JP2011072433A - Magnetic resonance imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MRI apparatus for making a temperature distribution of a magnetic material hold plate 14 even without narrowing an image pickup area and attenuating a fluctuation magnetic field while generating small eddy current. <P>SOLUTION: The MRI apparatus includes: a magnet for generating a static magnetic field in an image pickup area of a subject; a gradient magnetic field coil for making pulse current flow to generate a magnetic field where magnetic field intensity is gradient in the image pickup area, a low temperature area where heat is unevenly generated, and a high temperature area which is higher in temperature than the low temperature area; and a magnetic material hold plate 14 which is disposed along the gradient magnetic field coil, holds a plurality of magnetic materials 13, and improves the evenness of the static magnetic field. The magnetic material hold plate 14 is an excellent conductor provided with slits 19, has a high temperature approximate area 29 close to the high temperature area and low temperature approximate areas 37, 38 close to the low temperature area. The slits 19 are provided so as not to cross between the high temperature approximate area 29 and the low temperature approximate areas 37, 38. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic resonance imaging apparatus (hereinafter referred to as an MRI apparatus) including a magnetic material holding plate that holds a plurality of magnetic materials and improves the uniformity of a static magnetic field in an imaging region.

  An MRI apparatus is an apparatus that obtains a cross-sectional image showing the physical and chemical properties of a subject by utilizing a nuclear magnetic resonance phenomenon that occurs when a subject placed in a uniform static magnetic field is irradiated with a high frequency pulse. In particular, it is used for medical purposes. In the MRI apparatus, the electromagnet device generates a uniform static magnetic field in the imaging region where the subject is inserted, and the magnetic material holding plate holds a plurality of magnetic materials to improve the uniformity of the static magnetic field in the imaging region. The gradient coil generates a gradient magnetic field with a spatially gradient magnetic field in order to give positional information to the imaging region, and the RF coil irradiates the subject with a high-frequency pulse to cause nuclear magnetic resonance. The reception coil receives the magnetic resonance signal from the subject due to the nuclear magnetic resonance phenomenon, and finally, the computer system processes the received magnetic resonance signal and the position information to generate a cross-sectional image. It has gained.

  In order to improve the performance of the MRI apparatus, the strength of the static magnetic field is increased, the strength of the gradient magnetic field is increased, and the pulse drive of the gradient magnetic field is accelerated. The higher the static magnetic field strength, the clearer images and the various cross-sectional images can be obtained. The higher the gradient magnetic field, the higher the image quality and the shorter the imaging time. Increasing the strength and speed of the gradient magnetic field can be achieved by increasing the current of the drive power source for the gradient coil and increasing the switching speed. As a result, high-speed imaging methods have been put into practical use and are actively used in recent years.

  However, when the static magnetic field strength and the gradient magnetic field strength are increased, a pulsed current flows through the gradient magnetic field coil, so that the oscillating electromagnetic force generated between the magnet device and the gradient magnetic field coil also tends to increase. The oscillating electromagnetic force swings the gradient coil and vibrates the magnet device to which the gradient coil is attached. When the magnet device vibrates, it is considered that the uniformity of the static magnetic field is deteriorated and the cross-sectional image is disturbed. In addition, the gradient magnetic field coil through which a large current flows due to the increased strength of the gradient magnetic field easily generates heat, and the temperature of the magnetic material holding plate placed along the gradient magnetic field coil changes, so the temperature of the magnetic material held changes. It is considered that the uniformity of the static magnetic field is deteriorated.

  As a means for reducing the oscillating electromagnetic force, for example, as described in Patent Document 1, it has been proposed to reduce a fluctuating magnetic field due to vibration of a magnet device by causing an eddy current in a low resistivity conductor plate. ing. Further, it has been proposed to remove heat by flowing a coolant such as water in the gradient magnetic field coil with respect to the temperature change of the magnetic material holding plate.

Japanese Patent No. 4037272 (refer to FIG. 2 in particular)

  However, when a conductor plate is placed in a variable magnetic field, a large eddy current is generated in the conductor plate, and the magnetic field resulting from this eddy current is thought to deteriorate the uniformity of the static magnetic field. However, since the fluctuating magnetic field is attenuated by decreasing the eddy current instead of heat, it is preferable to generate the eddy current in a small flow path. In addition, it is considered that forming a system for flowing a refrigerant in the gradient magnetic field coil inevitably narrows the imaging region into which the subject is inserted, and makes the subject feel closed.

  Therefore, it is preferable that the fluctuation magnetic field can be attenuated while generating a small eddy current without narrowing the imaging region by using a system in which a refrigerant flows in the gradient magnetic field coil. The reason for the deterioration of the uniformity of the static magnetic field due to the temperature change of the magnetic material holding plate is that the temperature change in the surface of the magnetic material holding plate is not uniform, and a high and low temperature distribution occurs in the surface of the magnetic material holding plate. It was thought to be because. That is, the first meaning is not to lower the temperature rise of the magnetic material holding plate, but even if the temperature of the magnetic material holding plate rises, the temperature distribution is uniform. It was thought that the flow system could be omitted.

  Therefore, an object of the present invention is to provide an MRI apparatus that can make the temperature distribution of the magnetic material holding plate uniform without narrowing the imaging region, and can attenuate the variable magnetic field while generating a small eddy current.

The present invention relates to a magnet that generates a static magnetic field in an imaging region of a subject, a magnetic field having a magnetic field strength gradient generated in the imaging region by flowing a pulse current, and heat generated non-uniformly to generate a low temperature region and a temperature higher than the low temperature region. In an MRI apparatus comprising a gradient magnetic field coil in which a high temperature region is formed and a magnetic material holding plate arranged along the gradient magnetic field coil to hold a plurality of magnetic materials and improve the uniformity of the static magnetic field,
The magnetic material holding plate is a good conductor having a slit, and has a high temperature proximity region close to the high temperature region and a low temperature proximity region close to the low temperature region,
The slit is provided so as not to cross between the high temperature proximity region and the low temperature proximity region.

  ADVANTAGE OF THE INVENTION According to this invention, the temperature distribution of a magnetic material holding plate can be made uniform, without narrowing an imaging area | region, and the MRI apparatus which can attenuate a variable magnetic field can be provided, generating a small eddy current.

1 is a perspective view of a magnetic resonance imaging (MRI) apparatus according to a first embodiment of the present invention. 1 is a longitudinal sectional view of an MRI apparatus according to a first embodiment of the present invention. It is a disassembled perspective view of a gradient magnetic field coil. It is a top view of a gradient magnetic field coil, and is the figure which showed the generation | occurrence | production condition of the high temperature area | region and the low temperature area | region. It is a top view of a magnetic material holding | maintenance board, and is a figure which showed the generation | occurrence | production condition of the high temperature proximity | contact area | region, the low temperature proximity | contact area | region, and eddy current. It is arrow sectional drawing of the AA direction of FIG. 5A. It is a longitudinal cross-sectional view of the magnetic resonance imaging apparatus which concerns on the 1st Embodiment of this invention, and is a figure for demonstrating the generation | occurrence | production cause of an oscillating magnetic field. FIG. 3 is an intensity distribution diagram of a static magnetic field in an imaging region of the MRI apparatus according to the first embodiment of the present invention. It is an intensity distribution diagram of a static magnetic field in an imaging region of a conventional MRI apparatus. It is a graph of the uniformity of the static magnetic field in the imaging area | region of an MRI apparatus with respect to the vibration frequency of a gradient magnetic field coil. It is a top view of the magnetic material holding plate of the MRI apparatus which concerns on the 2nd Embodiment of this invention, and is the figure which showed the generation | occurrence | production condition of the high temperature proximity | contact area | region, the low temperature proximity | contact area | region, and an eddy current.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

(First embodiment)
FIG. 1 shows a perspective view of a magnetic resonance imaging (MRI) apparatus 21 according to the first embodiment of the present invention. According to the MRI apparatus 21, the subject 7 is physically placed on the subject 7 by using the nuclear magnetic resonance phenomenon that occurs when the subject 7 is placed in the imaging region 9 having a uniform static magnetic field and irradiated with a high frequency pulse. A cross-sectional image showing chemical properties can be obtained.

  The MRI apparatus 21 includes an electromagnet apparatus 22, and the electromagnet apparatus 22 generates a uniform static magnetic field in the imaging region 9. The electromagnet device 22 has a pair of upper and lower static magnetic field generators provided with a pair of upper and lower vacuum containers 1 on the outside, and a connecting column 12 that supports the pair of upper and lower vacuum containers 1 so as to be separated from each other. The subject 7 is inserted between the pair of upper and lower vacuum containers 1 while lying on the bed 23, and the imaging region of the subject 7 can be placed in the imaging region 9. Further, an RF coil 11 is provided on the imaging region 9 side of the vacuum vessel 1.

  The pair of upper and lower vacuum containers 1 have a disk shape that is generally rotationally symmetric with respect to a common central axis (z axis), and sandwiches the imaging region 9. The direction 6 of the static magnetic field is parallel to the z axis. In order to facilitate understanding of the structure of the MRI apparatus 21, xyz coordinates are set, and a coordinate origin is set in the middle of the pair of upper and lower vacuum vessels 1 on the z axis (center of the imaging region 9). is doing. The x-axis is set along the direction from the coordinate origin to the connecting column 12, and the y-axis is set along the insertion direction of the bed 23 perpendicular to the x-axis.

  FIG. 2 shows a longitudinal sectional view of the MRI apparatus 21 according to the first embodiment of the present invention. In the MRI apparatus 21, the magnetic material holding plate (shim tray) 14 improves the uniformity of the static magnetic field in the imaging region 9, and the gradient magnetic field coil 5 spatially applies a magnetic field to give positional information to the imaging region 9. A gradient magnetic field 10 having a gradient in intensity is generated in a pulse shape, the RF coil 11 irradiates the subject 7 with a high frequency pulse to cause a nuclear magnetic resonance phenomenon, and a receiving coil (not shown) causes the nuclear magnetic resonance phenomenon to occur. The resulting magnetic resonance signal from the subject 7 is received, and finally a computer system (not shown) processes the received magnetic resonance signal and the position information to obtain a cross-sectional image.

  The gradient magnetic field coil 5 has a pair of upper and lower sides, and is disposed on the imaging region 9 side of the vacuum vessel 1. The gradient magnetic field coil 5 generates, in a pulsed manner, a gradient magnetic field 10 in which the magnetic flux density (magnetic field strength) in the same direction as the static magnetic field direction 6 is inclined in an arbitrary direction in the imaging region 9. In general, the gradient magnetic field 10 can be generated not only in the y-axis direction shown in FIG. 2 but also in the function of generating independent gradient magnetic fields 10 in the three directions of the x-axis direction and the z-axis direction. The gradient magnetic field coil 5 is supported by the vacuum vessel 1 through support legs 15.

  The magnetic material holding plates (shim trays) 14 are a pair of upper and lower, and are arranged between the vacuum vessel 1 and the gradient magnetic field coil 5 along the vacuum vessel 1 and the gradient magnetic field coil 5 on the imaging region 9 side of the vacuum vessel 1. Has been. By arranging a plurality of small pieces of magnetic material (shim) 13 (see FIG. 5B) on the magnetic material holding plate (shim tray) 14, the uniformity of the static magnetic field strength in the imaging region 9 can be adjusted and improved. . The RF coil 11 has a pair of upper and lower sides and is disposed on the imaging region 9 side of the gradient magnetic field coil 5.

  In the vacuum vessel 1, an annular superconducting coil (main coil) 3, a superconducting coil (shield coil) 4, and a magnetic body (not shown) are arranged coaxially with the z axis as the central axis. Superconducting coils 3 and 4 are housed in a cooling container 8 filled with radiation shield 2 and liquid helium (He) as a refrigerant. The cooling container 8 is supported by the vacuum container 1 via the support legs 25.

  FIG. 3 shows an exploded perspective view of the upper gradient magnetic field coil 5 in the pair. The lower gradient coil 5 has a symmetrical structure of the upper gradient coil 5. The gradient magnetic field coil 5 has main coils 31 to 33 and shield coils 34 to 36. The main coil 31 has two spiral centers 30 arranged in the x-axis direction, and generates a gradient magnetic field whose magnetic field strength is inclined in the x-axis direction in the imaging region 9. The main coil 32 has two spiral centers 30 arranged in the y-axis direction, and generates a gradient magnetic field whose magnetic field strength is inclined in the y-axis direction in the imaging region 9. The main coil 33 has one spiral center 30 in the center, and generates a gradient magnetic field in the imaging region 9 whose magnetic field strength is inclined in the z-axis direction. The shield coil 34 has one spiral center 30 in the center, and cancels the magnetic field generated by the main coil 33 outside the imaging region 9. The shield coil 35 has two spiral centers 30 arranged in the x-axis direction, and cancels the magnetic field generated by the main coil 31 outside the imaging region 9. The shield coil 36 has two spiral centers 30 arranged in the y-axis direction, and cancels the magnetic field generated by the main coil 32 outside the imaging region 9.

  The main coils 31 to 33 and the shield coils 34 to 36 are energized to generate a gradient magnetic field, and generate heat and increase their temperature. Since the temperature rise occurs at a place where heat generated by heat generation is difficult to dissipate, for example, in the main coils 31 and 32 and the shield coils 35 and 36, it is considered that the temperature rises in an area around the spiral center 30. It is done. And it is thought that the temperature does not increase as the distance from the region increases, and is maintained at a low temperature. Further, in the main coil 33 and the shield coil 34, the influence of the winding density is taken into consideration, and it is considered that the temperature rises in a wide peripheral region centering on the spiral center 30. And it is thought that an outer peripheral area | region is maintained at low temperature.

  FIG. 4 shows a plan view of the gradient coil 5. On the surface of the gradient magnetic field coil 4, four high temperature regions 26 are generated by the main coils 31 to 33 and the shield coils 34 to 36. The closed loop arrow shown in FIG. 4 schematically shows the current flowing through the main coil 32 (see FIG. 3) and the shield coil 36, and the center of the closed loop arrow is the spiral center 30. A high temperature region 26 is generated around the spiral center 30. Two high temperature regions 26 occur on the y axis. A total of three low temperature regions 27 are generated before and after the two high temperature regions 26 on the y axis.

  Similarly, two high temperature regions 26 are generated on the x-axis by the main coil 31 (see FIG. 3) and the shield coil 35. A total of three low temperature regions 27 are generated before and after the two high temperature regions 26 on the x-axis. The main coil 33 (see FIG. 3) and the shield coil 34 function to further increase the four high temperature regions 26.

  Then, in the regions farthest from the four high temperature regions 26, low temperature regions 28 having a temperature lower than that of the low temperature region 27 as well as the high temperature region 26 are generated in four locations.

  FIG. 5A shows a plan view of the magnetic material holding plate 14, and FIG. 5B shows a cross-sectional view taken along the line AA in FIG. 5A. The magnetic material holding plate 14 is a good conductor and preferably includes at least one of aluminum (Al), copper (Cu), gold (Au), silver (Ag), and a superconducting material. If it is a good conductor, the electric resistance in the surface direction of the magnetic material holding plate 14 can be reduced, and heat conduction can be improved. A plurality of insertion holes 20 are provided in the magnetic material holding plate 14. By appropriately fitting and holding a plurality of magnetic materials 13 in the fitting holes 20, the uniformity of the static magnetic field in the imaging region 9 is improved.

  Since the magnetic material holding plate 14 is disposed close to the gradient magnetic field coil 5 (see FIG. 2), a temperature distribution is generated by heat conduction such as radiant heat from the gradient magnetic field coil 5. Comparing FIG. 5A and FIG. 4, a high temperature proximity region 29 having a high temperature is generated in a region close to the high temperature region 26. Further, a low temperature proximity region 37 that maintains a low temperature is generated in a region close to the low temperature region 27. A low temperature proximity region 38 that maintains a low temperature is generated in a region close to the low temperature region 28. The low temperature proximity region 38 is maintained at a lower temperature than the low temperature proximity region 37.

  The magnetic material holding plate 14 is provided with a plurality of slits 19. The slits 19 are provided radially in the radial direction of the disk-shaped magnetic material holding plate 14. The slits 19 are provided in line symmetry with the x axis as the symmetry axis, and are provided in line symmetry with the y axis as the symmetry axis. The slit 19 substantially divides the high temperature proximity region 29 and the low temperature proximity region 37. The slits 19 (19 a) arranged on the x-axis or the y-axis are provided along the direction from the high temperature proximity region 29 to the low temperature proximity region 37. The slits 19 (19b) disposed at an inclination of 45 degrees from the x-axis and the y-axis substantially divide the low temperature proximity region 38. Thus, since the slit 19 is provided so as not to cross between the high temperature proximity region 29 and the low temperature proximity region 37, 38, the heat of the high temperature proximity region 29 passes through the magnetic material holding plate 14 which is a good conductor along the shortest path. Conducting can raise the temperature of the low temperature proximity regions 37 and 38 and make the temperature distribution in the surface of the magnetic material holding plate 14 uniform. Variations in the temperature of the plurality of magnetic members 13 fitted therein are also reduced, and the uniformity of the static magnetic field in the imaging region 9 can be maintained with high accuracy.

  Further, the plurality of slits 19 block a flow path of eddy current generated by an oscillating magnetic field, which will be described later, and generate only a small eddy current 18. The eddy current 18 is generated symmetrically with respect to the x-axis and the y-axis and flows so as to be symmetric. Due to this symmetry, generation of a magnetic field that disturbs the cross-sectional image can be suppressed. In FIG. 5A, the eddy current 18 at the generation timing of the eddy current 18 that is symmetric with respect to the x-axis is shown in consideration of the flow direction of the eddy current 18. At timings before and after this timing, the eddy current 18 generates a flow in a direction symmetric with respect to the y-axis.

  In FIG. 5A, the magnetic material holding plate 14 is not divided by the slits 19 and the magnetic material holding plate 14 has an integrated disk shape, but each slit 19 is extended in the length direction. For example, it may be divided into two equal parts, fourth equal parts, or eighth equal parts. In this case, portability and workability at the time of attachment can be improved.

  FIG. 6 shows how the MRI apparatus 21 is oscillated by an oscillating magnetic field. Since the actual vibration amplitude is small and not visible, the amplitude is drawn larger than the actual amplitude for easy understanding. Here, the variable magnetic field generated with the vibration of the electromagnet device 22 will be described with reference to FIG. When a pulse current is applied to the gradient magnetic field coil 5, Lorentz force is generated in the static magnetic field generated by the electromagnet device 22, and the gradient magnetic field coil 5 vibrates. Since the gradient coil 5 is supported by the support leg 15 on the vacuum vessel 1 of the electromagnet device 22, the vibration propagates through the support leg 15 and vibrates the vacuum vessel 1. Further, the vibration propagates to the superconducting coils 3 and 4 and the magnetic body (not shown) in the vacuum vessel 1 through the support legs 25 and the like.

  When the superconducting coils 3 and 4 that generate a static magnetic field and the magnetic body vibrate, an oscillating magnetic field 16 in which the uniformity of the static magnetic field is disturbed is generated. At the same time, an eddy current 17 is generated in the metal structure such as the vacuum vessel 1 by the oscillating magnetic field 16 that varies with time. This eddy current 17 is generated both when the superconducting coils 3 and 4 and the magnetic body vibrate or when a metal structure such as the vacuum vessel 1 vibrates.

  Since the magnetic material holding plate 14 is also a good conductor, an eddy current 18 is generated as in the vacuum vessel 1, and the magnetic material holding plate 14 is close to the imaging region 9, so that the magnetic field due to the eddy current 18 becomes the oscillating magnetic field 16. Affects the image.

  For this reason, as shown in FIG. 5A, in the first embodiment, the magnetic material holding plate 14 is used as a good conductor, and a slit 19 is provided to prevent the flow path of the eddy current 18 while generating the eddy current 18 by vibration. . Thereby, the eddy current 18 due to vibration is reduced, the deterioration of the uniformity of the static magnetic field due to the eddy current magnetic field can be suppressed, and the magnetic material holding plate 14 and further the magnetic material 13 can be obtained by making a good conductor with good heat conduction. Therefore, a clear image can be obtained.

  FIG. 7A shows an intensity distribution diagram of the static magnetic field in the imaging region 9 of the MRI apparatus 21 according to the first embodiment (with slits) of the present invention, and FIG. 7B shows imaging of the MRI apparatus of the prior art (without slits). The intensity distribution map of the static magnetic field in the region 9 is shown. These are the cases where the gradient magnetic field coil 5 is analyzed by numerical simulation when it vibrates at the vibration frequency f1. The vibration frequency f1 corresponds to the resonance frequency of the gradient coil 5, and the vibration amplitude tends to increase at the vibration frequency f1. Thus, in the prior art, the magnetic field strength fluctuates (disturbs) in the range of ± 3α with respect to the average magnetic field strength AVE, whereas in the present invention, since eddy current can be reduced, the average magnetic field strength AVE Disturbances can be reduced simply by changing the magnetic field strength within a range of ± 1α. FIG. 7C shows the relationship of the uniformity of the static magnetic field in the imaging region 9 with respect to the vibration frequency of the gradient coil 5 by numerical simulation. According to the MRI apparatus 21 of the present invention, including the vibration frequency f1 (resonance frequency), the disturbance is smaller than that of the prior art and the uniformity can be improved.

(Second Embodiment)
FIG. 8 is a plan view of the magnetic material holding plate 14 of the MRI apparatus according to the second embodiment of the present invention. The MRI apparatus of the second embodiment is different from the MRI apparatus 21 of the first embodiment in the arrangement of the slits 19. On the other hand, the high temperature proximity region 29 and the low temperature proximity regions 37 and 38 are generated as in the first embodiment. Similarly to the first embodiment, the slits 19 (19a) are arranged in the radial direction of the magnetic material holding plate 14 on the x-axis and the y-axis.

  The difference in the arrangement of the slits 19 is that the slits 19 c are provided in a direction perpendicular to the radial direction of the magnetic material holding plate 14 and cross the slits 19 a in the high temperature proximity region 29. The slit 19 c is provided along the direction from the high temperature proximity region 29 to the low temperature proximity region 38. The slits 19 d and 19 e are also provided in a direction orthogonal to the radial direction of the magnetic material holding plate 14, and are provided in parallel with the direction from the high temperature proximity region 29 to the low temperature proximity region 38. The path of heat conduction from the high temperature proximity region 29 to the low temperature proximity region 38 is considered as the main path, and the slit 19 (19a, 19c, 19d, 19e) crosses between the high temperature proximity region 29 and the low temperature proximity region 38. The shortest path for heat conduction is secured. For this reason, the heat generated in the high temperature proximity region 29 is conducted to the low temperature proximity region 38 to lower the temperature of the high temperature proximity region 29 and increase the temperature of the low temperature proximity region 38, thereby increasing the temperature in the surface of the magnetic material holding plate 14. It can be made uniform.

  Further, the plurality of slits 19 (19a, 19c, 19d, 19e) further block the eddy current flow path from the first embodiment, and the eddy current 18 (18a) smaller than the eddy current 18 of the first embodiment. , 18b, 18c), and the eddy current 18 is further reduced. The eddy currents 18a, 18b, and 18c are generated symmetrically with respect to the x-axis and the y-axis, and flow so as to be symmetric. Due to this symmetry, generation of a magnetic field that disturbs the cross-sectional image can be suppressed.

1 Vacuum container (static magnetic field generator)
3 Superconducting coil (main coil)
4 Superconducting coil (shield coil)
5 Gradient magnetic field coil 9 Imaging area 13 Magnetic material (shim)
14 Magnetic material holding plate (Shim tray)
DESCRIPTION OF SYMBOLS 15 Support leg of gradient magnetic field coil 16 Oscillating magnetic field 17 Eddy current which flows into vacuum container by vibration 18, 18a, 18b, 18c Eddy current generated in magnetic material holding plate by vibration 19, 19a, 19b, 19c, 19d, 19e Slit 20 Insertion hole 21 Magnetic resonance imaging apparatus (MRI apparatus)
22 Electromagnet device (magnet)
26 High temperature region 27, 28 Low temperature region 29 High temperature proximity region 37, 38 Low temperature proximity region

Claims (9)

A magnet that generates a static magnetic field in the imaging region of the subject, and a pulsed current that generates a magnetic field with a gradient in magnetic field intensity, and generates heat unevenly, resulting in a low temperature region and a high temperature region that is higher than the low temperature region. In a magnetic resonance imaging apparatus comprising a gradient magnetic field coil, and a magnetic material holding plate arranged along the gradient magnetic field coil to hold a plurality of magnetic materials and improve the uniformity of the static magnetic field,
The magnetic material holding plate is a good conductor having a slit, and has a high temperature proximity region close to the high temperature region and a low temperature proximity region close to the low temperature region,
The magnetic resonance imaging apparatus, wherein the slit is provided so as not to cross between the high temperature proximity region and the low temperature proximity region.   The magnetic resonance imaging apparatus according to claim 1, wherein the slit divides at least one of the high temperature proximity region and the low temperature proximity region.   The plurality of slits are arranged at positions symmetrical to each other with respect to an axis of symmetry parallel to the direction of the gradient of the magnetic field generated by the gradient coil. Magnetic resonance imaging equipment.   4. The magnetic material holding plate includes at least one of aluminum (Al), copper (Cu), gold (Au), silver (Ag), and a superconducting material. The magnetic resonance imaging apparatus according to any one of the above. The magnet has two static magnetic field generation units sandwiching the imaging region,
The said magnetic material holding plate is provided in the said imaging region side of the said static magnetic field generation | occurrence | production part, and is a disk shape or a disc shape which can be divided | segmented, The any one of Claims 1 thru | or 4 characterized by the above-mentioned. Magnetic resonance imaging equipment.   The magnetic resonance imaging apparatus according to claim 5, wherein the slit is provided in a radial direction of the disk.   The magnetic resonance imaging apparatus according to claim 5, wherein the slit is provided in a direction orthogonal to a radial direction of the disk.   The magnetic resonance imaging apparatus according to claim 1, wherein the slit is provided along a direction from the high temperature proximity region to the low temperature proximity region.   The magnetic resonance imaging apparatus according to claim 1, wherein the slit crosses in the high temperature proximity region.

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