Method for designing meta-structure for non-uniform barrier, meta-structure for non-uniform barrier manufactured thereby, ultrasonic probe for non-uniform barrier, and ultrasonic imaging device for non-uniform barrier

Abstract

The present invention relates to a method for designing a meta-structure for a non-uniform barrier, the method comprising: an ultrasonic transmission and reception step; a non-uniform barrier thickness and physical property extraction step; a time difference extraction step; and a thickness determination step. In the ultrasonic transmission and reception step, an ultrasonic transmission signal is transmitted toward a non-uniform barrier, and a first ultrasonic reception signal reflected and incident from the non-uniform barrier and a second ultrasonic reception signal incident after passing through the non-uniform barrier are received. In the non-uniform barrier thickness and physical property extraction step, the thickness and physical properties of the non-uniform barrier are extracted on the basis of the first ultrasonic reception signal. In the time difference extraction step, an arrival time difference in each transducer element is extracted on the basis of the second ultrasonic reception signal. In the thickness determination step, the thickness of a unit cell of the meta-structure to be disposed in correspondence to each transducer element is determined by using the physical properties of a medium through which the ultrasonic transmission signal and the second ultrasonic reception signal are propagated, the physical properties of a material of the meta-structure to be designed, and the arrival time difference.

Description

Design method of a metastructure for a non-uniform barrier, a metastructure for a non-uniform barrier manufactured thereby, an ultrasonic probe for a non-uniform barrier, and an ultrasonic imaging diagnostic device for a non-uniform barrier

[0001] The present invention relates to a method for designing a meta-structure for a non-uniform barrier, and more particularly, to a method for designing a meta-structure for a non-uniform barrier that is mounted on an ultrasonic transducer and improves focusing penetration performance for a non-uniform barrier such as a skull.

[0002] The skull, the bony tissue that protects the brain, is a multilayered structure composed of calcium-hardened connective tissue, with cortical bone layered on the inner and outer surfaces and trabecular bone in between. Cortical bone is a relatively dense, hard tissue, while cancellous bone is a relatively loose, porous, soft tissue. Cortical and cancellous bone possess different physical properties, as well as thickness, making the skull a multilayered barrier to ultrasound penetration.

[0003] The skull, which is composed of multilayered barrier structures such as cortical bone-spongy bone-cortical bone, has a high reflectivity and low transmittance due to the impedance difference at the boundary of each barrier structure when performing medical ultrasound imaging using ultrasound or treatment using focused ultrasound.

[0004] The skull is a heterogeneous medium, with varying thicknesses and porosities within each layer depending on location. This causes waves (ultrasound, electromagnetic waves, etc.) to refract haphazardly, distorting images transmitted through the skull. Furthermore, the thickness and properties of each layer of cancellous and cortical bone vary from person to person, making it even more difficult to achieve individualized ultrasound focus.

[0005] Meanwhile, the ultrasound probe used in conventional ultrasound imaging diagnostic devices is basically composed of a lens, a front material, an ultrasound transducer (piezoelectric element), and a back material. At this time, the lens collects ultrasound perpendicular to the direction of the ultrasound transducer array, and plays a role in focusing the signal for reconstructing a two-dimensional cross-sectional image.

[0006] However, existing ultrasound lenses are designed to transmit and receive signals by focusing them around a specific focal distance for soft tissues of the human body with a uniform sound speed, making it difficult to transmit and receive ultrasound signals through barriers of the human body such as bones or gas (air layers inside the digestive organs) where the sound speed difference is large or uneven.

[0007] Although it is possible to correct for non-uniform sound velocity distribution or ultrasonic aberration using an ultrasonic transducer with a two-dimensional array without a lens, this method is not widely used due to practical problems such as low sensitivity of a single transducer element, high manufacturing cost, and the limited number of channels of existing imaging devices (about 256).

[0008] Accordingly, the problem to be solved by the present invention is to solve such a conventional problem, and to provide a method for designing a metastructure for a non-uniform barrier that forms an ultrasound transmission focus or improves the focusing transmittance by penetrating a non-uniform barrier such as a skull by determining the thickness of a unit cell of the metastructure corresponding to the transducer element using a different arrival time difference or a different arrival phase value for each ultrasonic transducer element and designing the metastructure.

[0009] In order to achieve the above object, the design method of the meta-structure for a non-uniform barrier of the present invention is characterized by including an ultrasonic transmission / reception step of transmitting an ultrasonic transmission signal toward the non-uniform barrier and receiving a first ultrasonic reception signal reflected from the non-uniform barrier and incident thereon and a second ultrasonic reception signal transmitted through the non-uniform barrier and then incident thereon; a non-uniform barrier thickness and property extraction step of extracting a thickness and a property of the non-uniform barrier based on the first ultrasonic reception signal; a time difference extraction step of extracting an arrival time difference for each transducer element based on the second ultrasonic reception signal; and a thickness determination step of determining a thickness of a unit cell of the meta-structure to be arranged correspondingly for each transducer element using the properties of a medium through which the ultrasonic transmission signal and the second ultrasonic reception signal propagate, the properties of a material of the meta-structure to be designed, and the arrival time difference.

[0010] In the design method of a meta-structure for a non-uniform barrier according to the present invention, an aberration correction step, which is performed after the thickness determination step and corrects the aberration of the non-uniform barrier based on a Chebyshev polynomial or a Zernike polynomial, may be further included.

[0011] In the design method of a meta-structure for a non-uniform barrier according to the present invention, in the time difference extraction step, the arrival time difference is extracted by using the difference between the arrival time at which the second ultrasonic reception signal reaches each element of the converter and the arrival time at which the second ultrasonic reception signal reaches a reference element among the converter elements, and in the thickness determination step, when the sound speed in the meta-structure is greater than the sound speed in the medium, the thickness of the unit cell of the meta-structure to be arranged to correspond to the converter element having a relatively large arrival time difference may be determined to be thicker than the thickness of the unit cell of the meta-structure to be arranged to correspond to the converter element having a relatively small arrival time difference, and when the sound speed in the meta-structure is less than the sound speed in the medium, the thickness of the unit cell of the meta-structure to be arranged to correspond to the converter element having a relatively large arrival time difference may be determined to be thinner than the thickness of the unit cell of the meta-structure to be arranged to correspond to the converter element having a relatively small arrival time difference.

[0012] In the design method of a meta-structure for a non-uniform barrier according to the present invention, in the time difference extraction step, the arrival time at which the second ultrasonic reception signal reaches each element of the converter can be selected as the time at which the second ultrasonic reception signal having an amplitude greater than a preset threshold value first arrives.

[0013] In the design method of a meta-structure for a non-uniform barrier according to the present invention, in the time difference extraction step, the arrival time at which the second ultrasonic reception signal reaches each element of the converter can be selected as the time at which the second ultrasonic reception signal having the maximum amplitude arrives.

[0014] In the design method of a meta-structure for a non-uniform barrier according to the present invention, in the time difference extraction step, the arrival time at which the second ultrasonic reception signal reaches each element of the converter can be selected as the arrival time at which the second ultrasonic reception signal having an amplitude of a preset reference value arrives.

[0015] In addition, in order to achieve the above object, the design method of the meta-structure for a non-uniform barrier of the present invention is characterized by including an ultrasonic transmission / reception step of transmitting an ultrasonic transmission signal toward the non-uniform barrier and receiving a first ultrasonic reception signal reflected from the non-uniform barrier and incident thereon and a second ultrasonic reception signal transmitted through the non-uniform barrier and then incident thereon; a non-uniform barrier thickness and property extraction step of extracting a thickness and a property of the non-uniform barrier based on the first ultrasonic reception signal; a signal conversion step of converting the second ultrasonic reception signal into a complex signal for each converter element; a phase value extraction step of extracting an arrival phase value reached for each converter element based on the complex signal; and a thickness determination step of determining a thickness of a unit cell of the meta-structure to be arranged correspondingly for each converter element using the properties of a medium through which the ultrasonic transmission signal and the second ultrasonic reception signal propagate, the properties of a material of the meta-structure to be designed, and the arrival phase value.

[0016] In the design method of a meta-structure for a non-uniform barrier according to the present invention, an aberration correction step, which is performed after the thickness determination step and corrects the aberration of the non-uniform barrier based on a Chebyshev polynomial or a Zernike polynomial, may be further included.

[0017] In the design method of a metastructure for a non-uniform barrier according to the present invention, in the thickness determination step, when the sound speed in the metastructure is greater than the sound speed in the medium, the thickness of a unit cell of the metastructure to be arranged to correspond to a converter element having a relatively large arrival phase value may be determined to be thicker than the thickness of a unit cell of the metastructure to be arranged to correspond to a converter element having a relatively small arrival phase value, and when the sound speed in the metastructure is less than the sound speed in the medium, the thickness of a unit cell of the metastructure to be arranged to correspond to a converter element having a relatively large arrival phase value may be determined to be thinner than the thickness of a unit cell of the metastructure to be arranged to correspond to a converter element having a relatively small arrival phase value.

[0018] In the design method of a meta-structure for a non-uniform barrier according to the present invention, in the phase value extraction step, the arrival phase value of the complex signal reaching each element of the converter can be selected as the phase value of the complex signal having the maximum amplitude among the complex signals.

[0019] In the design method of a meta-structure for a non-uniform barrier according to the present invention, in the phase value extraction step, the arrival phase value of the complex signal reaching each element of the converter can be selected as the phase value of the complex signal corresponding to the center frequency of the ultrasonic transmission signal of the converter element.

[0020] In the design method of a meta-structure for a non-uniform barrier according to the present invention, in the phase value extraction step, the average amplitude of the complex signal is calculated within a certain frequency range, and the arrival phase value of the complex signal reaching each element of the converter can be selected as the phase value of the complex signal corresponding to the average amplitude among the complex signals.

[0021] In addition, in order to achieve the above purpose, the meta-structure for a non-uniform barrier of the present invention is characterized in that it is manufactured by the design method of the meta-structure for a non-uniform barrier.

[0022] In addition, in order to achieve the above purpose, the ultrasonic probe for a non-uniform barrier of the present invention is characterized by including: a meta-structure for a non-uniform barrier manufactured by the design method of the meta-structure for a non-uniform barrier; and a converter for converting an electric signal into an ultrasonic signal and transmitting it or converting a received ultrasonic signal into an electric signal.

[0023] In the ultrasonic probe for a non-uniform barrier according to the present invention, a meta-structure position adjustment unit for adjusting the relative distance between the meta-structure for the non-uniform barrier and the non-uniform barrier may be further included.

[0024] In addition, in order to achieve the above purpose, the ultrasonic imaging diagnostic device for a non-uniform barrier of the present invention is characterized by including: a meta-structure for a non-uniform barrier manufactured by the design method of the meta-structure for a non-uniform barrier; an ultrasonic probe for a non-uniform barrier having a converter; and an image conversion unit for converting a signal received through the ultrasonic probe for a non-uniform barrier into an image.

[0025] In the ultrasound imaging device for a non-uniform barrier according to the present invention, a meta-structure position adjustment unit for adjusting the relative distance between the non-uniform barrier meta-structure and the non-uniform barrier may be further included.

[0026] In the ultrasonic imaging diagnostic device for a non-uniform barrier according to the present invention, a meta-structure control unit may be further included that calculates the focusing speed of the barrier-penetrating ultrasound of the meta-structure for the non-uniform barrier through the second ultrasonic reception signal and determines the focusing penetration performance.

[0027] In the ultrasonic imaging diagnostic device for a non-uniform barrier according to the present invention, the device may further include a non-uniform barrier thickness and property extraction unit that extracts the thickness and property of the non-uniform barrier through the first ultrasonic reception signal.

[0028] According to the design method of the meta-structure for a non-uniform barrier of the present invention, it is possible to form an ultrasound transmission focus or improve the focused transmittance by penetrating a non-uniform barrier such as a skull.

[0029] According to the ultrasound imaging device for a non-uniform barrier of the present invention, the quality of the output image can be improved by evaluating the influence of the metastructure for the non-uniform barrier on the image and adjusting the relative distance between the metastructure and the non-uniform barrier.

[0030] Figure 1 is a schematic diagram of a converter that transmits and receives ultrasonic signals for an uneven barrier.

[0031] FIG. 2 is a drawing sequentially showing a design method of a meta-structure for a non-uniform barrier according to one embodiment of the present invention.

[0032] Figure 3 is a drawing for explaining the time difference extraction step of the design method of the meta-structure for the non-uniform barrier of Figure 2.

[0033] Figures 4 and 5 are drawings for explaining the thickness determination step of the design method of the meta-structure for the non-uniform barrier of Figure 2.

[0034] FIG. 6 is a drawing sequentially showing a design method of a meta-structure for a non-uniform barrier according to another embodiment of the present invention.

[0035] Fig. 7 is a drawing for explaining the phase value extraction step of the design method of the metastructure for the non-uniform barrier of Fig. 6.

[0036] Figures 8 and 9 are drawings for explaining the thickness determination step of the design method of the meta-structure for the non-uniform barrier of Figure 6.

[0037] FIG. 10 is a drawing showing an example of a meta-structure for a non-uniform barrier manufactured by the design method of a meta-structure for a non-uniform barrier of the present invention.

[0038] FIG. 11 is a drawing schematically illustrating the configuration of an ultrasonic probe for a non-uniform barrier according to one embodiment of the present invention.

[0039] FIG. 12 is a drawing schematically illustrating the configuration of an ultrasonic imaging diagnostic device for a non-uniform barrier according to one embodiment of the present invention.

[0040] Hereinafter, embodiments of a design method for a meta-structure for a non-uniform barrier according to the present invention will be described in detail with reference to the attached drawings.

[0041] FIG. 1 is a schematic diagram illustrating a transducer for transmitting and receiving ultrasonic signals for a non-uniform barrier, FIG. 2 is a diagram sequentially illustrating a design method of a meta-structure for a non-uniform barrier according to an embodiment of the present invention, FIG. 3 is a diagram for explaining a time difference extraction step of the design method of the meta-structure for a non-uniform barrier of FIG. 2, and FIGS. 4 and 5 are diagrams for explaining a thickness determination step of the design method of the meta-structure for a non-uniform barrier of FIG. 2.

[0042] Referring to FIGS. 1 to 5, a design method (M1) of a meta-structure for a non-uniform barrier according to the present embodiment is to be mounted on an ultrasonic transducer to improve focused penetration performance for a non-uniform barrier such as a skull, and includes an ultrasonic transmission / reception step (S110), a non-uniform barrier thickness and property extraction step (S120), a time difference extraction step (S130), a thickness determination step (S140), and an aberration correction step (S150).

[0043] First, in the present invention, the heterogeneous barrier (10) is explained as an example of a skull composed of a multi-layered structure in which trabecular bone is laminated on the inside and outside with cortical bone in between.

[0044] The above ultrasonic transmission / reception step (S110) transmits an ultrasonic transmission signal (TS) toward the non-uniform barrier (10), and receives a first ultrasonic reception signal (RS1) that is reflected from the non-uniform barrier (10) and is incident, and a second ultrasonic reception signal (RS2) that is incident after passing through the non-uniform barrier (10).

[0045] Referring to FIG. 1, the elements (111a, 111b, 111c) of the converter (110) are arranged in an array form, and each element (111a, 111b, 111c) of the converter (110) transmits an ultrasonic transmission signal (TS) toward a target point (TP) inside an uneven barrier (10).

[0046] The ultrasonic transmission signal (TS) transmitted from the transducer (110) elements (111a, 111b, 111c) can be reflected from the surface of the non-uniform barrier (10) by propagating through the medium (i) between the transducer (110) and the non-uniform barrier (10), and a part of the ultrasonic transmission signal (TS) is incident on the inside of the non-uniform barrier (10) and propagated inside the non-uniform barrier (10).

[0047] The ultrasonic reception signal reflected from the non-uniform barrier (10) and incident on each element (111a, 111b, 111c) of the converter (110) is defined as the first ultrasonic reception signal (RS1), and the ultrasonic reception signal reflected from the target point (TP) and incident after passing through the non-uniform barrier (10) is defined as the second ultrasonic reception signal (RS2).

[0048] The above non-uniform barrier thickness and property extraction step (S120) extracts the thickness and property of the non-uniform barrier (10) based on the first ultrasonic reception signal (RS1).

[0049] The first ultrasonic reception signal (RS1) reflected from the non-uniform barrier (10) is received by each element (111a, 111b, 111c) of the array-type converter (110), and the thickness distribution and physical properties (density, sound speed) of the non-uniform barrier (10) can be extracted.

[0050] The above time difference extraction step (S120) extracts the arrival time difference reached by each converter element (111a, 111b, 111c) based on the second ultrasonic reception signal (RS2).

[0051] Here, the arrival time difference can be extracted by using the difference between the arrival times (RTa, RTb, RTc) at which the second ultrasonic reception signal (RS2) reaches each element (111a, 111b, 111c) of the converter and the arrival time (RTb) at which the second ultrasonic reception signal (RS2) reaches the reference element (111b) among the converter elements.

[0052] For example, if the reference element among the converter elements is selected as the second converter element (111b) arranged in the center of the array arrangement, the arrival time difference reaching the first converter element (111a) may be RTa-RTb, and the arrival time difference reaching the third converter element (111c) may be RTc-RTb.

[0053] At this time, the arrival time (RTa, RTb, RTc) at which the second ultrasonic reception signal (RS2) reaches each element (111a, 111b, 111c) of the converter can be selected by one of the following three methods.

[0054] First, referring to (a) of FIG. 3, the arrival time (RTa, RTb, RTc) at which the second ultrasonic reception signal (RS2) reaches each element (111a, 111b, 111c) of the converter can be selected as the time (T1) at which the ultrasonic reception signal (RS) having an amplitude (A11) greater than a preset threshold value first arrives.

[0055] A second ultrasonic reception signal (RS2) having an amplitude less than a threshold value can be determined as noise reflected from an arbitrary point inside the non-uniform barrier (10), and a threshold value can be set at which it can be determined as a second ultrasonic reception signal (RS2) received by passing through the non-uniform barrier (10).

[0056] Secondly, referring to (b) of FIG. 3, the arrival times (RTa, RTb, RTc) at which the second ultrasonic reception signal (RS2) reaches each element (111a, 111b, 111c) of the converter can be selected as the time (T2) at which the second ultrasonic reception signal (RS2) having the maximum amplitude (A12) reaches.

[0057] The time at which the signal having the strongest value among the second ultrasonic reception signals (RS2) received by penetrating the non-uniform barrier (10) arrives is selected as the arrival time (RTa, RTb, RTc) at each element (111a, 111b, 111c).

[0058] Thirdly, referring to (c) of FIG. 3, the arrival time (RTa, RTb, RTc) at which the second ultrasonic reception signal (RS2) reaches each element (111a, 111b, 111c) of the converter can be selected as the time (T3) at which the second ultrasonic reception signal (RS2) having an amplitude (A13) of a preset reference value arrives.

[0059] The time at which a signal having a certain reference value between the threshold value of Fig. 3 (a) and the maximum value of Fig. 3 (b) among the second ultrasonic reception signals (RS2) received by penetrating the non-uniform barrier (10) arrives is selected as the arrival time (RTa, RTb, RTc) at each element (111a, 111b, 111c).

[0060] The above thickness determination step (S130) determines the thickness of the unit cells (121a, 121b, 121c) of the meta-structure (120) to be arranged correspondingly to each converter element (111a, 111b, 111c) by using the properties of the medium (i) through which the ultrasonic transmission signal (TS) and the second ultrasonic reception signal (RS2) are transmitted, the properties of the material of the meta-structure (120) to be designed, and the arrival time difference (RTa-RTb, RTc-RTb).

[0061] Here, the unit cells (121a, 121b, 121c) of the meta structure (120) are arranged in a one-to-one correspondence with the converter elements (111a, 111b, 111c), and can be formed in the same quantity as the number of converter elements (111a, 111b, 111c) arranged in an array form.

[0062] Referring to FIG. 4, when the sound speed (Cm) in the metastructure (120) is greater than the sound speed (Ci) in the medium (i), the principle of determining the thickness of the unit cells (121a, 121b, 121c) of the metastructure (120) is explained.

[0063] When the speed of sound (Cm) in the metastructure (120) is greater than the speed of sound (Ci) in the medium (i), it may mean that the density of the material of the metastructure (120) is less than the density of the medium (i) through which the ultrasonic transmission signal (TS) and the second ultrasonic reception signal (RS2) are propagated. In addition, when the speed of sound (Cm) in the metastructure (120) is greater than the speed of sound (Ci) in the medium (i), it may also mean that the stiffness of the material of the metastructure (120) is greater than the stiffness of the medium (i) through which the ultrasonic transmission signal (TS) and the second ultrasonic reception signal (RS2) are propagated.

[0064] Under these conditions, if the arrival time difference (RTa-RTb) of the first converter element (111a) is greater than the arrival time difference (RTc-RTb) of the third converter element (111c), it is preferable to determine the thickness (w1) of the first unit cell (121a) of the meta-structure to be arranged corresponding to the first converter element (111a) to be thicker than the thickness (w3) of the third unit cell (121c) of the meta-structure to be arranged corresponding to the third converter element (111c).

[0065] By forming the unit cell of the meta-structure having a relatively fast sound speed thicker, when the meta-structure (120) designed in front of the converter (110) is installed, the deviation in the arrival time difference between the converter elements (111a, 111b, 111c) can be reduced, thereby improving the transmission focus of the ultrasonic image.

[0066] In contrast, referring to FIG. 5, when the sound speed (Cm) in the metastructure (120) is smaller than the sound speed (Ci) in the medium (i), the principle of determining the thickness of the unit cells (121a, 121b, 121c) of the metastructure (120) is explained.

[0067] When the speed of sound (Cm) in the metastructure (120) is smaller than the speed of sound (Ci) in the medium (i), it may mean that the density of the material of the metastructure (120) is larger than the density of the medium (i) through which the ultrasonic transmission signal (TS) and the second ultrasonic reception signal (RS2) are propagated. In addition, when the speed of sound (Cm) in the metastructure (120) is smaller than the speed of sound (Ci) in the medium (i), it may also mean that the stiffness of the material of the metastructure (120) is smaller than the stiffness of the medium (i) through which the ultrasonic transmission signal (TS) and the second ultrasonic reception signal (RS2) are propagated.

[0068] Under these conditions, if the arrival time difference (RTa-RTb) of the first converter element (111a) is greater than the arrival time difference (RTc-RTb) of the third converter element (111c), it is preferable to determine the thickness (w1) of the first unit cell (121a) of the meta-structure to be arranged corresponding to the first converter element (111a) to be thinner than the thickness (w3) of the third unit cell (121c) of the meta-structure to be arranged corresponding to the third converter element (111c).

[0069] By forming the thickness of the unit cell of the meta-structure having a relatively slow sound speed thinner, when the designed meta-structure (120) is installed in front of the converter (110), the deviation in the arrival time difference between the converter elements (111a, 111b, 111c) can be reduced, thereby improving the transmission focus of the ultrasonic image.

[0070] The above aberration correction step (S150) is performed after the thickness determination step (S140) and corrects the aberration of the non-uniform barrier (10) based on the Chebyshev polynomial or the Zernike polynomial.

[0071] The design process of the non-uniform barrier customized meta-structure (120) is performed through mode decomposition based on Chebyshev polynomials or Zernike polynomials, and through mode decomposition, the aberrations occurring in the non-uniform barrier (10) are quantitatively analyzed by dividing them into low-order terms and high-order terms, and the main aberrations of the non-uniform barrier are efficiently corrected through the low-order mode, and by reflecting the high-order mode, even complex micro-aberrations are precisely corrected, thereby greatly improving the ultrasonic focusing performance and transmission efficiency.

[0072] Meanwhile, FIG. 6 is a drawing sequentially showing a design method of a meta-structure for a non-uniform barrier according to another embodiment of the present invention, FIG. 7 is a drawing for explaining a phase value extraction step of the design method of the meta-structure for a non-uniform barrier of FIG. 6, and FIGS. 8 and 9 are drawings for explaining a thickness determination step of the design method of the meta-structure for a non-uniform barrier of FIG. 6.

[0073] Referring to FIGS. 6 to 9, the design method (M2) of a meta-structure for a non-uniform barrier according to the present embodiment includes an ultrasonic transmission / reception step (S210), a non-uniform barrier thickness and material property extraction step (S220), a signal conversion step (S230), a phase value extraction step (S240), a thickness determination step (S250), and an aberration correction step (S260).

[0074] The above ultrasonic transmission / reception step (S210) transmits an ultrasonic transmission signal (TS) toward the non-uniform barrier (10), and receives a first ultrasonic reception signal (RS1) that is reflected from the non-uniform barrier (10) and is incident, and a second ultrasonic reception signal (RS2) that is incident after passing through the non-uniform barrier (10).

[0075] The elements (111a, 111b, 111c) of the converter (110) are arranged in an array form, and each element (111a, 111b, 111c) of the converter (110) transmits an ultrasonic transmission signal (TS) toward a target point (TP) inside the non-uniform barrier (10).

[0076] The ultrasonic transmission signal (TS) transmitted from the transducer (110) elements (111a, 111b, 111c) can be reflected from the surface of the non-uniform barrier (10) by propagating through the medium (i) between the transducer (110) and the non-uniform barrier (10), and a part of the ultrasonic transmission signal (TS) is incident on the inside of the non-uniform barrier (10) and propagated inside the non-uniform barrier (10).

[0077] The ultrasonic reception signal reflected from the non-uniform barrier (10) and incident on each element (111a, 111b, 111c) of the converter (110) is defined as the first ultrasonic reception signal (RS1), and the ultrasonic reception signal reflected from the target point (TP) and incident after passing through the non-uniform barrier (10) is defined as the second ultrasonic reception signal (RS2).

[0078] The above non-uniform barrier thickness and property extraction step (S220) extracts the thickness and property of the non-uniform barrier (10) based on the first ultrasonic reception signal (RS1).

[0079] The first ultrasonic reception signal (RS1) reflected from the non-uniform barrier (10) is received by each element (111a, 111b, 111c) of the array-type converter (110), and the thickness distribution and physical properties (density, sound speed) of the non-uniform barrier (10) can be extracted.

[0080] The above signal conversion step (S230) converts the ultrasonic reception signal (RS) into a complex signal for each converter element (111a, 111b, 111c).

[0081] The process of converting the second ultrasonic reception signal (RS2), which is a real-valued signal received and converted into a digital signal in the ultrasonic transmission / reception step (S210), into a complex signal can utilize Fourier transform or an IQ demodulation technique, which is a decomposition process of in-phase and quadrature components. Since the Fourier transform or IQ demodulation technique is a technique widely known to those skilled in the art, a detailed description thereof will be omitted.

[0082] The above phase value extraction step (S240) extracts the reached phase value for each converter element (111a, 111b, 111c) based on the complex signal.

[0083] At this time, the arrival phase values ​​(RPa, RPb, RPc) at which the complex signal reaches each element (111a, 111b, 111c) of the converter can be selected by one of the three methods below.

[0084] First, referring to (a) of Fig. 7, the arrival phase values ​​(RPa, RPb, RPc) at which the complex signal reaches each element (111a, 111b, 111c) of the converter can be selected as the phase values ​​of the complex signal (f1) having the maximum amplitude (A21) among the complex signals.

[0085] The phase value at which the signal having the strongest value among the complex signals received by penetrating the non-uniform barrier (10) reaches is selected as the arrival phase value (RPa, RPb, RPc) at each element (111a, 111b, 111c).

[0086] Secondly, referring to (b) of Fig. 7, the arrival phase values ​​(RPa, RPb, RPc) at which the complex signal reaches each element (111a, 111b, 111c) of the converter can be selected as the phase values ​​of the complex signal (f2) corresponding to the center frequency of the ultrasonic transmission signal of the converter elements (111a, 111b, 111c).

[0087] Thirdly, referring to (c) of Fig. 7, the average amplitude of the complex signal (f3 to f4) within a certain frequency range is calculated, and the arrival phase values ​​(RPa, RPb, RPc) at which the ultrasonic reception signal reaches each element (111a, 111b, 111c) of the converter can be selected as the phase values ​​of the complex signal corresponding to the average amplitude among the complex signals.

[0088] The average amplitude will be determined between A23 and the maximum amplitude, and the complex signal corresponding to this average amplitude will be selected between f3 and f4.

[0089] The above thickness determination step (S250) uses the properties of the medium (i) through which the ultrasonic transmission signal (TS) and the second ultrasonic reception signal (RS2) are transmitted, the properties of the material of the meta-structure (120) to be designed, and the arrival phase values ​​(RPa, RPb, RPc) to determine the thickness of the unit cells (121a, 121b, 121c) of the meta-structure (120) to be arranged correspondingly to each converter element (111a, 111b, 111c).

[0090] Referring to FIG. 8, when the sound speed (Cm) in the metastructure (120) is greater than the sound speed (Ci) in the medium (i), the principle of determining the thickness of the unit cells (121a, 121b, 121c) of the metastructure (120) is explained.

[0091] When the speed of sound (Cm) in the metastructure (120) is greater than the speed of sound (Ci) in the medium (i), it may mean that the density of the material of the metastructure (120) is less than the density of the medium (i) through which the ultrasonic transmission signal (TS) and the second ultrasonic reception signal (RS2) are propagated. In addition, when the speed of sound (Cm) in the metastructure (120) is greater than the speed of sound (Ci) in the medium (i), it may also mean that the stiffness of the material of the metastructure (120) is less than the stiffness of the medium (i) through which the ultrasonic transmission signal (TS) and the second ultrasonic reception signal (RS2) are propagated.

[0092] Under these conditions, if the arrival phase value (RPa) of the first converter element (111a) is greater than the arrival phase difference (RPc) of the third converter element (111c), it is preferable to determine the thickness (w1) of the first unit cell (121a) of the meta-structure to be arranged corresponding to the first converter element (111a) to be thicker than the thickness (w3) of the third unit cell (121c) of the meta-structure to be arranged corresponding to the third converter element (111c).

[0093] By forming the unit cell of the meta-structure having a relatively fast sound speed thicker, when the meta-structure (120) designed in front of the converter (110) is installed, the deviation of the arrival phase value between the converter elements (111a, 111b, 111c) can be reduced, thereby improving the transmission focusing speed of the ultrasonic image.

[0094] In contrast, referring to FIG. 9, when the sound speed (Cm) in the metastructure (120) is smaller than the sound speed (Ci) in the medium (i), the principle of determining the thickness of the unit cells (121a, 121b, 121c) of the metastructure (120) is explained.

[0095] When the speed of sound (Cm) in the metastructure (120) is smaller than the speed of sound (Ci) in the medium (i), it may mean that the density of the material of the metastructure (120) is larger than the density of the medium (i) through which the ultrasonic transmission signal (TS) and the second ultrasonic reception signal (RS2) are propagated. In addition, when the speed of sound (Cm) in the metastructure (120) is smaller than the speed of sound (Ci) in the medium (i), it may also mean that the stiffness of the material of the metastructure (120) is larger than the stiffness of the medium (i) through which the ultrasonic transmission signal (TS) and the second ultrasonic reception signal (RS2) are propagated.

[0096] Under these conditions, if the arrival phase value (RPa) of the first converter element (111a) is greater than the arrival phase value (RPc) of the third converter element (111c), it is preferable to determine the thickness (w1) of the first unit cell (121a) of the meta-structure to be arranged corresponding to the first converter element (111a) to be thinner than the thickness (w3) of the third unit cell (121c) of the meta-structure to be arranged corresponding to the third converter element (111c).

[0097] By forming the thickness of the unit cell of the meta-structure having a relatively slow sound speed thinner, when the designed meta-structure (120) is installed in front of the converter (110), the deviation of the arrival phase value between the converter elements (111a, 111b, 111c) can be reduced, thereby improving the transmission focusing speed of the ultrasonic image.

[0098] The above aberration correction step (S260) is performed after the thickness determination step (S250) and corrects the aberration of the non-uniform barrier (10) based on the Chebyshev polynomial or the Zernike polynomial.

[0099] The design process of the non-uniform barrier customized meta-structure (120) is performed through mode decomposition based on Chebyshev polynomials or Zernike polynomials, and through mode decomposition, the aberrations occurring in the non-uniform barrier (10) are quantitatively analyzed by dividing them into low-order terms and high-order terms, and the main aberrations of the non-uniform barrier are efficiently corrected through the low-order mode, and by reflecting the high-order mode, even complex micro-aberrations are precisely corrected, thereby greatly improving the ultrasonic focusing performance and transmission efficiency.

[0100] Meanwhile, FIG. 10 is a drawing showing an example of a meta-structure for a non-uniform barrier manufactured by a design method of a meta-structure for a non-uniform barrier of the present invention, FIG. 11 is a drawing schematically showing the configuration of an ultrasonic probe for a non-uniform barrier according to an embodiment of the present invention, and FIG. 12 is a drawing schematically showing the configuration of an ultrasonic imaging diagnostic device for a non-uniform barrier according to an embodiment of the present invention.

[0101] Referring to FIG. 10, the meta-structure (120) for a non-uniform barrier manufactured by the design method (M1, M2) for the above non-uniform barrier can be formed in the form of an array of unit cells (121) having a thickness determined by the design method (M1, M2) above.

[0102] That is, the thickness of each unit cell (121) of the meta-structure (120) can be formed so that the deviation in the arrival time difference or arrival phase value is minimized by reflecting the thickness, degree of porosity, etc. of the non-uniform barrier (10) placed in front of each unit cell (121) of the meta-structure (120).

[0103] Referring to FIG. 11, an ultrasonic probe (100) for a non-uniform barrier is characterized by including a transducer (110), a meta-structure (120) for a non-uniform barrier, and a meta-structure position adjustment unit (130).

[0104] The above converter (110) converts an electrical signal into an ultrasonic signal and transmits it or converts a received ultrasonic signal into an electrical signal.

[0105] The above-described meta-structure (120) for a non-uniform barrier is manufactured by the design method (M1, M2) of the above-described meta-structure for a non-uniform barrier. The meta-structure (120) for a non-uniform barrier can be formed in the form of an array of unit cells (121) having a thickness determined by the above-described design method (M1, M2).

[0106] The above meta-structure position adjustment unit (130) can adjust the relative distance between the meta-structure (120) for the non-uniform barrier and the non-uniform barrier (10).

[0107] The relative distance between the meta-structure (120) for the non-uniform barrier and the non-uniform barrier (10) can be manually adjusted by a worker, or the meta-structure (120) for the non-uniform barrier can be moved by an external force using a motor, linear motion guide, etc. installed in the probe.

[0108] Meanwhile, in the ultrasonic probe (100) for a non-uniform barrier of the present embodiment, the meta-structure (120) for a non-uniform barrier can be detachably installed. Since the thickness and properties of each layer constituting the cancellous bone and cortical bone differ for each individual, a meta-structure (120) for a non-uniform barrier that is custom-designed for each individual can be replaced and used.

[0109] The ultrasonic probe (100) for a non-uniform barrier of the present embodiment may additionally be installed with a front material (101) whose impedance is matched to facilitate ultrasonic transmission, a rear material (102) responsible for ultrasonic absorption and heat absorption, etc. An ultrasonic lens (not shown) capable of focused ultrasonic transmission into general soft tissue may also be installed at the front or rear of the meta-structure (120) for a non-uniform barrier.

[0110] In addition, without installing a front material (101), a meta-structure (120) for a non-uniform barrier can be manufactured using a material with matched impedance, and an ultrasonic probe (100) for a non-uniform barrier can be configured by forming a back material (102) - a converter (110) - a meta-structure (120) for a non-uniform barrier.

[0111] Referring to FIG. 12, an ultrasonic imaging diagnostic device (200) for a non-uniform barrier is characterized by including an ultrasonic probe (100) for a non-uniform barrier, a non-uniform barrier thickness and property extraction unit (210), an image processing unit (220), and a meta-structure control unit (230).

[0112] The above ultrasonic probe (100) for a non-uniform barrier comprises a meta-structure (120) for a non-uniform barrier manufactured by a design method (M1, M2) for a meta-structure for a non-uniform barrier, a transducer (110), and a meta-structure position adjustment unit (130) for adjusting the relative distance between the meta-structure (120) for a non-uniform barrier and the non-uniform barrier (10).

[0113] The above-mentioned non-uniform barrier thickness and material property extraction unit (210) extracts the thickness distribution and material properties of the non-uniform barrier (10) through the first ultrasonic reception signal (RS1) reflected from the non-uniform barrier (10) among the signals received through the non-uniform barrier ultrasonic probe (100).

[0114] The above image processing unit (220) converts a signal received through an ultrasonic probe (100) for an uneven barrier into an image.

[0115] The above meta-structure control unit (230) calculates the focusing speed of the barrier-penetrating ultrasound of the meta-structure (120) for the non-uniform barrier through the second ultrasonic reception signal (RS2) and determines the focusing penetration performance.

[0116] The metastructure control unit (230) can calculate the effect of the metastructure (120) for a non-uniform barrier on the image (whether the image brightness is improved, whether the signal-to-noise ratio is improved, whether the axial resolution is reduced due to multiple internal reflections within the metastructure (120) for a non-uniform barrier and the non-uniform barrier (10), whether the coherency of the signal is reduced due to ultrasonic refraction of the metastructure (120) for a non-uniform barrier, etc.) based on the current image result synthesized through the well-known delay-and-sum (DAS) technique with the received second ultrasonic reception signal (RS2).

[0117] Through this, the influence of the meta-structure (120) for a non-uniform barrier on the image can be evaluated, and the position of the meta-structure (120) for a non-uniform barrier can be adjusted using the meta-structure position adjustment unit (130). If the problem cannot be solved by position adjustment, the meta-structure (120) for a non-uniform barrier can be changed or redesigned.

[0118] The heterogeneous barrier meta-structure manufactured by the method for designing a heterogeneous barrier meta-structure of the present invention can be widely used in various non-destructive testing industrial fields that use ultrasound to penetrate heterogeneous tissues including bone tissue, soft tissue (fat, muscle, skin, etc.), gas, etc. having different physical properties, as well as in medical ultrasound imaging diagnosis and treatment, as well as in various non-destructive testing industrial fields that use ultrasound to penetrate heterogeneous physical barriers including solid (metal, ceramic, plastic) or fluid materials (composite materials, insulation materials, rust or sludge in pipes, etc.).

[0119] The method for designing a meta-structure for a non-uniform barrier of the present invention, which is configured as described above, determines the thickness of each unit cell of the meta-structure corresponding to each ultrasonic transducer element by using different arrival time differences or different arrival phase values ​​for each ultrasonic transducer element, thereby obtaining the effect of forming an ultrasonic transmission focus or improving the focusing transmittance by penetrating a non-uniform barrier such as a skull.

[0120] The ultrasound imaging device for a non-uniform barrier of the present invention, configured as described above, can obtain the effect of improving the quality of an output image by evaluating the effect of the non-uniform barrier meta-structure on an image and adjusting the relative distance between the meta-structure and the non-uniform barrier.

[0121] The scope of the present invention is not limited to the embodiments and modifications described above, but can be implemented in various forms within the scope of the appended claims. Any person skilled in the art, without departing from the spirit of the invention as claimed in the claims, may make various modifications to the invention, which are deemed to fall within the scope of the claims.

[0122] The present invention can effectively detect, measure, and diagnose objects beyond barriers using ultrasound, and can be widely used not only in the medical field but also in various non-destructive testing technology fields.

Claims

1. An ultrasonic transmission / reception step of transmitting an ultrasonic transmission signal toward an uneven barrier, and receiving a first ultrasonic reception signal reflected from the uneven barrier and incident thereon, and a second ultrasonic reception signal transmitted through the uneven barrier and then incident thereon; A non-uniform barrier thickness and property extraction step for extracting the thickness and properties of a non-uniform barrier based on the first ultrasonic reception signal; A time difference extraction step for extracting the arrival time difference for each converter element based on the second ultrasonic reception signal; and A method for designing a metastructure for a non-uniform barrier, characterized by comprising: a thickness determination step for determining the thickness of a unit cell of a metastructure to be arranged correspondingly to each converter element by using the properties of a medium through which the ultrasonic transmission signal and the second ultrasonic reception signal are transmitted, the properties of a material of a metastructure to be designed, and the arrival time difference.

2. In paragraph 1, is performed after the above thickness determination step, A design method of a metastructure for an inhomogeneous barrier, characterized in that it further includes an aberration correction step for correcting aberration of an inhomogeneous barrier based on Chebyshev polynomials or Zernike polynomials.

3. In paragraph 1, In the above time difference extraction step, The above arrival time difference is extracted by using the difference between the arrival time at which the second ultrasonic reception signal reaches each element of the converter and the arrival time at which the second ultrasonic reception signal reaches the reference element among the converter elements. The above thickness determination step is, When the sound speed in the metastructure is greater than the sound speed in the medium, the thickness of the unit cell of the metastructure to be arranged corresponding to the converter element with a relatively large arrival time difference is determined to be thicker than the thickness of the unit cell of the metastructure to be arranged corresponding to the converter element with a relatively small arrival time difference. A method for designing a metastructure for a non-uniform barrier, characterized in that when the speed of sound in the metastructure is smaller than the speed of sound in the medium, the thickness of a unit cell of the metastructure to be arranged corresponding to a converter element having a relatively large difference in arrival times is determined to be thinner than the thickness of a unit cell of the metastructure to be arranged corresponding to a converter element having a relatively small difference in arrival times.

4. In paragraph 3, In the above time difference extraction step, A design method for a meta-structure for an inhomogeneous barrier, characterized in that the arrival time of the second ultrasonic reception signal reaching each element of the converter is selected as the time at which the second ultrasonic reception signal having an amplitude greater than a preset threshold value first arrives.

5. In paragraph 3, In the above time difference extraction step, A design method for a meta-structure for an inhomogeneous barrier, characterized in that the arrival time of the second ultrasonic reception signal to each element of the converter is selected as the time at which the second ultrasonic reception signal having the maximum amplitude arrives.

6. In paragraph 3, In the above time difference extraction step, A design method for a meta-structure for an inhomogeneous barrier, characterized in that the arrival time of the second ultrasonic reception signal to each element of the converter is selected as the arrival time of the second ultrasonic reception signal having an amplitude of a preset reference value.

7. An ultrasonic transmission / reception step of transmitting an ultrasonic transmission signal toward the non-uniform barrier and receiving a first ultrasonic reception signal reflected from the non-uniform barrier and incident and a second ultrasonic reception signal transmitted through the non-uniform barrier and then incident; A non-uniform barrier thickness and property extraction step for extracting the thickness and properties of a non-uniform barrier based on the first ultrasonic reception signal; A signal conversion step for converting the second ultrasonic reception signal into a complex signal for each converter element; A phase value extraction step for extracting the phase value reached by each converter element based on the above complex signal; and A design method for a metastructure for an inhomogeneous barrier, characterized by including a thickness determination step for determining the thickness of a unit cell of a metastructure to be arranged correspondingly for each converter element by using the properties of a medium through which the ultrasonic transmission signal and the second ultrasonic reception signal are transmitted, the properties of a material of a metastructure to be designed, and the arrival phase value.

8. In paragraph 7, is performed after the above thickness determination step, A design method of a metastructure for an inhomogeneous barrier, characterized in that it further includes an aberration correction step for correcting aberration of an inhomogeneous barrier based on Chebyshev polynomials or Zernike polynomials.

9. In paragraph 7, The above thickness determination step is, When the sound speed in the metastructure is greater than the sound speed in the medium, the thickness of the unit cell of the metastructure to be arranged corresponding to the converter element having a relatively large arrival phase value is determined to be thicker than the thickness of the unit cell of the metastructure to be arranged corresponding to the converter element having a relatively small arrival phase value. A method for designing a metastructure for a non-uniform barrier, characterized in that when the sound speed in the metastructure is smaller than the sound speed in the medium, the thickness of a unit cell of the metastructure to be arranged corresponding to a converter element having a relatively large arrival phase value is determined to be thinner than the thickness of a unit cell of the metastructure to be arranged corresponding to a converter element having a relatively small arrival phase value.

10. In paragraph 9, In the above phase value extraction step, A design method for a meta-structure for an inhomogeneous barrier, characterized in that the phase value of the complex signal reaching each element of the converter is selected as the phase value of the complex signal having the maximum amplitude among the complex signals.

11. In paragraph 9, In the above phase value extraction step, A design method for a meta-structure for an inhomogeneous barrier, characterized in that the arrival phase value of the complex signal reaching each element of the converter is selected as the phase value of the complex signal corresponding to the center frequency of the ultrasonic transmission signal of the converter element.

12. In paragraph 9, In the above phase value extraction step, Calculate the average amplitude of the complex signal within a certain frequency range, A design method for a meta-structure for an inhomogeneous barrier, characterized in that the phase value at which the complex signal reaches each element of the converter is selected as the phase value of the complex signal corresponding to the average amplitude among the complex signals.

13. A meta-structure for a non-uniform barrier, characterized in that it is manufactured by the design method of the meta-structure for a non-uniform barrier described in any one of claims 1 to 12.

14. A meta-structure for a non-uniform barrier manufactured by the design method of a meta-structure for a non-uniform barrier described in any one of claims 1 to 12; and An ultrasonic probe for an uneven barrier, characterized by including a converter for converting an electrical signal into an ultrasonic signal and transmitting it or converting a received ultrasonic signal into an electrical signal.

15. In paragraph 14, An ultrasonic probe for a non-uniform barrier, characterized in that it further includes a metastructure for the non-uniform barrier and a metastructure position adjustment unit for adjusting the relative distance between the non-uniform barrier and the metastructure.

16. A non-uniform barrier meta-structure manufactured by the design method of the non-uniform barrier meta-structure described in any one of clauses 1 to 12, and an ultrasonic probe for non-uniform barrier having a transducer; and An ultrasound imaging diagnostic device for an uneven barrier, characterized by including an image processing unit that converts a signal received through the uneven barrier ultrasonic probe into an image.

17. In paragraph 16, An ultrasound imaging device for a non-uniform barrier, characterized in that it further includes a meta-structure for the non-uniform barrier and a meta-structure position adjustment unit for adjusting the relative distance between the non-uniform barrier and the meta-structure.

18. In paragraph 16, An ultrasound imaging diagnostic device for an inhomogeneous barrier, characterized by further comprising a metastructure control unit for calculating the focusing speed of the ultrasound waves penetrating the barrier of the inhomogeneous barrier metastructure through the second ultrasonic reception signal and determining the focusing penetration performance.

19. In Article 16, An ultrasound imaging diagnostic device for an uneven barrier, characterized by further comprising: an uneven barrier thickness and property extraction unit for extracting the thickness and property of the uneven barrier through the first ultrasonic reception signal.

Images