JP2008125928A - Magnetic resonance imaging apparatus provided with shim tray temperature controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MRI apparatus capable of suppressing the temperature change of a shim iron piece for magnetic field adjustment based on room temperature change and the heat generation of a gradient magnetic field coil, reducing the fluctuation of magnetic field strength and magnetic field uniformity and improving the resolution of images. <P>SOLUTION: The magnetic resonance imaging apparatus comprises: a magnet for generating a static magnetic field in an imaging space; the gradient magnetic field coil for generating a gradient magnetic field in the imaging space; a shim iron piece for adjusting the uniformity of the static magnetic field; a shim tray for holding the shim iron piece by an optional distribution; a transmission coil of a high frequency for exciting magnetic resonance; a reception coil for receiving nuclear magnetic resonance signals from an object; and a temperature controller for controlling the shim iron piece and the shim tray to an optional temperature. Since the shim iron piece and the shim tray are controlled to the optional temperature, the temperature change of the shim iron piece for the magnetic field adjustment based on the room temperature change and the heat generation of the gradient magnetic field coil is suppressed. Thus, the fluctuation of he magnetic field strength and the magnetic field uniformity is reduced and the resolution of the images is improved as a result. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus for nuclear magnetic resonance imaging (Nuclear Magnetic Resonance Imaging, hereinafter referred to as “MRI”), and in particular, the temperature of shim iron based on room temperature changes, gradient magnetic field coils, and the like. The present invention relates to an MRI apparatus including a shim tray temperature control device for suppressing magnetic field fluctuation due to change.

  MRI is an imaging method using an NMR (Nuclear Magnetic Resonance) phenomenon. NMR is a phenomenon in which radio wave energy of a specific frequency (Larmor frequency) is selectively absorbed when a certain kind of atomic nucleus (NMR nuclide) is placed in a uniform static magnetic field. In the NMR imaging method, the existence density of the target nuclide is imaged by a combination of non-ionizing electromagnetic radiation (radio waves), a static magnetic field, and a gradient magnetic field. NMR is regarded as a resonance phenomenon with respect to radio waves of atomic nuclei.

  The NMR imaging method includes a method of measuring electromagnetic induction (FlD: Free Induction Decay) emitted immediately after irradiation of an excitation radio wave pulse, or an echo signal by a combination of 90 ° and 180 ° pulses. There is a method of using.

  The method of reconstructing into a two-dimensional image (MRI) uses three elements of the wave, that is, frequency (wavelength), phase, and amplitude. In order to obtain a digital image, it is necessary that the x and y coordinates and the gradation (signal intensity) at the coordinates are determined in all the matrices. In MRI, amplitude is used for signal intensity, and frequency (wavelength) and phase are used for x and y coordinates. Any of frequency, phase, and slice selection (meaning a tomographic plane described later) can generate a gradient magnetic field in a static magnetic field, thereby determining a signal intensity having position information.

  As a method for mathematically calculating frequency information, a Fourier transform method (Fourier transform, a calculation method for transforming spatiotemporal data into frequency space data) is used.

  The frequency direction readout method is to generate a gradient magnetic field of aT / m (1T (tesla) = 10 kG (kilo gauss), magnetic field change per gradient unit ≡ gradient magnetic field) in the x-axis direction in the space of the static magnetic field B0. The frequency νx on the x-coordinate due to the effective static magnetic field in the x-axis direction is given by the following equation.

νx = γ / 2π × (B0 + ax)
B0: Static magnetic field strength, γ: Rotational magnetic ratio, a: Gradient magnetic field Information in the x-axis direction can be obtained at a time, and is referred to as a reading direction in the sense that the information is obtained.

  Similarly, a gradient magnetic field is applied in the y-axis direction in the phase direction, but this magnetic field is much smaller than the magnetic field strength in the readout direction. The phase angle 360 ° is divided according to the matrix size, and the number of divisions is obtained each time a signal is taken. Must be changed. For this reason, it is necessary to repeat the combination of pulses for obtaining the NMR signal by the number of divisions. A series of repetitions of this RF pulse is called an MRI pulse series.

  In order to create a tomographic image, it is necessary to select the thickness of the tomographic plane (slice). Slice selection is made possible by generating a gradient magnetic field along an axis perpendicular to the slice cross section. This gradient magnetic field is the strongest gradient magnetic field, and the magnetic field strength is increased in order to reduce the slice thickness.

  Medical MRI mainly images a three-dimensional distribution of nuclear magnetic resonance signals of hydrogen nuclei in a living body. For this reason, an image density corresponding to the content of hydrogen atoms in the living tissue can be obtained, and as a result, a tissue shape, that is, a morphological image can be obtained.

  When the strength of the static magnetic field in the sky that images the three-dimensional distribution of the magnetic resonance signal changes from a predetermined value or the uniformity of the static magnetic field is disturbed, the frequency and phase of the signal change, and the image is disturbed. Occurs. Therefore, medical MRI requires extremely high magnetic field uniformity and stability at the ppm level. Furthermore, MR spectroscopy is a technology that has been developed in recent years. MR spectroscopy is a technique for identifying a substance from a chemical shift of a magnetic resonance frequency, and can obtain distribution information of a specific substance in a living body. Since this chemical shift amount is very small, even higher discrimination in magnetic field uniformity and stability is required.

  On the other hand, the gradient magnetic field coil that generates the gradient magnetic field is repeatedly heated by a strong pulse current, so that heat generation increases. However, in recent high-field type magnets, heat generation in the gradient magnetic field coil tends to increase. And since the gradient magnetic field coil is arrange | positioned in the vicinity of the shim iron piece which finely adjusts distribution of a static magnetic field, the shim iron piece becomes easy to receive a temperature fluctuation | variation by the heat_generation | fever of a gradient magnetic field coil.

  In general, the saturation magnetization of a ferromagnetic material such as iron has a property of weakening as the temperature increases. This is mainly due to the fact that the orientation of the internal atomic spin that creates the magnetization is randomized by thermal energy. Therefore, if the magnetic material of the permanent magnet used for MRI, the magnetic pole for strengthening / correcting the magnetic field, the yoke, the shim piece for fine adjustment, etc. are subjected to temperature fluctuations, the magnetic field strength and uniformity of the imaging air fluctuate. To do.

  As an invention for suppressing the magnetic field fluctuation caused by the temperature change in the MRI magnet and around the magnet, a heat absorption plate is attached between the X axis gradient magnetic field coil and the Y axis gradient magnetic field coil. There is one in which a heat pipe that transfers heat is joined to a groove, and heat is radiated to free space by a fin attached to the tip of the heat pipe (see, for example, Patent Document 1). In Patent Document 1, the heat generated by driving the gradient magnetic field coil can escape to the free space without being trapped in the gap between the gradient magnetic field coil and the magnetic pole piece of the static magnetic field generation magnetic circuit. Temperature can be stabilized. However, the technique described in Patent Document 1 discharges the heat generated by the gradient magnetic field coil to the outside, and does not take into account the change in room temperature.

  In some cases, the heat generated by the gradient coil prevents the magnetic pole of the permanent magnet from being heated using a good thermal conductor and a heat pump (see, for example, Patent Document 2). In Patent Document 2, a thermoelectric heat pump is controlled by a temperature sensor.

  Furthermore, there is one that detects the temperature of the magnet and its surroundings and corrects the magnetic field with a shim coil (see, for example, Patent Document 3). When the temperature of the shim tray changes, error magnetic fields in many modes are generally generated. Therefore, it is difficult to correct all of these changes with the shim coil. In order to correct this, it is necessary to directly control the temperature of the shim tray.

JP-A-5-285119 Special Table 2003-524445 JP 2000-342554 A

  The object of the present invention is to suppress the temperature change of the shim iron piece for adjusting the magnetic field based on the change in room temperature and the heat generation of the gradient magnetic field coil, reduce the fluctuation of the magnetic field intensity and the magnetic field uniformity, and enable high resolution of the image. It is to provide an MRI apparatus.

  A magnetic resonance imaging apparatus according to the present invention includes a magnet that generates a static magnetic field in an imaging space, a gradient magnetic field coil that generates a gradient magnetic field in the imaging space, a shim iron piece that adjusts the uniformity of the static magnetic field, and a shim iron piece A shim tray that holds the distribution, a high-frequency transmission coil that excites nuclear magnetic resonance, a reception coil that receives a nuclear magnetic resonance signal from the subject, a temperature control device that controls the shim iron piece and the shim tray to an arbitrary temperature, Is provided.

  According to the present invention, since the shim iron piece and the shim tray are controlled to an arbitrary temperature, the temperature change of the magnetic field adjusting shim iron piece based on the room temperature change or the heat generation of the gradient magnetic field coil can be suppressed. Therefore, fluctuations in the magnetic field strength and the magnetic field uniformity can be reduced, and as a result, the resolution of the image can be increased.

  Hereinafter, the MRI apparatus of the present invention will be described in detail with reference to FIGS.

  A first embodiment of an MRI apparatus provided with a shim tray temperature control apparatus according to the present invention will be described with reference to FIGS. In this embodiment, in order to suppress the temperature change of the shim iron piece for magnetic field adjustment based on the change in room temperature or the heat generation of the gradient magnetic field coil, the temperature-controlled air is blown to the shim iron piece and the shim tray, and the temperature of the shim iron piece and the shim tray is adjusted. The temperature is controlled to a predetermined temperature.

  First, the configuration of the vertical magnetic field type open MRI in the first embodiment will be described. The vertical magnetic field type open MRI in the present embodiment includes a magnet that generates a static magnetic field in an imaging space, a gradient magnetic field coil that generates a gradient magnetic field in the imaging space, a shim iron piece that adjusts the uniformity of the static magnetic field, and a shim iron piece. A shim tray that is held in an arbitrary distribution, a high-frequency transmission coil that excites nuclear magnetic resonance, and a reception coil that receives a nuclear magnetic resonance signal from a subject. FIG. 1 is a diagram showing the configuration of a temperature control device for a shim tray in the first embodiment. The arrangement of the gradient magnetic field coil 1 and shim tray 2 in the cross section of one magnetic pole of a vertical magnetic field type open MRI magnet and the present embodiment are shown in FIG. The structure of the shim tray temperature control apparatus which concerns is shown. FIG. 2 shows a configuration of a vertical magnetic field type open MRI magnet to which the temperature control device for shim tray in the present embodiment is applied. FIG. 1 shows the vicinity of the gradient coil 1 and shim tray 2 in the lower magnet of the MRI apparatus shown in FIG. The same configuration as that of FIG. 1 is also arranged in the gradient magnetic field coil 1 and shim tray 2 of the upper magnet. Except for the left and right connecting columns 19 shown in FIG. 2, the configuration of the magnet is basically arranged on the axis. Hereinafter, in this embodiment, the temperature control device for the shim tray in the lower magnet shown in FIG. 1 will be mainly described.

  As shown in FIGS. 1 and 2, the shim tray 2 and the gradient magnetic field coil 1 are installed in a recess called a cave-in 3. Moreover, the shim tray 2 is usually installed inside the gradient magnetic field coil 1. The shim tray 2 is made of a nonmagnetic material such as SUS or FRP. Since the magnet is basically axisymmetric, the gradient coil 1 is a column, the shim tray 2 is a disk, and the cave-in 3 is a cylindrical recess. The shim tray 2 has a number of screw holes (not shown). By screwing a magnetic shim bolt (not shown) such as iron into this screw hole and installing the shim bolt group in an arbitrary distribution, the magnetization distribution of the shim bolt is adjusted to reduce the error magnetic field, realizing the desired uniform magnetic field can do. Further, by screwing the magnetic shim bolts into the screw holes, it is possible to achieve both fixing properties and simple mounting / removal.

  The operation of adjusting the error magnetic field by arranging the shim bolt group in an arbitrary distribution (that is, inserting the shim bolt into an arbitrary screw hole of the shim tray) is called shimming. Shimming is performed with the gradient coil 1 removed and the shim tray 2 exposed. Further, shimming is performed based on information obtained by measuring an error of the excitation magnetic field. Therefore, the shim tray 2 needs to be arranged outside the magnet body such as the magnet container 4 so that the magnet can be excited and can be easily accessed by the operator. Therefore, the shim tray 2 is disposed in an environment in contact with the atmosphere, and the temperature changes according to the change in the room temperature. After the shimming, the gradient magnetic field coil 1 is installed on the upper part of the shim tray 2, and this gradient magnetic field coil is driven when an image is acquired. When the gradient magnetic field coil 1 is driven, a strong pulse current flows through the gradient magnetic field coil to generate heat, and the heat is transmitted to the shim tray 2 by heat transfer, convection, and radiation, and the temperature of the shim tray 2 is increased. Become.

  Here, in the present embodiment, in order to control the temperature of the shim tray to a predetermined temperature, the temperature-controlled air is blown to the shim tray. The temperature control device for the shim tray in this embodiment will be described in detail below. First, gaps 5 and 6 through which air flows are provided on both surfaces of the shim tray 2, that is, on both sides of the surface facing the bottom surface of the cave-in 3 and the surface facing the back surface of the gradient magnetic field coil 1 (surface opposite to the measurement space). A blower tube 7 for blowing air from a gap formed between the side surface of the gradient coil 1 and the cave-in 3 is inserted. A packing 8 made of urethane or the like is provided over the entire circumference of the gap formed between the side surface of the gradient magnetic field coil 1 and the cave-in 3 so that the blown air effectively flows on the surface of the shim tray 2. Further, an exhaust pipe 9 is provided in the gap on the opposite side to the blower pipe 7.

The blower pipe 7 for blowing air to the gaps 5 and 6 is provided with a Peltier cooler 10 for cooling the blown air and a non-induction heater 11 for heating the blown air. The heater wire inside the non-induction heater 11 is a non-inductive winding in which the energization current of the heater wire is reciprocated. The reason why the non-inductive winding is used is to prevent generation of a current / voltage due to magnetic coupling with a magnetic field by a current, a gradient magnetic field coil, or a main magnetic field at the time of quenching. A blower 12 is provided upstream of the blower tube 7 to suck in air at room temperature and apply a blowing pressure to the air. On the surface of the shim tray 2, temperature sensors 13, 14 such as thermocouples for measuring the temperature of the shim tray 2 are provided. Since the radiant heat from the gradient magnetic field coil 1 is relatively large, it is desirable to provide a plurality of temperature sensors on the side facing the gradient magnetic field coil 1 and on the opposite side (side facing the bottom of the cave-in 3) as shown in FIG. . In order to measure the room temperature, an outside air temperature sensor 15 is also provided in the vicinity of the indoor air inlet. Information from these temperature sensors 13, 14, 15 is sent to the control device 16. The control device 16 adjusts the outputs of the Peltier cooler 10 and the non-induction heater 11 based on information from the temperature sensors 13, 14, 15 and controls so that the average temperature of the shim tray 2 becomes the initial temperature. Here, the initial temperature is a temperature when the shimming operation is performed / finished. The magnet realizes the most uniform magnetic field at a predetermined magnetic field strength at the temperature when the shimming operation is performed / finished, and in order to maintain the state, the temperature when the shim tray 2 performs / terminates the shimming operation is maintained. There is a need. The initial temperature is set to a state close to the average temperature at which the magnet is used, or slightly higher than that in consideration of the average heating by the gradient coil 1.

  As described above, since the gradient magnetic field coil 1 becomes a large heat source, it is conceivable that the temperature of the shim tray 2 on the side facing the gradient magnetic field coil greatly increases. In order to alleviate this temperature rise, a thin non-magnetic, non-conductive heat insulating material may be disposed between the gradient coil 1 and the shim tray 2. Further, when the gradient coil generates a large amount of heat, the gaps 5 and 6 provided on both sides of the shim tray are provided on the side facing the gradient coil so as to increase the amount of air flowing on the side facing the gradient coil. To make it wider.

  In addition, as shown in FIG. 2, the upper magnetic pole and the lower magnetic pole of the magnet are different in height when installed in the room by about 1 m. Often different for magnetic poles. Therefore, as shown in FIG. 2, the Peltier cooler 10 and the non-induction heater 11 are provided with two upper and lower systems of an upper magnetic pole and a lower magnetic pole and controlled independently.

  The blower tube 7 is routed from the outer periphery to the inside of the cave-in 3 via the edge between the magnetic poles of the magnet. Further, the exhaust pipe 9 is routed from the cave-in 3 to the outer peripheral portion via the edge between the magnetic poles of the magnet. Since the power lead, cooling water pipe, and the like necessary for exciting the gradient coil 1 are similarly installed at this position, the blower pipe 7 and the exhaust pipe 9 are installed in parallel with the power lead, the cooling water pipe, and the like. In particular, it does not become a demerit on appearance.

  As described above, the MRI apparatus according to the present embodiment includes the shim tray temperature control device for keeping the temperature of the shim tray at a predetermined temperature. By keeping the temperature of the shim tray constant by using the shim tray temperature control device, it is possible to suppress the temperature change of the shim iron pieces for magnetic field adjustment based on the change in room temperature or the heat generation of the gradient magnetic field coil. Therefore, fluctuations in the magnetic field strength and the magnetic field uniformity can be reduced, and as a result, the resolution of the image can be increased. Further, by maintaining the temperature of the shim tray at the temperature at the time of shimming, higher magnetic field uniformity can be achieved. Such an MRI apparatus according to the present embodiment can be used for signal acquisition such as water / fat discrimination and spectroscopy that require particularly high magnetic field stability and uniformity.

  Furthermore, in the MRI apparatus in the present embodiment, the temperature of the shim tray is controlled by blowing the temperature-adjusted air to the shim tray. By using the shim tray temperature control device that blows the temperature-adjusted air to the shim tray, it is possible to configure the shim tray temperature control device using an existing heater, cooler, etc., so no special device is required, It is possible to manufacture a shim tray temperature control device very easily.

  A second embodiment of the MRI apparatus provided with the shim tray temperature control apparatus according to the present invention will be described with reference to FIG. In this embodiment, in the shim tray temperature control apparatus described in the first embodiment, an air supply duct for dispersing the air blown from the blower pipe 7 is used in order to ensure temperature uniformity. The configuration of the shim tray temperature control apparatus according to this embodiment is shown below. The overall configuration of the MRI apparatus is the same as that of the first embodiment, and thus detailed description thereof is omitted.

As described above, the gradient magnetic field coil 1 has a columnar shape, the shim tray 2 has a disk shape, and the cave-in 3 has a cylindrical recess. Attempting to exhaust air from an exhaust pipe installed at a single position of 180 degrees results in uneven temperature. To alleviate this temperature non-uniformity, it is effective to distribute the air supply along the circumference to a certain range of angles using an air supply duct. FIG. 3 is a diagram showing the shape of the duct of the shim tray temperature control device in the present embodiment. As shown in FIG. 3, the duct of the shim tray temperature control device in the present embodiment is a C-shaped air supply duct 18 whose front end is closed, and a plurality of air supply holes 17 are provided. The air supply hole 17 is opened so that air is ejected toward the center of the circle.

  In the MRI apparatus provided with the shim tray temperature control device in the present embodiment, the shim tray can be controlled to a predetermined temperature, so that the variation in the magnetic field strength and the magnetic field uniformity can be reduced as in the first embodiment. The resolution of the image can be increased. Furthermore, since the shim tray temperature control apparatus in the present embodiment can disperse the air blown from the blower pipe and supply the air to the shim tray, it is possible to ensure temperature uniformity.

  A third embodiment of the MRI apparatus provided with the shim tray temperature control apparatus according to the present invention will be described. In this embodiment, instead of the shim tray temperature control device described in the first embodiment, a plate material made of a good heat conductor is provided so as to contact the shim iron piece and the shim tray, and a plate material made of a good heat conductor by a thermoelectric heat pump. The shim iron pieces and the shim tray are controlled to an arbitrary temperature.

  In the MRI apparatus provided with the shim tray temperature control apparatus in the present embodiment, since the shim tray is controlled to a predetermined temperature, the variation in the magnetic field strength and the magnetic field uniformity can be reduced, as in the first embodiment. The resolution of the image can be increased. Furthermore, the shim tray temperature control apparatus in the present embodiment adjusts the temperature of the sheet material made of a good thermal conductor provided so as to contact (or thermally contact) the shim iron piece and the shim tray by a thermoelectric heat pump, Since the temperature of the shim tray is controlled, the temperature of the shim tray can be directly controlled as compared with the case where the temperature control device described in the first embodiment is used, and more accurate and detailed temperature control can be performed.

  A fourth embodiment of the MRI apparatus provided with the shim tray temperature control apparatus according to the present invention will be described. In this embodiment, instead of the shim tray temperature control device described in the first embodiment, the shim tray is heated by using a heater wire joined and drawn uniformly on the shim tray. The configuration of the shim tray temperature control apparatus according to this embodiment is shown below.

  In the shim tray temperature control apparatus according to the present embodiment, a heater wire is joined on the shim tray, and the heater wire is uniformly routed on the shim tray. The shim tray can be heated to an arbitrary temperature by passing a current through the heater wire.

  During operation, the shim tray is assumed to have a temperature higher than room temperature due to heat input from the gradient coil. However, the heater wire alone cannot be cooled. Therefore, at the time of shimming, the shim tray and shim iron are kept warmed by the heater wire so as to have the expected operating temperature in advance.

  After the shimming is completed, the gradient coil is attached and the gradient coil is driven. When the gradient magnetic field coil is driven, the shim tray is further heated. At this time, the energization current of the heater wire is reduced by the amount that is higher than the assumed operation temperature, and adjusted to the assumed operation temperature. As described above, the temperature control by the heater wire needs to be considered to heat up to the expected operation temperature at the time of shimming, but since the cooling device is unnecessary, the device becomes simple and the heater wire inserted into the device is thin. There is an advantage that only electric wires are required. The heater wire is arranged to be a non-inductive wiring that cancels the generated magnetic field by reciprocating the current so that the imaging space is not disturbed by the magnetic field generated by the current of the heater wire.

  In the MRI apparatus provided with the shim tray temperature control device in this embodiment, the shim tray is controlled to a predetermined temperature by heating the heater wire, so that the fluctuations in the magnetic field strength and the magnetic field uniformity are changed as in the first embodiment. As a result, the resolution of the image can be increased. Furthermore, since the shim tray temperature control device in the present embodiment can control the shim tray to a predetermined temperature only by heating the heater wire, a cooling device is unnecessary, and the configuration of the shim tray temperature control device becomes simple.

The figure which shows the structure of the temperature control apparatus of the shim tray in a 1st Example. The figure which shows the structure of the perpendicular magnetic field type | mold open MRI magnet to which the temperature control apparatus of the shim tray in a 1st Example is applied. The figure which shows the shape of the duct of the shim tray temperature control apparatus in a 3rd Example.

Explanation of symbols

1 Gradient coil 2 Shim tray 3 Cave in 4 Vacuum vessel 5 Gap (gradient field coil side)
6 Gap (Cave in bottom side)
7 Blower pipe 8 Packing 9 Exhaust pipe 10 Peltier cooler 11 Non-induction heater 12 Blower 13 Temperature sensor (opposite side of gradient magnetic field coil)
14 Temperature sensor (cave-in opposite side)
15 Outside air temperature sensor 16 Control device 17 Air supply hole 18 Air supply duct 19 Connecting column

Claims (14)

  A magnet that generates a static magnetic field in the imaging space, a gradient coil that generates a gradient magnetic field in the imaging space, a shim iron piece that adjusts the uniformity of the static magnetic field, a shim tray that holds the shim iron piece in an arbitrary distribution, A high-frequency transmission coil that excites nuclear magnetic resonance, a reception coil that receives a nuclear magnetic resonance signal from a subject, and a temperature control device that controls the shim iron piece and the shim tray to an arbitrary temperature. A magnetic resonance imaging apparatus.   A magnet that generates a static magnetic field in the imaging space, a gradient coil that generates a gradient magnetic field in the imaging space, a shim iron piece that adjusts the uniformity of the static magnetic field, a shim tray that holds the shim iron piece in an arbitrary distribution, A high-frequency transmission coil that excites nuclear magnetic resonance, a reception coil that receives a nuclear magnetic resonance signal from a subject, and a temperature control device that holds the temperature of the shim iron piece and the shim tray within an arbitrary range. A magnetic resonance imaging apparatus.   3. The magnetic resonance imaging apparatus according to claim 1, wherein the temperature control device is configured to arbitrarily move the shim iron piece and the shim tray by blowing air adjusted in temperature to a gap provided around the shim tray. A magnetic resonance imaging apparatus characterized by controlling the temperature.   4. The magnetic resonance imaging apparatus according to claim 3, wherein the temperature control device heats air that blows air to the gap, a cooler that cools air that blows air to the gap, and air that blows to the gap. 5. A magnetic resonance imaging apparatus comprising at least one of heaters.   5. The magnetic resonance imaging apparatus according to claim 4, wherein the cooler is a Peltier cooler.   5. The magnetic resonance imaging apparatus according to claim 4, wherein the heater is composed of a non-inductive heating wire.   The magnetic resonance imaging apparatus according to any one of claims 3 to 6, wherein an air circulation amount in a first gap formed between the shim tray and the gradient magnetic field coil in the gap is determined by the shim tray. A magnetic resonance imaging apparatus characterized in that it is larger than a second gap formed on the opposite side of the gradient magnetic field coil.   The magnetic resonance imaging apparatus according to claim 7, wherein the first gap is larger than the second gap. The magnetic resonance imaging apparatus according to any one of claims 3 to 8, wherein the temperature adjustment device includes an arc-shaped duct that is connected to the blower pipe and is positioned along the gap.
The nuclear magnetic resonance imaging apparatus characterized in that air whose temperature is adjusted by the temperature control device is supplied to the shim iron piece and the shim tray through an air supply hole provided in the duct. 10. The magnetic resonance imaging apparatus according to claim 3, wherein the temperature control device includes a temperature measurement device that measures the temperature of at least one of the shim iron pieces and the shim tray,
The temperature control device controls at least one of the cooler and the heater based on a measured value of at least one of the shim iron piece and the shim tray obtained by the temperature measurement device. Magnetic resonance imaging apparatus. 3. The magnetic resonance imaging apparatus according to claim 1, wherein the temperature control device is connected to the thermoelectric heat pump and the thermoelectric heat pump, and is thermally connected to at least one of the shim iron pieces and the shim tray. With a good thermal conductor,
The magnetic resonance imaging apparatus, wherein the heat conductor is heated by the heat conduction heat pump to control the shim iron pieces and the shim tray to arbitrary temperatures. The magnetic resonance imaging apparatus according to claim 11, wherein the temperature control device includes a temperature measurement device that measures the temperature of at least one of the shim iron piece and the shim tray.
The said temperature control apparatus controls the said heat heat pump based on the measured value of at least any one of the said shim iron piece and the said shim tray obtained by the said temperature measurement apparatus, The magnetic resonance imaging apparatus characterized by the above-mentioned.   13. The magnetic resonance imaging apparatus according to claim 1, wherein the temperature control device is a temperature difference between a room temperature outside the magnetic resonance imaging apparatus and a temperature of at least one of the shim iron piece and the shim tray. Based on the above, the temperature of the shim iron piece and the shim tray is controlled.   14. The magnetic resonance imaging apparatus according to claim 1, wherein the temperature control device has a temperature of the shim iron piece or the shim tray at the time of a shimming operation that is an operation of inserting the shim iron piece into the shim tray. A magnetic resonance imaging apparatus that controls temperatures of the shim iron pieces and the shim tray.

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