Self-decoupling coil array for magnetic resonance imaging

Abstract

The present invention relates to a self-decoupling coil array for magnetic resonance imaging, comprising resonant coils each having a detuning loop, wherein decoupling capacitors are connected in series to the resonant coils; at the positions where the decoupling capacitors are arranged, the two resonant coils are oppositely arranged to form decoupling units, and a plurality of decoupling units are arranged in at least one direction. The decoupling units oppositely arranged at the positions of the decoupling capacitors enable one resonant coil to be decoupled from the other resonant coil, and the decoupling units are present in pairs in the self-decoupling coil array, thereby preventing electrical coupling throughout the entire self‑decoupling coil array and thus achieving self‑decoupling. Compared with the prior art, the self-decoupling coil array for magnetic resonance imaging disclosed in the present application achieves decoupling between detuned resonant circuits by introducing additional electrical coupling, so that the sensitivity remains at an appropriate level and the imaging signal-to-noise ratio gain becomes more uniform.

Description

A self-decoupling coil array for magnetic resonance imaging Technical Field

[0001] This invention relates to the field of magnetic resonance imaging equipment technology, and more particularly to a self-decoupling coil array for magnetic resonance imaging. Background Technology

[0002] Magnetic resonance imaging is crucial in medical diagnosis, providing clear images of soft tissue morphology and function.

[0003] MRI systems are often limited by signal-to-noise ratio (SNR) when imaging small anatomical structures or requiring high spatial resolution. Studies have shown that combining wireless / wired surface coils with conventional receiving coils can significantly enhance the imaging SNR.

[0004] However, existing wireless / wired arrays are prone to mutual interference when operating in multi-channel mode, which can lead to sensitivity loss and uneven signal gain in wireless / wired arrays with multiple coils, affecting signal-to-noise ratio and image quality. Summary of the Invention

[0005] To address the shortcomings of existing wireless / wired arrays, which are prone to mutual interference during multi-channel operation, resulting in sensitivity loss and uneven signal gain in wireless / wired arrays with multiple coils, this invention proposes a self-decoupling coil array for magnetic resonance imaging.

[0006] The technical solution adopted in this invention is a self-decoupling coil array for magnetic resonance imaging, including a resonant coil with a detuning circuit, a decoupling capacitor connected in series with the resonant coil, two resonant coils being arranged opposite each other at the location where the decoupling capacitor is set to form a decoupling unit, and multiple decoupling units being arranged in at least one direction.

[0007] Preferably, the resonant coil is a passive resonant coil.

[0008] Preferably, no two resonant coils overlap.

[0009] Preferably, the multiple decoupling units are evenly arranged with the same distance between them in at least one direction.

[0010] Preferably, multiple decoupling units are arranged in two orthogonal directions.

[0011] Preferably, two resonant coils are positioned 5 mm apart and opposite each other at the location where the decoupling capacitor is set, thereby forming a decoupling unit. The side length of the resonant coil is 50 mm, and the size of the decoupling capacitor ranges from 1.4 picofarads to 1.9 picofarads.

[0012] Preferably, the decoupling unit does not bend along the length direction of any decoupling unit.

[0013] Preferably, the resonant coil is connected in series with an adjustable capacitor.

[0014] Preferably, an inductor is connected in series between the decoupling capacitor and the adjustable capacitor.

[0015] Preferably, the detuned circuit is a parallel LC circuit controlled by two pairs of bidirectional diodes.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This application discloses a self-decoupling coil array for magnetic resonance imaging, including resonant coils with detuning circuits. A decoupling capacitor is connected in series with the resonant coils. Two resonant coils are positioned opposite each other at the location of the decoupling capacitor to form a decoupling unit. Multiple decoupling units are arranged in at least one direction. The decoupling units positioned opposite each other at the location of the decoupling capacitor enable one resonant coil to decouple from the other. Since the decoupling units exist in pairs in the self-decoupling coil array, no electrical coupling occurs throughout the entire array, achieving self-decoupling.

[0018] Compared with the prior art, the self-decoupling coil array for magnetic resonance imaging disclosed in this application achieves decoupling between detuned resonant circuits by introducing additional electrical coupling, so that the sensitivity is maintained at the proper level, the imaging signal-to-noise ratio gain is more uniform, the wireless array coil is optimized, the signal-to-noise ratio and image quality in MRI imaging are improved, and the misjudgment of lesions by doctors due to uneven signal gain is avoided. Attached Figure Description

[0019] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein:

[0020] Figure 1 shows a schematic diagram of the use of a self-decoupling coil array for magnetic resonance imaging and the structure of a 12-channel self-decoupling coil array according to an embodiment of the present invention;

[0021] Figure 2 shows the decoupling capacitor C obtained by electromagnetic simulation of a self-decoupling coil array for magnetic resonance imaging according to an embodiment of the present invention. mode Capacity;

[0022] Figure 3 shows a circuit diagram of a resonant coil in a self-decoupling coil array for magnetic resonance imaging provided according to an embodiment of the present invention;

[0023] Figure 4 shows the experimental results of a water phantom imaging of a self-decoupling coil array for magnetic resonance imaging provided in an embodiment of the present invention;

[0024] Figure 5 shows the experimental results of a self-decoupling coil array for magnetic resonance imaging provided according to an embodiment of the present invention;

[0025] Figure 6 shows a comparison of the effects of a pair of conventional coils and a pair of self-decoupled coil arrays for magnetic resonance imaging provided according to an embodiment of the present invention (C). mode =1.5pF). Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0027] The present invention discloses a self-decoupling coil array for magnetic resonance imaging, including a resonant coil with a detuning circuit, the resonant coil being connected in series with a decoupling capacitor, two resonant coils being arranged opposite each other at the location where the decoupling capacitor is set to form a decoupling unit, and multiple decoupling units being arranged in at least one direction.

[0028] Decoupling units, positioned opposite each other and without overlap at the location of the decoupling capacitor, enable one resonant coil to decouple from another. Since these decoupling units exist in pairs within the self-decoupling coil array, no electrical coupling occurs within the entire array, achieving self-decoupling. Compared to existing technologies, this application discloses a self-decoupling coil array for magnetic resonance imaging. By introducing additional electrical coupling, it achieves decoupling between detuned resonant circuits, maintaining the appropriate sensitivity level, resulting in a more uniform signal-to-noise ratio gain, optimizing the wireless array coils, improving the signal-to-noise ratio and image quality in MRI imaging, and avoiding misdiagnosis of lesions due to uneven signal gain.

[0029] Specifically, the self-decoupling coil array used in this invention decouples itself from the resonant coils during operation. The current distribution of a single resonant coil is non-uniform, and the decoupling capacitor C... mode The current intensity on one side is smaller and the electric field intensity is stronger, thus introducing additional electrical coupling between the resonant coils and achieving self-decoupling.

[0030] It should be noted that the resonant coil has a detuned state and a resonant state. The detuned state is used to detune during the radio frequency transmission stage, and the resonant state is used to resonate during the reception stage to enhance the signal.

[0031] Multiple decoupling units are arranged in at least one direction. The specific number of directions chosen for arrangement depends on the size of the region requiring magnetic resonance imaging. When the region is large, multiple decoupling units can be arranged in more directions. The arrangement of multiple decoupling units in at least one direction is relative to a direction on the same plane. After multiple decoupling units are arranged on the same plane, they can be folded and bent into other shapes, such as cylindrical or dome shapes. Furthermore, the resonant coil is built based on coils, and coils themselves have a certain degree of elastic or plastic deformation capability; therefore, the resonant coil itself has the ability to bend.

[0032] Furthermore, the density of multiple decoupling units arranged in any direction can be determined based on the required gain at that location. For locations requiring a larger gain, the arrangement density at that location can be appropriately increased, i.e., the distance between two adjacent decoupling units.

[0033] This application does not limit the shape of the resonant coil. To achieve decoupling, it is only necessary to arrange the two resonant coils opposite each other at the location of the decoupling capacitor.

[0034] This invention is a self-decoupling coil array, therefore it does not limit the use of the receiving coil; any conventional receiving coil can be used. This invention is not limited by the type, size, or dimensions of the resonant coils in the self-decoupling coil array, nor by the number of channels in the self-decoupling coil array, nor by the distribution plane of the self-decoupling coil array; it can be distributed on a plane or on a cylindrical surface. Furthermore, the RF receiving coil and the self-decoupling coil array can be placed directly adjacent to each other or at a certain distance.

[0035] The feasibility of this invention has been experimentally verified. Referring to Figure 4, a nearly two-fold improvement in signal-to-noise ratio is clearly visible on the surface during water model testing. Referring to Figure 5, in human body imaging, a 45% improvement in signal-to-noise ratio is observed in the region of interest (ROI) for knee joint imaging.

[0036] The working process of the self-decoupling coil array is as follows: During the radio frequency (RF) transmission phase of the magnetic resonance imaging (MRI) system, the PIN diode in the detuned circuit of the resonant coil of the self-decoupling coil array is turned on, putting the entire resonant coil in a detuned state. The response of the self-decoupling coil array to the RF transmission field is attenuated, thus minimizing its impact on the RF transmission field. When the self-decoupling coil array operates in the receiving phase, the PIN diode in the detuned circuit of the resonant coil of the wireless array is not turned on, the detuned circuit is not working, and the signal can pass through. Under Faraday's law of electromagnetic induction, the change in magnetic flux passing through the wireless array induces an electromotive force in the self-decoupling coil array. The self-decoupling coil array amplifies this voltage signal by a factor of Q (the quality factor of the self-decoupling coil array) before it is received by the RF receiving coil, thereby enhancing the signal-to-noise ratio of the imaging signal. This invention provides an embodiment example: a 12-channel self-decoupling coil array for knee joint imaging, the placement of which is shown in Figure 1. In Figure 1, label 101 represents the self-decoupling coil array for MRI, and label 102 represents the RF receiving coil (knee coil).

[0037] The tuning of the self-decoupling coil array includes tuning, detuning, and decoupling; its resonant coil is shown in Figure 3, where the unit structure of the wireless array adopts a loop structure, and its tuning is achieved through the adjustable capacitor C in the tuning circuit of the resonant coil. Tune This is achieved by adjusting C1 and L1, where the frequency of the detuned loop in the loop is controlled by adjusting C1 and L1. The self-decoupling coil array uses a decoupling capacitor C connected in series with the resonant coil. mode Its capacitance is very small, allowing for the introduction of additional electrical coupling to counteract the magnetic coupling between opposing resonant coils, thereby reducing the coupling between individual unit loops. As shown in Figure 2, C mode The size of C will control the magnitude of electrical coupling. mode The smaller the value, the greater the electrical coupling. C can be determined through electromagnetic simulation. mode The size of the capacitance value.

[0038] It should be explained that the curves from top to bottom in Figure 6 represent the coupling magnitude when a pair of conventional coils, a pair of self-decoupling coil arrays are placed normally, and a pair of self-decoupling coil arrays are placed opposite each other. The best decoupling effect can be obtained when they are placed opposite each other.

[0039] In some embodiments, the resonant coil is a passive resonant coil.

[0040] Meanwhile, the resonant coil is a passive coil. Compared to wired phased array coils, the manufacturing and integration process of traditional wired phased array coils can be more costly and complex, requiring simplification to reduce overall medical costs and improve the accessibility of MRI systems. In other embodiments, the resonant coil can also be a wired resonant coil.

[0041] In some embodiments, any two resonant coils do not overlap.

[0042] It should be noted that when resonant coils are placed in overlapping positions, a certain overlap area is required to achieve overlap decoupling. However, when facing two adjacent resonant coils with a small overlap area, decoupling cannot be achieved through overlap. In this case, a decoupling capacitor is needed to completely achieve the purpose of decoupling the self-decoupling coil array.

[0043] In some embodiments, a plurality of decoupling units are uniformly arranged at equal intervals in at least one direction.

[0044] Specifically, to ensure that the gain obtained by the self-decoupling coil array used for magnetic resonance imaging is the same at all points in at least one direction, multiple decoupling units are uniformly arranged at equal intervals in at least one direction. When installing the self-decoupling coil array in this direction, it is not necessary to consider the impact of misalignment on imaging. Furthermore, the uniform arrangement of multiple decoupling units at equal intervals in at least one direction allows for direct observation of whether the gain is at the same level during magnetic resonance imaging. If a decoupling unit in the self-decoupling coil array malfunctions, this can be used as a marker to quickly determine the location of the damage.

[0045] In some specific embodiments, multiple decoupling units are arranged in two orthogonal directions.

[0046] It should be noted that multiple decoupling units are arranged in two orthogonal directions, which makes it easier to calculate the gain at each position of the self-decoupling coil array. At the same time, arranging them in two orthogonal directions can adapt to most application scenarios and facilitates the processing and arrangement of the self-decoupling coil array.

[0047] In some more specific embodiments, two resonant coils are positioned opposite each other with a 5 mm gap at the location where the decoupling capacitor is set, thereby forming a decoupling unit. The side length of the resonant coil is 50 mm, and the size of the decoupling capacitor ranges from 1.4 picofarads to 1.9 picofarads.

[0048] It needs to be explained that the decoupling capacitor C inserted in series with the resonant coil in the self-decoupling coil array... mode Its capacitance is very small, allowing for the introduction of additional electrical coupling to counteract the magnetic coupling between opposing resonant coils, thereby reducing the coupling between individual unit loops. As shown in Figure 2, C mode The size of C will control the magnitude of electrical coupling. mode The smaller the value, the greater the electrical coupling. C can be determined through electromagnetic simulation. mode The size of the capacitance value.

[0049] The decoupling capacitor used in the self-decoupling coil array fabricated using the above parameters ranges from 1.4 picofarads to 1.9 picofarads. This is suitable for imaging the knee joint, thus achieving optimal decoupling performance. Preferably, 1.65 picofarads can be used (see Figure 2), as this results in a smaller coupling coefficient between the self-decoupling coils and better decoupling. Preferably, the decoupling capacitor C... mode With a capacitive reactance greater than 200Ω, high-quality decoupling between wireless array channels is achieved.

[0050] In some more specific embodiments, the resonant coil is square in shape.

[0051] In this design, the squares have equal side lengths, ensuring that the distance between any two adjacent detuned resonant loops in two orthogonal directions is the same. For self-decoupling coil arrays requiring bending at varying degrees, the degree of bending is the only parameter affecting the gain, thus facilitating adjustment of the bending degree and the desired high-gain location. In other embodiments, the resonant coils can also be other polygonal shapes.

[0052] In some embodiments, the decoupling unit does not bend along its length.

[0053] Specifically, the length direction of the decoupling unit refers to the direction of the connection between the two decoupling capacitors. In order to avoid changes in the distance between the two decoupling capacitors in the decoupling unit during the bending process, bending should be avoided in the direction of the connection between the two decoupling capacitors to achieve a better decoupling effect.

[0054] In some embodiments, the decoupling units are all disposed on the flexible structure.

[0055] The flexible structure can be made of flexible materials such as cloth or felt, which makes it easier to use the decoupled wireless array.

[0056] In some specific embodiments, the flexible structure is provided with an adhesive structure, which allows adjustment of the size of the imaging area enclosed by the flexible structure. The flexible structure is connected to a shielding structure, which can shield the remaining decoupling units that do not enclose the imaging area, thereby not affecting the normal operation of the enclosed imaging area.

[0057] In some specific embodiments, the flexible structure has at least two detachable structures, allowing the operator to adjust the size appropriately according to the required imaging area.

[0058] In some embodiments, an adjustable capacitor is connected in series with the resonant coil.

[0059] To further optimize the resonant coil structure and reduce the manufacturing cost of the self-decoupling coil array, this application incorporates an adjustable capacitor connected in series with the resonant coil to achieve the tuning state. It should be noted that the detuning circuit and the tuning circuit are not necessarily two distinct circuits; in some embodiments, the detuning circuit and the tuning circuit share a common circuit line.

[0060] In some embodiments, an inductor is connected in series between the decoupling capacitor and the adjustable capacitor.

[0061] Specifically, on the one hand, to prevent the normal tuning of the resonant coil from being affected by using an excessively small decoupling capacitor, an inductor is connected in series between the decoupling capacitor and the adjustable capacitor; on the other hand, to further enhance the decoupling effect of the self-decoupling coil array and to prevent mutual interference between the decoupling capacitor and the adjustable capacitor, an inductor is connected in series between the decoupling capacitor and the adjustable capacitor.

[0062] In some embodiments, the detuned circuit is a parallel LC circuit controlled by two pairs of bidirectional diodes.

[0063] This implementation example uses a parallel LC circuit controlled by two pairs of bidirectional diodes to achieve detuning. Detuning can also be achieved in other ways, such as introducing a new detuning circuit.

[0064] In the description of this specification, the use of terms such as "Embodiment 1," "this embodiment," or "in one embodiment" indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in one or more embodiments or examples.

[0065] In the description of this specification, the terms "connection," "installation," "fixing," "setting," and "having" are interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0066] In the description of this specification, relational terms such as “first” and “second” are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0067] The above description of the embodiments is intended to enable those skilled in the art to understand and apply the technology of this invention. Those skilled in the art can easily make various modifications to these examples and apply the general principles described herein to other embodiments without creative effort. Therefore, this invention is not limited to the above embodiments. Modifications in the following situations should be within the scope of protection of this invention: ① New technical solutions implemented based on the technical solution of this invention and combined with existing common knowledge, where the technical effects of the new technical solution do not exceed the technical effects of this invention; ② Equivalent substitutions of some features of the technical solution of this invention using known technology, resulting in the same technical effects as those of this invention; ③ Extendable technical solutions based on the technical solution of this invention, where the substantive content of the extended technical solution does not exceed the technical solution of this invention; ④ Equivalent transformations made using the content of this specification and drawings, directly or indirectly applied to other related technical fields.

Claims

1. A self-decoupling coil array for magnetic resonance imaging, characterized in that, It includes a resonant coil with a detuned circuit, the resonant coil being connected in series with a decoupling capacitor, two resonant coils being arranged opposite each other at the location where the decoupling capacitor is set to form a decoupling unit, and a plurality of the decoupling units being arranged in at least one direction.

2. The self-decoupling coil array for magnetic resonance imaging according to claim 1, characterized in that, The resonant coil is a passive resonant coil.

3. A self-decoupling coil array for magnetic resonance imaging according to claim 1, characterized in that, No two of the resonant coils overlap.

4. A self-decoupling coil array for magnetic resonance imaging according to claim 3, characterized in that, The decoupling units are evenly arranged at equal intervals in at least one direction.

5. A self-decoupling coil array for magnetic resonance imaging according to claim 4, characterized in that, The decoupling units are arranged in two orthogonal directions.

6. A self-decoupling coil array for magnetic resonance imaging according to claim 5, characterized in that, Two resonant coils are positioned 5 mm apart and opposite each other at the location where the decoupling capacitor is set, thus forming a decoupling unit. The side length of the resonant coil is 50 mm, and the size of the decoupling capacitor ranges from 1.4 picofarads to 1.9 picofarads.

7. A self-decoupling coil array for magnetic resonance imaging according to claim 1, characterized in that, The decoupling unit does not bend along its length in any of the decoupling units.

8. A self-decoupling coil array for magnetic resonance imaging according to any one of claims 1 to 7, characterized in that, The resonant coil is connected in series with an adjustable capacitor.

9. A self-decoupling coil array for magnetic resonance imaging according to claim 8, characterized in that, An inductor is connected in series between the decoupling capacitor and the adjustable capacitor.

10. A self-decoupling coil array for magnetic resonance imaging according to any one of claims 1 to 7, characterized in that, The detuned circuit is a parallel LC circuit controlled by two pairs of bidirectional diodes.

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