WO2015110389A1 - Cooling device and method for a magnetic resonance imaging system - Google Patents

Cooling device and method for a magnetic resonance imaging system Download PDF

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Publication number
WO2015110389A1
WO2015110389A1 PCT/EP2015/050902 EP2015050902W WO2015110389A1 WO 2015110389 A1 WO2015110389 A1 WO 2015110389A1 EP 2015050902 W EP2015050902 W EP 2015050902W WO 2015110389 A1 WO2015110389 A1 WO 2015110389A1
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Prior art keywords
cold head
cooling liquid
working
cooling
detection result
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PCT/EP2015/050902
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French (fr)
Inventor
Zhi Chun Fang
Le JIANG
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Siemens PLC
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Siemens PLC
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/3804—Additional hardware for cooling or heating of the magnet assembly, for housing a cooled or heated part of the magnet assembly or for temperature control of the magnet assembly
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/04—Cooling

Definitions

  • Magnetic resonance imaging is an imaging technology involving biomagnetics and nuclear spin which has advanced rapidly with the development of computer technology, electronic circuit technology and superconductor technology. It uses a magnetic field and radio frequency (RF) pulses to induce nutation of precessing hydrogen nuclei (i.e. H+) in human tissue, to generate RF signals which are processed by a computer to form an image. If an object is placed in a magnetic field and irradiated by suitable electromagnetic waves to produce resonance therein, and electromagnetic waves released thereby are then analysed, it is possible to learn the positions and types of the atomic nuclei of which the object is composed. On this basis, a precise three-dimensional image of the interior of the object can be drawn. For instance, a moving picture of contiguous slices can be obtained by performing an MRI scan of the human brain, starting at the crown and continuing all the way to the base.
  • RF radio frequency
  • the embodiments of the present invention propose a cooling device for an MRI system, wherein the amount of cooling liquid volatilized when the cold head is not working is reduced.
  • the cold head operational state detection unit is for detecting a state of an electric motor of the cold head; wherein the detection result is that the cold head is not working when an electric motor of the cold head is in a shut-down state; and/or the detection result is that the cold head is working when the electric motor of the cold head is in an operational state.
  • An MRI system comprising any one of the cooling devices described above.
  • the method comprises: providing a valve in the cooling liquid volatilization channel; detecting an operational state of the cold head, wherein the valve is opened when the detection result is that the cold head is not working; and/or the valve is closed when the detection result is that the cold head is working.
  • the method comprises: comparing a gas return pipe pressure and a gas supply pipe pressure of a compressor connected to the cold head; wherein the detection result is that the cold head is not working when the gas supply pipe pressure is equal to the gas return pipe pressure; and/or the detection result is that the cold head is working when the gas supply pipe pressure is greater than the gas return pipe pressure.
  • the method comprises: detecting a state of an electric motor of the cold head; wherein the detection result is that the cold head is not working when an electric motor of the cold head is in a shut ⁇ down state; and/or the detection result is that the cold head is working when the electric motor of the cold head is in an operational state.
  • the control unit opens the cooling liquid volatilization channel, and when the cold head is working, the cooling liquid volatilization channel on the cold head side is closed.
  • the pre-cooling effect of volatilizing gas on the cold head is exploited, reducing volatilization of cooling liquid, and saving a significant amount of cooling liquid.
  • Fig. 2 is a drawing of the internal structure of the cooling liquid tank of the present invention.
  • Fig. 3 is a structural drawing of the control unit according to the present invention.
  • Fig. 4 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and pneumatic drive in the present invention, wherein the cold head is working normally.
  • Fig. 5 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and pneumatic drive in the present invention, wherein the cold head is not working.
  • Fig. 6 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and a cold head electric motor in the present invention, wherein the cold head is working normally.
  • Fig. 7 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and a cold head electric motor in the present invention, wherein the cold head is not working.
  • Fig. 8 is a flow chart of the cooling method for an imaging system according to the present invention.
  • a superconducting magnetic resonance apparatus generally uses liquid helium as a cooling medium.
  • Helium has the lowest boiling point of any substance currently known, with a boiling point of 4.2 K, and will not solidify at temperatures extremely close to absolute zero; therefore liquid helium can be used to obtain a low temperature close to absolute zero, to establish and maintain a superconducting environment for superconducting coils .
  • a superconducting magnet employs a multi-layer vacuum thermal isolation structure.
  • heat conduction to the superconducting magnet is difficult to prevent entirely, and liquid helium will evaporate to remove any heat that has been introduced, to maintain a low temperature of 4.2 K.
  • superconducting magnetic resonance systems are generally all equipped with a cooling system to supply cold.
  • the cooling system generally comprises three parts, namely a cold head, a helium compressor and a water cooling unit.
  • the cold head consists of components such as an electric drive motor, a rotary valve, a gas distributor plate, a piston and a cylinder.
  • the cooling system operates in the following manner: the electric drive motor controls the rotary valve to rotate on the gas distributor plate or some other gas distribution method is employed; the piston is controlled to compress and expand gas, to form an alternating cycle between a high-pressure gas chamber and a low-pressure gas chamber, and complete the process of sucking in high-pressure, low-temperature helium gas (e.g. at 20 Bar, 8°C) and discharging low-pressure, high- temperature helium gas (e.g. 8 Bar, 30°C), while at the same time carrying heat from within the cold head into the helium compressor .
  • high-pressure, low-temperature helium gas e.g. at 20 Bar, 8°C
  • the low-pressure helium gas returned is compressed in the helium compressor to increase the pressure thereof, undergoes heat exchange with cooling water supplied by the water cooling unit as well as oil filtering, and then high-pressure helium gas is conveyed back to the cold head, to set up a helium gas circulation process.
  • a cooling liquid volatilization channel disposed at the cold head side can be used to cool the cold head.
  • a control unit linked to the working state of the cold head may be provided. When the cold head is not working, the control unit opens the cooling liquid volatilization channel at the cold head side, and/or when the cold head is working, the cooling liquid volatilization channel at the cold head side is closed; thus the pre-cooling effect of volatilizing gas on the cold head is exploited, so volatilization of cooling liquid such as liquid helium is reduced.
  • Fig. 1 is a structural drawing of a cooling device for an MRI system according to an embodiment of the present invention.
  • the cooling device comprises: a cooling liquid tank 1, and a cooling liquid volatilization channel 4 located at the cold head 2 side of the MRI system.
  • the volatilization starting point of the cooling liquid volatilization channel 4 is the interior of the cooling liquid tank 1, while the volatilization end point of the cooling liquid volatilization channel 4 is the atmosphere or a gas recovery device. That is, the cooling liquid volatilization channel 4 is from cooling liquid in the cooling liquid tank 1 at a temperature of about 4 K, to the atmosphere at room temperature or a gas recovery device. Furthermore, the cold head 2 may be arranged outside or inside the cooling liquid tank 1.
  • the cooling device further comprises a control unit 3, for opening the cooling liquid volatilization channel 4 located at the cold head side when the cold head 2 is not working, and/or closing the cooling liquid volatilization channel 4 located at the cold head side when the cold head 2 is working .
  • the cooling liquid volatilization channel 4 may be arranged on the periphery of the cold head 2. Thus, when the cooling liquid volatilization channel 4 is opened, the cold gas which volatilizes out will have a pre-cooling effect on the cold head 2, so that volatilization of cooling liquid in the MRI system can be reduced.
  • the cooling liquid may specifically comprise liquid helium, liquid nitrogen, liquid oxygen or liquid hydrogen, etc.
  • the cooling liquid is liquid helium.
  • the cooling liquid tank 1 may comprise: a superconducting inner coil, and a superconducting outer coil surrounding the superconducting inner coil, with both the superconducting inner coil and the superconducting outer coil being immersed in cooling liquid. It is precisely because of the cooling effect of the cooling liquid that the superconducting inner coil and superconducting outer coil are able to maintain the superconducting state of the superconducting magnet, and together provide the main magnetic field for superconducting magnetic resonance.
  • the superconducting inner coil and superconducting outer coil together form the superconducting magnet for magnetic resonance .
  • the cooling device further comprises a cooling liquid volatilization channel 5 arranged at a service tower side.
  • the volatilization starting point of the cooling liquid volatilization channel 5 on the service tower side is cooling liquid in the cooling liquid tank 1, while the volatilization end point of the cooling liquid volatilization channel 5 on the service tower side is the atmosphere or a gas recovery device. That is, the cooling liquid volatilization channel 5 on the service tower side is from cooling liquid in the cooling liquid tank 1 at a temperature of about 4 K, to the atmosphere at room temperature or a gas recovery device.
  • the cooling liquid volatilization channel 5 on the service tower side is opened when the cold head 2 is not working, but does not discharge gas when the cold head 2 is working. Thus, when the cold head 2 is not working, volatilizing gas can still volatilize out through the cooling liquid volatilization channel 5 on the service tower side.
  • the volatilizing gas flows into the atmosphere from a cooling liquid volatilization channel 5 on the service tower side, and the cooling liquid volatilization channel 4 is closed.
  • the control unit 3 opens the cooling liquid volatilization channel 4, and due to the pre-cooling effect of the cold gas on the cold head 2, volatilization of cooling liquid such as liquid helium can be reduced.
  • the embodiments of the present invention establish functionality whereby the cessation of cold head 2 operation due to the supply of water/electricity being cut off, etc. is linked to the automatic opening of the cooling liquid volatilization channel 4. This enables the operational flexibility to be enhanced, with a reduction in the volatilization of liquid helium, so that a significant amount of liquid helium is saved.
  • the control unit 2 comprises a valve for opening or closing the cooling liquid volatilization channel 4.
  • the valve opens the cooling liquid volatilization channel 4; and/or when the gas supply pipe pressure of the compressor is greater than the gas return pipe pressure, the valve closes the cooling liquid volatilization channel 4.
  • the control unit 2 comprises a valve for opening or closing the cooling liquid volatilization channel.
  • the valve opens the cooling liquid volatilization channel 4; and/or when the electric motor of the cold head 2 is in an operational state, the valve closes the cooling liquid volatilization channel 4.
  • Fig. 2 is a drawing of the internal structure of the cooling liquid tank of the present invention.
  • the cooling liquid tank comprises a superconducting inner coil 11 and a superconducting outer coil 21.
  • the superconducting inner coil 11 is immersed in cooling liquid 33.
  • the superconducting outer coil 21, which surrounds the superconducting inner coil 11, is also immersed in the cooling liquid 33. It is precisely due to the cooling effect of the cooling liquid 33 that the superconducting inner coil 11 and superconducting outer coil 21 are able to maintain the superconducting state of the superconducting magnet, and together provide the main magnetic field for superconducting magnetic resonance.
  • the cooling liquid tank may also comprise a cooling liquid vessel 31 which contains the outer coil 21. Convection takes place between the cooling liquid vessel 31 and various elements in the cooling liquid tank, in order to supply the cooling liquid 33 in which the superconducting inner coil 11 and superconducting outer coil 21 are immersed.
  • Fig. 3 is a structural drawing of the control unit according to the present invention.
  • control unit 3 comprises a cold head operational state detection unit 6 and a valve 7; the valve 7 is disposed in the cooling liquid volatilization channel 4, and can open or close the cooling liquid volatilization channel 4.
  • the cold head operational state detection unit 6 is for detecting the operational state of the cold head 2.
  • the valve 7 opens, so that the cooling liquid volatilization channel 4 opens accordingly; and/or when the detection result is that the cold head is working, the valve 7 closes, so that the cooling liquid volatilization channel 4 closes accordingly.
  • the cold head operational state detection unit 6 is for comparing the gas return pipe pressure and gas supply pipe pressure of a compressor connected to the cold head 2. When the cold head operational state detection unit 6 determines that the gas supply pipe pressure is equal to the gas return pipe pressure, the detection result is that the cold head is not working, so the valve 7 opens, and the cooling liquid volatilization channel 4 opens accordingly; and/or when the cold head operational state detection unit 6 determines that the gas supply pipe pressure is greater than the gas return pipe pressure, the detection result is that the cold head is working, so the valve 7 closes, and the cooling liquid volatilization channel 4 closes accordingly.
  • the cold head operational state detection unit 6 is for detecting a state of an electric motor of the cold head 2.
  • the detection result is that the cold head is not working, so the valve 7 opens, and the cooling liquid volatilization channel 4 opens accordingly; and/or when the cold head operational state detection unit 6 determines that the electric motor of the cold head is in an operational state, the detection result is that the cold head is working, so the valve 7 closes, and the cooling liquid volatilization channel 4 closes accordingly.
  • Fig. 4 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and pneumatic drive in the present invention, wherein the cold head is working.
  • the valve 7 has one end connected to a gas supply pipe S of a compressor connected to the cold head, and another end connected to a gas return pipe R of the compressor.
  • the pressure of the gas supply pipe S e.g. 22 bar
  • the pressure of the gas return pipe R e.g. 8 bar
  • Fig. 5 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and pneumatic drive in the present invention, wherein the cold head is not working.
  • the valve 7 has one end connected to a gas supply pipe S of a compressor connected to the cold head, and another end connected to a gas return pipe R of the compressor.
  • the pressure of the gas supply pipe S is the same as the pressure of the gas return pipe R.
  • the valve 7 can move to the left under the action of an element such as a return spring provided in advance, so that gas is able to volatilize into the atmosphere in the direction shown by the arrow in the cooling liquid volatilization channel 4.
  • Fig. 6 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and a cold head electric motor in the present invention, wherein the cold head is working normally.
  • a control input end of the valve 7 is connected to an electric motor running state (MD) output end of the cold head.
  • MD electric motor running state
  • the valve 7 moves to the right, and closes the cooling liquid volatilization channel 4 accordingly, so that gas is unable to volatilize into the atmosphere through the cooling liquid volatilization channel 4.
  • Fig. 7 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and a cold head electric motor in the present invention, wherein the cold head is not working.
  • a control input end of the valve 7 is connected to an electric motor running state (MD) output end of the cold head.
  • MD electric motor running state
  • the valve 7 moves to the left, and opens the cooling liquid volatilization channel 4 accordingly, so that gas is able to volatilize into the atmosphere in the direction shown by the arrow in the cooling liquid volatilization channel 4.
  • the embodiments of the present invention can be applied in a superconducting MRI system.
  • the present invention also proposes a cooling method for an MRI system.
  • Fig. 8 is a flow chart of the cooling method for magnetic resonance according to the present invention.
  • the method comprises:
  • Step S801 a cooling liquid volatilization channel is provided on the cold head side.
  • Step S802 the cooling liquid volatilization channel on the cold head side is opened when the cold head is not working, and/or the cooling liquid volatilization channel on the cold head side is closed when the cold head is working.
  • the method comprises: providing a valve in the cooling liquid volatilization channel; detecting the operational state of the cold head, wherein the valve is opened when the detection result is that the cold head is not working; and/or the valve is closed when the detection result is that the cold head is working .
  • the method comprises: comparing a gas return pipe pressure and gas supply pipe pressure of a compressor connected to the cold head; wherein the detection result is that the cold head is not working when the gas supply pipe pressure is equal to the gas return pipe pressure; and/or the detection result is that the cold head is working when the gas supply pipe pressure of the compressor is greater than the gas return pipe pressure.
  • the method comprises: detecting a state of an electric motor of the cold head; wherein the detection result is that the cold head is not working when the electric motor of the cold head is in a shut-down state; and/or the detection result is that the cold head is working when the electric motor of the cold head is in an operational state.
  • the magnetic resonance cooling device in the embodiments of the present invention comprises: a cooling liquid tank; and a cooling liquid volatilization channel located on a cold head side of an MRI system, the volatilization starting point of the cooling liquid volatilization channel being the cooling liquid tank, and the volatilization end point being the atmosphere and/or a gas recovery device.
  • the cooling liquid volatilization channel provided on the cold head side can be used to cool the cold head.
  • the embodiments of the present invention may also provide a control unit linked to the operational state of the cold head.
  • the control unit opens the cooling liquid volatilization channel, and when the cold head is working, the cooling liquid volatilization channel on the cold head side is closed.
  • the pre-cooling effect of volatilizing gas on the cold head is exploited, reducing volatilization of cooling liquid, and saving a significant amount of cooling liquid such as liquid helium.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

Disclosed in the embodiments of the present invention are a cooling device and method for an MRI system, and an MRI system. The device comprises: a cooling liquid tank (1); and a cooling liquid volatilization channel (5) located on a cold head side of the MRI system, the volatilization starting point of the cooling liquid volatilization channel being the cooling liquid tank, and the volatilization end point being the atmosphere and/or a gas recovery device. The embodiments of the present invention can use the cooling liquid volatilization channel provided on the cold head side to cool the cold head (2), as well as using a control unit linked to the operational state of the cold head to control the opening or closing of the cooling liquid volatilization channel on the cold head side, thereby reducing volatilization of cooling liquid, and saving a significant amount of cooling liquid.

Description

Description
COOLING DEVICE AND METHOD FOR A MAGNETIC RESONANCE IMAGING SYSTEM
Technical field
The present invention relates to the technical field of medical apparatus, in particular to a cooling device and method for a magnetic resonance imaging system, and a magnetic resonance imaging system.
Background art
Magnetic resonance imaging (MRI) is an imaging technology involving biomagnetics and nuclear spin which has advanced rapidly with the development of computer technology, electronic circuit technology and superconductor technology. It uses a magnetic field and radio frequency (RF) pulses to induce nutation of precessing hydrogen nuclei (i.e. H+) in human tissue, to generate RF signals which are processed by a computer to form an image. If an object is placed in a magnetic field and irradiated by suitable electromagnetic waves to produce resonance therein, and electromagnetic waves released thereby are then analysed, it is possible to learn the positions and types of the atomic nuclei of which the object is composed. On this basis, a precise three-dimensional image of the interior of the object can be drawn. For instance, a moving picture of contiguous slices can be obtained by performing an MRI scan of the human brain, starting at the crown and continuing all the way to the base.
MRI technology may include superconducting MRI and permanent magnet MRI, where the classification is made according to the way in which the magnetic field is produced. In superconducting MRI, a stable magnetic field of high strength is produced using coils made of superconducting material. A cooling system plays an important role in ensuring normal operation of superconducting magnetic resonance, and the cold head is an important component of the magnetic resonance cooling system. The cold head and a compressor form a closed-circuit helium gas cycle, and are generally connected to each other by a flexible pressure pipe.
However, when the cold head stops working for some reason (e.g. during transportation, or a power cut, or due to the cooling system being damaged, etc.), a large amount of liquid helium will volatilize.
Content of the invention
The embodiments of the present invention propose a cooling device for an MRI system, wherein the amount of cooling liquid volatilized when the cold head is not working is reduced.
The embodiments of the present invention propose an MRI system, wherein the amount of cooling liquid volatilized when the cold head is not working is reduced.
The embodiments of the present invention propose a cooling method for an MRI system, whereby the amount of cooling liquid volatilized when the cold head is not working is reduced.
The technical solution of the embodiments of the present invention is as follows:
A cooling device for an MRI system, comprising: a cooling liquid tank; and a cooling liquid volatilization channel located on a cold head side of the MRI system, the volatilization starting point of the cooling liquid volatilization channel being the cooling liquid tank, and the volatilization end point being the atmosphere and/or a gas recovery device.
Also included is a control unit, for opening the cooling liquid volatilization channel on the cold head side when a cold head is not working, and/or closing the cooling liquid volatilization channel on the cold head side when the cold head is working.
The control unit comprises a cold head operational state detection unit and a valve, the valve being disposed in the cooling liquid volatilization channel; the cold head operational state detection unit is for detecting an operational state of the cold head; when the detection result is that the cold head is not working, the valve opens; and/or when the detection result is that the cold head is working, the valve closes.
The cold head operational state detection unit is for comparing a gas return pipe pressure and a gas supply pipe pressure of a compressor connected to the cold head, wherein the detection result is that the cold head is not working when the gas supply pipe pressure is equal to the gas return pipe pressure; and/or the detection result is that the cold head is working when the gas supply pipe pressure is greater than the gas return pipe pressure .
The cold head operational state detection unit is for detecting a state of an electric motor of the cold head; wherein the detection result is that the cold head is not working when an electric motor of the cold head is in a shut-down state; and/or the detection result is that the cold head is working when the electric motor of the cold head is in an operational state. An MRI system comprising any one of the cooling devices described above.
A cooling method for an MRI system, comprising: providing a cooling liquid volatilization channel on a cold head side; opening the cooling liquid volatilization channel on the cold head side when the cold head is not working, and/or closing the cooling liquid volatilization channel on the cold head side when the cold head is working.
The method comprises: providing a valve in the cooling liquid volatilization channel; detecting an operational state of the cold head, wherein the valve is opened when the detection result is that the cold head is not working; and/or the valve is closed when the detection result is that the cold head is working.
The method comprises: comparing a gas return pipe pressure and a gas supply pipe pressure of a compressor connected to the cold head; wherein the detection result is that the cold head is not working when the gas supply pipe pressure is equal to the gas return pipe pressure; and/or the detection result is that the cold head is working when the gas supply pipe pressure is greater than the gas return pipe pressure.
The method comprises: detecting a state of an electric motor of the cold head; wherein the detection result is that the cold head is not working when an electric motor of the cold head is in a shut¬ down state; and/or the detection result is that the cold head is working when the electric motor of the cold head is in an operational state.
It can be seen from the technical solution above that in the embodiments of the present invention, the cooling device for an MRI system comprises: a cooling liquid tank; and a cooling liquid volatilization channel located on a cold head side of the MRI system, the volatilization starting point of the cooling liquid volatilization channel being the cooling liquid tank, and the volatilization end point being the atmosphere and/or a gas recovery device. Clearly, once the embodiments of the present invention are applied, the cooling liquid volatilization channel provided on the cold head side can be used to cool the cold head. Furthermore, the embodiments of the present invention may also provide a control unit linked to the operational state of the cold head. When the cold head is not working, the control unit opens the cooling liquid volatilization channel, and when the cold head is working, the cooling liquid volatilization channel on the cold head side is closed. Thus the pre-cooling effect of volatilizing gas on the cold head is exploited, reducing volatilization of cooling liquid, and saving a significant amount of cooling liquid.
Description of the accompanying drawings
Fig. 1 is a structural drawing of the cooling device for an MRI system of the present invention.
Fig. 2 is a drawing of the internal structure of the cooling liquid tank of the present invention.
Fig. 3 is a structural drawing of the control unit according to the present invention.
Fig. 4 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and pneumatic drive in the present invention, wherein the cold head is working normally.
Fig. 5 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and pneumatic drive in the present invention, wherein the cold head is not working.
Fig. 6 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and a cold head electric motor in the present invention, wherein the cold head is working normally.
Fig. 7 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and a cold head electric motor in the present invention, wherein the cold head is not working.
Fig. 8 is a flow chart of the cooling method for an imaging system according to the present invention.
Particular embodiments
The present invention is explained in further detail below in conjunction with the accompanying drawings and embodiments, to clarify the technical solution and advantages thereof. It should be understood that the particular embodiments described here are merely intended to explain the present invention elaboratively, not to define the scope of protection thereof.
A superconducting magnetic resonance apparatus generally uses liquid helium as a cooling medium. Helium has the lowest boiling point of any substance currently known, with a boiling point of 4.2 K, and will not solidify at temperatures extremely close to absolute zero; therefore liquid helium can be used to obtain a low temperature close to absolute zero, to establish and maintain a superconducting environment for superconducting coils .
A superconducting magnet employs a multi-layer vacuum thermal isolation structure. However, due to various factors such as structural support, heat conduction to the superconducting magnet is difficult to prevent entirely, and liquid helium will evaporate to remove any heat that has been introduced, to maintain a low temperature of 4.2 K. To reduce evaporation of liquid helium, superconducting magnetic resonance systems are generally all equipped with a cooling system to supply cold.
The cooling system generally comprises three parts, namely a cold head, a helium compressor and a water cooling unit. The cold head consists of components such as an electric drive motor, a rotary valve, a gas distributor plate, a piston and a cylinder. The cooling system operates in the following manner: the electric drive motor controls the rotary valve to rotate on the gas distributor plate or some other gas distribution method is employed; the piston is controlled to compress and expand gas, to form an alternating cycle between a high-pressure gas chamber and a low-pressure gas chamber, and complete the process of sucking in high-pressure, low-temperature helium gas (e.g. at 20 Bar, 8°C) and discharging low-pressure, high- temperature helium gas (e.g. 8 Bar, 30°C), while at the same time carrying heat from within the cold head into the helium compressor .
The low-pressure helium gas returned is compressed in the helium compressor to increase the pressure thereof, undergoes heat exchange with cooling water supplied by the water cooling unit as well as oil filtering, and then high-pressure helium gas is conveyed back to the cold head, to set up a helium gas circulation process.
Thus the continuous operation of the cold head and the helium compressor enables cold to be supplied to a magnetic resonance magnet in an uninterrupted flow, to reduce the volatilization of liquid helium.
In the embodiments of the present invention, a cooling liquid volatilization channel disposed at the cold head side can be used to cool the cold head. Moreover, a control unit linked to the working state of the cold head may be provided. When the cold head is not working, the control unit opens the cooling liquid volatilization channel at the cold head side, and/or when the cold head is working, the cooling liquid volatilization channel at the cold head side is closed; thus the pre-cooling effect of volatilizing gas on the cold head is exploited, so volatilization of cooling liquid such as liquid helium is reduced.
Fig. 1 is a structural drawing of a cooling device for an MRI system according to an embodiment of the present invention.
As Fig. 1 shows, the cooling device comprises: a cooling liquid tank 1, and a cooling liquid volatilization channel 4 located at the cold head 2 side of the MRI system.
The volatilization starting point of the cooling liquid volatilization channel 4 is the interior of the cooling liquid tank 1, while the volatilization end point of the cooling liquid volatilization channel 4 is the atmosphere or a gas recovery device. That is, the cooling liquid volatilization channel 4 is from cooling liquid in the cooling liquid tank 1 at a temperature of about 4 K, to the atmosphere at room temperature or a gas recovery device. Furthermore, the cold head 2 may be arranged outside or inside the cooling liquid tank 1.
Preferably, the cooling device further comprises a control unit 3, for opening the cooling liquid volatilization channel 4 located at the cold head side when the cold head 2 is not working, and/or closing the cooling liquid volatilization channel 4 located at the cold head side when the cold head 2 is working .
The cooling liquid volatilization channel 4 may be arranged on the periphery of the cold head 2. Thus, when the cooling liquid volatilization channel 4 is opened, the cold gas which volatilizes out will have a pre-cooling effect on the cold head 2, so that volatilization of cooling liquid in the MRI system can be reduced.
For example, the cooling liquid may specifically comprise liquid helium, liquid nitrogen, liquid oxygen or liquid hydrogen, etc. Preferably, the cooling liquid is liquid helium.
Preferably, the cooling liquid tank 1 may comprise: a superconducting inner coil, and a superconducting outer coil surrounding the superconducting inner coil, with both the superconducting inner coil and the superconducting outer coil being immersed in cooling liquid. It is precisely because of the cooling effect of the cooling liquid that the superconducting inner coil and superconducting outer coil are able to maintain the superconducting state of the superconducting magnet, and together provide the main magnetic field for superconducting magnetic resonance. The superconducting inner coil and superconducting outer coil together form the superconducting magnet for magnetic resonance .
In one embodiment:
The cooling device further comprises a cooling liquid volatilization channel 5 arranged at a service tower side. The volatilization starting point of the cooling liquid volatilization channel 5 on the service tower side is cooling liquid in the cooling liquid tank 1, while the volatilization end point of the cooling liquid volatilization channel 5 on the service tower side is the atmosphere or a gas recovery device. That is, the cooling liquid volatilization channel 5 on the service tower side is from cooling liquid in the cooling liquid tank 1 at a temperature of about 4 K, to the atmosphere at room temperature or a gas recovery device.
The cooling liquid volatilization channel 5 on the service tower side is opened when the cold head 2 is not working, but does not discharge gas when the cold head 2 is working. Thus, when the cold head 2 is not working, volatilizing gas can still volatilize out through the cooling liquid volatilization channel 5 on the service tower side.
When the superconducting magnet formed by the superconducting inner coil and superconducting outer coil is in an ordinary state (e.g. rising field, quench, etc.), the volatilizing gas flows into the atmosphere from a cooling liquid volatilization channel 5 on the service tower side, and the cooling liquid volatilization channel 4 is closed.
When a situation where the cooling system stops working is encountered, e.g. due to the supply of water/electricity being cut off, the cold head 2 stops working; at this time, the control unit 3 opens the cooling liquid volatilization channel 4, and due to the pre-cooling effect of the cold gas on the cold head 2, volatilization of cooling liquid such as liquid helium can be reduced.
The embodiments of the present invention establish functionality whereby the cessation of cold head 2 operation due to the supply of water/electricity being cut off, etc. is linked to the automatic opening of the cooling liquid volatilization channel 4. This enables the operational flexibility to be enhanced, with a reduction in the volatilization of liquid helium, so that a significant amount of liquid helium is saved.
In one embodiment: The control unit 2 comprises a valve for opening or closing the cooling liquid volatilization channel 4. When the gas supply pipe pressure of a compressor connected to the cold head 2 is equal to a gas return pipe pressure, the valve opens the cooling liquid volatilization channel 4; and/or when the gas supply pipe pressure of the compressor is greater than the gas return pipe pressure, the valve closes the cooling liquid volatilization channel 4.
In one embodiment:
The control unit 2 comprises a valve for opening or closing the cooling liquid volatilization channel. When an electric motor of the cold head 2 is in a shut-down state, the valve opens the cooling liquid volatilization channel 4; and/or when the electric motor of the cold head 2 is in an operational state, the valve closes the cooling liquid volatilization channel 4.
Fig. 2 is a drawing of the internal structure of the cooling liquid tank of the present invention.
As Fig. 2 shows, the cooling liquid tank comprises a superconducting inner coil 11 and a superconducting outer coil 21.
The superconducting inner coil 11 is immersed in cooling liquid 33. The superconducting outer coil 21, which surrounds the superconducting inner coil 11, is also immersed in the cooling liquid 33. It is precisely due to the cooling effect of the cooling liquid 33 that the superconducting inner coil 11 and superconducting outer coil 21 are able to maintain the superconducting state of the superconducting magnet, and together provide the main magnetic field for superconducting magnetic resonance. The cooling liquid tank may also comprise a cooling liquid vessel 31 which contains the outer coil 21. Convection takes place between the cooling liquid vessel 31 and various elements in the cooling liquid tank, in order to supply the cooling liquid 33 in which the superconducting inner coil 11 and superconducting outer coil 21 are immersed.
Fig. 3 is a structural drawing of the control unit according to the present invention.
As Fig. 3 shows, the control unit 3 comprises a cold head operational state detection unit 6 and a valve 7; the valve 7 is disposed in the cooling liquid volatilization channel 4, and can open or close the cooling liquid volatilization channel 4.
The cold head operational state detection unit 6 is for detecting the operational state of the cold head 2. When the detection result is that the cold head is not working, the valve 7 opens, so that the cooling liquid volatilization channel 4 opens accordingly; and/or when the detection result is that the cold head is working, the valve 7 closes, so that the cooling liquid volatilization channel 4 closes accordingly.
In one embodiment:
The cold head operational state detection unit 6 is for comparing the gas return pipe pressure and gas supply pipe pressure of a compressor connected to the cold head 2. When the cold head operational state detection unit 6 determines that the gas supply pipe pressure is equal to the gas return pipe pressure, the detection result is that the cold head is not working, so the valve 7 opens, and the cooling liquid volatilization channel 4 opens accordingly; and/or when the cold head operational state detection unit 6 determines that the gas supply pipe pressure is greater than the gas return pipe pressure, the detection result is that the cold head is working, so the valve 7 closes, and the cooling liquid volatilization channel 4 closes accordingly.
In one embodiment:
The cold head operational state detection unit 6 is for detecting a state of an electric motor of the cold head 2. When the cold head operational state detection unit 6 determines that the electric motor of the cold head is in a shut-down state, the detection result is that the cold head is not working, so the valve 7 opens, and the cooling liquid volatilization channel 4 opens accordingly; and/or when the cold head operational state detection unit 6 determines that the electric motor of the cold head is in an operational state, the detection result is that the cold head is working, so the valve 7 closes, and the cooling liquid volatilization channel 4 closes accordingly.
Fig. 4 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and pneumatic drive in the present invention, wherein the cold head is working.
As Fig. 4 shows, the valve 7 has one end connected to a gas supply pipe S of a compressor connected to the cold head, and another end connected to a gas return pipe R of the compressor. When the cold head is working normally, the pressure of the gas supply pipe S (e.g. 22 bar) is greater than the pressure of the gas return pipe R (e.g. 8 bar) . Thus the pressure of the gas supply pipe S is able to push the valve 7 towards the right, and close the cooling liquid volatilization channel 4 accordingly, so that gas is unable to volatilize into the atmosphere through the cooling liquid volatilization channel 4.
Fig. 5 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and pneumatic drive in the present invention, wherein the cold head is not working.
As Fig. 5 shows, the valve 7 has one end connected to a gas supply pipe S of a compressor connected to the cold head, and another end connected to a gas return pipe R of the compressor. When the cold head is not working, the pressure of the gas supply pipe S is the same as the pressure of the gas return pipe R. Thus, the valve 7 can move to the left under the action of an element such as a return spring provided in advance, so that gas is able to volatilize into the atmosphere in the direction shown by the arrow in the cooling liquid volatilization channel 4.
Fig. 6 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and a cold head electric motor in the present invention, wherein the cold head is working normally.
As Fig. 6 shows, a control input end of the valve 7 is connected to an electric motor running state (MD) output end of the cold head. When the electric motor of the cold head is in a normal operating state, the valve 7 moves to the right, and closes the cooling liquid volatilization channel 4 accordingly, so that gas is unable to volatilize into the atmosphere through the cooling liquid volatilization channel 4.
Fig. 7 is a schematic diagram of a linkage structure of the valve of the cooling liquid volatilization channel and a cold head electric motor in the present invention, wherein the cold head is not working.
As Fig. 7 shows, a control input end of the valve 7 is connected to an electric motor running state (MD) output end of the cold head. When the electric motor of the cold head is in a non-operational state, the valve 7 moves to the left, and opens the cooling liquid volatilization channel 4 accordingly, so that gas is able to volatilize into the atmosphere in the direction shown by the arrow in the cooling liquid volatilization channel 4.
The embodiments of the present invention can be applied in a superconducting MRI system.
Based on the detailed description given above, the present invention also proposes a cooling method for an MRI system.
Fig. 8 is a flow chart of the cooling method for magnetic resonance according to the present invention.
As Fig. 8 shows, the method comprises:
Step S801: a cooling liquid volatilization channel is provided on the cold head side.
Step S802: the cooling liquid volatilization channel on the cold head side is opened when the cold head is not working, and/or the cooling liquid volatilization channel on the cold head side is closed when the cold head is working.
In one embodiment:
The method comprises: providing a valve in the cooling liquid volatilization channel; detecting the operational state of the cold head, wherein the valve is opened when the detection result is that the cold head is not working; and/or the valve is closed when the detection result is that the cold head is working .
In one embodiment:
The method comprises: comparing a gas return pipe pressure and gas supply pipe pressure of a compressor connected to the cold head; wherein the detection result is that the cold head is not working when the gas supply pipe pressure is equal to the gas return pipe pressure; and/or the detection result is that the cold head is working when the gas supply pipe pressure of the compressor is greater than the gas return pipe pressure.
In one embodiment:
The method comprises: detecting a state of an electric motor of the cold head; wherein the detection result is that the cold head is not working when the electric motor of the cold head is in a shut-down state; and/or the detection result is that the cold head is working when the electric motor of the cold head is in an operational state.
In summary, the magnetic resonance cooling device in the embodiments of the present invention comprises: a cooling liquid tank; and a cooling liquid volatilization channel located on a cold head side of an MRI system, the volatilization starting point of the cooling liquid volatilization channel being the cooling liquid tank, and the volatilization end point being the atmosphere and/or a gas recovery device. Clearly, once the embodiments of the present invention are applied, the cooling liquid volatilization channel provided on the cold head side can be used to cool the cold head. Furthermore, the embodiments of the present invention may also provide a control unit linked to the operational state of the cold head. When the cold head is not working, the control unit opens the cooling liquid volatilization channel, and when the cold head is working, the cooling liquid volatilization channel on the cold head side is closed. Thus the pre-cooling effect of volatilizing gas on the cold head is exploited, reducing volatilization of cooling liquid, and saving a significant amount of cooling liquid such as liquid helium.
The above embodiments are merely preferred embodiments of the present invention, which are not intended to define the scope of protection thereof. Any modifications, equivalent substitutions or improvements etc. made within the spirit and principles of the present invention should be included in the scope of protection thereof.

Claims

Claims
1. A cooling device for a magnetic resonance imaging (MRI) system, comprising:
a cooling liquid tank; and
a cooling liquid volatilization channel located on a cold head side of the MRI system, the volatilization starting point of the cooling liquid volatilization channel being the cooling liquid tank, and the volatilization end point being the atmosphere and/or a gas recovery device.
2. The cooling device as claimed in claim 1, characterized in that it further comprises a control unit,
for opening the cooling liquid volatilization channel on the cold head side when a cold head of the MRI system is not working, and/or closing the cooling liquid volatilization channel on the cold head side when the cold head is working.
3. The cooling device as claimed in claim 2, characterized in that the control unit comprises a cold head operational state detection unit and a valve, the valve being disposed in the cooling liquid volatilization channel;
the cold head operational state detection unit is for detecting an operational state of the cold head;
when the detection result is that the cold head is not working, the valve opens; and/or when the detection result is that the cold head is working, the valve closes.
4. The cooling device as claimed in claim 3, characterized in that
the cold head operational state detection unit is for comparing a gas return pipe pressure and a gas supply pipe pressure of a compressor connected to the cold head, wherein the detection result is that the cold head is not working when the gas supply pipe pressure is equal to the gas return pipe pressure; and/or the detection result is that the cold head is working when the gas supply pipe pressure is greater than the gas return pipe pressure.
5. The cooling device as claimed in claim 3, characterized in that
the cold head operational state detection unit is for detecting a state of an electric motor of the cold head; wherein the detection result is that the cold head is not working when an electric motor of the cold head is in a shut¬ down state; and/or the detection result is that the cold head is working when the electric motor of the cold head is in an operational state.
6. An MRI system, characterized in that it comprises the cooling device as claimed in any one of claims 1 - 5.
7. A cooling method for an MRI system, comprising:
providing a cooling liquid volatilization channel on a cold head side;
opening the cooling liquid volatilization channel on the cold head side when the cold head is not working, and/or closing the cooling liquid volatilization channel on the cold head side when the cold head is working.
8. The cooling method as claimed in claim 7, characterized in that the method comprises:
providing a valve in the cooling liquid volatilization channel ;
detecting an operational state of the cold head, wherein the valve is opened when the detection result is that the cold head is not working; and/or the valve is closed when the detection result is that the cold head is working.
9. The cooling method as claimed in claim 8, characterized in that the method comprises:
comparing a gas return pipe pressure and a gas supply pipe pressure of a compressor connected to the cold head; wherein the detection result is that the cold head is not working when the gas supply pipe pressure is equal to the gas return pipe pressure; and/or the detection result is that the cold head is working when the gas supply pipe pressure of the compressor is greater than the gas return pipe pressure.
10. The cooling method as claimed in claim 8, characterized in that the method comprises:
detecting a state of an electric motor of the cold head; wherein the detection result is that the cold head is not working when an electric motor of the cold head is in a shut¬ down state; and/or the detection result is that the cold head is working when the electric motor of the cold head is in an operational state.
PCT/EP2015/050902 2014-01-21 2015-01-19 Cooling device and method for a magnetic resonance imaging system Ceased WO2015110389A1 (en)

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