A low temperature cooling system for a magnetic resonance imaging probe

Abstract

The invention discloses a low temperature cooling system for a magnetic resonance imaging probe, comprising a probe sleeve, wherein the end surface of one end of the probe sleeve is concave to form a room temperature cavity, the other end of the probe sleeve is sealed and connected to a base shell, the base shell is sealed and connected to an infusion sleeve, a radio frequency coil support cylinder and a gradient coil support cylinder are sleeved on the room temperature cavity, a radio frequency coil is fixed on the radio frequency coil support cylinder, a gradient coil is fixed on the gradient coil support cylinder, and a dewar is respectively connected to a liquid nitrogen circulation inlet pipe and a liquid nitrogen circulation outlet pipe. The invention can effectively improve the signal-to-noise ratio of the received signal, and can ensure a high imaging quality while ensuring sealing.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear magnetic resonance instruments, and in particular to a low-temperature cooling system of a magnetic resonance imaging probe, which is suitable for nuclear magnetic resonance imaging. Background Art

[0002] In the field of magnetic resonance imaging, gradient coils are used to generate frequently switched gradient fields. Due to the large amount of current on the gradient coils, a large amount of heat is generated. The gradient coils need to switch the gradient fields frequently, and a changing magnetic field will be generated in the space around the gradient coils. This changing magnetic field will cause eddy currents inside the metal and also generate a large amount of heat. In addition, in order to improve the signal-to-noise ratio of the probe, we need to cool the RF wire coils at low temperatures to reduce thermal noise and improve sensitivity. Therefore, we need to cool the gradient coils and RF coils at the same time. Due to the requirements of the sealed structure, there are no objective conditions for natural heat dissipation and air cooling that can be relied on. It is necessary to consider encapsulating and fixing the gradient coils in non-metallic materials with good thermal conductivity, and using a circulating liquid nitrogen environment to continuously cool the coils to ensure that the coils are in a low temperature state.

[0003] According to the composition, structure, and thermodynamics laws of the present invention, the cooling gradient coil needs to be calculated according to the following heat exchange formula:

[0004]

[0005] Among them, Q is the theoretical cooling capacity required for heat exchange, α is a constant generally taken as 1.2, η is the heat exchange efficiency, A is the contact area between the gradient coil support tube and the dewar used to fix the gradient coil, and K is the empirical heat transfer coefficient, which is generally taken as a constant K = 350W / (m 2 .k), ΔT is the average temperature difference between the gradient coil and the RF coil and the cold pole, D is the inner diameter of the liquid nitrogen circulation inlet pipe / liquid nitrogen circulation outlet pipe, and L is the length of the cold chain used to transmit liquid nitrogen. Considering the design margin, L is generally longer than the actual length. According to the thermodynamic formula, the required transmission amount of liquid nitrogen per unit time can be calculated to meet the amount consumed by heat exchange.

[0006] In summary, it is necessary to design a low-temperature cooling system for the MRI probe, which uses the circulating coolant to remove the heat generated by the RF circuit. Due to the large temperature difference between the coolant and the environment, in order to ensure the cooling efficiency and facilitate the design of the sealing structure, the RF coil and the gradient coil are placed coaxially, and the coil temperature is reduced by contact with the liquid nitrogen dewar. While improving the signal-to-noise ratio of the RF coil, the vacuum structure can also achieve good thermal insulation to prevent the sample from being damaged by low temperature. Summary of the invention

[0007] The purpose of the present invention is to provide a low temperature cooling system for a magnetic resonance imaging probe in view of the above problems existing in the prior art. When the gradient coil and the radio frequency coil are working continuously, the heat generated by the radio frequency coil, the gradient coil, the radio frequency signal amplifier, etc. can be taken away in time, and the temperature of the radio frequency coil, the gradient coil, the radio frequency signal amplifier, etc. can also be reduced to improve the signal-to-noise ratio. The present invention can not only greatly improve the cooling effect, but also the processing of each component is simple and inexpensive. It is easy to disassemble and debug.

[0008] The above-mentioned purpose of the present invention is achieved by the following technical means:

[0009] A low-temperature cooling system for a magnetic resonance imaging probe comprises a probe sleeve, wherein an end surface of one end of the probe sleeve is concave to form a room temperature cavity, the other end of the probe sleeve is sealed and connected to a base shell, the base shell is sealed and connected to an infusion sleeve, a radio frequency coil support tube is located in the probe sleeve and sleeved outside the room temperature cavity, a gradient coil support tube is located in the probe sleeve and sleeved outside the radio frequency coil support tube, a radio frequency coil is fixed on the radio frequency coil support tube, a gradient coil is fixed on the gradient coil support tube, ends on the same side of the radio frequency coil support tube and the gradient coil support tube are fixed on the outside of a dewar, the dewar is respectively connected to one end of a liquid nitrogen circulation inlet pipe and one end of a liquid nitrogen circulation outlet pipe, and the other end of the liquid nitrogen circulation inlet pipe and the other end of the liquid nitrogen circulation outlet pipe are respectively connected to a liquid outlet pipe and a reflux pipe of the infusion sleeve.

[0010] As described above, a plurality of cooling copper disks are arranged in the probe sleeve, and the liquid nitrogen circulation inlet pipe sequentially penetrates each cooling copper disk and is connected to the cooling copper disk, and the liquid nitrogen circulation outlet pipe sequentially penetrates each cooling copper disk and is connected to the cooling copper disk.

[0011] A low temperature cooling system for a magnetic resonance imaging probe also includes a supporting copper tube, which passes through each cooling copper disk in sequence and is connected to the cooling copper disk.

[0012] As described above, the cooling copper disk is provided with an adjustable capacitor, a radio frequency signal amplifier and a radio frequency switching switch, the gradient coil support tube is provided with a lead through hole, the two ends of the radio frequency coil pass through the lead through hole and are connected to the adjustable capacitor to form a radio frequency transmitting and receiving circuit, one of the two wiring terminals of the radio frequency transmitting and receiving circuit is connected to the fixed end of the radio frequency switching switch, the two switching ends of the radio frequency switching switch are respectively connected to the radio frequency signal amplifier and the first pin of the SMA interface provided on the base shell, and the radio frequency signal amplifier is connected to the second pin of the SMA interface.

[0013] As mentioned above, the base shell is also provided with two aviation plugs, and a temperature sensor is provided on the cooling copper plate. One of the aviation plugs is connected to the temperature sensor, and the other aviation plug provides power for the RF signal amplifier and the RF switching switch.

[0014] A low-temperature cooling system for a magnetic resonance imaging probe also includes an epoxy resin support frame, the epoxy resin support frame includes a support cap and a support cap edge, the support cap extends into the probe sleeve, the support cap edge is fixed to the inner wall of the base shell, a plurality of through holes are opened on the support cap, a supporting copper tube, a liquid nitrogen circulation inlet tube, a liquid nitrogen circulation outlet tube, and a capacitor adjustment rod pass through the corresponding through holes, a tuning hole corresponding to the position of the capacitor adjustment rod is opened on the base shell, an external tuning rod passes through the tuning hole and is detachably connected to the capacitor adjustment rod, and a sealing ring is arranged between the external tuning rod and the tuning hole.

[0015] The end surface of the end of the capacitance adjustment rod as described above is provided with a polygonal embedding groove, one end of the external tuning rod is a polygonal end, and the polygonal end and the polygonal embedding groove are adaptively connected.

[0016] As mentioned above, the base housing is provided with a vacuum extraction interface.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention can miniaturize the gradient coil and embed it inside the probe sleeve. When used in conjunction with the radio frequency coil, it can effectively improve the signal-to-noise ratio of the received signal. At the same time, except for the coil, circuit board, circuit elements, and copper tube, all other materials are non-metallic materials, which can ensure high imaging quality while ensuring sealing. The materials used for the entire probe are relatively common, which can greatly save costs compared with foreign low-temperature probes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the side cross-sectional structure of the present invention;

[0020] Figure 2 It is a schematic diagram of the structure of the room temperature cavity;

[0021] Figure 3 It is a schematic diagram of the epoxy resin support frame structure;

[0022] Figure 4 This is a schematic diagram of the connection of the adjustable capacitor;

[0023] Figure 5 It is a schematic diagram of the adjustable resistor structure;

[0024] Figure 6 It is a schematic diagram of the cross-sectional structure of the probe base;

[0025] Figure 7 It is a schematic diagram of the structure of the external tuning rod;

[0026] Figure 8 Schematic diagram of the capacitance adjustment rod structure;

[0027] Fig. 9 It is a schematic diagram of the connection between the external adjustment rod and the capacitor adjustment rod;

[0028] Fig.10 It is a schematic diagram of the cooling copper plate structure;

[0029] Fig.11 is a schematic diagram of the structure of the radio frequency coil;

[0030] Fig.12 It is a schematic diagram of the structure of one side where the Dewar is connected to the gradient coil support cylinder and the radio frequency coil support cylinder;

[0031] Fig.13 It is a structural schematic diagram of one side of the connection between the Dewar and the liquid nitrogen circulation outlet pipe and the liquid nitrogen circulation inlet pipe;

[0032] Fig.14 It is a rear structural schematic diagram of the present invention.

[0033] In the figure: 1-Dewar; 2-gradient coil support tube; 3-RF coil support tube; 4-RF coil; 5-RF signal amplifier; 6-infusion cannula; 7-cooling copper plate; 8-room temperature chamber; 9-vacuum interface; 10-probe sleeve; 11-capacitor adjustment rod; 12-epoxy resin support frame; 13-aviation plug; 14-SMA interface; 15-gradient coil; 16-base shell; 17-liquid nitrogen circulation outlet pipe; 18-support copper tube; 19-RF switching switch; 20-base shell; 21-probe base; 22-liquid nitrogen circulation inlet pipe; 23-external tuning rod; 24-tuning hole; 25-adjustable capacitor; 26-support cap; 27-support cap edge; 28-cylinder body groove. DETAILED DESCRIPTION

[0034] In order to facilitate those skilled in the art to understand and implement the present invention, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the implementation examples described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0035] A low temperature cooling system for a magnetic resonance imaging probe comprises a probe sleeve 10, wherein an end surface of one end of the probe sleeve 10 is concave to form a room temperature cavity 8, the other end of the probe sleeve 10 is sealed and connected to a base shell 16, the base shell 16 is sealed and connected to an infusion sleeve 6, a radio frequency coil support tube 3 is located in the probe sleeve 10 and is sleeved outside the room temperature cavity 8, a gradient coil support tube 2 is located in the probe sleeve 10 and is sleeved outside the radio frequency coil support tube 3, a radio frequency coil 4 is fixed on the radio frequency coil support tube 3, a gradient coil 15 is fixed on the gradient coil support tube 2, the ends on the same side of the radio frequency coil support tube 3 and the gradient coil support tube 2 are both fixed on the outside of a dewar 1, the dewar 1 is respectively connected to one end of a liquid nitrogen circulation inlet pipe 22 and one end of a liquid nitrogen circulation outlet pipe 17, the other end of the liquid nitrogen circulation inlet pipe 22 and the other end of the liquid nitrogen circulation outlet pipe 17 are respectively connected to the liquid outlet pipe and the reflux pipe of the infusion sleeve 6.

[0036] A plurality of cooling copper disks 7 are arranged in the probe sleeve 10 , and the liquid nitrogen circulation inlet pipe 22 passes through each cooling copper disk 7 in sequence and is connected to the cooling copper disk 7 , and the liquid nitrogen circulation outlet pipe 17 passes through each cooling copper disk 7 in sequence and is connected to the cooling copper disk 7 .

[0037] A low temperature cooling system for a magnetic resonance imaging probe further comprises a supporting copper tube 18 , wherein the supporting copper tube 18 passes through each cooling copper disk 7 in sequence and is connected to the cooling copper disk 7 .

[0038] An adjustable capacitor, a radio frequency signal amplifier 5 and a radio frequency switching switch 19 are arranged on the cooling copper disk 7. A lead through hole is opened on the gradient coil support tube 2. Both ends of the radio frequency coil 4 pass through the lead through hole to connect with the adjustable capacitor to form a radio frequency transmitting and receiving circuit. One of the two wiring terminals of the radio frequency transmitting and receiving circuit is connected to the fixed end of the radio frequency switching switch 19. The two switching ends of the radio frequency switching switch 19 are respectively connected to the radio frequency signal amplifier 5 and the first pin of the SMA interface 14 arranged on the base shell 16, and the radio frequency signal amplifier 5 is connected to the second pin of the SMA interface 14.

[0039] The base housing 16 is also provided with two aviation plugs 13 , and a temperature sensor is provided on the cooling copper plate 7 , one of the aviation plugs 13 is connected to the temperature sensor, and the other aviation plug 13 provides power for the RF signal amplifier 5 and the RF switching switch 19 .

[0040] A low-temperature cooling system for a magnetic resonance imaging probe also includes an epoxy resin support frame 12, the epoxy resin support frame 12 includes a support cap and a support cap edge, the support cap extends into the probe sleeve 10, the support cap edge is fixed to the inner wall of the base shell 16, a plurality of through holes are opened on the support cap, a support copper tube 18, a liquid nitrogen circulation inlet pipe 22, a liquid nitrogen circulation outlet pipe 17, and a capacitor adjustment rod 11 pass through the corresponding through holes, a tuning hole 24 corresponding to the position of the capacitor adjustment rod 11 is opened on the base shell 16, an external tuning rod 23 passes through the tuning hole 24 and is detachably connected to the capacitor adjustment rod 11, and a sealing ring is arranged between the external tuning rod 23 and the tuning hole 24.

[0041] The end surface of the end of the capacitance adjustment rod 11 is provided with a polygonal embedding groove, and one end of the external tuning rod 23 is a polygonal end, and the polygonal end and the polygonal embedding groove are adaptively connected.

[0042] The base housing 16 is provided with a vacuum port 9 .

[0043] Dewar 1 is used to store liquid nitrogen and prevent it from volatilizing, so as to ensure that the liquid nitrogen can be effectively circulated inside; holes for fixing the gradient coil support tube 2 and the radio frequency coil support tube 3 are reserved on one side of the Dewar 1. The Dewar 1 is made of non-magnetic non-metallic material with good thermal conductivity (it can be made of relatively cheap ceramics or sapphire with better thermal conductivity), and is used to place and fix the gradient coil support tube 2 and the radio frequency coil support tube 3 for conducting heat; the probe sleeve 10 and the base shell 16 are both in a vacuum state, and there is a vacuum layer outside the Dewar 1 to isolate the heat exchange between the inside and outside of the Dewar.

[0044] The RF coil 4 is used to transmit RF pulses and receive MR signals; the RF coil 4 is fixed on the RF coil support tube 3 by multiple glass rods; one end of the RF coil support tube is fixed to the corresponding side hole on the Dewar 1 by a non-magnetic screw, and the RF coil 4 and the gradient coil 15 are heat-conducted through the RF coil support tube 3 and the gradient coil support tube 2 respectively, wherein the RF coil support tube 3 is sleeved on the room temperature cavity 8, and the gradient coil support tube 2 is slightly larger than the outer diameter of the RF coil 4 and sleeved on the outside of the RF coil 4, and one end is also fixed to the corresponding side hole of the Dewar 1 by a non-magnetic screw; the liquid nitrogen circulation inlet pipe 22 and the liquid nitrogen circulation outlet pipe 17 are connected to the other side of the Dewar 1 for cooling circulation.

[0045] The radio frequency signal amplifier 5 adopts a low temperature low noise amplifier and is used to amplify the MR signal received by the radio frequency coil 4;

[0046] The liquid nitrogen circulation inlet pipe 22 and the liquid nitrogen circulation outlet pipe 17 are used to connect the Dewar 1 and the infusion sleeve 6 outside the probe. A radio frequency transmitting and receiving circuit consisting of a radio frequency coil 4 and an adjustable capacitor 25 is fixed on the cooling copper disk 7. The radio frequency transmitting and receiving circuit is an RLC resonant circuit, wherein the adjustable capacitor 25 is arranged on a hole reserved on the cooling copper disk 7. The radio frequency coil 4 and the cooling copper disk 7 are connected by flying wires. Heat exchange is performed between the radio frequency signal amplifier 5 and the cooling copper disk 7 cooled by liquid nitrogen to reduce the thermal noise coefficient of the radio frequency signal amplifier 5.

[0047] The cooling copper plate 7 adopts a plate-like design, and holes are reserved on the surface for fixing the adjustable capacitor 25, the RF signal amplifier 5 and the RF switching switch 19, and holes are reserved for the liquid nitrogen circulation inlet pipe 22 and the liquid nitrogen circulation outlet pipe 17 to pass through and connect, and holes are reserved for the capacitance adjustment rod 11 of the adjustable capacitor 25 to pass through, and holes are reserved for the cables to pass through; the shell of the RF signal amplifier 5 is a metal shell with excellent thermal conductivity, and the RF signal amplifier 5 is fixed to the cooling copper plate 7 by non-magnetic screws to facilitate cooling, and the cables connected to the RF coil 4 and the gradient coil 15 pass through the holes on the cooling copper plate 7.

[0048] The room temperature chamber 8 is used for placing samples and maintaining the vital signs of experimental animals. A heating plate is placed in the room temperature chamber 8 to heat the room temperature and ensure that the temperature of the room temperature chamber is not too low.

[0049] The vacuum interface 9 is used to extract the gas in the probe sleeve 10 and the base shell 16. The interface model is KF25, which is fixed to the base shell 16 and connected to the vacuum pump through a clamp and a ball valve to extract the air in the probe sleeve 10 and the base shell 16. The air pressure value of the vacuum layer is about 10 -5 pa, thereby reducing heat loss caused by internal and external heat exchange.

[0050] The probe sleeve 10 uses a non-metallic material with low thermal conductivity (for example, high-performance plastic (polyetheretherketone) PEEK, or plastic polyimide (PI) with better performance). The probe sleeve 10 is connected and fixed to the base shell 16 by screws. An O-ring is arranged between the probe sleeve 10 and the base shell 16, and the probe sleeve 10 and the base shell 16 form a sealing structure.

[0051] The capacitor adjustment rod 11 has an outer diameter of 6 mm and is spliced ​​in multiple sections. Each section is connected by non-magnetic fastening screws. The cooling copper plate 7 is reserved with a hole for the capacitor adjustment rod 11 to pass through. The hole diameter is slightly larger than the outer diameter of the capacitor adjustment rod 11. The capacitor adjustment rod 11 passes through the corresponding hole on the cooling copper plate 7. One end of the capacitor adjustment rod 11 is reserved for an interface for docking with the adjustable capacitor 25. The capacitor adjustment rod 11 and the adjustable capacitor 25 are fixed together with fastening screws. When the capacitor adjustment rod 11 rotates, the adjustable capacitor 25 can be driven to rotate; the other end of the capacitor adjustment rod 11 is reserved for the outer The interface for docking the external tuning rod 23 is similar to the structure of a hexagonal wrench. During docking, the external tuning rod 23 is inserted through the tuning hole 24 reserved in the base shell 16. A sealing ring is arranged between the external tuning rod 23 and the tuning hole 24. Four sealing O-grooves are reserved on the external tuning rod 23. During assembly, the silicone O-ring is clamped in the sealing O-groove. The outer diameter of the silicone O-ring is slightly larger than the inner diameter of the tuning hole 24. Therefore, the sealing effect between the external tuning rod 23 and the base shell 16 is achieved by compressing the tuning hole 24. At the same time, the rotation of the external tuning rod 23 can be maintained, which is convenient for matching and tuning.

[0052] The epoxy resin support frame 12 is a non-metallic material with poor thermal conductivity. The epoxy resin support frame 12 includes a support cap and a support cap edge. The support cap extends into the probe sleeve 10. The support cap edge is fixed to the inner wall of the base shell 16 by a non-magnetic screw. A plurality of through holes are provided on the support cap. The support copper tube 18, the liquid nitrogen circulation inlet pipe 22, the liquid nitrogen circulation outlet pipe 17, and the capacitor adjustment rod 11 pass through the corresponding through holes. The base shell 16 is provided with a tuning hole 2 corresponding to the position of the capacitor adjustment rod 11. 4. The external tuning rod 23 passes through the tuning hole 24 and is detachably connected to the capacitance adjustment rod 11. A sealing ring is provided between the external tuning rod 23 and the tuning hole 24. The entire cooling link (including the liquid nitrogen circulation outlet pipe 17, the liquid nitrogen circulation inlet pipe 22, the cooling copper plate 7, and the supporting copper tube 18) is suspended by the epoxy resin support frame 12. The epoxy resin support frame 12 does not contact the probe sleeve 10, and only contacts the base shell 16 through the supporting cap brim, so as to minimize contact to achieve the purpose of reducing heat exchange.

[0053] Dewar 1, the interior of Dewar 1 uses a U-shaped structure, such as Figure 1 As shown, the inflow channel and the outflow channel at both ends of the U-shaped structure in the dewar 1 are respectively welded to the liquid nitrogen circulation inlet pipe 22 and the liquid nitrogen circulation outlet pipe 17, so that the liquid nitrogen can circulate inside, and the continuous circulation of the internal liquid nitrogen provides a low-temperature environment. The liquid nitrogen circulation inlet pipe 22 and the liquid nitrogen circulation outlet pipe 17 are both made of copper tubes. The inflow channel and the outflow channel are respectively welded to the liquid nitrogen circulation inlet pipe 22 and the liquid nitrogen circulation outlet pipe 17 to prevent liquid nitrogen penetration; the liquid nitrogen circulation inlet pipe 22 and the liquid nitrogen circulation outlet pipe 17 are respectively connected to the liquid outlet pipe and the reflux pipe of the infusion sleeve 6, which are used to connect the self-pressurized liquid nitrogen supply system to replenish the liquid nitrogen in the dewar; ensure that the liquid nitrogen can cool other electronic components during circulation.

[0054] The cooling link comprises a liquid nitrogen circulation outlet pipe 17, a liquid nitrogen circulation inlet pipe 22, a cooling copper plate 7, and a supporting copper tube 18. The liquid nitrogen circulation outlet pipe 17, the liquid nitrogen circulation inlet pipe 22, and the supporting copper tube 18 are arranged in parallel. In this embodiment, there are three cooling copper plates 7, which are arranged in parallel. The liquid nitrogen circulation outlet pipe 17 and the liquid nitrogen circulation inlet pipe 22 pass through corresponding reserved holes on the cooling copper plate 7 and are welded to the cooling copper plate 7. The parallel arrangement allows the coolant of the entire cooling link to evenly take away the heat generated by the active devices (RF switching switch 19, RF signal amplifier 5, etc.) placed on the cooling copper plate (7). In addition, the cooling link in the invention example is simple to install, low in cost, and reduces the assembly process time. Since the gradient coil support tube 2 and the RF coil support tube 3 are separated from the cooling copper plate 7 by the dewar 1, the installation of the cooling link has no effect on the gradient coil support tube 2 and the RF coil support tube 3.

[0055] The shell of the infusion sleeve 6 is sealed and welded on the sleeve mounting hole corresponding to the base shell 16. The liquid outlet pipe and the return pipe of the infusion sleeve 6 extend into the base shell 16 and are respectively connected to the liquid nitrogen circulation inlet pipe 22 and the liquid nitrogen circulation outlet pipe 17. The infusion sleeve 6 has an outer sleeve and an inner pipe, and the outer sleeve is sleeved on the outside of the inner pipe. The inner pipe constitutes the liquid outlet pipe, and the channel between the inner wall of the outer sleeve and the outer wall of the inner pipe constitutes the return pipe. The liquid outlet pipe and the return pipe are both connected to the self-pressurized liquid nitrogen tank by a threaded sealed connection. After the connection is completed, the liquid nitrogen inlet and outlet are controlled by the air pressure valve of the self-pressurized liquid nitrogen tank, which can ensure effective liquid nitrogen transmission and good thermal insulation. The temperature at the connection between the liquid outlet pipe of the infusion sleeve 6 and the liquid nitrogen circulation inlet pipe 22 is not too low to freeze.

[0056] Preferably, the gradient coil support tube 2 and the radio frequency coil support tube 3 are made of ceramic or sapphire, so that the dewar 1 can cool the temperature of the gradient coil support tube 2 and the radio frequency coil support tube 3 quickly. The ends of the gradient coil support tube 2 and the radio frequency coil support tube 3 are provided with a connecting base, and the connecting base is punched with a threaded hole, which is fixed to the reserved hole on the left side of the dewar 1 by a non-magnetic screw to conduct heat;

[0057] Preferably, the outer wall of the gradient coil support tube 2 is provided with a gradient coil placement groove, in which the gradient coil 15 is embedded. The gradient coil 15 and the RF coil 4 are placed coaxially to ensure the uniformity of the coil magnetic field.

[0058] Preferably, the liquid nitrogen circulation outlet pipe 17 and the liquid nitrogen circulation inlet pipe are both made of copper pipes.

[0059] Preferably, an isolating member is provided between the circuit board carrying the RF switching switch 19 , the RF signal amplifier 5 , and the adjustable capacitor 25 and the cooling copper plate 7 , and the material of the isolating member is polyimide.

[0060] In order to minimize the consumption of liquid nitrogen and to ensure a better cooling effect, the probe sleeve 10 and the base shell 16 are evacuated. To ensure the vacuum degree, some aluminates can be placed inside the probe sleeve 10 and the base shell 16 to absorb diffused moisture and air molecules.

[0061] Preferably, the temperature sensor may be PT1000.

[0062] As an implementable method, the end of the gradient coil support tube 2 is provided with an end fixing edge, and the end fixing edge is fixed to the side of the dewar 1 by a non-magnetic screw. An annular cylinder embedding groove is provided on the same side of the dewar 1, and a cylinder end ring is provided at the end of the RF coil support tube 3. The cylinder end ring is a heat-expandable plastic. At room temperature, the cylinder end ring is clamped in the annular cylinder embedding groove. After cooling, the cylinder end ring shrinks and tightens in the cylinder embedding groove. This method can avoid glue bonding and reduce the generation of background signals.

[0063] It should be noted that the specific embodiments described in the present invention are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the attached claims.

Claims

1. A low temperature cooling system for a magnetic resonance imaging probe, comprising a probe sleeve (10), characterized in that: The end surface of one end of the probe sleeve (10) is concave to form a room temperature cavity (8); the other end of the probe sleeve (10) is sealedly connected to the base shell (16); the base shell (16) is sealedly connected to the infusion sleeve (6); the radio frequency coil support tube (3) is located in the probe sleeve (10) and is sleeved outside the room temperature cavity (8); the gradient coil support tube (2) is located in the probe sleeve (10) and is sleeved outside the radio frequency coil support tube (3); and the radio frequency coil support tube (3) is fixed to the probe sleeve (10). A radio frequency coil (4) is provided, a gradient coil (15) is fixed on a gradient coil support tube (2), the ends of the radio frequency coil support tube (3) and the gradient coil support tube (2) on the same side are fixed on the outside of a dewar (1), the dewar (1) is respectively connected to one end of a liquid nitrogen circulation inlet tube (22) and one end of a liquid nitrogen circulation outlet tube (17), the other end of the liquid nitrogen circulation inlet tube (22) and the other end of the liquid nitrogen circulation outlet tube (17) are respectively connected to the liquid outlet tube and the return tube of the infusion cannula (6), A plurality of cooling copper disks (7) are arranged in the probe sleeve (10), a liquid nitrogen circulation inlet pipe (22) sequentially passes through each cooling copper disk (7) and is connected to the cooling copper disk (7), and a liquid nitrogen circulation outlet pipe (17) sequentially passes through each cooling copper disk (7) and is connected to the cooling copper disk (7). It also includes a supporting copper tube (18), which passes through each cooling copper plate (7) in sequence and is connected to the cooling copper plate (7). The cooling copper disk (7) is provided with an adjustable capacitor, a radio frequency signal amplifier (5) and a radio frequency switching switch (19); a lead through hole is provided on the gradient coil support tube (2); two ends of the radio frequency coil (4) pass through the lead through hole to be connected to the adjustable capacitor to form a radio frequency transmitting and receiving circuit; one of the two wiring terminals of the radio frequency transmitting and receiving circuit is connected to a fixed end of the radio frequency switching switch (19); the two switching ends of the radio frequency switching switch (19) are respectively connected to the radio frequency signal amplifier (5) and a first pin of an SMA interface (14) provided on the base housing (16); and the radio frequency signal amplifier (5) is connected to a second pin of the SMA interface (14).

2. A low temperature cooling system for a magnetic resonance imaging probe according to claim 1, characterized in that: The base housing (16) is also provided with two aviation plugs (13), and a temperature sensor is provided on the cooling copper plate (7), one of the aviation plugs (13) is connected to the temperature sensor, and the other aviation plug (13) provides power to the radio frequency signal amplifier (5) and the radio frequency switching switch (19).

3. A low temperature cooling system for a magnetic resonance imaging probe according to claim 2, characterized in that: The invention also comprises an epoxy resin support frame (12), the epoxy resin support frame (12) comprising a support cap and a support cap edge, the support cap extends into the probe sleeve (10), the support cap edge is fixed to the inner wall of the base shell (16), a plurality of through holes are formed on the support cap, a support copper tube (18), a liquid nitrogen circulation inlet tube (22), a liquid nitrogen circulation outlet tube (17), and a capacitance adjustment rod (11) pass through corresponding through holes, a tuning hole (24) corresponding to the position of the capacitance adjustment rod (11) is formed on the base shell (16), an external tuning rod (23) passes through the tuning hole (24) and is detachably connected to the capacitance adjustment rod (11), and a sealing ring is provided between the external tuning rod (23) and the tuning hole (24).

4. The low temperature cooling system of a magnetic resonance imaging probe according to claim 3, characterized in that: The end surface of the end of the capacitance adjustment rod (11) is provided with a polygonal embedding groove, one end of the external tuning rod (23) is a polygonal end, and the polygonal end and the polygonal embedding groove are adaptively connected.

5. The low temperature cooling system of a magnetic resonance imaging probe according to claim 1, characterized in that: The base shell (16) is provided with a vacuum extraction interface (9).

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