JP4969148B2 - Shim coil manufacturing method and magnetic resonance imaging apparatus - Google Patents

Description

  The present invention relates to a magnetic resonance imaging apparatus (hereinafter referred to as an MRI apparatus), and more particularly to a structure of a flat plate-shaped gradient magnetic field generating coil or a magnetic field correction coil used in the MRI apparatus and a manufacturing method thereof.

  An MRI apparatus measures and calculates a signal obtained from a nuclear magnetic resonance (hereinafter referred to as “NMR”) phenomenon of a subject placed in a magnetic field, thereby calculating the density distribution and relaxation time distribution of nuclear spins in the subject. Are displayed as tomographic images, and are used for various diagnoses and the like with the human body as the subject. In order to obtain a signal from the NMR phenomenon, the subject is placed in a spatially and temporally uniform static magnetic field, and the subject is irradiated with electromagnetic waves in a pulsed manner by a high-frequency coil. Receive by coil. Further, a gradient magnetic field is superimposed on the static magnetic field in order to give position information to the NMR signal. For this reason, the MRI apparatus includes a gradient magnetic field coil that generates a gradient magnetic field orthogonal to the three axial directions. There are various imaging methods such as spin echo method and gradient echo method. In either case, the high frequency coil and gradient magnetic field coil are switched in a pulse form at high speed by a control signal from the sequencer, and predetermined repetitions are made. Driven repeatedly in time.

  As the gradient magnetic field coil, a Golay coil or the like is used in addition to the saddle type coil. In addition, a shim coil that generates a higher-order magnetic field is used to correct the static magnetic field distribution. The gradient magnetic field coil and shim coil conductor patterns are not closely in contact with each other and the spacing between the conductor patterns is not as constant as that of a general motor or electromagnet coil. Therefore, it is necessary to accurately arrange the conductor at the position. As a method of manufacturing the gradient magnetic field coil and shim coil, a) a method of forming from a conductor plate and b) a method of forming from a wire are mainly used.

  As shown in FIGS. 13A and 13B, a coil is formed from a conductor plate 131 such as a copper plate by cutting a spiral groove 132 by water jet containing abrasive grains, etching, or cutting. It is to make a shape. Since this method has an advantage that the resistance value can be lowered as compared with the method of forming a coil pattern from a wire, it is suitable for a gradient magnetic field coil for passing a large current.

On the other hand, a method of forming a coil from a wire rod is to obtain a desired coil pattern by arranging and fixing an enameled wire, a stranded wire or the like at a predetermined position. As one method, there is a method of spreading the wire while determining the interval of the wire with a spacer. Further, in Patent Document 1, as shown in FIG. 14, a groove 142 is provided along a coil pattern to be formed on a nonmagnetic insulating plate 141, and a wire 143 is inserted into the groove 142, and an elastic adhesive is provided. A method of obtaining a desired flat coil by fixing the wire 143 to the groove 142 at 144 is disclosed. The manufacturing method described in Patent Document 1 is less expensive than the method of processing the conductor plate 131 into a coil shape when the cross-sectional area of the coil wire 143 is small, and the wire 143 is held by the insulating plate 141. Therefore, rigidity can be increased.
Japanese Patent Publication 3-71891

  The manufacturing method of the flat coil described in Patent Document 1 includes an insulating plate 141 in which a groove 142 is formed as a member for holding a wire. For this reason, the thickness of the flat coil is determined by the thickness of the insulating plate 141. However, since the insulating plate 141 needs to withstand groove processing and have rigidity to hold the wire, it cannot be made too thin, and there is a limit to making the flat plate coil thinner. In addition, when the gradient magnetic field coil and shim coil are molded with resin, there also arises a problem that the insulating plate prevents the resin from wrapping around.

  On the other hand, a shim coil that generates a higher-order magnetic field is driven by a low-current power source that is overwhelmingly cheaper than a gradient magnetic field coil, so that the winding length of the coil is significantly longer than that of a gradient magnetic field. For example, if a Z2 shim coil that generates a quadratic term of a magnetic field in the Z direction requires a 25 m wire to obtain an output of 5 μT with a current of 5 A, depending on the geometric dimensions, a Z4 shim coil that generates a quadratic term is approximately 100m wire is required. Therefore, if the shim coil is to be manufactured by the manufacturing method described in Patent Document 1, it is necessary to perform groove processing of that length on the insulating plate 141. Moreover, since the insulating plate 141 is generally made of a rigid material such as a hard resin containing fibers, it takes time for the groove processing, and the manufacturing cost of the insulating plate 141 increases. If this insulating plate 141 is included in a part of the shim coil, there arises a problem that the shim coil itself is expensive.

  An object of this invention is to provide the MRI apparatus provided with the thin flat coil which fixed the wire.

  In order to solve the above problems, the present invention provides the following MRI apparatus. That is, a static magnetic field generation source that generates a static magnetic field in an imaging space where the subject is arranged, a gradient magnetic field application unit that applies a gradient magnetic field to the imaging space, and a high-frequency magnetic field coil that applies a high-frequency magnetic field to the subject The gradient magnetic field application unit includes a flat coil that generates at least one of a gradient magnetic field and a magnetic field for correcting a static magnetic field. The flat coil includes a sheet and a wire wound around the main plane of the sheet in a predetermined pattern and fixed to the sheet. Thus, the flat coil can be made thin by adopting a configuration in which the sheet supports the wire wound in a predetermined pattern.

  The flat coil described above can have a multilayer structure in which sheets and wires wound in a predetermined pattern are alternately stacked. Thereby, even if it is the structure which laminated | stacked multiple types of coil, a thin flat coil can be provided.

  In the case of a multi-layer structure, an insulating filling member is filled between the sheets and the wire can be embedded. Thereby, a highly rigid flat coil can be obtained. At this time, the filling member can be easily injected by providing a through hole in the sheet.

  As the above-mentioned sheet, for example, a resin sheet having an adhesive layer on the surface or a sheet in which fibers are impregnated with a resin can be used.

  The gradient magnetic field application unit can include a gradient magnetic field generation coil, a correction magnetic field generation coil, and a mold resin that integrates these coils. In this case, the gradient magnetic field generation coil and the correction magnetic field are included. At least one of the generating coils can be a flat coil having the above-described configuration.

  Moreover, according to this invention, the manufacturing method of the following flat coils is provided. That is, a conductor wire is placed in the groove of the mold member having a groove along the predetermined pattern formed on the upper surface, a sheet is placed on the mold member, the wire is bonded to the sheet, and the wire together with the sheet This is a manufacturing method for obtaining a sheet in which a wire having a predetermined pattern is fixed on the surface by removing it from the mold member.

  It is desirable to set the depth of the groove smaller than the thickness of the wire.

  In addition, after manufacturing a plurality of sheets on which the wire material is fixed, they can be stacked, a filling member is injected between the sheets and cured in a state where the wire material is embedded, thereby manufacturing a highly rigid flat coil. it can. At this time, it is desirable that the sheet is provided with a through hole for allowing the filling member to pass therethrough. Thereby, a filling member can be inject | poured between each sheet | seat from a through-hole.

  On the sheet placed on the mold member, a groove is further formed on the lower surface, and by mounting another mold member on which the wire material is disposed in the groove, a sheet having the wire material bonded to both surfaces is attached once. Can be manufactured with a press.

  As the sheet, a resin sheet having an adhesive layer on the surface can be used. Thereby, a wire and the said sheet | seat can be adhere | attached by press-contacting an adhesive material layer to a wire.

  Moreover, the fiber which impregnated resin can be used as the said sheet | seat. Thereby, a wire and a sheet | seat can be adhere | attached by heating in the state which made the sheet contact the material.

  Moreover, what was coat | covered with the material which exhibits adhesiveness by heating or contacting a predetermined solvent can be used as said wire. Thereby, a wire and a sheet | seat can be adhere | attached by heating a wire, or supplying a solvent to a wire.

  The flat coil of the present invention is a structure that does not include a mold for winding the wire in a predetermined pattern as a part of the flat coil, and the thin wire is fixed and supported by a thin sheet. A coil can be provided. The winding accuracy can be as high as that of the flat plate coil manufactured by the conventional groove filling method of Patent Document 1. Therefore, since the gradient magnetic field application unit having the same performance as the conventional one can be made thinner than the conventional one, the present invention can secure a large space (bore) for the subject in the MRI apparatus.

(First embodiment)
As shown in FIG. 1, the MRI apparatus according to the present embodiment includes a static magnetic field generating magnet 4, a gradient magnetic field generating system 21, a bed 31 on which an object 7 is mounted and arranged in an imaging space, and an object. 7 includes a transmission system 3 for applying a high-frequency magnetic field, a reception system 5 for receiving an NMR signal generated by the subject 1, a sequencer 2, a signal processing system 6, and a central processing unit (CPU) 1. is doing.

  The static magnetic field generating magnet 4 generates a uniform static magnetic field in the imaging space where the subject 7 is arranged. For example, any one of a permanent magnet system, a normal conducting system, and a superconducting system can be used.

  The transmission system 3 includes a high frequency oscillator 8, a modulator 9, a high frequency amplifier 10, and a high frequency (RF) coil 11, and the sequencer 2 controls the modulator 9 to irradiate the subject 7 with a predetermined high frequency magnetic field. .

  The gradient magnetic field generation system 21 includes a gradient magnetic field coil 13 that generates gradient magnetic fields Gx, Gy, and Gz in three directions of X, Y, and Z, a gradient magnetic field power source 12 that drives them, and a magnetic field that corrects the gradient magnetic field. A generated shim coil 22 and a shim coil power source 22 are included. The gradient magnetic field power supply 12 and the shim coil power supply 22 are connected to the sequencer 2 and cause the gradient magnetic field coil 13 and the shim coil 23 to generate a gradient magnetic field in a predetermined direction and its correction magnetic field, respectively, according to predetermined pulse sequence control.

  The gradient magnetic fields Gx, Gy, and Gz determine a slice plane for the subject 1 and give position information to the NMR signal. Of the gradient magnetic fields that provide position information, the phase encoding gradient magnetic field is normally repeatedly applied in a pulsed manner with a predetermined period while changing the magnetic field strength.

  The reception system 5 includes a reception coil 14, an amplifier 15, a quadrature detector 16, and an A / D converter 17, detects the NMR signal received by the reception coil 14 after amplification, and passes it to the CPU 1.

  The sequencer 2 controls the transmission system 3, the gradient magnetic field generation system 21, and the reception system 5 according to the pulse sequence information delivered from the CPU 1, and executes a predetermined pulse sequence, thereby performing a spin echo method, a gradient echo Various imaging methods such as a method are realized. The pulse sequence information is information such as the magnetic field intensity of the high frequency pulse and the gradient magnetic field pulse, the timing of the magnetic field pulse irradiation and the NMR signal detection, the repetition time, and the like. Conditions set by the user via the input unit 20 or predetermined conditions Is used. In any imaging method, the RF coil 11 and the gradient magnetic field coil 13 are repeatedly driven in a pulsed manner at a high speed with a predetermined repetition time by a control signal from the sequencer 2.

  The signal processing system 6 includes a CPU 1, a display 18, a recording device 19, and an input unit 20. The CPU 1 executes an internal image reconstruction program to reconstruct an image representing the nuclear spin density distribution, relaxation time distribution, and the like in the subject based on the NMR signal received from the reception system 5. The reconstructed image is displayed on the display 18. Further, it is stored in the recording device 19 as necessary. The input unit 20 receives settings such as image reconstruction conditions from the user.

Hereinafter, the structure of the magnet 4, the gradient magnetic field coil 13, and the RF coil 11 will be further described with reference to FIGS.
In the present embodiment, the static magnetic field generating magnets 4 have a disk shape, and a pair of the static magnetic field generating magnets 4 are arranged with an imaging space 200 in which the subject 7 is placed. The magnet 4 generates a static magnetic field in a direction perpendicular to the body axis direction of the subject 7 (Y direction in FIG. 1).

  As shown in FIGS. 2 and 3, the gradient coil 13 is an active shield type gradient magnetic field coil (ASGC) including a main coil 52 that generates a gradient magnetic field and a shield coil 51. The shield coil 51 is disposed closer to the magnet 4 than the main coil 52, and generates a magnetic field opposite to the magnetic field leaking from the main coil 52 to the magnet 4 side. Thereby, the gradient magnetic field leaking to the static magnetic field generating magnet 4 side is canceled, and generation of an eddy current due to the leaked magnetic field in the container of the static magnetic field generating magnet 4 is suppressed. As shown in FIG. 3, each of the main coil 52 and the shield coil 214 has a three-layer structure in which three coils for XYZ directions are stacked, and each has a disk shape.

  The shim coil 23 generates a magnetic field that cancels the higher-order error magnetic field and corrects the static magnetic field. The shim coil 23 has a structure in which a plurality of coils are stacked in multiple layers and has a disk shape. The shim coil 23 is disposed between the main coil 52 and the shield coil 51 with a predetermined interval therebetween. The structure of the shim coil 23 will be described later.

  On the imaging space 200 side of the main coil 52, the RF shield 53 and the RF coil 11 are sequentially arranged. The RF shield suppresses noise of the gradient magnetic field power source emitted from the gradient magnetic field coil 13 and shields electromagnetic coupling between the gradient magnetic field coil 13 and the RF coil 11 to reduce induction loss, thereby reducing the Q of the RF coil 11. It works to increase (Quality factor). The material of the RF shield 53 is a nonmagnetic metal such as copper or stainless steel, and is formed of a thin foil or a mesh knitted with a fine wire. The RF coil 11 that irradiates the subject 7 with the high-frequency magnetic field pulse has a flat plate shape.

  In the present embodiment, as shown in FIG. 3, the gradient magnetic field coil 13 (the main coil 52 and the shield coil 51) and the shim coil 23 are molded with a resin 31. Furthermore, a bore that is a space for a patient is formed by covering the RF coil 11 to the magnet 4 with a resin cover.

Hereinafter, the structure and manufacturing method of the shim coil 23 will be described.
The shim coil 23 has a structure in which a plurality of layers (here, five layers) are laminated, as shown in FIG. 5, on a wire layer in which conductor wires 32 are accurately arranged along a predetermined pattern as shown in FIG. . The conductor pattern of each wire layer is different, and the wire material of each layer is designed to generate a predetermined high-order correction magnetic field in a predetermined direction. Between the wire layers, an insulating sheet (adhesive sheet) 33 having adhesiveness is disposed on the surface.

  The shape of the conductor pattern of each wire layer can be designed by a known method such as a conductor position determining method for generating a predetermined higher order spherical harmonic function term described in JP-A No. 40-26368. . In the conductor pattern of each wire layer, the interval between the adjacent conductor wires 32 is not constant as shown in FIG. 4, and the wires 32 are arranged with high accuracy at positions determined by design.

  Further, as shown in FIG. 5, the adhesive sheet 33 is provided with a through-hole 34 serving as a flow path for the mold resin 31 in order to fill the gap between the wires 32 with the mold resin 31.

Next, a method for manufacturing the shim coil 23 having such a structure will be described.
In this embodiment, a die (lower die) 61 having a groove 62 in a conductor pattern shape designed as shown in FIG. 6 is prepared, and a wire 32 is inserted along the groove 62 and bonded onto the die 61. The sheet 33 is placed, and the adhesive sheet 33 is pressed against the wire 32. As a result, the wire 32 is bonded to the adhesive sheet 33, and the wire 32 is transferred to the adhesive sheet 33.

  The wire 32 preferably has a flat cross-sectional shape (rectangle with rounded corners). By using the wire having such a cross-sectional shape, the contact area with the side surface of the groove 62 is large, and the wire 32 is inserted into the groove 62 while the wire 32 is firmly held by the groove 62 of the mold 61, thereby obtaining a desired conductor pattern. You can go around. It is also possible to use a wire having another shape, such as a wire having a circular cross-sectional shape, but when the contact area with the side surface of the groove 62 is small, the wire 32 is likely to jump out of the groove 62 during scooping. It is desirable to use a jig or the like for preventing popping out. In terms of dimensions, for example, a wire having a cross-sectional width of 1 mm × height of about 2 mm can be used. In addition, the structure of the wire 32 can use the copper single wire which carried out insulation coating, such as an enamel, the compressed strand wire, the hollow conductor for flowing cooling water, etc.

  A groove 62 is formed in advance on the upper surface of the mold 61 in the shape of the conductor pattern to be formed as described above (for example, the pattern of FIG. 4). As the material of the mold 61, it is preferable to use a material that is difficult to adhere to the adhesive sheet 33. For example, a fluororesin (for example, tetrafluoroethylene resin), a metal or resin coated with a fluororesin, and the like are suitable. Further, the material of the mold 61 is required to withstand the processing for forming the groove 62 and to have rigidity to withstand pressure contact described later. On the other hand, in the manufacturing method of the present embodiment, since the mold 61 does not become a part of the manufactured flat plate shim coil 23, it is not necessary to consider the magnetic permeability and rigidity required for the shim coil 23. The material of the mold 61 can be selected considering only the necessary conditions.

  The width of the groove 62 is substantially the same as the width of the wire 32, or is slightly narrower than the width of the wire 32 when the mold 61 is made of resin and has elasticity. In this way, by not creating a gap between the groove 62 and the wire 32, the position of the wire 32 can be accurately positioned in the main plane direction. The depth of the groove 62 is made shallower than the height of the wire 32. By doing so, it is possible to adhere to the adhesive sheet 33 at the upper part of the wire 32 protruding from the groove 62.

  It is desirable to provide a recess 65 in the region between the groove 62 and the groove 62 of the mold 61 as shown in FIG. Although the adhesive force per area between the adhesive sheet 33 and the mold 61 can be reduced by using the mold 61 that is difficult to adhere to the adhesive sheet 33 as described above, the adhesive sheet 33 and the mold 61 are provided by providing the recess 65. The contact area between the mold 61 and the adhesive sheet 33 can be further reduced.

  On the other hand, the adhesive sheet 33 is used that has adhesiveness to the wire 32 and that can obtain dimensional stability against heat and tension after the wire 32 is attached. For example, as shown in FIG. 6, the adhesive sheet 33 is configured as a resin sheet 64 provided with an adhesive layer 63 on the surface, whereby the adhesiveness is set to the adhesive layer 63 and the dimensional stability is set to the resin sheet 64. It can be carried and adhesion and dimensional stability can be obtained. As the adhesive layer 63, a non-woven fabric base material impregnated with an acrylic adhesive is suitable. As the resin sheet 64, a PET (polyethylene terephthalate) rolled sheet or the like is suitable in terms of characteristics.

  It is desirable that the adhesive layer 63 has a structure in which the tip of the wire 32 is buried and fixed as shown in FIG. Thereby, since the flatness of the resin sheet 64 can be maintained and the tip of the wire 32 can be brought into contact with the adhesive material layer 63 in a wide area, it is possible to firmly bond. For example, in the case of using a flat wire (rectangle with rounded corners), the depth at which the wire 32 is buried in the adhesive layer 63 is preferably the same as the radius of curvature of the corner of the wire 32. The adhesive layer 63 is formed so as to have a thickness equal to or greater than the buried depth. For example, the thickness of the adhesive layer 62 can be set to 200 μm, and the thickness of the resin sheet 64 can be set to 188 μm.

Next, the manufacturing procedure of the shim coil 23 will be described with reference to FIGS.
First, the above-described mold (lower mold) 61 and the wire 32 are prepared, and the wire 32 is embedded along the groove 62 of the mold 61 (step 71 in FIG. 7). Thereby, as shown in FIG. 6, the wire 32 is wound around along the groove 62 of the lower mold 61, and the upper end of the wire 32 is in a state of protruding from the groove 62.

  On the lower mold 61 in this state, as shown in FIG. 8, the adhesive sheet 33 is mounted with the adhesive layer 63 facing the wire 32 side, and the upper mold 81 is placed thereon (step 72). . The adhesive sheet 33 is previously provided with a through hole 34 serving as a flow path for the mold resin 31 at a predetermined position. This is disposed between the upper and lower press plates 82 and 83 of the press device, and the upper and lower molds 81 and 61 are pressed (step 73). Thereby, the adhesive sheet 33 is pressed against the wire 32, and the upper end of the wire 32 is bonded to the adhesive sheet 33. By peeling the adhesive sheet 33 to which the wire 32 is adhered from the lower mold 61, the conductor pattern formed by the wire 32 is transferred to the adhesive sheet 33.

  By doing so, as shown in FIG. 9, a wire layer in which the wire 32 having a desired conductor pattern is fixed on one surface of the adhesive sheet 33 is obtained. When the shim coil of FIG. 5 is formed, five layers of this wire layer are formed using five types of lower molds 61 in which grooves 62 having different conductor patterns are formed. By stacking five layers, the five layers are fixed to each other. The spacing between the five layers of the adhesive sheet 33 is the same as the thickness (height) of the wire 32. Thereby, the shim coil 23 of FIG. 5 can be manufactured. In addition, it is desirable to provide a large number of through holes 34 so that the mold resin 31 is filled between all the wires 32.

  The formed shim coil 23 is disposed between the main coil 52 and the shield coil 51 of the gradient magnetic field coil 13 manufactured separately via a spacer having a predetermined thickness, and the resin 31 is supplied to the whole. Mold. Since the through-hole 34 is provided in the adhesive sheet of the shim coil 23, the mold resin 31 can be easily filled in the gap between the wires 32. Thereby, the gradient magnetic field coil 13 and the shim coil 23 can be integrated and the rigidity can be increased. For example, an epoxy resin can be used as the mold resin 31.

  As the upper die 81, it is possible to use a groove having a desired conductor pattern groove 62 on the lower surface in the same manner as the lower die 61. By inserting the wire 32 in advance in the groove of the upper mold 81 and using the adhesive sheet 33 provided with the adhesive layer 63 on both sides, the adhesive sheet 33 can be formed as shown in FIG. It is also possible to form a wire 32 having a desired conductor pattern on both sides. Thereby, the press frequency | count can be reduced and the shim coil 23 by which the several layer was laminated | stacked can be manufactured efficiently.

  In the present embodiment, the dies 61 and 81 are used only at the time of manufacture and are not included in a part of the manufactured shim coil 23. Therefore, since the thickness of the coil of one layer can be reduced to the sum of the diameter (height) of the wire 32 and the thickness of the adhesive sheet 33, an extremely thin shim coil can be manufactured. Thereby, since the thickness of the gradient magnetic field coil 13 including the shim coil 23 can be reduced, it is possible to ensure a large height of the bore which is a space in which the subject 7 is disposed.

  In addition, since a large number of through holes 34 can be easily formed in the thin adhesive sheet 33, the mold resin can be easily filled between the wire materials 32, and the wire material 32 is firmly and accurately fixed while being the thin shim coil 23. Moreover, a highly rigid shim coil can be obtained.

  In addition, since the dies 61 and 81 are used only at the time of manufacture and are not included in a part of the manufactured shim coil 23, the shim coil 23 can be lowered while using the expensive dies 61 and 81 with grooves. Can be manufactured at low cost.

  The manufacturing method of the present embodiment is particularly effective for the shim coil 23 having a small current value and requiring a plurality of coils. However, not only the shim coil 23 but also the gradient magnetic field coil 13 can be manufactured by the above manufacturing method in the same manner as the shim coil 23. Further, by combining the low resistance gradient magnetic field coil 13 manufactured by forming a groove in the conductor plate with the shim coil 23 manufactured by the manufacturing method of the present embodiment, a high performance gradient magnetic field coil and shim coil 23 are obtained. This is preferable.

Conversely, the gradient magnetic field coil 13 manufactured by the manufacturing method of the present embodiment and the shim coil 23 formed from a conductor plate can be used.
6 and 8 illustrate the structure in which the upper and lower press plates 82 and 83 are fastened with the press bolts 84 as an example. However, as long as the molds 81 and 61 can be pressed from above and below, various types of press machines can be used. Can be used. For example, a hydraulic press can be used. In addition, if it tightens with the volt | bolt 84, the direction which put and tightened the disc spring between the upper and lower press plates 82 and 83 and the volt | bolt 84 rather than a spring washer can be tightened more stably.

(Second Embodiment)
As a second embodiment, another method for manufacturing the shim coil 23 that can be used in the MRI apparatus of the present invention will be described.

  In the first embodiment, the wire 32 is bonded (transferred) to the insulating sheet (resin sheet) 33 using the adhesive sheet 33, that is, adhesive having normal temperature, but by applying heat to cure it. It is also possible to bond. The overall configuration of the MRI apparatus and the structure of the shim coil 23 are the same as those in the first embodiment except for the adhesive sheet 33.

  In the second embodiment, instead of the adhesive sheet 33 of the first embodiment, a sheet (so-called prepreg) 74 in which a fiber is impregnated with a semi-cured resin is used as a lower mold 61 in step 72 of FIG. And press (step 73).

  By heating the prepreg 74 in this state, the resin of the prepreg 74 is cured and bonded to the wire 32. There are various types of prepregs depending on the resin and the base material. In general, the resin may be heated at several hundreds of degrees for several hours. Thereafter, the wire 32 is fixed to the prepreg 74 by cooling.

  In order to heat the prepreg 74 in step 73, for example, a method of putting the whole sandwiched between the upper and lower press plates 82 and 83 into a heating furnace as it is can be used. In this case, it is necessary to form the molds 61 and 81, the press plates 82 and 83, etc. with a material having heat resistance and a low coefficient of thermal expansion.

  On the other hand, as a simpler heating method, it is possible to use a method (electric current heating method) in which a current is passed through the wire 32 and heated.

  When conducting current heating, the power supply 111 for current heating is connected to both ends of the wire 32 in a pressed state as shown in FIG. 8, and a temperature sensor 112 is attached to the coil wire 32, and its output is output. Is input to the temperature controller 113. The temperature of the wire 32 is controlled by PID control by the temperature controller 113. Thereby, the prepreg 74 can be heated to a predetermined temperature by the heat generation of the wire 32, and the wire 32 can be bonded to the prepreg 74.

  In order to efficiently heat and cure the prepreg 74 by energization heating, it is more preferable to use a press apparatus having a structure as shown in FIG. That is, the soaking plate 121 and the heat insulating plate 122 are arranged so as to sandwich the lower mold 61 and the upper mold 81. The heat equalizing plate 121 makes the temperature near the prepreg 74 uniform, and the heat insulating plate 122 acts to prevent heat from escaping to the outside. As shown in FIG. 4, the flat shim coil 23 has a dense and dense conductor pattern formed by the wire 32, and the ratio thereof is several times larger. Therefore, the amount of heat generation varies greatly depending on the position, and a temperature difference is likely to occur. The lower limit of the heating temperature is equal to or higher than the minimum temperature necessary for curing the prepreg 74, and the upper limit of the temperature needs to be designed to be equal to or lower than the heat resistance temperature of the insulating coating of the wire rod 32 (for example, enameled wire). By arranging the soaking plate 121 behind the molds 81 and 61, the temperature distribution can be suppressed within a predetermined temperature range.

  Moreover, since the heat escaping to the outside can be reduced by using the heat insulating plate 122, the prepreg 74 can be efficiently heated, and the power supplied to the wire 32 can be reduced, thereby reducing the manufacturing cost. Can be reduced. As a material of the heat insulating plate 122, an inorganic plate that can withstand pressing can be used.

(Third embodiment)
As a third embodiment, another method for manufacturing the shim coil 23 that can be used in the MRI apparatus of the present invention will be described.

  In the first and second embodiments, the wire 32 does not have adhesiveness, and the side of the sheet 33 such as an adhesive sheet or prepreg has adhesiveness. However, in the third embodiment, the wire side is adhesive. The case of providing the will be described below.

  As a first method for imparting adhesiveness to the wire 32, a method of applying an adhesive to the outer peripheral surface of the wire 32, embedding it in the groove 62 of the mold 61, laminating an adherend sheet thereon, and pressurizing it. Can be used. Also, depending on the type of adhesive, it can be cured by heating in a pressed state. However, it is necessary to select an adhesive according to the material of the mold 61 so that the adhesive does not adhere to the mold 61.

  As a second method, a self-bonding wire can be used as the wire 32. The self-bonding wire is obtained by further coating the surface of a conventional coated wire with a material layer (bonding layer) having a property of causing adhesiveness by heating or application of a solvent. Therefore, in steps 72 and 73 of FIG. 7, the fusion layer is activated by heating the wire 32 or applying a solvent, and the wire 32 can be bonded to the insulating sheet.

  For example, when using a self-bonding wire that is fused by adhering alcohol as the wire 32, after squeezing the wire 32 on the mold 61 in step 71 of FIG. 7, the surface of the wire is wiped with alcohol and activated. In step 72, an insulating sheet such as PET can be stacked thereon and bonded in the step 73 by pressing. In the case of a self-bonding wire that is fused by heating, it can be adhered to an insulating sheet such as PET by energizing and heating using a PET sheet instead of a prepreg.

1 is a block diagram showing the overall configuration of an MRI apparatus according to a first embodiment. Sectional drawing which shows arrangement | positioning of the magnet 4, the gradient magnetic field coil 13, and the shim coil 23 of the MRI apparatus of FIG. FIG. 3 is a sectional view showing a configuration in which the gradient magnetic field coil 13 (shield coil 51 and main coil 52) and shim coil 23 of FIG. FIG. 3 is an explanatory diagram showing an example of a conductor pattern of the shim coil 23 of FIG. 2. FIG. 3 is an explanatory diagram showing a layer structure of the shim coil 23 of FIG. 2. Sectional drawing which shows the structure which pinched | interposed the type | mold 61 with which the wire 32 was arrange | positioned, and the adhesive sheet 33 in 1st Embodiment with the press apparatus. Explanatory drawing which shows the manufacturing flow of a flat shim coil in 1st Embodiment. The notch perspective view which shows the structure which pinched | interposed the type | mold 61 and the adhesive sheet 33 with which the wire 32 was arrange | positioned in the 1st Embodiment with the press apparatus. The perspective view which shows the sheet | seat 33 with which the wire 32 was fixed obtained by 1st Embodiment. The perspective view which shows the sheet | seat 33 with which the wire 32 was fixed to both surfaces obtained by 1st Embodiment. The block diagram which shows the circuit structure at the time of heating by supplying with electricity to the wire 32 in 2nd Embodiment. Sectional drawing which shows the structure of the press apparatus in the case of heating by supplying with electricity to the wire 32 in 2nd Embodiment. (A) is a notch perspective view which shows the structure of the flat coil manufactured by forming the groove | channel 132 in the conventional conductor plate 131, (b) is an enlarged view of a figure (a). The notch perspective view of the flat coil of the structure which embedded the wire in the groove | channel of the conventional insulating board 141. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Central processing unit (CPU), 2 ... Sequencer, 3 ... Transmission system, 4 ... Magnet for static magnetic field generation, 5 ... Reception system, 6 ... Signal processing system, 11 ... High frequency (RF) coil, 13 ... Gradient magnetic field coil , 23 ... Shim coil, 32 ... Wire rod, 33 ... Adhesive sheet, 34 ... Through-hole, 51 ... Shield coil, 52 ... Main coil, 53 ... RF shield, 61 ... Mold, 81 ... Upper die, 82, 83 ... Upper and lower presses Plate, 200 ... imaging space.

Claims (9)

A first step of disposing a conductor wire in the groove of a mold member in which grooves along a predetermined pattern are formed on the upper surface ;
A second step of placing a sheet on the mold member and bonding the wire to the sheet ;
And removing the wire together with the sheet from the mold member to obtain a sheet in which the wire of the pattern is fixed on the surface ,
A method of manufacturing a shim coil, wherein the height of the wire is higher than the depth of the groove, and an upper portion of the wire protrudes from the groove. A first step of disposing a conductor wire in the groove of a mold member in which grooves along a predetermined pattern are formed on the upper surface;
A second step of placing a sheet on the mold member and bonding the wire to the sheet;
And removing the wire together with the sheet from the mold member to obtain a sheet in which the wire of the pattern is fixed on the surface,
The method of manufacturing a shim coil according to claim 1, wherein the wire has a height greater than a width, and the groove has a width corresponding to the width of the wire. 3. The shim coil manufacturing method according to claim 2, wherein a height of the wire is higher than a depth of the groove, and an upper portion of the wire protrudes from the groove. In the shim coil manufacturing method according to claim 1 or 3, in the second step, an upper mold is disposed on the sheet, and the sheet is pressed against the wire,
The method of manufacturing a shim coil, wherein a distance between the mold member and the upper mold is larger than a thickness of the sheet. 4. The shim coil manufacturing method according to claim 1 , wherein a resin sheet having an adhesive layer on a surface thereof is used as the sheet, and the wire and the sheet are pressed by pressing the adhesive layer to the wire. A method of manufacturing a shim coil , characterized in that: The shim coil manufacturing method according to claim 1 or 3 , wherein a fiber impregnated with resin is used as the sheet, and the sheet and the sheet are heated by heating the sheet in contact with the wire. A method of manufacturing a shim coil , characterized by bonding. The shim coil manufacturing method according to claim 1 or 3 , wherein the wire is heated or coated with a material that exhibits adhesiveness by contact with a predetermined solvent, and the wire is heated, or The method of manufacturing a shim coil , wherein the wire and the sheet are bonded by supplying the solvent to the wire. A static magnetic field generation source for generating a static magnetic field in an imaging space in which the subject is arranged, a gradient magnetic field applying unit for applying a gradient magnetic field to the imaging space, and a high-frequency magnetic field coil for applying a high-frequency magnetic field to the subject A magnetic resonance imaging apparatus comprising:
The gradient magnetic field application unit includes a shim coil that generates at least one of the gradient magnetic field and the magnetic field that corrects the static magnetic field,
The magnetic resonance imaging apparatus according to claim 1, wherein the shim coil is manufactured by the method for manufacturing a shim coil according to claim 1. A static magnetic field generation source for generating a static magnetic field in an imaging space in which the subject is arranged, a gradient magnetic field applying unit for applying a gradient magnetic field to the imaging space, and a high-frequency magnetic field coil for applying a high-frequency magnetic field to the subject Have
The gradient magnetic field application unit includes a flat coil that generates at least one of the gradient magnetic field and the magnetic field for correcting the static magnetic field,
The flat coil has a multilayer structure in which sheets and wires wound in a predetermined pattern are alternately laminated,
An insulating filling member is filled between the sheets, and the wire is embedded,
A magnetic resonance imaging apparatus, wherein the sheet is provided with a through hole for injecting the filling member.

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