JP5179827B2 - Magnetic resonance equipment - Google Patents

Description

  The present invention relates to a magnetic resonance apparatus in which a magnetic metal is accommodated in an accommodating portion for correcting the uniformity of a main magnetic field.

  The magnetic resonance apparatus includes a magnet (permanent magnet or electromagnet) for generating a main magnetic field and a gradient magnetic field system (gradient magnetic field coil) for generating a gradient magnetic field. The main magnetic field is a static magnetic field and desirably has high uniformity. Therefore, shimming is performed in order to maintain the uniformity of the main magnetic field. Shimming is roughly divided into passive shimming and active shimming. Passive shimming adjusts the magnetic field distribution of the main magnetic field by placing a magnetic metal (such as an iron piece) called a shim near the magnet. More specifically, the uniformity of the main magnetic field is maintained by devising the arrangement of a plurality of magnetic metals. Active shimming generates a correction magnetic field for making a main magnetic field uniform by adjusting a current flowing through a coil (shim coil).

  Now, in passive shimming, it is known that non-uniformity of the main magnetic field occurs due to fluctuations in the temperature of the magnetic metal. In addition, it is known that an offset occurs in the main magnetic field due to fluctuations in the temperature of the magnetic metal. The cause of the temperature fluctuation includes mainly heat generation from the gradient magnetic field coil and heat generation in the magnetic metal due to eddy current induced by the generation of the gradient magnetic field. When the temperature of the magnetic metal changes due to these heat generations, the magnetic susceptibility of the magnetic metal changes, and as a result, the strength of the main magnetic field changes partially or entirely.

A technique of including a correction magnetic field for correcting such inhomogeneity of the main magnetic field in a gradient magnetic field is known (see, for example, Patent Document 1). In this technique, the temperature of the magnet is detected, and the correction amount is determined according to the temperature. Then, the offset of the current value corresponding to the correction amount is supplied to the gradient magnetic field coil in addition to the current for generating the gradient magnetic field that is originally required.
JP-A-2-206436

  In the above conventional technique, since the main magnetic field is corrected by the gradient magnetic field, the correction amount and the correction resolution are limited, and the uniformity and strength of the main magnetic field cannot always be kept constant.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a magnetic resonance apparatus capable of maintaining a main magnetic field stably by effectively functioning passive shimming. It is in.

The magnetic resonance apparatus according to one aspect of the present invention is the magnetic resonance apparatus in which the magnetic metal is accommodated in the accommodating portion for correcting the uniformity of the main magnetic field, the temperature of the magnetic metal accommodated in the accommodating portion, and the accommodating portion. An acquisition means for acquiring temperature information related to any of the temperature of the storage section and a temperature in the vicinity of the storage section, a temperature change section for changing the temperature of the magnetic metal stored in the storage section, and the storage section When the magnetic metal is placed, the temperature of the magnetic metal is adjusted to a target temperature set higher than normal temperature based on the temperature information acquired by the acquisition means , and at the time of imaging, the acquisition means Control means for controlling the temperature changing means so as to adjust the temperature of the magnetic metal to the target temperature based on the acquired temperature information .

  According to the present invention, it is possible to effectively maintain the uniformity of the main magnetic field by effectively functioning passive shimming.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view of a part of a magnetic resonance imaging (MRI) apparatus 100 according to an embodiment of the present invention.

  The MRI apparatus 100 in this embodiment includes a gantry 10, a magnet 11, a gradient magnetic field coil unit 12, a gradient magnetic field power source 22, a high frequency coil (RF coil) 23, a transmitter 24, a receiver 25, a sequencer 26, a system controller 27, and an input. Device 28, arithmetic unit 29, storage unit 30, display 31, heater control unit 32, and flow rate control unit 33. Furthermore, the MRI apparatus 100 includes a bed that is disposed adjacent to the gantry 10 but not shown. The gantry 10 is typically formed with a photographing space 10a penetrating in a substantially cylindrical shape at the inner center portion thereof. The axial direction of the imaging space 10a is defined as a Z direction, and two directions that are orthogonal to the Z direction and are also orthogonal to each other are defined as an X direction (horizontal direction) and a Y direction (vertical direction). In FIG. 1, the gantry 10 shows only a half broken at the YZ plane.

The gantry 10 accommodates a magnet 11 and a gradient magnetic field coil unit 12. The magnet 11 generates a main magnetic field (static magnetic field) B ₀ in the imaging space 10a. As the magnet 11, a superconducting magnet is typically used. The overall shape of the magnet 11 is formed in a substantially cylindrical shape. Inside the magnet 11, a magnet bore (hereinafter simply referred to as a bore) 11a is formed. The axis of the bore 11a coincides with the axis of the imaging space 10a. The gradient coil unit 12 is disposed in the bore 11a. The gradient coil unit 12 is individually supplied with drive currents corresponding to the X, Y, and Z axes from the gradient magnetic field power source 22 to individually generate gradient magnetic fields for the X, Y, and Z axes. Includes three sets of coils.

  The RF coil 23 is disposed inside the imaging space 10a during imaging. A transmitter 24 and a receiver 25 are connected to the RF coil 23. The transmitter 24 supplies a pulse current that oscillates at the Larmor frequency to the RF coil 23 under the control of the sequencer 26. The receiver 25 receives a magnetic resonance (MR) signal via the RF coil 23 and performs various signal processing to form a corresponding digital signal. The couch top 34 is arranged so as to be able to be inserted into and removed from the imaging space 10a of the gantry 10, and the subject 200 is placed on the upper surface thereof.

  The sequencer 26 is placed under the control of a system controller 27 that manages the entire MRI apparatus 100. An input device 28 is connected to the system controller 27. The operator can select a desired pulse sequence from a plurality of types of pulse sequences such as a spin echo (SE) method and an echo planer (EPI) method via the input device 28. The system controller 27 sets the selected pulse sequence in the sequencer 26. The sequencer 26 controls the application timing and intensity of each gradient magnetic field in the X, Y, and Z axis directions, the application timing of the high-frequency magnetic field, the amplitude, the duration, and the like according to the set pulse sequence.

  The arithmetic unit 29 inputs the MR signal (digital data) formed by the receiver 25, arranges the measured data in a two-dimensional Fourier space formed by a built-in memory, Fourier transform for image reconstruction, etc. To generate image data and spectrum data. The storage unit 30 stores the calculated image data. The display 31 displays an image.

  The heater control unit 32 controls the amount of heat generated by a heater (described later) built in the gradient magnetic field coil unit 12. The flow rate control unit 33 controls the flow rate of the coolant flowing through a cooling pipe (described later) built in the gradient magnetic field coil unit 12. The cooling liquid is cooled by a cooling device (not shown). Based on the temperature measured by a sensor (described later) built in the gradient coil unit 12, the system controller 27 sets the heater controller 32 so that the temperature of the magnetic metal built in the gradient coil unit 12 becomes the target temperature. And a function of controlling the flow rate control unit 33.

  FIG. 2 is a perspective view showing a schematic configuration of the gradient coil unit 12.

  As shown in FIG. 2, the gradient coil unit 12 includes a plurality of pockets 13, and includes a plurality of cooling pipes 14, a plurality of heaters 15, and sensors 16.

  The pocket 13 has a through-hole shape along the axial center of the gradient coil unit 12, and a magnetic metal is disposed therein as necessary. In FIG. 2, four pockets 13 are shown. The number of pockets 13 may be arbitrary, and it is preferable that there are many physical limitations. This is because the degree of freedom of arrangement of the magnetic metal is increased, and the accuracy of correction of the magnetic field uniformity can be improved. The number of the preferable pockets 13 is, for example, 12 or 24. The cooling pipe 14 is arranged in parallel with the pocket 13 at a position adjacent to the inner peripheral side of the gradient coil unit 12 with respect to each of the pockets 13. The cooling pipe 14 serves as a coolant flow path for cooling the magnetic metal disposed in the pocket 13. The flow rate of the coolant in the cooling pipe 14 is controlled by the flow rate control unit 33. The heater 15 is arranged in parallel with the pocket 13 at a position adjacent to the outer peripheral side of the gradient coil unit 12 with respect to each of the pockets 13. The heater 15 heats the magnetic metal disposed in the pocket 13. The heating temperature of the heater 15 is controlled by the heater control unit 32. The sensor 16 is disposed in the vicinity of one of the pockets 13. The sensor 16 measures the temperature of the magnetic metal disposed in the pocket 13. The sensor 16 sends a signal representing the measured temperature to the system controller 27. As the sensor 16, a semiconductor sensor, a thermocouple, or the like can be used.

  FIG. 3 is a cross-sectional view of the gradient coil unit 12 in the XY plane.

  As shown in FIG. 3, the gradient coil unit 12 is divided into a main coil layer 12a, a shim layer 12b, and a shield coil layer 12c from the inner peripheral side. And the pocket 13, the cooling pipe 14, and the heater 15 are all provided in the shim layer 12b. The shim layer 12b is formed by molding the pocket 13, the cooling pipe 14, and the heater 15 into a cylindrical shape with resin. The main coil layer 12a is supplied with a current from the gradient magnetic field power source 22, and generates three types of main coils (X-main coil, X, Y, Z) that generate gradient magnetic fields whose magnetic field strengths change along the X, Y, and Z axes, respectively. Y-main coil, Z-main coil) are molded into a cylindrical shape with resin. The shield coil layer 12c is supplied with a current from the gradient magnetic field power source 22, and generates three types of shield coils (X-shield coil, Y-shield) for generating a magnetic field for shielding a leakage magnetic field from the main coil layer 12a. Coil, Z-shield coil) is molded into a cylindrical shape with resin. That is, the gradient coil unit 12 is a so-called ASGC (actively shielded gradient coil).

  In FIG. 3, the main coil layer 12a and the shield coil layer 12c show only their cross-sectional outlines, and the detailed internal structure is not shown.

  Next, the operation of the MRI apparatus 100 configured as described above will be described.

  At the time of imaging, the magnet 11 generates a main magnetic field in the imaging space 10a. This main magnetic field is usually required to have a strength of several kilogauss to several tens of kilogauss (several tesla). In addition to strength, the main magnetic field is required to have spatial uniformity. A spatial region where a uniform magnetic field is required is generally a spherical region having a diameter of about 50 cm. Spatial uniformity is usually required to be several tens of ppm or less over the entire spatial region when the main magnetic field strength is 1.5 Tesla.

  The magnet 11 is manufactured so as to generate a magnetic field that satisfies the above requirements. However, the magnetic field generated by the magnet 11 is distorted due to the influence of the surrounding magnetic material. Therefore, for example, as part of the installation work or maintenance work of the MRI apparatus 100, a magnetic metal is appropriately placed in the pocket 13 by the operator so that the non-uniformity of the main magnetic field is corrected. That is, by disposing the magnetic metal in the pocket 13, the magnetic field distribution of the main magnetic field changes due to the influence. Therefore, the nonuniformity of the main magnetic field can be corrected by appropriately arranging the magnetic metal so that the change in the magnetic field distribution works to correct the nonuniformity of the main magnetic field.

  However, the magnetic susceptibility of magnetic metals varies with temperature. When the magnetic susceptibility of the magnetic metal disposed in the pocket 13 changes, the influence of the magnetic metal on the main magnetic field changes, and the nonuniformity of the main magnetic field also decreases. Therefore, in order to suppress the reduction in non-uniformity of the main magnetic field that occurs in this way, the system controller 27 performs the following temperature control.

(basic action)
When the heat generated from the gradient coil 12 is transferred to the magnetic metal in the pocket 13 so that the magnetic metal becomes higher than a predetermined temperature, or when the magnetic metal becomes lower than the predetermined temperature in the standby state. The temperature of the magnetic metal measured by the sensor 16 is sent to the system controller 27. When it is necessary to increase the temperature of the magnetic metal based on the measurement result, the system controller 27 instructs the heater control unit 32 to operate the heater 15 to increase the temperature of the magnetic metal to a predetermined temperature. . On the contrary, when it is necessary to lower the temperature of the magnetic metal, the flow controller 33 is instructed to increase the flow rate of the coolant in the cooling pipe 14 to lower the magnetic metal to a predetermined temperature. The heater control unit 32 and the flow rate control unit 33 perform control so as to keep the temperature of the magnetic metal at a constant temperature based on a command from the system controller 27. As a result, the temperature of the magnetic metal is always kept substantially constant, so that the change in magnetic susceptibility due to the temperature change of the magnetic metal is reduced. Therefore, the uniformity of the main magnetic field can be maintained.

  Below, temperature control is demonstrated more concretely.

(When placing magnetic metal)
When the work of placing the magnetic metal in the pocket 13 is performed, the system controller 27 recognizes that fact based on, for example, an instruction from the operator. In this case, the system controller 27 controls the heater control unit 32 and the flow rate control unit 33 so that the temperature of the magnetic metal measured by the sensor 16 becomes a predetermined target temperature. Here, the target temperature is set higher than the normal temperature. The target temperature is set lower than the temperature at which the resin located around the magnetic metal is denatured. The range of the target temperature that satisfies such conditions is usually about 40 to 80 ° C.

  Now, at the time of the above-mentioned work, usually no great heat is generated in the gantry 10. For this reason, the temperature of the magnetic metal arranged in the pocket 13 is often about room temperature. That is, the temperature of the magnetic metal is often lower than the target temperature. Therefore, in such a state, the system controller 27 controls the heat generation amount of the heater 15 via the heater control unit 32 so that the temperature of the magnetic metal disposed in the pocket 13 is raised to the target temperature. If for some reason the temperature of the magnetic metal exceeds the target temperature, or if the temperature of the magnetic metal exceeds the target temperature as a result of heating by the heater 15, the system controller 27 is placed in the pocket 13. The flow rate of the coolant in the cooling pipe 14 is controlled via the flow rate control unit 33 so that the temperature of the magnetic metal being lowered to the target temperature.

  The operation of arranging the magnetic metal in the pocket 13 in this way is performed in an environment where the temperature of the magnetic metal becomes the target temperature. That is, the magnetic metal is arranged so that the uniformity of the main magnetic field is high when the temperature of the magnetic metal is the target temperature.

(When shooting)
At the time of photographing, energization to the main coil and shield coil of the gradient magnetic field coil unit 12 is switched at high speed. As a result, the main coil and the shield coil generate heat, and the heat generation heats the magnetic metal. The magnetic metal is also heated by an eddy current generated in the magnetic metal by a magnetic field. Therefore, the system controller 27 increases the cooling capacity by the cooling liquid in accordance with the temperature rise of the magnetic metal based on the measurement result by the sensor 16, and cools the cooling pipe 14 so that the temperature of the magnetic metal is maintained at the target temperature. The flow rate of the liquid is controlled via the flow rate control unit 33.

  In addition, when it has been in a standby state for a long time, the temperature of the magnetic metal may be about room temperature. In this case, the system controller 27 controls the heat generation amount of the heater 15 via the heater control unit 32 so as to raise the temperature of the magnetic metal to the target temperature. When heating the magnetic metal in this way, shooting may be started before the temperature of the magnetic metal rises to the target temperature, or the shooting is started after the temperature of the magnetic metal rises to the target temperature. You may do it. In the former case, the photographing time can be shortened. In the latter case, high-quality imaging can be performed with little influence of fluctuations in the main magnetic field.

  If the imaging start time is determined in advance, the system controller 27 may control the heater 15 via the heater control unit 32 so that the temperature of the magnetic metal is raised to the target temperature before the imaging start time. good. In this way, it is possible to perform high-quality image capturing with little influence of fluctuations in the main magnetic field and shorten the image capturing time. Of course, the flow rate of the coolant and the amount of heat generated by the heater 15 may be controlled by the system controller 27 so that the temperature of the magnetic metal becomes the target temperature even in the standby state.

  As described above, according to the MRI apparatus 100, since the temperature of the magnetic metal is kept substantially constant at the target temperature at the time of imaging, the change in the uniformity of the main magnetic field due to the temperature change of the magnetic metal hardly occurs during imaging. Absent. As a result, it is possible to perform shooting in a stable main magnetic field and obtain a high-quality image.

  Further, since the MRI apparatus 100 maintains the temperature of the magnetic metal disposed in the pocket 13 at the target temperature at the time of the magnetic metal placement work, if the magnetic metal placement is appropriately performed during this work, It is possible to maintain a high uniformity of the main magnetic field during imaging. As a result, it is possible to obtain a high-quality image with small spatial image quality variation.

  By the way, cooling of the gradient magnetic field coil unit or the like has been conventionally performed. Conventionally, it has been desirable for such cooling to lower the temperature of the object to be cooled as much as possible, and thus a large cooling capacity has been required. However, the MRI apparatus 100 maintains the temperature of the magnetic metal at a certain level by setting the target temperature to a temperature higher than normal temperature. Therefore, the MRI apparatus 100 only needs to have a cooling capacity smaller than that required based on the conventional common sense described above. However, in the MRI apparatus 100, the target temperature is set lower than the temperature at which the resin or the like located around the magnetic metal is denatured. There is no end.

  This embodiment can be variously modified as follows.

  (1) The sensor 16 may be disposed anywhere as long as the temperature related to the temperature of the magnetic metal can be measured. Of course, it is sufficient if it is in the vicinity of the magnetic metal. For example, when the temperature change of the magnetic metal has a correlation (for example, when the temperature change of the magnetic metal is doubled, 1. Any position is acceptable as long as the temperature changes by a factor of five. In this case, a correlation coefficient between the sensor 16 and the temperature of the magnetic metal is given to the system controller 27 in advance, and the temperature of the magnetic metal is determined based on the correlation coefficient and the temperature measured by the sensor 16. It can be determined by the controller 27.

  (2) In the above embodiment, the MRI apparatus 100 is provided with the cooling pipe 14 and the heater 15. However, one cooling means and one heating means may be provided. In this case, for example, the cooling pipe 14 as the cooling means and the heater 15 as the heating means are arranged in a spiral shape along the central axis of the cylindrical shape formed by the gradient coil unit 12 so that all the magnetism can be obtained. Metal cooling or heating may be performed. In this case, the cooling pipe 14 and the heater 15 may be arranged along either the inner peripheral surface or the outer peripheral surface of the gradient magnetic field coil unit 12, or the inner peripheral surface of the magnet 11 and the gradient magnetic field coil unit 12. You may arrange | position between outer peripheral surfaces. That is, any configuration may be used as long as the magnetic metal can be cooled or heated. Note that a gas such as air may be used as the refrigerant.

  (3) A configuration in which the positions of the cooling pipe 14 and the heater 15 are replaced with respect to the above embodiment may be employed. A plurality of sensors 16 may be provided. For example, one sensor 16 may be provided for each pocket 13 to individually control the temperature of each magnetic metal.

  (4) As a cooling means, a cooling mechanism conventionally provided in the gradient coil unit 12 may be used for cooling the gradient coil unit 12 itself.

  4 and 5 are diagrams showing a configuration of the gradient magnetic field coil unit 40 provided with a cooling mechanism that can be used as a cooling means. FIG. 4 is a perspective view, and FIG. 5 is a cross-sectional view in the XY plane. In FIG. 4, the gradient magnetic field coil unit 40 shows only a half broken at the YZ plane. The gradient coil unit 40 includes a main coil layer 40a, a shim layer 40b, and a shield coil layer 40c. The main coil layer 40a and the shield coil layer 40c are equivalent to the main coil layer 12a and the shield coil layer 12c in the gradient magnetic field coil unit 12. A plurality of pockets 41 equivalent to the pockets 13 are provided in the shim layer 40b. Further, in the shim layer 40b, a plurality of cooling tubes 42 are arranged on a circumference centered on the Z axis. Each of the cooling tubes 42 is arranged parallel to the Z axis. Two cooling tubes 42 are arranged in such a manner that two pockets sandwich one pocket 41. The cooling tube 42 has a substantially rectangular tube shape or a substantially cylindrical shape, and the inside thereof becomes a flow path through which cooling water flows. The plurality of cooling tubes 42 are connected as shown in FIG. 4 at the side end of the gradient magnetic field coil unit 40 so that the flow paths formed by them are connected to one.

  (5) As the heating means, the main coil or shield coil of the gradient magnetic field coil unit 12 may be used. That is, the magnetic metal can be heated by switching the energization to the main coil and the shield coil of the gradient coil unit 12 to generate heat when shooting is not performed. Among known imaging methods in MRI, there are an imaging method in which the non-uniformity of the main magnetic field does not matter so much and an imaging method in which a major problem occurs. Therefore, if the temperature of the magnetic metal is low, the former imaging method is used, and if the latter imaging method is used after the temperature of the magnetic metal has risen to the target temperature, the main coil when no imaging is performed. Switching to the energization of the shield coil can also be omitted.

  (6) The temperature control of the magnetic metal as in the embodiment may be performed only at the time of photographing using the latter photographing method of the two types of imaging methods.

  (7) It is desirable that the target temperature is a temperature at which the uniformity of the main magnetic field is the highest. However, even if the target temperature deviates from such a temperature, if the uniformity of the main magnetic field is not changed during the photographing, the image quality can be improved as compared with the case where it changes. Therefore, the target temperature may be changed automatically or manually. When the target temperature is automatically changed, for example, when the temperature of the magnetic metal is low immediately after the start of the MRI apparatus 100, the target temperature is set low, and after the temperature of the magnetic metal has sufficiently increased, the target temperature is increased. It is conceivable to set to As a result, immediately after startup, it is possible to reduce the time required for the temperature of the magnetic metal to rise to the target temperature, and to shorten the time required to start imaging. After that, the target temperature can be set to a temperature at which the uniformity of the main magnetic field is increased, so that it is possible to perform imaging with higher image quality.

  (8) Even if the temperature of the magnetic metal fluctuates to some extent, if the fluctuation range is within a certain range, the influence of the fluctuation of the uniformity of the main magnetic field on the image quality is small. For this reason, the target temperature may include a certain width.

  (9) The present invention can also be applied to a magnetic resonance apparatus that does not perform imaging.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

1 is a schematic view of a part of an MRI apparatus 100 according to an embodiment of the present invention. The perspective view which shows the structure of the gradient magnetic field coil unit 12 in FIG. Sectional drawing in the XY plane of the gradient magnetic field coil unit 12 in FIG. The perspective view which shows the structure of the gradient magnetic field coil unit 40 provided with the cooling mechanism divertable as a cooling means for magnetic metals. Sectional drawing in XY plane of the gradient magnetic field coil unit 40 provided with the cooling mechanism which can be diverted as a cooling means for magnetic metals.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Gantry, 11 ... Magnet, 12, 40 ... Gradient magnetic field coil unit, 12a, 40a ... Main coil layer, 12b, 40b ... Shim layer, 12c, 40c ... Shield coil layer, 13, 40 ... Pocket, 14 ... Cooling pipe , 15 ... heater, 16 ... sensor, 21 ... static magnetic field power supply, 22 ... gradient magnetic field power supply, 23 ... RF coil, 24 ... transmitter, 25 ... receiver, 26 ... sequencer, 27 ... system controller, 28 ... input device, DESCRIPTION OF SYMBOLS 29 ... Operation unit, 30 ... Memory | storage unit, 31 ... Display, 32 ... Heater control part, 33 ... Flow control part, 42 ... Cooling tube, 100 ... MRI apparatus.

Claims (10)

In the magnetic resonance apparatus in which a plurality of magnetic metals are accommodated in the accommodating portion for correcting the uniformity of the main magnetic field,
Obtaining means for obtaining temperature information related to any of a temperature of the magnetic metal housed in the housing part, a temperature of the housing part, and a temperature in the vicinity of the housing part;
Temperature changing means for changing the temperature of the magnetic metal housed in the housing portion;
During the placement work of the magnetic metal in the housing portion , based on the temperature information acquired by the acquisition means, the temperature of the magnetic metal is adjusted to a target temperature set higher than normal temperature , and at the time of imaging, A magnetic resonance apparatus comprising: control means for controlling the temperature changing means so as to adjust the temperature of the magnetic metal to the target temperature based on the temperature information obtained by the obtaining means . The magnetic resonance apparatus according to claim 1,
The temperature changing means includes
Cooling means for cooling the magnetic metal;
Heating means for heating the magnetic metal,
The control means comprises a control means for controlling the cooling capacity of the cooling means and the heating capacity of the heating means so that the temperature of the magnetic metal is adjusted to the target temperature. .   3. The magnetic resonance apparatus according to claim 2, wherein the cooling means cools the magnetic metal using cooling water.   3. The magnetic resonance apparatus according to claim 2, wherein the cooling means cools the magnetic metal using a gas. 3. The magnetic resonance apparatus according to claim 2 , wherein the heating unit heats the magnetic metal with a heater. The magnetic resonance apparatus according to claim 2.
Further comprising gradient magnetic field generating means for generating a gradient magnetic field superimposed on the main magnetic field,
And the said control means makes the said gradient magnetic field generation means function as said heating means by operating the said gradient magnetic field generation means in order to raise the temperature of the said magnetic metal, The magnetic resonance apparatus characterized by the above-mentioned .   2. The magnetic resonance apparatus according to claim 1, wherein the acquisition unit measures any one of a temperature of the magnetic metal housed in the housing portion, a temperature of the housing portion, and a temperature in the vicinity of the housing portion. A magnetic resonance apparatus comprising a sensor. The magnetic resonance apparatus according to claim 7 , wherein the temperature sensor is disposed at a position where the temperature changes with a known correlation coefficient with respect to a temperature change of the magnetic metal,
Wherein, the magnetic resonance apparatus characterized by controlling the temperature controller to adjust the temperature of the magnetic metal which is estimated on the basis of said correlation coefficient between the measured temperature by the temperature sensor.   2. The magnetic resonance apparatus according to claim 1, wherein the target temperature is a temperature that maintains uniformity of the main magnetic field. 2. The magnetic resonance apparatus according to claim 1, wherein the control means starts control of the temperature changing means for adjusting the temperature of the magnetic metal prior to imaging start time.

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