Magnetic resonance imaging apparatus and pressure measurement method

Abstract

To improve the accuracy of measuring pressure inside a helium container. [Solution] A magnetic resonance imaging apparatus according to one embodiment comprises a superconducting coil, a helium container, a first pressure gauge, a second pressure gauge, a valve, and a control circuit. The superconducting coil generates a static magnetic field. The helium container houses liquid helium for cooling the superconducting coil together with the superconducting coil. The first pressure gauge measures the pressure inside the helium container within a first pressure measurement range. The second pressure gauge measures the pressure inside the helium container within a second pressure measurement range that is narrower than the first pressure measurement range. The valve switches the second pressure gauge to be used for measuring the pressure inside the helium container. The control circuit controls the opening and closing of the valve based on the measurement value of the first pressure gauge.

Description

Technical Field

[0001] The embodiments disclosed in this specification and the drawings relate to a magnetic resonance imaging (MRI) apparatus and a pressure measurement method.

Background Art

[0002] An MRI apparatus is an imaging device that excites the nuclear spins of a subject placed in a static magnetic field with a high-frequency (RF: Radio Frequency) pulse at the Larmor frequency, and performs a scan to collect magnetic resonance (MR: Magnetic Resonance) signals generated from the subject along with the excitation, and generates an MR image based on the MR signals collected by the scan.

[0003] Some MRI apparatuses have a static magnetic field magnet that generates a static magnetic field and is composed of a superconducting magnet. The superconducting magnet incorporates a superconducting coil, and the superconducting coil is cooled to an extremely low temperature by liquid helium. In an MRI apparatus, when a quench occurs, the liquid helium rapidly vaporizes, and the pressure inside the helium container that houses the superconducting coil together with the liquid helium rises rapidly.

[0004] In addition, air may flow into the pipe connecting the low-temperature side helium sump and the normal-temperature side space of the helium container, and the air may solidify and cause blockage. For example, a method of evaluating the measured value by one pressure gauge arranged in the pipe is known in order to detect early that blockage has occurred in the pipe.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] One of the problems that the embodiments disclosed herein and in the drawings aim to solve is to improve the accuracy of measuring the pressure inside a helium container that houses a superconducting coil together with liquid helium. However, the problems that the embodiments disclosed herein and in the drawings aim to solve are not limited to the above problem. Problems corresponding to the effects of each configuration shown in each embodiment described later can also be positioned as other problems. [Means for solving the problem]

[0007] An MRI apparatus according to one embodiment comprises a superconducting coil, a helium container, a first pressure gauge, a second pressure gauge, a valve, and a control circuit. The superconducting coil generates a static magnetic field. The helium container houses liquid helium for cooling the superconducting coil together with the superconducting coil. The first pressure gauge measures the pressure inside the helium container within a first pressure measurement range. The second pressure gauge measures the pressure inside the helium container within a second pressure measurement range that is narrower than the first pressure measurement range. The valve switches the second pressure gauge to be used for measuring the pressure inside the helium container. The control circuit controls the opening and closing of the valve based on the measurement value of the first pressure gauge. [Brief explanation of the drawing]

[0008] [Figure 1] A block diagram showing an example of the overall configuration of an MRI apparatus according to this embodiment. [Figure 2] A block diagram showing an example of the cross-sectional structure and configuration of a superconducting magnet according to the first embodiment. [Figure 3] This diagram illustrates the case where pressure is measured using a first pressure gauge (A) and the case where pressure is measured using two differential pressure gauges (B). [Figure 4] A diagram illustrating the pressure measurement range. [Figure 5] A flowchart showing an example of operation of the pressure measurement method according to the first embodiment. [Figure 6] A block diagram showing an example of the cross-sectional structure and configuration of a superconducting magnet according to the second embodiment. [Figure 7] A flowchart showing an example of operation of the pressure measurement method according to the second embodiment. [Modes for carrying out the invention]

[0009] The MRI apparatus and pressure measurement method according to the embodiment will be described below with reference to the attached drawings. In each figure, the same elements are denoted by the same reference numerals, and redundant explanations are omitted.

[0010] (Overall configuration of the MRI system) Figure 1 is a block diagram showing an example of the overall configuration of an MRI apparatus 1 according to an embodiment. The MRI apparatus 1 comprises a pedestal 100, a control cabinet 300, an image processing device 400 (for example, a console), and a patient bed 500.

[0011] The mounting device 100 comprises a superconducting magnet 10, a gradient magnetic field coil 11, and a whole-body (WB) coil 12. These components are housed in a cylindrical casing.

[0012] The superconducting magnet 10 has a roughly cylindrical shape and generates a static magnetic field in the bore into which the patient being examined is brought. The bore is the examination space inside the cylinder of the superconducting magnet 10. The superconducting magnet 10 contains a superconducting coil 101 (see Figure 2), which is cooled to an extremely low temperature by liquid helium 102 (see Figure 2). In excitation mode, the superconducting magnet 10 generates a static magnetic field by applying a current supplied from a static magnetic field power supply (not shown) to the superconducting coil. After the superconducting magnet 10 transitions to persistent current mode, the static magnetic field power supply may be disconnected. Once the superconducting magnet 10 transitions to persistent current mode, it continues to generate a large static magnetic field for a long time, for example, for more than a year. Further details about the superconducting magnet 10 will be described later.

[0013] The gradient coil 11 has a generally cylindrical shape and is fixed inside the superconducting magnet 10 in the radial direction of the cylindrical shape. The gradient coil 11 generates a gradient magnetic field by receiving an electric current from the gradient power supply 31. The gradient coil 11 is formed by combining three coils corresponding to the mutually orthogonal X, Y, and Z axes, and these three coils receive an electric current individually from the gradient power supply 31 to generate a gradient magnetic field in which the magnetic field strength changes along the X, Y, and Z axes.

[0014] As shown in Figure 1, the left-right direction of the subject P positioned on the bed 500 is defined as the X-axis, the front-to-back direction (body thickness direction) as the Y-axis, and the head-to-foot direction as the Z-axis. The X, Y, and Z axes are orthogonal to each other.

[0015] The WB coil 12 is an RF coil that has a roughly cylindrical shape and is fixed inside the gradient magnetic field coil 11 so as to surround the subject. The WB coil 12 transmits RF pulses transmitted from the transmitter 32 to the subject and receives the MR signal emitted from the subject P by the excitation of hydrogen nuclei.

[0016] The MRI apparatus 1 may have a local coil 20 in addition to the WB coil 12. The local coil 20 is an RF coil positioned close to the subject and receives the MR signal emitted from the subject at a position close to the subject. The local coil 20 may also transmit RF pulses transmitted from the transmitter 32 to the subject. There are various types of local coils 20 depending on the imaging area of ​​the subject, such as for the head, chest (e.g., Figure 1), spine, lower limbs, and whole body.

[0017] The control cabinet 300 comprises a gradient magnetic field power supply 31, a transmitter 32, a receiver 33, and a sequence controller 34. Under the control of the sequence controller 34, the gradient magnetic field power supply 31 supplies current to the gradient magnetic field coils 11, causing the gradient magnetic field coils 11 to generate gradient magnetic fields along the X, Y, and Z axes.

[0018] Based on the instructions from the sequence controller 34, the transmitter 32 generates an RF pulse train in the Larmor frequency band as an RF transmission wave, outputs it to the RF coil, and excites the subject P.

[0019] The receiver 33 performs analog-to-digital (AD) conversion on the MR signal received by the RF coil and outputs it to the sequence controller 34. The digitized MR signal is called raw data.

[0020] Under the control of the image processing device 400, the sequence controller 34 drives the gradient magnetic field power supply 31, the transmitter 32, and the receiver 33 respectively to perform a scan of the subject P. The sequence controller 34 receives raw data from the receiver 33 during the execution of the scan and transmits the raw data to the image processing device 400.

[0021] The sequence controller 34 includes a processing circuit (not shown). The processing circuit of the sequence controller 34 is composed of, for example, a processor that executes a predetermined program, or hardware such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0022] The hospital bed 500 includes a bed body 50 and a top plate 51. The bed body 50 can move the top plate 51 in the vertical and horizontal directions, move the subject P placed on the top plate 51 to a predetermined height, and move it into the bore.

[0023] The image processing device 400 includes a processing circuit 40, a storage circuit 41, a display 42, and an input interface 43. The image processing device 400 is composed of a computer.

[0024] The memory circuit 41 is a storage medium that includes ROM (Read Only Memory), RAM (Random Access Memory), and external storage devices such as HDD (Hard Disk Drive) and optical disc drives. The memory circuit 41 stores various information and data, and stores various programs that are executed by the processor equipped in the processing circuit 40.

[0025] The display 42 is a display device such as a liquid crystal display panel, a plasma display panel, or an organic EL panel. The display 42 may also be a GUI (Graphical User Interface) that displays various information and data under the control of the processing circuit 40 and also functions as an input device.

[0026] The input interface 43 includes various input devices for the user to input various types of information and data, and an input circuit that processes signals from the input devices. Examples of input devices include a mouse, keyboard, trackball, and touch panel. When an input device is operated, the input circuit generates a signal corresponding to that operation and outputs it to the processing circuit 40.

[0027] The processing circuit 40 is, for example, a circuit equipped with a CPU or a dedicated or general-purpose processor. The processor executes various programs that are pre-stored in the memory circuit 41 or directly incorporated into the processing circuit 40.

[0028] These components enable the image processing device 400 to control the entire MRI apparatus 1. Specifically, the processing circuit 40 receives instructions regarding imaging conditions and other various information from a user, such as a medical technologist, via the input interface 43. The processing circuit 40 then instructs the sequence controller 34 to perform a scan based on the input imaging conditions. The processing circuit 40 also reconstructs the MR image based on the raw data transmitted from the sequence controller 34. The reconstructed MR image is displayed on the display 42 and stored in the memory circuit 41.

[0029] (Superelectric magnet according to the first embodiment) Figure 2 is a block diagram showing an example of the cross-sectional structure and configuration of a superconducting magnet 10 according to the first embodiment. The superconducting magnet 10 of the MRI apparatus 1 comprises a superconducting coil 101, a helium container 103, a pressure measuring device 110, and a control circuit 120.

[0030] The control circuit 120 is a circuit that includes, for example, a CPU or a dedicated or general-purpose processor. The processor executes various programs that are pre-stored in a memory circuit (not shown) or directly incorporated into the control circuit 120, thereby realizing functions corresponding to various programs. The control circuit 120 realizes a first acquisition function F1, a first determination function F2, a valve control function F3, a second acquisition function F4, a second determination function F5, and a scan control function F6. Details of the functions will be described later.

[0031] The superconducting coil 101 generates a static magnetic field. The helium container 103 houses the superconducting coil 101 along with liquid helium 102, which cools the superconducting coil 101. The helium container 103 is enclosed within the vacuum container 104. The vacuum container 104 maintains a vacuum inside and serves to insulate the helium container 103 from the outside. The piping 107 is located at the top of the helium container 103 and connects the low-temperature section 105 and the room-temperature section 106 of the helium container 103. The pressure measuring device 110 is located on the piping 107 and measures the pressure inside the helium container 103.

[0032] The pressure measuring device 110 comprises a first pressure gauge P1, a second pressure gauge P2, and a valve 113. The first pressure gauge P1 is located in a first measuring chamber 111 connected to the helium container 103, and the second pressure gauge P2 is located in a second measuring chamber 112 connected to the first measuring chamber 111 via the valve 113. Here, Figures 3(A) and 3(B) illustrate the case where pressure measurement is performed using the first pressure gauge P1 (Figure 3(A)) and the case where pressure measurement is performed using the second pressure gauge P2 (Figure 3(B)).

[0033] The first measurement chamber 111 and the second measurement chamber 112 in the pressure measuring device 110 are separated by the opening and closing of a valve 113 so that the pressure values ​​in the two measurement chambers 111 and 112 are different (Figure 3(A)), or opened so that the pressure values ​​in the two measurement chambers 111 and 112 are the same (Figure 3(B)). When the valve 113 is closed, the pressure is measured by the first pressure gauge P1, and when the valve 113 is open, the pressure is measured by the second pressure gauge P2.

[0034] Conventionally, the pressure inside the helium container 103 is measured by a single pressure gauge placed in the piping. However, for example, the pressure inside the helium container when a quench occurs is around tens of thousands (Pa: Pascals), and because the pressure measurement range is wide, it is difficult for a single pressure gauge to detect pressure changes of a few (Pa). In other words, a single pressure gauge has low pressure measurement resolution, making it difficult to detect pressure changes with the desired resolution. Therefore, it is also difficult to detect the precursors to a quench.

[0035] In contrast, in this embodiment, the pressure measuring device 110 is equipped with two pressure gauges: a first pressure gauge P1 and a second pressure gauge P2. The pressure measuring device 110 may be equipped with three or more pressure gauges. The first pressure gauge P1 measures the pressure inside the helium container 103 within a first pressure measuring range. The second pressure gauge P2 measures the pressure inside the helium container 103 within a second pressure measuring range that is narrower than the first pressure measuring range.

[0036] Here, with reference to Figure 4, the first pressure measurement range measured by the first pressure gauge P1 and the second pressure measurement range measured by the second pressure gauge P2 will be described in detail. The first pressure measurement range measured by the first pressure gauge P1 is the range between the minimum pressure value V1 and the maximum pressure value V2 of the helium container 103 (i.e., the entire pressure measurement range within the helium container 103). The first pressure gauge P1 is resistant to failure within the entire pressure measurement range within the helium container 103 and can measure the pressure within the entire pressure measurement range within the helium container 103.

[0037] The minimum pressure value V1 of the helium container 103 is, for example, the vacuum pressure value, which is the pressure value in a vacuum state. The minimum pressure value V1 of the helium container 103 may also be a predetermined negative pressure value for controlling the introduction and discharge of helium gas. The maximum pressure value V2 of the helium container 103 is tens of thousands to hundreds of thousands (for example, 160,000) (Pa).

[0038] The second pressure measurement range measured by the second pressure gauge P2 is a predetermined measurement range that includes a reference pressure value V0. The reference pressure value V0 is defined as the steady-state pressure of the helium container 103. The pressure value inside the helium container 103 is kept approximately constant during normal operation of the MRI device 1. The predetermined measurement range that includes the reference pressure value V0 is this approximately constant pressure value, for example, 3000 to 3100 (Pa).

[0039] The second pressure gauge P2 measures pressure values ​​within a narrower measurement range (e.g., 100 Pa) than the entire pressure measurement range within the helium container 103, resulting in a higher measurement resolution than the first pressure gauge P1. This enables pressure measurement with a desired resolution (e.g., a number of Pas, such as 1 to 10 Pa). In other words, the second pressure gauge P2 is configured to have a higher resolution than the first pressure gauge P1.

[0040] As mentioned above, the state in which the valve 113 is open or closed determines whether the pressure inside the helium container 103 is measured by the first pressure gauge P1 or the second pressure gauge P2.

[0041] The second pressure gauge P2 is not resistant to damage across the entire pressure measurement range within the helium container 103 and may be damaged if pressure outside the non-destructive pressure range is applied. Specifically, it may be damaged if pressure higher than the upper limit of the non-destructive pressure range is applied, or if pressure lower than the lower limit of the non-destructive pressure range is applied. Therefore, the valve 113 is opened only when the pressure value in the helium container 103 measured by the first pressure gauge P1 is within the non-destructive pressure range, thereby protecting the second pressure gauge P2 from damage. The second measurement chamber 112 is maintained at a pressure within the non-destructive pressure range regardless of the open or closed state of the valve 113.

[0042] Specifically, valve 113 is opened within the valve's opening pressure range, which is the range between the valve's opening pressure value V3 and the valve's closing pressure value V4, and closed outside of this valve's opening pressure range. The valve's opening pressure range is narrower than the non-destructive pressure range, for example, 2500 to 3500 (Pa). Furthermore, the valve's opening pressure range is wider than a predetermined measurement range that includes the reference pressure value V0.

[0043] Furthermore, the capacity of the second measuring chamber 112 of the pressure measuring device 110 is relatively and sufficiently smaller than the combined capacity of the helium container 103, the piping 107, and the first measuring chamber 111 of the pressure measuring device 110. Therefore, when the valve 113 is opened, the pressure values ​​measured are approximately the same between the first pressure gauge P1 and the second pressure gauge P2.

[0044] Referring to the flowchart in Figure 5, the opening and closing of the valve 113 in the pressure measurement method according to the first embodiment will be explained.

[0045] In step ST1, the first acquisition function F1 acquires the pressure value inside the helium container 103 measured by the first pressure gauge P1.

[0046] In step ST2, the first determination function F2 determines whether the pressure value inside the helium container 103, measured by the first pressure gauge P1, is within the range of the valve 113's opening and closing pressure value (i.e., within the opening and closing pressure range).

[0047] In step ST2, if the pressure value in the helium container 103 measured by the first pressure gauge P1 is not within the valve opening / closing pressure range, i.e., NO, the process returns to step ST1.

[0048] In step ST2, if the pressure value inside the helium container 103 measured by the first pressure gauge P1 is within the valve opening / closing pressure range, i.e., YES, the process proceeds to step ST3. In step ST3, the valve control function F3 controls the opening of valve 113. For example, if the pressure value inside the helium container 103 is greater than the valve opening pressure value V3, the valve control function F3 controls the opening of valve 113. Also, if the pressure value inside the helium container 103 is greater than the valve closing pressure value V4, the valve control function F3 controls the closing of valve 113.

[0049] Specifically, the control circuit 120 opens valve 113 when the pressure value inside the helium container 103 measured by the first pressure gauge P1 is within the valve's opening / closing pressure range. Valve 113 switches so that the second pressure gauge P2 is used to measure the pressure inside the helium container 103. The control circuit 120 controls the opening and closing of valve 113 based on the measurement value from the first pressure gauge P1.

[0050] In step ST4, the second acquisition function F4 of the control circuit 120 acquires information regarding the pressure value inside the helium container 103 measured by the second pressure gauge P2. The information regarding the pressure value is the pressure value inside the helium container 103.

[0051] In step ST5, the second determination function F5 determines whether the pressure value inside the helium container 103, measured by the second pressure gauge P2, is equal to or greater than a predetermined threshold (see Figure 4).

[0052] In step ST5, if the pressure value inside the helium container 103 measured by the second pressure gauge P2 is not above a predetermined threshold, i.e., NO, the process returns to step ST4.

[0053] In step ST5, if the pressure value inside the helium container 103 measured by the second pressure gauge P2 is equal to or greater than a predetermined threshold, i.e., YES, the process proceeds to step ST6.

[0054] In step ST6, the scan control function F6 of the control circuit 120 controls the stopping of the scan based on information regarding the pressure value. That is, if the pressure value inside the helium container 103 is above a predetermined threshold, an instruction signal is sent to the sequence controller 34 and the scan is stopped.

[0055] The information regarding the pressure value may also be the rate of change in the pressure value inside the helium container 103. If the rate of change in the pressure value inside the helium container 103 measured by the second pressure gauge P2 exceeds the rate of change in the pressure value when the MRI device 1 is operating normally and the pressure value inside the helium container 103 is kept constant, the scan may be stopped. Alternatively, the rate of change in the pressure value per unit time may be calculated from the pressure value data inside the helium container 103 measured by the second pressure gauge P2 for a certain period of time, and the scan may be stopped if the standard deviation value, which is one of the variations in the rate of change, is greater than or equal to a threshold.

[0056] According to the MRI apparatus 1 of the first embodiment, the pressure inside the helium container 103 can be accurately measured within a predetermined measurement range near a reference pressure value V0 defined as the steady-state pressure of the helium container 103. For example, if heat ingress temporarily increases during a scan in the MRI apparatus 1, the liquid helium 102 vaporizes into gaseous helium, causing a change in pressure value that is a precursor to a quench. Since the change in pressure value can be detected even at this precursor stage of a quench, control such as stopping the scan can be performed, making it possible to prevent the occurrence of a quench.

[0057] (Superelectric magnet according to the second embodiment) Figure 6 is a block diagram showing an example of the cross-sectional structure and configuration of the superconducting magnet 10 according to the second embodiment. The second embodiment differs from the first embodiment in that at least one of the heater 109c and the refrigerator 108 is controlled to approach the reference pressure value V0. Furthermore, the control circuit 120 according to the second embodiment further realizes the temperature control function F7.

[0058] The second embodiment further includes a heater 109c and a refrigerator 108. The refrigerator 108 is, for example, a compression refrigerator and is located at the top of the helium container 103. The refrigerator 108 lowers the pressure inside the helium container 103. The heater 109c is, for example, a boost heater and is located inside the helium container 103 and connected to an external temperature control unit 109a via a control line 109b. The temperature control unit 109a energizes the heater 109c to vaporize the liquid helium 102 so that the pressure inside the helium container 103, as measured by the pressure measuring device 110, does not become negative. The heater 109c raises the pressure inside the helium container 103.

[0059] The pressure measurement method according to the second embodiment will be described with reference to the flowchart in Figure 7. In step ST5, if the pressure value in the helium container 103 measured by the second pressure gauge P2 is above a predetermined threshold (for example, if the pressure value in the helium container 103 rises), the process proceeds to step ST7. In the second embodiment, if the pressure value in the helium container 103 measured by the second pressure gauge P2 is below a predetermined threshold (for example, if the pressure value in the helium container 103 falls), the process may proceed to step ST7. The explanation of steps ST1 to ST5, which overlap with the first embodiment, will be omitted.

[0060] In step ST7, the temperature control function F7 of the control circuit 120 controls the heater 109c and the refrigerator 108 to approach the reference pressure value V0 based on information regarding the pressure value. For example, if the pressure value inside the helium container 103 rises, the temperature control function F7 controls the operation to lower the pressure value inside the helium container 103 by driving the refrigerator 108 or stopping the heater 109c. For example, if the pressure value inside the helium container 103 falls, the temperature control function F7 controls the operation to raise the pressure value inside the helium container 103 by stopping the refrigerator 108 or driving the heater 109c.

[0061] Generally, during normal operation of the MRI device 1, the pressure value inside the helium container 103 is kept constant relative to atmospheric pressure. According to the MRI device 1 of the second embodiment, even if a sudden change in atmospheric pressure occurs and the atmospheric pressure rises rapidly, the pressure value inside the helium container 103 can be controlled to a constant level by stopping the refrigerator 108 and driving the heater 109c. Furthermore, even if heat ingress temporarily increases during scanning, the pressure value inside the helium container 103 can be controlled to a constant level by stopping the heater 109c and driving the refrigerator 108.

[0062] According to the MRI apparatus and pressure measurement method of at least one embodiment described above, the accuracy of measuring the pressure inside a helium container housing a superconducting coil together with liquid helium can be improved.

[0063] In the above embodiments, the term "processor" refers to, for example, a dedicated or general-purpose CPU (Central Processing Unit), GPU (Graphics Processing Unit), or Application Specific Integrated Circuit (ASIC), or a programmable logic device. Programmable logic devices include, for example, simple programmable logic devices (SPLDs), complex programmable logic devices (CPLDs), and field programmable gate arrays (FPGAs).

[0064] If the processor is, for example, a CPU, it implements various functions by reading and executing programs stored in memory circuits. Alternatively, if the processor is, for example, an ASIC, instead of storing programs in memory circuits, functions equivalent to those programs are directly incorporated as logic circuits within the processor's circuitry. In this case, the processor implements various functions through hardware processing that reads and executes the programs incorporated within the circuitry. Furthermore, a processor can also implement various functions by combining software and hardware processing.

[0065] Furthermore, although the above embodiment shows an example where a single processor in the processing circuit implements each function, a processing circuit may be configured by combining multiple independent processors, with each processor implementing each function. Also, when multiple processors are provided, the memory circuit for storing programs may be provided individually for each processor, or a single memory circuit may store programs corresponding to the functions of all processors together.

[0066] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0067] 1…Magnetic Resonance Imaging (MRI) machine 10…Superconducting magnet 101…Superconducting coil 102…Liquid helium 103…Helium container 111…First measurement room 112…Second measurement room 113…Valve 120…Control circuit P1…First pressure gauge P2…Second pressure gauge

Claims

1. A superconducting coil for generating a static magnetic field, A helium container containing liquid helium for cooling the superconducting coil, together with the superconducting coil, A first pressure gauge for measuring the pressure inside the helium container within a first pressure measurement range, A second pressure gauge for measuring the pressure inside the helium container in a second pressure measurement range that is narrower than the first pressure measurement range, A valve that switches the second pressure gauge so that it is used to measure the pressure inside the helium container, The system includes a control circuit that controls the opening and closing of the valve based on the measurement value of the first pressure gauge, Magnetic resonance imaging device.

2. The first pressure gauge is located in a first measuring chamber connected to the helium container, and the second pressure gauge is located in a second measuring chamber connected to the first measuring chamber via a valve. The magnetic resonance imaging apparatus according to claim 1.

3. The second pressure gauge is configured to have a higher resolution than the first pressure gauge. The magnetic resonance imaging apparatus according to claim 1.

4. The second pressure measurement range is a predetermined measurement range that includes a reference pressure value defined as the steady-state pressure of the helium container. The magnetic resonance imaging apparatus according to claim 1.

5. The first pressure measurement range is the range between the vacuum pressure value and the maximum pressure value of the helium container. The magnetic resonance imaging apparatus according to claim 1.

6. The aforementioned control circuit is The valve is opened when the pressure value inside the helium container measured by the first pressure gauge is within the opening / closing pressure range. Information regarding the pressure value inside the helium container is obtained using the second pressure gauge. The magnetic resonance imaging apparatus according to claim 4.

7. The information relating to the pressure value includes at least one of the pressure value in the helium container and the rate of change of the pressure value. The magnetic resonance imaging apparatus according to claim 6.

8. The control circuit controls the stopping of the scan based on the information regarding the pressure value. The magnetic resonance imaging apparatus according to claim 6.

9. A heater for increasing the pressure inside the helium container, The system further comprises a refrigerator for reducing the pressure inside the helium container, The control circuit, based on information regarding the pressure value, controls at least one of the heater and the refrigerator to approach the reference pressure value. The magnetic resonance imaging apparatus according to claim 6.

10. A superconducting coil for generating a static magnetic field, A helium container housing the superconducting coil together with liquid helium for cooling, A first pressure gauge for measuring the pressure inside the helium container within a first pressure measurement range, A second pressure gauge for measuring the pressure inside the helium container in a second pressure measurement range that is narrower than the first pressure measurement range, A pressure measurement method in a magnetic resonance imaging apparatus, comprising a valve that switches the pressure gauge used to measure the pressure to either the first pressure gauge or the second pressure gauge, Based on the measurement value of the first pressure gauge, control is performed to open and close the valve. Pressure measurement method.

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