 WO 03075757A1
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WO
WIPO (PCT)
Prior art keywords
space
annular
magnet device
magnetic field
circumferential direction
Prior art date
Application number
PCT/JP2003/002951
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English (en)
Japanese (ja)
Inventor
Shigeru Kakugawa
Tsuyoshi Wakuda
Yoshihide Wadayama
Hirotaka Takeshima
Takeshi Yatsuo
Kenji Sakakibara
Original Assignee
Hitachi, Ltd.
Hitachi Medical Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2002069952A external-priority patent/JP2003265435A/ja
Priority claimed from JP2002069656A external-priority patent/JP4040334B2/ja
Application filed by Hitachi, Ltd., Hitachi Medical Corporation filed Critical Hitachi, Ltd.
Publication of WO2003075757A1 publication Critical patent/WO2003075757A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/387—Compensation of inhomogeneities
    • G01R33/3873—Compensation of inhomogeneities using ferromagnetic bodies ; Passive shimming
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/3806—Open magnet assemblies for improved access to the sample, e.g. C-type or U-type magnets

Definitions

  • the present invention relates to a magnet device in which a pair of static magnetic field sources face each other across an imaging space, and a magnetic resonance imaging (hereinafter abbreviated as MRI) device using the magnet device.
  • MRI magnetic resonance imaging
  • a magnet device described in International Publication No. WO 99/27851 (MAGNET APPARATUS AM) MRI APPARATUS is known as a superconducting iron for an open type MRI device using the former method.
  • This magnet device is composed of two magnet assemblies that face each other across the shadow space, which is the shadow area of the MRI image.
  • Each magnet assembly has a plurality of superconducting coils, and is arranged substantially axisymmetrically with respect to the central axis of the device.
  • Superconducting coil The main coil of the coil has a positive polarity and a negative polarity coil alternately arranged, and can generate a highly uniform field while being a compact magnet.
  • magnet devices using the latter method include, for example, Japanese Patent Application Laid-Open No. 5-2511231 (proximity magnet for magnetic I imaging) and Japanese Patent Application Laid-Open No. 8-8787 (magnet facing type permanent magnet magnetic circuit). What has been described is disclosed.
  • the magnet device for the MR device urn from the source of difficulty is introduced into the HIS, for example, to the shooting space via the annular protrusion and the annular projection provided on the outer periphery thereof.
  • the tomographic image of the subject inserted into the imaging space is obtained using the tilted-field coil and the high-frequency coil.
  • a method that is generally used for a magnet device using a shimi to homogenize an expansion space is to form an uneven surface on a surface of the shimi space on the side of the space.
  • two opposing magnets are magnetically supported by a column made of a magnetic material in order to suppress the leakage magnetic field.
  • FIG. 16 shows a schematic structure of a magnet device (hereinafter, referred to as a first conventional example) disclosed in Japanese Unexamined Patent Publication No. 5-252131.
  • Fig. 16 shows a schematic side view of the entire magnet device.
  • the upper and lower pipes 102 a and 102 b are vertically opposed to each other with the imaging space 10 interposed therebetween.
  • a ring is formed on the side of the outer periphery of the upper and lower magnetic poles 102a, 102b that faces the imaging space 10.
  • 3 ⁇ 4B 106 a 106 b is provided.
  • the magnet device 100 in the first row f »i is divided into two sections, one on the side facing the shooting space 10 and the other on the upper and lower annular sections 106a and 106b.
  • Magnetic bodies 108 and 109 are arranged, and the arrangement of the discrete magnetic bodies 108 and 109 attempts to cancel out the non-rotational field.
  • the ring! The magnetic material 108, 109 is localized in the direction of rotation on the surface of the dog protrusion 106a, 106b, so that the desired magnetic field that cancels out the above non-rotational filthy field is generated.
  • FIG. 17 shows a plan view of the second annular separation.
  • the width of the annular projection 1 12 is partially changed continuously, and a plurality of notches 1 1 4, 1 1 and 5 are provided.
  • an object of the present invention is to provide a magnet device for an MRI device capable of forming a clear image by removing an irregular magnetic field in a »field in a space.
  • the magnet device is a magnetic device that generates a static magnetic field in the expansion space through a pair of brushes arranged opposite to each other with a space between them and a magnetically connected to the fabrics.
  • Field source an annular separator made of a magnetic material protruding in an annular shape on the opposite surface side of the three-stage shu, and at least one master that directly or indirectly establishes the space between the stalks.
  • the amount of at least a part of the magnetic body in the circumferential direction of the annular projection is increased or decreased.
  • the amount of magnetic material in the radial cross section is increased or decreased in the circumferential part or in the ⁇ region of the annular ⁇ which is placed opposite to the space. It is possible to increase or decrease the amount of magnetic flux gathering in the corresponding area of space and increase or decrease the magnetic field j. For this reason, the irregular magnetic field is canceled by appropriately determining the circumferential area of the annular protrusion and the increase / decrease of the magnetic material in accordance with the irregular magnetic field area and the magnetic field strength generated in the imaging space. It is possible to homogenize the magnetic field in the space. As a result, clear MR images are obtained.
  • the magnet device of the present invention generates a thigh field in the if3i cascade space through a pair of flips arranged opposite to each other with the space interposed therebetween and magnetically connected with the 3 knots.
  • a thigh field source a ring dog ⁇ made of a magnetic material protruding in an annular shape on the opposite surface side of the knitting picture, and at least one directly or indirectly supporting the space between the it paintings
  • magnetic support a magnet device provided with a support made of a magnetic material (hereinafter referred to as “magnetic support”)
  • the irregularity ⁇ generated in the “self” space due to the 3 magnetic support is removed, and the magnetic field in the knitting space is removed.
  • an irregular magnetic field due to the magnetic column is generated at a position close to the magnetic column in the 3 ⁇ 41 ⁇ space, so that an irregular field in the imaging space is generated.
  • the magnetic field in the ⁇ ⁇ space is made uniform by increasing or decreasing the amount of magnetic material in the radial cross section of at least a part of the circumferential direction of the annular projection facing the region to cancel the above-mentioned field. .
  • the amount of the magnetic material in at least a part of the radial cross section in the circumferential direction of the knitted three annular projections is small.
  • the amount of the magnetic material is gradually increased or decreased along the circumferential direction from a portion to a large amount of the magnetic material, to the portion, or vice versa.
  • At least a part of the annular protrusion in the circumferential direction has a smaller amount of the magnetic material in a cross section in the judgment direction along the circumferential direction, from a small number of portions to a large number of portions, or from a large portion to a small amount.
  • the magnetic field bow changes gradually in at least a part of the space in the circumferential direction of the space by returning to the arrogant space by circulating the ring Can be formed. Therefore, when an irregular magnetic field having the above distribution is generated in space, the present invention is effective in canceling this.
  • the cross-sectional area of at least a part of the annular projection in the circumferential direction in the radial direction is sequentially increased or decreased along the circumferential direction. It is.
  • Simply called width the radial width of at least a part of the j
  • height dimension in the direction perpendicular to it At least one of the laws (hereinafter simply referred to as height) is gradually increased or decreased along the circumferential direction.
  • the magnetic field in the imaging space can be made uniform by increasing or decreasing at least one of the width or the height of the section in the judgment direction of the annular shape, as in the case of the embodiment.
  • one or more annular weaves having a small outer diameter are arranged substantially concentrically on the inner peripheral side of the knitting ring ⁇ . is there.
  • the small-diameter annular ring is arranged on the inner side of the large-diameter annular separation, so that the annular protrusions are arranged both in the circumferential direction and in the radial direction. Not only the outer peripheral part but also the inner peripheral part can be accurately canceled out, so that the magnetic field in the imaging space can be accurately uniformed over a wide range.
  • the height of at least a part of the circumferential side end surface of the knitted ring dog projection in the circumferential direction is increased or decreased, It has a corrugated shape.
  • the height of at least a part of the end face in the circumferential direction of the annular projection is increased or decreased. Since the dog is a dog, the cross-sectional area of the section in the ⁇ ⁇ direction also changes in the wavy type I dog, and the area of the dog facing the same part of the inflated space along the circumferential direction ⁇ Generate a distribution. Therefore, if a field of »J ⁇ dog is generated along the circumferential direction in the ⁇ space facing the above, it can be canceled and the magnetic field can be made uniform. be able to.
  • the magnetic field of the knitting space is further homogenized.
  • at least a part of the IMS annular projection in the circumferential direction is constituted by a plurality of annular members each having at least one of a sectional area, a width, and a height of a radial cross section thereof.
  • the circular ring member is sequentially ⁇ ⁇ ⁇ from small to large in IE cross-sectional area, width, or height, or vice versa, and the inner circumferential surface, outer circumferential surface, And at least one of the end faces on the space side is attached to the stairs I dog.
  • the annular protrusion is composed of a plurality of annular members having at least one of different cross-sectional areas, widths, and heights in the radial cross section, the annular protrusion is divided into small annular members, and ffi: By doing so, the processing becomes easier and the cost can be reduced.
  • the annular ⁇ member is successively arranged from the smallest in cross-sectional area, width and height in the radial cross section, and the inner, outer, and end surfaces of the annular member are stepped. Therefore, by taking those envelopes, it is possible to approximate the inner peripheral surface, outer peripheral surface, and end surface of the annular ⁇ with the woven spring.
  • one pair of the three knitting field generating sources is arranged on the back side of the cafeteria, facing each other across the three knitting space.
  • the pair of cloud-prone sources arranged opposite each other has a source of limestone and a vine that is placed facing the space.
  • H In a magnet device in which one or more ring dogs protruding toward the space are arranged, in order to homogenize the magnetic field in the self-return space, at least one radial section of the The cross-sectional area is changed periodically in the circumferential direction. In this configuration, since the cross-sectional area of the radial cross section of the annular projection changes periodically in the circumferential direction, the magnetic field bow distribution due to this annular ⁇ and ⁇ gathering in space ⁇ is also periodic in the circumferential direction.
  • the pair of rinsing place generating sources disposed opposite each other has a power source and a magnetic pulp disposed facing the water fountain space, respectively.
  • One or more dogs protruding toward the crescendo space side are arranged.
  • At least one of the above-mentioned rings is composed of a plurality of ring attachments. The cross-sectional area of Wei Yongzhu's cross section is periodically changed in the circumferential direction.
  • the annular separation is composed of a plurality of annular members, and the sectional area of the radial section of the annular protrusion is periodically changed in the circumferential direction.
  • the pair of opposing sources arranged in opposition each have a power source and a power source and a power source facing the space.
  • the width of at least one radial section of the loop is used to equalize the magnetic field in the expansion space. Is periodically changed in the circumferential direction.
  • the width dimension of the radial cross section of the annular projection changes periodically in the circumferential direction.
  • the cross sectional area also changes in the circumferential direction. , So that the same effect as mi 3 can be obtained.
  • the pair of »t easy-generating sources arranged opposite each other has a power source and a ⁇ -jiru arranged facing the expansion space, respectively.
  • at least one annular protrusion protruding toward the so-called 3 ⁇ inflated space side is arranged, and at least one of the annular ⁇ is constituted by an annular ⁇ , the radial direction of the annular projection member according to the above 3)
  • the width of the cross section is changed periodically in the circumferential direction.
  • the ring projection is composed of a plurality of annular ⁇ 3 members, and the width of the section in the ⁇ direction of the annular projection is periodically changed in the circumferential direction, so that the sectional area of the annular projection is also circular. It changes periodically in the circumferential direction, and the fruit as described in Chapter 3 can be obtained.
  • the pair of easy-to-generate sources disposed opposite each other includes a source of lime and a vine that is disposed facing the bulging space.
  • Knitting ⁇ ⁇ ⁇ ⁇ In a magnetic device in which one or more rings projecting toward the space side are arranged, at least one radial cross section of the knitting ring protrusion is used in order to uniformize the magnetic field in the ⁇ 3 ⁇ space. Is periodically changed in the circumferential direction.
  • the pair of thigh field generating sources disposed opposite each other has a force source and a squeezer disposed facing the space, respectively, and the WM pole has an expanded space side.
  • at least one of the annular protrusions is composed of a plurality of annular members, and a radial cross-section of the annular protrusion member in 3 to 1 is provided. Is periodically changed in the circumferential direction.
  • the annular ⁇ 3 is composed of a plurality of annular ⁇ members, and the height of the cross section in the direction in which the annular protrusion protrudes is periodically changed in the circumferential direction. It changes periodically depending on the direction, and the same effect as knitting can be obtained.
  • the pair of Ryoba sources arranged opposite each other has a mosquito source and a pair of dragons arranged facing the space, respectively.
  • One or more annular protrusions protruding toward the space side are arranged.
  • At least one of the annular ⁇ is composed of a plurality of annular attachments.
  • At least one of the inner envelope connecting the surfaces and the outer envelope connecting the outer peripheral surfaces in the radial direction is periodically changed in the circumferential direction.
  • the annular member is composed of a plurality of annular S members, and the inner or outer envelope formed by the radially inner or outer peripheral surface of the annular projection member has a periodic shape in the circumferential direction. Is changing.
  • the width dimension of the cross section in the ⁇ f ⁇ direction of the annular projection having these envelopes as the inner or outer peripheral surface changes periodically in the circumferential direction, so that the cross section in the judgment direction of each annular ⁇ member itself is obtained.
  • the width dimension of FjfB is approximately the same, an interaction result similar to fijfB can be obtained.
  • the pair of basket field generating sources disposed opposite each other includes a joy source and a squeezer arranged facing the squash space, respectively. Knitting One or more annular gaps protruding toward the inflated space side are arranged.
  • a magnet device where at least one of the annular rings is composed of a plurality of annular ⁇ The envelope connecting the end faces facing the an space is changed periodically in the circumferential direction.
  • the annular separation is made up of a plurality of ring members, and the envelope formed by the end faces of the annular protrusion members facing the imaging space is related to the circumferential direction. And change periodically. As a result, the height dimension of the ⁇ -direction cross section of the ring-shaped protrusion with the end face of this fountain changes periodically in the circumferential direction. Approximately the same change produces the same effect as knitting.
  • the number of knitting annular separation members per knitting annular weir is within 60. .
  • the annular projection is composed of up to 60 annular projection members per one piece, the labor and cost required for processing and assembling the annular projection member are more than the cost of integrally forming the annular weed. In addition, it is easy to assemble and adjust to the place where the ring is tolerated, and it is possible to obtain the effect of dividing into the ring.
  • the knitting 3 cross-sectional area of the ring 3 or the knitting width, or the knitting 3 height, or the knitting 3 can be varied in a sinusoidal function in the circumferential direction. I'm doing it.
  • the cross-sectional area, width, height, or envelope of the annulus varies sinusoidally with respect to the circumferential direction, and thus varies sinusoidally along the circumferential direction of the 31 ° space.
  • a non-fiber field with a magnetic bow key distribution such as
  • the cross-sectional area of the annular protrusion, or the width, or the height of the knit, or the envelope spring is an integer of 1 or more with respect to one circumference in the circumferential direction. Is changed sinusoidally according to the mode m.
  • the cross-sectional area, width, height, or envelope of the annulus varies sinusoidally with a mode m that is 1 or more for one week in the circumferential direction, so that the circumference of the imaging space is Along the direction, it is possible to cancel out the fact that the magnetic field has a distribution that varies with the sine function of mode m.
  • the cross-sectional area of the annular projection, or the width, the height, or the envelope is two or more with respect to one circumference in the circumferential direction. It is changed by the superposition of the sine function by the mode m which is one or more of which is different from.
  • the cross-sectional area, width, height, or envelope of the ring is varied by the superposition of sine functions in mode m, where the envelope is two or more different integers of one or more over one circumference. Because of this, it is possible to cancel an irregular magnetic field having a magnetic field intensity distribution that changes in a manner that is a superposition of sine functions of multiple modes along the circumferential direction of the space.
  • At least two or more knitted annular protrusions are arranged cross-sectional areas, or ⁇ ! 3 widths, or self-heights, or the fountain is formed in a circumferential direction.
  • one or more different modes are changed sinusoidally by ⁇ ⁇ , ⁇ , etc.
  • the cross-sectional area, width, height, or envelope of at least two or more annular weaves varies in a sinusoidal fashion in the mode corresponding to each annular protrusion, each in a circumferential direction.
  • the magnetic field bow changes both in the circumferential direction and in the radial direction such that it changes by superposition of sine functions of different modes along the circumferential direction corresponding to each annular protrusion in the return space. It is possible to negate the disadvantage of having a boat distribution.
  • the magnet device of the present invention there is further provided at least one column that couples the pair of static magnetic field sources or the pair of knits with each other c. Since the static TO sources or a pair of magnetic transducers are connected by one or more columns, the magnetic poles are supported without significant deformation, and a large open space is created between the magnetic poles in the imaging space. Property is obtained.
  • the third column is further composed of a ferromagnetic material. ing.
  • the strut supporting the gap between the difficult-field sources or the space is made of a ferromagnetic material.
  • the return path of the magnetic flux generated for generating the magnetic field can be obtained, and the leakage magnetic field to the outside of the device can be reduced.
  • At least one columnar ferromagnetic material that magnetically couples between one generation source of the 31 pairs of knits or ⁇ of the 31 pairs of knits to form a magnetic circuit exists. I do.
  • the magnetomotive force source is a superconducting coil. In this configuration, a uniform magnetic field can be formed in the space with a high magnetic field bow ffi by the magnetomotive force source composed of a supercoil, so that a clear MR image with high resolution can be obtained.
  • the 3rd magnetic force source is a normal conducting coil.
  • the magnetomotive force source is a normal conducting coil, cooling of the coil is not required, and the manufacturing cost of the device and the cost of the fiber are reduced.
  • the knitting magnetomotive force source is a permanent magnet.
  • the magnetomotive force source is a permanent magnet, cooling of the coil and coil power are not required, so that maintenance of the device is facilitated and the maintenance cost of the device is reduced.
  • FIG. 1 is a diagram showing the right to complete leakage of a first example of a magnet device according to the present invention. It is.
  • Fig. 2 is a diagram showing the upper ring in Fig. 1 together with the coordinate system including the Ki-swelling space.
  • FIG. 3 is a diagram for explaining generation of an irregular magnetic field by the magnet device of the MRI device.
  • FIG. 4 is a plan view illustrating a case where the irregular magnetic field of FIG. 3 is canceled by the annular projection of the present invention.
  • FIG. 5 is a characteristic diagram showing the relationship between the non-field shown in FIGS. 3 and 4 and the ring weir.
  • FIG. 6 is a schematic sectional view of a magnet device according to the present invention.
  • FIG. 1 is a diagram showing the right to complete leakage of a first example of a magnet device according to the present invention. It is.
  • Fig. 2 is a diagram showing the upper ring in Fig. 1 together with the coordinate system including the Ki-swell
  • FIG. 7 is a diagram for explaining generation of an irregular magnetic field by the apparatus of FIG.
  • FIG. 8 is a structural view of a ring used in the apparatus of FIG.
  • FIG. 9 is a diagram showing a third difficult example of the magnet device according to the present invention.
  • FIG. 10 is a plan view of an annular projection of a fourth embodiment of the magnet device according to the present invention.
  • FIG. 11 is a plan view of an annular projection of a fifth embodiment of the magnet device according to the present invention.
  • FIG. 12 is a perspective view of a lower annular protrusion of a sixth embodiment of the magnet device according to the present invention.
  • FIG. 13 is a plan view of the annular projection used in FIG. FIG.
  • FIG. 14 is a plan view of the annular projection of the seventh embodiment of the magnet device according to the present invention.
  • FIG. 15 is a schematic structural view of an eighth example of the sickle of the magnet device according to the present invention.
  • Figure 1 ⁇ is a seismic cross section of the magnet system in Agata.
  • FIG. 17 is a plan view of an annular separation used in the apparatus of FIG.
  • FIG. 18 is an explanatory diagram of an MRI device using the magnet device according to the present invention. Best mode for making invention
  • FIG. 18 is a block diagram for explaining the overall configuration of the MRI apparatus using the magnet apparatus of the present invention.
  • This MRI device is used to obtain a tomographic image of the subject using the magnetic resonance phenomenon.
  • the magnet device 18 1 is composed of one of permanent magnets, normal-electrode ⁇ stones, and superconducting stones arranged in a certain space around the subject 18 8.
  • a uniform basket field is generated around the area in the direction away from the ft or in a direction perpendicular to the body axis of the polar body.
  • ⁇ Circumferential field generating means 18 2 include tilting field coils 1 89 wound in three axial directions of X, Y and ⁇ and tilting power sources 1 8 10 for magnetizing each of these coils Consists of
  • the tilting fiber field power supply 18010 magnetizes each of the coils to transfer tilt reverberation in the X, ⁇ , and ⁇ directions to the subject 188. Apply.
  • the ⁇ ⁇ ⁇ cross section of the subject 188 is changed by 1 ⁇ ⁇ ⁇ depending on how to add the tilt reverberation.
  • the transmission system 18 3 consists of a high-frequency oscillator 18 11, a modulator 18 12, a high-frequency amplifier 18 13 and a high-frequency, irradiation coil 18 14.
  • the output from the high-frequency oscillator 18 11 After the amplified high-frequency pulse is amplified by the high-frequency amplifier 1813, it is supplied to a high-radiation coil 181, which is installed in close proximity to the subject 188, to irradiate the body with electromagnetic waves.
  • the receiving system 18 4 consists of a high-frequency receiving coil 18 15, a receiving circuit 18 16 and an AZD variable 18 17, and irradiates from the high-frequency coil 18 14 of the transmitting system 18 3.
  • the raw NMR signal from the nucleus of the carcass prey 188 caused by the generated electromagnetic waves The signal is detected by the reception coil 18 15, input to the A / D converter 18 17 via the reception circuit 18 16, converted into a digital signal, and further in accordance with an instruction from the sequencer 18 6. Sampled at timing The signal is sent to signal system 185 as an I »de overnight.
  • the signal input / output system 185 includes a CPU 187 that performs a Fourier transform on the collected data and controls the sequencer 186.
  • the correction unit of the present invention includes a correction unit of the present invention.
  • the signal device that performs the necessary functions to perform the functions of the device 18 18 18 stores the program of the image analysis processing over time and the sequence of the specified measurement, the parameters used for the execution of the program, and the parameters used for the execution.
  • the sequencer 186 repeatedly generates a slice fiber code, a phase encode, a frequency encode, and a high-frequency magnetic field pulse in a predetermined norr sequence, while the slicer code, the phase encode, and the frequency encode are generated at the legs of the CPU 187. It sends various instructions necessary for acquiring tomographic image data of the subject 188 to the gradient magnetic field generating means 182, the transmitting system 183, and the receiving system 184.
  • the operation unit is composed of a trackball, mouse, keyboard, etc., and inputs control information for signal S-185.
  • FIG. 1 shows an extra view of the entire structure of the first male example of the magnet device according to the present invention.
  • the magnet device 1 of the present embodiment includes upper and lower sources 2 a and 2 b vertically opposed to each other across an imaging space 10, and the static magnetic field sources 2 a and 2 b A uniform vertical field is formed in the photographing space 10 by b.
  • the center of the shooting space 10 is the origin 0
  • a coordinate system is set with the Z axis as the direction, the X axis as the left and right direction, and the Y axis as the front and rear direction.
  • the upper and lower orchids 4a and 4b are woven on the sides of the upper and lower thigh field sources 2a and 2b, respectively, facing the space 10.
  • the upper and lower rings 6 a and 6 b made of a magnetic material protrude in an annular shape toward the shooting space 10.
  • the upper and lower ⁇ field sources 2 a and 2 b are arranged on the left and right sides of the imaging space 10 by ferromagnetic supports (hereinafter, also referred to as bow magnets f raw supports) 8 a and 8 b. It is mechanically supported and magnetically coupled.
  • Sources 2 a, 2 10 and main 8 &, 8 b form a magnetic circuit together with ⁇ ⁇ 4 a, 4 b, i ⁇ 36 a, 6 b, and are generated in «space 10
  • the return path of the magnetic field is reduced, so that the leakage magnetic field force of the magnet device 1 is reduced.
  • the «generated by the upper and lower static sources 2 a and 2 b travels to the upper space 10 through the upper and lower ⁇ 4 a, 410 ⁇ -shaped ⁇ 6 &, 6 b A basket place is formed here.
  • it is necessary to provide irregularities on the surface facing the photographing space 10 of the sword 4a, 4b, or to make the annular protrusions 6a, 6b The height of the sword is changed, and the arrangement of the rings 4a and 4b and the rings t3 ⁇ 43 ⁇ 46a and 6b is changed.
  • FIG. 2 is a complement diagram showing the upper annular projection 6 a in FIG. 1 together with a coordinate system including the ⁇ 1 ⁇ space 10.
  • the ring-shaped ⁇ 6 is arranged on the outer periphery of the side facing the ⁇ ! 3 ⁇ 4 space 10 of the ⁇ 4, but since it is a main part of the present invention, it is located above the entire structure of the magnet device 1 in FIG. Only the ring ⁇ 6a is extracted and shown in Fig. 2 together with the coordinate system.
  • the origin 0 of the coordinates is the center of the ii ⁇ space 10
  • the Z axis is the facing direction of the two difficult-field sources 2 a and 2 b in FIG. It is also the direction of the static magnetic field formed at zero.
  • the choice of X and ⁇ axes is arbitrary.
  • the X axis is the horizontal direction
  • the ⁇ axis is the barley direction
  • the rotation ⁇ about the ⁇ axis is measured counterclockwise from the X axis. The same applies to the following embodiments unless otherwise specified.
  • the upper annular separation 6a is arranged above the expanded space 10 in the circumferential direction with the Z axis as the central axis.
  • the cross-sectional area S of the cross section (hereinafter referred to as the judgment direction cross section) 7 at the turning angle ⁇ is changed along the circumferential direction.
  • S is increased or decreased along the circumferential direction so as to remove the irregular magnetic field in the ⁇ space 10.
  • the range in which the cross-sectional area S increases / decreases may be a partial area in the circumferential direction or the entire area.
  • the magnetic material in the circumferential direction of the ring 3 ⁇ 436 is used in this example.
  • the distribution in the ⁇ ⁇ space 10 can be changed by passing through the annular protrusion 6 and leading to the ⁇ space 10. Therefore, in response to the distribution of the irregular magnetic field in the space 10, the irregular area S is increased or decreased along the circumferential direction with respect to the Si value so as to eliminate the irregularity so as to eliminate the irregularity.
  • the magnetic field can be canceled, and the ⁇ uniformity in the key space 10 can be increased.
  • » ⁇ is used as» ⁇ , but flat: 3 ⁇ 4 value or minimum value may be used.
  • the axial cross section 7 of the annular separation 6 is For a rectangle il ⁇ r consisting of a width D and a height H parallel to the Z axis, the cross-sectional area S at a rotation angle ⁇ is determined by the width D and the height H. Accordingly, in order to change the cross-sectional area S along the circumferential direction, one or both of the width D and the height ⁇ of the cross-section 7 in the ⁇ ⁇ direction are changed along the circumferential direction. It is also done by
  • the width D in the ⁇ f ⁇ direction of the circumferential section 7 of a part of the ring 6 in the circumferential direction is changed along the circumferential direction to eliminate the ease of the shooting space 10. .
  • the irregular magnetic field is generated near the ferromagnetic support 8a, 81) of the imaging space 10, that is, mainly in the X-axis direction.
  • the width D of the region of the annular protrusion 6 in the X-axis direction is changed. Since a positive irregular magnetic field is usually generated in the X-axis direction, in order to remove this, in FIG. 2, the width D of the ring! In this way, the contribution of TO to the shooting space 10 will be reduced, and the hot water will be canceled out.
  • the width D of the annular projection 6a is small in the X-axis direction, that is, D1 at the rotation angle of ⁇ 20 °, D3 at the rotation angle of 180 °, and D3 at the rotation angle of 180 °. 3 ⁇ 4 ⁇ Value D ⁇ (M). From the minimum width Dl, D3 to: ⁇ Width DO, the width D is gradually increased, but the values of the minimum width Dl, D3, the area of the narrow width D and the width D The way of spreading is determined according to the size of the magnetic field bow of the magnetic field in the cucumber space 10, the range of the region where the irregular magnetic field is generated, and the like. In other words, the width difference (DO-Dl) and (DO-D3) should be almost proportional to the value of the irregular magnetic field key, and the width D should be narrow and the area should be almost the same as the irregular magnetic field generation area. It is done.
  • the range in which the width D of the ring 6 is changed is only a part of the circumferential direction corresponding to the region where the irregular magnetic field is generated in the normal space 10, but the change range of the width D is circular. It may be spread over the entire area in the circumferential direction. In the latter case, It is possible to cancel not only low-order irregular fields but also high-order irregular brains.
  • the sources 2 a and 2 b are arranged opposite to each other with the space 10 in the vertical direction, with the upper and lower orchids 4 a and 4 b on the back.
  • the present invention is not limited to this, but the thigh field sources 2a and 2b are arranged in different places, and the phenomena generated in the different places are guided to the squeezers 4a and 4b by a magnetic circuit.
  • the present invention holds even when a static magnetic field is formed in the space 10 by the magnetic flux obtained by ⁇ i of the 44a, 4b and the ring 3 ⁇ 4S6a, 6b.
  • a pair of ⁇ The swords 4 a and 4 b are arranged facing each other, and the ⁇ m generated by the difficult-field sources 2 a and 2 b is ⁇ 4 4 a, regardless of the location of the thigh field sources 2 a and 2 b.
  • the present invention is established in a case where the hot water is formed in the ⁇ space 10 by being guided to the ⁇ space 10 via 4b.
  • ⁇ 4 a and 4 b are arranged in the vertical direction, but the arrangement direction of the lanterns 4 a and 4 b is not limited to this, and other directions such as the horizontal direction The present invention holds.
  • FIG. 3 is a diagram for explaining the generation of the non- ⁇ field by the magnet device of the MRI device.
  • FIG. 4 is a plan view illustrating the case where the non- ⁇ field of FIG. 3 is canceled by the annular projection of the present invention. Is a special order diagram showing the relationship between the irregular magnetic field shown in FIGS. 3 and 4 and the ring.
  • Fig. 3 (a) shows an example of the field generated by the ferromagnetic material in the water space
  • Fig. 3 (b) shows an example of the distortion of the tomographic image of the subject in the irregular imaging space.
  • Fig 3 (a) is a cross-sectional view of the magnet device passing through the center 0 of the expansion space 10. In this figure, in this example, two strong magnets are arranged in the horizontal direction (X-axis direction) of the water supply space 10. Individual books Main 1 2a, 1 2b are arranged.
  • a uniform #M is usually formed by the upper and lower static magnetic field sources and the magnetic poles.
  • an irregular magnetic field is generated in a uniform static magnetic field due to the arrangement of the two columns 12a and 12b.
  • the bow magnetic field f Biological body The irregular magnetic field generated by the supports 12a and 12b is large near the poles 12a and 12b, and the legs are separated from the poles 12a and 12b. It gets smaller as the distance increases. In this way, the unsavory ground created by the two pillars 1 2a and 1 2 is a superposition of the contributions from 3 ⁇ 43 ⁇ 4 12 a and 12 b, respectively.
  • the magnetic field distribution is as shown in FIG.
  • Fig. 3 (a) the state of the irregular magnetic field created in the space 10 of the columns 12a and 12b is indicated by its «bow J degree ⁇ springs 14a, 14b, and 14c.
  • Isoquan spring 14a near poles 12a and 12b shows a high magnetic field bow key.
  • Isokonsen spring 14c near center 0 shows a low bow boat.
  • the hatched areas Fl and F3, which are surrounded by the line 14a, are areas with high irregular expansion (hereinafter referred to as high irregular magnetic field areas).
  • the irregular TO ⁇ JS in the high magnetic field regions F 1 and F 3 can reach several hundreds Ppm.
  • FIG. 3 (b) shows a tree inserted into the return space 10; ⁇ for example, a tomographic image 16 of the head.
  • this tomographic image 16 emphasizes only image distortion.
  • the tomographic image 16 of the head is obtained by arranging the head of the264 body on the thigh of the cucumber space 10 and performing the tilt fiber coil and the high frequency coil.
  • Fig. 3 (a) if there are highly irregular magnetic field regions F1 and F3 that distort the uniform thigh field in the imaging space 10 as shown in Fig. 3 (a), the tomographic image of the head 1 6 to Causes image distortions Gl and G3 at positions as shown in Fig. 3 (b). That is, in the high-fiber field regions Fl and F3, the image 16 of the head is distorted or the image distortions Gl and G3 occur.
  • the high magnetic field regions F 1 and F 3 in the expansion space 10 are generated due to the columns 12 a and 12 b made of a ferromagnetic material, and are formed in regions near the columns 12 a and 12 b. . Then, in the high irregular magnetic field regions F 1 and F 3, the image is deformed or becomes unclear in the obtained tomographic image 16, and image distortions Gl and G 3 are generated. Associated with the venue.
  • FIG. 4 is a plan view showing the relationship between the ring and the column according to the present invention.
  • the annular spaces 20a and 20b of the present invention are arranged above and below the imaging space 10, and two bows, magnetic injection and main columns 12a and 12b are arranged on the left and right sides.
  • the irregular magnetic field of the fi ⁇ space 10 is changed by changing the cross-sectional area of the cross section in the crosswise direction of Jigwei 20a, 2 Ob (here, changing the width D in the judgment direction). Trying to counteract.
  • FIG. 3 (a) there are high irregular magnetic field regions F1 and F3 in the horizontal direction (X-axis direction) where the columns 12a and 12b exist as the irregular magnetic field of the space 10.
  • the widths D1 ⁇ D3 in the radial direction in the X-axis direction regions 22a, 22b of the annular 20a, 2Ob facing the highly irregular easy regions Fl, F3 are the width D0 (MM ) Make it narrower. That is, while the width D of the conventional annular protrusion is the DO directly from the base i over the entire circumferential direction, in the present invention, the width D of the regions 22a and 22b opposed to the highly irregular »regions F1 and F3 is reduced.
  • the values are smaller than the reference value DO, that is, D1, ⁇ 3.
  • DO the reference value
  • the change in the width D of the annular ⁇ 20a, 20b depends on the magnetic field strength distribution of the irregular magnetic field in the high irregular regions F1, F3 of the expansion space 10, and in the Y-axis direction over the regions 22a, 22b.
  • the width is gradually narrowed from the width D0 to the minimum widths Dl and D3 in the X-axis direction, and is gradually increased to return to the width DO in the Y-axis direction.
  • the way of changing the width D in the change regions 22a and 22b of the width D is as follows: the high irregular magnetic field regions F1 and F corresponding to the decreasing amount of the width D along the circumferential direction of the annular protrusions 20a and 20b. It is performed so as to be almost proportional to the magnetic field bow in the field 3 in FIG.
  • the field bow of the irregular magnetic field in the highly irregular «regions Fl and F3 (+3) is the decrease of the field bow « value due to the width D of the annular ⁇ 20a, 2 Ob being reduced to the width Dl and D3 ( -3) cancels out, resulting in a uniform ⁇ -field.
  • FIG. 5 is a special order diagram showing the relationship between the irregularities and the annular projections.
  • the horizontal axis represents the rotation angle ( ⁇ with the X axis as 3 ⁇ 4 ⁇ )
  • the vertical axis represents the circumferential magnetic field f of the portion of the imaging space 10 where the irregular magnetic field is generated.
  • the horizontal line 24 indicates the magnetic field key f 0 in the uniform region of the space 10.
  • the broken line 26 indicates the amount of change in the magnetic field bow key in the imaging space 10 due to the change in the width D of the annular protrusions 20a and 20b.
  • the value of the difficult bow key of the dashed line 26 is represented by the straight line (0) on the f0 line. In the areas Dl and D3 where the width D is set to the widths Dl and D3, a correction magnetic field having negative magnetic field strength values dl and d3 is generated.
  • the solid line 25 indicates the region 1 and the irregularity of F 3 flfl and f 3 are corrected by the correction magnetic fields 11 and d 3 in the regions 01 and 03 of the broken line 26. , A uniform magnetic field of the magnetic field bow f 0 is obtained. For this reason, according to the present invention, the easily irregularities in the water space 10 are removed and the magnetic field is made uniform, so that a clear tomographic image with no disturbance on the screen can be obtained. .
  • the width D of the radial cross section of the annular projections 20a and 20b changes in order to cancel the irregular magnetic field in the example shown in FIG. 4, the high irregular magnetic field regions F l and F in the X-axis direction are shown. Areas 2 2a and 2 2b opposed to 3, but this area is not limited to a part of the area, and the width 0 remains the 3 ⁇ 4 ⁇ value D 0. Except for the above, a circumferential ⁇ f page area may be used. The effect of canceling the irregular magnetic field is usually improved by increasing the range in which the width D is changed.
  • the width D of the cross section in the direction away from the ring is changed within the above range in order to cancel the irregular magnetic field, but the effect of canceling the difficult field is determined by the ring ⁇ .
  • the cross-sectional area S and the height H can also be obtained by changing the cross-sectional area S and the height H of the cross-section, so that these cross-sectional areas S and the height H are changed. The same can be said for the range of change in direction.
  • FIG. 6 is a cross-sectional view of the magnet device according to the present invention
  • FIG. 7 is a diagram for explaining the generation of irregularity ⁇ by the device of FIG. 6
  • FIG. 8 is a structural diagram of the ring used in the device of FIG. It is.
  • a magnetic material is not used for the material of the pillar that supports the static magnetic field generation source, but even in such a case, an irregular magnetic field is generated in the imaging space 10. .
  • the generation of the irregular magnetic field will be described with reference to FIGS. 6 and 7, and the method of canceling the irregular magnetic field will be described with reference to FIG.
  • ⁇ 3 30 a, 30 b made of a magnetic material disposed vertically opposed to each other across the space 10 It is supported by one post 32.
  • the support 30 is made of a non-magnetic material, for example, stainless steel. Rings on the side facing the ⁇ space 10 of the upper and lower ⁇ 3 30a, 3Ob!
  • Dog ⁇ 3 4a, 3 4b are arranged.
  • the coordinate system in Fig. 6 passes through the center 0 of the shooting space 10, the vertical direction is the Z-axis direction, the horizontal direction with the fulcrum 32 is the X-axis direction (the left side is positive), and the front-rear direction (the front side is positive). ).
  • an upward m is formed in the water space 10.
  • the ⁇ BO for creating this place is transmitted through the magnet device 28 in the directions of the arrows 36a, 36b, and 36c, so that the ⁇ mB O causes the upper and lower magnetic poles 30a, 3
  • a force P indicated by arrows 38a and 38b acts between Ob and the annular projections 34a and 34b. Due to this force P, the magnetic poles 30a, 30b and the annular protrusions 34a, 34b are respectively inclined at an angle (the position after the inclination of the arrow is indicated by a broken line), and the upper and lower arrows 30a, 30b are shown.
  • the gap on the left side i.e., on the side away from the post 32, is narrower than the gap on the right side, i.e., the side near the post 32, between a and 30b and between the upper and lower annular separations 34a and 34b. Slanting around.
  • Figure 7 shows the area where the irregular magnetic field is generated.
  • a non- ⁇ field is generated in a region F 1 farthest from the strut 32 and a region F 3 closest to the strut 32.
  • the field is formed stronger in region F1 than in region F3. If the average magnetic field bell f 0 of the bulging space 10 is assumed to be » a positive irregular magnetic field f 1 is generated in the irregular ⁇ region F 1, and a negative magnetic field is generated in the irregular easy region F 3: f 3 occurs.
  • FIG. 8 (a) is a longitudinal sectional view of the annular projections 34a and 34b
  • FIG. 8 (b) is a plan view thereof.
  • the non-fiber separated from the support 3 the annular «S3 4a, corresponding to the page area F 1, where the cross-sectional area S 0 of the annular projections 34 a and 34 b in the Y-axis direction is a» value.
  • the cross-sectional area S1 of the region 40a of 34b is made smaller than S0, and the ring corresponding to the non-field region F3 close to the strut 32 (the region 40 of dogwei 34a, 34b) Make the cross-sectional area S3 of b larger than SO.
  • the area 40a where the cross-sectional area is reduced to S1 is reduced, and the cross-sectional area is reduced.
  • the magnetic field intensity in the irregularly swellable area F 1 in the imaging space 10 decreases by (f 1 ⁇ f 0) because the magnetic flux that increases M in the area 40 b where S 3 is increased by increasing
  • the magnetic field in the field region F 3 increases by (f 0-f 3).
  • the case where a magnetic material or a non-magnetic material is used as the material of the column supporting the static electricity generation source and the magnetic pole, and the case where two or one column is arranged as the column is described.
  • these combinations are used, and the field generated by the existence of the magnetic ffii main body and the magnetic field generated by one support temple are sculpted into the Toto space.
  • the area where the Imperial Palace is located is not limited to two places, but one place or three places More than: There is also ⁇ .
  • the amount or cross-sectional area of the magnetic material at the corresponding position in the circumferential direction of the annular protrusion is determined by the first and second difficulties in accordance with the location of the irregular magnetic field in the water space 10. Just increase or decrease as in the example.
  • FIG. 1 a modified example of the annular projection in the magnet device of the present invention will be described with reference to FIGS. 1, 2, and 9 to 15.
  • FIG. 1 a modified example of the annular projection in the magnet device of the present invention will be described with reference to FIGS. 1, 2, and 9 to 15.
  • FIG. 1 and 2 show the first example as described above.
  • regions Fl and F3 with high irregular magnetic fields are generated near the ferromagnetic columns 8a and 8b in the iff space 10 so that they are opposed to these regions Fl and F3.
  • the ⁇ -direction cross-sections of the upper and lower annular 3 ⁇ 43 ⁇ 46a, 6b regions increase or decrease at least one of the cross-section height H and height D so as to cancel the above-mentioned irregular magnetic field, and increase or decrease the cross-sectional area S Things.
  • FIG. 2 shows an example in which the width D of the annular ⁇ 6 a is increased or decreased along the circumferential direction.
  • the width D is 0. Is reduced to the widths D 1 and D 3 with respect to the 3 ⁇ 4 ⁇ value DO, and the cross-sectional area S is reduced.
  • the annular protrusions 6 corresponding to the regions F1 and F3 are formed.
  • the width D is gradually increased in both directions (counterclockwise and counterclockwise) along the circumferential direction from the area of D1 or D3 to the area of wide width D0.
  • the positions of the cross-sections and the values of the cross-sectional areas S of the annular 6a and 6b are determined, and the cross-sectional area S
  • the width D can be determined according to the value. For this reason, the ring) [the dog projections 6a and 6b only need to be manufactured in one type, and the manufacture is easy.
  • FIG. 9 shows a third structural example of a magnet device according to the present invention.
  • the magnet device 44 is composed of upper and lower ⁇ t sources, 2a, 2b, 44a, 4b, and a ring, which are arranged opposite to each other across the inflated space 10.
  • the height H of a part of the circumferential area of the annular ⁇ 46 a, 46 b is changed so as to cancel the irregular magnetic field, and the end faces 50 a, 50 b of the annularly separated 46 a, 46 b on the space 10 side are wave-shaped.
  • FIG. 9 (a) is a front view of the entire apparatus
  • the X-axis direction is in the left-right direction with the columns 8a and 8b
  • the rotation angle ⁇ is set counterclockwise with the X-axis as republic
  • the height H is reduced to reduce the cross-sectional area S.
  • the height H changes sequentially along the circumferential direction according to the amount of the irregular magnetic field at the corresponding position.
  • the end face 50b of the annular space 46b on the side of the space 10 forms the taste.
  • the area in which the height H of the annular ring 46 is changed is a part of the area in the circumferential direction corresponding to the area where the irregular magnetic field is generated in the normal expansion space 10.
  • the activation region may extend over the entire region in the circumferential direction. As in the latter case, when the height H is increased or decreased over the ⁇ region of the annular protrusion 46 to cancel the first field, it is possible to cancel the higher-order field. The effect of making the magnetic field uniform is greater.
  • FIG. 10 is a plan view of a fourth embodiment of the magnet device according to the present invention.
  • the annular projections 52a and 52b of this embodiment are substantially the same as the annular projections 6a and 6b of the first embodiment shown in FIG. , 54b are not part of the circumferential direction, but sequentially change the width D at the spiral degree ⁇ over the ⁇ page area. That is, the width D of the annular projections 52a and 52b is changed along the circumferential direction from the area of the narrow width D1 or D3 in the X-axis direction to the area of the wide width D0 in the Y-axis direction. It is formed so as to spread in both directions (counterclockwise and counterclockwise) over the ⁇ ! Area. As a result, also in this embodiment, the same effect as in the third example in FIG. 9 can be obtained.
  • FIG. 11 is a plan view of a fifth embodiment of the magnet device according to the present invention.
  • the radial width D of the upper and lower annular projections 54a and 54b is narrow in the left-right direction (X-axis direction) and wide in the front-rear direction (Y-axis direction). Furthermore, the widths D1 and D3 in the X-axis direction are almost the same.
  • the width D2 of the rear region 55 is wider than the width D4 of the front region 56 in the Y-axis direction.
  • the area of the rear region 55 is larger than the area of the front half ⁇ page region 56.
  • the width of the ring-shaped weaves 54a and 54b is increased or decreased over the entire circumferential direction, but the area where the width is increased or decreased is the circumference. It goes without saying that only a part of the directions is sufficient. That is, it goes without saying that it may be applied to a part of the annular projections 54a and 54b corresponding to the generation region of the irregular magnetic field in the imaging space 10.
  • an increase / decrease area of the width D is provided at three to four places in the circumferential direction of the annular projections 54a, 543 ⁇ 4), the number of which depends on the number of irregular TO areas in the imaging space 10.
  • the number is not particularly limited by the number in the example. The same applies to other examples.
  • FIG. 12 and FIG. 13 show structural views of a circular ring of a sixth example of the magnet device according to the present invention.
  • Fig. 12 is the residual glue diagram of the combination of the lower ring and ⁇
  • Fig. 13 is the plan view of the ring.
  • a combined annular ring 58b (58a) composed of a large-diameter dog protrusion 60 and a small-diameter annular ring 62 is arranged on the surface of the magnetic pole 4b (4a). ing.
  • the outer periphery of the large-diameter annular ring 60 is formed so as to substantially coincide with the outer peripheral surface of the ring 4b.
  • the small-diameter annular ring 62 is arranged substantially concentrically inside the large-diameter annular ring 60.
  • the width DL of the large-diameter annular protrusion 60 and the width DS of the small-diameter annular protrusion 62 are both varied along the circumferential direction.
  • the large-diameter annular protrusion 60 has a maximum value DL2 and a minimum value DL4 of the width DL in the Y-axis direction, and has average values DL1 and DL3 of the width DL in the X-axis direction.
  • the width DL4 in the Y-axis direction is reduced from the narrow width DL4 in both directions along the circumferential direction to the wide width DL2 via the width DL1 and the width DL3, and sequentially to the wide width DL2. Is changed to be larger.
  • the two narrow widths DS2 and DS4 in the Y-axis direction extend along the circumference in the circumferential direction, and the wide widths DS1 and DS3 in both directions.
  • the sequential width DS is large It has been changed to become.
  • the direction of the wide width DL2 of the large-diameter annular protrusion 60 differs from that of the wide width DS1, DS3 of the small-diameter annular weir 62 by about 90 °.
  • the dog ⁇ 60 mainly cancels the irregular magnetic field in the ⁇ -axis direction at the outer periphery of the imaging space 10, and mainly captures the image by the small diameter annular projection 62
  • the two annular rings with different ⁇ are arranged on the upper and lower magnetic poles, respectively, so that the irregular magnetic field of the imaging space 10 is canceled not only in the circumferential direction but also in the judgment direction. Can be.
  • the large-diameter ring Wei 60 and the small-diameter ring Wei 60 change the area of cancellation of the irregularity in the circumferential direction. This is an effective method for canceling an ineffective field when the generation region of the image is inclined with respect to the judgment direction.
  • the present invention is not limited to this, and it goes without saying that three or more rings may be provided. Also, in the present example, the position of the wide width of the annular separation was shifted by about 90 ° between each other, but it is needless to say that other angles may be shifted instead of this.
  • FIG. 14 is a plan view of a seventh example of the magnet device according to the present invention, which is annularly separated.
  • the annular separation is made up of a plurality of members with different widths d in the judgment direction.
  • the upper and lower annular gaps 64a and 64b have radial widths of da, db, and dc, respectively (da ⁇ db ⁇ dc). It consists of three types of circular ⁇ blocks 66a, 66b, and 66c.
  • annular protrusion blocks 66 a, 66 b, and 66 c are arranged in the circumferential direction so that their outer circumferences are substantially circular, and are wide in the X-axis direction (width dc )
  • the outer peripheral surfaces of the annular protrusions 64a and 64b are substantially circular around the Z axis which is the central axis of the device, but the inner peripheral surface has a radius of each annular protrusion block. Is different, so it is stepped. For this reason, the inner peripheral surface of the inner peripheral surface of the annular weir block 66 is taken as an envelope 68, and the ring is formed by the envelope 68 (in the dog projections 6 4a and 6 4b). In this way, by representing the inner peripheral surface with the envelope,
  • each annular block can be determined so that the radius R of the envelope 68 on the inner peripheral surface periodically changes with respect to the rotation angle ⁇ . .
  • the number of the annular ⁇ -probes 66 constituting the annular ⁇ 64a, 64b is eight in the figure, but is not limited to this, and may be another number.
  • annular projection block with a different radius on the inner peripheral surface 6 6 are arranged over the entire circumferential area of the annular projections 64 a and 64 b, but the annular projection block 66 may be arranged only partially in the circumferential direction. That is, only a part of the ring ⁇ (dog ⁇ 64a, 64b) facing the region where the irregular magnetic field is generated in the imaging space 10 may be used.
  • the outer peripheral surface has the same radius, and ⁇ number of annular ⁇ -blocks 66 having different inner peripheral surface ⁇ are arranged along the inner peripheral direction.
  • the present invention is not limited to this, and a plurality of annular probes having the same inner peripheral surface judgment and different outer peripheral surface judgments are arranged along the circumferential direction.
  • a plurality of annular holes having different diameters on both the inner peripheral surface and the outer peripheral surface may be arranged along the circumferential direction.
  • the outer peripheral surface is stepped, so take this envelope to represent the outer peripheral surface as an annular projection
  • the inner peripheral surface and the outer peripheral surface Since both have a stepped shape, they can be handled in the same way as the seventh difficult example in FIG. 14 by taking the envelope of both and representing the inner and outer peripheral surfaces as annular projections.
  • FIG. 15 shows a summary structural diagram of an eighth example of the magnet device according to the present invention.
  • the magnet device 70 includes upper and lower «field generators 2 a, 2 b, ⁇ a 4 a, 4 b, and a ring (dog ⁇ 7) which are arranged to face each other across the expansion space 10.
  • the upper and lower annular projections 7 2a and 7 2b are Z arranged along the circumferential direction. It is composed of a plurality of annular blocks 74a, 74b, 74c and the like having different heights h in the axial direction.
  • the end faces of the syllable space 10 2 of the annular spaces 7 2 a and 7 2 b, which are formed by a plurality of annular blocks 7 4, are stepped. Take 76 a and 76 b to represent the end face of the circular wei 72 a and 72 b on the ⁇ space 10 side.
  • the end faces of the envelope springs 76a and 76b, that is, the circular ⁇ 372a and 72b are dog-shaped I dogs as in the third embodiment of FIG. Therefore, the present example can be handled in the same manner as the third example of FIG.
  • the heights H of the springs 76a and 76b on the end face of the annular space 72a and 72b on the imaging space 10 side are periodic with respect to the rotation angle 0 about the Z axis.
  • the height h of each annular pro- ject 74 can be determined so that In this way, by periodically changing the height H of the envelopes 76a and 76b of the end faces, the periodic inefficiency of the iff space 10 can be easily canceled.
  • the annular weir blocks 74 with different end heights h are arranged over the entire circumferential area of the annular projections 72 a and 72 b.
  • the range in which is arranged may be only a part of the circumferential direction. That is, it may be only a part of the annular regions 72a and 72b opposed to the region of the space 10 where irregularity is likely to occur.
  • the number of the ring-shaped weir 74 is 6 per ring of the ring S 72 a and 72 b. Appropriate number is 0 or less.
  • the fixing of the annular projection blocks 74 is also performed in the same manner as in the seventh embodiment of FIG.
  • a circular weir was constructed by circulating a plurality of circular ⁇ proxies with different widths d or heights h in the circumferential direction.
  • the cross-sectional area S of the ring-shaped structure was changed by changing the width d or height h of the ring-shaped structure. It is translated into ⁇ .
  • the present invention is also valid when a plurality of annular dog projections having different cross-sectional areas S are arranged along the circumferential direction to form an annular projection irrespective of the shape of the annular dog. .
  • a rectangle circumscribing the cross section in the judgment direction of the annular ⁇ prok (however, each side is assumed to be parallel to the judgment direction and the Z-axis direction), and the side parallel to the judgment direction is defined.
  • the side that is TO in the width and Z-axis directions as the height it can be handled in the same way as the seventh and eighth examples.
  • Equation (1) the component in the Z-axis direction of the magnetic field generated by the upper and lower ⁇ -field sources 2a and 2b in the space 10 is generally represented by Expression (1).
  • the magnetic field of order (0, 0) is a magnetic field that does not depend on coordinates, and is a uniform magnetic field to be generated in the space 10.
  • the magnetic field of that order is a magnetic field that changes with coordinates
  • an image ⁇ is generated in the iifized tomographic image, as shown in Fig. 3 (b), etc., which is called a random or irregular magnetic field component.
  • the order (1, IX (3, IX and (2, 2), etc.) in equation (1) is reduced due to the arrangement of a ferromagnetic support or the effect of magnetic attraction acting between the magnetic poles.
  • the following irregular magnetic fields are large: For example, as shown in Fig. 1, when the columns 8a and 8b are arranged at symmetrical positions in the X-axis direction, the above-mentioned mode (2, 2) etc.
  • the non- ⁇ field of mode m2 1 such as (3, 1) mainly occurs.
  • the most efficient way to cancel the irregular magnetic field component of mode m2 1 is to change the above cross-sectional area S with the sine function of mode m2 1 with respect to the turning degree ⁇ . That is, the cross-sectional area S is changed as in the equation (2).
  • SQ is the average value of the cross-sectional areas of the annular gaps 34a and 34b, and SB ; 1 is the amplitude of the change in the cross-sectional area.
  • the median S at 270 °. Becomes In comparison with Fig. 8, the minimum value (S 0 -S B) 1 ) is S 1, the silent value (S 0 + S Bjl ) is S 3,
  • the intermediate value S 0 is S 0, and varies sinusoidally between the waste value and the minimum value.
  • the ring-shaped dog projections 34a, 34b selectively select the ⁇ component of the mode m21. appear. Therefore, by appropriately determining the amplitude, the mode m2, which has the same magnitude as the irregular magnetic field of the mode m2 1 generated in the iff space 10 of the magnet device 28 shown in FIG. The ⁇ component of 1 can be generated, and the irregular magnetic field of mode m2 1 can be canceled out, and the magnetic field of the expansion space 10 can be made uniform.
  • the coordinate system has been introduced to explain physical aspects such as inventions, etc., and the coordinate system is arbitrary. Therefore, the essence of the invention in the present embodiment does not change depending on how to take this coordinate system.
  • the essence of the invention in this example is that the cross-sectional area, height, or width in the judgment direction of the annular projection is sinusoidally periodic in accordance with the order of the irregular magnetic field to be canceled. Is to change it.
  • a large field of mode m2 2 such as the order (2, 2) in equation (1) is generated.
  • the width D in the judgment direction is periodically changed in order to periodically change the cross-sectional area S at the rotation angle of the ring 6a (6b).
  • DQ is an average of ⁇ width of the annular release 6 a ⁇ 6 b
  • D B, 2 is the amplitude of the change in width.
  • the width D of the annular release 6 a, 6 b is the minimum value in the X-axis direction (D.- D B, 2), spoiled value Y-axis direction (DQ + D b, 2) Becomes In comparison with Fig. 2, the minimum value (D 0 -D Bj2 ) is D 1 or D 3, and the waste value (D 0 + D Bj2 ) is DO, which varies sinusoidally between the minimum value and the silent value. are doing.
  • the ring protrusions 6a and 6b typically generate an explosive component of mode m22. Therefore, by appropriately determining the amplitudes D B and 2 , the mode m2 is generated in the expansion space 10 of the magnet device 1 in FIG. It is possible to generate 22 magnetic field components, cancel the field of m 2, and make the magnetic field of the customer space 10 uniform.
  • the height H of the upper and lower rings 46a and 46b is changed along the circumferential direction as shown in Expression (4).
  • H 0 is the ring!
  • H B , 2 is the width of the height change.
  • This embodiment is useful for canceling the magnetic field of mode m22 as in the first example of FIG.
  • the width D in the ⁇ direction of the upper and lower annular separations 52a and 52b is changed as in equation (5).
  • D 0 is cyclic «S52a, 52 b of the average width
  • D B, 2 is the amplitude of the width change.
  • Equation (5) By changing the width D of the loops 52a and 52b as shown in Equation (5), the loops ⁇ 52a and 52b selectively generate a magnetic field component of mode m2 2 in the ⁇ space 10, so that the amplitude D By properly selecting B and 2 , the non- ⁇ field of mode m 2 2 is canceled out, and the magnetic field in i-space 10 is made uniform.
  • Equation (5) in this ⁇ is exactly the same as equation (3) in the first ⁇ example, and is suitable for canceling the irregular magnetic field of mode m22, as in the first difficult example of FIG. is there.
  • the radial width D of the upper and lower annular wheels 54a and 54b is changed along the circumferential direction as in equation (6).
  • D 0 is the average width of 54a, 54b
  • D A) 1 is the amplitude of the width change in mode m2
  • D B , 2 is the width of the width change in mode m22. Amplitude.
  • the irregular magnetic field of the two modes, the mode m2 1 and the mode m2 2 can be canceled out. It becomes possible to cancel. Because of this, practical For example, it can be used to cancel irregularities in a magnet device having a more privileged structure than the first difficult example in FIG. 1 or the second difficult example in FIG.
  • two upper and lower orchids 4a and 4b each have two annular projections, that is, large-diameter annular projections 60, and are arranged on the inner periphery thereof. It shows that a small-diameter circular ring 62 is installed and the cross-sectional area in the ⁇ direction of each circular ring 360, 62 is changed in different modes. Specifically, in FIG. 13, for the outer large-diameter annular ring 60, the width D L in the direction of its crossing is changed as in equation (7), and for the inner small-diameter annular ring 62, The width D s in the radial direction is changed as in equation (8).
  • the large-diameter annular separation 60 and small-diameter annular separation 62 can independently change the mode and phase of the magnetic field generated to cancel the irregular magnetic field. This is effective for canceling irregular magnetic fields. This effect is enhanced by increasing the number of rings to three or more, and the accuracy of correction is also improved.
  • the upper and lower annular weirs 64a, 64b are formed by a plurality of annular protuberances 66a, 66b, 66c, etc., each having a different width D. ⁇ It has been formed. The judgment of the outer peripheral surface of each of the annular blocks 66 is almost the same, and the radius of the inner peripheral surface is different corresponding to the radial width d of each.
  • each annular projection block 66 is approximately determined by the dimension of the envelope 68 in the judgment direction.
  • the width d in the judging direction of each annular separating block 66 is determined so that the width D between the envelope spring 68 on the inner peripheral surface and the outer peripheral surface changes periodically in the circumferential direction. ing.
  • the rotation R of the wrapper spring 68 on the inner peripheral surface ( ⁇ ) also changes periodically, and in this example, it changes as shown in equation (9).
  • the average of R Q is the inner peripheral surface of the packaging fountain 6 8 ⁇ , R B, 2 is the amplitude of the broadcast changes.
  • the 10 magnetic fields are homogenized.
  • each of the proteins 6 6 has an inner peripheral surface of a different report: ⁇
  • the present invention is not limited to this, and is similarly applied to a case where each of the annular projection blocks has an outer peripheral surface having a different radius or an inner peripheral surface and an outer peripheral surface having different radii.
  • the upper and lower annular weaves 72a and 72b are respectively formed by a plurality of annular projections 4a, 74b, 74c, etc., each having a different height h in the Z-axis direction.
  • each of the annular blocks 74 has substantially the same width, and the height h to the end face on the imaging space 10 side is different from each other.
  • the end faces of the ring dogs 72a and 72b are approximately formed by the dimensions of the envelopes 76a and 76b of the end faces of the annular protruding pro- jects 74.
  • the height of the end face of each annular release block 74 is represented by the height H of the envelope springs 76a and 76b of the end face in the Z-axis direction. It is determined to change periodically.
  • the height H of the envelopes 76a and 76b of the end faces at the rotation angle ⁇ changes periodically, and in this example, it is changed as shown in equation (10).
  • 1 ⁇ is the average value of the heights of the end faces oftown72 and 72 b, and the heights of the hot springs 76 a and 76 b, and 2 are the amplitudes of the height changes.
  • the height h of the annular ⁇ block 74 that composes the annular ⁇ 72a ⁇ 72b becomes Since it changes along the circumferential direction in the same mode m22 as in the equation (10), the annular separations 72a and 72b almost selectively generate the magnetic field component of the mode m22.
  • Kazumi's 1st to 8th implementations of the magnet device have a simple configuration, such as a single support or a single support or two supports that are arranged vertically.
  • a higher-order mode irregular magnetic field is generated.
  • the value of the irregularity m of each mode is obtained, and the value of the irregularity m is calculated in accordance with the value of these irregular magnetic fields.
  • the purpose of this study is to determine the values of the cross-sectional area (or the amount of the magnetic material) of the four dogs.
  • the magnetic field component for canceling the mode inversion is selectively generated for each mode, so that it is irregular for each mode.
  • the entire magnetic field is canceled, and the magnetic field in the space 10 is made uniform.
  • a coordinate system has been introduced for the form of the cyclic deformation of the ring.
  • the coordinate system is originally an auxiliary means for explaining the physics, and the content of the present invention is not limited by the arbitraryness of how to take the coordinate system.
  • the gist of the present invention is that the annular protrusion is periodically deformed in the circumferential direction.In order to make this understanding easier, it has been explained that a coordinate system has been introduced and explained. It will be easy for a trader to understand.
  • the above-mentioned heat source is provided with some power source in order to form a space in the space 10.
  • a super- # coil-normal coil-permanent magnet can be used as the magnetomotive force source.
  • the superconducting coil needs a cooling means to cool it to a superconducting state. Since a high magnetic field can be generated in the shadow space, a high-resolution and clear MR image without distortion can be obtained by applying the present invention to the magnet device.
  • the generated magnetic field is lower than in the case of a superconducting coil.
  • the SI of the coil is not required, the i3 ⁇ 4 cost and the maintenance cost of the device can be reduced.
  • permanent magnets do not use coils, there is no need for a coil power supply or coil frights, which makes maintenance and management of the equipment easy and greatly reduces equipment maintenance costs.
  • the symbols in the drawings have the following meanings.
  • the magnet device of the present invention at least a part of the annular ⁇ is arranged in the circumferential direction by arranging the annular ⁇ on the opposing surface side of the magnetic pole disposed facing the expansion space.
  • the irregular magnetic field generated in the imaging space is canceled, and the magnetic field is made uniform.
  • the amount of the magnetic pole at the position corresponding to the ring-shaped weir is removed to eliminate the irregular field generated by this, or
  • the above-mentioned irregularity ⁇ is canceled out, and the magnetic field in the ⁇ space is made uniform.
  • two or more annular protrusions are arranged in the radial direction, and the amount of at least a part of these annular magnetic materials in the circumferential direction, or the cross-sectional area of the cross section in the meshing direction,
  • the irregular magnetic field generated in the space can be canceled out in the circumferential and radial directions, that is, over the entire page area of the space, and the magnetic field in the expanded space can be eliminated. Is uniformed.
  • the annular wei by forming the annular wei to have a plurality of annular lugs with different cross-sectional areas, widths, or heights in the cross section in the cross direction, the annular wei is generated integrally. Like the ones, it is possible to cancel the inconsistency in the space and to reduce the cost of the ring projection by reducing the size of the ring. .
  • the magnet device includes a magnetomotive force source, and a pair of opposing field generating sources; It has one or more ring dogs arranged on the opposite side of the shroud, and the cross-sectional area, width, or height of the annular protrusion in the radial direction changes periodically in the circumferential direction. So the irregular magnetic field generated in the imaging space Therefore, it is possible to cancel out that the bow ffi distribution periodically changes in the circumferential direction, and as a result, it is possible to make the return space uniform.
  • the magnet device includes at least one annular ring disposed on the opposite surface side of the ring, and the annular ring is composed of a plurality of annular rings. Since the cross-sectional area, width, or height of the cross section in the ⁇ direction changes periodically in the circumferential direction, the irregular magnetic field transfer in the circumferential direction of the creel space changes irregularly. Since it is possible to negate the vibrations, it is easy to assemble the divided annular member and the assembling thereof, so that the manufacturing cost can be reduced.
  • the magnet device includes one or more annular members arranged on the opposite surface side of the ring, and the annular member includes a plurality of annular members.
  • the inner envelope connecting the inner peripheral surface in the direction, the outer envelope connecting the outer peripheral surface in the radial direction, or the end surface envelope connecting the end surfaces facing the space are periodically changing in the circumferential direction.
  • the cross-sectional area, width, or height, or the envelope spring of the radial cross section of the annular protrusion changes in a sine function in the circumferential direction, A field having an inflatable bow distribution that varies sinusoidally along the circumferential direction of the space can be canceled out, and the magnetic field in the space can be made uniform.
  • the cross-sectional area, width, height, or envelope of the radial cross section of the annular protrusion is one or more in one circumferential direction. Is changed sinusoidally according to the mode m, so that along the circumferential direction of the return space, the magnetic field changes according to the sine function of mode m. Field bow Non- ⁇ field with ffi distribution can be canceled.
  • the cross-sectional area, width, height, or envelope of the radial cross section of the annular protrusion is different from one another by two or more in one circumferential direction. Since it is changed by the superposition of the sine functions by the mode m which is one or more, the distribution of the squib keys along the circumferential direction of the dilation space is changed by the superposition of the sine functions of the multiple modes. With can cancel the field.
  • the magnet device of the present invention at least two or more annular separations are provided on the side facing the magnetic pole, and the cross-sectional area, width, or height of the cross section of these annular weaves in the crosswise direction is provided.
  • the envelope changes in a sinusoidal function by one or more different modes over one circumference in each direction. ⁇ , ⁇ , etc.
  • the force S can cancel out the field having the magnetic field bow J ⁇ distribution distributed in the radial direction, which changes by superposition of the sine functions of different modes along the circumferential direction corresponding to.
  • a magnetic material or a non-magnetic material that leak-tightly couples between a pair of primary sources or a pair of pairs arranged opposite to each other across the imaging space. Because of this, it is supported without great deformation between the ⁇ ⁇ and large openness is obtained in the iff space.
  • a main magnetic body is added to magnetically connect the static magnetic field generation sources or the magnetic poles with a magnetic material to form a magnetic circuit. Since it is formed, the leakage magnetic field of the device can be reduced.
  • the magnet device of the present invention when the magnetomotive force source is a super-articulated coil, a high magnetic field bow is provided in the water supply space, and a uniform difficulty is obtained. If the fiber source is a normal conducting coil, cooling of the coil becomes unnecessary, reducing the production and maintenance costs of the equipment. If the power source is a permanent magnet, the maintenance of the equipment becomes easy and the maintenance cost of the equipment is greatly reduced.

Abstract

L'invention concerne un dispositif à aimant permettant d'obtenir une image MR nette et précise par élimination de tout champ magnétique irrégulier généré dans un champ magnétique dans un espace de prise d'image d'un appareil de formation d'image par résonance magnétique. Une paire de sources de génération de champ magnétique stationnaire (2a et 2b) et une paire de pôles magnétiques (4a et 4b) en regard l'un de l'autre dans le sens vertical afin de prendre en sandwich un espace (10) de prise d'image reposent sur deux appuis ferromagnétiques (8a et 8b) disposés dans le sens droite-gauche. On dispose de saillies annulaires (6a et 6b) sur les côtés opposés des pôles magnétiques (4a et 4b). La largeur d'une section dans le sens radial est définie selon des valeurs petites (D1 et D3) dans le sens droite-gauche, et une grande valeur (D0) dans le sens longitudinal de manière que la valeur change graduellement entre les deux. Dans le dispositif à aimant (1), un champ magnétique irrégulier positif est généré dans une zone à proximité des appuis (8a et 8b) de l'espace de prise d'image (10). Cependant, en définissant la largeur de saillies annulaires (6a et 6b) dans le sens droite-gauche comme plus petite que celle des autres parties, le flux magnétique traversant la zone et convergeant dans l'espace de prise d'image (10) est réduit, ce qui supprime le champ magnétique irrégulier positif susmentionné.
PCT/JP2003/002951 2002-03-14 2003-03-12 Dispositif a aimant et imagerie par resonance magnetique utilisant ledit dispositif WO2003075757A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP2002069952A JP2003265435A (ja) 2002-03-14 2002-03-14 磁気共鳴イメージング装置用磁石装置
JP2002/69952 2002-03-14
JP2002/69656 2002-03-14
JP2002069656A JP4040334B2 (ja) 2002-03-14 2002-03-14 磁気共鳴イメージング装置

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62112106U (fr) * 1985-12-27 1987-07-17
JPH01280447A (ja) * 1988-05-02 1989-11-10 Hitachi Ltd 核スピン共鳴断層撮影装置
JPH02248008A (ja) * 1989-03-20 1990-10-03 Sanyo Electric Co Ltd 核磁気共鳴撮像装置に用いる静磁場発生装置
JPH0394732A (ja) * 1989-09-08 1991-04-19 Sumitomo Special Metals Co Ltd Ｍｒｉ用磁界発生装置
JPH05182821A (ja) * 1991-12-27 1993-07-23 Sumitomo Special Metals Co Ltd Ｍｒｉ用磁界発生装置
JPH05251231A (ja) * 1991-12-26 1993-09-28 Applied Superconetics Inc 磁気共鳴結像用近接自在磁石
JPH08243087A (ja) * 1995-03-13 1996-09-24 Shin Etsu Chem Co Ltd 磁石対向型永久磁石磁気回路
WO2001031359A1 (fr) * 1999-10-29 2001-05-03 Oxford Magnet Technology Limited Aimant ameliore

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62112106U (fr) * 1985-12-27 1987-07-17
JPH01280447A (ja) * 1988-05-02 1989-11-10 Hitachi Ltd 核スピン共鳴断層撮影装置
JPH02248008A (ja) * 1989-03-20 1990-10-03 Sanyo Electric Co Ltd 核磁気共鳴撮像装置に用いる静磁場発生装置
JPH0394732A (ja) * 1989-09-08 1991-04-19 Sumitomo Special Metals Co Ltd Ｍｒｉ用磁界発生装置
JPH05251231A (ja) * 1991-12-26 1993-09-28 Applied Superconetics Inc 磁気共鳴結像用近接自在磁石
JPH05182821A (ja) * 1991-12-27 1993-07-23 Sumitomo Special Metals Co Ltd Ｍｒｉ用磁界発生装置
JPH08243087A (ja) * 1995-03-13 1996-09-24 Shin Etsu Chem Co Ltd 磁石対向型永久磁石磁気回路
WO2001031359A1 (fr) * 1999-10-29 2001-05-03 Oxford Magnet Technology Limited Aimant ameliore

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