KR101995635B1 - Therapeutic ultrasound transducer using polarization reversed piezoelectric structure and driving method for manufacturing thereof - Google Patents

Abstract

Disclosed is a therapeutic ultrasound transducer using a piezoelectric structure in which a polarization is reversed and a manufacturing method thereof. In the ultrasonic transducer for therapeutic use using the polarization reversed piezoelectric structure according to an embodiment of the present invention, the first piezoelectric element and the second piezoelectric element are laminated so as to have polarization directions opposite to each other, and the electrode layer and the ground layer are laminated Only a pair of electrodes may be formed on the surface of the ultrasonic transducer to generate therapeutic ultrasonic waves having multiple frequency characteristics.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an ultrasound transducer for ultrasound transduction using a piezoelectric structure,

The present invention relates to a therapeutic ultrasound transducer using a polarization reversed piezoelectric structure and a manufacturing method thereof. More particularly, the first and second piezoelectric elements are laminated so as to have polarization directions opposite to each other, electrode layer and a ground layer are formed on a surface of a therapeutic ultrasound transducer to form an ultrasonic wave having multiple frequency characteristics by forming only a pair of electrodes and a method of fabricating the ultrasound transducer using a polarization reversed piezoelectric structure .

High intensity focused ultrasound (HIFU) therapy is a technique that focuses high energy ultrasound output from an ultrasound transducer on lesion sites such as benign and malignant tumors to produce thermal effects and cavitation Is a non-invasive treatment that induces mechanical effects and necrosis lesions. Such a high-intensity focused ultrasound therapy is useful for minimizing damage to the surrounding tissues outside the lesion tissue in comparison to the open surgery, reducing the patient's pain and improving the recovery rate The utilization rate is gradually increasing due to various advantages such as points.

However, the high-intensity focused ultrasound therapy has a disadvantage in that the treatment area is limited due to the narrow convergence region of ultrasound energy capable of necrosing the lesion, and thus, a large amount of treatment time is still consumed for necrosing lesion tissue having a large volume .

Ultrasonic therapy using multiple frequencies has been proposed as one of the measures to overcome this problem and ultrasound therapy using multiple frequencies can improve the cavitation effect by simultaneously irradiating ultrasonic energy of different frequency components to lesion tissues . However, the therapeutic ultrasound transducer using multiple frequencies may be arranged such that piezoelectric elements having different center frequencies are arranged side by side so that each piezoelectric element can form ultrasound energies of different frequencies at the same focusing point, ) Structure, but the manufacturing process is complicated. That is, in order to manufacture an ultrasound transducer for treatment using multiple frequencies including a multi-element structure, two or more pairs of electrodes are required, and the ultrasound waves of different frequencies are accurately focused on one point There are many difficulties in

On the other hand, in a transducer structure for diagnostic ultrasound, a polarization inversion layer technique capable of generating multiple frequency characteristics using only a pair of electrodes has been proposed. The above-described technique has a 1f ₀ characteristic based on the total lamination thickness of the laminated piezoelectric elements by using a displacement difference between the laminated piezoelectric elements by forming only a pair of electrode layers at the top and bottom of the laminated piezoelectric element, It is possible to simultaneously generate harmonic frequency components having multiple frequencies. It is also possible to generate only the harmonic frequency components having a multiple of the 1f ₀ characteristic by having the same displacement between the piezoelectric elements.

This polarization inversion layer technique has been utilized in a diagnostic ultrasound transducer requiring high resolution image acquisition since it has an advantage of generating broadband characteristics according to the design of the matching layer and the back layer based on the multi frequency characteristics.

Basically, diagnostic ultrasound transducers attach importance to high-resolution images through broadband characteristics, whereas therapeutic ultrasound transducers place necrosis of lesions at focus points, so even if the two transducers apply the same polarization inversion layer structure, Different.

Particularly, since the diagnostic ultrasound transducer has a large influence on the matching layer and the rear layer in order to exhibit the broadband characteristic, the ratio of the thickness of the polarization reversed layer of the ultrasonic transducer There is a need to develop an ultrasonic transducer for treatment based on an inverse polarization layer structure that is suitable for treating a lesion of a patient.

U.S. Patent No. 8,905,934 B2 entitled "Ultrasound transducer, ultrasound probe, and ultrasound diagnostic apparatus" (registered on December 9, 2014)

The first piezoelectric element and the second piezoelectric element are laminated so as to have polarization directions opposite to each other, and the electrode layer and the ground layer are laminated so that the first and second piezoelectric elements It is possible to simultaneously generate harmonic frequency characteristics having a fundamental frequency characteristic based on the total thickness and a multiple of fundamental frequency characteristics by forming only a pair of electrodes on the surface of the stacked element, The necrotic region of the ultrasonic transducer to enlarge the necrotic region of the ultrasonic transducer to reduce the operation time and to use the same pair of electrodes as the single piezoelectric element, The purpose of the present invention is to improve process yield and yield. In addition, it is also possible to provide multi-frequency characteristics and optimum thickness ratio according to different thickness ratios between the first and second piezoelectric elements in the HIFU converter using the proposed polarization inversion piezoelectric structure technique, It is an object of the present invention to provide a multi-frequency characteristic generated when a plurality of elements are used, and it is an object of the present invention to provide a HIFU converter characteristic of a proposed polarization reversed piezoelectric structure technique through application of a matching layer and a back layer, In a laminated structure of first and second piezoelectric elements having the same thickness, one piezoelectric element forms a composite structure, thereby generating multi-frequency characteristics similar to those having different thickness ratios due to the different sound speeds of the respective elements And the HIFU converter using the proposed polarization inversion structure was designed and fabricated. To verify the longitudinal it is an object.

The ultrasonic transducer for therapeutic use using the polarization-reversed piezoelectric structure according to an embodiment of the present invention includes a first piezoelectric element, a second piezoelectric element, an electrode layer, and a ground layer, and the first piezoelectric element and the second piezoelectric element are connected to each other And the electrode layer and the ground layer are stacked so as to have a polarization direction opposite to that of the ultrasonic transducer, and a pair of electrodes are formed on the surface of the ultrasonic transducer for treatment, so that the fundamental frequency characteristic based on the total thickness and the harmonic frequency characteristic Can be generated at the same time, and multiple frequency characteristics can be obtained by simultaneously generating these multiple frequency characteristics.

Further, in the therapeutic ultrasound transducer using the polarization-reversed piezoelectric structure, multiple frequency characteristics can be generated by controlling the thickness ratio of the first piezoelectric element and the second piezoelectric element. At this time, the first and second piezoelectric elements are to the ratio of the thickness of the first piezoelectric element (t ₁₎ 0.5 or less can generate a multi-frequency characteristics is formed so that in case the thickness (t ₁₎ of the total multilayer thickness (t) of the first piezoelectric element been laminated have. At this time, the first piezoelectric element having a thickness ratio of 0.5 or less may be located forward or on the opposite side of the ultrasonic propagation direction.

Also, in the therapeutic ultrasound transducer using the polarization-reversed piezoelectric structure, the energy amplitude between the fundamental frequency and the harmonic frequency characteristic can be controlled by adjusting the thickness ratio of the first piezoelectric element and the second piezoelectric element.

In the ultrasonic transducer for therapeutic use using the polarization-reversed piezoelectric structure, the first piezoelectric element and the second piezoelectric element are laminated in multilayers so that the piezoelectric structures reversed in polarization are alternately formed, and the entire The lamination thickness is made equal to the thickness ratio of the laminated piezoelectric elements while maintaining the same thickness of the single piezoelectric element having the similar fundamental frequency characteristic so that only the harmonic frequency component of the fundamental frequency component based on the total lamination thickness is generated , The frequencies of these harmonic frequency components can be increased in proportion to the number of piezoelectric elements having the same thickness which are stacked.

In addition, in the therapeutic ultrasound transducer using the polarization-reversed piezoelectric structure, a matching layer for improving the transmission efficiency of the therapeutic ultrasound transducer can be inserted. At this time, the center frequency is set to the intermediate value of the fundamental frequency and the harmonic frequencies It is possible to minimize the characteristic variation of the frequency spectrum caused by insertion of the matching layer while making the transmission efficiency.

In addition, it is possible to improve the bandwidth of each frequency component by inserting the back layer and adjusting the acoustic impedance of the inserted back layer in the therapeutic ultrasound transducer using the polarization reversed piezoelectric structure, Can be reduced in proportion to the increase of the acoustic impedance.

When the first piezoelectric element and the second piezoelectric element have different acoustic impedances in the therapeutic ultrasound transducer using the polarization reversed piezoelectric structure, the thicknesses of the two elements are different from each other due to the difference in acoustic velocities between the two elements Multiple frequency characteristics can be generated even if they are the same. For this purpose, the first and second piezoelectric elements can use piezoelectric elements having the same acoustic impedance, or by forming a composite structure in one of the first and second piezoelectric elements, So that the elements have different acoustic impedances.

In addition, in the case of forming a composite structure in any one of the first piezoelectric element and the second piezoelectric element in the therapeutic ultrasound transducer using the polarization-reversed piezoelectric structure, the amplitude control between the fundamental frequency and the harmonic frequency characteristics The ceramic volume fraction according to the pitch and pitch of the composite structure can be adjusted.

Further, in the therapeutic ultrasound transducer using the polarization-reversed piezoelectric structure, the first piezoelectric element and the second piezoelectric element may be formed in a composite structure to form a curvature for ultrasonic energy focusing.

The method for fabricating a therapeutic ultrasound transducer using the polarization reversed piezoelectric structure according to an embodiment of the present invention includes a step of lapping after confirming the polarization direction of the first piezoelectric element and the second piezoelectric element, Forming a composite structure through a dicing operation and attaching a width wise filler; lapping the polarization reversed-phase piezoelectric element in the composite structure; and bonding the first piezoelectric element and the second piezoelectric element to each other, Forming an electrode for a signal line on the surface of the polarization inversion layer piezoelectric element, forming the piezoelectric elements in a concave shape, positioning the piezoelectric elements inside the housing, connecting signal lines to the back surface of the piezoelectric elements Forming an electrode for a ground line on the front surface of the therapeutic ultrasound transducer; and attaching a connector to the housing, And < / RTI >

Since the therapeutic ultrasound transducer using the polarization reversed piezoelectric structure according to an embodiment of the present invention can be manufactured using only a pair of electrodes in the same manner as a general single piezoelectric element structure, It is possible to reduce the manufacturing method and improve the production yield by reducing the number of electrodes and the number of ground layers required in the piezoelectric element structure.

The ultrasonic transducer for therapeutic use using the polarization reversed piezoelectric structure according to an embodiment of the present invention may adjust the thickness ratio of the piezoelectric elements stacked or form a complex structure of one piezoelectric element among the stacked piezoelectric elements, It is possible to generate multiple frequency characteristics using different acoustic impedance differences, which can improve the cavitation effect in the lesion tissue during high intensity ultrasound therapy, thereby shortening the treatment time compared to a general high intensity ultrasound transducer .

The therapeutic ultrasound transducer using the polarization-reversed piezoelectric structure according to an embodiment of the present invention can be used for various purposes such as adjusting the amplitude between multiple frequencies generated in accordance with the number and thickness ratio of the piezoelectric elements to be laminated and the acoustic impedance difference, ₀ and 2f ₀ combinations, 1f ₀ and 3f ₀ combinations, etc.) are possible.

The therapeutic ultrasound transducer using the polarization reversed piezoelectric structure according to an embodiment of the present invention can generate only a single frequency component or generate multiple frequencies by appropriately controlling the parameters such as the number of piezoelectric elements and the thickness ratio Therefore, it is possible to generate various multi-frequency or single-frequency harmonics depending on the conditions of the treatment object

Since the therapeutic ultrasound transducer using the polarization reversed piezoelectric structure according to an embodiment of the present invention can generate high frequencies even with a thick piezoelectric element, it is difficult to manufacture due to the thin piezoelectric element thickness generated in manufacturing a high frequency transducer And it is possible to generate various multi-frequency or single-frequency harmonics even through various combinations of piezoelectric elements having complex and bulk structures in particular.

The therapeutic ultrasound transducer using the polarization-reversed piezoelectric structure according to an embodiment of the present invention sets the center frequency used for deriving the thickness of the matching layer to be an intermediate value of multiple frequencies by further attaching the matching layer, And the distortion of the frequency band caused by the matching layer attachment in the frequency spectrum can be minimized.

The therapeutic ultrasound transducer using the polarization-reversed piezoelectric structure according to an embodiment of the present invention further includes a rear layer, thereby increasing the bandwidth of the frequency characteristic of the multi-frequency characteristic in the frequency spectrum according to the change of the rear layer acoustic impedance . ≪ / RTI >

The therapeutic ultrasound transducer using the polarization reversed piezoelectric structure according to an embodiment of the present invention can improve the focusing function by using the concave shape of the piezoelectric element or by using the concave shape lens.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. It is to be understood, however, that the technical features of the present invention are not limited to the specific drawings, and the features disclosed in the drawings may be combined with each other to constitute a new embodiment.
FIG. 1 (a) shows a therapeutic ultrasound transducer 100 of a single piezoelectric device structure, and FIG. 1 (b) is a cross-sectional view of a two- Ultrasonic transducer 180. Fig.
2 (a) shows a case where a 0.5-thickness ratio (t ₁ = 0.85 mm, t ₂ = 0.85 mm) is obtained by using a finite element analysis-based simulation in a therapeutic ultrasound transducer 180 using a polarization- (T ₁ = 0.51 mm, t ₂ (t ₂ )) using a finite element analysis-based simulation in a therapeutic ultrasound transducer 180 using a polarization reversed piezoelectric structure. = 1.19 mm).
3 (a) shows a case where a 0.5-thickness ratio (t ₁ = 0.85 mm, t ₂ = 0.85 mm) is obtained by using a finite element analysis-based simulation in a therapeutic ultrasound transducer 180 using a polarization- (T ₁ = 0.51 mm, t ₁ = 0.51 mm) using a finite element analysis-based simulation in a therapeutic ultrasound transducer 180 using a polarization-reversed piezoelectric structure, t ₂ = 1.19 mm) at the focal point.
4 (a) shows a case in which a 0.5-thickness ratio (t ₁ = 0.85 mm, t ₂ = 0.85 mm) is used in a treatment ultrasound transducer 180 using a polarization reversed piezoelectric structure using a finite element analysis- FIG. 4 (b) shows the result of transforming the ultrasound pressure amplitude at the focusing point of the ultrasonic transducer 180 into a frequency spectrum. FIG. 4 (b) (T ₁ = 0.51 mm, t ₂ = 1.19 mm) at the focal point when the ultrasonic pressure amplitude is converted into the frequency spectrum.
5 (a), 5 (b) and 5 (c) show the ultrasonic pressure at the focusing point when the therapeutic ultrasonic transducer 180 using the polarization reversed piezoelectric structure has a thickness ratio of 0.2, 0.15 and 0.1.
6 (a), 6 (b) and 6 (c) show ultrasonic pressures at a focusing point when the therapeutic ultrasonic transducer 180 using a polarization reversed piezoelectric structure has a thickness ratio of 0.2, 0.15 and 0.1, It shows the result of conversion.
Of Figure 7 (a) is an embodiment in the stacked in therapeutic ultrasound transducer (180) for the polarization inversion layer structure according to the first piezoelectric elements and second piezoelectric elements, the same 0.5 weight ratio to each other thicknesses of the present invention (t ₁ = 0.85 mm and t ₂ = 0.85 mm), and each piezoelectric element shows a transformer formed in a monolithic structure, and FIG. 7 (b) shows a transformer having a polarization inverse layer structure according to an embodiment of the present invention (T ₁ = 0.85 mm, t ₂ = 0.85 mm) having the same thicknesses of the piezoelectric elements stacked in the piezoelectric element 180 are formed in the composite structure 220 so that only one piezoelectric element is formed And a therapeutic ultrasound transducer 230 having a polarization reversed-layer structure.
FIG. 8A shows the electrical impedance results estimated using the finite element analysis based simulation in the structure of the converter 180 of FIG. 7A, FIG. The results of the electrical impedance estimation using the finite element analysis based simulation in the converter 230 structure of FIG.
9 (a) shows the ultrasonic pressure at the focusing point using the finite element analysis-based simulation in the structure of the converter 180 of Fig. 7 (a), Fig. 9 (b) The ultrasound pressure at the focal point is shown using finite element analysis based simulation in the converter 230 structure.
10 (a) shows a result obtained by converting the ultrasonic pressure amplitude signal into a frequency spectrum at a focal point using the finite element analysis-based simulation in the structure of the converter 180 of FIG. 7 (a) b) shows the result of converting the ultrasonic pressure amplitude signal to the frequency spectrum at the focal point using the finite element analysis based simulation in the structure of the converter 230 of FIG. 7 (b).
(A), (b) in FIG. 11, (c) depending on each 1f _0, 1.5f _0, 2f ₀ center frequency in the ultrasonic transducer 180 for the treatment of a polarization inversion layer structure according to an embodiment of the present invention And a single matching layer of different thicknesses derived respectively.
Figs. 12 (a), 12 (b) and 12 (c) show the results obtained by converting the pressure at the focusing point in Figs. 11 (a), 11 (b) and 11 (c) into a frequency spectrum.
13 (a), 13 (b) and 13 (c) illustrate a case in which rear surface layers having various acoustic impedances are attached in the therapeutic ultrasound transducer 180 of the polarization inverse layer structure according to the embodiment of the present invention, Lt; / RTI >
Figs. 14 (a), 14 (b) and 14 (c) show the results obtained by converting the pressure at the focusing point in Figs. 13 (a), 13 (b) and 13 (c) into a frequency spectrum.
FIG. 15 shows a therapeutic ultrasound transducer 260 of a three-stage laminated polarized reversed-phase structure according to an embodiment of the present invention.
Figure 16 shows the pressure at the focal point through the thickness ratio control of each of the piezoelectric elements in the structure of the therapeutic ultrasound transducer (260) of the three-pole,
FIG. 17 shows the result of converting the pressure amplitude at the focal point to a relative frequency spectrum through the adjustment of the thickness ratio of the piezoelectric elements in the structure of the therapeutic ultrasound transducer 260 in the three-pole polarization inversion layer structure.
18 is a diagram illustrating a prototype of the transducer 180 of the polarization inversion layer structure of the two-layer laminated structure, which is designed using finite element analysis-based simulation.
19 shows a prototype manufacturing process of a therapeutic ultrasound transducer 180 having a polarization inversion layer structure according to an embodiment of the present invention.
FIG. 20 is a flowchart showing a method of manufacturing a therapeutic ultrasound transducer 180 using a polarization-reversed piezoelectric structure according to an embodiment of the present invention.
21 (a) shows a finite element analysis-based design of FIG. 18, a prototype of a therapeutic ultrasound transducer 180 having a polarization inverse layer structure completed according to the manufacturing methods of FIGS. 19 and 20, (b) shows a cross-sectional view of the prototype ultrasound transducer 180 of the completed polarization inverse layer structure.
22 (a) and 22 (b) illustrate an electric impedance and an impulse (impulse) to the prototype of the ultrasonic transducer 180 of the polarization inverse layer structure for the performance verification of the prototype of the ultrasonic transducer 180 of the polarization inversion layer structure of FIG. ) 2-way pulse echo response.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

The terms used in this specification will be briefly described and the present invention will be described in detail.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. Also, in certain cases, there may be a term selected arbitrarily by the applicant, in which case the meaning thereof will be described in detail in the description of the corresponding invention. Therefore, the term used in the present invention should be defined based on the meaning of the term, not on the name of a simple term, but on the entire contents of the present invention.

When an element is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements as well, without departing from the spirit or scope of the present invention. Also, the terms "part," " module, "and the like described in the specification mean units for processing at least one function or operation, which may be implemented in hardware or software or a combination of hardware and software . In addition, when a part is referred to as being "connected" to another part throughout the specification, it includes not only "directly connected" but also "connected with other part in between".

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

FIG. 1 (a) shows a therapeutic ultrasound transducer 100 of a single piezoelectric device structure, and FIG. 1 (b) is a cross-sectional view of a two- Ultrasonic transducer 180. Fig.

Referring to FIG. 1A, the transducer 100 of a general single piezoelectric device structure basically includes a polarization direction 110 in a piezoelectric device, and the polarization direction 110 is opposite to the polarization direction 110 Or by forming the electrodes 120 and 130 so that they have the same polarity to each other, the transducer 100 of a single piezoelectric element structure can be driven. At this time, the center frequency of the ultrasonic energy generated from the transducer 100 of the single piezoelectric element structure may be mainly represented by the 1f ₀ characteristic based on the total thickness t.

1 (b), a therapeutic ultrasound transducer 180 having a polarization inversion layer structure according to an embodiment of the present invention includes piezoelectric elements 140 and 150 having different polarization directions 160 and 170, And the pair of electrodes 120 and 130 are formed on the surface of the transducer 180 having the polarization inversion layer structure, so that the transducer 180 having the polarization inverse layer structure can be driven.

That is, the therapeutic ultrasound transducer 180 using the polarization reversed piezoelectric structure according to an embodiment of the present invention includes a first piezoelectric element 140, a second piezoelectric element 150, an electrode layer 120, And the first piezoelectric element 140 and the second piezoelectric element 150 are stacked so as to have opposite polarization directions 160 and 170 and the electrode layer 120 and the ground layer 130 are stacked, Only a pair of electrodes may be formed on the surface of the element where the first piezoelectric element and the second piezoelectric element are stacked to generate ultrasonic waves having multiple frequency characteristics.

In the therapeutic ultrasound transducer 180 using the polarization-reversed piezoelectric structure, the first piezoelectric element has a thickness smaller than that of the second piezoelectric element and is located opposite to the direction of propagation of the ultrasonic wave, and the first piezoelectric element and the second piezoelectric element By forming electrodes on the bonding surface of the piezoelectric element and bonding them to increase the electrical conductivity, efficient multi-frequency characteristics can be generated.

For example, the therapeutic ultrasound transducer 180 using the polarization-reversed piezoelectric structure may adjust the thickness ratio t of the first piezoelectric element 140 and the second piezoelectric element 150, the second harmonic frequency (2f ₀₎ to generate a multi-frequency properties, including properties or the second harmonic frequency (2f ₀₎ only singly characteristics and 1f ₀ characteristic that is based on having a second multiple of the 1f ₀ characteristics of .

For example, the sole occurrence of the second harmonic frequency (2f ₀ ) characteristic alone is the ratio of the thickness t ₁ of the piezoelectric element located on the opposite side in the ultrasonic propagation direction to the thickness t of the total piezoelectric elements, as a precaution, the ratio of the thickness t ₁ and the total thickness t may be realized by controlling not more than 0.5.

That is, in the therapeutic ultrasound transducer 180 using the polarization-reversed piezoelectric structure, the first piezoelectric element and the second piezoelectric element can be adjusted in thickness by using the same piezoelectric element or using different types of piezoelectric elements So that efficient multi-frequency characteristics can be generated.

FIGS. 2 to 4 are graphs showing finite element analysis (finite element analysis) to show multifrequency or harmonic frequency characteristics that can be generated in the therapeutic ultrasound transducer 180 using the polarization reversed piezoelectric structure according to an embodiment of the present invention. element analysis-based simulation, the electrical impedance at a 0.5-thickness ratio or a 0.3-thickness ratio, pressure at the focal point, and frequency spectral results at that pressure.

Here, in order to use the finite element analysis based simulation, it is assumed that the piezoelectric element is composed of a circular type. In order to generate 1.2 MHz 1f ₀ widely used for HIFU treatment, the thickness of the entire piezoelectric element is 1.7 mm . The device width w is assumed to be 60 mm, which is about 30 times the total thickness, for ideal radial vibration mode driving, and the piezoelectric device is assumed to have a concave shape for focusing the ultrasonic energy.

The thickness ratio is a ratio of the thickness t ₁ of the first piezoelectric element 140 to the total thickness t. For example, after the thickness t ₁ of the first piezoelectric element 140 is laminated to 0.85 mm, the thickness t ₂ of the second piezoelectric element 150 is set to The total thickness of the first piezoelectric element 140 and the second piezoelectric element 150 becomes t = 1.7 mm and the total thickness t of the first piezoelectric element 140 ) Thickness t ₁ = 0.85 mm is 0.5.

That is, FIG. 2 (a) shows a 0.5-thickness ratio (t ₁ = 0.85 mm, t ₂ = 0.85 mm) using a finite element analysis-based simulation in a therapeutic ultrasound transducer 180 using a polarization- (T ₁ = 0.51 mm, t ₁ = 0.51 mm) using a finite element analysis-based simulation in a therapeutic ultrasound transducer 180 using a polarization-reversed piezoelectric structure. t ₂ = 1.19 mm).

Table 1 below is a table showing resonance frequency values and anti-resonance frequency values and impedance values derived from the respective frequencies derived from FIGS. 2 (a) and 2 (b).

Referring to FIGS. 2 (a), 2 (b) and 1, it can be seen that only a 2f ₀ characteristic having a 2.4 MHz resonance frequency is generated at a thickness ratio of 0.5, and a resonance frequency of 1.28 MHz at a thickness ratio of 0.3 this characteristic has 1f _0, 3f ₀ characteristics of the 2f ₀ attribute and 3.96 MHz the resonance frequency of the 2.55 MHz resonant frequency can be confirmed to be occurring at the same time.

That is, the therapeutic ultrasound transducer 180 using the polarization-reversed piezoelectric structure according to an embodiment of the present invention can adjust the thickness ratio of the first piezoelectric element 140 and the second piezoelectric element 150, Can be generated.

3 (a) shows a case where a 0.5-thickness ratio (t ₁ = 0.85 mm, t ₂ = 0.85 mm) is obtained by using a finite element analysis-based simulation in a therapeutic ultrasound transducer 180 using a polarization- (T ₁ = 0.51 mm, t ₁ = 0.51 mm) using a finite element analysis-based simulation in a therapeutic ultrasound transducer 180 using a polarization-reversed piezoelectric structure, t ₂ = 1.19 mm) at the focal point.

Table 2 below is a table showing the maximum pressure values at the focal points of the respective thickness ratios derived from FIGS. 3 (a) and 3 (b).

3 (a) and 3 (b) show the ultrasound pressure immediately after returning from the ideal reflector at the focusing point of the therapeutic ultrasound transducer 180 using the polarization-reversed piezoelectric structure, Table 2], it can be seen that the pressure at the focal point is 0.383 MPa at a 0.5-thickness ratio, and 0.513 MPa at the focal point at the 0.3-thickness ratio.

4 (a) shows a case in which a 0.5-thickness ratio (t ₁ = 0.85 mm, t ₂ = 0.85 mm) is used in a treatment ultrasound transducer 180 using a polarization reversed piezoelectric structure using a finite element analysis- FIG. 4 (b) shows the result of transforming the ultrasound pressure amplitude at the focusing point of the ultrasonic transducer 180 into a frequency spectrum. FIG. 4 (b) (T ₁ = 0.51 mm, t ₂ = 1.19 mm) at the focal point when the ultrasonic pressure amplitude is converted into the frequency spectrum.

4 (a) and 4 (b) show the results obtained by converting the pressure amplitudes of 0.5 thickness ratio and 0.3 thickness ratio derived from FIGS. 3 (a) and 3 (b) into frequency spectrums, respectively.

In other words, in order to analyze the frequency components outputted for each thickness ratio in the therapeutic ultrasound transducer 180 using the polarization-reversed piezoelectric structure, the frequency spectrum of FIGS. 4A and 4B is based on a finite element analysis Simulation results show that the pressure amplitudes are converted into frequency spectra for each thickness ratio.

Table 3 below is a table showing the center frequencies of the 1f ₀ , 2f ₀ , and 3f ₀ frequency characteristics and the dB at the peak point of the center frequency derived from FIGS. 4 (a) and 4 (b).

Referring to FIGS. 4 (a), 4 (b) and 3, the frequency characteristics generated by the respective thickness ratios are similar to the electrical impedance characteristics of FIG. 2 (a) Can be obtained.

That is, referring to FIGS. 4A, 4B and 3, the ratio of 0.5 thickness of the therapeutic ultrasound transducer 180 using the polarization-reversed piezoelectric structure has a center frequency of 2.67 MHz (0 dB) in the 2f _0, and only the characteristic confirmed that derived, 0.3 weight ratio with which the center frequencies of each of 1.34 MHz (-6.71 dB), 2.67 MHz (0 dB), 4.02 MHz (-2.25 dB) 1f 0, 2f ₀ , and 3f ₀ characteristics are generated at the same time.

2 through 4, the therapeutic ultrasound transducer 180 of the polarization inverse layer structure is formed by a pair of electrodes 120 and 130 identical to the conventional transducer 100 of the single piezoelectric device structure, It can be confirmed that it can be driven.

In addition, the therapeutic ultrasound transducer 180 having a polarization inversion layer structure can generate multiple frequency characteristics in comparison with the conventional transducer 100 of a single piezoelectric device structure, thereby improving the cavitation effect in tissue.

That is, by using the therapeutic ultrasound transducer 180 having the polarization inverse layer structure according to the embodiment of the present invention, it is possible to shorten the HIFU treatment time and to generate only the harmonic frequency characteristic by controlling the same thickness ratio, The difficulty in fabrication due to the thin thickness generated in the manufacture of the transducer for high frequency therapy can be improved.

Referring to FIGS. 4B and 3, the 2f ₀ characteristic has a maximum value at a ratio of 0.3 thickness, and then 3f ₀ and 1f ₀ have values of -2.25 dB and -6.71 dB, respectively. . This difference in peak points can be adjusted by performing a thickness optimization that yields equally peak points between the required frequency components through a finer adjustment than the proposed 0.3 thickness ratio.

5 to 6 are graphs showing the relationship between the thickness ratio of the piezoelectric elements stacked up to 0.2, and the thickness ratio of the piezoelectric elements stacked by using the finite element analysis based simulation in the therapeutic ultrasound transducer 180 using the polarization reversed piezoelectric structure according to an embodiment of the present invention. 0.15, and 0.1, and the result of converting the pressure immediately after returning by the ideal reflector at the focusing point and the pressure into the frequency spectrum.

5 (a), 5 (b) and 5 (c) show the ultrasound pressure at the focusing point when the therapeutic ultrasound transducer 180 using the polarization reversed piezoelectric structure has the ratio of 0.2, 0.15, and 0.1 thickness , 6 (a), 6 (b), and 6 (c) show ultrasonic pressures at a focusing point when the therapeutic ultrasonic transducer 180 using a polarization reversed piezoelectric structure has a thickness ratio of 0.2, 0.15 and 0.1, .

The following Table 4 and Table 5 show the relationship between the maximum pressure per thickness ratio of FIGS. 5A, 5B and 5C and the frequency of the frequency of FIGS. 6A, 6B, Is a table showing peak points of center frequency and center frequency of characteristics.

Referring to FIGS. 5 (a), 5 (b), 5 (c) and 4, the thickness ratios are reduced to 0.2, 0.15 and 0.1 so that the pressures are 0.475, 0.368 and 0.312 MPa, Referring to FIGS. 6 (a), 6 (b), 6 (c) and 5, the 0.2-thickness ratio in the frequency spectrum is -2.2 dB between the 1 f ₀ and 2 f ₀ characteristics It decreased 0.15 has a maximum value in the thickness ratio characteristic 1f _0, 2f _0, the peak of the characteristic point is decreased -2.04 dB, and the results are quite similar to the thickness ratio of the peak value of 0.15 1f and 3f _{0 0} properties in the thickness ratio 0.1 And the characteristics of 1f ₀ and 3f ₀ are 0.8 dB.

5 to 6, the therapeutic ultrasound transducer 180 having a polarization inverse layer structure according to an embodiment of the present invention adjusts the ratio of multi-frequency characteristics generated at the focal point by adjusting the thickness ratio And it has an advantage of providing a therapeutic ultrasound transducer having various multi frequency characteristics ratio only by adjusting the thickness between the piezoelectric elements stacked according to the kind of the lesion tissue and the environment at the time of HIFU treatment .

In addition, the therapeutic ultrasound transducer 180 of the polarization inverse layer structure according to an embodiment of the present invention is generated in accordance with the thickness ratio by controlling the thickness ratio of the first piezoelectric element 140 and the second piezoelectric element 150 The energy amplitude between multiple frequencies can be adjusted.

Of Figure 7 (a) is an embodiment in the stacked in therapeutic ultrasound transducer (180) for the polarization inversion layer structure according to the first piezoelectric elements and second piezoelectric elements, the same 0.5 weight ratio to each other thicknesses of the present invention (t ₁ = 0.85 mm and t ₂ = 0.85 mm), and each piezoelectric element shows a transformer formed in a monolithic structure, and FIG. 7 (b) shows a transformer having a polarization inverse layer structure according to an embodiment of the present invention (T ₁ = 0.85 mm, t ₂ = 0.85 mm) having the same thicknesses of the piezoelectric elements stacked in the piezoelectric element 180 are formed in the composite structure 220 so that only one piezoelectric element is formed And a therapeutic ultrasound transducer 230 having a polarization reversed-layer structure.

That is, FIG. 7A is a cross-sectional view of a transducer formed to have a 0.5-thickness ratio by laminating the first piezoelectric element 140 and the second piezoelectric element 150 of FIG. 1B in the same thickness of 0.85 mm. And FIG. 7 (b) shows the case where the thicknesses of the first piezoelectric element 140 and the second piezoelectric element 150 in FIG. 1 (b) are equal to 0.85 mm, And the second piezoelectric element is configured to have the composite structure 210.

7 (b) is a diagram showing a structure capable of simultaneously generating multiple frequency characteristics of 1f ₀ and 2f ₀ , and FIGS. 7 (a) and 7 (b) (B) of FIG. 7, it is possible to induce the sound velocity between the stacked piezoelectric elements to be different from each other by forming only one piezoelectric element into the composite structure 210, Unlike the transformer 180 structure of FIG. 7 (a) that generates only the 2f ₀ frequency characteristic by generating different time differences in ultrasonic energy, the structure of the transformer 230 of FIG. 7 (b) ₀ and 2f ₀ frequency characteristics at the same time.

In order to use the finite element analysis based simulation in the transformer 230 having the structure of FIG. 7B, the same specifications as those of the transformer designed in FIGS. 2 to 4 are taken into consideration. As shown in FIG. 7B, It is assumed that the second piezoelectric element 210 located at the upper end of the stacked piezoelectric elements is formed as an annular 2-2 composite structure. In this case, the pitch and the kerf 190 width were set to 0.7 mm and 0.2 mm, respectively, so that the ceramic volume fraction was set to about 29%.

The following Table 6 is a table showing the main properties of the filler 190 applied to the structure of the transformer 230 of FIG. 7 (b) to use the simulation based on the finite element analysis, and Table 7 The main physical property values of the bulk type piezoelectric elements 140 and 150 as the monolithic structure of FIG. 7A and the main physical properties of the piezoelectric element 210 as the 2-2 composite structure formed at the upper end of FIG. Are compared with each other in the same thickness.

Referring to Table 7, it can be seen that the piezoelectric element 210 formed of the 2-2 composite structure has a reduced acoustic impedance compared to the bulk type piezoelectric elements 140 and 150, and in particular, In the case of the bulk type, they have the same longitudinal velocity but they have different acoustic velocities of 996 m / s difference by forming the composite structure.

FIG. 8A shows the electrical impedance results estimated using the finite element analysis based simulation in the structure of the converter 180 of FIG. 7A, FIG. The results of the electrical impedance estimation using the finite element analysis based simulation in the converter 230 structure of FIG.

Table 8 below is a table showing resonance frequency values and anti-resonance frequency values derived from FIGS. 8 (a) and 8 (b) and impedance values derived from the respective frequencies.

8 (a) shows the impedance result of the transducer having the piezoelectric element laminated structure between the bulk type at the thickness ratio of 0.5 and FIG. 8 (b) shows the impedance result of the transducer having the piezoelectric element laminated structure at the thickness ratio of 0.5. Indicates the impedance result of the converter.

8A and 8B, the results of FIG. 8A show that when the thickness ratio is 0.5 in the transformer structure of FIG. 1B (FIGS. 2A and 2B) 1>) and when to check that it has the same effect, with reference to (b) and <Table 8> of Figure 8, in the case of forming one of the piezoelectric elements in the composite structure of the same thickness ratio, 1f ₀ and 2f ₀ And the resonance frequencies of the respective characteristics are 1.1 MHz and 2.13 MHz, and the frequency characteristics similar to those of the multi-frequency obtained through the adjustment of the different thickness ratios in the conventional converter 180 Can be confirmed.

In other words, the conventional transducer 180 can acquire multiple frequency characteristics through different thickness ratio control. However, the therapeutic ultrasound transducer 230 using the polarization reversed piezoelectric structure according to an embodiment of the present invention by forming the one of the piezoelectric elements in the same thickness ratio in the composite structure, it is possible to obtain the multi-frequency characteristics such as the characteristics of the 1f ₀ and 2f ₀ is generated at the same time.

9 (a) shows the ultrasonic pressure at the focusing point using the finite element analysis-based simulation in the structure of the converter 180 of Fig. 7 (a), Fig. 9 (b) The ultrasound pressure at the focal point is shown using finite element analysis based simulation in the converter 230 structure.

Table 9 below is a table showing the maximum pressure value at the focusing point derived from Figs. 9 (a) and 9 (b).

9A and 9, the maximum pressure of 0.383 MPa in FIG. 9A is obtained when the thickness ratio is 0.5 in the transducer structure of FIG. 1B 9 and FIG. 9, the maximum pressure of FIG. 9 (b) is estimated to be 0.593 MPa, and FIG. 9 (b) the maximum pressure of 0.383 MPa in Fig. 3 (a) and the maximum pressure of 0.513 MPa at the focal point measured at the thickness ratio 0.3 in Fig. 3 (b) and Table 2.

10 (a) shows a result obtained by converting the ultrasonic pressure amplitude signal into a frequency spectrum at a focal point using the finite element analysis-based simulation in the structure of the converter 180 of FIG. 7 (a) b) shows the result of converting the ultrasonic pressure amplitude signal to the frequency spectrum at the focal point using the finite element analysis based simulation in the structure of the converter 230 of FIG. 7 (b).

The following Table 10 is a table summarizing the results of the frequency spectrum derived from FIGS. 10 (a) and 10 (b).

10 (a), 10 (b) and 10, the junction structure between the bulk type piezoelectric elements 140 and 150 having the same thickness ratio in the structure of the converter 180 of FIG. 7 (a) Only one harmonic frequency characteristic is generated while the composite structure 210 is formed in the structure of the transformer 230 of Figure 7B, when formed from a 210) it has confirmed that the multi-frequency characteristics of the 1f ₀ and 2f ₀ is derived at the same time.

At this time, it can be seen that the center frequency of each characteristic derived from the frequency spectrum of FIG. 10 (b) is similar to the center frequencies of the multi-frequency characteristic derived from the conventional control of the thickness ratio.

That is, the therapeutic ultrasound transducer 230 of the polarization inversion layer structure including the piezoelectric element of the complex structure according to the embodiment of the present invention can generate multiple frequency characteristics of 1f ₀ and 2f ₀ at the same thickness ratio.

For example, in a therapeutic ultrasound transducer 180 using a polarization reversed piezoelectric structure, the first piezoelectric element and the second piezoelectric element are laminated to have the same thickness ratio, and at least one of the piezoelectric elements forms a composite structure So that multiple frequency characteristics can be generated.

Although a 2-2 composite structure is described as an example of a composite structure according to an embodiment of the present invention, it is not necessary to limit the composite structure to a 2-2 composite structure in order to express multi-frequency characteristics. And may include various types of complex structures.

In addition, the expression of the multi-frequency characteristic at the same thickness ratio of the therapeutic ultrasound transducer 230 of the polarization inversion layer structure including the piezoelectric elements of the composite structure is not limited to the ceramic volume fraction, By varying the acoustic impedance of the bulk type transducer through the adjustment of the ceramic volume fraction, multiple frequency characteristics can be expressed.

That is, the expression of the multiple frequency characteristics at the same thickness ratio can be achieved by applying various structures capable of changing the sound velocity of the bulk type transducer, and the piezoelectric element 210 having the composite structure may be disposed at any position Frequency characteristics can be expressed.

That is, since the expression of the multi-frequency characteristic of the present invention utilizes the difference in acoustic impedance between the two piezoelectric elements, both piezoelectric elements can have a composite structure having a different acoustic impedance or a bulk-type structure having different acoustic impedances.

For example, in the therapeutic ultrasound transducer 180 using the polarization-reversed piezoelectric structure, the first piezoelectric element 140 and the second piezoelectric element 150 are formed to have different acoustic impedance values, Can be generated.

Further, in the therapeutic ultrasound transducer 180 using the polarization-reversed piezoelectric structure, the first piezoelectric element and the second piezoelectric element may form a complex structure, or only one piezoelectric element may form a complex structure, by adjustment of the ceramic volume fraction in accordance with the pitch and the pitch it can be adjusted to the amplitude of the 1f _0, 2f _0, 3f ₀ frequency characteristics of the ultrasonic transducer for the treatment.

In order to improve the converging function of the ultrasonic waves in the therapeutic ultrasound transducer 180 using the polarization-reversed piezoelectric structure, the shapes of the first piezoelectric element 140 and the second piezoelectric element 150 are used to perform ultrasound energy focusing To form a curvature for the &lt; / RTI &gt;

In the conventional ultrasound transducer 100 of the conventional single piezoelectric element structure, the thickness corresponding to a quarter wavelength is selected as the thickness of the matching layer based on the generated single frequency. In the ultrasonic transducer 100 according to the embodiment of the present invention, The effective thickness of the matching layer of the therapeutic ultrasound transducer with frequency characteristics should be determined using a different method than the conventional method.

(A), (b) in FIG. 11, (c) depending on each 1f _0, 1.5f _0, 2f ₀ center frequency in the ultrasonic transducer 180 for the treatment of a polarization inversion layer structure according to an embodiment of the present invention 12 (a), 12 (b) and 12 (c) show the pressure immediately after returning by the ideal reflector at the focal point in the case of including a single matching layer of different thicknesses derived. ), (b), and (c) into the frequency spectrum.

Here, the physical properties of the single matching layer included in (a), (b), (c) of Figure 11 are as follows: <Table _{11>, 1f 0, 1.5f 0} , 2f 0 is derived by the central frequency The thickness of each single matching layer was 0.227, 0.303, and 0.454 mm, respectively, and the assumption was made that the stacked piezoelectric elements had a ratio of 0.2 thickness using the finite element analysis based simulation.

<Table 12> is for each 1f _0, 1.5f _0, 2f ₀ center frequency in (a), (b), (c) an ultrasonic transducer (180) for the polarization treatment of the inversion layer structure as a result of the 11 And the maximum pressure of the ultrasonic wave according to the thickness of each matching layer derived.

Referring to FIGS. 11 (a), 11 (b), 11 (c) and 12, the maximum pressure of the transducer 180 including the matching layer is 0.727, 0.793 and 0.672 MPa, respectively And it can be confirmed that the transmission efficiency is improved by increasing the maximum pressure value as a whole compared with the amplitude due to the adhesion of the matching layer.

If (a), (b), (c) of FIG. 12, refer to (a), (b), (c) for each 1f _0, 1.5f _0, 2f ₀ represents the frequency spectrum of the result, FIG. 12, It can be seen that deformation occurs in the bandwidth of the frequency characteristics according to the applied center frequency.

For example, considering only 1f ₀ and 2f ₀ in the case of 1.5f ₀ , it can be seen that the difference between the peak points of the two center frequencies is minimized to -1.59 dB.

That is, unlike a diagnostic ultrasound transducer requiring a broadband characteristic, when the frequency spectrum is deformed due to adhesion of the matching layer, that is, when the bandwidth of the center frequency is widened, The ultrasonic energy generated at the focal point is attenuated, and these results can be confirmed by the results shown in Table 13 below.

Table 13 below is a table showing dB of center frequency and peak point for 1f ₀ , 2f ₀ , and 3f ₀ peak points generated according to reference frequencies 1f ₀ , 1.5f ₀ , and 2f ₀ for each center frequency.

Thus, in general, the matching layer in order to minimize the deformation of the frequency spectrum generated during the attachment, in one embodiment the polarization inversion layer ultrasonic transducer 180 for the treatment of a structure according to the present invention, the matching based on the center frequency of 1.5f ₀ The thickness of the layer can be derived. Referring to Table 11, it can be seen that the center frequency of 1.5f ₀ is higher than the center frequency of 1f ₀ and 2f ₀ , have.

That is, in order to determine the value of the center frequency used in the design of the matching layer, the therapeutic ultrasound transducer 180 of the polarization inverse layer structure according to an embodiment of the present invention determines the center frequency using the intermediate value of the multiple frequencies By further including the matching layer having the thickness corresponding to the determined center frequency, the transmission efficiency of the therapeutic ultrasound transducer 180 of the polarization inverse layer structure can be further improved, and the deformation of the frequency characteristic generated in the frequency spectrum can be minimized .

13 (a), 13 (b) and 13 (c) illustrate a case in which rear surface layers having various acoustic impedances are attached in the therapeutic ultrasound transducer 180 of the polarization inverse layer structure according to the embodiment of the present invention, 14 (a), 14 (b) and 14 (c) show the results obtained by converting the pressure at the focal point in FIGS. 13 (a) .

13 and 14 illustrate a structure in which a rear surface layer having an acoustic impedance of 3.1, 6.2, and 10 Mrayls is attached to a therapeutic ultrasound transducer 180 having a polarization inversion layer structure, It is a result of assuming that the stacked piezoelectric elements have a ratio of 0.2 thickness.

In addition, the back layer having acoustic impedances of 3.1, 6.2, and 10 Mrayls, respectively, can be mixed with EPOTEK301 and the EPOTEK301 and tungsten powder to form a back layer having various acoustic impedance values.

Table 14 below shows the maximum pressure at the focusing point when the back layer having the acoustic impedance of 3.1, 6.2, and 10 Mrayls is attached to the therapeutic ultrasound transducer 180 of the polarization inversion layer structure, Table 15] shows the -6 dB bandwidth of the 1f ₀ and 2f ₀ characteristics in the frequency spectrum for each acoustic impedance of 3.1, 6.2, and 10 Mrayls.

13, when the back layer is attached to the therapeutic ultrasound transducer 180 having the polarization inverse layer structure, the pressure at the focal point is reduced compared with that before the attachment, It can be seen that the 1f ₀ and 2f ₀ peak points are perfectly equal to each other. That is, as the acoustic impedance increases, the bandwidths of the center frequencies are improved and the valleys generated between the center frequencies are reduced.

13 and 14, the therapeutic ultrasound transducer 180 of the polarization inversion layer structure according to an embodiment of the present invention can minimize the energy difference between the multiple frequency characteristics through attachment of the rear layer , The bandwidth of the center frequency and the depth of the valleys between the center frequencies are reduced as the higher acoustic impedance is attached, and the frequency band to be applied to the converter can be utilized more widely and widely.

That is, the therapeutic ultrasound transducer 180 of the polarization inverse layer structure according to an embodiment of the present invention further includes a back layer having an impedance for improving the bandwidth of each frequency component, The depth of the valleys can be further reduced and the bandwidth of each frequency component can be improved.

Fig. 15 shows a therapeutic ultrasound transducer 260 of a three-stage polarization inverse layer structure according to an embodiment of the present invention.

That is, FIG. 15 shows a therapeutic ultrasound transducer 260 having a polarization inverse layer structure laminated in three layers by additionally laminating one piezoelectric element in the therapeutic ultrasound transducer 180 of the polarization inverse layer structure of FIG. 1 (b) .

15, a therapeutic ultrasound transducer 260 having a three-stage polarization inversion layer structure is constructed in the same manner as the features of the therapeutic ultrasound transducer 180 having a polarization reversed-layer structure laminated in two stages, The electrodes 120 and 130 are formed on the surfaces of the piezoelectric elements that are stacked and have only a pair of electrodes 120 and 130. The electrodes 120 and 130 have different polarization directions 160,

In addition, the ultrasonic transducer 260 for therapeutic use having the three-stage polarization inversion layer structure according to an embodiment of the present invention may be configured such that when two piezoelectric elements are laminated It is possible to generate only a wide variety of multi-frequency characteristics or harmonic frequency characteristics.

FIG. 16 shows the pressure at the focusing point through adjustment of the thickness ratio of each of the piezoelectric elements in the structure of the therapeutic ultrasound transducer 260 having the three-stage polarization inversion layer structure, FIG. 17 shows the pressure in the ultrasound transducer (260) shows the result of converting the pressure amplitude at the focal point into a relative frequency spectrum by controlling the thickness ratio of each piezoelectric element in the structure.

16 (a), (b), (c) and 17 (a), (b) and (c) show the thickness ratio of the ultrasonic transducer 260 of the three- As a result obtained by dividing into the branches (case1, case2, case3), the total thickness of the transducer 260 was assumed to be 1.7 mm as in the case of the above-described two-layer laminate structure (FIG. 7 (a) The thicknesses of t ₁ , t ₂ and t ₃ were 0.15 (case ₁ ) and 0.15 (thickness), respectively, when the thicknesses of the laminated piezoelectric elements were equal to each other at a ratio of 0.33 (t ₁ : 0.566 mm, t ₂ : 0.566 mm, t ₃ : 0.566 mm) , T ₂ , and t ₃ are 0.15, 0.7, and 0.15 in thickness ratio (case ₁ ), 0.425, and 0.425 (t ₁ : 0.255 mm, t ₂ : 0.7225 mm, t ₃ : 0.7225 mm) (case ₁ ), and the case where the torsion angle (t ₁ : 0.255 mm, t ₂ : 1.19 mm, t ₃ : 0.255 mm) is present (case ₃ ).

Table 16 below shows the maximum pressure values at the focusing points of each case measured in FIG.

Referring to FIGS. 16, 17 and 16, in case 1, the maximum pressure derived from the focusing point of the therapeutic ultrasound transducer 260 having the three-stage polarization inversion layer structure is about 0.540 MPa, As a result of the conversion into the frequency spectrum, it is confirmed that frequency characteristics of 3f ₀ , which is three times of the total thickness 1f ₀ , are generated.

In case 2, the maximum pressure at the focusing point of the therapeutic ultrasound transducer 260 in the three-pole polarization inversion layer structure is 0.483 MPa, the 1f ₀ characteristic is excluded from the frequency spectrum, and the 2f ₀ and 3f ₀ characteristics are similar to each other Values are generated at the same time.

In case 3, the maximum pressure at the focal point is 0.414 MPa, and the 2f ₀ characteristic is excluded from the frequency spectrum and the 1f ₀ and 3f ₀ characteristics are simultaneously generated at similar values.

In other words, the therapeutic ultrasound transducer 260 having the three-stage polarization inverse layer structure according to an embodiment of the present invention can generate only the 3f ₀ characteristic based on the total thickness by controlling the thickness ratio in the three piezoelectric device lamination structures and it can also be the generation of 1f _0, 2f _0, 3f ₀ multi-frequency characteristics as shown in 2 (b), and various multi-frequency characteristics, such as the addition 2f ₀ and 3f ₀ or, 1f ₀ and 2f ₀ of the attribute Can be generated.

Based on these results, it is possible to select various frequencies in comparison with the conventional single frequency or multi-layer structure by adjusting the number of piezoelectric elements to be laminated and the thickness ratio of each piezoelectric element.

That is, the number of piezoelectric elements stacked in the therapeutic ultrasound transducer 180 of the polarization inversion layer structure is increased, and the frequency characteristics of the transducer, which can be derived through adjustment of the thickness ratio of each piezoelectric element, case 3, and it is possible to derive various single frequency characteristics or multiple frequency characteristics according to the ratio of the number of piezoelectric elements to be laminated and the thickness ratio.

For example, in the therapeutic ultrasound transducer 180 having a polarization inversion layer structure, the first piezoelectric element 140 and the second piezoelectric element 150 are laminated in multiple layers so that the piezoelectric structures reversed polarization are alternately formed, The total lamination thickness of the laminated piezoelectric elements is made equal to the thickness ratio of the laminated piezoelectric elements while maintaining the same thickness of the single piezoelectric element having the same fundamental frequency characteristic, Only the harmonic frequency component of the frequency component may be generated. Here, the harmonic frequency component can be increased in proportion to the number of piezoelectric elements stacked in multiple layers.

18 is a diagram illustrating a prototype of the transducer 180 of the polarization inversion layer structure of the two-layer laminated structure, which is designed using finite element analysis-based simulation.

That is, it is designed to also the conversion 180 of the polarization inversion layer structure of two-stage stacked structure of 18 prototype is to test for various characteristics of the ultrasonic transducer for the treatment of 1 to 17, the same frequency as the 1f ₀ Properties .

Referring to FIG. 18, the prototype of the transducer 180 of the polarization inversion layer structure of the two-layer laminated structure was designed to have a square type of 17 mm diameter using the PZT4 series APC840 as the piezoelectric element. In addition, it is designed in 1-3 composite structure to enable efficient focusing of ultrasonic energy and smooth curvature formation of piezoelectric element, and it is designed to have 0.51 ceramic volume fraction by forming 0.2 mm width in 0.7 mm pitch. As the piezoelectric element generates a 1-3 composite structure and a thickness vibration mode, the total thickness of the stacked piezoelectric elements is 1.5 mm, t ₁ is 0.45 mm, t ₂ is 1.05 mm. &lt; / RTI &gt;

In addition, the prototype of the transducer 180 of the two-layer stacked structure of the polarization reversed layer structure was designed to have a curvature of 40 mm so that the focusing of the ultrasonic energy would be focused at a point where the F-number is about 2, RTV664 silicon with a relatively low acoustic impedance was applied to allow the device to be fixed with the housing and to generate maximum transmission efficiency. The electrodes 120 and 130 are designed to constitute only one pair of piezoelectric element surfaces stacked as in the transformer 180 structure of FIG. 1 (b).

Using the therapeutic ultrasound transducer 180 of the polarization inversion layer structure designed in FIG. 18, the frequencies of the multi-frequency characteristics proposed in the present invention are applied singly, and the focusing regions changed in the medium, which is the medium, are compared.

The following Table 17 shows the frequency characteristics of 1.2 MHz and 2.4 MHz of the therapeutic ultrasound transducer 180 of the polarization inversion layer structure designed in FIG. 18 and the case of applying 1.2 MHz and 2.4 MHz signals The maximum pressure generated at the focal point for all three cases in which a dual-frequency signal is applied, the -3 dB depth of field (DOF) of the formed focal point, and the maximum pressure at the maximum pressure point of the focal point. 6 dB is a table showing measurement results of lateral beamwidth. In addition, to obtain the same results as HIFU treatment, all of the application signals are 200 V _pp A continuous wave having a voltage was used.

As shown in Table 17, when a 2.4 MHz single signal is applied, a maximum pressure of 1.7 MPa is obtained at the focal point, followed by a maximum pressure of 1.6 MPa when the dual frequency is applied, and 1.2 MHz The maximum pressure of 1.2 MPa was obtained.

The -3 dB DOF was the largest measured at 60.5 mm when the 1.2 MHz signal was applied, 33.9 mm when the double frequency was applied, and 28.8 mm when the 2.4 MHz was applied.

In case of -6 dB side beam width, 1.2 MHz signal was most widely applied, and the 2.4 MHz signal showed the narrowest beam width of 1.9 mm.

In other words, referring to Table 17, the therapeutic ultrasound transducer 180 having the polarization inverse layer structure can apply the frequency corresponding to the characteristic on the basis of the multi-frequency characteristic to control the focusing region generated at the focusing point Can be confirmed.

In other words, since the therapeutic ultrasound transducer 100 having a general single piezoelectric element structure generates only one frequency characteristic, there is a restriction on the frequency selection to be applied, and while this constraint always generates the same focusing region, The therapeutic ultrasound transducer 180 having the polarization inversion layer structure according to the embodiment has an advantage that the focusing region can be adjusted by using one transducer depending on the size and environment of the lesion tissue.

19 shows a prototype manufacturing process of a therapeutic ultrasound transducer 180 having a polarization inversion layer structure according to an embodiment of the present invention.

19, two bulk-type PZT-4 piezoelectric element parts are first prepared (Fig. 19 (a)) in order to fabricate a prototype ultrasound transducer 180 for a polarization inversion layer structure, One of the piezoelectric elements is lapped at a target thickness of 1.05 mm of the non-polarization-reversed piezoelectric element and the other element is wrapped at 0.95 mm thicker than the target thickness of 0.45 mm of the polarization inversion layer piezoelectric element (Fig. 19 (b)).

Here, the reason why the lapping is performed to a thickness greater than the target thickness is to prevent damages of the device support which may be generated at the bottom of the device in the dicing process after the adhesion of the two piezoelectric devices. In addition, the lapping of each piezoelectric element is intended to minimize the error between the bonding surfaces of the piezoelectric elements when the two piezoelectric elements are later bonded by laminating a surface having a negative polarization direction.

After the lapping of each piezoelectric element is completed, smooth electrical conductivity between each piezoelectric element is generated before bonding to maximize the effect due to the polarization reversal layer. In order to maximize the effect of the polarization reversal layer, a chrome / gold) is deposited, and then the positive (+) polarization directions of the two devices having a uniform surface are bonded using an adhesive (FIG. 19 (c)). In this manufacturing method, unlike the case where most of the cases using the conventional polarization inversion layer technology form a polarization inversion layer through temperature control in one LiNbO ₃ single element, a method of forming a polarization inversion layer structure using individual piezoelectric elements , It is possible to manufacture a polarization inversion layer structure using various piezoelectric elements by avoiding the fabrication of the proposed polarization inversion layer structure using only the existing LiNbO ₃ through the corresponding method.

After the two piezoelectric elements are cured, a 1-3 composite structure is formed through a dicing operation, and the width-wise filler is attached (Fig. 19 (d)). After the dicing operation, the polarization inversion layer piezoelectric element having a thickness of 0.95 mm is wrapped to 0.45 mm so as to have the total thickness of the two laminated piezoelectric elements (Fig. 19 (e)), and a signal line is formed on the back surface of the piezoelectric element The electrode is formed by depositing chromium / gold preferentially on the surface of the first electrode (Fig. 19 (f)).

Next, an RTV mold having the same curvature as that of the stainless steel ball and the steel ball is prepared in advance and a piezoelectric element is attached between the ball and the mold. Then, a concave type piezoelectric element is formed at a high temperature for improving the focusing function (g)). The formed concave piezoelectric element is cooled, then placed on a stainless steel ball together with the housing, a signal line is connected to the back of the piezoelectric element, and then RTV664 is poured for the back layer formation When the back layer is cured, a back layer is formed (FIG. 19 (h)).

Next, after the back layer is formed, a stainless steel ball is removed, and chromium / gold is deposited on the front surface of the transformer to form a ground line to form an electrode (Fig. 19 (i)). Finally, SMA After attaching the connector (SubMiniature A connector), the signal line is connected to the connector (FIG. 19 (j)), thereby making it possible to complete the fabrication of the therapeutic ultrasound transducer.

FIG. 20 is a flowchart showing a method of manufacturing a therapeutic ultrasound transducer 180 using a polarization-reversed piezoelectric structure according to an embodiment of the present invention.

20, in order to manufacture the therapeutic ultrasound transducer 180 using the polarization-reversed piezoelectric structure, the polarization direction of the first piezoelectric element and the second piezoelectric element is checked in step S10, and then the lapping is performed .

For example, the first piezoelectric element and the second piezoelectric element may be a bulk type PZT-4 piezoelectric element, and after confirming the polarization direction of each piezoelectric element, Can be performed on the surface having the polarization direction.

In step S20, electrodes are formed on the bonding surfaces of the first piezoelectric element and the second piezoelectric element, and then the positive (+) polarization directions are bonded to each other.

For example, as shown in FIG. 19 (c), after the electrodes are formed on the bonding surface by generating smooth electrical conductivity between the piezoelectric elements before bonding, the amount of each piezoelectric element +) Can be bonded to the polarization direction of the positive (+) direction of the two devices having a uniform surface by using an adhesive after depositing chromium / gold on the polarization surface of the device.

In step S30, a composite structure is formed through a dicing operation, and the cross-sectional filler is attached, and in step S40, the polarization inverse-layer piezoelectric elements are wrapped in the formed composite structure.

For example, the composite structure formed through the dicing operation may be a 1-3 complex structure or the like.

In step S50, an electrode for a signal line is formed on the surface of the polarized reverse-biased piezoelectric elements.

For example, in order to form a signal line on the back surface of the piezoelectric element, chromium / gold may be preferentially deposited on the surface of the piezoelectric element to form an electrode.

In step S60, the piezoelectric elements are formed in a concave shape.

For example, as shown in FIG. 19 (g), in order to improve the focusing function, the piezoelectric elements may be formed to have concave surfaces using an RTV mold and a stainless steel ball. In other words, the piezoelectric elements placed on the RTV mold can be formed to have a concavely shaped surface by pressing the stainless steel ball to improve the focusing function.

In step S70, after the piezoelectric elements are positioned inside the housing, a signal line is connected to the rear surface of the piezoelectric elements, and then a rear surface layer is formed.

For example, as shown in FIG. 19 (h), the rear layer can be formed by placing the piezoelectric elements on the stainless steel ball together with the housing, connecting the signal lines to the rear surface of the piezoelectric elements, and then curing the RTV664.

In step S80, an electrode for a ground line is formed on the front surface of the therapeutic ultrasound transducer.

For example, as shown in (i) of FIG. 19, after the back layer is formed, the stainless steel ball may be removed, and chromium / gold may be deposited on the front surface of the transformer to form a ground line.

In step S90, after the connector is attached to the housing, the signal line is connected to the connector, thereby completing the fabrication of the therapeutic ultrasound transducer 180 using the polarization reversed piezoelectric structure.

Here, the connector referred to in the housing may be a miniature connector or the like.

21 (a) shows a finite element analysis-based design of FIG. 18, a prototype of a therapeutic ultrasound transducer 180 having a polarization inverse layer structure completed according to the manufacturing methods of FIGS. 19 and 20, (b) shows a cross-sectional view of the prototype ultrasound transducer 180 of the completed polarization inverse layer structure.

21 (a) and 21 (b), the prototype is an ultrasonic transducer 180 having a polarization inversion layer structure fabricated using piezoelectric elements stacked in two stages, the rear layer is formed using RTV664, The spacing of tooth width is 0.2 mm and the spacing of ceramic is 0.5 mm.

22 (a) and 22 (b) illustrate an electric impedance and an impulse (impulse) to the prototype of the ultrasonic transducer 180 of the polarization inverse layer structure for the performance verification of the prototype of the ultrasonic transducer 180 of the polarization inversion layer structure of FIG. ) 2-way pulse echo response.

Table 18 below is a table showing the resonance and anti-resonance frequencies of the respective frequencies measured at (a) in FIG. 22 and corresponding impedances of the respective frequencies.

Referring to FIG. 22 (a), it can be seen that the 1f ₀ and 2f ₀ characteristics are generated simultaneously according to the ratio of the thickness of 0.3. That is, referring to Table 18, the resonance frequency of about 1.2 MHz in the case of the 1f ₀ characteristic and the resonance frequency in the case of the 2f ₀ characteristic are about 2.3 MHz, ₀ &lt; / RTI &gt; and 2f < ₀ >

22 (b), the center frequencies of the 1f ₀ and 2f ₀ components are measured at 1.2 MHz and 2.4 MHz, respectively, and the 1f ₀ characteristic has the highest peak point, and the 2f ₀ characteristic has the 1f ₀ characteristic Compared with a decrease of -3.83 dB.

The result of FIG. 22 (b) is slightly different from the characteristic of the ratio of 0.3 thickness shown in FIG. 4 (b), but FIG. 4 shows the result of the pressure immediately after returning through the reflector at the focusing point On the other hand, FIG. 22 (b) shows the voltage value according to the 2-way pulse echo response. Therefore, considering the high frequency attenuation during the return time from the reflector, It can be seen that the multi-frequency characteristic using the polarization inversion layer structure proposed in the present invention is experimentally apparent through the transformer prototype of FIG.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

100: ultrasonic transducer for treatment of a single piezoelectric element structure
110: polarization direction of a single piezoelectric element
120: electrode layer
130: ground layer
140: first piezoelectric element
150: second piezoelectric element
160: polarization direction of the first piezoelectric element
170: polarization direction of the second piezoelectric element
180: Therapeutic ultrasound transducer of polarization inverse layer structure
190: Complex structure Piezoelectric layer width
200: Composite structure Ceramic part of piezoelectric layer
210: a second piezoelectric element having a composite structure
220: Polarization direction of the second piezoelectric element having a composite structure
230: Therapeutic ultrasound transducer of a polarization reversed layer structure comprising a complex structure
240: third piezoelectric element
250: polarization direction of the third piezoelectric element
260: Therapeutic ultrasound transducer with 3-pole polarization inversion structure

Claims (12)

In a therapeutic ultrasound transducer using a polarization reversed piezoelectric structure,
A first piezoelectric element;
A second piezoelectric element;
An electrode layer; And
Comprising a ground layer,
Wherein the first piezoelectric element and the second piezoelectric element are laminated so as to have polarization directions opposite to each other,
The first piezoelectric element has a thickness smaller than that of the second piezoelectric element and is located on the opposite side of the ultrasonic wave propagating direction,
Wherein the electrode layer and the ground layer form only a pair of electrodes on the surface of the element in which the first piezoelectric element and the second piezoelectric element are stacked to generate ultrasonic waves having multiple frequency characteristics,
Electrodes can be formed on and adhered to the bonding surfaces of the first and second piezoelectric elements to increase the electrical conductivity, thereby generating efficient multi-frequency characteristics,
Wherein a thickness and an acoustic impedance value of each of the first piezoelectric element and the second piezoelectric element are determined so as to simultaneously generate a harmonic frequency corresponding to an integral multiple of the fundamental frequency and the fundamental frequency, Therapeutic ultrasound transducers.
delete The method according to claim 1,
Wherein the first piezoelectric element and the second piezoelectric element adjust the energy amplitude between multiple frequencies generated simultaneously through the thickness and acoustical impedance ratio control of the piezoelectric transducer.
The method according to claim 1,
Mutual the polarization reversal number of the stacked piezoelectric device is capable of more than a total of three, and the fundamental frequency in accordance with the thickness and acoustic impedance control of the stack each of the piezoelectric element component (1f ₀₎ and the harmonic component corresponding to an integral multiple of the fundamental frequency (2f ₀ , 3f ₀ ), and a polarization reversed piezoelectric structure capable of generating multiple frequencies simultaneously by combining the generated fundamental frequency component and a plurality of harmonic components.
delete The method according to claim 1,
Wherein the first piezoelectric element and the second piezoelectric element can use the same piezoelectric element or different types of piezoelectric elements can be used as the first piezoelectric element and the second piezoelectric element.
The method according to claim 1,
Further comprising a matching layer for improving the transmission efficiency of the therapeutic ultrasound transducer,
The center frequency used in designing the matching layer is determined as an intermediate value of the multiple frequencies to improve the transmission efficiency and the polarization reversed piezoelectric structure that minimizes the deformation of the frequency characteristic generated in the frequency spectrum due to the matching layer Ultrasonic transducer for therapeutic use.
The method according to claim 1,
A therapeutic ultrasound transducer using a polarization reversed piezoelectric structure further comprising a back layer having various impedances to further reduce the depth of bone generated between multiple frequencies in the frequency spectrum and to improve the bandwidth of each frequency component.
The method according to claim 1,
At least one of the piezoelectric elements forms a composite structure, and it is possible to control the acoustic impedance of the piezoelectric element and to simultaneously generate multiple frequencies by controlling the characteristics of the composite component, and to increase the ultrasonic transmission efficiency by controlling the acoustic impedance And increasing the ease of fabricating the transducer. &Lt; Desc / Clms Page number 20 &gt;
delete The method according to claim 1,
Wherein the first piezoelectric element and the second piezoelectric element are made of a piezoelectric material,
Ultrasonic transducer for therapy using a polarization reversed piezoelectric structure formed of a composite structure to form a curvature for ultrasound energy focusing.
A method of making a therapeutic ultrasound transducer using a polarization reversed piezoelectric structure,
After confirming the polarization direction of the first piezoelectric element and the second piezoelectric element, then lapping;
Forming an electrode on the bonding surface of the first piezoelectric element and the second piezoelectric element, and bonding the positive polarity directions to each other;
Wrapping the polarization reversed-phase piezoelectric elements;
Forming an electrode for a signal line on a surface of the polarization inversion layer piezoelectric element;
Forming the piezoelectric elements in a concave shape;
Positioning the piezoelectric elements inside the housing, connecting the signal lines to the rear surface of the piezoelectric elements, and forming a rear surface layer;
Forming an electrode for a ground line on the front surface of the therapeutic ultrasound transducer; And
Attaching a connector to the housing, and connecting the signal line to the connector,
Wherein the first piezoelectric element is thinner than the second piezoelectric element and is located on the opposite side of the ultrasonic wave propagating direction,
The layer on which the electrode is formed and the layer for grounding may be formed by forming only a pair of electrodes on the surface of the element on which the first piezoelectric element and the second piezoelectric element are stacked to generate ultrasonic waves having multi-
Electrodes can be formed on and adhered to the bonding surfaces of the first and second piezoelectric elements to increase the electrical conductivity, thereby generating efficient multi-frequency characteristics,
The thickness and acoustical impedance value of each of the first piezoelectric element and the second piezoelectric element are determined so as to be capable of simultaneously generating a fundamental frequency and a harmonic frequency corresponding to an integral multiple of the fundamental frequency,
In order to form the therapeutic ultrasound transducer into a composite structure, it is preferable that the step of adhering the polarization directions to each other is followed by a step of forming a composite structure through a dicing operation, Method of making ultrasonic transducer.

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