A radio frequency signal receiving system for magnetic resonance imaging

Abstract

The present invention discloses a radio frequency signal receiving system for magnetic resonance imaging. The system comprises: a cryogenic holding device, a coil and a preamplifier, wherein the cryogenic holding device 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 region and a closed cavity surrounding the vacuum region, the vacuum layer is connected to a 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. The radio frequency signal receiving system provided by the present invention has the advantages of high signal-to-noise ratio, wide application, easy operation and easy maintenance, and is suitable for imaging multiple parts of the human body such as knee joints, arms, and wrists.

Description

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 technology has become an important means of imaging human soft tissues due to its advantages of being non-invasive, radiation-free, high-resolution, high-contrast, and imaging in any orientation. When performing magnetic resonance imaging, the magnetic resonance imaging system sends magnetic resonance signals to the human body through the transmitting coil. After the human tissue is stimulated by the signal, the feedback electromagnetic signal is fed back to the system through the receiving coil. Among them, the signal strength received by the receiving coil largely determines the quality of the reconstructed image.

[0003] The signal-to-noise ratio is the core parameter of coil design. A high signal-to-noise ratio means higher resolution and higher contrast, which means better image quality. The stronger the signal received by the coil from the human body and the smaller the thermal noise of the receiving coil itself, the higher the signal-to-noise ratio and the better the receiving performance. The former requires the coil or resonant structure to be as close as possible to the imaging site, and the latter can be achieved by reducing the temperature of the coil and circuit.

[0004] The coil products currently on the market work at room temperature, and the thermal noise of the coil and related circuits limits the improvement of the signal-to-noise ratio. For example, patent application CN201310059788.9 discloses a knee radio frequency coil for a magnetic resonance imaging system, which reduces noise by placing the coil in a low-temperature environment, thereby ultimately improving the signal-to-noise ratio. However, the solution has the following defects:

[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 best condition or even fail to work at all, and the current component production process is far from being able to ensure that its actual value is completely consistent with the nominal value. In addition, when components such as capacitors are soaked in liquid nitrogen, the electromagnetic parameters of the capacitor material are affected by temperature changes, and its capacitance value usually changes accordingly. Therefore, the production of magnetic resonance coils at low temperatures cannot be separated from repeated manual measurement and debugging according to its state. Even for experienced engineers, this process takes weeks or even months. However, existing technologies rarely consider 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 for larger imaging parts such as the knee joint is acceptable, but the imaging quality for smaller imaging parts such as the wrist will be reduced.

[0007] 3) The coil part adopts a birdcage coil design. Since this coil has high requirements for symmetry, it usually brings difficulties to debugging. If it is not debugged properly, it may cause a sharp drop in signal uniformity.

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

[0009] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a radio frequency signal receiving system for magnetic resonance imaging. The system comprises: a cryogenic holding device, a coil and a preamplifier, wherein the cryogenic holding device 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, 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.

[0010] In one embodiment, the heat-insulating cover contains a cavity, and a second suction port is provided on the heat-insulating cover, and the cavity of the heat-insulating cover is evacuated through the second suction port.

[0011] In one embodiment, thermal insulation is achieved by filling the cavity of the thermal insulation cover with thermal insulation material.

[0012] 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.

[0013] In one embodiment, the coil is a semi-flexible circuit board with a coil array and related circuits etched on the circuit board, and the coil is inserted along the liquid nitrogen chamber and then connected end to end.

[0014] In one embodiment, the shell, the heat-insulating cover and the closed cavity are all made of non-magnetic non-metallic materials.

[0015] In one embodiment, the non-metallic material includes fiberglass or thermoplastic material.

[0016] 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.

[0017] 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.

[0018] In one embodiment, the thermoplastic material is a 3D printing material.

[0019] Compared with the prior art, the advantage of the present invention is that a unique low-temperature holding 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 also 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 improved 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, and is particularly suitable for imaging parts of different sizes such as the human knee, arm, and wrist.

[0020] 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 attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0022] Figure 1 is a front view of a radio frequency signal receiving system according to an embodiment of the present invention;

[0023] Figure 2 is a cross-sectional view of a radio frequency signal receiving system according to an embodiment of the present invention;

[0024] Figure 3 is another cross-sectional view of a radio frequency signal receiving system according to an embodiment of the present invention;

[0025] Figure 4 is a schematic diagram of the working process of a radio frequency signal receiving system according to an embodiment of the present invention;

[0026] Figure 5 Schematic diagram of coil insertion according to one embodiment of the present invention. DETAILED DESCRIPTION

[0027] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that 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 unless otherwise specifically stated.

[0028] 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.

[0029] 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 as part of the specification.

[0030] 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.

[0031] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0032] Combination Figure 1 , Figure 2 and Figure 3 As shown, the provided multi-channel radio frequency signal receiving system for magnetic resonance imaging includes a cryogenic device, a coil 5 contained in the cryogenic device, and a preamplifier 8 disposed outside the cryogenic device. Figure 1 In the example of FIG. 1 , the cryogenic device is provided with a housing 1, a heat-insulating cover 2 and a vacuum layer 6. The housing 1 may be Figure 2 The wrapped vacuum layer 6 shown may also be just a support. The shape of the housing 1 is not limited to the style shown in the figure, and may also be other shapes suitable for supporting.

[0033] Figure 2 The example vacuum layer 6 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 arranged on the top of the thermal insulation cover 2 and communicates with the vacuum cavity of the thermal insulation cover 2, and the other is arranged on the side of the shell 1 and communicates with 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.

[0034] exist Figure 1 In the embodiment, the low temperature holding device is also 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.

[0035] 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.

[0036] In one embodiment, the entire cryogenic device can be made of non-magnetic materials. For example, the housing 1, the heat-insulating cover 2 and the vacuum chamber are all 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. As long as these materials meet the requirements of being non-magnetic, non-metallic, sufficient to form a vacuum environment, and having no magnetic resonance signal or the magnetic resonance signal is insufficient to affect the imaging effect, it can be used.

[0037] In one embodiment, the coil 5 is a semi-flexible circuit board on which the coil array and related circuits are etched. When installing, 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. Figure 5 As shown. The coil 5 is connected to the preamplifier 8. The cooled 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.

[0038] 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 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 to make 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.

[0039] For a further understanding of the present invention, see Figure 4 As shown, the working process of the provided multi-channel radio frequency signal receiving system for magnetic resonance imaging includes the following steps:

[0040] Step S1, vacuumizing the vacuum layer 6 through the vacuum port 4;

[0041] Step S2, inserting the coil 5 into the liquid nitrogen chamber 7;

[0042] Step S3, injecting liquid nitrogen into the liquid nitrogen chamber 7 so that the liquid nitrogen covers the coil 5, and performing a test;

[0043] Step S4, determining whether the signal-to-noise ratio of the coil reaches a set index;

[0044] Step S5, if the set index is not reached, pour out the liquid nitrogen, take out the coil adjustment components, and then continue to execute step S2;

[0045] Step S6, if the set index has been reached, the device is placed on the magnetic resonance imaging bed and covered with a heat preservation cover;

[0046] Step S7, the tested part is covered with the signal improvement layer 11 and then placed in the device.

[0047] It should be understood that, without violating the spirit and scope of the present invention, those skilled in the art may make appropriate changes or modifications to the above embodiments. For example, the cryogenic coil is not limited to being used together with the signal improvement layer, and the cryogenic coil may also be used alone. For another example, it is not limited to being used for human imaging, but also applicable to animal imaging. In addition, the vacuum port, pressure relief port, etc. are not limited to being located at the illustrated positions, but may also be located at other positions that meet their functional requirements.

[0048] In summary, compared with the prior art, the present invention has the following advantages:

[0049] 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.

[0050] 2) Compared with using metasurfaces as a signal amplification tool, the present invention uses high dielectric materials to improve electromagnetic distribution, improves imaging quality, and can also use other resonant structures to amplify signals.

[0051] 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.

[0052] 4) Different from using only frozen coils for imaging, the radio frequency signal receiving system of the present invention can not only use the barrel coil soaked in liquid nitrogen for imaging alone, but also can be used with a signal improvement layer to adapt to 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.

[0053] 5) The present invention can amplify signals for small parts of different sizes, such as wrists and arms, and improve image quality by using a resonant circuit. In addition, by using a high dielectric material, the electromagnetic distribution of the measured part can be improved for ultra-high field applications such as 5T and 7T, thereby obtaining higher image quality.

[0054] Embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the marketplace, or to enable other persons of ordinary skill 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 cryogenic holding device, a coil and a preamplifier, wherein the cryogenic holding device is provided with a shell, a heat-insulating cover and a vacuum layer, the shell wraps the vacuum layer, the vacuum layer includes a vacuum region and a closed cavity surrounding the vacuum region, the vacuum layer is connected to a first draw port, the first draw port is arranged on the side of the shell, 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; The heat-insulating cover contains a cavity, and the heat-insulating cover is provided with a second extraction port, through which the cavity of the heat-insulating cover is evacuated; Wherein, 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; Wherein, 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; wherein, the housing, the insulation cover and the closed cavity are all made of non-magnetic non-metallic materials; It also includes that when imaging the target part, a signal improvement layer is covered on the target part, wherein the signal improvement layer is made of a resonant circuit or a high dielectric material adapted to the size of the target part; Wherein, a pressure relief port is provided on the heat-insulating cover, and the pressure relief port passes through the heat-insulating cover and is communicated with the closed cavity. The cable comes out through the pressure relief port, and the cable does not completely block the pressure relief port.

2. 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.

3. The system according to claim 1, characterized in that The non-metallic material includes glass fiber reinforced plastic or thermoplastic material.

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

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