Radio frequency signal receiving system for magnetic resonance imaging

Abstract

Disclosed in the present invention is a radio frequency signal receiving system for magnetic resonance imaging. The system comprises: a low-temperature holding apparatus, a coil and a preamplifier, wherein the low-temperature holding apparatus is provided with a shell, a heat preservation cover and a vacuum layer. The shell wraps the vacuum layer; the vacuum layer comprises a vacuum area and a closed cavity surrounding the vacuum area, and the vacuum layer is in communication with a first vacuumizing port; and the coil is arranged in the closed cavity, and a signal generated by the coil is transmitted to a magnetic resonance system by means of the preamplifier. The radio frequency signal receiving system provided in the present invention has the advantages of being high in signal-to-noise ratio, wide in application, easy in operation, easy in maintenance, etc., and is suitable for imaging of multiple parts of a human body, such as knee joints, arms and wrists.

Description

A radio frequency signal receiving system for magnetic resonance imaging Technical Field

[0001] The present invention relates to the technical field of magnetic resonance imaging, and more particularly to a radio frequency signal receiving system for magnetic resonance imaging. Background Art

[0002] Magnetic resonance imaging (MRI) has become an important tool for imaging human soft tissue due to its advantages, including being non-invasive, radiation-free, high-resolution, high-contrast, and the ability to image cross-sections in any orientation. During MRI, the system transmits magnetic resonance signals to the human body via a transmitting coil. The tissue is stimulated by these signals and then transmits electromagnetic signals back to the system via a receiving coil. The strength of the signals received by the receiving coils largely determines the quality of the reconstructed image.

[0003] The signal-to-noise ratio (SNR) is a key parameter in coil design. A high SNR means higher resolution and contrast, which translates to better image quality. The stronger the signal received by the coil from the human body, and the lower the thermal noise of the receiving coil itself, the higher the SNR and the better the reception performance. The former requires the coil or resonant structure to be as close as possible to the imaging site, while the latter can be achieved by reducing the temperature of the coil and circuitry.

[0004] Currently available coil products operate at room temperature, and the thermal noise generated by the coil and related circuits limits the improvement of the signal-to-noise ratio. For example, patent application CN201310059788.9 discloses a knee radiofrequency coil for magnetic resonance imaging systems. This solution reduces noise by placing the coil in a low-temperature environment, ultimately achieving an improved signal-to-noise ratio. However, this solution has the following drawbacks:

[0005] 1) It is not conducive to debugging the RF coil during the production process. Unlike ordinary mass-produced products, for magnetic resonance coils, a slight difference in the value of a component will cause the coil to not work in the optimal state or even fail to work at all, and the current component production process is far from being able to guarantee that its actual value is completely consistent with the nominal value. In addition, when components such as capacitors are soaked in liquid nitrogen, their capacitance values ​​usually change because the electromagnetic parameters of the capacitor material are affected by temperature changes. Therefore, the production of magnetic resonance coils at low temperatures cannot be separated from repeated manual measurement and debugging based on their status. Even for experienced engineers, this process takes weeks or even months. Existing technologies pay little attention to the feasibility, ease of operation, and subsequent ease of maintenance of coil debugging.

[0006] 2) When used as a single coil only, the imaging quality is acceptable for larger imaging areas such as the knee joint, but the imaging quality will be reduced for smaller imaging areas such as the wrist.

[0007] 3) The coil part adopts a birdcage coil design. Due to its high requirements for symmetry, this coil usually brings difficulties to debugging. If the debugging is not done well, it may cause a sharp drop in signal uniformity.

[0008] In the existing technology, the article "Adaptive Cylindrical Wireless Metasurfaces in Clinical Magnetic Resonance Imaging" (ADVANCED MATERIALS) uses the system's body coil as the receiving coil, and wraps the imaging area with a metasurface to enhance the signal, ultimately improving the received signal-to-noise ratio. This solution is effective for imaging smaller imaging areas such as the wrist or animals such as mice, but is not suitable for imaging larger body parts. In addition, since the signal of the body coil itself is relatively weak, the obtained system signal-to-noise ratio still has room for improvement.

[0009] Summary of the Invention

[0010] The present invention aims to overcome the shortcomings of the prior art and provides a radio frequency signal receiving system for magnetic resonance imaging. The system comprises a cryogenic device, a coil, and a preamplifier. The cryogenic device comprises an outer shell, an insulating cover, and a vacuum layer. The outer shell encloses the vacuum layer, which comprises a vacuum region and a sealed cavity surrounding the vacuum region. The vacuum layer is connected to a first extraction port. The coil is disposed within the sealed cavity, and the signal generated by the coil is transmitted to the magnetic resonance system via the preamplifier.

[0011] In one embodiment, the heat-insulating cover contains a cavity, and a second extraction port is provided on the heat-insulating cover, through which the cavity of the heat-insulating cover is vacuumed.

[0012] In one embodiment, heat insulation is achieved by filling the cavity of the heat-insulating cover with heat-insulating material.

[0013] In one embodiment, the coil is a local coil, and liquid nitrogen is injected into the closed cavity to form a liquid nitrogen cavity, and the injected liquid nitrogen covers the coil.

[0014] In one embodiment, the coil is a semi-flexible circuit board with a coil array and related circuits etched on the circuit board. The coil is inserted along the liquid nitrogen chamber and then connected end to end.

[0015] In one embodiment, the shell, the heat-insulating cover and the closed cavity are all made of non-magnetic non-metallic materials.

[0016] In one embodiment, the non-metallic material includes fiberglass or thermoplastic material.

[0017] In one embodiment, a pressure relief port is provided on the heat-insulating cover, and the pressure relief port passes through the heat-insulating cover and communicates with the closed cavity. The cable exits through the pressure relief port, and the cable does not completely block the pressure relief port.

[0018] In one embodiment, the system further comprises: when imaging the target site, covering the target site with a signal improvement layer, wherein the signal improvement layer is made of a resonant circuit or a high dielectric material adapted to the size of the target site.

[0019] In one embodiment, the thermoplastic material is a 3D printing material.

[0020] Compared with the existing technology, the advantage of the present invention is that a unique low-temperature maintenance device is designed for the radio frequency signal receiving system, and an open design is used, which is conducive to the repeated debugging of the radio frequency coil during the production process and does not require additional freezing equipment. In addition, it can be matched with a signal improvement layer to adapt to the imaging of parts of different sizes to meet different needs such as signal amplification and improvement of electromagnetic distribution. By combining the radio frequency coil at low temperature with the signal improvement layer, a radio frequency signal receiving system is formed that can improve imaging performance in a variety of application scenarios. It is particularly suitable for imaging parts of different sizes such as the human knee joint, arm, and wrist.

[0021] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0023] FIG1 is a front view of a radio frequency signal receiving system according to an embodiment of the present invention;

[0024] FIG2 is a cross-sectional view of a radio frequency signal receiving system according to an embodiment of the present invention;

[0025] FIG3 is another cross-sectional view of a radio frequency signal receiving system according to an embodiment of the present invention;

[0026] FIG4 is a schematic diagram of the working process of a radio frequency signal receiving system according to an embodiment of the present invention;

[0027] FIG. 5 is a schematic diagram of coil insertion according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0029] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0030] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0031] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0032] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] As shown in Figures 1, 2, and 3, the provided multi-channel RF signal receiving system for magnetic resonance imaging includes a cryogenic device, a coil 5 housed within the cryogenic device, and a preamplifier 8 disposed externally thereto. In the example of Figure 1, the cryogenic device comprises an outer shell 1, an insulating cover 2, and a vacuum layer 6. The outer shell 1 may enclose the vacuum layer 6, as shown in Figure 2, or it may simply be a support. The shape of the outer shell 1 is not limited to that shown in the figure and may also have other shapes suitable for providing support.

[0034] The vacuum layer 6 shown in FIG2 includes a vacuum area and a closed cavity (not shown) surrounding the vacuum area. The thermal insulation cover 2 contains a vacuum cavity, which can be evacuated through the vacuum port 4. For example, there are two vacuum ports 4, one of which is provided on the top of the thermal insulation cover 2 and is connected to the vacuum cavity of the thermal insulation cover 2, and the other is provided on the side of the outer shell 1 and is connected to the vacuum layer 6 in the low-temperature maintenance device. It should be understood that the thermal insulation cover 2 is not limited to being insulated with a vacuum cavity, and can also be insulated by filling with materials such as foam. By insulating the thermal insulation cover 2, the low-temperature maintenance device can have a better insulation effect to ensure that the low-temperature maintenance device does not absorb heat from the outside, thereby effectively maintaining a low-temperature environment. In addition, the designed low-temperature maintenance device does not require additional cooling equipment, thereby reducing costs.

[0035] In FIG1 , the low-temperature holding device is further provided with a pressure relief port 3 , a cable 9 connected to the pressure relief port, and a preamplifier 8 connected to the cable 9 .

[0036] In one embodiment, a liquid nitrogen cavity 7 is formed between the vacuum layers 6. When the system is working, the injected liquid nitrogen needs to cover (flood) the coil 5. The vacuum port 4 is connected to the vacuum layer 6.

[0037] In one embodiment, the entire cryogenic device can be made of non-magnetic materials. For example, the outer shell 1, the insulation cover 2, and the vacuum chamber can all be made of non-magnetic, non-metallic materials. For example, fiberglass or other 3D printing materials that meet the strength and density requirements can be used. These materials can be used as long as they meet the requirements of being non-magnetic, non-metallic, sufficient to form a vacuum environment, and having no magnetic resonance signal or a magnetic resonance signal that is insufficient to affect the imaging effect.

[0038] In one embodiment, the coil 5 is a semi-flexible circuit board with a coil array and related circuitry etched thereon. During installation, the coil 5 can be inserted along the liquid nitrogen chamber 7 and then connected end to end to complete the installation of the coil, as shown in Figure 5. The coil 5 is connected to the preamplifier 8. After cooling, the coil obtains a signal with a high signal-to-noise ratio, which is transmitted to the magnetic resonance system for processing through the cable 9 and the preamplifier 8. The pressure relief port 3 passes through the insulation cover 2 and is connected to the liquid nitrogen chamber 7. The cable 9 exits through the pressure relief port 3. The cable 9 should not completely block the pressure relief port 3.

[0039] In practical applications, in order to adapt to the imaging of parts of different sizes, a signal improvement layer can also be used to image the target part. For example, the signal improvement layer 11 can be implemented by a resonant circuit or by a high dielectric material. When the signal improvement layer 11 is a resonant circuit structure, its function is to amplify the signal fed back from the measured part, thereby improving the signal strength of the radio frequency signal receiving system and thus improving the signal-to-noise ratio. When the signal improvement layer 11 is a high dielectric material, its function is to improve the electromagnetic field distribution of the measured part, making it more uniform, thereby obtaining a higher quality image. Under ultra-high field strengths such as 5T and 7T (T is the unit of magnetic field strength, Tesla), the higher the field strength, the more significant the imaging quality effect obtained.

[0040] For further understanding of the present invention, referring to FIG4 , the working process of the multi-channel radio frequency signal receiving system for magnetic resonance imaging includes the following steps:

[0041] Step S1, vacuuming the vacuum layer 6 through the vacuum port 4;

[0042] Step S2, inserting the coil 5 into the liquid nitrogen chamber 7;

[0043] Step S3, injecting liquid nitrogen into the liquid nitrogen chamber 7 so that the liquid nitrogen covers the coil 5, and performing a test;

[0044] Step S4, determining whether the signal-to-noise ratio of the coil reaches a set index;

[0045] Step S5: If the set index is not reached, pour out the liquid nitrogen, remove the coil adjustment components, and then continue to execute step S2;

[0046] Step S6: If the set index has been reached, the device is placed on the MRI bed and covered with a heat-insulating cover;

[0047] In step S7 , the tested part is covered with the signal improvement layer 11 and then placed in the device.

[0048] It should be understood that those skilled in the art may make appropriate changes or modifications to the above embodiments without departing from the spirit and scope of the present invention. For example, the cryogenic coil is not limited to use with the signal-enhancing layer; the cryogenic coil can also be used alone. Another example is not limited to human imaging; it is also applicable to animal imaging. Furthermore, vacuum ports, pressure relief ports, etc. are not limited to the locations shown; they can also be located in other locations that meet their functional requirements.

[0049] In summary, compared with the prior art, the present invention has the following advantages:

[0050] 1) The present invention uses a local coil immersed in liquid nitrogen, which has a higher signal-to-noise ratio than using a body coil as a receiving coil.

[0051] 2) Compared with using metasurfaces as a signal amplification tool, the present invention uses high-dielectric materials to improve electromagnetic distribution, enhances imaging quality, and can also use other resonant structures to amplify signals.

[0052] 3) The low-temperature holding device of the present invention adopts an open design, which is conducive to repeated debugging of the radio frequency coil during the manufacturing process.

[0053] 4) Unlike imaging using only cryogenic coils, the RF signal receiving system of the present invention not only uses a barrel coil immersed in liquid nitrogen for imaging alone, but can also be combined with a signal-enhancing layer to accommodate imaging of various sizes, meeting diverse requirements such as signal amplification and improved electromagnetic distribution. By combining cryogenic RF coils with the signal-enhancing layer, a RF signal receiving system is constructed that improves imaging performance in a variety of application scenarios.

[0054] 5) By incorporating a resonant circuit, this invention can amplify signals for various small areas, such as the wrist and arm, improving image quality. Furthermore, by incorporating high-dielectric materials, it can improve the electromagnetic distribution of the measured area for ultra-high field applications, such as 5T and 7T, thereby achieving even higher image quality.

[0055] While various embodiments of the present invention have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technological improvements in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein. The scope of the present invention is defined by the appended claims.

Claims

1. A radio frequency signal receiving system for magnetic resonance imaging, comprising: A low-temperature holding device, a coil and a preamplifier, wherein the low-temperature holding device is provided with an outer shell, a heat-insulating cover and a vacuum layer, the outer shell wraps the vacuum layer, the vacuum layer comprises a vacuum area and a closed cavity surrounding the vacuum area, the vacuum layer is connected to the first draw port, the coil is arranged in the closed cavity, and the signal generated by the coil is transmitted to the magnetic resonance system via the preamplifier.

2. The system according to claim 1, characterized in that The heat-insulating cover contains a cavity, and a second suction port is provided on the heat-insulating cover, through which the cavity of the heat-insulating cover is evacuated.

3. The system according to claim 1, characterized in that The heat insulation is achieved by filling the cavity of the heat-insulating cover with heat-insulating material.

4. The system according to claim 1, characterized in that The coil is a local coil. Liquid nitrogen is injected into the closed cavity to form a liquid nitrogen cavity, and the injected liquid nitrogen covers the coil.

5. The system according to claim 4, characterized in that The coil is a semi-flexible circuit board on which a coil array and related circuits are etched, and the coil is inserted along the liquid nitrogen cavity and then connected end to end.

6. The system according to claim 1, characterized in that The shell, the heat-insulating cover and the closed cavity are all made of non-magnetic non-metallic materials.

7. The system according to claim 6, characterized in that The non-metallic material includes glass fiber reinforced plastic or thermoplastic material.

8. The system according to claim 1, characterized in that The heat-insulating cover is provided with a pressure relief port, which passes through the heat-insulating cover and is in communication with the closed cavity. The cable exits through the pressure relief port, and the cable does not completely block the pressure relief port.

9. The system according to claim 1, characterized in that The method further includes covering the target site with a signal improvement layer when imaging the target site, wherein the signal improvement layer is made of a resonant circuit or a high dielectric material adapted to the size of the target site.

10. The system according to claim 7, characterized in that The thermoplastic material is a 3D printing material.

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