META-STRUCTURE FOR IMPEDANCE MATCHING FOR MULTI-LAYERED OR NON-UNIFORM BARRIERS, ULTRASONIC PROBE INCLUDING THE SAME, AND ULTRASONIC IMAGING DEVICE INCLUDING THE SAME

Abstract

In a meta-structure for impedance matching for a multi-layer or non-uniform barrier, an ultrasound probe including the same, and an ultrasound imaging diagnostic device including the same, the meta-structure is disposed in a medium disposed between an ultrasound transducer and a multi-layer barrier, spaced a predetermined matching distance from a surface of the multi-layer barrier toward the ultrasound transducer, and is configured to minimize a difference between the surface impedance at the matching distance and the characteristic impedance of the medium.

Description

[Technical Field]

[0001] The present invention relates to a metastructure for impedance matching for a multilayer or non-uniform barrier, an ultrasound probe including the same, and an ultrasound imaging diagnostic device including the same, and more particularly to a metastructure for impedance matching for a multilayer or non-uniform barrier for imaging a detection target area that exists beyond a multilayer or non-uniform barrier having different impedance properties, such as a skull, an ultrasound probe including the same, and an ultrasound imaging diagnostic device including the same. [Background technology]

[0002] Metamaterials use periodic artificial structures to realize wave properties that are difficult for natural materials to possess, such as zero refractive index and negative refractive index. Research on metamaterials, which was previously active in the electromagnetic field, has recently moved to the acoustic field, and research on acoustic metamaterials using the wave properties of acoustic waves is becoming active.

[0003] For example, acoustic metamaterials can be used to locally concentrate sound into areas smaller than the wavelength, freely change its propagation path, and improve the image quality of sound waves and ultrasound imaging. To achieve this, it is essential to develop a design technology for artificial structures that can freely adjust the elastic modulus, density, and refractive index by periodically arranging structures smaller than the wavelength.

[0004] Recently, research has been conducted on so-called metasurfaces, metamaterial layers, and metastructures, which are created by arranging unit structures designed through physical principles on two-dimensional thin films.

[0005] Meanwhile, the skull, which is a bone tissue that protects the brain, is a connective tissue hardened by calcium and has a multi-layered structure with cortical bone sandwiched between trabecular bone and layered on the inside and outside. Cortical bone is a relatively dense hard tissue, while trabecular bone is a relatively loose, porous soft tissue. In other words, since cortical bone and trabecular bone have different physical properties as well as different thicknesses, the skull forms a multi-layered barrier against ultrasound transmission.

[0006] In this way, the skull, which is made up of multi-layer barrier structures such as cortical bone and cancellous bone, has high reflectivity and low transmittance due to the difference in impedance at the interface between each barrier structure during medical ultrasound imaging using ultrasound or treatment using focused ultrasound.

[0007] Furthermore, existing metasurfaces, metamaterial layers, and metastructures basically match impedance at the interface of a single barrier by quarter-wavelength (λ) matching. In the case of a multi-layer barrier, such as the skull, which has cortical and cancellous bone, multiple effective impedances at the interface of the multi-layer barrier must all be considered, making it difficult to design impedance matching with high transmittance.

[0008] Furthermore, since the thickness and physical properties of the layers of the skull that make up the cancellous bone and cortical bone vary from person to person, matching individual impedances becomes even more difficult.

[0009] Meanwhile, an ultrasound imaging diagnostic device uses an ultrasound transducer to convert an electrical signal into mechanical vibrations and transmits ultrasound waves, receives the signals reflected back from the target object, converts them into electrical signals, and processes the signals to convert them into images.

[0010] Conventionally, an ultrasound probe used in an ultrasound imaging diagnostic device basically consists of a lens, a front material, a piezoelectric element (ultrasonic transducer), and a rear material. Here, the front material plays a role in matching the impedance difference between the ultrasound transducer and the soft tissue of the human body. Therefore, it can be difficult to transmit and receive ultrasound signals through barriers that have a large impedance difference with the soft tissue of the human body, such as bones and gas (air layers present in the digestive tract).

[0011] Furthermore, even if the impedance of the front surface material is matched to the bones of the human body using the existing matching method (a 1 / 4 wavelength (λ) thick impedance matching layer), it is difficult for the ultrasound generated by the probe to first penetrate soft tissues such as human skin. As a result, the technology of the existing ultrasound probe front surface material is difficult to apply to obtaining images of internal soft tissues of the human body by penetrating bones.

[0012] Related prior art documents include Korean Patent Registration No. 10-2093248. Summary of the Invention [Problem to be solved by the invention]

[0013] In order to solve the above-mentioned problems, the object of the present invention is to provide a meta-structure for impedance matching of a multi-layer barrier, which can maximize transmittance by calculating the effective impedance of a multi-layer barrier such as a skull as a surface impedance, regardless of the number of barrier layers or the number of boundary surfaces, rather than by expressing the effective impedance of each barrier as a characteristic impedance of each layer.

[0014] Another object of the present invention is to provide a meta-structure for impedance matching of a multi-layer barrier having a semi-resonant vibration mode capable of realizing impedance matching for the multi-layer barrier.

[0015] Another object of the present invention is to provide a metastructure for impedance matching of a non-uniform barrier having a semi-resonant vibration mode that can implement impedance matching for a non-uniform barrier having different physical properties not only in the ultrasound transmission direction but also in a direction crossing the ultrasound transmission direction.

[0016] Another object of the present invention is to provide a meta-structure for impedance matching of a non-uniform barrier, which can maximize the overall ultrasonic transmittance by performing zone-by-zone impedance matching for the non-uniform barrier.

[0017] Furthermore, another object of the present invention is to provide a metastructure for impedance matching of a multi-layer barrier or a non-uniform barrier, in which design variables such as thickness and matching distance can be set based on the ultrasonic intensity reflected or transmitted by the multi-layer barrier.

[0018] A further object of the present invention is to provide an ultrasonic probe including the above-mentioned metastructure.

[0019] It is another object of the present invention to provide an ultrasound imaging diagnostic apparatus and method including the above-mentioned ultrasound probe. [Means for solving the problem]

[0020] To achieve the above-mentioned object, the meta-structure according to the present invention is characterized in that it is arranged in a medium between an ultrasonic transducer and a multilayer barrier, at a predetermined matching distance from the surface of the multilayer barrier toward the ultrasonic transducer, and is arranged so as to minimize the difference between the surface impedance at the matching distance and the characteristic impedance of the medium.

[0021] The meta-structure is provided so as to have a semi-resonant mode in which the magnitude of the positive direction vibration mode and the magnitude of the negative direction vibration are substantially the same as each other in the natural vibration mode.

[0022] The metastructure includes a first material layer having a first elastic modulus and a first density, and a second material layer having a second elastic modulus and a second density, the first material layer and the second material layer being stacked in the direction of ultrasonic transmission, and the first elastic modulus and the second elastic modulus being different from each other, or the first densities and the second densities being different from each other.

[0023] The second material layer is disposed on both the front and rear surfaces of the first material layer in the ultrasonic transmission direction.

[0024] The second material layer includes a pattern portion having a first region that exposes the first material layer to the outside and a second region that covers the first material layer without exposing it.

[0025] A plurality of them are tiled relative to one another in a direction transverse to the direction of ultrasound transmission.

[0026] The multilayer barrier includes a first metastructure positioned a first matching distance away from the surface of the multilayer barrier, and a second metastructure positioned a second matching distance away from the surface of the multilayer barrier that is different from the first matching distance.

[0027] To achieve the above object, the meta-structure according to the present invention is characterized in that it is arranged in a medium provided between an ultrasonic transducer and a multilayer barrier, at a predetermined matching distance from the surface of the multilayer barrier toward the ultrasonic transducer, and is arranged so as to minimize the reflection coefficient of a system transfer matrix formed by the product of transfer matrices expressed by the characteristic impedance and phase change of each of the meta-structure, the medium, and the multilayer barrier arranged at the matching distance.

[0028] The reflection coefficient of the system transfer matrix is ​​minimized by the matching distance or the thickness of the meta-structure.

[0029] The multilayer barrier has an impedance that is at least twice the impedance of the medium material, or has an impedance that is substantially the same as the characteristic impedance of the multilayer barrier, so that the range of change of the system transfer matrix is ​​widened by deepening the multiple internal reflections of the ultrasound propagating between the multilayer barrier and the medium material.

[0030] To achieve the above object, the metastructure according to the present invention is characterized in that it includes a first metastructure disposed in an intermediary material disposed between an ultrasonic transducer and a barrier, and spaced a first matching distance from a first surface region of the barrier toward the ultrasonic transducer, so as to minimize the difference between a first surface impedance and the characteristic impedance of the intermediary material at the first matching distance, and a second metastructure disposed a second matching distance from a second surface region of the barrier adjacent to the first surface region toward the ultrasonic transducer, so as to minimize the difference between a second surface impedance and the characteristic impedance of the intermediary material at the second matching distance.

[0031] The first metastructure has a first effective radiation area corresponding to the first surface area, and the second metastructure has a second effective radiation area corresponding to the second surface area, and the first effective radiation area and the second effective radiation area each have a width smaller than 1 / 2 wavelength (λ).

[0032] To achieve the above object, the metastructure according to the present invention is characterized in that it includes a first metastructure arranged in an intermediary material arranged between an ultrasonic transducer and a barrier, and arranged at a first matching distance from a first surface region of the barrier toward the ultrasonic transducer, so as to minimize the reflection coefficient of a first system transfer matrix formed by the product of a first transfer matrix represented by the characteristic impedance and phase change of each of the first metastructure, the intermediary material, and the barrier arranged at the first matching distance, and a second metastructure arranged at a second matching distance from a second surface region of the barrier adjacent to the first surface region toward the ultrasonic transducer, so as to minimize the reflection coefficient of a second system transfer matrix formed by the product of a second transfer matrix represented by the characteristic impedance and phase change of each of the second metastructure, the intermediary material, and the barrier arranged at the second matching distance.

[0033] The first metastructure includes a 1-1 metastructure positioned a 1-1 matching distance away from the first surface region, and a 1-2 metastructure positioned a 1-2 matching distance away from the first surface region, the 1-2 matching distance being different from the 1-1 matching distance.

[0034] The first meta-structure has an impedance that is at least twice as high as the impedance of the intermediary material or substantially the same as the characteristic impedance of the barrier, so as to deepen the multiple internal reflections of the ultrasound propagating between it and the barrier and thereby widen the range of variation of the first system transfer matrix.

[0035] To achieve the above object, an ultrasonic probe according to the present invention includes the meta-structure and an ultrasonic transducer that provides ultrasonic waves to the meta-structure.

[0036] The meta-structure moves in the direction of ultrasound transmission relative to the multi-layer barrier.

[0037] To achieve the above object, an ultrasonic probe according to the present invention includes the meta-structure and an ultrasonic transducer that provides ultrasonic waves to the meta-structure.

[0038] The first meta-structure or the second meta-structure is moved in an ultrasonic transmission direction relative to the ultrasonic transducer.

[0039] To achieve the above object, the ultrasound imaging diagnostic device according to the present invention is characterized by including the meta-structure, an ultrasound transducer that provides ultrasound to the meta-structure, a signal processing unit that processes signals received from the ultrasound transducer to generate an ultrasound image, and a meta-structure control unit that controls at least one of the physical properties, thickness, and matching distance of the meta-structure based on the ultrasound image generated by the signal processing unit. [Effects of the Invention]

[0040] According to the present invention, substantially 100% transmission of ultrasound can be achieved through a multi-layered or heterogeneous barrier.

[0041] Furthermore, by adjusting the matching distance of the meta-structure or adjusting the physical properties of the meta-structure, such as its elastic modulus or pattern portion, the environmental conditions of the multilayer barrier can be actively addressed, allowing ultrasound to pass through efficiently.

[0042] Furthermore, ultrasonic waves can be transmitted efficiently despite not only differences in the physical properties of the skull from person to person but also differences in the physical properties at different positions.

[0043] In addition, the meta-structure can be widely used in medical ultrasound imaging diagnosis and treatment, which uses ultrasound to penetrate into multi-layered tissues containing materials with different impedances, such as bone tissue, soft tissue, and gas, as well as in various non-destructive testing industries, which use ultrasound to penetrate multi-layered physical barriers containing solids (metals, ceramics, plastics) or fluids (composite materials, insulation materials, rust and sludge in pipes, etc.). [Brief explanation of the drawings]

[0044] [Figure 1] FIG. 1 is a conceptual diagram for explaining the surface impedance generated in an intermediate material disposed between an ultrasonic transducer and a multilayer barrier when ultrasonic waves are incident from the ultrasonic transducer toward the multilayer barrier in an ultrasonic probe to which a metastructure according to one embodiment of the present invention is applied. [Figure 2] FIG. 2 is a schematic diagram illustrating the process of determining the position of the surface impedance located in the water medium when ultrasound is incident from the ultrasound transducer toward the water medium and the skull of the multi-layer barrier in the ultrasound probe of FIG. 1. [Figure 3] FIG. 3 is a schematic diagram illustrating impedance matching of a metamaterial having an effective surface density disposed in the water medium when ultrasound is incident from the ultrasound transducer toward the water medium and the skull of the multi-layer barrier in the ultrasound probe of FIG. 1. [Figure 4] 4a to 4c are side and perspective views of the meta-structure of FIG. [Figure 5] FIG. 5 is a graph showing transmittance for each frequency when the meta-structure of FIG. 4a is applied and when the meta-structure is not applied. [Figure 6] FIG. 6 is a perspective view showing a meta-structure according to another embodiment of the present invention. [Figure 7] FIG. 7 is a schematic diagram showing a state in which a meta-structure according to still another embodiment of the present invention is applied. [Figure 8] Fig. 8a is a schematic diagram showing a state in which a meta-structure according to yet another embodiment of the present invention is applied, which is a schematic diagram showing a meta-structure for impedance matching to a barrier having a porous structure, and Fig. 8b is a schematic diagram showing a state in which the porous structure in the multilayer barrier in Fig. 8a is approximated by a uniform material. [Figure 9]Figure 9a is an image showing the simulation results of improving ultrasound transmission when applying an impedance matching meta-structure to a barrier having the porous structure of Figure 8a, and Figure 9b is a graph showing how the pressure distribution changes along the right boundary line of Figure 9a due to the porous structure of the meta-structure of Figure 8a. [Figure 10] FIG. 10 is a schematic diagram showing a multi-layer impedance matching meta-structure for a multi-layer barrier according to yet another embodiment of the present invention. [Figure 11] FIG. 11 shows the wavelength characteristics of the surface impedance at a position a matching distance away from the surface of a non-uniform barrier whose physical properties change continuously in a direction intersecting the ultrasonic transmission direction. [Figure 12] FIG. 12 is a schematic diagram showing a meta-structure according to still another embodiment of the present invention. [Figure 13] FIG. 13 is a schematic diagram showing a meta-structure according to still another embodiment of the present invention. [Figure 14] FIG. 14 is a graph showing impedance matching conditions for designing the A1 layer of FIG. [Figure 15] FIG. 15 is a graph showing impedance matching conditions for designing the A2 layer of FIG. [Figure 16] FIG. 16 shows the simulation results showing the transmittance before applying the meta-structure. [Figure 17] FIG. 17 shows a simulation result showing transmittance after applying a meta-structure according to an embodiment of the present invention. [Figure 18] FIG. 18 is a block diagram showing an ultrasonic probe according to the prior art. [Figure 19] Figure 19a is a block diagram showing an ultrasound probe according to yet another embodiment of the present invention, Figure 19b is a block diagram showing an ultrasound probe according to yet another embodiment of the present invention, and Figure 19c is a block diagram showing an ultrasound probe according to yet another embodiment of the present invention. [Figure 20]FIG. 20 is a block diagram for explaining control of a meta structure in an ultrasonic probe according to still another embodiment of the present invention. [Figure 21] FIG. 21 is a block diagram showing a conventional ultrasound imaging diagnostic apparatus. [Figure 22] FIG. 22 is a block diagram showing an ultrasound imaging apparatus according to still another embodiment of the present invention. [Figure 23] FIG. 23 is a block diagram illustrating an operation method of the ultrasound imaging diagnostic apparatus of FIG. [Figure 24] FIG. 24 is a flowchart illustrating an operation method of the ultrasound imaging diagnostic apparatus of FIG. 22, that is, an ultrasound imaging diagnostic method. [Figure 25] 25a and 25b are graphs showing the change in the insertion position and reflectivity due to the repeated control of the meta-structure in the operating method of the ultrasound imaging diagnostic apparatus of FIG. [Explanation of symbols]

[0045] 1: Ultrasonic transducer 2: Barrier

[0046] 3: Mediator 10, 10', 20, 30, 50: Metastructure

[0047] 11: First meta structure 12: Second meta structure

[0048] 40: Porous multi-layer barrier 41: Outer layer (outer cortex) within the multilayer barrier

[0049] 42: Porous structure within multilayer barrier 43: Inner layer (outer cortex) within the multilayer barrier

[0050] 60, 61, 62: Background medium 63: Target

[0051] 70: Ultrasonic transducer 80: Ultrasonic transmission signal

[0052] 81: Transmitting Directional Ultrasound 82: Barrier-penetrating ultrasound

[0053] 83: Target reflection signal 84: Directional ultrasonic reception

[0054] 85: Ultrasonic received signal 86: Distance between meta structure and barrier

[0055] 100: (conventional) ultrasound probe 101, 411, 421: Lenses

[0056] 102, 413: Front material

[0057] 103, 414, 423, 502: Ultrasonic transducers (piezoelectric elements)

[0058] 104, 415, 424: Rear material 110: Ultrasonic transmitter / receiver

[0059] 120: Transmit pulse generator 130: Analog-to-digital converter

[0060] 140: Transmission and reception convergence unit 150: Intermediate signal processing section

[0061] 160: Video Processing Unit 161: B-mode imaging department

[0062] 162: Blood flow Doppler signal and imaging unit

[0063] 300, 410, 420, 500: (Meta)Ultrasonic Probes

[0064] 301, 412, 422, 501: Metastructures 350: Specific details for implementing the meta-structure control unit invention

[0065] The present invention will be described below with reference to the accompanying drawings. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. In addition, to clearly illustrate the present invention in the drawings, parts that are not relevant to the description will be omitted, and similar parts will be designated by similar reference numerals throughout the specification.

[0066] Throughout this specification, when a part is said to be "connected (connected, contacted, or coupled)" to another part, this includes not only "directly connected" but also "indirectly connected" through another member in between. Furthermore, when a part is said to "include" a certain component, this does not mean that it excludes other components, but that it can also include other components, unless otherwise specified to the contrary.

[0067] The terms used in this specification are merely used to describe specific embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless otherwise clearly intended in the context. In this specification, the terms "comprise" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but should be understood not to preclude the presence or possible addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0068] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0069] FIG. 1 is a conceptual diagram for explaining the surface impedance generated in an intermediate material disposed between an ultrasonic transducer and a multilayer barrier when ultrasonic waves are incident from the ultrasonic transducer toward the multilayer barrier in an ultrasonic probe to which a metastructure according to one embodiment of the present invention is applied.

[0070] As shown in FIG. 1, the meta-structure 10 according to the present embodiment is used in an ultrasound probe and an ultrasound imaging diagnostic apparatus including the ultrasound probe.

[0071] Here, the ultrasonic probe transmits ultrasonic waves through the multi-layer barriers 2, which basically have different physical properties, to generate an ultrasonic image of the detection target area existing beyond the multi-layer barrier 2. In this regard, the meta-structure 10 can be said to be an impedance matching meta-structure that basically performs impedance matching with respect to the barrier boundary surface when generating an ultrasonic image of the area existing beyond the barrier structure.

[0072] Generally, impedance matching is performed at the interface of a single barrier by quarter wavelength (λ) matching. However, this type of impedance matching is difficult to apply to multi-layer barriers, such as the skull, which has cortical and cancellous bones. That is, since multiple effective impedances at the interface of a multi-layer barrier must all be taken into consideration, there are many difficulties in designing an impedance matching system that achieves substantially 100% transmittance.

[0073] In contrast, in this embodiment, the effective impedance of the multilayer barrier 2 is not expressed as the characteristic impedance for each barrier layer, but is calculated as the surface impedance regardless of the number of layers of the barrier 2, i.e., the number of boundary surfaces, and impedance matching is performed.

[0074] JPEG2025532427000002.jpg20169

[0075] JPEG2025532427000003.jpg24169

[0076] This allows ultrasonic waves to be transmitted through the multi-layer barriers having different physical properties at a rate of substantially 100%, thereby generating a high-resolution image of the detection target area that exists beyond the multi-layer barrier 2.

[0077] The surface impedance means a value obtained by dividing the negative pressure on a surface by the particle velocity when a plane sound wave is incident perpendicularly on the surface.

[0078] JPEG2025532427000004.jpg17169

[0079] [Formula 1]

number

[0080] JPEG2025532427000006.jpg16169

[0081] JPEG2025532427000007.jpg20169

[0082] In this case, the mediator 3 is water or a substance having a characteristic impedance similar to that of water.

[0083] Here, in the case of this embodiment, by considering the surface impedance as a representative physical property of the multilayer barrier 2, the characteristic impedance of the barrier is directly considered as in the case of conventional complementary metamaterials, and as the number of layers of the multilayer barrier 2 increases, there is no need to introduce additional metamaterial layers to offset the inherent characteristic impedance of each layer.

[0084] That is, although the surface impedance in this embodiment is naturally related to the intrinsic characteristic impedance of each layer of the multilayer barrier 2, it can be calculated as a single representative value without introducing an additional metamaterial layer to offset the intrinsic characteristic impedance of each layer.

[0085] FIG. 2 is a schematic diagram illustrating the process of determining the position of the surface impedance located in the water medium when ultrasound is incident from the ultrasound transducer toward the water medium and the skull of the multi-layer barrier in the ultrasound probe of FIG. 1.

[0086] JPEG2025532427000008.jpg21169

[0087] [Formula 2]

number

[0088] [Formula 2-1]

number

[0089] [Formula 2-2]

number

[0090] [Formula 2-3]

number

[0091] [Formula 2-4]

number

[0092] [Formula 2-5]

number

[0093] [Formula 2-6]

number

[0094] [Formula 2-7]

number

[0095] [Formula 2-8]

number

[0096] JPEG2025532427000018.jpg19169

[0097] JPEG2025532427000019.jpg12168

[0098] JPEG2025532427000020.jpg11168

[0099] JPEG2025532427000021.jpg31169

[0100] For reference, the intermediate substance water and the outer cortical bone, cancellous bone, and inner cortical bone of the skull have physical properties as shown in Table 1 below.

[0101] [Table 1]

[0102] FIG. 3 is a schematic diagram illustrating impedance matching of a metamaterial having an effective surface density disposed in the water medium when ultrasound is incident from the ultrasound transducer toward the water medium and the skull of the multi-layer barrier in the ultrasound probe of FIG. 1.

[0103] JPEG2025532427000023.jpg15169

[0104] [Formula 3-1]

number

[0105] JPEG2025532427000025.jpg15169

[0106] [Formula 3-2]

number

[0107] JPEG2025532427000027.jpg1147

[0108] JPEG2025532427000028.jpg16169

[0109] [Formula 3-3]

number

[0110] JPEG2025532427000030.jpg15169

[0111] [Formula 3-4]

number

[0112] JPEG2025532427000032.jpg1045

[0113] JPEG2025532427000033.jpg17165

[0114] [Formula 3-5>

number

[0115] JPEG2025532427000035.jpg19161

[0116] [Formula 3-6]

number

[0117] JPEG2025532427000037.jpg13165

[0118] JPEG2025532427000038.jpg16165

[0119] [Formula 3-7]

number

[0120] JPEG2025532427000040.jpg18164

[0121] [Formula 3-8]

number

[0122] JPEG2025532427000042.jpg11165

[0123] JPEG2025532427000043.jpg13165

[0124] [Formula 3-9>

number

[0125] JPEG2025532427000045.jpg17165

[0126] JPEG2025532427000046.jpg25165

[0127] JPEG2025532427000047.jpg26165

[0128] JPEG2025532427000048.jpg20165

[0129] JPEG2025532427000049.jpg29165

[0130] The meta-structure 10 thus fabricated can be manufactured to have a semi-resonant mode in which the magnitude of the positive and negative vibrations in the natural vibration mode is substantially the same, and ultrasonic waves can be transmitted through the multi-layer barrier at substantially 100%.

[0131] JPEG2025532427000050.jpg31165

[0132] 4a to 4c are side and perspective views of the meta-structure of FIG.

[0133] As shown in FIGS. 4 a to 4 c , the meta-structure 10 includes a first material layer 11 and a second material layer 13 .

[0134] The first substance layer 11 and the second substance layer 13 are stacked on top of each other along the direction of transmission of the ultrasonic waves.

[0135] Here, the first material layer 11 has a first elastic modulus, a first density, and a first thickness. Also, the second material layer 13 has a second elastic modulus, a second density, and a second thickness. Here, the first elastic modulus and the second elastic modulus may be different from each other, and the first elastic modulus may be greater than the second elastic modulus. Alternatively, the first density and the second densities may be different from each other.

[0136] That is, the first and second elastic moduli may be different from each other and the first and second densities may be the same from each other, the first and second elastic moduli may be the same from each other and the first and second densities may be different from each other, or the first and second elastic moduli may be different from each other and the first and second densities may be different from each other.

[0137] The first and second thicknesses may be the same or different, and the total thickness of the metastructure 10, which is the sum of the first and second thicknesses, may be relatively very small compared to the wavelength.

[0138] In this way, the layered structure of the first material layer 11 and the second material layer 13 allows the metastructure 10 to efficiently satisfy the semi-resonant mode.

[0139] Furthermore, by adjusting the relative difference between the first and second elastic moduli, the relative difference between the first and second densities, or the relative difference between the first and second thicknesses, it is possible to change the semi-resonant mode of the metastructure 10. That is, by appropriately adjusting the semi-resonant mode of the metastructure 10 so as to correspond to the surface impedance at the surface 2a of the multilayer barrier 2, ultrasonic waves can be efficiently transmitted through the multilayer barrier 2 under various environmental conditions.

[0140] Meanwhile, as described above, the meta-structure 10 includes a first material layer 11 and a second material layer 13, and as shown in FIG. 4a, a pair of second material layers 13 are arranged on both sides (front and back) of the first material layer 11, sandwiching the first material layer 11 therebetween.

[0141] In this case, as shown in Figures 4b and 4c, the second material layer 13 has a patterned portion, which is provided as a first region 13a and a second region 13b.

[0142] The first region 13a is a region that exposes the first material layer 11 to the outside, and the second region 13b is a region that blocks the first material layer 11 so that the first material layer 11 is not exposed.

[0143] For example, the pattern unit may be radially arranged with a center point as a reference in the direction of transmission of ultrasound. That is, although the pattern unit is shown to be formed in a cloverleaf shape or an X-shape in FIGS. 4b and 4c, the shape of the pattern unit is not particularly limited. However, the first region 13a and the second region 13b included in the pattern unit may have symmetrical shapes with respect to the center of the pattern unit. The pattern unit may also be arranged in the first material layer 11 as well as the second material layer 13. The pattern unit formed in the first material layer 11 may have the same pattern as or a different pattern from the pattern formed in the second material layer 13.

[0144] As described above, the pattern portion can more efficiently realize the semi-resonant mode of the metastructure 10.

[0145] Furthermore, by appropriately modifying the design of the pattern portion, the semi-resonant mode of the metastructure 10 can be appropriately adjusted, allowing ultrasonic waves to efficiently pass through the multilayer barrier 2 under various environmental conditions.

[0146] 4a to 4c, when a pair of second material layers 13 are disposed on both sides (front and back) of the first material layer 11, the first material layer 11 is made of PI (polyimide) and the second material layer 13 is made of Cu (copper). In this case, the first thickness of the first material layer 11 is 12 um to 25 um, and the second thickness of the second material layer 13 is 9 um to 75 um.

[0147] JPEG2025532427000051.jpg26165

[0148] FIG. 5 is a graph showing transmittance for each frequency when the meta-structure of FIG. 4a is applied and when the meta-structure is not applied.

[0149] That is, as shown in Figure 5, when the meta-structure 10 according to this embodiment is applied to a frequency range where the transmittance is relatively low when the meta-structure is not applied, it was confirmed that the transmittance increases sharply in the corresponding frequency range.

[0150] Meanwhile, as described above, the metastructure 10 is designed to have a predetermined operating frequency, but the operating frequency of the metastructure 10 can be actively changed. For example, by applying a thermal or electrical external force to the first material layer 11 or the second material layer 13, at least one physical property of the first material layer 11 or the second material layer 13, such as the elastic modulus, thickness, or pattern portion, can be changed, thereby changing the overall operating frequency of the metastructure 10. As a result, by actively adjusting the operating frequency of the metastructure 10 in response to the surface impedance at the surface 2a of the multilayer barrier 2, ultrasound can be efficiently transmitted through the multilayer barrier 2 depending on environmental conditions.

[0151] FIG. 6 is a perspective view showing a meta-structure according to another embodiment of the present invention.

[0152] As shown in Figure 6, the meta structure 20 according to this embodiment includes a plurality of unit meta structures 21, which are tiled in a direction intersecting the ultrasonic transmission direction to form the meta structure 20. That is, a plurality of unit meta structures 21 are so-called tiled in a first direction and a second direction perpendicular thereto to form a single meta structure group, which constitutes the meta structure 20. Here, the tiled arrangement means that n*m (n and m are natural numbers) unit meta structures 21 are arranged adjacent to each other by being arranged in the first direction and the second direction.

[0153] Here, each unit meta-structure 21 can be configured in the same manner as the meta-structure 10 described with reference to FIGS. 4a to 4c.

[0154] Here, adjacent unit meta structures 21 can be physically coupled together, so that the semi-resonant modes of each unit meta structure 21 can be linked together, or adjacent unit meta structures 21 can be physically separated, so that the semi-resonant modes of each unit meta structure 21 can be realized independently.

[0155] Furthermore, each unit meta structure 21 can be designed to have a different operating frequency, thereby achieving a broadband effect for the entire meta structure group 20. Of course, each unit meta structure 21 constituting the entire meta structure group 20 can also be designed to have the same operating frequency, in which case the operating frequency of each unit meta structure 21 can be actively changed in response to the surface impedance at the surface of the multilayer barrier, as described above.

[0156] FIG. 7 is a schematic diagram showing a state in which a meta-structure according to still another embodiment of the present invention is applied.

[0157] As shown in FIG. 7, the meta-structure 30 according to this embodiment includes a first meta-structure 31 and a second meta-structure 32 along the ultrasonic transmission direction.

[0158] Here, the first meta structure 31 and the second meta structure 32 can be configured in the same manner as the meta structure 10 described with reference to FIGS. 4a to 4c.

[0159] JPEG2025532427000052.jpg20168

[0160] JPEG2025532427000053.jpg21168

[0161] JPEG2025532427000054.jpg18168

[0162] JPEG2025532427000055.jpg32168

[0163] JPEG2025532427000056.jpg25168

[0164] In addition, in the case of the meta-structure, if the matching distance of the meta-structure is adjusted to correspond to the surface impedance at the surface of the multilayer barrier, or if the physical properties of the meta-structure, such as the elastic modulus or pattern portion, are adjusted, the environmental conditions of the multilayer barrier can be actively addressed, allowing ultrasound to pass through efficiently.

[0165] FIG. 8a is a schematic diagram showing a state in which a meta-structure according to yet another embodiment of the present invention is applied, and is a schematic diagram showing a meta-structure for impedance matching with respect to a barrier having a porous structure.

[0166] In this embodiment, a meta-structure can be provided that determines the thickness and insertion position (matching distance) of the meta-structure by measuring the intensity of ultrasound reflected or transmitted through the multilayer barrier. This can facilitate impedance matching for multilayer barriers with non-uniform porous structures, for which surface impedance calculation is difficult.

[0167] Specifically, FIG. 8 a is a schematic diagram showing an impedance matching meta-structure 50 for a barrier 40 having a dense outer or outer cortex layer 41, an inner porous structure 42, and an even denser inner or inner cortex layer 43.

[0168] 8a, ultrasonic waves 80 generated by the ultrasonic transducer 70 pass through the meta-structure 50 and propagate as ultrasonic waves 81 in the transmission direction, passing through the medium 61 between the meta-structure 50 and the barrier 40. Here, a reflected ultrasonic wave 84 in the reception direction is generated due to the difference in impedance between the barrier 40 and the medium 61. In this case, by appropriately selecting the physical properties (impedance) and thickness of the meta-structure 50, the distance 86 between the barrier 40 and the medium 61, and the distance 87 between the meta-structure 50 and the transducer, the interference between the transmitted and received ultrasonic waves 81 and 84 placed between the meta-structure 50 and the barrier 40 can be adjusted, thereby maximizing the barrier-transmitted ultrasonic waves 82.

[0169] Here, the theoretical perfect ultrasonic non-reflection condition and perfect ultrasonic transmission condition, which do not take into account attenuation due to scattering and absorption, are expressed by the following formulas 4-1a and 4-1b, respectively.

[0170] [Formula 4-1a]

number

[0171] [Formula 4-1b]

number

[0172] Here, R means the reflectivity of the multilayer system consisting of the meta-structure, intermediate medium and barrier, and is defined as the ratio of the amplitude (pressure length or displacement length) B of the ultrasound reflected by the system to the amplitude (pressure length or displacement length) A of the ultrasound incident on the system, and T means the ultrasound transmittance of the system, and is defined as the ratio of the amplitude C of the ultrasound that passes through the system to the amplitude A of the ultrasound that incident on the system.

[0173] The following equations 4-2a and 4-2b express the amplitudes of the incident and reflected ultrasonic waves in the incident medium of the multilayer system when they are the amplitude of the pressure length (commonly used in acoustics) and the amplitude of the particle displacement length (v) (commonly used in elasticity), respectively.

[0174] [Formula 4-2a]

number

[0175] [Formula 4-2b]

number

[0176] Also, in FIG. 8a, the impedance matching phenomenon is reciprocal, so the barrier transmittance of the reflected echo signal 83 of the object 63 can be increased, and finally, the ultrasonic reception signal 85 including the signal of the object 63 arrives at the ultrasonic transducer 70 again and is converted into an electrical signal, which can be used for image processing.

[0177] JPEG2025532427000061.jpg28168

[0178] JPEG2025532427000062.jpg23164

[0179] [Formula 4-3a]

number

[0180] [Formula 4-3b]

number

[0181] JPEG2025532427000065.jpg19164

[0182] [Formula 4-4a]

number

[0183] [Formula 4-4b]

number

[0184] [Formula 4-4c]

number

[0185] JPEG2025532427000069.jpg15164

[0186] JPEG2025532427000070.jpg16164

[0187] [Formula 4-5a]

number

[0188] [Formula 4-5b]

number

[0189] [Formula 4-5c]

number

[0190] JPEG2025532427000074.jpg15164

[0191] JPEG2025532427000075.jpg27164

[0192] JPEG2025532427000076.jpg20164

[0193] JPEG2025532427000077.jpg31164

[0194] [Formula 4-6a]

number

[0195] [Formula 4-6b]

number

[0196] To apply the minimum reflection or maximum transmission condition in Equation 4-1, the pressure length and particle velocity length of the ultrasonic wave must be expressed in terms of the amplitude variables of the incident, transmitted, and reflected ultrasonic waves of the multilayer system. If the amplitude of the ultrasonic wave is the amplitude of the pressure length, it can be expressed as Equation 4-7 below using the well-known linear Euler equation.

[0197] [Formula 4-7a]

number

[0198] [Formula 4-7b]

number

[0199] [Formula 4-7c]

number

[0200] JPEG2025532427000083.jpg19164

[0201] [Formula 4-8]

number

[0202] Equations 4-8 above can serve as starting points for designing and efficiently finding the properties, thickness, and location of meta-structures that improve the ultrasonic transmission of the multilayer system.

[0203] Figure 8b is a schematic diagram illustrating the approximation of the porous structure 42 in the multilayer barrier of Figure 8a with a homogeneous material 44. This may provide yet another way to efficiently find the properties, thickness, and location of the meta-structure of the present invention to improve the ultrasound transmission of the multilayer system.

[0204] FIG. 9a is an image showing the simulation verification result that ultrasound transmission is improved when the impedance matching meta-structure is applied to the barrier having the porous structure of FIG. 8a.

[0205] In FIG. 9a, the barrier 40 has the same configuration as in FIG. 8a, and the meta-structure 50 located on the left side of the barrier 40 has an appropriate thickness or is located at an appropriate distance from the barrier 40.

[0206] JPEG2025532427000085.jpg40164

[0207] [Formula 4-8a]

number

[0208] [Formula 4-8b]

number

[0209] [Formula 4-8c]

number

[0210] The above equation is derived by simultaneously combining the results of Equation 4-6 and Equation 4-7, and can be applied to any system including a multilayer barrier and a meta-structure.

[0211] JPEG2025532427000089.jpg21164

[0212] In Fig. 9a, the thickness of the meta-structure 50 verified in the simulation was about 4 mm, and the distance from the multi-layer barrier 40 was about 10 mm. In Fig. 9a, the ultrasonic generator on the left side is omitted, and when the average pressure was calculated at the right boundary line 95, it was found that the pressure increased by about three times or more when the meta-structure 50 was present compared to when the meta-structure was not present.

[0213] FIG. 9b is a graph illustrating how the porous structure of the meta-structure of FIG. 8a alters the pressure distribution along the right border of FIG. 9a.

[0214] As shown in Figure 9b, the pressure distribution along the right boundary line 95 is uneven due to the porous structure 42, but it can be seen that the pressure length in the presence of the meta-structure 50 is larger than that in the absence of the meta-structure. The physical properties of the multilayer barrier 40 used in the simulation were two to four times larger than the characteristic impedance of the background medium.

[0215] On the other hand, knowledge of the porous structure within the multilayer barrier can facilitate meta-structure design using known homogenization methods, such as the transfer matrix pressure length or transmission coefficient, reflection coefficient, or simplified simulation model, as shown in Figure 8b.

[0216] FIG. 10 is a schematic diagram showing a multi-layer impedance matching meta-structure for a multi-layer barrier according to yet another embodiment of the present invention.

[0217] That is, Figure 10 is a schematic diagram showing a multilayer meta-structure (A1, A2, ..., AN layers) for multilayer impedance matching for multilayer barriers, which facilitates finding impedance matching conditions for N-layer barriers (B1, B2, ..., BN layers) such as the skull, scalp, meninges, etc.

[0218] For perfect ultrasound transmission through the multilayer barrier, the physical properties of the multilayer metastructure can be arranged in mirror symmetry with those of the multilayer barrier, which satisfies the impedance matching condition of Equation 5-1 and the phase matching condition of Equation 5-1b.

[0219] [Formula 5-1a]

number

[0220] [Formula 5-1b]

number

[0221] JPEG2025532427000092.jpg19164

[0222] [Formula 5-2a]

number

[0223] [Formula 5-2b]

number

[0224] JPEG2025532427000095.jpg28164

[0225] [Formula 5-3a]

number

[0226] [Formula 5-3b]

number

[0227] JPEG2025532427000098.jpg20161

[0228] [Formula 5-4]

number

[0229] On the other hand, if it is difficult to know the actual number of barrier layers or if it is too many, and therefore it is difficult to determine or fabricate the number of layers of the meta-structure, by inserting a smaller number of meta-structures and adjusting their relative positions, the transfer matrix (or scattering matrix) of the entire system can be adjusted to minimize reflectance and maximize transmittance, as described in the previous embodiment.

[0230] For example, the design conditions for inserting two meta-structures to enhance ultrasonic multilayer barrier transmission can be expressed by the transfer matrix described above, as shown in the following equation 5-5.

[0231] [Formula 5-3]

number

[0232] JPEG2025532427000101.jpg39164

[0233] The physical properties (characteristic impedance) of the meta-structure that provides impedance matching to the multilayer barrier were verified by simulation as shown in Figures 9a and 9b. As a result, in order to obtain the effect of improving ultrasound transmission, the meta-structure should have an impedance at least twice as large as that of the background medium. It is advantageous for impedance matching if the physical properties are similar to or larger than those of the multilayer barrier. This is because it is easy to adjust the transfer matrix of the entire multilayer system by deepening the multiple internal reflections between the meta-structure and the multilayer barrier.

[0234] In addition, the meta-structure in this embodiment may have vibration modes such as monopole, dipole, quadrupole, etc., and may have negative mass or negative stiffness characteristics. The role of the meta-structure having the corresponding vibration mode or negative physical properties is to adjust the transfer matrix of the entire multi-layer system and minimize the ultrasonic reflectivity, as described above, thereby providing the same function.

[0235] Meanwhile, the meta-structure 10 according to the embodiment described in FIGS. 1 and 2 has been described as providing impedance matching for the structure of the multi-layer barrier 2 whose physical properties change discontinuously along the direction in which the ultrasound passes.

[0236] In contrast, Figure 11 shows the wavelength characteristics of the surface impedance at a matching distance from the surface of a non-uniform barrier whose physical properties change continuously in a direction intersecting the ultrasonic transmission direction.

[0237] JPEG2025532427000102.jpg28164

[0238] FIG. 12 is a schematic diagram showing a meta-structure according to still another embodiment of the present invention.

[0239] JPEG2025532427000103.jpg40164

[0240] Specifically, the meta-structure 10' includes a first meta-structure 11' and a second meta-structure 12'.

[0241] The first meta-structure 11' and the second meta-structure 12' are disposed in an intermediary material 3 provided between the ultrasonic transducer 1 and the multilayer barrier 2, and are arranged adjacent to each other along the second direction (D2).

[0242] JPEG2025532427000104.jpg26164

[0243] JPEG2025532427000105.jpg24164

[0244] JPEG2025532427000106.jpg31164

[0245] JPEG2025532427000107.jpg25164

[0246] As a result, the first surface impedance due to the first meta-structure 11' and the second surface impedance due to the second meta-structure 12' can cause different physical property changes in the first surface region 2a and the second surface region 2b of the multi-layer barrier 2, making it possible to realize high transmittance for the non-uniform barrier 2.

[0247] On the other hand, the first effective radiation area 11a of the first metastructure 11' and the second effective radiation area 12a of the second metastructure 12' can each be designed and arranged to have a width smaller than the wavelength (λ).

[0248] Like the skull (cancellous bone), the multilayer barrier 2 basically has physical properties (density, porosity, etc.) that change continuously in the second direction (D2) that intersects the first direction (D1) in which ultrasound passes.Taking this into consideration, the width of the first effective radiation area 11a of the first metastructure 11' and the second effective radiation area 12a of the second metastructure 12' can be set to be smaller than the wavelength (λ), thereby reducing the deviation in surface impedance within each effective radiation area.

[0249] Preferably, the first effective radiation area 11a of the first metastructure 11' and the second effective radiation area 12a of the second metastructure 12' are set to be smaller than 1 / 2 wavelength (λ).

[0250] Of course, the continuously changing physical properties (density, porosity, etc.) of the non-uniform barrier 2 can change at least one of the matching distance, physical properties, and effective radiation area of ​​the first meta-structure layer 11' or the second meta-structure layer 12', thereby allowing ultrasonic waves to efficiently pass through the non-uniform barrier 2 under various environmental conditions.

[0251] JPEG2025532427000108.jpg26164

[0252] FIG. 13 is a schematic diagram showing a meta-structure according to still another embodiment of the present invention.

[0253] That is, in the case of the meta-structure according to this embodiment, the thickness and insertion position of the meta-structure can be determined by measuring the intensity of ultrasound reflected or transmitted through a barrier having non-uniform thickness and physical properties. This facilitates impedance matching for a multi-layer barrier having a non-uniform porous structure, which makes it difficult to calculate the surface impedance.

[0254] Fig. 14 is a graph showing impedance matching conditions for designing the A1 layer in Fig. 13. Fig. 15 is a graph showing impedance matching conditions for designing the A2 layer in Fig. 13.

[0255] Specifically, as shown in Figures 13 to 15, in the meta-structure according to this embodiment, the barriers B1 (14a), B2 (14b), and B4 (14d) are made of aluminum, and the barriers B3 (14c) and B5 (14e) are made of stainless steel. The thicknesses of the barriers are set as follows: B1 = 1.2 mm, B2 = 1.0 mm, B3 = 1.3 mm, B4 = 1.7 mm, and B5 = 1.2 mm. The background medium 15 is assumed to be water. The effective physical properties, such as effective density, effective Young's modulus, and thickness, are obtained through impedance matching for each barrier zone.

[0256] Here, the physical property values ​​corresponding to each barrier, the background medium 15, and the meta-structure (impedance matching layer) A1 (16a) are as follows:

[0257] JPEG2025532427000109.jpg11164

[0258] JPEG2025532427000110.jpg11164

[0259] JPEG2025532427000111.jpg11164

[0260] JPEG2025532427000112.jpg11164

[0261] [Formula 6-1]

number

[0262] [Formula 6-2]

number

[0263] [Formula 6-3]

number

[0264] [Formula 6-4]

number

[0265] JPEG2025532427000117.jpg21164

[0266] JPEG2025532427000118.jpg30167

[0267] JPEG2025532427000119.jpg17167

[0268] JPEG2025532427000120.jpg29167

[0269] The effective physical properties and dimensions of each meta-structure A3 (16c), A4 (16d), and A5 (16e), calculated in the same manner as in the design of meta-structure A2 (16b), are as follows:

[0270] JPEG2025532427000121.jpg13167

[0271] JPEG2025532427000122.jpg12167

[0272] JPEG2025532427000123.jpg12167

[0273] Fig. 16 shows a simulation result indicating transmittance before applying a meta structure, and Fig. 17 shows a simulation result indicating transmittance after applying a meta structure according to an embodiment of the present invention.

[0274] To confirm the ultrasonic transmission performance of the meta-structure, we used the commonly used simulation program COMSOL Multiphysics. The calculated effective physical properties and dimensions of each meta-structure layer were applied to the model, and the ultrasonic transmission pressure before and after applying the meta-structure are shown in Figure 16 and Figure 17, respectively.

[0275] As shown in FIG. 16, before applying the meta-structure, a pressure of 1 Pa at 500 kHz is applied to the vibration section 16, and an incident wave 17 passes through an inhomogeneous barrier 19 to form a transmitted wave 18.

[0276] As shown in Figure 17, after applying the meta-structure, a pressure of 500 kHz and 1 Pa is similarly applied to the vibration unit 20, and a meta-structure layer 22 is placed in front of the non-uniform barrier 23, and the ultrasonic incident wave 21 passes through the meta-structure 24 and the non-uniform barrier 23 to form a transmitted wave 22.

[0277] As shown in Figures 16 and 17, the waveforms before and after the meta-structure are similar, but the pressure amplitude increases by an average of about 2.5 times, confirming that phase matching by geometry enables uniform propagation after penetrating an inhomogeneous barrier.

[0278] Meanwhile, the meta-structure described in the above embodiment is applied to an ultrasonic probe, and an ultrasonic probe including the meta-structure will be described below.

[0279] First, FIG. 18 is a block diagram showing an ultrasonic probe according to the prior art.

[0280] As shown in FIG. 18, the conventional ultrasonic probe 100 basically includes an ultrasonic transducer 103 (piezoelectric element) that generates ultrasonic waves, a front surface material 102 that matches the impedance difference between the ultrasonic transducer 103 and soft tissue, a lens 101 that focuses an ultrasonic beam in a direction (elevation) perpendicular to the array direction of the ultrasonic transducer 103 to obtain a two-dimensional ultrasonic cross-sectional image, and a rear surface material 104 that absorbs received ultrasonic waves or protects the ultrasonic transducer 103 from overheating.

[0281] FIG. 19a is a block diagram illustrating an ultrasound probe according to yet another embodiment of the present invention.

[0282] 19a, in the case of the ultrasonic probe 300 according to this embodiment, the meta-structure 301 according to the above-described embodiment is fabricated in a module separate from the conventional ultrasonic probe 100, and has a shape located in front (upper side in the drawing) of the conventional ultrasonic probe 100. This makes it possible to provide a multi-layer barrier and further impedance matching.

[0283] FIG. 19b is a block diagram illustrating an ultrasound probe according to yet another embodiment of the present invention.

[0284] 19b, in the case of the ultrasonic probe 410 according to this embodiment, the meta-structure 412 according to the embodiment is included in the ultrasonic probe 410 and serves as a component located between the outermost (front) lens 411 and the front material 413. Here, the front material 413 has physical properties different from those of the front material of conventional ultrasonic probes, since it must implement impedance matching between the meta-structure 412 and the piezoelectric element 414, which has a large acoustic impedance. The front material of the ultrasonic probe according to the conventional technology is mainly made by mixing metal or ceramic powder with resin, and changing the composition ratio makes it possible to match the difference in acoustic impedance between the ultrasonic transducer (piezoelectric element) and the meta-structure.

[0285] FIG. 19c is a block diagram illustrating an ultrasound probe according to yet another embodiment of the present invention.

[0286] Also, as shown in Figure 19c, in the case of the ultrasonic probe 420 according to this embodiment, the meta-structure 422 according to the embodiment replaces the front material layer in the ultrasonic probe 420 and performs impedance matching between the ultrasonic transducer 423 (piezoelectric element) and the multilayer barrier.

[0287] Here, although not shown in the drawing, if the meta-structure 422 is curved in a direction perpendicular to the array direction of the ultrasonic transducer 423 or has different physical properties or shape, the meta-structure 422 can also replace the role of the lens 421 in the ultrasonic probe 420.

[0288] FIG. 20 is a block diagram for explaining control of a meta structure in an ultrasonic probe according to still another embodiment of the present invention.

[0289] As shown in Figure 20, as described above, in order for the meta-structure 501 according to this embodiment to efficiently perform impedance matching with any multilayer barrier, the insertion position of the meta-structure 501 (or the relative distance from the multilayer barrier or probe) and the thickness or physical properties of the meta-structure 501 can be changed by the position / thickness / detachment control unit 503 included in the ultrasonic probe 500.

[0290] That is, the position / thickness / detachment control unit 503 can generate external force mechanically, thermally, or electromagnetically to change the thickness or physical properties of the meta-structure 501. The position / thickness / detachment control unit 503 can also include a motor mechanism or a joint mechanism to make the meta-structure 501 detachable so that it can be replaced with another meta-structure.

[0291] The position / thickness / detachment control unit 503 can also adjust the insertion position and distance of the meta-structure 501. The position / thickness / detachment control unit 503 can also receive a command from an external meta-structure control unit 350 via a probe cable or the like to actually control the meta-structure 501. Details regarding the control of the meta-structure will be further described in the description of the ultrasound imaging diagnostic apparatus below.

[0292] Meanwhile, the meta structure described in the above embodiment can also be applied to an ultrasound imaging diagnostic apparatus, and the ultrasound imaging diagnostic apparatus including the meta structure will be described below.

[0293] First, FIG. 21 is a block diagram showing a conventional ultrasonic imaging diagnostic apparatus.

[0294] As shown in FIG. 21, the conventional ultrasound imaging diagnostic device includes an ultrasound probe 100, an ultrasound transceiver 110 for transmitting an ultrasonic analog signal converted into electricity or amplifying a received signal, a transmit pulse generator 120, an analog-to-digital converter 130 for converting the received analog signal, a transmit / receive convergence unit 140 for adjusting a time delay for each channel to form a wavefront of a signal to be transmitted to a digital converter array or to identify the received signal for each channel according to an image position, an intermediate signal processor 150 for converting a real-valued received signal into a complex-valued signal by reducing a sampling rate to facilitate image processing, and an image processor 160 for converting a channel signal into a B-mode image 161 or extracting a blood flow signal and converting it into sound or an image 162.

[0295] FIG. 22 is a block diagram showing an ultrasound imaging apparatus according to still another embodiment of the present invention.

[0296] As shown in FIG. 22, the ultrasound imaging diagnostic apparatus according to the present embodiment includes a meta-ultrasonic probe 300 including the meta-structure and a meta-structure control unit 350, unlike the ultrasound imaging diagnostic apparatus according to the prior art.

[0297] The meta-structure control unit 350 can determine the degree of impedance matching depending on the ultrasonic reflectivity of the current multi-layer barrier and meta-structure system based on the ultrasonic reception signal. Also, the meta-structure control unit 350 can calculate the influence of the meta-structure on the image (whether image brightness is improved, whether signal-to-noise ratio is improved, whether axial resolution is reduced due to multiple internal reflections within the meta-structure and multi-layer barrier, whether signal coherency is reduced due to ultrasonic refraction by the meta-structure, etc.) based on the received ultrasonic channel signal and the current image result synthesized using a known delay-and-sum (DAS) method.

[0298] FIG. 23 is a block diagram illustrating an operation method of the ultrasound imaging diagnostic apparatus of FIG.

[0299] As shown in FIG. 23, the operation of the conventional ultrasound imaging diagnostic device is the same as the configuration procedure of the conventional ultrasound imaging diagnostic device shown in FIG. 21, with ultrasound transmission / reception and image synthesis processes, and the operation flowchart of FIG. 23 forms a closed loop to repeatedly synthesize a new image frame.

[0300] FIG. 24 is a flowchart illustrating an operation method of the ultrasound imaging diagnostic apparatus of FIG. 22, that is, an ultrasound imaging diagnostic method.

[0301] In contrast to this, referring to FIG. 24, unlike the operation of the ultrasound imaging diagnostic device according to the prior art described in FIG. 23, the operation of the ultrasound imaging diagnostic device according to this embodiment reduces the ultrasound reflectivity of the multilayer barrier, evaluates the influence of the meta-structure on the image as described above, and can repeatedly control the position of the meta-structure, etc., and also has an operating method that changes the ultrasound transmission waveform to find an ultrasound transmission waveform suitable for the current meta-structure-barrier multilayer system.

[0302] 25a and 25b are graphs showing the change in the insertion position and reflectivity due to the repeated control of the meta-structure in the operating method of the ultrasound imaging diagnostic apparatus of FIG.

[0303] 25a and 25b are graphs showing the change in the insertion position and reflectivity due to the repetitive control of the meta-structure in the operating method of the ultrasound imaging diagnostic apparatus according to the present embodiment.

[0304] When controlling the meta-structure, ultrasound probe, and ultrasound imaging diagnostic device, important variables include the thickness of the meta-structure, the physical properties of the meta-structure, the insertion position of the meta-structure (matching distance), the number of cycles of the transmitted ultrasound pulse, and the time delay and amplitude weighting values ​​that differ for each channel of the transmitted and received ultrasound during beamforming (to compensate for the non-uniform ultrasound transmittance at each position in the meta-structure-multilayer barrier system in Figure 9b).As a result, Figures 25a and 25b show the control of the insertion position of the meta-structure (matching distance) and the change in reflectivity, which clearly shows the impedance matching effect of the meta-structure of the present invention, among various important variables.

[0305] Specifically, Figure 25a shows that the insertion position of the meta-structure changes for each iteration, and as shown in Figure 25b, the reflectivity of the multi-layer system gradually decreases, and when it falls below a certain value, the movement of the meta-structure stops. Also, as shown in Figure 25b, the reflectivity can be calculated by extracting the intensity of the signal reflected by the meta-structure and the multi-layer barrier from the received ultrasonic signal.

[0306] According to the embodiments of the present invention described above, substantially 100% transmission of ultrasound through the multi-layer barrier is possible.

[0307] Furthermore, by adjusting the matching distance of the meta-structure or adjusting the physical properties such as the elastic modulus and pattern portion of the meta-structure, the environmental conditions of the multi-layer barrier can be actively addressed to efficiently transmit ultrasound.

[0308] Furthermore, ultrasonic waves can be transmitted efficiently despite not only differences in the physical properties of the skull from person to person but also differences in the physical properties depending on the location.

[0309] In addition, the meta-structure can be widely used in medical ultrasound imaging diagnosis and treatment, where ultrasound is used to penetrate into multi-layered tissues containing materials with different impedances, such as bone tissue, soft tissue, and gas, as well as in various non-destructive testing industries, where ultrasound is used to penetrate multi-layered physical barriers containing solids (metals, ceramics, plastics) or fluids (composite materials, insulation materials, rust and sludge in pipes, etc.).

[0310] As described above, the preferred embodiments of the present invention have been described with reference to the drawings. However, a person skilled in the art can make various modifications or changes to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. a matching distance from a surface of the multilayer barrier to the ultrasonic transducer, the matching distance being located within a medium provided between the ultrasonic transducer and the multilayer barrier; An impedance matching meta-structure, characterized in that the meta-structure is provided to minimize a difference between a surface impedance at the matching distance and a characteristic impedance of the medium.

2. 2. The impedance matching metastructure according to claim 1, wherein the metastructure is provided so as to have a semi-resonant mode in which the magnitude of the positive direction vibration mode and the magnitude of the negative direction vibration are substantially the same in the natural vibration mode.

3. a first layer of material having a first modulus of elasticity and a first density; a second layer of material having a second modulus of elasticity and a second density; the first material layer and the second material layer are stacked in an ultrasonic transmission direction; 2. The impedance matching metastructure according to claim 1, wherein the first elastic modulus and the second elastic modulus are different from each other, or the first density and the second density are different from each other.

4. 4. The impedance matching metastructure of claim 3, wherein the second material layer is disposed on both the front and rear surfaces of the first material layer in the ultrasonic transmission direction.

5. 5. The impedance matching metastructure of claim 4, wherein the second material layer includes a pattern portion having a first region that exposes the first material layer to the outside and a second region that covers the first material layer without exposing it.

6. 2. The impedance matching metastructure according to claim 1, wherein a plurality of said metastructures are arranged in a tiled arrangement in a direction intersecting the ultrasonic transmission direction.

7. a first metastructure positioned a first matching distance from a surface of the multilayer barrier; 2. The impedance matching metastructure according to claim 1, further comprising: a second metastructure disposed at a second matching distance from the surface of the multilayer barrier, the second matching distance being different from the first matching distance.

8. a matching distance from a surface of the multilayer barrier to the ultrasonic transducer, the matching distance being located within a medium provided between the ultrasonic transducer and the multilayer barrier; The metastructure for impedance matching is characterized in that it is arranged so as to minimize the reflection coefficient of a system transfer matrix formed by the product of transfer matrices representing the characteristic impedance and phase change of each of the metastructure, the intermediary material, and the multilayer barrier arranged at the matching distance.

9. 9. The impedance matching meta-structure of claim 8, wherein the reflection coefficient of the system transfer matrix is ​​minimized by the matching distance or the thickness of the meta-structure.

10. The impedance matching metastructure of claim 8, characterized in that it has an impedance at least twice the impedance of the medium material or substantially the same as the characteristic impedance of the multilayer barrier, so as to deepen multiple internal reflections of ultrasound propagating between the multilayer barrier and the medium material, thereby widening the range of change of the system transfer matrix.

11. disposed within a medium disposed between the ultrasonic transducer and the barrier; a first meta-structure disposed at a first matching distance from the first surface region of the barrier toward the ultrasonic transducer, the first meta-structure being configured to minimize a difference between a first surface impedance and a characteristic impedance of the medium at the first matching distance; and a second metastructure disposed at a second matching distance on the ultrasonic transducer side from a second surface region of the barrier adjacent to the first surface region, and configured so as to minimize a difference between a second surface impedance at the second matching distance and a characteristic impedance of the medium.

12. the first metastructure has a first effective radiation area corresponding to the first surface area; the second metastructure has a second effective radiation area corresponding to the second surface area; 12. The impedance-matching metastructure of claim 11, wherein the first effective radiating area and the second effective radiating area each have a width less than one-half wavelength (λ).

13. disposed within a medium disposed between the ultrasonic transducer and the barrier; a first metastructure disposed at a first matching distance from the first surface region of the barrier toward the ultrasonic transducer, the first metastructure disposed at the first matching distance, the first metastructure disposed at the first matching distance, the intermediate material, and the barrier, the first metastructure being configured to minimize a reflection coefficient of a first system transfer matrix formed by a product of a characteristic impedance and a first transfer matrix representing a phase change; An impedance matching metastructure comprising: a second metastructure disposed at a second matching distance on the ultrasonic transducer side from a second surface region of the barrier adjacent to the first surface region, the second metastructure disposed at the second matching distance, the intermediate material, and the second metastructure configured so as to minimize a reflection coefficient of a second system transfer matrix formed by the product of a second transfer matrix represented by a phase change and the characteristic impedance of each of the barrier.

14. The first metastructure comprises: a first meta-structure disposed a first matching distance from the first surface region; 14. The impedance matching metastructure of claim 13, further comprising: a first-second metastructure disposed at a first-second matching distance different from the first surface region.

15. The impedance matching metastructure of claim 13, wherein the first metastructure has an impedance at least twice as high as the impedance of the medium material or substantially the same as the characteristic impedance of the barrier, so as to deepen multiple internal reflections of ultrasound propagating between the barrier and the first system transfer matrix and thereby widen the range of variation of the first system transfer matrix.

16. The metastructure of claim 1 or 8; and an ultrasonic transducer that provides ultrasonic waves to the meta-structure.

17. 17. The ultrasonic probe of claim 16, wherein the meta-structure moves in an ultrasonic transmission direction relative to the multilayer barrier.

18. The metastructure of claim 11 or 13; and an ultrasonic transducer that provides ultrasonic waves to the meta-structure.

19. 20. The ultrasonic probe of claim 18, wherein the first meta-structure or the second meta-structure is moved in an ultrasonic transmission direction relative to the ultrasonic transducer.

20. A metastructure according to any one of claims 1, 8, 11 and 13; an ultrasonic transducer for providing ultrasonic waves to the metastructure; a signal processing unit that processes the signal received from the ultrasonic transducer to generate an ultrasonic image; and a meta-structure control unit that controls at least one of the physical property, thickness, and matching distance of the meta-structure based on the ultrasound image generated by the signal processing unit.

Images