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CN-122017702-A - Magnetic resonance imaging apparatus and control method for refrigerator

CN122017702ACN 122017702 ACN122017702 ACN 122017702ACN-122017702-A

Abstract

The invention aims to provide a magnetic resonance imaging device and a control method of a refrigerator, wherein the magnetic resonance imaging device prolongs the replacement life of the refrigerator and reduces the replacement frequency of the refrigerator so as to improve the operation rate of an MRI device. The cold head life extension mode is performed. In the cold head life extension mode, a displacer of a refrigerator is moved at a constant frequency lower than a predetermined upper limit frequency regardless of the temperature of a superconducting coil, and a driving frequency of a compressor driving part adjusted by a compressor inverter is controlled according to the temperature of the superconducting coil.

Inventors

  • YAO TAKESHI

Assignees

  • 富士胶片株式会社

Dates

Publication Date
20260512
Application Date
20251110
Priority Date
20241111

Claims (11)

  1. 1. A magnetic resonance imaging apparatus, characterized in that, Has a superconducting magnet for generating a static magnetic field in a shooting space, The superconducting magnet includes a superconducting coil, a container accommodating the superconducting coil, a coldhead mounted to the container, a compressor supplying compressed refrigerant gas to the coldhead, and a processor, The compressor includes a mechanism part, a compressor driving part which periodically moves the mechanism part and compresses the refrigerant gas, and a compressor inverter which adjusts a driving frequency of the compressor driving part, The cold head includes a cylinder to which the refrigerant gas compressed by the compressor is supplied, a displacer disposed in the cylinder, and a displacer driving unit that periodically moves the displacer in the cylinder, The cylinder body of the cold head is connected with the superconducting coil through a metal heat guiding component and cools the superconducting coil, The processor has a cold head life extension mode in which the displacer is moved at a constant frequency lower than a predetermined upper limit frequency regardless of the temperature of the superconducting coil, and the driving frequency of the compressor driving section adjusted by the compressor inverter is controlled according to the temperature of the superconducting coil.
  2. 2. The magnetic resonance imaging apparatus according to claim 1, wherein, The displacer drive unit and the compressor inverter are supplied with electric power of a constant frequency from a commercial ac power supply.
  3. 3. The magnetic resonance imaging apparatus according to claim 1, wherein, The cold head further comprises an inverter for cold head for adjusting the driving frequency of the displacer driving section, The processor controls the inverter for cold head in addition to the inverter for compressor, The cold head life prolonging mode of the processor comprises a shooting time mode and a non-shooting time mode, In the imaging mode, the displacer is continuously operated at the constant frequency regardless of the temperature of the superconducting coil.
  4. 4. A magnetic resonance imaging apparatus according to claim 3, wherein, The processor operates the displacer at a frequency smaller than the constant frequency of the photographing mode in the non-photographing mode.
  5. 5. A magnetic resonance imaging apparatus according to claim 3, wherein, The processor stops the displacer according to the temperature of the superconducting coil in the non-photographing mode.
  6. 6. A magnetic resonance imaging apparatus according to claim 3, wherein, The processor determines the constant frequency at which the displacer is moved based on a repetition frequency used in parameters of a cine sequence performed by the magnetic resonance imaging apparatus for cine.
  7. 7. The magnetic resonance imaging apparatus according to claim 1, wherein, The processor controls the driving frequency of the compressor driving unit according to the temperature of the superconducting coil, and stops the compressor and the displacer when the driving frequency of the compressor driving unit reaches a predetermined lower limit frequency.
  8. 8. The magnetic resonance imaging apparatus according to claim 1, wherein, The processor controls the driving frequency of the compressor driving unit according to the temperature of the superconducting coil, and stops the compressor and the displacer when the temperature of the superconducting coil reaches a predetermined lower limit temperature.
  9. 9. The magnetic resonance imaging apparatus according to claim 7, wherein, The processor is configured to restart the compressor and the displacer when a predetermined time has elapsed after stopping the compressor and the displacer, when the temperature of the superconducting coil reaches a predetermined upper limit temperature, or when the pressure in the vessel reaches a predetermined upper limit pressure.
  10. 10. The magnetic resonance imaging apparatus according to claim 1, wherein, The processor executes the cold head life extension mode when the magnetic resonance imaging apparatus is in a photographing state or a photographing standby state.
  11. 11. A control method for a refrigerator provided in a superconducting magnet of a magnetic resonance imaging apparatus, The refrigerator comprises a cold head provided with a superconducting magnet, and a compressor for supplying compressed refrigerant gas to the cold head, The control method is characterized in that, The displacer of the cold head is moved at a constant frequency lower than a predetermined upper limit frequency regardless of the temperature of the superconducting magnet, and the driving frequency of the compressor driving part of the compressor is controlled according to the temperature of the superconducting magnet.

Description

Magnetic resonance imaging apparatus and control method for refrigerator Technical Field The present invention relates to a magnetic resonance imaging (Magnetic Resonance Imaging, hereinafter referred to as MRI) apparatus. Background An MRI apparatus is known that cools a superconducting magnet using liquid helium. The superconducting coil is disposed in a liquid helium container, and the liquid helium container is provided with a cold head of a refrigerator that cools and re-liquefies vaporized helium. Patent document 1 discloses a technique of changing the driving frequency of a compressor (compressor) of a refrigerator so as to change the cooling capacity in order to make the pressure in a liquid helium vessel constant. On the other hand, an MRI apparatus that does not use liquid helium is also known. For example, patent document 2 discloses an MRI apparatus in which bobbins of superconducting coils disposed in a vacuum vessel are conduction-cooled by cold heads of two or more refrigerators. An inverter is connected to a compressor of the refrigerator, and the inverter is controlled according to the temperature of the superconducting coil unit. Thereby, the capacity of the compressor is changed, and the temperature of the superconducting coil unit is controlled to be constant. Patent document 1 Japanese patent No. 5960152 Patent document 2 Japanese patent application laid-open No. 2013-144099 MRI apparatuses using superconducting coils must use a refrigerator in order to cool the superconducting coils. When the refrigerator is replaced, the MRI apparatus needs to be stopped. Disclosure of Invention The purpose of the present invention is to improve the operation rate of an MRI device by prolonging the replacement life of a refrigerator and reducing the replacement frequency of the refrigerator. According to one aspect of the present invention, there is provided a magnetic resonance imaging apparatus of a superconducting magnet, which has a function of generating a static magnetic field in a shooting space. The superconducting magnet includes a superconducting coil, a container accommodating the superconducting coil, a cold head mounted to the container, a compressor supplying compressed refrigerant gas to the cold head, and a processor. The compressor includes a mechanism unit, a compressor driving unit that periodically moves the mechanism unit to compress a refrigerant gas, and a compressor inverter that adjusts a driving frequency of the compressor driving unit. The cold head includes a cylinder to which refrigerant gas compressed by a compressor is supplied, a displacer disposed in the cylinder, and a displacer drive unit that periodically moves the displacer in the cylinder. The cylinder body of the cold head is connected with the superconducting coil through a metal heat guiding component and cools the superconducting coil. The processor has a cold head life extension mode in which the displacer is moved at a constant frequency lower than a predetermined upper limit frequency regardless of the temperature of the superconducting coil, and the driving frequency of the compressor driving section adjusted by the compressor inverter is controlled according to the temperature of the superconducting coil. Effects of the invention According to the present invention, the number of movements of the displacer is reduced by operating the MRI apparatus in the cold head life extension mode, so that the replacement life of the refrigerator can be extended. This reduces the frequency of replacement of the refrigerator of the MRI apparatus, and improves the operation rate of the MRI apparatus. Drawings Fig. 1 is a block diagram showing the overall configuration of an MRI apparatus according to an embodiment of the present invention. Fig. 2 is a cross-sectional view showing the arrangement of a superconducting magnet or the like of the MRI apparatus shown in fig. 1. Fig. 3 is a view showing a cross-sectional structure of a superconducting magnet of the MRI apparatus of fig. 1. Fig. 4 is a sectional view showing the structure of the cold head 107 and the compressor 108 of the superconducting magnet of fig. 3. Fig. 5 is a flowchart showing control of the cold head 107 and the compressor 108 by the processor of the superconducting magnet according to embodiment 1. Fig. 6 is a flowchart showing control of the cold head 107 and the compressor 108 by the processor of the superconducting magnet according to the modification of embodiment 1. Fig. 7 is a flowchart showing control of the cold head 107 and the compressor 108 by the processor of the superconducting magnet according to embodiment 2. Fig. 8 (a) is a graph showing the input heat based on photographing and the operating frequency of the compressor of the superconducting magnet according to embodiment 4, and fig. 8 (b) is a graph showing the operating frequency and the magnet temperature of the compressor of the superconducting magnet according to embodiment 4. Fig.