CN114910845A

CN114910845A - Magnetic field enhancement assembly and magnetic field enhancement device

Info

Publication number: CN114910845A
Application number: CN202110183925.4A
Authority: CN
Inventors: 赵乾; 池中海; 孟永钢; 郑卓肇; 易懿; 王亚魁
Original assignee: Tsinghua University; Beijing Tsinghua Changgeng Hospital
Current assignee: Tsinghua University; Beijing Tsinghua Changgeng Hospital
Priority date: 2021-02-10
Filing date: 2021-02-10
Publication date: 2022-08-16
Also published as: WO2022170752A1

Abstract

The present application relates to a magnetic field enhancing assembly and a magnetic field enhancing device. The magnetic field enhancement assembly includes a first dielectric layer, a first electrode layer, a second electrode layer, and a fourth control circuit. The first dielectric layer has a first surface. The first dielectric layer has a first end and a second end disposed opposite to each other. The first electrode layer is arranged on the first surface and close to the second end. The second electrode layer is arranged on the first surface, arranged at an interval with the first electrode layer and arranged close to the first end. One end of the fourth control circuit is connected with one end, far away from the first end, of the second electrode layer. The other end of the fourth control circuit is connected with one end, far away from the second end, of the first electrode layer. The fourth control circuit is used for controlling the first electrode layer and the second electrode layer to be disconnected in a radio frequency transmitting stage and to be connected in a radio frequency receiving stage.

Description

Magnetic field enhancement assembly and magnetic field enhancement device

Technical Field

The present application relates to the field of magnetic resonance imaging technology, and in particular, to a magnetic field enhancing assembly and a magnetic field enhancing device.

Background

MRI (Magnetic Resonance Imaging) is a non-invasive detection method, and is an important basic diagnostic technique in the fields of medicine, biology and neuroscience. The strength of the signal transmitted by the traditional MRI equipment is mainly determined by the strength of the static magnetic field B0, and the signal-to-noise ratio and the resolution of the image can be improved and the scanning time can be shortened by adopting a high magnetic field system and even an ultrahigh magnetic field system. However, the increase in the static magnetic field intensity brings about three problems: 1) increased Radio Frequency (RF) field non-uniformity, increased tuning difficulty; 2) the heat production of human tissue increases, brings the potential safety hazard, and adverse reactions such as vertigo and vomiting still appear to the patient easily: 3) the purchase cost is greatly increased, and is a burden for most small-scale hospitals. Therefore, how to use the minimum static magnetic field intensity while obtaining high imaging quality becomes a crucial issue in the MRI technology.

The MRI method is a new trend capable of effectively improving the MRI characteristics, wherein the plate or columnar dielectric harmonic oscillator with high dielectric constant is introduced into the MRI to improve the strength of a radio frequency magnetic field and reduce the specific absorption rate, so that the effects of improving the imaging resolution and reducing the signal to noise ratio are achieved. The advent of metamaterials provides a novel and more efficient method for improving MRI imaging quality and efficiency. Metamaterials have many special properties that are not found in natural materials. The electromagnetic wave propagation path and the electromagnetic field intensity distribution can be controlled by the interaction between the electromagnetic wave and the metal or dielectric elements of the metamaterial and the coupling effect between the elements. The specific working principle is that the adjustment of electromagnetic parameters such as anisotropy and gradient distribution is realized by utilizing electromagnetic resonance in a structure formed by a metamaterial. In addition, through the design of parameters such as geometric dimension, shape, dielectric constant and the like of the metamaterial, the resonance enhancement of different frequency points can be realized.

In a nuclear magnetic resonance system, there are two radio frequency phases: a radio frequency transmitting phase and a radio frequency receiving phase. The radio frequency fields of the radio frequency transmit phase and the radio frequency receive phase have the same resonant frequency. Therefore, the structure formed by the metamaterial can greatly increase the radio frequency transmitting field while enhancing the radio frequency receiving field. At this time, after the radio frequency transmission field is enhanced, the MRI image quality is degraded. However, conventional magnetic field enhancement assemblies include a dielectric plate and first and second electrodes positioned on front and rear surfaces of the dielectric plate, respectively. The orthographic projection of the second electrode on the dielectric plate is positioned at two ends of the orthographic projection of the first electrode on the dielectric plate so as to form a parallel plate capacitor. At this time, the structure of the conventional magnetic field enhancement assembly has only frequency selectivity, so that the magnetic field enhancement assembly exhibits a linear response characteristic, which enhances the radio frequency transmitting field and the radio frequency receiving field simultaneously, resulting in a reduction in MRI image quality.

Disclosure of Invention

In view of the above, it is necessary to provide a magnetic field enhancement assembly and a magnetic field enhancement device.

The present application provides a magnetic field enhancement assembly. The magnetic field enhancement assembly includes a first dielectric layer, a first electrode layer, a second electrode layer, and a fourth control circuit. The first dielectric layer has a first surface. The first dielectric layer has a first end and a second end disposed opposite to each other. The first electrode layer is arranged on the first surface and is close to the second end. The second electrode layer is arranged on the first surface, arranged at an interval with the first electrode layer and arranged close to the first end. One end of the fourth control circuit is connected with one end, far away from the first end, of the second electrode layer, and the other end of the fourth control circuit is connected with one end, far away from the second end, of the first electrode layer. The fourth control circuit is used for controlling the first electrode layer and the second electrode layer to be disconnected in a radio frequency transmitting stage and to be connected in a radio frequency receiving stage.

In the above magnetic field enhancement assembly and magnetic field enhancement device, the second electrode layer and the first electrode layer may be used as transmission lines of the magnetic field enhancement assembly. The fourth control circuit controls connection or disconnection of the second electrode layer and the first electrode layer. The magnetic field enhancement assembly introduces a nonlinear control structure through the fourth control circuit, so that a resonant loop formed by a plurality of magnetic field enhancement assemblies also has nonlinear response characteristics, and the magnetic field enhancement assembly can be applied to all clinical sequences including a fast spin echo sequence. The resonance occurring in the structure formed by the plurality of magnetic field enhancing components is an LC resonance. In LC resonance, the inductance is derived from the transmission line itself formed by the first electrode layer and the second electrode layer, and may be equivalent to an inductance and a resistance. The capacitance in LC resonance arises from the structural capacitance formed between any two electrode layers and the dielectric.

In a radio frequency emission phase, the fourth control circuit controls the first electrode layer to be disconnected from the second electrode layer. The resonance circuit formed by a plurality of magnetic field enhancement components is in an open state and is in a detuned state. In addition, no induction current exists in a resonant loop formed by the magnetic field enhancement components, so that an induction magnetic field which can interfere radio frequency cannot be generated, and the influence of the magnetic field enhancement components on a radio frequency emission stage is eliminated.

And in a radio frequency receiving stage, the fourth control circuit controls the first electrode layer to be connected with the second electrode layer. The resonance loops formed by the magnetic field enhancement components are in a connected state, can present a resonance state, and greatly enhance a signal field. The fourth control circuit controls the first electrode layer and the second electrode layer to be disconnected in a radio frequency transmitting stage and connected in a radio frequency receiving stage, so that the magnetic field enhancement assembly can only enhance a radio frequency receiving field, the radio frequency transmitting field cannot be enhanced, and the image signal to noise ratio is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the description of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the description below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a side view of a magnetic field enhancement assembly in one embodiment provided herein;

FIG. 2 is a side view of a magnetic field enhancement assembly in one embodiment provided herein;

FIG. 3 is a side view of a magnetic field enhancement assembly in one embodiment provided herein;

FIG. 4 is a schematic structural diagram of a magnetic field enhancement assembly of the embodiment of FIG. 3 provided herein;

FIG. 5 is a top view of the magnetic field enhancement assembly of the embodiment of FIG. 3 as provided herein;

FIG. 6 is a schematic structural diagram of an overlapping portion of a first electrode layer and a third electrode layer in an embodiment provided in the present application;

FIG. 7 is a schematic structural diagram of an overlapping portion of a first electrode layer and a third electrode layer in one embodiment provided herein;

FIG. 8 is a side view of a magnetic field enhancement assembly in one embodiment provided herein;

FIG. 9 is a side view of a magnetic field enhancement assembly in one embodiment provided herein;

FIG. 10 is a schematic diagram of the overall structure of the magnetic field enhancement device provided in the present application;

FIG. 11 is a schematic diagram of an exploded view of a magnetic field enhancement device provided herein;

fig. 12 shows the resonant behavior of the magnetic field enhancement device during the rf transmit phase and the rf receive phase.

Description of reference numerals:

the magnetic field enhancement device comprises a magnetic field enhancement assembly 10, a first dielectric layer 100, a first electrode layer 110, a second electrode layer 120, a fourth control circuit 600, a first surface 101, a second surface 102, a first end 103, a second end 104, a first depletion type MOS tube 231, a second depletion type MOS tube 232, a third depletion type MOS tube 233, a fourth depletion type MOS tube 234, a second surface 102, a third electrode layer 130, a second structure capacitor 302, a fourth electrode layer 140, a third structure capacitor 303, a fifth electrode layer 141, a fifth control circuit 610, a sixth control circuit 620, a sixth electrode layer 121, a first opening 401, a second opening 402, a third opening 403, a fourth opening 404, a magnetic field enhancement device 20, a cylindrical support structure 50, a magnetic field enhancement assembly 10, a first annular conductive sheet 510, a second annular conductive sheet 520, a third end 51 and a fourth end 53.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are given in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first resistance may be referred to as a second resistance, and similarly, a second resistance may be referred to as a first resistance, without departing from the scope of the present application. The first resistance and the second resistance are both resistances, but they are not the same resistance.

It is to be understood that "connection" in the following embodiments is to be understood as "electrical connection", "communication connection", and the like if the connected circuits, modules, units, and the like have communication of electrical signals or data with each other.

As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, as used in this specification, the term "and/or" includes any and all combinations of the associated listed items.

Referring to fig. 1, the present application provides a magnetic field enhancement assembly 10. The magnetic field enhancing assembly 10 comprises a first dielectric layer 100, a first electrode layer 110, a second electrode layer 120 and a fourth control circuit 600. The first dielectric layer 100 has a first surface 101. The first dielectric layer 100 has a first end 103 and a second end 104 disposed opposite to each other. The first electrode layer 110 is disposed on the first surface 101. The first electrode layer 110 is disposed proximate to the second end 104. The second electrode layer 120 is disposed on the first surface 101. The second electrode layer 120 is spaced apart from the first electrode layer 110. The second electrode layer 120 is disposed near the first end 103.

One end of the fourth control circuit 600 is connected to one end of the second electrode layer 120 away from the first end 103. The other end of the fourth control circuit 600 is connected to one end of the first electrode layer 110 away from the second end 104. The fourth control circuit 600 is used for controlling the first electrode layer 110 and the second electrode layer 120 to be disconnected in a radio frequency transmitting phase and to be connected in a radio frequency receiving phase.

In this embodiment, the second electrode layer 120 and the first electrode layer 110 can be used as a transmission line of the magnetic field enhancement device 10. The fourth control circuit 600 controls connection or disconnection of the second electrode layer 120 and the first electrode layer 110. The magnetic field enhancement assembly 10 introduces a nonlinear control structure through the fourth control circuit 600, so that the resonant loop formed by a plurality of the magnetic field enhancement assemblies 10 also has a nonlinear response characteristic, and can be applied to all clinical sequences including a fast spin echo sequence. The resonance occurring in the structure formed by a plurality of said magnetic field enhancing assemblies 10 is an LC resonance. In LC resonance, the inductance is derived from the transmission line itself formed by the first electrode layer 110 and the second electrode layer 120, and may be equivalent to an inductance and a resistance. The capacitance in LC resonance results from the structural capacitance formed between any two electrode layers and the dielectric.

In the rf transmitting phase, the fourth control circuit 600 controls the first electrode layer 110 to be disconnected from the second electrode layer 120. The resonant tank formed by a plurality of the magnetic field enhancement assemblies 10 is in an open state and exhibits a detuned state. In addition, no induced current exists in a resonant circuit formed by the plurality of magnetic field enhancement assemblies 10, so that an induced magnetic field which can interfere with radio frequency is not generated, and the influence of the magnetic field enhancement assemblies 10 on a radio frequency transmission stage is eliminated.

In the rf receiving phase, the fourth control circuit 600 controls the first electrode layer 110 to be connected to the second electrode layer 120. The resonance circuit formed by a plurality of the magnetic field enhancement assemblies 10 is in a connection state, and can present a resonance state, thereby greatly enhancing the signal field. The fourth control circuit 600 controls the first electrode layer 110 and the second electrode layer 120 to be disconnected in the radio frequency transmission phase and connected in the radio frequency receiving phase, so that the magnetic field enhancement assembly 10 can only enhance the radio frequency receiving field, the radio frequency transmission field is not enhanced, and the image signal to noise ratio is improved.

The magnetic field enhancement assembly 10 is a MOS transistor based nonlinear response MRI image enhancement super-structured surface device. The MOS tube-based nonlinear response MRI image enhancement super-structure surface device controls the first electrode layer 110 and the second electrode layer 120 to be disconnected in a radio frequency transmitting stage and connected in a radio frequency receiving stage through the fourth control circuit 600. The first electrode layer 110 and the second electrode layer 120 are disconnected in the rf transmission phase and connected in the rf reception phase, so that the magnetic field enhancement assembly 10 can only enhance the rf reception field and does not enhance the rf transmission field. The MOS tube-based nonlinear response MRI image enhancement super-structure surface device has the characteristic of nonlinear response, and cannot enhance a radio frequency transmitting field and a radio frequency receiving field simultaneously.

In one embodiment, the fourth control circuit 600 includes a first depletion type MOS transistor 231 and a second depletion type MOS transistor 232. The source of the first depletion type MOS transistor 231 is connected to the second electrode layer 120. The gate and the drain of the first depletion type MOS transistor 231 are connected. The gate and the drain of the second depletion type MOS transistor 232 are connected. The gate and the drain of the second depletion type MOS transistor 232 are connected to the gate and the drain of the first depletion type MOS transistor 231. The source of the second depletion type MOS transistor 232 is connected to the first electrode layer 110.

In this embodiment, the first depletion type MOS transistor 231 and the second depletion type MOS transistor 232 are connected in series in an opposite direction, so that the first electrode layer 110 and the second electrode layer 120 can be controlled to be disconnected in a radio frequency transmitting phase and connected in a radio frequency receiving phase. The first depletion type MOS tube 231 and the second depletion type MOS tube 232 are connected in series in an opposite direction, so that the ac environment in the MRI apparatus can be adapted. The first depletion type MOS tube 231 and the second depletion type MOS tube 232 are connected in series in an opposite direction, which can ensure that one of the first depletion type MOS tube 231 and the second depletion type MOS tube 232 is cut off in a radio frequency emission phase, so that the first electrode layer 110 and the second electrode layer 120 are disconnected and not connected.

The first depletion type MOS tube 231 and the second depletion type MOS tube 232 have the characteristics of low-voltage conduction and high-voltage cutoff. In addition, the first depletion type MOS tube 231 and the second depletion type MOS tube 232 have a clamping voltage at room temperature of about 1V, and both the off-time and the recovery time are in the order of nanoseconds.

In the MRI apparatus, the radio frequency transmitting phase and the radio frequency receiving phase have a time sequence difference of several tens milliseconds to several thousands milliseconds, and the first depletion type MOS transistor 231 and the second depletion type MOS transistor 232 can be quickly turned on and off. The difference between the radio frequency power in the radio frequency transmitting stage and the radio frequency power in the radio frequency receiving stage is 3 orders of magnitude. The induced voltage in the coil during the radio frequency transmission phase is between a few V and a few hundred V, the specific value depending on the sequence and flip angle chosen.

In a radio frequency transmission phase, an induced voltage is large, the first depletion type MOS tube 231 and the second depletion type MOS tube 232 are in an off state, and a resonant circuit formed by the plurality of magnetic field enhancement components 10 is in an off state and is in a detuned state. Moreover, no current is present in the magnetic field enhancement assembly 10, and no induced magnetic field is generated that would interfere with radio frequencies. In a radio frequency receiving stage, the first depletion type MOS tube 231 and the second depletion type MOS tube 232 are connected, and a plurality of resonant circuits formed by the magnetic field enhancement component 10 are in a connected state, so that a resonant state can be presented, a signal field can be greatly enhanced, and an image signal-to-noise ratio can be enhanced.

The first electrode layer 110, the second electrode layer 120, the third electrode layer 130, and the fourth electrode layer 140 may be made of non-magnetic metal such as copper, silver, gold, or the like. The material of the first dielectric layer 100 may be a flame-retardant material grade FR4, a high-temperature-resistant thermoplastic resin such as polyphenylene oxide (PPE), or a Rogers 4003C material. In one embodiment, the first electrode layer 110, the second electrode layer 120, the third electrode layer 130, and the fourth electrode layer 140 are made of the same material, and are made of copper foil.

In one embodiment, the first dielectric layer 10 has a width of 15mm, a thickness of 0.51mm and a length of 250 mm.

Referring to fig. 2, in an embodiment, the fourth control circuit 600 further includes a third depletion type MOS transistor 233 and a fourth depletion type MOS transistor 234. The source of the third depletion type MOS transistor 233 is connected to the source of the first depletion type MOS transistor 231. The gate and the drain of the third depletion type MOS transistor 233 are connected. The gate and the drain of the fourth depletion MOS transistor 234 are connected. The gate and the drain of the fourth depletion type MOS transistor 234 are connected to the gate and the drain of the third depletion type MOS transistor 233. The source of the fourth depletion MOS transistor 234 is connected to the source of the second depletion MOS transistor 232.

In this embodiment, in the radio frequency receiving stage, the first depletion type MOS transistor 231 and the second depletion type MOS transistor 232 are turned on and equivalently become a resistor. The third depletion type MOS transistor 233 and the fourth depletion type MOS transistor 234 are electrically connected and equivalently become a resistor. The first depletion type MOS tube 231 and the second depletion type MOS tube 232 are connected in series in an opposite direction. The third depletion type MOS transistor 233 and the fourth depletion type MOS transistor 234 are connected in series and in reverse, and are connected in parallel with the first depletion type MOS transistor 231 and the second depletion type MOS transistor 232. At this time, in the radio frequency receiving stage, two resistors are connected in parallel between the second electrode layer 120 and the first electrode layer 110, so that the overall resistance value is reduced, which is more beneficial for the magnetic field enhancement assembly 10 to form a uniform magnetic field, and the MRI image quality is improved.

In one embodiment, the second electrode layer 120 and the first electrode layer 110 are symmetrically disposed about the fourth control circuit 600 along a direction from the first end 103 to the second end 104. That is, the lengths of the second electrode layer 120 and the first electrode layer 110 are the same.

In this embodiment, the fourth control circuit 600 is disposed at an intermediate position of the first dielectric layer 100. The second electrode layer 120 and the first electrode layer 110 may be equivalent to an inductor, and the magnetic field strength is large. The second electrode layer 120 and the first electrode layer 110 are distributed on two sides of the fourth control circuit 600, so that the structure of the magnetic field enhancement assembly 10 is symmetrical. The magnetic field enhancement assembly 10 is structurally symmetrical such that the distribution of the magnetic field enhanced by the magnetic field enhancement assembly 10 exhibits symmetry. In the radio frequency receiving stage, the fourth control circuit 600 controls the first electrode layer 110 to be connected with the second electrode layer 120, so that the distribution of the magnetic field enhanced by the magnetic field enhancement assembly 10 is more uniform, and the MRI image quality is improved.

Referring to fig. 3 and 4, in one embodiment, the first dielectric layer 100 further includes a second surface 102. The second surface 102 is disposed opposite to the first surface 101. The magnetic field enhancement assembly 10 further comprises a third electrode layer 130 and a fourth electrode layer 140. The third electrode layer 130 is disposed on the second surface 102. The third electrode layer 130 covers a portion of the second surface 102. The third electrode layer 130 is disposed proximate to the second end 104. The fourth electrode layer 140 is disposed on the second surface 102. The fourth electrode layer 140 covers a part of the second surface 102. The fourth electrode layer 140 is disposed near the first end 103.

The orthographic projection of the third electrode layer 130 on the first dielectric layer 100 is overlapped with the orthographic projection of the first electrode layer 110 on the first dielectric layer 100, and a second structure capacitor 302 is formed. In the heavily doped portion, the first electrode layer 110, the first dielectric layer 100, and the third electrode layer 130 form the second structured capacitor 302. The orthogonal projection of the fourth electrode layer 140 on the first dielectric layer 100 is overlapped with the orthogonal projection of the second electrode layer 120 on the first dielectric layer 100, so as to form a third structural capacitor 303. In the heavily doped portion, the second electrode layer 120, the first dielectric layer 100, and the fourth electrode layer 140 form the third structured capacitor 303.

The second electrode layer 120 between the third structure capacitor 303 and the fourth control circuit 600 may form a first transmission line. The first electrode layer 110 between the fourth control circuit 600 and the second structure capacitor 302 may form a second transmission line. The third structure capacitor 303, the fourth control circuit 600 and the second structure capacitor 302 are connected in series through a first transmission line and a second transmission line. Therefore, by connecting the third structure capacitor 303, the fourth control circuit 600 and the second structure capacitor 302 in series, the resonant frequency of the resonant circuit formed by the plurality of magnetic field enhancement assemblies 10 can be adjusted, and the adjustment time of the plurality of magnetic field enhancement assemblies 10 after being placed in the mri system is shortened.

The magnetic field enhancement assembly 10 generates an induced voltage in a magnetic field environment. A parasitic capacitance is formed in a transmission line portion formed by the first electrode layer 110 and the second electrode layer 120. The parasitic capacitance is in parallel relationship with the second structure capacitance 302 and the third structure capacitance 303. In a radio frequency receiving stage, the third structure capacitor 303 and the second structure capacitor 302 form a capacitor series structure, and an induced voltage is divided into a plurality of parts, so that the voltage division of the third structure capacitor 303 and the second structure capacitor 302 is reduced.

Further, the third structure capacitor 303 and the second structure capacitor 302 form a capacitor series structure, which can reduce the voltage on the parasitic capacitor. The voltage on the parasitic capacitance is reduced, and the harm of the parasitic capacitance is reduced, so that the load effect is reduced. The load effect of the magnetic field enhancement assembly 10 is reduced, so that the resonant frequency of a resonant circuit formed by a plurality of magnetic field enhancement assemblies 10 is not easily influenced by a tested object, the enhancement performance of the magnetic field enhancement assembly 10 is improved, and the stability of the resonant frequency is enhanced.

In one embodiment, the overlap length is related to the overlap area at the corresponding overlap portion of the third structure capacitor 303. The third structural capacitor 303 and the second structural capacitor 302 both have suitable facing areas, which means that the structural capacitor formed by the second electrode layer 120 and the fourth electrode layer 140 has a suitable value, so that the resonant tank formed by the plurality of magnetic field enhancement assemblies 10 has the same operating frequency as the MRI system.

Wherein the resonant frequency of the resonant tank formed by the plurality of magnetic field enhancement assemblies 10 is determined by

Where L and C are the equivalent inductance and equivalent capacitance, respectively, in the resonant tank formed by the plurality of magnetic field enhancing components 10. The value of the equivalent capacitance is determined by the structural capacitance Cs of each cell. The relation between the structural capacitance Cs and the facing area S of the two electrode plates is

Wherein epsilon ₀ ε represents the relative permittivity of the first dielectric layer 100 for a vacuum permittivity. d is the distance between the two electrode plates (or the thickness of the first dielectric layer 100). Therefore, the appropriate facing area is intended to allow a resonant tank formed by a plurality of the magnetic field enhancing assemblies 10 to have a target resonant frequency, i.e., the same operating frequency as the MRI system.

In one embodiment, the overlapping length of the second electrode layer 120 and the fourth electrode layer 140 at the heavy sum portion of the third structural capacitor 303 is 35 mm. In the heavy portion corresponding to the second structured capacitor 302, the overlapping length of the first electrode layer 110 and the third electrode layer 130 is 35 mm.

In one embodiment, the length of the second electrode layer 120 between the third structural capacitor 303 and the fourth control circuit 600 is the same as the length of the first electrode layer 110 between the second structural capacitor 302 and the fourth control circuit 600. That is, the lengths of the first transmission line and the second transmission line are the same in a direction from the first end 103 to the second end 104.

In this embodiment, the second electrode layer 120 between the third structure capacitor 303 and the fourth control circuit 600 may form the first transmission line. The first electrode layer 110 between the second structure capacitor 302 and the fourth control circuit 600 may form the second transmission line. The first transmission line and the second transmission line may be equivalent to an inductor and a resistor. At this time, the effective magnetic field is distributed between the third structural capacitor 303 and the fourth control circuit 600 and between the second structural capacitor 302 and the fourth control circuit 600. That is, the effective magnetic field is distributed between the first transmission line and the second transmission line. The effective magnetic field between the second structure capacitance 302 and the fourth control circuit 600 forms a first detection region. The effective magnetic field between the third structured capacitor 303 and the fourth control circuit 600 forms a second detection area. The first detection area is the same as the second detection area. The region where the effective magnetic field is formed serves as a detection region for detecting a detection site. In this embodiment, the magnetic field enhancement assembly 10 forms two identical detection regions on the left and right sides of the fourth control circuit 600, which is more beneficial for the magnetic field enhancement assembly 10 to form a uniform magnetic field, and improves the quality of MRI images.

Referring to fig. 5, in an embodiment, a width of the second electrode layer 120 between the third structure capacitor 303 and the fourth control circuit 600 is smaller than a width of the second electrode layer 120 corresponding to the third structure capacitor 303. The width of the first electrode layer 110 between the second structure capacitor 302 and the fourth control circuit 600 is smaller than the width of the first electrode layer 110 corresponding to the second structure capacitor 302. That is, the width of the first transmission line in the direction perpendicular to the first end 103 to the second end 104 is smaller than the width of the second electrode layer 120 corresponding to the third structure capacitor 303. The width of the second transmission line is smaller than the width of the first electrode layer 110 corresponding to the second structure capacitor 302.

In this embodiment, the third structure capacitor 303 is connected to the fourth control circuit 600 through the first transmission line. The second structure capacitor 302 is connected to the fourth control circuit 600 via the second transmission line. However, the electrode layer and the electrode layer corresponding to the transmission line are oppositely disposed to form a stray capacitance. The width of the second electrode layer 120 between the third structure capacitor 303 and the fourth control circuit 600 is reduced, so that the width of the first transmission line is reduced, and the area is reduced when the electrode layer is opposite to the electrode layer. The width of the first electrode layer 110 between the second structure capacitor 302 and the fourth control circuit 600 is reduced, so that the width of the second transmission line is reduced, and the relative area between the electrode layers is reduced.

Through setting up the width of first transmission line with the width of second transmission line makes first transmission line with the second transmission line is relative with other electrode layers, makes just for reducing the area, has reduced the stray capacitance who forms. The width of the first transmission line is smaller than that of the second electrode layer 120 corresponding to the third structure capacitor 303, so that the third structure capacitor 303 can be ensured to fully utilize the area of the second electrode layer 120 to form a structure capacitor, and stray capacitance is reduced. The width of the second transmission line is smaller than the width of the first electrode layer 110 corresponding to the second structural capacitor 302, which not only can ensure that the second structural capacitor 302 fully utilizes the area of the first electrode layer 110 to form a structural capacitor, but also reduces stray capacitance. Therefore, under the condition that the formation of the first structure capacitor 301 and the second structure capacitor 302 is not influenced, and the connection of the first structure capacitor and the second structure capacitor is not influenced, the stray capacitance is reduced, the uniform distribution of a magnetic field is facilitated, and the MRI image quality is improved.

Referring to fig. 6, in an embodiment, the first electrode layer 110 corresponding to the capacitor 302 with the second structure is provided with a first opening 401. The third electrode layer 130 corresponding to the second structure capacitor 302 is provided with a second opening 402. The first opening 401 and the second opening 402 coincide with each other in an orthographic projection of the first dielectric layer 100. That is, the first opening 401 is disposed opposite to the second opening 402 on two opposite surfaces of the first dielectric layer 100.

The orthographic projections of the first opening 401 and the second opening 402 on the first dielectric layer 100 are overlapped, and the overlapped part forms a comb-tooth-shaped shape with one opening, so that the local magnetic field distribution can be further optimized, and the detection effect of a specific position of a detection part is improved.

Referring to fig. 7, in an embodiment, a third opening 403 is formed in the first electrode layer 110 corresponding to the second capacitor structure 302. The third opening 403 is spaced apart from the first opening 401. The third electrode layer 130 corresponding to the second structure capacitor 302 is provided with a fourth opening 404. The fourth opening 404 is spaced apart from the second opening 402. The orthographic projection of the third opening 403 and the fourth opening 404 on the first dielectric layer 100 is overlapped. The first opening 401 and the second opening 402 coincide with each other in an orthographic projection of the first dielectric layer 100. Through the first opening 401, the second opening 402, the third opening 403 and the fourth opening 404, the orthographic projection overlapping part forms a comb-shaped shape with two openings, so that the local magnetic field distribution can be further optimized, and the detection effect of a specific position of a detection part is improved.

In one embodiment, the structure of the second electrode layer 120 corresponding to the third structural capacitor 303 is the same as the structure of the first electrode layer 110 corresponding to the second structural capacitor 302. The fourth electrode layer 140 corresponding to the third structural capacitor 303 and the third electrode layer 130 corresponding to the second structural capacitor 302 have the same structure. The structure of the third structure capacitor 303 is the same as that of the second structure capacitor 302, so that a symmetrical structure is formed.

Referring to fig. 8, in one embodiment, the magnetic field enhancing assembly 10 further includes a fifth electrode layer 141 and a fifth control circuit 610. The fifth electrode layer 141 and the first electrode layer 110 are disposed on the first surface 101 at an interval. And the fifth electrode layer 141 is disposed between the first electrode layer 110 and the second electrode layer 120. One end of the fourth control circuit 600 is connected to one end of the second electrode layer 120. The other end of the fourth control circuit 600 is connected to one end of the fifth electrode layer 141. One end of the fifth control circuit 610 is connected to the other end of the fifth electrode layer 141. The other end of the fifth control circuit 610 is connected to one end of the first electrode layer 110.

In this embodiment, the fifth control circuit 610 is the same as the fourth control circuit 600, and includes the first depletion type MOS transistor 231 and the second depletion type MOS transistor 232 connected in series and in reverse. The fifth control circuit 610 and the fourth control circuit 600 jointly control the first electrode layer 110, the fifth electrode layer 141, and the second electrode layer 120 to be disconnected in the rf transmitting phase and to be connected in the rf receiving phase.

Referring to fig. 9, in one embodiment, the magnetic field enhancement assembly 10 further includes a fifth electrode layer 141, a sixth control circuit 620, and a sixth electrode layer 121. The fifth electrode layer 141 and the first electrode layer 110 are disposed on the first surface 101 at an interval. And the fifth electrode layer 141 is disposed between the first electrode layer 110 and the second electrode layer 120. One end of the fourth control circuit 600 is connected to the other end of the fifth electrode layer 141. The other end of the fourth control circuit 600 is connected to one end of the first electrode layer 110. One end of the sixth control circuit 620 is connected to one end of the fourth electrode layer 140. The sixth electrode layer 121 and the third electrode layer 130 are disposed on the second surface 102 at an interval. And the sixth electrode layer 121 is disposed between the fourth electrode layer 140 and the third electrode layer 130. The other end of the sixth control circuit 620 is connected to one end of the sixth electrode layer 121. The orthographic projection of the sixth electrode layer 121 on the first dielectric layer 100 and the orthographic projection of the fifth electrode layer 141 on the first dielectric layer 100 overlap each other to form a first structural capacitor 301.

In this embodiment, the sixth control circuit 620 is the same as the fourth control circuit 600, and includes the first depletion type MOS transistor 231 and the second depletion type MOS transistor 232 connected in series and in reverse. The first electrode layer 110, the fifth electrode layer 141, the sixth electrode layer 121, and the fourth electrode layer 140 are controlled by the sixth control circuit 620 and the fourth control circuit 600 together to be disconnected in the rf transmitting phase and connected in the rf receiving phase.

The fourth electrode layer 140 between the third structure capacitor 303 and the sixth control circuit 620 forms a third transmission line. The sixth electrode layer 121 between the sixth control circuit 620 and the first structural capacitor 301 forms a fourth transmission line. The fifth electrode layer 141 between the first structure capacitor 301 and the fourth control circuit 600 forms a fifth transmission line. The first electrode layer 110 between the fourth control circuit 600 and the second structure capacitor 302 forms a sixth transmission line. The third structure capacitor 303, the sixth control circuit 620, the first structure capacitor 301, the fourth control circuit 600, and the second structure capacitor 302 are connected in series through the third transmission line, the fourth transmission line, the fifth transmission line, and the sixth transmission line. The magnetic field enhancement assembly 10 includes a plurality of series connected structural capacitors.

In a radio frequency receiving stage, the third structure capacitor 303, the first structure capacitor 301, and the second structure capacitor 302 form a capacitor series structure, which divides an induced voltage into a plurality of voltages, and reduces the voltage division of the third structure capacitor 303, the first structure capacitor 301, and the second structure capacitor 302.

Further, the third structure capacitor 303, the first structure capacitor 301 and the second structure capacitor 302 form a capacitor series structure, which reduces the voltage on the parasitic capacitor connected in parallel with the third structure capacitor. The voltage on the parasitic capacitance is reduced, and the harm of the parasitic capacitance is reduced, so that the load effect is reduced. The load effect of the magnetic field enhancement assembly 10 is reduced, so that the resonant frequency of the resonant circuit formed by the magnetic field enhancement assemblies 10 is not easily affected by the tested object, the enhancement performance of the magnetic field enhancement assembly 10 is improved, and the stability of the resonant frequency is enhanced.

Referring to fig. 10 and 11, in one embodiment, the present application provides a magnetic field enhancement device 20. The magnetic field enhancement device 20 comprises a cylindrical support structure 50, a plurality of magnetic field enhancement assemblies 10, a first annular conductive sheet 510 and a second annular conductive sheet 520. The cylindrical support structure 50 has two spaced, opposing third and fourth ends 51, 53. The plurality of magnetic field enhancement assemblies 10 are spaced apart from the cylindrical support structure 50. The plurality of magnetic field enhancement assemblies 10 extend along the third end 51 toward the fourth end 53. The first annular conductive tab 510 is disposed on the cylindrical support structure 50. The first annular conductive plate 510 is adjacent to the third end 51. The first annular conductive sheet 510 is connected to the second electrode layer 120 of each magnetic field enhancement assembly 10. The second annular conductive strip 520 is disposed on the cylindrical support structure 50. The second annular conductive strip 520 is proximate the fourth end 53. The second annular conductive sheet 520 is connected to the first electrode layer 110 of each magnetic field enhancement assembly 10.

In one embodiment, the first annular conductive sheet 510 is connected to the second electrode layer 120 of each of the magnetic field enhancement assemblies 10. The second annular conductive sheet 520 is connected to the first electrode layer 110 of each magnetic field enhancement assembly 10.

In one embodiment, the material of the first annular conductive sheet 510 and the second annular conductive sheet 520 may be gold, silver, copper, or other metal material.

In one embodiment, the first annular conductive sheet 510 is connected to the fourth electrode layer 140 of each magnetic field enhancement assembly 10. The second annular conductive sheet 520 is connected to the third electrode layer 130 of each magnetic field enhancement assembly 10.

The cylindrical support structure 50 has an inner surface and an outer surface disposed in spaced relation. The inner surface of the cylindrical support structure 50 may enclose a detection space 509. The detection space 509 may be used to accommodate a detection site. The detection site may be an arm, leg, abdomen, or the like. The plurality of magnetic field enhancement assemblies 10 are equally spaced to improve local magnetic field uniformity.

A plurality of the magnetic field enhancement assemblies 10 may be disposed at equal intervals on the outer surface of the cylindrical support structure 50. The first conductive annular sheet 510 and the second conductive annular sheet 520 are disposed at opposite ends of the cylindrical support structure 50, respectively, and are disposed around the axis 504 of the cylindrical support structure 50.

Both ends of each magnetic field enhancement assembly 10 are respectively connected with the first annular conductive sheet 510 and the second annular conductive sheet 520. The plurality of magnetic field enhancement assemblies 10 are connected by the first and second annular

conductive sheets

510 and 520. The first annular conductive sheet 510 and the second annular conductive sheet 520 are respectively connected end to end, so that the whole structure of the magnetic field enhancement device 20 is isotropic, and the magnetic field uniformity is improved.

The first and second annular

conductive sheets

510 and 520 may be respectively disposed around the axis 504 of the cylindrical support structure 50, i.e., the first and second annular

conductive sheets

510 and 520 are both annular structures.

In one embodiment, a plurality of retaining structures 530 are spaced around the outer surface of the cylindrical support structure 50. In a direction along the third end 51 to the fourth end 53, each of the magnetic field enhancement assemblies 10 corresponds to the position-limiting structure 530 of the third end 51 and the position-limiting structure 530 of the fourth end 53, respectively. One of the magnetic field enhancing assemblies 10 is fixed by the limiting structures 530 at the two ends of the third end 51 and the fourth end 53, so that the magnetic field enhancing assembly 10 is fixed on the outer surface of the cylindrical supporting structure 50.

In one embodiment, the limiting structure 530 may be a through groove. The through slots may be used for inserting the magnetic field enhancing assembly 10. The two through slots respectively limit the two ends of the magnetic field enhancement assembly 10. The magnetic field enhancement assembly 10 can be secured to the outer surface of the cylindrical support structure 50 by the retention structure 530.

In one embodiment, the magnetic field enhancement device 20 may include 12 magnetic field enhancement assemblies 10 equally spaced about the axis 504 on the outer surface of the cylindrical support structure 50.

Referring to fig. 12, fig. 12 shows the resonant behavior of the magnetic field enhancement device 20 during the rf transmit phase and the rf receive phase. As can be seen from fig. 12, the magnetic field enhancing device 20 has a good resonant frequency in the rf receiving stage, and can greatly enhance the rf receiving field and improve the image signal-to-noise ratio. In the radio frequency transmission phase of the magnetic field enhancement device 20, the magnetic field enhancement assembly 10 is disconnected by the fourth control circuit 600, so that the resonant tank formed by a plurality of the magnetic field enhancement assemblies 10 is disconnected. The magnetic field enhancement device 20 has no resonance performance, and no current, and does not induce a magnetic field, thereby ensuring that the intensity of the radio frequency magnetic field after the magnetic field enhancement device 20 is added is the same as that before the addition. Therefore, the fourth control circuit 600 controls the first electrode layer 110 and the second electrode layer 120 to be disconnected in the rf transmission phase and connected in the rf receiving phase, so that the magnetic field enhancement assembly 10 can only enhance the rf receiving field, and does not enhance the rf transmission field, thereby improving the image signal-to-noise ratio.

In the description herein, references to "some embodiments," "other embodiments," "desired embodiments," or the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent application shall be subject to the appended claims.

Claims

1. A magnetic field enhancement assembly, comprising:

a first dielectric layer (100) having a first surface (101), the first dielectric layer (100) having a first end (103) and a second end (104) disposed opposite;

a first electrode layer (110) disposed on the first surface (101) and disposed proximate to the second end (104);

a second electrode layer (120) disposed on the first surface (101), spaced apart from the first electrode layer (110), and disposed proximate to the first end (103);

a fourth control circuit (600), wherein one end of the fourth control circuit (600) is connected with one end, away from the first end (103), of the second electrode layer (120), and the other end of the fourth control circuit (600) is connected with one end, away from the second end (104), of the first electrode layer (110);

the fourth control circuit (600) is used for controlling the first electrode layer (110) and the second electrode layer (120) to be disconnected in a radio frequency transmitting phase and connected in a radio frequency receiving phase.

2. The magnetic field enhancing assembly of claim 1, wherein the fourth control circuit (600) comprises:

a first depletion MOS tube (231), wherein the source electrode of the first depletion MOS tube (231) is connected with the second electrode layer (120), and the grid electrode and the drain electrode of the first depletion MOS tube (231) are connected;

the grid electrode and the drain electrode of the second depletion type MOS tube (232) are connected, the grid electrode and the drain electrode of the second depletion type MOS tube (232) are connected with the grid electrode and the drain electrode of the first depletion type MOS tube (231), and the source electrode of the second depletion type MOS tube (232) is connected with the first electrode layer (110).

3. The magnetic field-enhancing assembly of claim 2, wherein the fourth control circuit (600) further comprises:

a third depletion MOS tube (233), wherein the source electrode of the third depletion MOS tube (233) is connected with the source electrode of the first depletion MOS tube (231), and the grid electrode and the drain electrode of the third depletion MOS tube (233) are connected;

the grid electrode and the drain electrode of the fourth depletion MOS tube (234) are connected, the grid electrode and the drain electrode of the fourth depletion MOS tube (234) are connected with the grid electrode and the drain electrode of the third depletion MOS tube (233), and the source electrode of the fourth depletion MOS tube (234) is connected with the source electrode of the second depletion MOS tube (232).

4. The magnetic field enhancing assembly according to claim 1, wherein the second electrode layer (120) and the first electrode layer (110) are symmetrically arranged with respect to the fourth control circuit (600) in a direction from the first end (103) to the second end (104).

5. The magnetic field enhancement assembly according to claim 1, wherein the first dielectric layer (100) has a second surface (102) disposed opposite the first surface (101), the magnetic field enhancement assembly further comprising:

a third electrode layer (130) disposed on the second surface (102), covering a portion of the second surface (102), and disposed near the second end (104);

the orthographic projection of the third electrode layer (130) on the first dielectric layer (100) is overlapped with the orthographic projection of the first electrode layer (110) on the first dielectric layer (100), and a second structural capacitor (302) is formed;

a fourth electrode layer (140) disposed on the second surface (102), covering a portion of the second surface (102), and disposed near the first end (103);

the orthographic projection of the fourth electrode layer (140) on the first dielectric layer (100) is partially overlapped with the orthographic projection of the second electrode layer (120) on the first dielectric layer (100), and a third structural capacitor (303) is formed.

6. The magnetic field enhancing assembly according to claim 5, wherein the length of the second electrode layer (120) between the third structural capacitance (303) and the fourth control circuit (600) and the length of the first electrode layer (110) between the second structural capacitance (302) and the fourth control circuit (600) are the same along the direction from the first end (103) to the second end (104).

7. The magnetic field enhancement assembly according to claim 5, wherein the width of the second electrode layer (120) between the third structure capacitance (303) and the fourth control circuit (600) is smaller than the width of the second electrode layer (120) corresponding to the third structure capacitance (303);

the width of the first electrode layer (110) between the second structure capacitor (302) and the fourth control circuit (600) is smaller than the width of the first electrode layer (110) corresponding to the second structure capacitor (302).

8. The magnetic field enhancing assembly according to claim 5, wherein the first electrode layer (110) corresponding to the second structural capacitor (302) is provided with a first opening (401), the third electrode layer (130) corresponding to the second structural capacitor (302) is provided with a second opening (402), and the first opening (401) coincides with an orthographic projection of the second opening (402) on the first dielectric layer (100).

9. The magnetic field enhancing assembly according to claim 8, wherein the first electrode layer (110) corresponding to the second structural capacitor (302) is provided with a third opening (403), the third opening (403) being spaced apart from the first opening (401);

a fourth opening (404) is formed in the third electrode layer (130) corresponding to the second structure capacitor (302), and the fourth opening (404) and the second opening (402) are arranged at intervals;

the third opening (403) and the fourth opening (404) coincide in an orthographic projection of the first dielectric layer (100).

10. A magnetic field enhancement device, comprising:

a cylindrical support structure (50) having two spaced, opposed third (51) and fourth ends (53);

a plurality of magnetic field enhancing assemblies (10), each of said magnetic field enhancing assemblies (10) comprising:

the fourth control circuit (600) is used for controlling the first electrode layer (110) and the second electrode layer (120) to be disconnected in a radio frequency transmitting phase and connected in a radio frequency receiving phase;

the plurality of magnetic field enhancement assemblies (10) are arranged at intervals on the cylindrical supporting structure (50) and extend along the third end (51) to the fourth end (53);

a first annular conductive sheet (510) disposed on said cylindrical support structure (50) near said third end (51), said first annular conductive sheet (510) being connected to said second electrode layer (120) of each said magnetic field enhancement assembly (10); and

a second annular conductive sheet (520) disposed on the cylindrical support structure (50) and proximate to the fourth end (53), the second annular conductive sheet (520) being connected to the first electrode layer (110) of each magnetic field enhancement assembly (10).