Magnetic resonance metamaterial array decoupling connection circuit based on topology connection reconfiguration
By introducing physical conductive bridges and nonlinear adjustment elements into the metamaterial array and reconstructing the circuit topology, the tuning difficulty and coupling problem of the metamaterial array were solved, frequency stability and magnetic field uniformity were improved, and the signal-to-noise ratio of magnetic resonance imaging was enhanced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TIANJIN UNIV
- Filing Date
- 2026-04-09
- Publication Date
- 2026-07-31
AI Technical Summary
Traditional metamaterial arrays in magnetic resonance imaging suffer from problems such as high tuning difficulty, severe inter-unit coupling leading to mode splitting, unstable spectrum, and poor robustness in flexible applications.
By introducing physical conductive bridges to establish a continuous global conductive network between adjacent metamaterial reinforcing units, frequency alignment and high-frequency current protection are achieved using nonlinear adjustment elements and adjustable capacitors, and the circuit topology is reconstructed to eliminate coupling.
This improved the frequency stability and magnetic field uniformity of the metamaterial array, reduced the tuning difficulty, and enhanced the signal-to-noise ratio and magnetic resonance imaging performance.
Smart Images
Figure CN122488005A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of magnetic resonance imaging technology, and in particular to a non-coupled connection circuit for magnetic resonance metamaterial arrays based on topological connection reconstruction. By reconstructing the circuit topology through physical connections, the metamaterial array paradigm shift from discrete units to a continuous circuit network of the array is realized. Background Technology
[0002] Magnetic Resonance Imaging (MRI) is widely used in medical imaging and scientific research due to its advantages such as no ionizing radiation, high resolution, and excellent soft tissue contrast. The intensity of the acquired signal is key to improving image quality. In recent years, the application of metamaterial resonators in MRI has been extensively studied. Due to their ability to enhance local fields, they can effectively improve the signal-to-noise ratio of MRI images. Furthermore, as passive devices, they have advantages such as higher detection flexibility, low cost, and compactness, and are expected to become an effective tool for high-quality imaging.
[0003] Metamaterial arrays are mostly composed of periodically arranged discrete open-loop resonators, helical resonators, and other units. Frontier research on improving the signal-to-noise ratio (SNR) of MRI using metamaterial resonators can be divided into three-dimensional volumetric metamaterial resonators and two-dimensional surface metamaterial resonator arrays. Three-dimensional volumetric metamaterials offer higher local field uniformity and stability, but are limited by structural size and more complex in system integration. Two-dimensional surface metamaterial resonator arrays offer better flexibility and comfort, but are more difficult to design and tune. Traditional metamaterial arrays are physically discrete, and the independence of the units leads to uncontrollable mode splitting caused by near-field coupling. Strong coupling causes the originally uniform unit resonant frequency to split into multiple hybrid modes, resulting in multiple resonance peaks in the spectrum, leading to energy dispersion and an inability to concentrate on the target frequency of MRI. Furthermore, the load on units at different positions in the array and the interference from neighboring units vary, causing inaccurate frequency distribution within the array and making it difficult to achieve synchronous resonance across the entire array.
[0004] Regardless of the form, metamaterial arrays face challenges such as difficult tuning and uncontrollable mode splitting due to severe inter-unit coupling. Furthermore, flexible metamaterial arrays exhibit poor robustness to structural stretching and bending, resulting in significant frequency shifts. These challenges severely hinder the widespread application of metamaterial resonators in clinical testing. Therefore, there is an urgent need to propose a coupling-free connection circuit for magnetic resonance metamaterial arrays based on topological connection reconstruction. Summary of the Invention
[0005] The purpose of this invention is to provide a decoupled connection circuit for magnetic resonance metamaterial arrays based on topology connection reconstruction, thereby solving the problems existing in the prior art. This invention introduces the concept of topology connection reconstruction, connecting adjacent metamaterial enhancer units through physical circuitry, transforming the circuit topology from a separate set into a unified global network, and fusing multiple hybrid modes into a single, coherent global eigenmode. To solve the above-mentioned technical problems, this invention adopts the following technical solution: A non-coupled connection circuit for a magnetic resonance metamaterial array based on topological connection reconstruction is disclosed. The magnetic resonance metamaterial array includes multiple metamaterial intensifier units, each including a dielectric substrate and a helical resonant coil, with the helical resonant coil disposed on the top layer of the substrate. The helical resonant coil has an inner lead-out terminal and an outer lead-out terminal on its outer circumference; these are referred to as the inner lead-out terminal or the outer lead-out terminal, one being the head end and the other the tail end. Multiple metamaterial intensifier units are periodically and repeatedly arranged to form the magnetic resonance metamaterial array. A physical conductive bridge is introduced between adjacent metamaterial intensifier units, as follows: the tail end of the helical resonant coil of the previous unit is electrically connected to the head end of the helical resonant coil of the next unit, and the tail end of the helical resonant coil of the last unit is electrically connected to the head end of the helical resonant coil of the first unit, thereby reconstructing the originally spatially discrete multiple helical resonant coils into a continuous global conductive network in the circuit topology. The physical conductive bridge is a nonlinear tuning circuit, including an impedance adjustment element and a nonlinear switching element connected in parallel with the impedance adjustment element; the impedance adjustment element is used for overall resonant frequency alignment of the array; the nonlinear switching element is used to ensure that the array can passively or actively block high-frequency current to protect the device under test and restore the high conduction state of the network during signal reception.
[0006] Furthermore, the metamaterial intensifier units are arranged in a periodic repeating pattern according to the shape of the target magnetic resonance imaging region.
[0007] Furthermore, the arrangement methods include two-dimensional flat plate arrangements suitable for local enhancement of the body surface, and three-dimensional barrel or conformal arrangements suitable for full-field imaging.
[0008] Furthermore, the impedance adjustment element is an adjustable capacitor; the nonlinear switching element is a detuned circuit composed of cross-connected reverse-parallel diodes.
[0009] Furthermore, by adjusting the capacitance value of the adjustable capacitor in the global conductive network, the conduction current path provided by the physical conductive bridge exhibits a low impedance state at the target magnetic resonance Larmor frequency.
[0010] Furthermore, the adjustable capacitor has high voltage resistance. The capacitance value of the adjustable capacitor is 1-3pF.
[0011] Furthermore, the diode has a low on-state voltage parameter to enable conduction during the radio frequency transmission phase.
[0012] The beneficial effects of this invention are as follows: the introduction of a physical conductive bridging structure between adjacent metamaterial reinforcing units reconstructs multiple spatially discrete helical resonant coils into a continuous global conductive network in the circuit topology; under the provided uncoupled mode implementation method, the array behaves as a whole, eliminating mutual inductance interference between units and fundamentally eliminating mutual influence during tuning; the resonant frequency remains highly stable under flexible bending, stretching, or near different human body loads; the B1 field distribution generated by a single coherent mode has greater global continuity, effectively eliminating field strength attenuation between discrete units and eliminating the need for complex decoupling networks in traditional arrays. Attached Figure Description
[0013] Figure 1 The magnetic resonance metamaterial intensifier unit structure provided in the embodiment of the present invention.
[0014] In the figure, 1-polyimide flexible substrate; 2-artificial skyrmion structure; 3-internal lead-out port; 4-external lead-out port Figure 2 The electrical connection diagram of the uncoupled connection circuit of the magnetic resonance metamaterial array based on topological connection reconstruction of two-dimensional planar arrangement is provided for the embodiments of the present invention.
[0015] Figure 3 The electrical connection diagram of the uncoupled connection circuit of the magnetic resonance metamaterial array based on topological connection reconstruction of three-dimensional barrel arrangement is provided for the embodiments of the present invention.
[0016] Figure 4 Spectral characteristics of traditional discrete unit metamaterial arrays and uncoupled mode metamaterial arrays; Figure 5 For metamaterial arrays with various arrangements, (a) magnetic field diagram of a traditional discrete unit metamaterial array with a two-dimensional planar arrangement; (b) magnetic field diagram of a metamaterial array with a two-dimensional planar arrangement in an uncoupled mode; (c) magnetic field diagram of a traditional discrete unit metamaterial array with a three-dimensional barrel arrangement; (d) magnetic field diagram of a metamaterial array with a three-dimensional barrel arrangement in an uncoupled mode. Figure 6 Comparison of pig hoof imaging images of traditional array connection methods and uncoupled mode metamaterial array connection methods for three-dimensional barrel-shaped metamaterial arrays. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are all within the scope of protection of this invention.
[0018] The basic technical solution of this invention will be described first.
[0019] The present invention discloses a topology-reconstructed, coupling-free connection circuit for a magnetic resonance metamaterial array. The magnetic resonance metamaterial array includes multiple metamaterial intensifier units, each comprising a dielectric substrate and a helical resonant coil, wherein the helical resonant coil is disposed on the top layer of the substrate. The helical resonant coil has an inner lead-out terminal and an outer lead-out terminal on its outer circumference; these are referred to as the inner lead-out terminal or the outer lead-out terminal, one being the head end and the other the tail end. Multiple metamaterial intensifier units are periodically and repeatedly arranged to form the magnetic resonance metamaterial array. A physical conductive bridge is introduced between adjacent metamaterial intensifier units, as follows: the tail end of the helical resonant coil of the preceding unit is electrically connected to the head end of the helical resonant coil of the following unit, and the tail end of the helical resonant coil of the last unit is electrically connected to the head end of the helical resonant coil of the first unit, thereby reconstructing the originally spatially discrete multiple helical resonant coils into a continuous global conductive network in the circuit topology.
[0020] The metamaterial intensifier units are arranged in a periodic repeating pattern according to the shape of the target magnetic resonance imaging region. The arrangement includes a two-dimensional flat plate arrangement suitable for local enhancement of the body surface, and a three-dimensional barrel or conformal arrangement suitable for full-field imaging.
[0021] The physical conductive bridge is a nonlinear tuning circuit, including an impedance adjustment element and a nonlinear switching element connected in parallel with the impedance adjustment element; the impedance adjustment element is used for overall resonant frequency alignment of the array; the nonlinear switching element is used to ensure that the array can passively or actively block high-frequency current to protect the object under test during the transmission of high-power radio frequency pulses by the magnetic resonance system, and restore the high conduction state of the network during signal reception.
[0022] The impedance adjustment element is an adjustable capacitor; the nonlinear switching element is a detuned circuit composed of cross-connected reverse-parallel diodes; by adjusting the capacitance value of the adjustable capacitor in the global conductive network, the conduction current path provided by the physical conductive bridging structure presents a low impedance state at the target magnetic resonance Larmor frequency, and the influence of parasitic displacement current and spatial mutual inductance between adjacent units is reduced.
[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The specific process is as follows: like Figure 1 As shown in the figure, a schematic diagram of a metamaterial enhancer unit structure used in a magnetic resonance metamaterial array uncoupled connection circuit based on topological connection reconstruction provided by an embodiment of the present invention includes a polyimide (PI) flexible substrate 1, an artificial skyrmion structure 2, an inner lead-out port 3, and an outer lead-out port 4.
[0024] The metamaterial reinforcing unit's artificial skyrmion structure has a metal wire width of 2 mm, 5 turns, a turn spacing of 4 mm, and a metal wire thickness of 0.035 mm. The material is copper. The PI substrate has a thickness of 0.1 mm and a relative permittivity of 3.5. This substrate, while ensuring support, also possesses excellent flexibility, enabling it to effectively conform to the detection target and achieve optimal signal-to-noise ratio gain.
[0025] like Figure 2 and Figure 3 The diagram shown is an electrical connection diagram of a magnetic resonance metamaterial array uncoupled connection circuit based on topological connection reconstruction provided by an embodiment of the present invention. Combining flexibility and detection applicability, the metamaterial intensifier units are periodically and repeatedly arranged according to the shape of the target magnetic resonance imaging region. The arrangement includes a two-dimensional flat plate arrangement suitable for local enhancement of the body surface, and a three-dimensional barrel arrangement suitable for full-field imaging.
[0026] This invention provides a topology-reconstructed, uncoupled magnetic resonance metamaterial array circuit by introducing a physical conductive bridge structure between adjacent metamaterial intensifier units. Specific nodes (e.g., external leads) of the spiral resonant coils in one unit are directly electrically connected to specific nodes (e.g., internal leads) of the spiral resonant coils in the next unit. Through this physical conductive bridge structure, the originally spatially discrete spiral resonant coils are reconstructed into a continuous, globally conductive network in the circuit topology.
[0027] The impedance adjustment element is an adjustable capacitor; the nonlinear switching element is a detuned circuit composed of cross-connected reverse-parallel diodes. By adjusting the capacitance value of the adjustable capacitor in the global conductive network, the conduction current path provided by the physical conductive bridging structure exhibits a low impedance state at the target magnetic resonance Larmor frequency, and the effects of parasitic displacement current and spatial mutual inductance between adjacent units are reduced. The physical conduction bridge specifically comprises an integrated parallel circuit of an adjustable capacitor and a reverse-parallel diode. The adjustable capacitor is selected with a high withstand voltage parameter, and the capacitance value is 1-3pF. The diode is selected with a low on-state voltage parameter to achieve conduction during the RF transmission phase. The physical conduction bridge circuit can achieve uniformly adjustable metamaterial frequency and nonlinear enhancement, ensuring that during the transmission of high-power RF pulses by the magnetic resonance system, the array can passively or actively block high-frequency current to protect the device under test, while restoring the network to a high conduction state during signal reception.
[0028] By adjusting the adjustable capacitance value in the physical conductive bridge of the overall metamaterial array, the array can resonate at the Larmor frequency of 1.5T magnetic resonance. The capacitance value in each conductive bridge circuit is controlled to be the same, which greatly reduces the tuning difficulty.
[0029] like Figure 4 The image shows the spectral characteristics of a traditional discrete-unit metamaterial array and an uncoupled metamaterial array. The unit structure used in the traditional discrete-unit metamaterial array is different from that in the uncoupled metamaterial array. Figure 1 In a consistent manner, a nonlinear tuning circuit is added between the inner lead-out port 3 and the outer lead-out port 4, and the resonant frequency of each unit is adjusted to 63.8MHz, and they are periodically and closely arranged into a two-dimensional planar array and a three-dimensional barrel array.
[0030] This network topology enforces strict voltage and current continuity conditions throughout the array, thereby merging and simplifying multiple hybrid split modes in discrete states into a single, coherent global eigenmode. This eliminates coupling disturbances between units at the physical level, achieving a coupling-free operating mode.
[0031] The dielectric substrate is a flexible and bendable substrate (such as polyimide PI); when the two-dimensional flat plate arrangement undergoes spatial bending or stretching deformation, since the resonant frequency of the global intrinsic mode is determined by the topological invariants and global impedance of the continuous conductive network, the central resonant frequency of the metamaterial array remains constant, exhibiting coupling stability characteristics that are immune to geometric deformation. The uncoupled mode is characterized by the fact that in the spectral response of the metamaterial array, the N resonance peaks originally generated by the coupling of N discrete units are merged into a single high-Q resonance peak after topological connection reconstruction, and the frequency of this resonance peak strictly corresponds to the Larmor resonance frequency of the target magnetic resonance system.
[0032] To verify the technical effect of the uncoupled mode proposed in this invention, the spectral scanning of the probe magnetic field strength of the traditional discrete unit metamaterial array and the topology reconstruction uncoupled mode metamaterial array of this invention were compared using full-wave electromagnetic simulation software.
[0033] When using traditional discretely arranged metamaterial arrays, the original degeneracy of the system is disrupted due to strong near-field parasitic mutual inductance and capacitive coupling between adjacent units. Simulation curves show at least 5-6 violently oscillating discrete hybrid resonance peaks (with a maximum field strength of approximately 19.5 A / m) appearing in the 63 MHz to 66 MHz frequency band. This severe "mode splitting" phenomenon causes the radio frequency energy to be dispersed to non-target frequencies, making it impossible to achieve stable and concentrated field enhancement at the Larmor frequency of the 1.5T magnetic resonance, and making it highly susceptible to detuning due to external environmental disturbances. Using the present invention Figure 2 and Figure 3 After the topological reconstruction scheme shown, the establishment of a global conduction path enforces phase locking of the system, and spatial parasitic coupling is completely suppressed by the conduction current. Simulation curves show that the previously chaotic and fragmented multiple resonance peaks are completely eliminated and merged into a single, extremely sharp global intrinsic resonance peak, with its center frequency precisely locked at the target operating frequency of 63.8 MHz for 1.5T MRI. Comparing the peak values of the two sets of curves, it can be seen that after entering the uncoupled mode, since energy is no longer dissipated due to mode splitting, the probe magnetic field strength at the target frequency significantly jumps from the traditional 19.5 A / m to 24.3 A / m. This not only proves the complete elimination of parasitic coupling between units from a physical perspective, but also means that the array can provide MRI with a higher local signal-to-noise ratio (SNR) and a more uniform magnetic field distribution at the clinical application level.
[0034] like Figure 5 As shown, this is a comparison of the normalized magnetic field distribution provided in the embodiments of the present invention. Figure 5 Studies (a,c) and (b,d) show that the magnetic field strength and uniformity are significantly improved after using the topological connection reconstruction scheme for both two-dimensional flat plate arrays and three-dimensional barrel arrays. Due to the severe modal splitting of traditional discrete unit metamaterial arrays, it is difficult to guarantee a stable magnetic field enhancement effect, and different splitting peaks exhibit complex magnetic field distribution patterns.
[0035] like Figure 6 The image shown is a comparison of images of pig hooves imaged in a magnetic resonance imaging (MRI) system using a three-dimensional barrel-shaped metamaterial array provided in an embodiment of the present invention. The experiment was conducted on a commercially available United Imaging 1.5T UMR670 MRI scanner, using a 24-channel head coil as the receiving coil, and employing the T1w_TSE sequence (TR: 480ms, TE: 20ms, FOV: 180mm×180mm, voxel: 0.6mm×0.6mm×3mm). Figure 6 Traditional connected array imaging suffers from uneven enhancement. However, by using a non-coupled metamaterial array connection method, the image uniformity is greatly improved, and uniform enhancement can be achieved in the region of interest.
[0036] Therefore, the non-coupled connection circuit of magnetic resonance metamaterial array based on topological connection reconstruction provided by the present invention can significantly reduce the tuning difficulty of metamaterial array. The embodiments demonstrate the complete elimination of parasitic coupling between units and have a stable enhancement effect in terms of magnetic field strength and uniformity, providing a reliable and stable new method for the clinical application of metamaterials.
[0037] Matters not covered in this invention are common knowledge.
[0038] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A magnetic resonance metamaterial array decoupling connection circuit based on topology connection reconfiguration, characterized in that, The magnetic resonance metamaterial array includes multiple metamaterial intensifier units, each metamaterial intensifier unit including a dielectric substrate and a helical resonant coil, with the helical resonant coil disposed on the top layer of the substrate; The spiral resonant coil has an internal lead-out terminal and an external lead-out terminal on its outer circumference; these are called the internal lead-out terminal and the external lead-out terminal, one being the start end and the other the tail end; multiple metamaterial reinforcing units are periodically and repeatedly arranged to form a magnetic resonance metamaterial array; a physical conductive bridge is introduced between adjacent metamaterial reinforcing units, as follows: the tail end of the spiral resonant coil of the previous unit is electrically connected to the start end of the spiral resonant coil of the next unit, and the tail end of the spiral resonant coil of the last unit is electrically connected to the start end of the spiral resonant coil of the first unit through the physical conductive bridge, thereby reconstructing the originally spatially discrete multiple spiral resonant coils into a continuous global conductive network in the circuit topology; The physical conductive bridge is a nonlinear tuning circuit, including an impedance adjustment element and a nonlinear switching element connected in parallel with the impedance adjustment element; the impedance adjustment element is used for overall resonant frequency alignment of the array. Nonlinear switching elements are used to ensure that the array can passively or actively block high-frequency current to protect the device under test and restore the network to a high conduction state during signal reception.
2. The magnetic resonance metamaterial array decoupling connection circuit of claim 1, wherein, Its features are, The metamaterial intensifier units are arranged in a periodic repeating pattern according to the shape of the target magnetic resonance imaging region.
3. The magnetic resonance metamaterial array decoupling connection circuit of claim 2, wherein, The arrangement methods include two-dimensional flat plate arrangements suitable for local enhancement of the body surface, and three-dimensional barrel or conformal arrangements suitable for full-field imaging.
4. The magnetic resonance metamaterial array decoupling connection circuit of claim 1, wherein, The impedance adjustment element is an adjustable capacitor; the nonlinear switching element is a detuned circuit composed of cross-connected reverse-parallel diodes.
5. The magnetic resonance metamaterial array decoupling connection circuit of claim 4, wherein, By adjusting the capacitance value of the adjustable capacitor in the global conductive network, the conduction current path provided by the physical conductive bridge presents a low impedance state at the target magnetic resonance Larmor frequency.
6. The magnetic resonance metamaterial array decoupling connection circuit of claim 4, wherein, Its features are, Adjustable capacitors have high voltage resistance.
7. The uncoupled connection circuit for magnetic resonance metamaterial arrays according to claim 4, characterized in that, Its features are, The adjustable capacitor has a capacitance of 1-3pF.
8. The magnetic resonance metamaterial array decoupling connection circuit of claim 4, wherein, Its features are, Diodes have low on-state voltage parameters to enable conduction during the radio frequency transmission phase.