Magnetic resonance dual frequency birdcage coil and related equipment

Abstract

The present application relates to a magnetic resonance dual-frequency birdcage coil and related equipment, the magnetic resonance dual-frequency birdcage coil comprises: a first end ring; a second end ring, which is separated from the first end ring in the axial direction, and comprises N first LC parallel resonant circuits which are arranged in sequence in the circumferential direction and connected in series with each other, the resonant frequency of the first LC parallel resonant circuit is a first frequency; a third end ring, which is separated from the second end ring in the axial direction and is located on the side of the second end ring away from the first end ring; N legs, which are arranged in sequence and separated in the circumferential direction between the first end ring and the third end ring, each leg comprises a first part connecting the first end ring and the second end ring, and a second part connecting the second end ring and the third end ring, the first part comprises a second LC parallel resonant circuit, the resonant frequency of the second LC parallel resonant circuit is a second frequency; the first end ring, the legs and the third end ring can resonate at the first frequency, and the second end ring, the second part and the third end ring can resonate at the second frequency.

Description

Technical Field

[0001] The present application relates to the field of magnetic resonance technology, and in particular to a magnetic resonance dual-frequency birdcage coil and related equipment. Background Art

[0002] The RF resonant frequency of the magnetic resonance system is proportional to the main magnetic field:

[0003] f0=γ·B0

[0004] Among them, B0 is the size of the main magnetic field, and γ is the magnetic gyrometry ratio. The magnetic gyrometry ratios of different nuclides are different. Therefore, the resonant frequency f0 of the magnetic resonance system is related to both the size of the main magnetic field and the nuclides. There are many nuclides in the human body, some of which, such as 1H hydrogen protons and 23Na sodium, 31P phosphorus, 13C carbon, 19F fluorine, etc., can generate signals in the magnetic resonance system, and the signals are even large enough for imaging.

[0005] However, the MRI systems and RF coils in the industry are generally single-frequency systems, because most of them only use the MRI signal of 1H protons as the imaging nuclide. This is because the content and signal of other nuclides (referred to as heteronuclei) in the human body are many times lower than that of 1H, so the signal-to-noise ratio (SNR) of the obtained MRI images is very low, which is of little significance for diagnosis and scientific research.

[0006] However, dual-frequency coils and even multi-frequency coils still have great prospects: on the one hand, dual-frequency coils can be used for two magnetic resonance systems with different frequencies at the same time, such as being compatible with 1.5T and 3.0T magnetic resonance systems at the same time, which can effectively reduce the number of coils equipped in hospital machines and reduce procurement costs; on the other hand, since the signal of the nuclide will increase with the enhancement of the main magnetic field of the magnetic resonance, with the promotion and application of ultra-high field strength (7T, 9.4T) magnetic resonance imaging systems, the imaging of heteronuclear nuclei has also become possible. Especially from the perspective of human physiological metabolism, protons carry very little physiological information and can hardly provide any metabolic information. However, some non-proton nuclides, such as 23Na sodium and 31P phosphorus, reflect the balanced concentration of electrolytes inside and outside cells and tissues, and carry more abundant human physiological and metabolic information, so the imaging of heteronuclear nuclei has high clinical significance. Summary of the invention

[0007] Among dual-frequency coils, birdcage coils are a very important category because they have unique advantages in terms of excitation efficiency and uniformity within a certain frequency range. The design of dual-frequency birdcage coils needs to focus on the mutual influence between the dual frequencies. In order to reduce this influence, the schemes may include: 1. Double coil layering, installing the coils of two frequencies on cylinders with different inner diameters, which can reduce mutual influence; 2. Single coil dual resonance, using a combination of inductors and capacitors, so that one coil has dual-frequency resonance excitation capabilities at the same time; 3. Double coil staggered, installing the dual-frequency coils on the same cylinder, but the legs of the double coils are staggered and tuned separately. The double coils in this scheme usually adopt two 1*N phased array coil designs [Bili Wang et al., A radially interleaved sodium and proton coil array for brain MRI at 7T. NMR Biomed. 2021 December; 34(12): e4608. doi: 10.1002 / nbm.4608.].

[0008] The coil size of the first solution is obviously too large, and because the outer layer blocks the inner debugging, the optimization and debugging of the inner side is complicated and difficult, and the efficiency and signal-to-noise ratio of the outer layer are also sacrificed; the frequency-related components (capacitors or inductors) in the second solution usually affect two frequencies at the same time, making it difficult for the component values ​​to meet the dual-frequency requirements at the same time. The third solution is very simple to design, debug and optimize the coil, but the inventor found that its excitation efficiency and uniformity are not high.

[0009] In view of this, the present application provides a magnetic resonance dual-frequency birdcage coil and related equipment to solve at least one of the above-mentioned technical problems.

[0010] In a first aspect, the present application provides a magnetic resonance dual-frequency birdcage coil, comprising:

[0011] first end ring;

[0012] A second end ring is spaced apart from the first end ring in the axial direction and includes N first LC parallel resonant circuits arranged in sequence in a circumferential direction around the axial direction and connected in series with each other, the resonant frequency of the first LC parallel resonant circuit is a first frequency, and N is an integer not less than 4;

[0013] a third end ring, spaced apart from the second end ring in the axial direction and located on a side of the second end ring away from the first end ring;

[0014] N legs are sequentially arranged between the first end ring and the third end ring along the circumferential direction and spaced apart from each other, each of the first LC parallel resonant circuits is configured between two different adjacent legs, each of the legs comprises a first portion connecting the first end ring and the second end ring, and a second portion connecting the second end ring and the third end ring, the first portion comprises a second LC parallel resonant circuit, and a resonant frequency of the second LC parallel resonant circuit is a second frequency;

[0015] The first end ring, the leg and the third end ring are capable of resonating at the first frequency, and the second end ring, the second part and the third end ring are capable of resonating at the second frequency.

[0016] In some possible implementations, in the axial direction, the distance between the first end ring and the second end ring is smaller than the distance between the third end and the second end ring.

[0017] In some possible implementations, the first frequency is lower than the second frequency.

[0018] In some possible implementations, N is an integer multiple of 4.

[0019] In some possible implementations, N=8.

[0020] In some possible implementations, the first LC parallel resonant circuit includes a first capacitor and a first inductor connected in parallel to each other, the second LC parallel resonant circuit includes a second capacitor and a second inductor connected in parallel to each other, the capacitance value of the first capacitor is different from the capacitance value of the second capacitor, and the inductance value of the first inductor is different from the inductance value of the second inductor.

[0021] In some possible implementations, the first end ring includes N third capacitors arranged sequentially in the circumferential direction and connected in series with each other, and each of the third capacitors is configured between two different adjacent legs;

[0022] The third end ring includes N fourth capacitors arranged sequentially in the circumferential direction and connected in series with each other, and each of the fourth capacitors is configured between two different adjacent legs;

[0023] The third capacitor and the fourth capacitor have the same capacitance value.

[0024] In some possible implementations, the second end ring includes N fifth capacitors that are sequentially arranged in the circumferential direction and connected in series with the N first LC parallel resonant circuits, and each of the fifth capacitors is configured between two different adjacent legs;

[0025] The capacitance value of the combined circuit formed by the fifth capacitor and the first LC parallel resonant circuit is equal to the capacitance values ​​of the third capacitor and the fourth capacitor.

[0026] In a second aspect, the present application provides a coil device, comprising:

[0027] The magnetic resonance dual-frequency birdcage coil as described in the first aspect;

[0028] The shell is formed into a cylindrical shape extending along the axial direction, and the magnetic resonance dual-frequency birdcage coil is installed in the shell.

[0029] In a third aspect, the present application provides a magnetic resonance device, comprising the coil device as described in the second aspect.

[0030] According to the magnetic resonance dual-frequency birdcage coil provided by the present application, when it receives a radio frequency signal of the first frequency, each first LC parallel resonant circuit resonates at the first frequency, so that the second end ring is in an open circuit state without working, and the first end ring, the leg and the third end ring constitute the first birdcage coil. By selecting the second capacitor and the second inductor as appropriate capacitance values ​​and inductance values, respectively, the first end ring, the leg and the third end ring constitute the first birdcage coil in this state. Resonate at the first frequency. Similarly, when the magnetic resonance dual-frequency birdcage coil receives a radio frequency signal of the second frequency, each second LC parallel resonant circuit resonates at the second frequency, so that the first end ring and the first part of the leg are in an open circuit state without working, and the second end ring, the second part of the leg and the third end ring constitute the second birdcage coil. By selecting the first capacitor and the first inductor as appropriate capacitance values ​​and inductance values, respectively, the second end ring, the second part of the leg and the third end ring in this state can resonate at the second frequency. In addition, since it works as a birdcage coil in both frequency states, it has high excitation efficiency and uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present application, rather than limiting the present application.

[0032] Figure 1 It is a three-dimensional schematic diagram of a magnetic resonance dual-frequency birdcage coil provided by an embodiment of the present application.

[0033] Figure 2 yes Figure 1 The structure schematic diagram of the magnetic resonance dual-frequency birdcage coil after being flattened.

[0034] Figure 3 yes Figure 1The circuit structure diagram of the magnetic resonance dual-frequency birdcage coil after being flattened is shown.

[0035] Figure 4 yes Figure 1 The simulation calculation diagram of the magnetic resonance dual-frequency birdcage coil is shown, where the horizontal axis is the frequency and the vertical axis is the reflection dB value.

[0036] Figure 5 yes Figure 1 The B1 field distribution diagram of the MRI dual-frequency birdcage coil shown is applied as a transmitting coil in a Siemens 1.5T MRI system (the center point flip angle is 1440°).

[0037] Figure 6 yes Figure 1 The B1 field distribution diagram of the MRI dual-frequency birdcage coil shown is applied as a transmitting coil in a Siemens 3.0T MRI system (the center point flip angle is 1440°).

[0038] Figure 7 yes Figure 1 The schematic diagram of the image signal-to-noise ratio and uniformity test of the magnetic resonance dual-frequency birdcage coil used as a receiving coil in a Siemens 1.5T magnetic resonance system is shown.

[0039] Figure 8 yes Figure 1 The figure shows a schematic diagram of image signal-to-noise ratio and uniformity testing of a dual-frequency magnetic resonance birdcage coil used as a receiving coil in a Siemens 3.0T magnetic resonance system.

[0040] Description of reference numerals:

[0041] 1-first end ring, 2-second end ring, 3-third end ring, 4-leg, 4A-first part, 4B-second part;

[0042] C1-first capacitor, C2-second capacitor, C3-third capacitor, C4-fourth capacitor, C5-fifth capacitor;

[0043] L1 - first inductor, L2 - second inductor. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the embodiment of the present application will be clearly and completely described below in conjunction with the drawings of the embodiment of the present application. Obviously, the described embodiment is a part of the embodiment of the present application, rather than all the embodiments. Based on the described embodiment of the present application, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of this application. It can be understood that, in the absence of conflict, some technical means of the various embodiments described herein can be replaced or combined with each other.

[0045] In the description of the specification and claims of this application, if there are terms such as "first", "second", etc., they are only used to distinguish the objects described and do not have any order or technical meaning. Therefore, the objects defined as "first", "second", etc. may explicitly or implicitly include one or more of the objects. In addition, "one" or "a" and similar words do not indicate a quantitative limitation, but indicate the existence of at least one, and "multiple" means no less than two.

[0046] Now, embodiments of the present application are described with reference to the accompanying drawings.

[0047] Figures 1 to 3 A magnetic resonance dual-frequency birdcage coil provided according to some embodiments of the present application is shown, which includes a first end ring 1, a second end ring 2, a third end ring 3 and 8 legs 4.

[0048] The first end ring 1, the second end ring 2 and the third end ring 3 are arranged in sequence and spaced apart in the axial direction, and in the axial direction, the distance between the first end ring 1 and the second end ring 2 is smaller than the distance between the third end ring 3 and the second end ring 2. In addition, the first end ring 1, the second end ring 2 and the third end ring 3 have the same size and are parallel to each other.

[0049] The second end ring 2 includes 8 first LC parallel resonant circuits arranged in sequence in the circumferential direction around the aforementioned axial direction, and the 8 first LC parallel resonant circuits are connected in series with each other. Specifically, the first LC parallel resonant circuit includes a first capacitor C1 and a first inductor L1 connected in parallel with each other, and the first capacitor C1 and the first inductor L1 are respectively selected to have appropriate capacitance values ​​and inductance values, so that the resonant frequency of each first LC parallel resonant circuit is the first frequency, that is, each first LC parallel resonant circuit resonates at a specified first frequency.

[0050] The eight legs 4 are arranged in sequence and spaced apart along the circumferential direction between the first end ring 1 and the third end ring 3. Each of the aforementioned eight first LC parallel resonant circuits is configured between two different adjacent legs 4. In other words, a first LC parallel resonant circuit is correspondingly arranged between any two adjacent legs 4. Each leg 4 connects the first end ring 1, the second end ring 2 and the third end ring 3. Specifically, the first leg 4 includes a first portion 4A connecting the first end ring 1 and the second end ring 2, and a second portion 4B connecting the second end ring 2 and the third end ring 3. Based on the aforementioned content and in combination with Figure XX, it can be seen that the first portion 4A and the second portion 4B are both connected between two adjacent first LC parallel resonant circuits. In addition, the eight legs 4 can be arranged at equal intervals along the circumferential direction and extend in a substantially straight line in the axial direction.

[0051] The first part 4A of each leg 4 includes a second LC parallel resonant circuit. Specifically, the second LC parallel resonant circuit includes a second capacitor C2 and a second inductor L2 connected in parallel with each other, and the second capacitor C2 and the second inductor L2 are respectively selected to have appropriate capacitance values ​​and inductance values, so that the resonant frequency of each second LC parallel resonant circuit is the second frequency, that is, each second LC parallel resonant circuit resonates at a specified second frequency. The capacitance value of the first capacitor C1 is different from that of the second capacitor C2, the inductance value of the first inductor L1 is different from that of the second inductor L2, and the first frequency is lower than the second frequency. For example, the first frequency is 63.6 MHz and the second frequency is 123.2 MHz.

[0052] Furthermore, the first end ring 1 , the leg 4 and the third end ring 3 can resonate at the aforementioned first frequency, and the second end ring 2 , the second portion 4B and the third end ring 3 can resonate at the aforementioned second frequency.

[0053] In this way, when the magnetic resonance dual-frequency birdcage coil receives a radio frequency signal of the first frequency, since each first LC parallel resonant circuit resonates at the first frequency, the second end ring 2 is in an open circuit state and is not in operation. The first end ring 1, the leg 4 and the third end ring 3 constitute a first birdcage coil. By selecting the second capacitor C2 and the second inductor L2 as appropriate capacitance and inductance values ​​respectively (obviously, the selection of this value must also ensure that the second LC parallel resonant circuit can resonate and open circuit at the second frequency), the first birdcage coil constituted by the first end ring 1, the leg 4 and the third end ring 3 in this state can resonate at the first frequency. Similarly, when the magnetic resonance dual-frequency birdcage coil receives a radio frequency signal of the second frequency, since each second LC parallel resonant circuit resonates at the second frequency, the first end ring 1 and the first part 4A of the leg 4 are in an open circuit state without operation, and the second end ring 2, the second part 4B of the leg 4 and the third end ring 3 constitute a second birdcage coil. By selecting the first capacitor C1, the first inductor L1 and the fifth capacitor C5 described later as appropriate capacitance and inductance values ​​respectively (obviously, the selection of this value must also ensure that the first LC parallel resonant circuit resonates and is open circuit at the first frequency), the second birdcage coil constituted by the second end ring 2, the second part 4B of the leg 4 and the third end ring 3 in this state can resonate at the second frequency.

[0054] It is well known that the resonant frequency of a parallel resonant circuit consisting of a capacitor and an inductor is:

[0055]

[0056] If the capacitor and inductor are connected in parallel and resonate at a certain frequency, it is equivalent to an open circuit for the signal of this frequency; for signals with lower frequencies, this parallel capacitor and inductor can be equivalent to an inductor; for high frequencies, it is equivalent to a capacitor. By utilizing the above characteristics of the capacitor and inductor connected in parallel, the aforementioned dual-frequency resonance of the birdcage coil can be realized relatively simply.

[0057] The first end ring 1 also includes 8 third capacitors C3 arranged in sequence in the circumferential direction and connected in series with each other, and each third capacitor C3 is configured between two different adjacent legs 4. Similar to the first end ring 1, the third end ring 3 includes 8 fourth capacitors C4 arranged in sequence in the circumferential direction and connected in series with each other, and each fourth capacitor C4 is configured between two different adjacent legs 4. Moreover, the first capacitor C1 and the second capacitor C2 have the same capacitance value. In addition, the second end ring 2 includes 8 fifth capacitors C5 arranged in sequence in the circumferential direction and connected in series with the aforementioned 8 first LC parallel resonant circuits, and each fifth capacitor C5 is configured between two different adjacent legs 4. Moreover, the capacitance value of the combined circuit formed by the second capacitor C2 and the first LC parallel resonant circuit is equal to the capacitance value of the first capacitor C1 and the second capacitor C2. In this way, the magnetic resonance dual-frequency birdcage coil can ensure the symmetry in the electrical structure regardless of whether it works at the first frequency (the working mode corresponding to the aforementioned first birdcage coil) or the second frequency (the working mode corresponding to the aforementioned second birdcage coil), thereby facilitating the generation of a uniform magnetic resonance signal (B1 field).

[0058] In order to verify the above description, it is judged that Figure 1 and Figure 2 Can this birdcage coil achieve dual-frequency operation in Siemens 1.5T system (frequency 63.6MHz) and 3.0T system (frequency 123.2MHz)? The inventor specifically configures the first frequency to be 63.6MHz and the second frequency to be 123.2MHz.

[0059] First, the RF circuit of the magnetic resonance dual-frequency birdcage coil was simulated to see whether the dual-frequency resonance effect can be achieved smoothly. The simulation results are as follows: Figure 3 As shown, it can be seen that the magnetic resonance dual-frequency birdcage coil has good resonance peaks at 63.6 MHz and 123.2 MHz.

[0060] Furthermore, a dual-frequency birdcage coil prototype was built, and after adding the RF output port and matching network, the magnetic resonance dual-frequency birdcage coil was connected to the Siemens 1.5T Vanto system and 3.0T Skyra system for excitation field uniformity test and receiving signal-to-noise ratio test. The test results are as follows Figures 4 to 8As shown, it can be seen that the birdcage coil has relatively excellent B1 field uniformity and image signal-to-noise ratio at 1.5T63.6MHz and 3.0T123MHz.

[0061] although Figures 1 to 3 The number of the legs 4 is 8, but it should be understood that the legs 4 may also be of other numbers, such as 4 or 16. Generally speaking, in order to better match a standard magnetic resonance system, the number of the legs 4 is preferably an integer multiple of 4.

[0062] An embodiment of the present application further provides a coil device, comprising a shell and the above-mentioned magnetic resonance dual-frequency birdcage coil, wherein the shell is formed into a cylindrical shape extending along the axial direction, and the magnetic resonance dual-frequency birdcage coil is installed in the shell.

[0063] An embodiment of the present application further provides a magnetic resonance device, which includes the aforementioned coil device.

Claims

1. A magnetic resonance dual-frequency birdcage coil, characterized in that: include: first end ring; A second end ring is spaced apart from the first end ring in the axial direction and includes N first LC parallel resonant circuits arranged in sequence in a circumferential direction around the axial direction and connected in series with each other, the resonant frequency of the first LC parallel resonant circuit is a first frequency, and N is an integer not less than 4; a third end ring, spaced apart from the second end ring in the axial direction and located on a side of the second end ring away from the first end ring; N legs are sequentially arranged between the first end ring and the third end ring along the circumferential direction and spaced apart from each other, each of the first LC parallel resonant circuits is configured between two different adjacent legs, each of the legs comprises a first portion connecting the first end ring and the second end ring, and a second portion connecting the second end ring and the third end ring, the first portion comprises a second LC parallel resonant circuit, and a resonant frequency of the second LC parallel resonant circuit is a second frequency; wherein the first end ring, the leg and the third end ring are capable of resonating at the first frequency, and the second end ring, the second portion and the third end ring are capable of resonating at the second frequency; The first end ring includes N third capacitors arranged sequentially in the circumferential direction and connected in series with each other, and each of the third capacitors is configured between two different adjacent legs; The third end ring includes N fourth capacitors arranged sequentially in the circumferential direction and connected in series with each other, and each of the fourth capacitors is configured between two different adjacent legs; Wherein, the third capacitor and the fourth capacitor have the same capacitance value; The second end ring includes N fifth capacitors which are arranged sequentially in the circumferential direction and are connected in series with the N first LC parallel resonant circuits, and each of the fifth capacitors is arranged between two different adjacent legs; The capacitance value of the combined circuit formed by the fifth capacitor and the first LC parallel resonant circuit is equal to the capacitance values ​​of the third capacitor and the fourth capacitor.

2. The magnetic resonance dual-frequency birdcage coil according to claim 1, characterized in that: In the axial direction, the distance between the first end ring and the second end ring is smaller than the distance between the third end ring and the second end ring.

3. The magnetic resonance dual-frequency birdcage coil according to claim 1, characterized in that: The first frequency is lower than the second frequency.

4. The magnetic resonance dual-frequency birdcage coil according to claim 1, characterized in that: N is an integer multiple of 4.

5. The magnetic resonance dual-frequency birdcage coil according to claim 1, characterized in that: N＝8。 6. The magnetic resonance dual-frequency birdcage coil according to claim 1, characterized in that: The first LC parallel resonant circuit includes a first capacitor and a first inductor connected in parallel with each other, and the second LC parallel resonant circuit includes a second capacitor and a second inductor connected in parallel with each other, the capacitance value of the first capacitor is different from the capacitance value of the second capacitor, and the inductance value of the first inductor is different from the inductance value of the second inductor.

7. A coil device, characterized in that: include: The magnetic resonance dual-frequency birdcage coil according to any one of claims 1 to 6; The shell is formed into a cylindrical shape extending along the axial direction, and the magnetic resonance dual-frequency birdcage coil is installed in the shell.

8. A magnetic resonance device, characterized in that: Comprising the coil arrangement of claim 7.

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