Magnetic resonance birdcage coil and magnetic resonance equipment with same

Abstract

The invention relates to a magnetic resonance birdcage coil and magnetic resonance equipment. The magnetic resonance birdcage coil includes: a first end ring; a second end ring spaced apart from the first end ring in the axial direction; the first supporting legs are sequentially arranged between the first end ring and the second end ring at equal intervals in the circumferential direction around the axial direction, each first supporting leg is connected with the first end ring and the second end ring, each first supporting leg is connected with a first LC parallel resonance circuit in series, and the resonance frequency of the first LC parallel resonance circuit is a first frequency; the second supporting legs are sequentially arranged between the first end ring and the second end ring at equal intervals in the circumferential direction, each second supporting leg is connected with the first end ring and the second end ring, each second supporting leg is connected with a second LC parallel resonance circuit in series, and the resonance frequency of the second LC parallel resonance circuit is a second frequency different from the first frequency; the first end ring, the second leg, and the second end ring can resonate at a first frequency, and the first end ring, the first leg, and the second end ring can resonate at a second frequency.

Description

[0001] This application is a divisional application of the application titled "Magnetic Resonance Birdcage Coil and Magnetic Resonance Equipment" filed with the China Patent Office on January 29, 2024, with the application number 202410119312.8, and the original application is incorporated herein by reference. Technical Field

[0002] This application relates to the field of magnetic resonance technology, and in particular, to a magnetic resonance birdcage coil and a magnetic resonance equipment having the same. Background Art

[0003] The radiofrequency resonance frequency of a magnetic resonance system is directly proportional to the main magnetic field:

[0004] f0 = γ·B0

[0005] Where B0 is the magnitude of the main magnetic field and γ is the gyromagnetic ratio, and the gyromagnetic ratio of different nuclides is different. Therefore, the resonance frequency f0 of the magnetic resonance system is related to both the magnitude of the main magnetic field and the type of nuclide. There are various nuclides in the human body, and some of them, such as 1H hydrogen protons, 23Na sodium, 31P phosphorus, 13C carbon, 19F fluorine, etc., can generate signals in the magnetic resonance system, and even the signals are large enough for imaging.

[0006] However, the magnetic resonance systems and radiofrequency coils in the industry are generally single-frequency systems because the vast majority of them only use the magnetic resonance signals of 1H protons as imaging nuclides. This is because the content and signals of other nuclides (abbreviated as heteronuclei) in the human body are many times lower than those of 1H, resulting in a very low signal-to-noise ratio (SNR) of the obtained magnetic resonance images, and the diagnostic and research significance is insufficient.

[0007] 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 different-frequency magnetic resonance systems simultaneously, 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 for hospital machines and reduce the procurement cost; on the other hand, since the signals of nuclides will increase with the enhancement of the magnetic resonance main magnetic field, with the popularization and application of ultra-high field strength (7T, 9.4T) magnetic resonance imaging systems, the imaging of heteronuclei has also become possible. Especially from the perspective of human physiological metabolism, the physiological information carried by protons is very little and almost cannot provide any metabolic information. While some non-proton nuclides, such as 23Na sodium, 31P phosphorus, etc., reflect the electrolyte balance concentration inside and outside cells and tissues, and the human physiological and metabolic information they carry is more abundant, and imaging of heteronuclei has high clinical significance. Summary of the Invention

[0008] In a dual - frequency coil, the birdcage coil is a very important category. Because in terms of excitation efficiency and uniformity, within a certain frequency range, the birdcage has unique advantages. When designing a dual - frequency birdcage coil, the mutual influence between the two frequencies needs to be considered. To reduce this influence, the solutions can include: 1. Double - coil layering, installing coils of two frequencies on cylinders with different inner diameters, which can reduce the mutual influence; 2. Single - coil double resonance, using an inductance - capacitance combination method to enable a single coil to have the ability to excite dual - frequency resonance simultaneously; 3. Double - coil stagger, installing dual - frequency coils on the same cylinder, but the legs of the two coils are staggered from each other and tuned separately. In this solution, the two coils usually adopt the design of two 1*N phased - array coils [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.].

[0009] For the first solution above, the coil size will be significantly larger. Moreover, since the outer layer blocks the debugging of the inner layer, the inner - layer optimization and debugging are relatively complex and difficult, and the efficiency and signal - to - noise ratio of the outer layer are also sacrificed; in the second solution, the frequency - related devices (capacitors or inductors) usually affect both frequencies simultaneously, making it difficult for the component values to meet the dual - frequency requirements at the same time. For the third solution, the coil design, debugging, and optimization are very simple, but the inventor found that its excitation efficiency and uniformity are not high.

[0010] In view of this, the present application provides a magnetic resonance birdcage coil and a magnetic resonance device having the same to solve at least one of the above - mentioned technical problems.

[0011] In a first aspect, the present application provides a magnetic resonance birdcage coil, including:

[0012] A first end - ring;

[0013] A second end - ring, axially spaced from the first end - ring;

[0014] A plurality of first legs, arranged equidistantly in sequence in the circumferential direction around the axis between the first end - ring and the second end - ring. Each first leg connects the first end - ring and the second end - ring, and a first LC parallel resonance circuit is connected in series on each first leg. The resonance frequency of the first LC parallel resonance circuit is a first frequency;

[0015] A plurality of second legs, which are arranged equidistantly in sequence in the circumferential direction between the first end ring and the second end ring. Each second leg connects the first end ring and the second end ring, and a second LC parallel resonance circuit is connected in series on each second leg. The resonance frequency of the second LC parallel resonance circuit is a second frequency different from the first frequency;

[0016] Wherein, the first end ring, the second legs and the second end ring can resonate at the first frequency, and the first end ring, the first legs and the second end ring can resonate at the second frequency;

[0017] Wherein, the total number of the first legs is equal to the total number of the second legs, both being N. N third capacitors are connected in series on the first end ring and are arranged in sequence in the circumferential direction. Each third capacitor is disposed between two different adjacent first legs and between two different adjacent second legs; N fourth capacitors are connected in series on the second end ring and are arranged in sequence in the circumferential direction. Each fourth capacitor is disposed between two different adjacent first legs and between two different adjacent second legs.

[0018] In some possible embodiments, the third capacitors and the fourth capacitors have the same capacitance value.

[0019] In some possible embodiments, N is an integer multiple of 4.

[0020] In some possible embodiments, the first leg includes a fifth capacitor connected in series with the first LC parallel resonance circuit.

[0021] In some possible embodiments, except for the capacitors in the second LC parallel resonance circuit, no other capacitors are connected on the second legs.

[0022] In a second aspect, the present application provides a magnetic resonance device, including the magnetic resonance birdcage coil as described in the first aspect.

[0023] According to the magnetic resonance dual-frequency birdcage coil provided by the present application, when it receives a magnetic resonance radio frequency signal of the first frequency, since each first LC parallel resonance circuit resonates at this first frequency, each first leg is in an open circuit state where it does not work. The first end ring, the second leg, and the second end ring form a first birdcage coil. By respectively selecting appropriate capacitance values and inductance values for the second capacitor and the second inductor, the aforementioned first birdcage coil formed by the first end ring, the second leg, and the second end ring in this state can be made to resonate at the first frequency. Similarly, when this magnetic resonance birdcage coil receives a magnetic resonance radio frequency signal of the second frequency, since each second LC parallel resonance circuit resonates at this second frequency, each second leg is in an open circuit state where it does not work. The first end ring, the first leg, and the second end ring form a second birdcage coil. By respectively selecting appropriate capacitance values and inductance values for the first capacitor and the first inductor, the aforementioned second birdcage coil formed by the first end ring, the first leg, and the second end ring in this state can be made to resonate at the second frequency. Additionally, since it operates in a birdcage coil manner in both frequency states, it has high excitation efficiency and uniformity. Description of the Drawings

[0024] 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 described below only relate to some embodiments of the present application and do not limit the present application.

[0025] Figure 1 is a three-dimensional schematic diagram of a magnetic resonance dual-frequency birdcage coil provided by an embodiment of the present application.

[0026] Figure 2 is Figure 1 a schematic structural diagram of the shown magnetic resonance dual-frequency birdcage coil after being flattened.

[0027] Figure 3 is Figure 1 a schematic circuit structural diagram of the shown magnetic resonance dual-frequency birdcage coil after being flattened.

[0028] Figure 4 is Figure 1 a simulation calculation diagram of the dual-frequency coil of the shown magnetic resonance dual-frequency birdcage coil, where the abscissa is the frequency and the ordinate is the reflection dB value.

[0029] Figure 5 is Figure 1 a B1 field distribution diagram (the central point flip angle is 1440°) of the shown magnetic resonance dual-frequency birdcage coil applied as a transmit coil to a Siemens 1.5T magnetic resonance system.

[0030] Figure 6 is Figure 1The B1 field distribution diagram (center point flip angle is 1440°) of the shown magnetic resonance dual-frequency birdcage coil applied as a transmitting coil to a Siemens 3.0T magnetic resonance system.

[0031] Figure 7 is Figure 1 Schematic diagram of the image signal-to-noise ratio and uniformity test of the shown magnetic resonance dual-frequency birdcage coil applied as a receiving coil to a Siemens 1.5T magnetic resonance system.

[0032] Figure 8 is Figure 1 Schematic diagram of the image signal-to-noise ratio and uniformity test of the shown magnetic resonance dual-frequency birdcage coil applied as a receiving coil to a Siemens 3.0T magnetic resonance system.

[0033] Explanation of reference numerals:

[0034] 1 - First end ring, 2 - Second end ring, 3 - First leg, 4 - Second leg;

[0035] C1 - First capacitor, C2 - Second capacitor, C3 - Third capacitor, C4 - Fourth capacitor, C5 - Fifth capacitor;

[0036] L1 - First inductor, L2 - Second inductor. Detailed implementation manners

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the described embodiments of this application belong to the scope of protection of this application. It can be understood that, without conflict, some technical means described in the various embodiments herein may be replaced or combined with each other.

[0038] In the description of the specification and claims of this application, if there are terms such as "first" and "second", they are only used to distinguish the described objects and do not have any sequential or technical meanings. Thus, the objects defined with "first", "second", etc. may explicitly or implicitly include one or more of such objects. And, words such as "one" or "a" do not represent a quantity limitation, but rather indicate the existence of at least one, and "multiple" means not less than two.

[0039] Now, the embodiments of this application will be described with reference to the accompanying drawings.

[0040] Figures 1 to 3Shows a magnetic resonance birdcage coil provided according to some embodiments of the present application, which includes a first end ring 1, a second end ring 2, eight first legs 3, and eight second legs 4.

[0041] The first end ring 1 and the second end ring 2 are arranged axially spaced apart, and they can have the same size and be parallel to each other.

[0042] The eight first legs 3 are arranged equidistantly in sequence in the circumferential direction around the axis between the first end ring 1 and the second end ring 2. Each first leg 3 connects the first end ring 1 and the second end ring 2, and a first LC parallel resonance circuit is connected in series on each first leg 3. Specifically, the first LC parallel resonance circuit includes a first capacitor C1 and a first inductor L1 connected in parallel with each other. By respectively selecting appropriate capacitance values and inductance values for the first capacitor C1 and the first inductor L1, the resonance frequency of each first LC parallel resonance circuit is the first frequency, that is, each first LC parallel resonance circuit resonates at a specified first frequency.

[0043] Similar to the case of the first legs 3, the eight second legs 4 are also arranged equidistantly in sequence in the circumferential direction between the first end ring 1 and the second end ring 2. Each second leg 4 connects the first end ring 1 and the second end ring 2, and a second LC parallel resonance circuit is connected in series on each second leg 4. Specifically, the second LC parallel resonance circuit includes a second capacitor C2 and a second inductor L2 connected in parallel with each other. By respectively selecting appropriate capacitance values and inductance values for the second capacitor C2 and the second inductor L2, the resonance frequency of each second LC parallel resonance circuit is the second frequency, that is, each second LC parallel resonance circuit resonates at a specified second frequency.

[0044] The capacitance value of the first capacitor C1 is different from the capacitance value of the second capacitor C2, and the inductance value of the first inductor L1 is different from the inductance value of the second inductor L2. Based on this, the first frequency is different from the second frequency.

[0045] Moreover, the first end ring 1, the second legs 4, and the second end ring 2 can resonate at the aforementioned first frequency, and the first end ring 1, the first legs 3, and the second end ring 2 can resonate at the aforementioned second frequency.

[0046] In this way, when the magnetic resonance birdcage coil receives a magnetic resonance radio frequency signal of the first frequency, since each first LC parallel resonance circuit resonates at the first frequency, each first leg is in an open circuit state where it does not work. The first end ring 1, the second leg 4, and the second end ring 2 form the first birdcage coil. By respectively selecting appropriate capacitance values and inductance values for the second capacitor C2 and the second inductor L2 (obviously, the selection of these values should also ensure that the second LC parallel resonance circuit can resonate at the second frequency), the first birdcage coil formed by the first end ring 1, the second leg 4, and the second end ring 2 in this state can be made to resonate at the first frequency. Similarly, when the magnetic resonance birdcage coil receives a magnetic resonance radio frequency signal of the second frequency, since each second LC parallel resonance circuit resonates at the second frequency, each second leg 4 is in an open circuit state where it does not work. The first end ring 1, the first leg 3, and the second end ring 2 form the second birdcage coil. By respectively selecting appropriate capacitance values and inductance values for the first capacitor C1, the first inductor L1, and the fifth capacitor C5 (to be described later) (obviously, the selection of these values should also ensure that the first LC parallel resonance circuit resonates at the first frequency), the second birdcage coil formed by the first end ring 1, the first leg 3, and the second end ring 2 in this state can be made to resonate at the second frequency.

[0047] As is well known, the resonance frequency of a parallel resonance circuit composed of a capacitor and an inductor is:

[0048]

[0049] If the capacitor and inductor are in parallel resonance at a certain frequency, for a signal of this frequency, it is equivalent to an open circuit; for a signal with a lower frequency, this parallel capacitor and inductor can be equivalent to an inductor; for a high frequency, it is equivalent to a capacitor. By utilizing the above characteristics of the parallel connection of the capacitor and inductor, the aforementioned dual-frequency resonance of the birdcage coil can be achieved relatively simply.

[0050] Eight third capacitors C3 arranged in series and connected to each other in the circumferential direction are also connected in series to the first end ring 1. Each third capacitor C3 is arranged between two different adjacent first legs 3 and also between two different adjacent second legs 4. Similar to the case of the first end ring 1, eight fourth capacitors C4 arranged in series and connected to each other in the circumferential direction are connected in series to the second end ring 2. Each fourth capacitor C4 is arranged between two different adjacent first legs 3 and also between two different adjacent second legs 4. Moreover, the third capacitor C3 and the fourth capacitor C4 have the same capacitance value. In this way, whether the magnetic resonance birdcage coil operates at the first frequency (the operating mode corresponding to the aforementioned first birdcage coil) or at the second frequency (the operating mode corresponding to the aforementioned second birdcage coil), it can ensure the electrical structure symmetry of the coil, thus contributing to generating a uniform magnetic resonance signal (B1 field).

[0051] In addition, the first leg 3 further includes a fifth capacitor C5 connected in series with the first LC parallel resonance circuit. By configuring the fifth capacitor C5, the following object can be easily achieved: while ensuring that the first LC parallel resonance circuit formed by the parallel connection of the first capacitor C1 and the first inductor L1 can resonate at the first frequency, the electrical performance of the first leg 3 is adjusted by the fifth capacitor so that the first leg 3, the first end ring 1, and the second end ring 2 can resonate at the second frequency. In addition, no other capacitors are connected to the second leg 4 except the second capacitor C2.

[0052] Please refer to Figure 1 , in this embodiment, 8 first legs 3 and 8 second legs 4 are arranged into a plurality of leg pairs that are equally spaced in the circumferential direction, and each leg pair includes a first leg 3 and a second leg 4. For each leg pair, one end of the first leg 3 and one end of the second leg 4 are connected to the same part of the first end ring 1, the other end of the first leg 3 and the other end of the second leg 4 are connected to the same part of the second end ring 2, and the first leg 3 and the second leg 4 are symmetrically arranged with respect to a virtual plane (not shown), and the virtual plane is a plane that extends axially and passes through the center of the circumference (the virtual plane extends on the diameter of the first end ring 1 and the second end ring 2). In this way, a dual-frequency birdcage coil with high structural symmetry can be easily manufactured.

[0053] To verify the above description, it is judged whether such a birdcage coil with Figure 1 and Figure 2 configuration can achieve dual-frequency operation under the Siemens 1.5T system (frequency 63.6 MHz) and 3.0T system (frequency 123.2 MHz). The inventor specifically configures the first frequency to 63.6 MHz and the second frequency to 123.2 MHz.

[0054] First, the radio frequency circuit of this magnetic resonance birdcage coil is simulated and calculated to see if the dual-frequency resonance effect can be successfully achieved. The simulation results are as Figure 4 shown, and it can be seen that this magnetic resonance birdcage coil has good resonance peaks at 63.6 MHz and 123.2 MHz.

[0055] Moreover, a dual-frequency birdcage coil prototype is constructed. After adding a radio frequency output port and a matching network, this magnetic resonance birdcage coil is connected to the Siemens 1.5T Avanto system and 3.0T Skyra system for excitation field uniformity testing and received signal-to-noise ratio testing. The test results are as Figures 5 to 8 shown, and it can be seen that there are relatively excellent B1 field uniformity and good image signal-to-noise ratio at 1.5T 63.6 MHz and 3.0T 123 MHz.

[0056] Although Figures 1 to 3 In Figures 1 to 3 , the number of both the first legs 3 and the second legs 4 is 8. However, it should be understood that the first legs 3 and the second legs 4 may also have other numbers, such as 4 or 16, etc. Generally speaking, in order to better match a standard magnetic resonance system, the number of the first legs 3 and the second legs 4 is preferably an integer multiple of 4.

[0057] In some other embodiments, the number of the first legs 3 and the number of the second legs 4 may also be different. For example, there are 4 first legs 3 and 8 second legs 4.

[0058] The embodiment of the present application also provides a magnetic resonance device, which includes the aforementioned magnetic resonance birdcage coil.

Claims

1. A magnetic resonance birdcage coil, characterized in that, Comprising: A first end ring; A second end ring, axially spaced apart from the first end ring; A plurality of first legs, sequentially arranged equidistantly in the circumferential direction around the axis between the first end ring and the second end ring, each first leg connecting the first end ring and the second end ring, and a first LC parallel resonance circuit connected in series on each first leg, the resonance frequency of the first LC parallel resonance circuit being a first frequency; A plurality of second legs, sequentially arranged equidistantly in the circumferential direction between the first end ring and the second end ring, each second leg connecting the first end ring and the second end ring, and a second LC parallel resonance circuit connected in series on each second leg, the resonance frequency of the second LC parallel resonance circuit being a second frequency different from the first frequency; Wherein, the first end ring, the second legs and the second end ring can resonate at the first frequency, and the first end ring, the first legs and the second end ring can resonate at the second frequency; Wherein, the total number of the first legs is equal to the total number of the second legs, both being N; N third capacitors arranged sequentially in the circumferential direction are connected in series on the first end ring, each third capacitor being disposed between different adjacent two first legs and between different adjacent two second legs; N fourth capacitors arranged sequentially in the circumferential direction are connected in series on the second end ring, each fourth capacitor being disposed between different adjacent two first legs and between different adjacent two second legs.

2. The magnetic resonance birdcage coil according to claim 1, wherein The third capacitors and the fourth capacitors have the same capacitance value.

3. The magnetic resonance birdcage coil according to claim 1, wherein, N is an integer multiple of 4.

4. The magnetic resonance birdcage coil according to claim 1, characterized in that The first leg includes a fifth capacitor connected in series with the first LC parallel resonance circuit.

5. The magnetic resonance birdcage coil according to claim 1, wherein Except for the capacitors in the second LC parallel resonance circuit, no other capacitors are connected on the second leg.

6. A magnetic resonance device, characterized in that, Comprising the magnetic resonance birdcage coil according to any one of claims 1 to 5.

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