JP4847236B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention measures nuclear magnetic resonance (hereinafter referred to as `` NMR '') signals from hydrogen, phosphorus, etc. in a subject and images nuclear density distribution, relaxation time distribution, etc. More particularly, the present invention relates to a shim member that corrects the static magnetic field uniformity and a mechanism that suppresses temperature fluctuations of the shim tray.

  MRI equipment measures NMR signals generated by nuclear spins that make up a subject placed in a static magnetic field, especially human tissue, and forms the shape and function of its head, abdomen, limbs, etc. in two dimensions or This is a device for imaging in three dimensions. In imaging, the NMR signal is given different phase encoding depending on the gradient magnetic field, frequency-encoded, and measured as time series data. The measured NMR signal is reconstructed into an image by two-dimensional or three-dimensional Fourier transform.

  In order to acquire a high-quality image, it is necessary to adjust the uniformity of the static magnetic field as high as possible and stably maintain the high uniformity. There are two methods for adjusting the uniformity of the static magnetic field: an active shimming method in which shim coils are arranged and the current is controlled, and a passive shimming method in which magnetic members such as shim iron are arranged. In the uniformity adjustment by this passive shimming method, when the temperature of the shim iron changes, its magnetization characteristics change, so that the static magnetic field uniformity also changes. As a result, the image quality is deteriorated. The main cause of temperature fluctuation of shim iron is that Joule heat generated in the gradient coil conducts heat to shim iron. In particular, recent high-function sequences require high gradient magnetic field strength and high static magnetic field uniformity. When the amount of current is increased due to the high gradient magnetic field strength, Joule heat increases in proportion to the square of the current, and the static magnetic field uniformity may be further deteriorated by the heat. For this reason, a structure that establishes the opposite high gradient magnetic field strength and high static magnetic field uniformity is required.

In Patent Document 1, a shim iron piece is fixed between a gradient magnetic field coil and a magnet, and the gradient magnetic field coil and the shim iron are separated. Thereby, it becomes possible to suppress the temperature fluctuation of the shim iron due to the direct heat transfer from the gradient coil.
JP 2002-336215 A

  In the configuration described in Patent Document 1, convection using air as a medium between the gradient coil and the shim iron, the gradient coil and the shim iron as the heat transfer form from the gradient coil to the shim iron. There is heat conduction through the fixed member and radiation between the gradient coil and shim iron. If the interval between the gradient coil and shim iron is narrow, the amount of heat transfer by the surrounding gas increases. On the other hand, the amount of heat transfer by radiation is a constant value regardless of the distance between them. Further, the heat conduction through the member for fixing the gradient coil is local and the number of the fixing members is small, so the influence of the heat conduction is limited. Therefore, in order to suppress the temperature rise of shim iron, it is necessary to reduce the amount of heat transfer by this convection and radiation. However, Patent Document 1 does not consider the amount of heat transfer by convection and radiation.

  Therefore, an object of the present invention is to suppress the temperature fluctuation of the shim member by reducing the amount of heat transfer by convection and radiation between the gradient magnetic field coil and the shim member.

In order to achieve the above object, the MRI apparatus of the present invention is configured as follows. That is, a static magnetic field generating means for generating a static magnetic field, a gradient magnetic field coil for generating a gradient magnetic field in the space of the static magnetic field, a shim member for adjusting the uniformity of the static magnetic field, and a static magnetic field generating means and a gradient are held. Uniformity adjusting means having a shim tray disposed between the magnetic field coil and means for suppressing temperature fluctuation of the shim member are provided.

  According to the MRI apparatus of the present invention, the amount of heat transfer by convection and radiation between the gradient magnetic field coil and the shim member can be reduced, so that temperature fluctuation of the shim member can be suppressed. Thereby, for example, even in a high-function sequence that requires a high gradient magnetic field strength and a high static magnetic field uniformity, a good image with little image quality deterioration can be obtained.

  Hereinafter, preferred embodiments of the MRI apparatus of the present invention will be described in detail with reference to the accompanying drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments of the invention, and the repetitive description thereof is omitted.

  First, an overall outline of an example of an MRI apparatus to which the present invention is applied will be described with reference to FIG. As shown in FIG. 1, the MRI apparatus is provided with a static magnetic field magnet 12 that generates a static magnetic field to be applied to the subject 10 placed on the bed 15. The static magnetic field generating source of the static magnetic field generating magnet 12 may be a superconducting coil, a normal conducting coil, or a permanent magnet. Further, a gradient magnetic field coil 14 that generates gradient magnetic fields in three different directions applied to the subject 10, for example, X, Y, and Z axis directions, is provided. A gradient magnetic field is applied with one of these three directions as a slice direction, a phase encoding direction, and a frequency encoding direction. Further, an RF coil 16 that generates a high-frequency magnetic field pulse to be applied to the subject 10, that is, an RF pulse, and an RF probe 18 that detects an NMR signal or echo signal generated from the subject 10 are provided. Further, a signal processing unit 20 that reconstructs an image based on an echo signal obtained by the RF probe 18 and a display unit 22 that displays the image reconstructed by the signal processing unit 20 are provided.

  The operation of the MRI apparatus configured as described above will be described. A static magnetic field is applied to the subject 10 by the static magnetic field magnet 12. A slice selection gradient magnetic field is applied from the gradient magnetic field coil 14 to the observation site (for example, the heart) of the subject 10 to which the static magnetic field is applied in accordance with the current from the gradient magnetic field power supply 26 based on the command of the control unit 24. Is done. Further, along with the application of the slice selection gradient magnetic field, the observation region is irradiated with RF pulses from the RF coil 16 in accordance with the high-frequency current from the high-frequency transmission unit 28 based on the command of the control unit 24. As a result, an NMR phenomenon is induced in a nucleus (for example, a hydrogen nucleus) in the constituent material of the observation site, and an echo signal is generated. In order to acquire position information of the observation site where the NMR phenomenon has been induced, a phase encoding gradient magnetic field and a frequency encoding gradient magnetic field are applied from the gradient coil 14 to the echo signal. This echo signal is detected by the signal detection unit 30 from the RF probe 18 based on a command from the control unit 24. Based on the detected echo signal, the image of the observation site is reconstructed two-dimensionally or three-dimensionally by the signal processing unit 20, and the reconstructed two-dimensional or three-dimensional image is displayed on the display unit 22.

  Next, the structure around the magnet of the MRI apparatus will be described with reference to FIG. FIG. 2 is a diagram showing an outline of a longitudinal section of the static magnetic field magnet 12 (a section parallel to the static magnetic field direction). The static magnetic field magnets 12 are arranged to face each other and form a uniform magnetic field region 55. The subject 10 (not shown) is disposed in the uniform magnetic field region 55 and lies on the bed 15 (not shown). A concave portion is provided on each of the pair of upper and lower magnet containers on the uniform magnetic field region 55 side, and the gradient magnetic field coil 14 and the shim tray 56 are disposed in the concave portion. The gradient magnetic field coil 14 is disposed to face the uniform magnetic field region 55 and is fixed between the static magnetic field magnet 12 and the uniform magnetic field region 55. The RF coil 16 is disposed to face the uniform magnetic field region 55 and is fixed between the uniform magnetic field region 55 and the gradient magnetic field coil 14. The shim tray 56 is disposed between the static magnetic field magnet 12 and the gradient magnetic field coil 14, and holds a magnetic material piece such as iron or a magnet piece.

  An example of the shim tray 56 is shown in FIG. FIG. 3 shows an upper left quarter portion of the disc-shaped shim tray 56, (a) shows a top view and (b) shows a cross-sectional view. Other parts not shown are the same as the upper left quarter part. The shim tray 56 is provided with holes 60 at a plurality of desired positions, and shim iron (not shown) having predetermined magnetic characteristics is fixed to the holes 60. The shim tray 56 is made of a non-magnetic member such as a metal such as SUS or aluminum, or a resin such as a glass epoxy laminate.

(First embodiment)
A first embodiment of the MRI apparatus of the present invention will be described. In this embodiment, a reflective cooling member is disposed on at least one of the opposing surfaces of the gradient coil and shim tray. Preferably, a cooling pipe is arranged at the outer edge of the shim tray, the reflective cooling member and the cooling pipe are brought into thermal contact with each other to form the shim tray, and the coolant is allowed to flow through the cooling pipe to cool the shim tray. Keep the temperature constant.

First, a structural example for suppressing radiant heat from the gradient magnetic field coil 14 of the shim tray 56 will be described with reference to FIGS.
FIG. 4 is a cross-sectional view around the shim tray 56 including the cooling structure of the shim tray 56, and particularly shows the upper portion of the static magnetic field magnet 12. FIG. Although FIG. 4 shows the concave portion in an emphasized manner, the actual concave region is narrower in the direction of the static magnetic field. The lower part of the static magnetic field magnet 12 has an arrangement structure that is substantially symmetrical with the upper part shown in FIG. 4 with respect to the horizontal plane including the center of the static magnetic field.
A reflection cooling plate 57 is attached to the surface of the shim tray 56 on the gradient coil 14 side. The reflective cooling plate 57 contacts the cooling pipe 58 at the outer periphery of the shim tray 56. The cooling pipe 58 is supplied with a refrigerant controlled at a constant temperature by a heat exchanger (not shown) outside the examination room. In this way, the shim tray 56 is cooled by the refrigerant through the cooling pipe 58 and the reflective cooling plate 57. (The refrigerant can be a liquid such as water or a gas such as air, but water is preferred.)

  A reflective cooling plate 57 having a low emissivity may be attached to the surface of the gradient magnetic field coil 14 facing the shim tray 56. The reflection cooling plate 57 may be attached to at least one of the opposing surfaces of the gradient magnetic field coil 14 and the shim tray 56.

  Further, a powdery low-emissivity member 59 such as silica or lime is applied to the entire surface of the gradient magnetic field coil 14 in order to suppress the radiation heat from the surface and to reduce the emissivity. Alternatively, a plate or foil such as aluminum or copper may be bonded, or these may be vapor-deposited and surface coated. In order to suppress the generation of eddy currents, the thickness should be as thin as possible, and is preferably several tens to several hundreds of μm. When the reflective cooling plate 57 is attached to the surface of the gradient coil 14 facing the shim tray 56, the low emissivity member 59 is applied on the reflective cooling plate 57.

  FIG. 5 shows an example of the reflective cooling plate 57. FIG. 5 shows a top view of the upper left 1/4 portion of the disc-shaped reflection cooling plate 57, and other portions not shown are the same as the upper left 1/4 portion. The reflection cooling plate 57 is preferably made of a non-magnetic material with high thermal conductivity, and for example, aluminum, copper, titanium, or the like is suitable. Further, the emissivity of the surface of the reflective cooling plate 57 is made as small as possible by polishing or the like. In order to prevent image deterioration due to eddy current, a slit 61 is provided on the surface. The width of the slit 61 is preferably high thermal conductivity by reducing it to about 1 mm. Further, the longitudinal direction of the slit is preferably arranged in a direction orthogonal to the eddy current flowing in the reflective cooling plate 57, and FIG. 5 shows an example in which the slits 61 are arranged radially. In addition, when the reflective cooling plate 57 is thick, eddy current increases and the reflective cooling plate 57 itself generates heat. However, if the reflective cooling plate 57 is thinned, the heat conduction is reduced. Therefore, in practice, the thickness is determined in consideration of the magnitude of eddy current and the amount of heat transfer by heat conduction. Specifically, it can be several hundred μm to several mm. If the thickness is thin and the expected heat removal amount cannot be obtained, the cooling pipe 58 may be arranged in a plurality of turns in the shim tray 56 (details are described in the fourth embodiment).

  Further, as shown in FIG. 6, a cooling structure 65 using a cooling pipe may be provided in the gradient magnetic field coil 14 and connected to the shim tray cooling pipe 58 (the connecting portion is not shown). As the order of flowing the refrigerant, it is better to flow the refrigerant first to the shim tray cooling pipe 58, but it may be later. In the above structure, the cooling structure of the gradient magnetic field coil 14 and the cooling structure of the shim tray 56 are connected in order to suppress the increase in cost and system, but these are separated from the heat exchanger as separate cooling systems. A coolant controlled to a temperature may be passed. By cooling the gradient magnetic field coil 14 in this way, the energization current of the gradient magnetic field coil 14 can be increased.

  Next, a structural example that suppresses the amount of heat transfer by convection and heat conduction of the ambient gas around the shim tray 56 will be described. In order to suppress heat transfer due to convection and heat conduction, it is preferable to insert a heat insulating material between the gradient magnetic field coil 14 and the shim tray 56. The thicker the heat insulating material, the better the heat insulating effect, which is effective when the gap between the gradient coil and the shim tray is large. FIG. 13 shows a specific example of the heat insulating material arrangement. In order to increase the heat insulating effect, the diameter of the heat insulating material is larger than the diameter of the gradient magnetic field coil 14 and the shim tray 56, but may be the same diameter. As the heat insulating material, ceramic fiber, rock wool, foamed urethane, polyurethane foam and the like are suitable.

Even if the surroundings of the gradient magnetic field coil 14 and the shim tray 56 are evacuated and the heat insulating effect of the vacuum is used, the amount of heat transfer due to convection and heat conduction can be suppressed. Since a specific example in the case of creating a vacuum is described in Patent Document 2, for example, this can be used.
Japanese Patent Application No. 9-327205

  With the structure of the present embodiment described above, the Joule heat generated in the gradient magnetic field coil 14 and the heat transmitted to the shim tray 56 are attached to at least one of the surface of the shim tray 56 and the surface of the gradient magnetic field coil 14. It moves to the refrigerant in the cooling pipe 58 via the reflective cooling plate 57 having good heat conduction, and is discharged outside the examination room. Further, heat transfer due to radiation is suppressed by the low emissivity member 59 applied to the surface of the gradient magnetic field coil 14. By these, shim members such as shim irons that are discretely arranged in the shim tray hole 60 are uniformly cooled, local temperature fluctuations are suppressed, and temperature changes with time are also suppressed to keep the temperature constant. Can do. As a result, since the static magnetic field uniformity is stable, image deterioration can be prevented. Further, since the variation of the static magnetic field uniformity is suppressed by cooling the shim tray 56, it is possible to stably cope with a high-function sequence such as spectroscopy.

(Second Embodiment)
Next, a second embodiment of the MRI apparatus of the present invention will be described. The cooling structure of the shim tray of this embodiment is a form in which the temperature change of the shim tray is indirectly suppressed by disposing the cooling means in the magnet container and exhausting the heat transmitted by the radiation from the gradient coil to the outside. is there.
Hereinafter, detailed description of the same parts as those of the first embodiment will be omitted.

FIG. 7 shows an example of the cooling structure of the shim tray of this embodiment.
FIG. 7 shows a cross-sectional view of the upper magnet container 12. Note that FIG. 7 shows the concave portion with emphasis, but the actual concave region is narrower in the direction of the static magnetic field. The lower part of the magnet container 12 has a substantially symmetric arrangement structure with the upper part shown in FIG. 7 with respect to the horizontal plane including the center of the static magnetic field. A plate 70 with good thermal conductivity such as aluminum or copper is attached to the surface of the recess of the magnet container 12 parallel to the static magnetic field direction, and the surface of the plate 70 has an emissivity to promote heat transfer by radiation Apply high black body paint 71. This black body paint 71 has an emissivity extremely close to 1.

  In addition, a cooling pipe 72 connected to an unshown outside heat exchanger (not shown) is arranged in contact with the plate 70, and the refrigerant flows into the cooling pipe 72, so that mainly the heat of the plate 70 is released to the outside. To do. As a result, the heat transmitted from the gradient coil 14 to the magnet container 12 by radiation is transferred to the plate 70 and released to the outside through the refrigerant flowing in the cooling pipe 72 that is in contact with the plate 70 due to the heat conduction of the plate 70. Is done. The refrigerant may be liquid or gas, but water is preferred.

  FIG. 8 shows another example of the cooling structure of the shim tray of this embodiment. FIG. 8 shows a cross-sectional view of the upper magnet container 12. The cooling structure shown in FIG. 8 is a structure that increases the cooling efficiency by providing fins 73 on the surface parallel to the static magnetic field direction of the concave portion of the magnet container 12 instead of the plate 70 and the black body paint 71 of FIG. . Each of the fins 73 is arranged at an interval so as to extend in a direction perpendicular to the direction of the static magnetic field. The number of fins 73 may be one or more. FIG. 8 shows a long-diameter fin 73-1 arranged so as to extend between the gradient coil 14 and the shim tray 56, and a plurality of short-diameter pieces arranged on the opposing surface of the side surface of the gradient coil 14. An example of the fin 73-2 is shown. The plate 70 is arranged in the same manner as in FIG. 7, and the fins 73 and the cooling pipe 72 are arranged thereon, for example, by welding or bolt fastening. After the shim tray 56 is installed, the fins 73 are attached, and then shim iron (for example, M8 and M6 bolts) is attached. In particular, the shim tray is not taken out.

  With the structure of the present embodiment described above, the heat transferred from the gradient coil to the magnet container by radiation is efficiently released to the outside, so that the temperature in the recess can be kept constant. it can. Thereby, the time change of the temperature of shim members, such as shim iron currently arrange | positioned at a shim tray, can be suppressed, and temperature can be kept constant. As a result, the static magnetic field uniformity is stabilized, so that image deterioration can be prevented.

(Third embodiment)
Next, a third embodiment of the MRI apparatus of the present invention will be described. The cooling structure of the shim tray of the present embodiment is a form in which the shim tray is directly cooled by allowing the refrigerant to pass through the shim tray. Hereinafter, detailed description of the same parts as those of the first embodiment will be omitted.
FIG. 9 shows an example of the structure of the shim tray of this embodiment. FIG. 9 shows a cross-sectional view of the shim tray in the direction of the static magnetic field. The holder 95 and the side plate 96 are sandwiched and fixed by a pair of sandwich plates 94. The holder 95 is a member that holds a shim member such as shim iron, and is provided with a screw hole. A shim member is screwed into the screw hole and fixed to the holder 95. The sandwich plate 94, the holder 95, and the side plate 96 form a structure with a gap between the holders 95, preferably a honeycomb structure. Further, a pair of sockets 97 for entrance / exit for allowing the refrigerant to pass through the gap is provided in a part of the side plate 96.

  With such a structure, the refrigerant flowing from one socket 97 fills the gap in the shim tray, absorbs heat transferred to the shim tray, and flows out of the other socket 97 to the outside, thereby reducing the heat in the shim tray. Can be released to the outside. In addition, illustration of the circulation pump and piping for allowing a refrigerant to pass through a space | gap is abbreviate | omitted. The refrigerant may be liquid or gas, but water is preferred.

  As the sandwich plate 94, aluminum or titanium may be used as the reflection cooling plate 57, or the reflection cooling plate 57 may be attached to the surface using resin. Further, the sandwich plate 94 is provided with a through hole for allowing a shim member such as shim iron to pass therethrough. The through hole and the holder 95 are arranged so that the positions of the through hole and the screw hole of the holder 95 coincide with each other. The arrangement position of is adjusted.

  FIG. 10 shows an example of the holder 95. (a) shows an example of a holder with a square outer shape, and (b) shows an example of a holder with a cylindrical outer shape, but the outer shape of the holder 95 is not limited to these shapes, and may be other shapes. . The holder 95 is provided with a hole or screw hole 98 for fixing a shim member such as shim iron. Such a holder 95 is fixed in the shim tray 56 so that the hole or screw hole 98 and the through hole of the sandwich plate 94 penetrate each other.

  FIG. 11 shows another example of the structure of the shim tray of this embodiment. FIG. 11 shows a cross-sectional view of the upper magnet container 12. The lower part of the magnet container 12 has an arrangement structure that is substantially symmetrical to the upper part shown in FIG. 11 with respect to the horizontal plane including the center of the static magnetic field. As shown in FIG. 11, the cooling pipe 58 is fixed to the magnet side of the shim tray 56. FIG. 12 shows an example of the piping structure of the cooling pipe 58. FIG. 12 shows a top view of the shim tray 56 on the cooling pipe 58 side. Generally, a temperature distribution is generated in the gradient coil 14 that is energized. This is because the heat generation amount is increased because the conductor width of the portion where the turn density is high is small (= the cross-sectional area of the conductor is small). Therefore, the piping pattern of the cooling pipe 58 is adjusted in advance according to the temperature distribution of the gradient magnetic field coil 14 and configured. That is, the piping pattern of the cooling pipe 58 is configured so that the cooling pipe 58 is arranged in the vicinity of a portion with a high turn density. FIG. 12 shows an example of a spiral arrangement pattern. The pipe density in the end region having a high turn density is increased.

  FIG. 14 shows the turn density distribution of the Y coil in the gradient magnetic field coil 14, and FIG. 15 shows a specific example of the pattern arrangement of the cooling pipe 58 corresponding to FIG. In FIG. 14, a portion with a high turn density is indicated by a hatched portion. As shown in Fig. 15, by arranging a large number of cooling pipes in a place where the turn density is high and increasing the piping density, and by arranging a small number of cooling pipes in a place where the turn density is low and reducing the piping density, It can be cooled efficiently.

  With the structure of the present embodiment described above, the shim tray can be directly cooled by allowing the refrigerant to pass through the shim tray, so that shim members such as shim iron can be uniformly cooled to suppress local temperature fluctuations. In addition, the temperature can be kept constant by suppressing the time change of the temperature. As a result, the static magnetic field uniformity is stabilized, so that image deterioration can be prevented.

The above is description of each embodiment of the cooling structure of the shim tray in the MRI apparatus of the present invention. However, the MRI apparatus of the present invention is not limited to the contents disclosed in the description of the above embodiment, and may take other forms based on the gist of the present invention.
For example, the above-described embodiments have described the cooling structure of the shim tray in the vertical magnetic field type MRI apparatus, but the present invention can be similarly applied to a horizontal magnetic field type MRI apparatus.
Further, any plurality of shim tray cooling structures disclosed in the embodiments may be combined.

The figure which shows an example of the magnetic resonance imaging apparatus of this invention. The figure which shows especially the magnet part of the magnetic resonance imaging apparatus of this invention. The figure which shows the shim tray shape of the Example of this invention. The figure which shows the cooling structure of the Example of this invention. The figure which shows the reflective cooling plate of the Example of this invention. The figure which shows the cooling structure of the Example of this invention. The figure which shows the cooling structure of the Example of this invention. The figure which shows the cooling structure of the Example of this invention. The figure which shows the shim tray structure of the Example of this invention. The figure which shows the holder of the Example of this invention. The figure which shows the cooling structure of the Example of this invention. The figure which shows the cooling pipe piping pattern of the Example of this invention. The figure which shows the example which arrange | positions a heat insulating material between a gradient magnetic field coil and a shim tray. The figure which shows the turn density distribution of the gradient magnetic field coil 14 of a Y coil. FIG. 15 is a diagram showing a specific example of the pattern arrangement of the cooling pipes 58 corresponding to FIG.

Explanation of symbols

  12 Static magnetic field generator, 14 Gradient magnetic field coil, 16 High frequency magnetic field coil, 15 bed, 55 Uniform magnetic field area, 56 Shim tray, 57 Reflection cooling plate, 58 Cooling pipe, 59 Powder, 60 Shim iron hole, 61 slit, 70 plates, 71 black body paint, 73 fins, 94 sandwich plates, 95 holders, 96 side plates, 97 sockets

Claims (9)

A static magnetic field generating means for generating a static magnetic field, a gradient magnetic field coil for generating a gradient magnetic field in the space of the static magnetic field, a shim member for adjusting the uniformity of the static magnetic field and holding the static magnetic field generating means and the and homogeneity adjusting means having a shim tray disposed between the gradient coils, the magnetic resonance imaging apparatus comprising a temperature variation control means for suppressing the temperature fluctuation of the shim member by a liquid body refrigerant, the static magnetic field The generating means includes a static magnetic field generation source that generates the static magnetic field and a magnet container that houses the static magnetic field generation source.
The magnetic resonance imaging apparatus, wherein the temperature fluctuation control means includes a member having a higher thermal conductivity than the magnet container disposed on a surface of the magnet container facing the gradient magnetic field coil. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus, wherein the temperature fluctuation control means includes a reflection cooling member disposed on at least one of the opposing surfaces of the gradient coil and the shim tray. The magnetic resonance imaging apparatus according to claim 1 or 2,
A magnetic resonance imaging apparatus, wherein a member that suppresses thermal radiation is applied to a surface of the gradient magnetic field coil that faces the shim tray. The magnetic resonance imaging apparatus according to any one of claims 1 to 3,
The temperature variation control means includes a first cooling pipe disposed in contact with the reflective cooling member, and includes means for circulating the liquid refrigerant through the first cooling pipe. Magnetic resonance imaging device. The magnetic resonance imaging apparatus according to claim 4.
The temperature fluctuation control means includes a second cooling pipe disposed in the gradient coil, the first cooling pipe and the second cooling pipe are connected, and the liquid refrigerant is the first cooling pipe. A magnetic resonance imaging apparatus, wherein the cooling pipe is flowed first. The magnetic resonance imaging apparatus according to claim 1 .
2. The magnetic resonance imaging apparatus according to claim 1, wherein the temperature fluctuation control means includes a fin disposed on a surface of the magnet container facing the gradient magnetic field coil. The magnetic resonance imaging apparatus according to claim 1 or 6 ,
The temperature variation control means includes a third cooling pipe disposed in contact with the magnet container, and includes a means for circulating the liquid refrigerant through the third cooling pipe. Resonance imaging device. The magnetic resonance imaging apparatus according to any one of claims 1 to 7 ,
The shim tray has a gap inside thereof, and has means for allowing the liquid refrigerant to pass through the gap. The magnetic resonance imaging apparatus according to any one of claims 1 to 7 ,
The magnetic resonance imaging apparatus, wherein the temperature fluctuation control means includes a fourth cooling pipe disposed in the shim tray, and includes means for circulating the liquid refrigerant through the fourth cooling pipe. .

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