WO2022110136A1

WO2022110136A1 - Cooling system for radio frequency coil, and magnetic resonance imaging device

Info

Publication number: WO2022110136A1
Application number: PCT/CN2020/132744
Authority: WO
Inventors: 郑海荣; 李烨; 李旭; 刘新; 李楠; 陈巧燕; 杜凤; 李柔; 罗超
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2020-11-27
Filing date: 2020-11-30
Publication date: 2022-06-02
Also published as: CN112433188A

Abstract

A cooling system for a radio frequency coil (100), and a magnetic resonance imaging device. The cooling system comprises: a vacuum chamber (10) comprising a base (12) and a vacuum upper cover (11), wherein the vacuum upper cover (11) covers the base (12) to form a sealed space; a semiconductor refrigeration unit (20) disposed in the vacuum chamber (10), wherein a heat dissipation end of the semiconductor refrigeration unit (20) is in contact with the base (12), and a cooling end of the semiconductor refrigeration unit (20) is used to support the radio frequency coil (100); and a cooling unit (30) connected to the base (12), and used to absorb heat from the heat dissipation end of the semiconductor refrigeration unit (20). The magnetic resonance imaging device comprises the radio frequency coil (100) and the cooling system for the radio frequency coil (100). The radio frequency coil (100) is disposed on the cooling end of the semiconductor refrigeration unit (20), and is cooled by means of a semiconductor refrigeration technique, thereby improving safety, significantly reducing the volume of the cooling system, achieving continuous, uninterrupted cooling, and implementing cooling temperature control.

Description

Cooling systems for radio frequency coils, magnetic resonance imaging equipment

technical field

The invention belongs to the technical field of magnetic resonance imaging, and in particular relates to a cooling system for a radio frequency coil and a magnetic resonance imaging device.

Background technique

Magnetic resonance imaging is a medical imaging method that is harmless to the body, and it is one of the hot areas of research in the field of biomedicine. Magnetic resonance imaging has great advantages and potential in disease diagnosis, precise localization and disease prevention. The magnetic resonance imaging performance is mainly determined by the magnetic field strength of the main magnetic field and the receiving performance of the radio frequency coil. However, the increase of the strength of the main magnetic field will also bring about the problems of increasing the non-uniformity of the magnetic field, increasing the instability of the magnet and increasing the manufacturing cost of the magnet. Therefore, improving the performance of RF coils is considered as an economical and feasible method.

The imaging performance of an RF coil can be characterized by the signal-to-noise ratio (SNR). According to the equivalent approximate calculation formula of the signal-to-noise ratio of the radio frequency coil, reducing the temperature and equivalent resistance of the radio frequency coil can improve the signal-to-noise ratio of the radio frequency coil. Therefore, researchers use cryogenic liquid or gas to cryogenically freeze the radio frequency coil to achieve the purpose of improving the radio frequency coil. For example, the small animal imaging radio frequency coil CryoProbe ^TM of Bruker Company uses the refrigerator as the cold source and helium as the refrigerant, which can cool the coil to 30K and realize the coil-to-sample distance of 2mm. Using this product to image mouse brain ¹ H in the ultra-high field of 9.4T/15.2T/18T, the signal-to-noise ratio of the normal temperature coil with the same parameters is increased by 2.7 times/1.9 times/1.8 times. On the 9.4T magnetic resonance system of Heidelberg University, the copper radio frequency coil was cooled to 77K, and ^39K imaging was performed on the mouse brain, which improved the signal-to-noise ratio by 2.7 times compared with the same parameter coil.

The existing cryogenic refrigeration coil technologies all use cryogenic liquids and gases, and the design of the cryogenic system is relatively complicated and the manufacturing cost is high. At the same time, cryogenic liquids and gases have higher requirements on the thermal insulation and mechanical properties of the low-temperature system. If the designed strength and thermal insulation performance are unreasonable, the risk of low-temperature frostbite and explosion is likely to occur. The consumption of low-temperature liquid needs to be replenished in time, and manual duty is required, which requires the professionalism of operators.

SUMMARY OF THE INVENTION

(1) Technical problem to be solved by the present invention

The technical problem solved by the present invention is: how to simplify the complex structure of the cooling system of the radio frequency coil.

(2) Technical scheme adopted in the present invention

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A cooling system for a radio frequency coil, the cooling system comprising:

The vacuum chamber includes a base and a vacuum upper cover, and the vacuum upper cover is covered with the base to form a closed space;

a semiconductor refrigeration unit, disposed in the vacuum cavity, the heat dissipation end of the semiconductor refrigeration unit is in contact with the base, and the cooling end of the semiconductor refrigeration unit is used to carry the radio frequency coil;

The cooling unit is connected to the base and is used for absorbing heat from the heat dissipation end of the semiconductor refrigeration unit.

Optionally, the semiconductor refrigeration unit includes a plurality of stacked semiconductor refrigeration sheets, the cooling end of one of the two adjacent semiconductor refrigeration sheets is in contact with the heat dissipation end of the other semiconductor refrigeration sheet, and the topmost The cooling end of the semiconductor refrigeration sheet carries the radio frequency coil, and the heat dissipation end of the semiconductor refrigeration sheet at the bottom is connected to the base.

Optionally, the power of each of the semiconductor refrigeration chips increases along the direction from the topmost layer to the bottommost layer.

Optionally, non-magnetic non-metallic heat-conducting sheets are used for the heat-transfer components of each of the semiconductor refrigeration sheets to replace copper heat-conducting sheets.

Optionally, the power transmission wires of each of the semiconductor refrigeration chips are metal-shielded four-stranded wires to prevent current signal interference.

Optionally, the side wall of the vacuum upper cover is provided with a socket, the cooling system further includes a current lead and a plug, the plug is sealed with the socket, and the two ends of the current lead are respectively electrically connected to The semiconductor refrigeration unit and the plug, one end of the plug located on the outer side of the vacuum upper cover is used for connecting to a matching circuit.

Optionally, the cooling system further includes a radio frequency coil signal wire, two ends of the radio frequency coil signal wire are electrically connected to the radio frequency coil and the plug, respectively, and the shielding layer of the signal wire is grounded.

Optionally, the cooling unit includes a cooling water pipe and a cooling water circulation module that communicate with each other, an accommodation groove is opened inside the base, and the cooling water pipe communicates with the accommodation groove to transport cooling water into the accommodation groove .

Optionally, the cooling system further includes a thermometer, and the thermometer is arranged on the cooling end of the semiconductor refrigeration unit.

Optionally, the inner surface of the vacuum upper cover is coated with polyurethane low temperature glue.

Optionally, the material of the vacuum upper cover is a non-magnetic non-metallic material.

The present application also discloses a magnetic resonance imaging device, comprising a radio frequency coil and any one of the above cooling systems for the radio frequency coil, wherein the radio frequency coil is disposed on the cooling end of the semiconductor refrigeration unit.

(3) Beneficial effects

The invention discloses a cooling system and a magnetic resonance imaging device for a radio frequency coil. Compared with the prior art, the invention has the following advantages and beneficial effects:

The use of semiconductor refrigeration to cool the RF coil can improve safety, greatly reduce the volume of the cooling system, achieve continuous and uninterrupted cooling and control the cooling temperature.

Description of drawings

FIG. 1 is a schematic structural diagram of a cooling system for a radio frequency coil according to Embodiment 1 of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Before describing the various embodiments of the present application in detail, first briefly describe the inventive concept of the present application: in the existing cryogenic coil technology, the use of cryogenic liquid or gas to freeze the coil will result in a complex structure of the cryogenic system, high manufacturing cost, Technical issues such as poor security. In the present application, a semiconductor refrigeration unit is arranged in the vacuum cavity to form a low temperature environment, and the heat of the semiconductor refrigeration unit is discharged by the cooling unit, so as to form a cooling system with simple structure and high safety performance, and realize the cooling of the radio frequency coil.

As shown in FIG. 1 , the cooling system for a radio frequency coil of this embodiment includes a vacuum chamber 10 , a semiconductor refrigeration unit 20 and a cooling unit 30 . The vacuum chamber 10 includes a base 11 and a vacuum upper cover 12. The vacuum upper cover 12 is covered with the base 11 to form a closed space. The semiconductor refrigeration unit 20 is arranged in the vacuum chamber 10. The heat dissipation end of the semiconductor refrigeration unit 20 is connected to the base. 11 contacts, and the cooling end of the semiconductor refrigeration unit 20 is used to carry the radio frequency coil 100 . The cooling unit 30 is connected to the base 12 for absorbing the heat of the heat dissipation end of the semiconductor refrigeration unit 20 .

As a preferred embodiment, since the radio frequency coil 100 is used in a high magnetic field, in order to prevent the influence of the metal material on the magnetic field and the shielding of the radio frequency signal, the material of the vacuum upper cover 12 is a glass fiber ring with high low temperature strength, simple production and low price Oxygen resin material (G10). Of course, in other embodiments, the vacuum upper cover 12 may also use other types of non-magnetic non-metallic materials. The wall thickness of the front, rear, left and right sides of the vacuum upper cover 12 is 10mm, which not only meets the strength requirements, but also improves the air tightness. Since the closer the distance between the radio frequency coil 100 and the measured object, the higher the coil imaging signal-to-noise ratio, the thickness of the top of the vacuum upper cover 11 is designed to be 2 mm.

Further, the inner surface of the vacuum upper cover 12 is coated with a polyurethane low-temperature glue of about 0.5 mm. The polyurethane low-temperature glue has excellent air tightness and can effectively prevent air leakage of the vacuum upper cover 12 . At the same time, due to the low thermal conductivity of the polyurethane low-temperature adhesive, the polyurethane low-temperature adhesive will also play a role of heat insulation at the bottom. Wherein, the side of the vacuum upper cover 12 is provided with a vacuum chamber suction port 11a, which is used for vacuuming the system.

As a preferred embodiment, the semiconductor refrigeration unit 20 includes a plurality of stacked semiconductor refrigeration sheets 21, and the cooling end of one of the two adjacent semiconductor refrigeration sheets is in contact with the heat dissipation end of the other semiconductor refrigeration sheet, wherein the topmost layer The cooling end of the semiconductor refrigeration sheet carries the radio frequency coil 100 , the cooling end of the bottom semiconductor refrigeration sheet is connected to the base 12 , and the number of the semiconductor refrigeration sheet 21 is determined according to the cooling temperature requirement. In order to offset the thermal power brought by the electric heating, the power of each refrigerating chip increases along the direction from the topmost layer to the bottommost layer. Exemplarily, the semiconductor refrigeration sheets are numbered from top to bottom as 1, 2, 3...n, respectively. In order to offset the thermal power brought by electric heating, the power of the semiconductor refrigeration sheets gradually increases as the number increases. The cooling end of the No. 1 semiconductor refrigeration piece is in contact with the radio frequency coil for heat exchange, the cooling end of the No. 1 semiconductor refrigeration piece is in contact with the cooling end of the No. 2 semiconductor refrigeration piece for heat exchange, and the two semiconductor refrigeration pieces pass through the thermal conductivity. Higher Stycast epoxy glues directly bond, and so on.

Further, the heat dissipation end of the bottommost semiconductor refrigeration sheet needs to be actively dissipated. As a preferred embodiment, the heat dissipation end of the bottommost semiconductor refrigeration sheet is connected to the base 12 through thermal conductive silicone grease, and the base 12 transfers the heat of the heat dissipation end to the cooling unit 30 to realize heat dissipation. As a preferred embodiment, the cooling unit 30 includes a cooling water pipe 31 and a cooling water circulation module 32 that communicate with each other, a receiving groove 12a is opened inside the base 12 , and the cooling water pipe 31 is connected to the receiving groove for cooling water. It is transported into the accommodating groove 12a to conduct the heat of the heat dissipation end of the bottommost semiconductor refrigeration sheet to the outside through cooling water, so as to prevent damage caused by the overheating of the bottommost semiconducting sheet.

As a preferred embodiment, the base 12 is made of two square discs with a side length of 200mm, the thickness of the lower disc is 10mm, a receiving groove 12a with a depth of 6mm and a side length of 160mm is opened in the middle, and a hole with a diameter of 5mm is opened on both sides. The cooling water hole is used for cooling water to dissipate heat from the cooling end of the semiconductor refrigeration sheet.

In order to realize the control of the radio frequency coil 100 and the semiconductor refrigeration unit 20 , the cooling system of this embodiment further includes the cooling system further includes a plug 40 , a current lead 50 and a radio frequency coil lead 60 . The plug 40 is a non-magnetic aviation plug, a socket is provided on the side wall of the vacuum upper cover 11, the plug 40 is sealedly connected to the socket, and both ends of the current lead 50 are electrically connected to the semiconductor refrigeration unit respectively. 20 and the plug 40 , one end of the plug 40 located outside the vacuum upper cover 11 is used to connect to the matching circuit 70 , so as to supply power to the semiconductor refrigeration unit 20 . Both ends of the radio frequency coil lead 60 are electrically connected to the radio frequency coil 100 and the plug 40 respectively. Since the wire resistance of the radio frequency coil 100 decreases at low temperature, the change in capacitance value will cause the coil matching to change. A matching circuit 70 is provided outside 10, and the resistance of the radio frequency coil is re-matched to 50Ω at low temperature.

Further, the cooling system further includes a thermometer 81 and a thermometer lead 82 , and the thermometer 81 is disposed on the cooling end of the semiconductor refrigeration unit 21 . Exemplarily, the thermometer 81 is attached to the cooling end of the topmost semiconductor refrigeration sheet, and the two ends of the thermometer lead 82 are respectively connected to the thermometer 81 and the plug 40, so that the temperature of the radio frequency coil 100 can be monitored in real time. The above-mentioned current lead 50 , radio frequency coil lead 60 , and thermometer lead 82 are all twisted-pair copper wires to prevent electromagnetic interference.

The second embodiment also discloses a magnetic resonance imaging device, including a radio frequency coil 100 and any of the above cooling systems for radio frequency coils, the radio frequency coil 100 is disposed on the cooling end of the semiconductor refrigeration unit 20, and the vacuum upper cover is 11 is used to carry the measured object 200 . In order to facilitate sufficient contact between the radio frequency coil 100 and the semiconductor cooling chip 20 , the radio frequency coil 100 is made of a patch type or thin PCB board wire, or a distributed capacitance design. A thin layer of low-temperature thermal grease is applied between the surface (back) of the radio frequency coil 100 without components such as capacitors and the low-temperature surface of the semiconductor refrigeration unit 20 for heat exchange.

Exemplarily, the cooling system is used as follows:

(1) Use thermal grease and polyimide tape to fix the back of the radio frequency coil 100 to the cooling end of the topmost semiconductor refrigeration sheet 21, and the radio frequency coil lead 60 is connected to the corresponding number of the plug 40;

(2) The heat dissipation end of the bottommost semiconductor refrigeration sheet 21 of the semiconductor refrigeration unit 20 is in close contact with the base 12 through thermal conductive silicone grease, and is fixed on the set position;

(3) Connect the current lead of the semiconductor refrigeration unit 20 to the plug 40, after arranging the wiring, cover the vacuum upper cover 11, and use an O-ring and vacuum grease for vacuum sealing;

(4) The components such as the preamplifier, the TR switch and the matching circuit of the radio frequency coil 100 are connected to the outside of the plug 40;

(5) Connect the vacuum pump and the suction port of the vacuum chamber, pump the vacuum to less than 10 ^-2 Pa, close the non-magnetic vacuum valve, and use vacuum sealing mud to seal around the valve to prevent air leakage;

(6) Put the entire cooling system and the radio frequency coil into the magnetic resonance imaging equipment, and place the tested sample 200 above the vacuum upper cover 11;

(7) Turn on the cooling water circulation module 32, turn on the power of the semiconductor refrigeration unit, and cool and freeze the radio frequency coil. Through the temperature measurement of the thermometer 81, after observing the temperature, the matching circuit is adjusted to 50Ω, and magnetic resonance imaging is performed.

Compared with the prior art, the cooling system for the radio frequency coil disclosed in this embodiment has the following effects: (1) The radio frequency coil is cooled by means of semiconductor refrigeration, which can improve safety, greatly reduce the volume of the system, and realize continuous Uninterrupted cooling and controlled cooling temperature. (2) The design of non-magnetic non-metallic materials is adopted to prevent the interference of metal to the magnetic field of the magnetic resonance system and the shielding of radio frequency signals. (3) Liquid cooling with larger cooling capacity is used to dissipate heat to further increase the cooling power and provide safety guarantee. (4) The surface of the non-magnetic vacuum chamber is treated with polyurethane low-temperature glue to improve the air tightness and thermal insulation performance of the vacuum chamber. (5) The design can be quickly replaced, the external adjustment coil is matched, and it is suitable for radio frequency coils of different sizes, nuclides and shapes.

The specific embodiments of the present invention have been described in detail above. Although some embodiments have been shown and described, those skilled in the art should understand that the principles and spirit of the present invention, which are defined in the scope of the claims and their equivalents, are not departed from. Under the circumstances, these embodiments can be modified and perfected, and these modifications and improvements should also fall within the protection scope of the present invention.

Claims

A cooling system for a radio frequency coil, wherein the cooling system comprises:

The vacuum chamber includes a base and a vacuum upper cover, and the vacuum upper cover is covered with the base to form a closed space;

a semiconductor refrigeration unit, disposed in the vacuum cavity, the heat dissipation end of the semiconductor refrigeration unit is in contact with the base, and the cooling end of the semiconductor refrigeration unit is used to carry the radio frequency coil;

The cooling unit is connected to the base and is used for absorbing heat from the heat dissipation end of the semiconductor refrigeration unit.
The cooling system for a radio frequency coil according to claim 1, wherein the semiconductor refrigeration unit comprises a plurality of stacked semiconductor refrigeration sheets, and the cooling end of one of the two adjacent semiconductor refrigeration sheets is connected to the other one. The cooling end of the semiconductor refrigeration sheet abuts, wherein the cooling end of the topmost semiconductor cooling sheet carries the radio frequency coil, and the cooling end of the bottommost semiconductor cooling sheet is connected to the base.
The cooling system for a radio frequency coil according to claim 2, wherein the power of each piece of the refrigerating chip increases along the direction from the topmost layer to the bottommost layer.
The cooling system for a radio frequency coil according to claim 1, wherein a side wall of the vacuum upper cover is provided with an insertion hole, the cooling system further comprises a current lead and a plug, the plug is sealed with the insertion hole The two ends of the current lead are respectively electrically connected to the semiconductor refrigeration unit and the plug, and one end of the plug located outside the vacuum upper cover is used to connect to a matching circuit.
The cooling system for a radio frequency coil according to claim 4, wherein the cooling system further comprises a radio frequency coil lead wire, and both ends of the radio frequency coil lead wire are electrically connected to the radio frequency coil and the plug, respectively.
The cooling system for a radio frequency coil according to claim 2, wherein the cooling unit comprises a cooling water pipe and a cooling water circulation module that communicate with each other, a receiving groove is opened inside the base, and the cooling water pipe is connected to the cooling water pipe. The accommodating tank communicates to deliver cooling water into the accommodating tank.
The cooling system for a radio frequency coil according to claim 1, wherein the cooling system further comprises a thermometer, and the thermometer is disposed on the cooling end of the semiconductor refrigeration unit.
The cooling system for a radio frequency coil according to claim 1, wherein the inner surface of the vacuum upper cover is coated with polyurethane low temperature glue.
The cooling system for a radio frequency coil according to claim 1, wherein the material of the vacuum upper cover is a non-magnetic non-metallic material.
A magnetic resonance imaging device, comprising a radio frequency coil and the cooling system for the radio frequency coil according to claim 1, the radio frequency coil being arranged on the cooling end of the semiconductor refrigeration unit.
The magnetic resonance imaging apparatus according to claim 10, wherein the semiconductor refrigeration unit comprises a plurality of stacked semiconductor refrigeration sheets, and the cooling end of one of the two adjacent semiconductor refrigeration sheets is connected to the other semiconductor refrigeration sheet. The cooling end of the semiconductor refrigeration sheet on the top layer bears a radio frequency coil, and the cooling end of the semiconductor refrigeration sheet on the bottom layer is connected to the base.
The magnetic resonance imaging apparatus according to claim 11 , wherein the power of each of the refrigerating chips increases along the direction from the topmost layer to the bottommost layer.
The magnetic resonance imaging apparatus according to claim 10, wherein a side wall of the vacuum upper cover is provided with a socket, the cooling system further comprises a current lead and a plug, the plug is sealedly connected with the socket, and Both ends of the current lead are electrically connected to the semiconductor refrigeration unit and the plug respectively, and one end of the plug located outside the vacuum upper cover is used for connecting to a matching circuit.
The magnetic resonance imaging apparatus according to claim 13, wherein the cooling system further comprises a radio frequency coil lead, two ends of the radio frequency coil lead are electrically connected to the radio frequency coil and the plug, respectively.
The magnetic resonance imaging apparatus according to claim 11, wherein the cooling unit comprises a cooling water pipe and a cooling water circulation module that communicate with each other, an accommodation groove is opened inside the base, and the cooling water pipe communicates with the accommodation groove , to transport cooling water into the holding tank.
The magnetic resonance imaging apparatus according to claim 10, wherein the cooling system further comprises a thermometer, the thermometer is provided on the cooling end of the semiconductor refrigeration unit.
The magnetic resonance imaging apparatus according to claim 10, wherein the inner surface of the vacuum upper cover is coated with polyurethane low temperature glue.
The magnetic resonance imaging apparatus according to claim 10, wherein the material of the vacuum upper cover is a non-magnetic non-metallic material.