JP7415785B2 - Ultrasonic probe and ultrasonic diagnostic equipment - Google Patents

Description

The present invention relates to an ultrasound probe and an ultrasound diagnostic apparatus.

Ultrasonic diagnostic equipment can be used to probe inside a subject by simply applying an ultrasound probe connected to the ultrasound diagnostic equipment to the body surface of a subject, including humans or animals, or inserting it into the subject. This makes it possible to obtain ultrasonic diagnostic images of the tissue and movement of the body. Ultrasonic diagnostic equipment has the advantage of being highly safe and allowing repeated examinations.

Ultrasonic probes have built-in piezoelectric elements that transmit and receive ultrasonic waves. The piezoelectric element converts the transmitted signal from the ultrasound diagnostic device into an ultrasound signal and transmits it, receives the ultrasound reflected inside the subject and converts it into an electrical signal, and receives the ultrasound signal converted into an electrical signal. Send the signal to an ultrasound diagnostic device.

FIG. 14 is a perspective view of a conventional ultrasound probe 40. As shown in FIG. 14, a conventional ultrasonic probe 40 connected to a conventional ultrasonic diagnostic apparatus is acoustically matched to a piezoelectric element 41 having a plano-concave surface in the short axis direction (Y-axis direction) indicated by the arrow in the figure. A layer 46 is provided, and is composed of a piezoelectric element 41 and an acoustic matching layer 46, a large number of piezoelectric elements 41 and acoustic matching layers 46 are arranged in a direction perpendicular to the short axis direction, and a backing 44 is provided on the back surface of the piezoelectric element 41. It is provided. The thickness of the piezoelectric element 41 in the short axis direction is thinner at the center and thicker toward the ends. The acoustic matching layer 46 also has a similar thickness configuration.

With this configuration, high-frequency ultrasonic waves are obtained at the center of the piezoelectric element 41 and the acoustic matching layer 46, and low-frequency ultrasonic waves are obtained toward the ends. This makes it possible to obtain frequency characteristics in a high frequency range. Furthermore, the aperture becomes smaller at the center in the short axis direction at high frequencies, and the aperture becomes larger as you move toward the ends, that is, shift to lower frequencies, so the beam diameter is narrow from short distances to long distances. can be obtained, and high resolution can be achieved (for example, see Patent Document 1).

Furthermore, by providing a configuration in which a reflective layer is provided between the piezoelectric element and the backing, it is possible to widen the frequency band and improve sensitivity performance. By providing a reflective layer on the back side of the piezoelectric element with a thickness that is larger than the acoustic impedance of the piezoelectric element and approximately 1/4 wavelength, it becomes possible to efficiently radiate ultrasound toward the subject. In addition, there is a known configuration in which the thickness of the reflective part in the short axis direction is made thinner at the center and thicker toward the ends, thereby achieving a wider band (for example, as disclosed in the patent (See Reference 2).

Japanese Unexamined Patent Publication No. 7-107595 Special table 2017-501808 publication

There is a high demand for high resolution in ultrasound diagnostic equipment, and the ultrasound probes connected to ultrasound diagnostic equipment must have a wide frequency band, high sensitivity, and short axis. It is important to improve performance such as narrowing down the ultrasonic beam from short distances to long distances.

In order to meet the demand for higher resolution, there is currently a method to narrow down the ultrasonic beam in the short axis direction of the ultrasonic probe by using an acoustic lens, etc. The focus is fine near the focal length, but the beam spreads out at distances before and after the focal length, reducing resolution. On the other hand, as in the piezoelectric element having the configuration of Patent Document 1 or the reflective part having the configuration of Patent Document 2, one side of the piezoelectric element is processed to have a concave surface, and the concave piezoelectric parts or reflective parts are bonded to each other to form a laminated structure. There are issues with the need for precision processing and bonding technology.

The purpose of the present invention is to widen the frequency band of ultrasonic waves from high frequencies to low frequencies with a simple configuration without using a piezoelectric part or a reflecting part with a plano-concave structure, and to transmit ultrasonic waves from short distances with a deep depth of focus. An object of the present invention is to provide an ultrasonic probe and an ultrasonic diagnostic device that achieve high resolution over long distances.

In order to solve the above problem, the ultrasonic probe of the invention according to claim 1 has the following features:
a piezoelectric section in which a plurality of piezoelectric elements that transmit and receive ultrasonic waves are arranged;
a backing part provided on the back side of the piezoelectric part;
a reflecting section disposed between the piezoelectric section and the backing section and having an acoustic impedance greater than an acoustic impedance of the piezoelectric section;
an intermediate part disposed between the piezoelectric part and the reflective part,
The intermediate portion has a frequency of ultrasonic waves at a center portion of the piezoelectric portion in a direction orthogonal to an arrangement direction of the plurality of piezoelectric elements higher than a frequency of ultrasonic waves at the end portions ,
The intermediate portion has an acoustic impedance value that is equal to or lower than the acoustic impedance of the reflecting portion, and has an acoustic impedance value that is continuous, stepwise, regular, or irregular in the direction from the center portion to the end portion of the piezoelectric portion. Regularly reduce acoustic impedance,
The intermediate portion is a composite of a first material having an acoustic impedance value equal to or lower than the acoustic impedance of the reflecting portion and a second material having an acoustic impedance smaller than the first material. , the volume ratio of the first material is large at the center of the piezoelectric part, and the volume ratio of the first material becomes smaller toward the ends .
The ultrasonic probe of the invention according to claim 2 includes:
a piezoelectric section in which a plurality of piezoelectric elements that transmit and receive ultrasonic waves are arranged;
a backing part provided on the back side of the piezoelectric part;
a reflecting section disposed between the piezoelectric section and the backing section and having an acoustic impedance greater than an acoustic impedance of the piezoelectric section;
an intermediate part disposed between the piezoelectric part and the reflective part,
The intermediate portion is a composite using a plurality of materials having different acoustic impedances, and the value of the acoustic impedance of the composite at the center of the piezoelectric portion in a direction perpendicular to the arrangement direction of the plurality of piezoelectric elements is determined at the end. is made larger than the value of the acoustic impedance of the composite body, and the frequency of the ultrasonic waves at the center is made higher than the frequency of the ultrasonic waves at the ends.

The invention according to claim 3 is the ultrasonic probe according to claim 2 ,
The intermediate portion has an acoustic impedance value that is equal to or lower than the acoustic impedance of the reflecting portion, and has an acoustic impedance value that is continuous, stepwise, regular, or irregular in the direction from the center portion to the end portion of the piezoelectric portion. Regularly reduce acoustic impedance.

The invention according to claim 4 is the ultrasonic probe according to claim 1 or 3,
The intermediate portion has at least a uniform thickness, or has a thickness that increases continuously or stepwise from the center to the end of the piezoelectric portion.

The ultrasonic probe of the invention according to claim 5 includes:
a piezoelectric section in which a plurality of piezoelectric elements that transmit and receive ultrasonic waves are arranged;
a backing part provided on the back side of the piezoelectric part;
a reflecting section disposed between the piezoelectric section and the backing section and having an acoustic impedance greater than an acoustic impedance of the piezoelectric section;
an intermediate part disposed between the piezoelectric part and the reflective part,
The intermediate portion has a frequency of ultrasonic waves at a center portion of the piezoelectric portion in a direction orthogonal to an arrangement direction of the plurality of piezoelectric elements higher than a frequency of ultrasonic waves at the end portions,
The intermediate portion has a value smaller than the value of the acoustic impedance of the reflecting portion, and has a thickness increasing in a direction from the center portion to the end portion of the piezoelectric portion,
The thickness of the intermediate portion may be increased continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric portion by tilting at least the piezoelectric portion or the reflective portion. ,
A plurality of grooves are provided in the piezoelectric part, the reflective part, or both,
The depth of the groove is shallow at the center and becomes deeper toward the ends.

The ultrasonic probe of the invention according to claim 6 includes:
a piezoelectric section in which a plurality of piezoelectric elements that transmit and receive ultrasonic waves are arranged;
a backing part provided on the back side of the piezoelectric part;
a reflecting section disposed between the piezoelectric section and the backing section and having an acoustic impedance greater than an acoustic impedance of the piezoelectric section;
an intermediate part disposed between the piezoelectric part and the reflective part,
The intermediate portion has a frequency of ultrasonic waves at a center portion of the piezoelectric portion in a direction orthogonal to an arrangement direction of the plurality of piezoelectric elements higher than a frequency of ultrasonic waves at the end portions,
The intermediate portion has a value smaller than the value of the acoustic impedance of the reflecting portion, and has a thickness increasing in a direction from the center portion to the end portion of the piezoelectric portion,
The thickness of the intermediate portion may be increased continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric portion by tilting at least the piezoelectric portion or the reflective portion. ,
The thickness of the intermediate portion is such that at least the piezoelectric portion or the reflective portion has variations in unevenness or surface roughness, and is continuous, stepwise, or regular in the direction from the center to the end of the piezoelectric portion. or irregularly thickened.

The invention according to claim 7 is the ultrasonic probe according to any one of claims 1 to 6 ,
The acoustic impedance of the piezoelectric part, the reflecting part, or both changes continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric part.
The ultrasonic probe of the invention according to claim 8 includes:
a piezoelectric section in which a plurality of piezoelectric elements that transmit and receive ultrasonic waves are arranged;
a backing part provided on the back side of the piezoelectric part;
a reflecting section disposed between the piezoelectric section and the backing section and having an acoustic impedance greater than an acoustic impedance of the piezoelectric section;
an intermediate part disposed between the piezoelectric part and the reflective part,
The intermediate portion has a frequency of ultrasonic waves at a center portion of the piezoelectric portion in a direction orthogonal to an arrangement direction of the plurality of piezoelectric elements higher than a frequency of ultrasonic waves at the end portions,
The acoustic impedance of the piezoelectric part, the reflecting part, or both changes continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric part.
The ultrasonic probe of the invention according to claim 9 is the ultrasonic probe according to any one of claims 1 to 8, comprising:
The intermediate portion lowers the frequency of the ultrasonic wave from the center toward the end.

The invention according to claim 10 is the ultrasonic probe according to any one of claims 1 to 9 ,
The intermediate portion changes the frequency of the ultrasonic wave from a high frequency to a low frequency continuously, stepwise, regularly or irregularly from the center to the end of the piezoelectric portion.

The invention according to claim 11 is the ultrasonic probe according to any one of claims 1 to 10 ,
One or more acoustic matching layers are provided in the direction from the piezoelectric part to the subject,
The acoustic matching layer has a uniform thickness.

The ultrasonic diagnostic apparatus of the invention according to claim 12 includes:
The ultrasonic probe according to any one of claims 1 to 11 ;
and an image generation unit that generates ultrasound image data based on a received signal input from the ultrasound probe.

According to the present invention, a frequency band can be widened with a simple configuration, and high resolution can be achieved from short distances to long distances.

1 is an external view of an ultrasonic diagnostic apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram showing the functional configuration of an ultrasonic diagnostic apparatus. FIG. 1 is a partial cross-sectional view of the ultrasound probe of the first embodiment. FIG. 3 is a diagram schematically showing the relationship between the width of a piezoelectric part and the acoustic impedance of an intermediate layer. FIG. 3 is a diagram showing frequency characteristics when the acoustic impedance of the intermediate layer of the ultrasound probe of the first embodiment is changed. FIG. 6 is a diagram showing the relationship between center frequencies when the acoustic impedance of the intermediate layer of the ultrasound probe of the first embodiment is changed. FIG. 7 is a diagram showing frequency characteristics when changing the thickness of the intermediate layer of the ultrasound probe according to the second embodiment. FIG. 7 is a diagram showing the relationship between center frequencies when changing the thickness of the intermediate layer of the ultrasound probe according to the second embodiment. (a) is a cross-sectional view showing an example of a piezoelectric part, a reflective layer, and an intermediate layer. (b) is a sectional view showing another example of a piezoelectric part, a reflective layer, and an intermediate layer. (c) is a sectional view showing yet another example of a piezoelectric part, a reflective layer, and an intermediate layer. (a) is a diagram showing the relationship between the thicknesses of the piezoelectric part and the intermediate layer of the ultrasound probe according to the second embodiment. (b) is a diagram showing frequency characteristics received by the hydrophone. (a) is a diagram showing the results of beam patterns measured with the ultrasound probe of the second embodiment. (b) is a diagram showing the results of a beam pattern of a comparative example. FIG. 7 is a diagram showing frequency characteristics when the sound speed of the intermediate layer of the ultrasound probe of the third embodiment is changed. FIG. 7 is a diagram showing the relationship between center frequencies when changing the sound speed of the intermediate layer of the ultrasonic probe according to the third embodiment. FIG. 2 is a perspective view of a conventional ultrasound probe.

First to third embodiments of the present invention will be described in detail in order with reference to the accompanying drawings. Note that the present invention is not limited to the illustrated example.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. 1 to 6. First, with reference to FIG. 1, the overall configuration of an ultrasound diagnostic apparatus 100 according to the present embodiment will be described. FIG. 1 is a schematic diagram showing an ultrasound diagnostic apparatus 100 according to the present embodiment.

As shown in FIG. 1, the ultrasound diagnostic apparatus 100 includes an ultrasound probe 10, a main body 11, and a connector 12. The ultrasonic probe 10 is connected to the main body part 11 via a cable 14 connected to a connector part 12. A transmission signal (drive signal) from the main body section 11 is transmitted to the piezoelectric section 1 (see FIG. 2) of the ultrasound probe 10 via the cable 14. This transmission signal is converted into an ultrasonic wave in the piezoelectric section 1, and is transmitted into the living body of the subject. The transmitted ultrasonic wave is reflected by the tissue in the living body of the subject, and the reflected wave is also received by the piezoelectric section 1 and converted into a reception signal as an electric signal, which is transmitted to the main body section 11. The received signal is converted into ultrasound image data, which is an image of the internal state within the subject, in the main body 11 and displayed on the display 13.

The ultrasonic probe 10 includes a piezoelectric section 1, and the piezoelectric section 1 includes, for example, a plurality of piezoelectric elements 1a as transducers arranged in a one-dimensional array in the azimuth direction (scanning direction). . In this embodiment, for example, an ultrasound probe 10 including 192 piezoelectric elements 1a is used. Note that the piezoelectric section 1 may have piezoelectric elements 1a arranged in a two-dimensional array. Further, the number of piezoelectric elements 1a of the piezoelectric section 1 can be set arbitrarily. Furthermore, in this embodiment, ultrasonic scanning is performed using a linear scanning method using electronic scanning probes arranged in a linear manner as the ultrasound probe 10; however, the linear scanning method, the convex scanning method, Alternatively, either sector scanning method may be adopted. Communication between the main body 11 and the ultrasound probe 10 may be performed by wireless communication such as UWB (Ultra Wide Band) instead of wired communication via the cable 14.

Next, with reference to FIG. 2, the functional configuration of the ultrasound diagnostic apparatus 100 will be described. FIG. 2 is a block diagram showing the functional configuration of the ultrasound diagnostic apparatus 100.

As shown in FIG. 2, the main body 11 includes, for example, an operation input section 15, a transmission section 16, a reception section 17, an image generation section 18, an image processing section 19, and a DSC (Digital Scan Converter) 20. , a display section 13, and a control section 21.

The operation input unit 15 receives operation inputs from an operator such as a doctor or a laboratory technician. The operation input unit 15 includes various switches for inputting various image parameters for displaying, for example, a command to start diagnosis, data such as personal information of a subject, ultrasound image data, etc. on the display unit 13, and the like. , buttons, trackball, mouse, keyboard, etc., and outputs operation signals to the control unit 21. Note that the main body section 11 may include a touch panel provided on the display panel of the display section 13 to receive touch input from the operator.

The transmitter 16 is a circuit that supplies a drive signal, which is an electric signal, to the ultrasound probe 10 via the cable 14 under the control of the controller 21 to cause the ultrasound probe 10 to generate a transmission ultrasound. . Further, the transmitter 16 includes, for example, a clock generation circuit, a delay circuit, and a pulse generation circuit. The clock generation circuit is a circuit that generates a clock signal that determines the transmission timing and transmission frequency of the drive signal. The delay circuit sets a delay time for each individual path corresponding to each piezoelectric element 1a, delays the transmission of the drive signal by the set delay time, and focuses the transmission beam formed by the transmission ultrasound. It is a circuit. The pulse generation circuit is a circuit for generating a pulse signal as a drive signal at a predetermined period. The transmitting unit 16 configured as described above, for example, transmits a continuous portion (for example, 48 ) to generate transmitting ultrasonic waves. Then, the transmitter 16 performs scanning by shifting the piezoelectric element 1a, which is driven, in the azimuth direction (scanning direction) every time the transmitted ultrasonic wave is generated.

The receiving unit 17 is a circuit that receives a reception signal, which is an electrical signal, from the ultrasound probe 10 via the cable 14 under the control of the control unit 21 . The receiving unit 17 includes, for example, an amplifier, an A/D conversion circuit, and a phasing and adding circuit. The amplifier is a circuit for amplifying the received signal by a preset amplification factor for each individual path corresponding to each piezoelectric element 1a. The A/D conversion circuit is a circuit for analog-to-digital conversion (A/D conversion) of the amplified received signal. The phasing and adding circuit adjusts the time phase by giving a delay time to each individual path corresponding to each piezoelectric element 1a to the A/D-converted received signal, and adds these (phasing and addition) to generate sound. This is a circuit for generating line data.

The image generation unit 18 performs envelope detection processing, logarithmic compression, etc. on the sound ray data from the reception unit 17 under the control of the control unit 21, adjusts the dynamic range and gain, and converts the brightness. , B (Brightness) mode image data consisting of pixels having a brightness value as received energy can be generated. That is, the B-mode image data represents the strength of the received signal using luminance. The image generation unit 18 generates B-mode image data as ultrasound image data whose image mode is B mode, as well as A (Amplitude) mode, M (Motion) mode, Doppler method image mode (color Doppler mode, etc.), etc. It may also be possible to generate ultrasound image data in other image modes.

The image processing section 19 performs image processing on the B-mode image data output from the image generation section 18 according to various image parameters being set under the control of the control section 21 . Further, the image processing section 19 includes an image memory section 19a configured of a semiconductor memory such as a DRAM (Dynamic Random Access Memory). The image processing section 19 stores the B-mode image data subjected to image processing in the image memory section 19a in units of frames under the control of the control section 21. Image data in frame units is sometimes referred to as ultrasound image data or frame image data. The image processing section 19 sequentially outputs the image data generated as described above to the DSC 20 under the control of the control section 21 .

The DSC 20 converts the image data received from the image processing section 19 into an image signal for display under the control of the control section 21 and outputs it to the display section 13 .

The display unit 13 can be a display device such as an LCD (Liquid Crystal Display), a CRT (Cathode-Ray Tube) display, an organic EL (Electronic Luminescence) display, an inorganic EL display, or a plasma display. The display unit 13 displays still images or moving images of ultrasound image data on the display screen according to the image signal output from the DSC 20 under the control of the control unit 21 .

The control unit 21 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and reads out various processing programs such as a system program stored in the ROM and expands them into the RAM. , controls the operation of each part of the ultrasonic diagnostic apparatus 100 according to the developed program. The ROM is composed of a non-volatile memory such as a semiconductor, and stores a system program corresponding to the ultrasound diagnostic apparatus 100, various processing programs executable on the system program, and various data such as a gamma table. These programs are stored in the form of computer-readable program codes, and the CPU sequentially executes operations according to the program codes. The RAM forms a work area that temporarily stores various programs executed by the CPU and data related to these programs.

Regarding each unit included in the ultrasound diagnostic apparatus 100, part or all of the functions of each functional block can be realized as a hardware circuit such as an integrated circuit. An integrated circuit is, for example, an LSI (Large Scale Integration), and an LSI is sometimes called an IC (Integrated Circuit), a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. In addition, the method of integrating circuits is not limited to LSIs, but may be realized using dedicated circuits or general-purpose processors, and the connections and settings of circuit cells inside FPGAs (Field Programmable Gate Arrays) and LSIs can be reconfigured. A reconfigurable processor may also be used. Further, part or all of the functions of each functional block may be executed by software. In this case, this software is stored in one or more storage media such as ROM, optical disk, or hard disk, and is executed by a processor.

Next, an example of the overall structure of the ultrasound probe 10 will be described with reference to FIGS. 3 to 6. FIG. 3 is a partial cross-sectional view of the ultrasound probe 10. FIG. 4 is a diagram schematically showing the relationship between the width of the piezoelectric section 1 (in the Y-axis direction) and the acoustic impedance of the intermediate layer 9. FIG. 5 is a diagram showing frequency characteristics when the acoustic impedance of the intermediate layer 9 of the ultrasound probe 10 of this embodiment is changed. FIG. 6 is a diagram showing the relationship between the center frequency fc when the acoustic impedance of the intermediate layer 9 of the ultrasound probe 10 of this embodiment is changed.

As shown in FIG. 3, the ultrasonic probe 10 includes a piezoelectric section 1, a ground electrode 2 arranged on the front side for applying voltage to the piezoelectric section 1, and a signal electrode 3 arranged on the back side. , a reflective layer 5 as a reflective part disposed on the back side of the signal electrode 3, an intermediate layer 9 as an intermediate part disposed between the piezoelectric part 1 and the reflective layer 5, a signal electric terminal 7, and a piezoelectric It has an acoustic matching layer 6 as an acoustic matching layer and an acoustic lens 8 arranged in this order from the section 1 to the front side, and a backing 4 as a backing section arranged from the signal electrical terminal 7 to the back side. In this embodiment, the signal electrode 3, intermediate layer 9, and reflective layer 5 provided in the piezoelectric section 1 are arranged in contact with each other. Further, as shown in FIG. 3, it is assumed that the X-axis, Y-axis, and Z-axis are taken.

The piezoelectric section 1 is formed by a plurality of piezoelectric elements 1a that are arranged one-dimensionally in the X-axis direction in FIG. 3 to transmit ultrasonic waves by applying a voltage. The thickness of the piezoelectric portion 1 can be, for example, 0.05 [mm] or more and 0.3 [mm] or less. Each piezoelectric body is made of piezoelectric ceramics such as lead zirconate titanate (PZT), lead magnesium niobate/lead titanate solid solution (PMN-PT), and lead zinc niobate/lead titanate solid solution (PZN-PT). ) and other piezoelectric single crystals, as well as composite piezoelectric bodies made of composites of these materials and polymeric materials.

The ground electrode 2 is an electrode in which gold, silver, or the like is disposed on the front surface of the piezoelectric section 1 by a method such as vapor deposition, sputtering, or silver baking. The signal electrode 3 is an electrode in which gold, silver, or the like is placed on the back surface of the piezoelectric section 1 by a method such as vapor deposition, sputtering, or silver baking. The reflective layer 5 is a layer placed on the back side of the intermediate layer 9 placed on the back side of the signal electrode 3 provided on the piezoelectric section 1 . Since the reflective layer 5 is made of a material having a value larger than the acoustic impedance of the piezoelectric section 1, the piezoelectric section 1 is made to vibrate at a quarter wavelength of the ultrasonic wave transmitted and received by the piezoelectric section 1. It is composed of The signal electrical terminal 7 is disposed in contact with the back side of the reflective layer 5, and connects the signal electrode 3 to the main body 11 of the ultrasonic diagnostic apparatus 100 via the reflective layer 5 or the intermediate layer 9 and reflective layer 5. It is connected to an external power source (transmission section 16), etc. located at the terminal.

The intermediate layer 9 is a layer provided between the piezoelectric section 1 and the reflective layer 5, and as shown in FIG. The acoustic impedance is large in the center of the direction (direction), and the acoustic impedance decreases toward the ends. In addition, in FIG. 4, the horizontal axis schematically shows the width of the piezoelectric section 1 in the Y-axis direction shown in FIG. 3, and the vertical axis schematically shows the value of the acoustic impedance of the intermediate layer 9.

The acoustic matching layer 6 is a layer for acoustically matching the piezoelectric section 1 and the acoustic lens 8, and is made of a material having an acoustic impedance approximately intermediate between that of the piezoelectric section 1 and the acoustic lens 8. In this embodiment, the acoustic matching layer 6 includes four layers: a first acoustic matching layer 6a, a second acoustic matching layer 6b, a third acoustic matching layer 6c, and a fourth acoustic matching layer 6d. Here, each of the first acoustic matching layer 6a, the second acoustic matching layer 6b, the third acoustic matching layer 6c, and the fourth acoustic matching layer 6d has a substantially uniform thickness.

In this embodiment, the first acoustic matching layer 6a is made of silicon, quartz, free-cutting ceramics, graphite filled with metal powder, and has an acoustic impedance of 8 [MRayls] or more and 20 [MRayls] or less. and materials such as epoxy resin filled with fillers such as metals or oxides. The second acoustic matching layer 6b is formed from an epoxy resin filled with filler such as graphite and metal or oxide, and has an acoustic impedance of 6 [MRayls] or more and 12 [MRayls] or less. The third acoustic matching layer 6c is formed from a material such as an epoxy resin filled with a filler such as a metal or an oxide, and has an acoustic impedance of 3 [MRayls] or more and 6 [MRayls] or less. The fourth acoustic matching layer 6d is formed of a plastic material mixed with a rubber material, a resin filled with silicone rubber powder, etc., with a thickness of 1.7 [MRayls] or more and 2.3 [MRayls] or less.

By multilayering the acoustic matching layer 6 in this way, the ultrasound probe 10 can have a wider band. In addition, when the acoustic matching layer 6 is multilayered, it is more preferable that the acoustic impedance of each layer is set so that the acoustic impedance of each layer gradually or continuously approaches the acoustic impedance of the acoustic lens 8 as it approaches the acoustic lens 8. Further, each layer of the multilayered acoustic matching layer 6 may be adhered with an adhesive commonly used in the technical field, such as an epoxy adhesive.

Note that the material of the acoustic matching layer 6 is not limited to the above materials, and known materials including aluminum, aluminum alloy, magnesium alloy, Macor glass, glass, fused silica, copper graphite, resin, etc. can be used. It is. Examples of the above resins include polyethylene, polypropylene, polycarbonate, ABS (Acrylonitrile Butadiene Styrene) resin, AAS (Acrylonitrile Acrylate Styrene) resin, AES (Acrylonitrile Ethylene Styrene) resin, nylon, polyphenylene oxide, polyphenylene sulfide, polyphenylene ether, polyether. Includes ether ketone, polyamideimide, polyethylene terephthalate, epoxy resin, urethane resin, etc.

The acoustic lens 8 is made of, for example, a soft polymeric material that has an acoustic impedance close to that of the living body of the subject and a sound velocity different from that of the living body, and is refracted due to the difference in sound speed between the living body and the acoustic lens 8. is used to focus the ultrasonic waves transmitted from the piezoelectric section 1 to improve resolution. In this embodiment, the acoustic lens 8 is a cylindrical type that extends along the Y-axis direction in FIG. 3 (a direction perpendicular to the X-axis direction in which the piezoelectric elements 1a are arranged) and is convex in the Z-axis direction. This is an acoustic lens, which focuses the ultrasonic waves in the Y-axis direction and emits them toward the subject side of the ultrasonic probe 10. Examples of the above-mentioned soft polymeric materials include silicone rubber and the like.

The reflective layer 5 is a layer disposed between the piezoelectric part 1 (signal electrode 3), the intermediate layer 9, and the signal electrical terminal 7, and is used to widen and increase the frequency range that can be used by the ultrasound probe 10. It has a sensitizing function. The reflective layer 5 is made of a material having a higher acoustic impedance than the piezoelectric part 1.

The backing 4 is a layer that holds the piezoelectric section 1 and the reflective layer 5 and attenuates the ultrasonic waves transmitted from the piezoelectric section 1 to the back side via the reflective layer 5. The backing 4 is typically made of synthetic rubber, natural rubber, epoxy resin, thermoplastic resin, etc. filled with materials to adjust acoustic impedance, damping, and heat dissipation.

The ultrasonic probe 10 mechanically rotates, oscillates, or slides an ultrasonic wave transmitting/receiving section having a piezoelectric section 1 of a single piezoelectric element 1a that transmits and receives ultrasonic waves, or a plurality of piezoelectric elements 1a are arranged in an array. A window (not shown), which is a protective member for obtaining a three-dimensional ultrasound image by mechanically rotating or swinging the ultrasound transmitter/receiver part that can electronically scan the piezoelectric parts 1 arranged in the It may be provided at a position that covers the side of the probe 10 that comes into contact with the subject. The ultrasonic probe 10 also includes an acoustic medium liquid (not shown) between the window and the acoustic lens 8 etc. for acoustically matching the window and the wave transmitting/receiving surface of the piezoelectric section 1. You can.

The reflective layer 5 will be explained below. The thickness of the piezoelectric section 1 is set to about 0.25 wavelength (ultrasonic wavelength λ), which is thinner than a conventional piezoelectric section using general 0.5 wavelength resonance. Since the electric field strength generated in the piezoelectric part 1 when a voltage is applied is inversely proportional to the thickness of the piezoelectric part 1, the piezoelectric part 1 in this embodiment has a larger internal electric field strength than a conventional piezoelectric part. This causes a large amount of distortion. The thickness of the piezoelectric part 1 in this embodiment is about 1/2 of the thickness of a conventional general 0.5 wavelength resonance type piezoelectric part, so the strain in the piezoelectric part 1 is about twice that of the conventional piezoelectric part. Become.

However, when the piezoelectric part 1 is vibrated in a near-free state where no load is applied to both end faces on which the ground electrode 2 and signal electrode 3 are provided, the 0.5 wavelength resonance in the thickness direction is strongly excited, and the transmission and reception frequency increases. In order to make this a 0.25 wavelength resonance, a reflective layer 5 having a larger acoustic impedance than the piezoelectric part 1 is provided. This makes it possible to suppress vibrations on the back side of the piezoelectric section 1 and generate large strain while suppressing an increase in the transmission and reception frequency. In this state, acoustic energy is not distributed much to the reflective layer 5 side, and as a result, the ultrasonic probe 10 can have high transmission efficiency. Further, since the piezoelectric portion 1 is thin, the electrical capacity is increased, and an ultrasonic probe having high sensitivity and a wide band can be constructed.

As the material for the reflective layer 5, any material such as tungsten or tantalum that has a large difference in acoustic impedance from the piezoelectric part 1 can be used, but tungsten carbide is preferable from the viewpoint of manufacturing. Alternatively, it may be made of a mixture of tungsten carbide and other materials.

Note that since the material of the reflective layer 5 is electrically conductive, the signal electrode 3 of the piezoelectric section 1 and the signal electrical terminal 7 can be electrically connected, but the reflective layer 5 is electrically conductive. In the case of an insulator or a semiconductor, the piezoelectric part 1 can be formed by providing a through hole around or in the reflective layer 5 and providing a conductor of copper or gold by a method such as plating, vapor deposition, or sputtering. The signal electrode 3 and the signal electric terminal 7 may be electrically connected.

On the other hand, the acoustic lens 8 is a cylindrical acoustic lens that extends along the Y-axis direction in the figure (a direction perpendicular to the X-axis direction in which the piezoelectric elements 1a are arranged) and is convex in the Z-axis direction. The ultrasonic waves are focused in the Y-axis direction and radiated toward the subject. This acoustic lens 8 uses the difference in sound speed between the acoustic lens 8 and the subject to focus the light to a desired depth. Near the focused depth, the ultrasonic beam is narrowed down and an image with high resolution can be obtained, but on the other hand, there is a problem in that the resolution deteriorates due to diffusion at short and long distances before and after the focus. For this reason, it is important to focus the ultrasonic beam narrowly over short and long distances in order to improve resolution. The present embodiment is characterized by the configuration described above, which makes it possible to focus the ultrasonic beam narrowly to a deep distance from a short distance to a long distance.

The feature of this embodiment is that an intermediate layer 9 is provided between the piezoelectric section 1 and the reflective layer 5. FIG. 4 is a schematic diagram showing three patterns in which the acoustic impedance of the intermediate layer 9 is varied in the Y-axis direction (the width of the piezoelectric portion 1) of the piezoelectric portion 1 shown in FIG. The acoustic impedance of the intermediate layer 9 at the center in the Y-axis direction of the piezoelectric section 1 is high, and decreases toward the ends. As a result, the center of the piezoelectric section 1 in the Y-axis direction has a frequency characteristic that has a high frequency range, but as it approaches the ends, it has a frequency characteristic that shifts to a low frequency range. By weighting the frequencies in the axial direction, the ultrasonic beam is focused from short distances to long distances.

FIG. 5 shows that when the thickness of the intermediate layer 9 is fixed (in FIG. 5, the thickness of the intermediate layer 9 is 0.05 wavelength) and the value of the acoustic impedance of the intermediate layer 9 is changed from 4 to 100 [MRayls], the horizontal It shows a change in the frequency characteristic of the sensitivity [dB] of the ultrasonic probe 10 on the vertical axis with respect to the frequency [MHz] on the axis. From FIG. 5, it can be confirmed that the frequency characteristics change as the acoustic impedance of the intermediate layer 9 changes. When the intermediate layer 9 has a large acoustic impedance, it has a frequency characteristic up to a high frequency, and as the acoustic impedance of the intermediate layer 9 becomes smaller, it has a frequency characteristic that shifts to a lower frequency. From this result, as shown in FIG. 4, by providing an intermediate layer 9 with a large acoustic impedance at the center of the piezoelectric section 1 in the Y-axis direction and decreasing the acoustic impedance toward the ends, it is possible to reduce the frequency. Weighting becomes possible. In other words, the same phenomenon can be realized by varying the thickness of the piezoelectric section 1 and the reflective layer 5 and changing the frequency as in Patent Document 1 and Patent Document 2.

In addition, FIG. 5 uses the acoustic impedance values of each configuration shown in the following Table I, and assumes that the center frequency fc of the ultrasound is 10 [MHz] in the ultrasonic probe 10 with the configuration illustrated in FIG. 3. These are the results obtained by simulating the pulse response characteristics of the ultrasonic waves transmitted and received from the piezoelectric section 1 using the KLM (Krimholtz, Leedom and Matthaei) method. The wavelength of the ultrasonic wave is the value obtained by dividing the sound speed by the working frequency of 10 [MHz].

Moreover, FIG. 6 shows the change in the center frequency fc at -6 dB calculated from the frequency characteristic of the acoustic impedance of the intermediate layer 9 in FIG. The axis indicates the center frequency fc [MHz].

Here, the relationship between the center frequency fc and the acoustic impedance of the intermediate layer 9 is shown when the thickness of the intermediate layer 9 is 0.025 wavelength (ultrasonic wavelength λ), 0.05 wavelength, and 0.075 wavelength. ing. As is clear from the results in FIG. 6, increasing the acoustic impedance of the intermediate layer 9 tends to increase the center frequency fc, and conversely, decreasing the acoustic impedance tends to decrease the center frequency fc. Even if the thickness of the intermediate layer 9 changes, the same tendency is observed, although the degree of change is different.

Also, from FIG. 6, when the acoustic impedance of the intermediate layer 9 increases to 30 [MRayls] or more, the change in the center frequency fc becomes small, and even if it increases beyond that, it tends to be saturated, but the acoustic impedance of the reflective layer 5 Since the acoustic impedance of the intermediate layer 9 provided at the center of the piezoelectric part 1 in the Y-axis direction is approximately equal to or lower than that of the reflective layer 5, it changes up to a close value (about 100 [MRayls]). effective.

The configuration used in the simulation is based on the assumption that water is the subject in front of the acoustic lens 8 of the ultrasonic probe 10 shown in FIG. The results of the frequency characteristics when Fourier transformed are shown.

In this way, the intermediate layer 9 has a structure in which the acoustic impedance of the intermediate layer 9 is changed, that is, the acoustic impedance value is large at the center in the Y-axis direction of the piezoelectric section 1 and decreases toward the ends. As shown in FIG. 5, the central part of the piezoelectric part 1 in the Y-axis direction has a large acoustic impedance, so ultrasonic waves having a high frequency band can be transmitted and received. Since the acoustic impedance of the intermediate layer 9 is reduced, high frequency components are cut and ultrasonic waves having low frequency components can be transmitted and received. In the ultrasonic probe 10 having such a configuration, the transmitting section 16 shown in FIG. 2 applies a drive signal that generates a broadband transmission signal to the piezoelectric section 1.

As shown in FIGS. 3 to 6, the piezoelectric section 1 has an intermediate layer 9 provided between the piezoelectric section 1 and the reflective layer 5, which has a large acoustic impedance at the center of the piezoelectric section 1 in the Y-axis direction. The structure is such that the acoustic impedance gradually and continuously changes to a smaller value toward the end. Therefore, as shown in FIGS. 5 and 6, the piezoelectric section 1 includes many high frequencies in the sound wave emission direction on the subject side at the center of the piezoelectric section 1 in the Y-axis direction, that is, the center frequency fc is high; Since it becomes lower toward the end, it has a broadband frequency characteristic.

In addition, the intermediate layer 9 is not provided in the central region of the piezoelectric portion 1 in the Y-axis direction, and the reflective layer 5 is provided so as to be in direct contact with it, and the intermediate layer 9 is provided from an arbitrary region toward the end. The acoustic impedance may also be made to slope as it goes from part to part.

Note that the intermediate layer 9 provided between the piezoelectric part 1 and the reflective layer 5 has a large acoustic impedance in the center of the piezoelectric part 1, and has a continuous acoustic impedance that increases toward the ends. Although the configuration has been described in which the acoustic impedance is changed to a small value, the intermediate layer 9 provided between the piezoelectric part 1 and the reflective layer 5 may change the acoustic impedance in a stepwise, regular or irregular manner. It has a similar effect.

If the acoustic impedance is to be reduced stepwise from the center to the end in the Y-axis direction of the piezoelectric section 1, a structure may be adopted in which materials each having an acoustic impedance are arranged.

Further, the thickness of the acoustic matching layer 6 may be changed in accordance with the change in the center frequency fc from the center in the Y-axis direction of the piezoelectric part 1 in the direction of the ends.

The acoustic lens 8 focuses the ultrasonic waves propagated through the acoustic matching layer 6 from the piezoelectric section 1 on a subject (not shown). After being transmitted by the piezoelectric section 1 and passing through the acoustic lens 8, the high frequency component of the ultrasonic wave at a short distance is localized near the center of the piezoelectric section 1 in the Y-axis direction. The component ultrasonic beam diameter becomes narrower. On the other hand, the low frequency component, which shifts to a lower frequency from the center to the end in the Y-axis direction of the piezoelectric part 1, has an ultrasonic beam diameter that increases at a short distance, but at a relatively long distance. The ultrasonic beam diameter tends to become narrower due to the focusing of the lens 8. Therefore, due to the focusing effect of the acoustic lens 8 and the effect of changing the frequency from the center region in the Y-axis direction of the piezoelectric section 1 to a high frequency and shifting to a low frequency toward the ends, Since the ultrasonic beam can be focused narrowly over a distance, the resolution of the ultrasonic image can be improved.

An example of a method for changing the acoustic impedance of the intermediate layer 9 provided between the piezoelectric section 1 and the reflective layer 5 is as follows. Materials with high acoustic impedance having arbitrary thickness, such as tungsten metal film (acoustic impedance is about 104 [MRayls]), molybdenum metal film (acoustic impedance is about 63 [MRayls]), copper film (acoustic impedance is about 44 [MRayls]) ]), stainless steel metal film (acoustic impedance is approximately 46 [MRayls]), etc., or a film processed into a film shape with an acoustic impedance of 30 [MRayls] or more, and etching these materials using a pattern mask. Stripes or holes are provided by laser processing or mechanical processing. A material having an acoustic impedance of 30 [MRayls] or less, for example, an adhesive such as an epoxy resin, is provided in the striped or holed portions of the film. This makes it possible to change the value of acoustic impedance by changing the volume ratio of the film of 30 [MRayls] or more and the material of 30 [MRayls] or less provided in the holes. In addition, any material other than metal with an acoustic impedance of 30 [MRayls] or more may be used, and the material is not limited to these materials.

Note that since the material of the intermediate layer 9 is various metal films and is electrically conductive, the signal electrode 3 of the piezoelectric portion 1 and the signal electrical terminal 7 via the intermediate layer 9 and the reflective layer 5 are However, if the intermediate layer 9 is made of an electrical insulator or semiconductor, a plurality of through holes are provided around or in the intermediate layer 9 to connect the copper. The signal electrode 3 of the piezoelectric part 1 is electrically connected to the signal electric terminal 7 via the intermediate layer 9 and the reflective layer 5 by providing a gold conductor by a method such as plating, vapor deposition, or sputtering. Good too.

Here, as an example of a method for changing the acoustic impedance of the intermediate layer 9, a composite using a plurality of types of materials will be described below. When considering a composite of tungsten metal film and epoxy resin, the acoustic impedance of each is approximately 104 [MRayls] for tungsten and approximately 3 [MRayls] for epoxy resin, and these composites change the volume ratio. Accordingly, the acoustic impedance can be arbitrarily changed in the range of about 3 to about 104 [MRayls], and the frequency characteristics can be arbitrarily changed as shown in FIGS. 5 and 6. The area where the volume ratio of tungsten is high, that is, the area where the acoustic impedance is large, is provided at the center of the piezoelectric part 1 in the Y-axis direction, and the volume ratio of the epoxy resin is increased toward the ends, thereby reducing the acoustic impedance. Place it in For example, tungsten with a thickness of 0.025 wavelength (at a frequency of 10 [MHz], the speed of sound is about 6460 [m/s], so the thickness is 0.0136 [mm]) can be etched, laser processed, etc. Using the method described above, a layer in which pores are provided so that the porosity increases toward the end of the piezoelectric section 1 in the Y-axis direction is provided between the piezoelectric section 1 and the reflective layer 5, and epoxy adhesive is applied thereto. By adhering with an agent or the like, the adhesive can also enter the voids and be adhered to form the intermediate layer 9 of the composite.

In addition, after processing the tungsten film to form holes in advance, the holes are filled with epoxy resin and processed to a desired thickness, and then the piezoelectric part 1 and the reflective layer 5 are bonded with epoxy resin. It is also possible to provide the

In the characteristics shown in FIGS. 5 and 6, the thickness of the intermediate layer 9 is uniform, but this thickness is thinner at the center in the Y-axis direction of the piezoelectric section 1, and becomes thicker toward the ends. , or the thickness may be inclined stepwise or the thickness may be reversed.

Further, although the acoustic matching layer 6 of this embodiment is described as having a substantially uniform thickness, the high frequency characteristics of the center of the piezoelectric portion 1 in the Y-axis direction may be In some cases, the thickness may be changed in accordance with each frequency as the frequency shifts to lower frequencies toward the end.

The intermediate layer 9 provided between the piezoelectric part 1 and the reflective layer 5 has a structure in which the acoustic impedance is large at the center of the piezoelectric part 1 in the Y-axis direction and becomes smaller toward the ends. In addition, as shown in FIG. 4, there is also a configuration in which the acoustic impedance is constant in a certain width at the center of the piezoelectric section 1 in the Y-axis direction, and changes from there so that the acoustic impedance decreases toward the ends. A similar effect can be obtained.

Note that the acoustic impedance of the piezoelectric part 1 and the reflective layer 5 has a constant value in the Y-axis direction, and the intermediate layer 9 provided between the piezoelectric part 1 and the reflective layer 5 has a constant value in the Y-axis direction of the piezoelectric part 1. In the above description, the acoustic impedance is large at the center of the piezoelectric section 1, and the acoustic impedance becomes smaller toward the ends. A similar effect can be obtained in a configuration in which the acoustic impedance is decreased continuously, stepwise, regularly, or irregularly.

In addition, although the acoustic impedance of the piezoelectric part 1 or the reflective layer 5 has been described as having a uniform value from the center to the end of the piezoelectric part 1 in the Y-axis direction, in addition to this, the acoustic impedance of the piezoelectric part 1 or the reflective layer 5 is The same effect can also be obtained in a configuration in which the acoustic impedance is changed continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric part 1 in the Y-axis direction. .

As described above, according to the present embodiment, the ultrasonic probe 10 includes a piezoelectric section 1 in which a plurality of piezoelectric elements 1a that transmit and receive ultrasonic waves are arranged, and a backing 4 provided on the back side of the piezoelectric section 1. , a reflective layer 5 disposed between the piezoelectric part 1 and the backing 4 and having an acoustic impedance larger than the acoustic impedance of the piezoelectric part 1; an intermediate layer 9 disposed between the piezoelectric part 1 and the reflective layer 5; Equipped with The intermediate layer 9 makes the frequency of the ultrasonic waves at the center of the piezoelectric section 1 in the Y-axis direction orthogonal to the arrangement direction (X-axis direction) of the plurality of piezoelectric elements 1a higher than the frequency of the ultrasonic waves at the ends. Specifically, the intermediate layer 9 lowers the frequency of the ultrasonic waves from the center toward the ends in the Y-axis direction.

With this configuration, the piezoelectric element and reflective layer do not need to be processed into curved surfaces as in the past, making the configuration simple and easy to manufacture, as well as providing high-quality ultrasonic probes. 10 children can be obtained.

Furthermore, a high frequency response is obtained at the center of the piezoelectric section 1 in the Y-axis direction, and shifts from high frequency to low frequency toward the ends. In addition, by changing the size of the aperture in inverse proportion to the frequency, it is possible to obtain a narrow ultrasonic beam diameter from a short distance with a deep depth of focus to a long distance, and the ultrasonic probe 10, The ultrasonic diagnostic apparatus 100 can have high resolution.

Further, the intermediate layer 9 has an acoustic impedance value that is equal to or lower than the acoustic impedance of the reflective layer 5, and is continuously, stepwise, or Reduce acoustic impedance regularly or irregularly. Therefore, by changing the acoustic impedance, the frequency (of the ultrasonic waves) can be easily changed to a small value from the center of the piezoelectric section 1 in the Y-axis direction toward the ends.

Further, the intermediate layer 9 has a uniform thickness from the center to the end of the piezoelectric section 1 in the Y-axis direction. Therefore, the configuration of the ultrasonic probe 10 can be simplified and can be easily produced.

Further, the intermediate layer 9 is a composite of a first material having an acoustic impedance value equal to or less than the acoustic impedance of the reflective layer 5 and a second material having an acoustic impedance smaller than the first material. The volume ratio of the first material is large at the center of the piezoelectric part 1 in the Y-axis direction, and the volume ratio of the first material becomes smaller toward the ends. Therefore, the frequency (of the ultrasonic waves) can be easily and reliably changed to a small value from the center of the piezoelectric section 1 in the Y-axis direction toward the ends.

Further, the intermediate layer 9 changes the frequency of the ultrasonic waves from a high frequency to a low frequency continuously, stepwise, regularly or irregularly from the center to the end in the Y-axis direction of the piezoelectric part 1. do. Therefore, the frequency can be easily and reliably changed to a small value from the center to the end of the piezoelectric section 1 in the Y-axis direction by using various aspects of the intermediate layer 9.

The ultrasonic probe 10 also includes one or more (four layers) of a first acoustic matching layer 6a, a second acoustic matching layer 6b, and a third acoustic matching layer 6c in the direction from the piezoelectric part 1 toward the subject. , a fourth acoustic matching layer 6d is provided. The first acoustic matching layer 6a, the second acoustic matching layer 6b, the third acoustic matching layer 6c, and the fourth acoustic matching layer 6d have uniform thicknesses. Therefore, the ultrasonic probe 10 can have a wide band, and the configuration of the acoustic matching layer 6 can be simplified.

The ultrasound diagnostic apparatus 100 also includes an ultrasound probe 10 and an image generation unit 18 that generates ultrasound image data based on a received signal input from the ultrasound probe 10. Therefore, with a simple configuration, it is possible to widen the frequency band and realize the ultrasonic diagnostic apparatus 100 with high resolution from short distances to long distances.

(Second embodiment)
A second embodiment according to the present invention will be described with reference to FIGS. 7 to 11. Note that this embodiment is basically the same as the configuration shown in FIG. 3 described in the first embodiment, so it will be described with reference to FIG. 3. FIG. 7 is a diagram showing frequency characteristics when the thickness of the intermediate layer 9 of the ultrasound probe 10 of this embodiment is changed. FIG. 8 is a diagram showing the relationship between the center frequency fc when the thickness of the intermediate layer 9 of the ultrasound probe 10 of this embodiment is changed.

In FIG. 7, a material having a value of 3 [MRayls] smaller than the acoustic impedance of the piezoelectric part 1 and the reflective layer 5 is used for the intermediate layer 9 provided between the piezoelectric part 1 and the reflective layer 5, and its thickness is The calculation results of frequency characteristics when changing . FIG. 7 shows the results of the sensitivity [dB] of the ultrasound probe 10 on the vertical axis versus the frequency [MHz] on the horizontal axis when the thickness of the intermediate layer 9 is changed from 0 to 0.02 wavelength. Note that the calculations show the results obtained by varying the thickness of the intermediate layer 9 using the method shown in the first embodiment and the specifications in Table I.

Further, FIG. 8 shows the relationship between the thickness of the intermediate layer 9 corresponding to FIG. 7 on the horizontal axis and the center frequency fc [MHz] at −6 dB calculated based on the results of FIG. 7 on the vertical axis. FIG. 8 also shows the results when the acoustic impedance of the intermediate layer 9 was set to 10 and 30 [MRayls].

As shown in FIG. 7, when the thickness of the intermediate layer 9 is thin, that is, it is extremely thin with a thickness of 0 or 0.004 wavelength in the figure, it has broadband characteristics with frequencies up to the high frequency range, but As the thickness of the layer 9 increases (from 0.006 wavelength to 0.02 wavelength), the frequency characteristic is such that the high frequency range is cut and shifted to the low frequency range. FIG. 8, which shows the results of calculating the center frequency fc from the frequency characteristics of FIG. 7, also shows a tendency to shift to a lower frequency range as the thickness of the intermediate layer 9 increases. This is because, as shown in FIG. 8, the frequency tends to shift even if the acoustic impedance of the intermediate layer 9 becomes 10 or 30 [MRayls]. However, in the intermediate layer 9 of 30 [MRayls], which has a large acoustic impedance, the change in thickness and frequency tends to be small, but there is still an effect. In the configuration in which the frequency is varied by varying the thickness of the intermediate layer 9, it is effective if the acoustic impedance of the intermediate layer 9 has a smaller value than the acoustic impedance of the reflective layer 5.

As can be assumed from FIG. 8, the acoustic impedance of the intermediate layer 9 is smaller than that of the piezoelectric section 1 and the reflective layer 5, that is, the ratio becomes larger, so that the center frequency fc with respect to the thickness of the intermediate layer 9 increases. Changes tend to be large. An example of a specific material for effectively utilizing this tendency is an epoxy resin having an acoustic impedance of approximately 3 [MRayls]. Furthermore, if a material with an acoustic impedance value smaller than this is used, the frequency characteristics can be greatly changed with a small change in thickness. Examples of materials other than epoxy resin include composites of epoxy resin filled with various powders, metals, metal oxides, or metal carbides, polymer materials, low melting point indium, tin metal, and other alloys. be. The material for the intermediate layer 9 is not limited to any material as long as it has a value smaller than the acoustic impedance of the reflective layer 5.

In addition, although the acoustic impedance of the piezoelectric part 1 or the reflective layer 5 has been described as having a uniform value from the center to the end of the piezoelectric part 1 in the Y-axis direction, in addition to this, the acoustic impedance of the piezoelectric part 1 or the reflective layer 5 is The same effect can also be obtained in a configuration in which the acoustic impedance is changed continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric part 1 in the Y-axis direction. .

Taking advantage of the fact that the frequency characteristics change when the thickness of the intermediate layer 9 in FIGS. By increasing the thickness toward the ends, a high-frequency response can be obtained in the center region of the piezoelectric section 1, and as it approaches the ends, the frequency shifts from high to low, and the piezoelectric section At the end of 1, it is possible to obtain a lower frequency response than at the center, and the aperture size is changed in inverse proportion to the frequency, allowing narrow ultrasonic waves to be transmitted from short distances with deep focal depths to long distances. Since the beam diameter can be obtained, high resolution can be achieved.

An example of a structure in which the thickness of the intermediate layer 9 provided between the piezoelectric part 1 and the reflective layer 5 is varied is shown in FIGS. 9(a), 9(b), and 9(c). FIG. 9A is a cross-sectional view showing an example of the piezoelectric section 1, the reflective layer 5, and the intermediate layer 9. FIG. 9(b) is a cross-sectional view showing another example of the piezoelectric section 1, the reflective layer 5, and the intermediate layer 9. FIG. 9C is a cross-sectional view showing still another example of the piezoelectric section 1, the reflective layer 5, and the intermediate layer 9.

In the configuration in which the thickness of the intermediate layer 9 shown in FIG. 9(a) is varied, both the piezoelectric portion 1 and the reflective layer 5 are inclined. The thickness of the intermediate layer 9 is the thinnest at the center of the piezoelectric section 1 in the Y-axis direction, and is inclined so that it becomes thicker toward the ends. Note that although the thickness of the intermediate layer 9 is inclined with respect to the thickness of the piezoelectric part 1 and the reflective layer 5, the thickness of the intermediate layer 9 is also inclined even if the piezoelectric part 1 or the reflective layer 5 is not inclined. The structure is not limited to this as long as the thickness is inclined.

Further, in the configuration in which the thickness of the intermediate layer 9 shown in FIG. 9(b) is changed, a plurality of grooves extending in the X-axis direction are provided in the piezoelectric part 1, and the depth of the grooves (depth of the unevenness) is It is shallow in the center in the axial direction and becomes deeper toward the ends. In addition, a plurality of grooves are provided in the reflective layer 5 or the piezoelectric part 1 and the reflective layer 5, and the depth of the grooves (the depth of the unevenness) is shallow at the center in the Y-axis direction and gradually increases toward the ends. It may be configured to be deeper. Alternatively, the piezoelectric portion 1, the reflective layer 5, or both may have a configuration in which the surface roughness is varied. In other words, the depth or surface roughness of the unevenness at the center of the piezoelectric part 1 in the Y-axis direction is small, and becomes deeper or rougher toward the ends, and the intermediate part provided between the piezoelectric part 1 and the reflective layer 5 is By embedding or adhering the layer 9 according to the depth of the unevenness and the surface roughness, the layer 9 is formed continuously or stepwise from the center to the end of the piezoelectric part 1 in the Y-axis direction, with the thickness varying. The structure is such that it is thick.

Furthermore, in the configuration in which the thickness of the intermediate layer 9 shown in FIG. 9 has a structure in which the thickness of the piezoelectric part 1 is thin at the center in the Y-axis direction and becomes thicker toward the ends. In addition, the thickness of the piezoelectric part 1 or the reflective layer 5 is changed stepwise in a regular or irregular manner, and the intermediate layer 9 is thinner at the center in the Y-axis direction of the piezoelectric part 1 and closer to the ends. Therefore, it may be configured to be thicker .

With the above configuration, a high frequency response can be obtained at the center of the piezoelectric section 1 in the Y-axis direction, and the response shifts from high frequency to low frequency toward the ends, and the piezoelectric At the end of section 1, a lower frequency response can be obtained than at the center, and the aperture size is changed in inverse proportion to the frequency to provide a narrow ultra-low focus range from near to far with a deep depth of focus. Since the beam diameter of the sound waves can be obtained, high resolution can be achieved.

FIG. 10A is a diagram showing the relationship between the thicknesses of the piezoelectric portion 1 and the intermediate layer 9 of the ultrasound probe 10 of this embodiment. FIG. 10(b) is a diagram showing the frequency characteristics of the ultrasound probe 10 received by the hydrophone. FIG. 11A is a diagram showing the results of the beam pattern measured with the ultrasound probe 10 of this embodiment. FIG. 11(b) is a diagram showing the results of the beam pattern of the comparative example. 10(a) to FIG. 11(b), an ultrasonic probe 10 is prototyped, and the frequency changes from a high frequency to a low frequency range from the center to the end in the Y-axis direction of the piezoelectric part 1. The figure shows the results of measuring the ultrasonic beam pattern when

The specifications of the prototype ultrasonic probe 10 are the center frequency of 10 [MHz] with the configuration shown in Table I of the first embodiment, and the width of the piezoelectric part 1 (the length in the Y-axis direction in FIG. 3). The radius of curvature of the acoustic lens was set to 4.6 mm, and the focal length of the acoustic lens was approximately 20 mm. For the intermediate layer 9 provided between the piezoelectric section 1 and the reflective layer 5, an epoxy resin having an acoustic impedance of about 3 [MRayls] was used.

In FIG. 10(a), the horizontal axis shows the width [mm] of the piezoelectric part 1 in the Y-axis direction (minor axis), and the vertical axis shows the thickness [mm] of the intermediate layer 9 made of epoxy resin. In the region approximately 1.1 [mm] on both sides from the center in the Y-axis direction, the thickness of the intermediate layer 9 is 0.5 [μm], which is close to 0 (0.002 wavelength when the center frequency fc is 10 [MHz]). The thickness of the intermediate layer 9 was made as follows (equivalent to 10 [MHz]), and the thickness of the intermediate layer 9 was increased from there toward both ends, to 6 [μm] at the ends (corresponding to 0.024 wavelength when the center frequency fc is 10 [MHz]). . This configuration is similar to that shown in FIG. 9A, but in order to make the thickness of the intermediate layer 9 incline, the reflective layer 5 is processed to make it incline, and the piezoelectric part 1 has a uniform thickness.

In FIG. 10(b), an ultrasonic probe 10 made by making the thickness of the intermediate layer 9 slope is placed at each position A, B, C, D, and E shown in FIG. 10(a). The vertical axis corresponds to the frequency [Hz] on the horizontal axis when the received waveform is measured by installing a hydrophone that receives ultrasonic waves transmitted with an impulse drive waveform having characteristics that include the frequency band of the child 10 at a close distance. The results of each frequency characteristic of the sensitivity [dB] of the ultrasonic probe 10 are shown below. It can be seen that the frequency characteristics change from a high frequency range to a low frequency range as the thickness of the intermediate layer 9 changes. In FIG. 10(b), the center frequency fc of each frequency characteristic is 10.8 [MHz] at position A, 10.3 [MHz] at position B, 9.3 [MHz] at position C, and 8 at position D. .0 [MHz], and 6.8 [MHz] at position E. The center frequency fc at the center of the piezoelectric part 1 in the Y-axis direction has a high frequency range, and as it goes to the ends, it becomes low. The result is a shift in the frequency range, and by changing the thickness of the intermediate layer 9 depending on the position of the piezoelectric portion 1, the frequency changes.

FIG. 11(a) shows the results of measuring the ultrasonic beam with respect to depth using the ultrasonic probe 10 whose frequency characteristics change from the center to the end in the Y-axis direction of the piezoelectric part 1. ). In FIG. 11, the horizontal axis shows the measurement depth [mm], and the vertical axis shows the beam widths [mm] of −3 dB, −6 dB, and −12 dB in the beam profile at each depth. The measurement conditions at this time are that the ultrasonic probe 10 is installed at the center of rotation of the hydrophone, and the hydrophone is scanned at each depth in steps of 0.2 degrees underwater to measure the waveform. is being received and measured.

FIG. 11(b) is a comparative example of an ultrasonic probe, in which the width of the piezoelectric part is 4.6 [mm], and the intermediate layer has a uniform thickness of 0.5 [μm] or less, which is close to 0. These are the results of ultrasound beam patterns measured using an ultrasound probe with a so-called conventional configuration, in which there is no change in frequency characteristics from the center to the ends in the axial direction. Further, FIG. 11(a) shows the results of the ultrasonic beam pattern measured using the ultrasonic probe 10 having the configuration changed to the frequency characteristics shown in FIGS. 10(a) and 10(b) of this embodiment. be.

From the ultrasonic beam pattern in Figure 11(b) of the comparative example (conventional configuration), the distance where the beam width is narrowest at the -3 dB, -6 dB, and -12 dB levels, that is, the focal length, is 20 [mm]. The respective beam widths were 0.61 [mm], 0.97 [mm], and 1.8 [mm]. On the other hand, the distances at which the beam width is narrowest at -3 dB, -6 dB, and -12 dB from the ultrasonic beam pattern of FIG. The beam widths were 0.82 [mm], 1.3 [mm], and 2.2 [mm], respectively. The beam width at the focal length is narrower in the comparative example (conventional configuration) than in this embodiment, but it is true that the comparative example has higher resolution around this depth; As is clear from the comparison in terms of depth and overall depth, the configuration of this embodiment has a beam that is uniformly narrow over the entire area, and the resolution of the ultrasound image is high in the depth of a wide area. A method for evaluating the beam width will be explained below.

Additionally, depth of focus is a method for evaluating whether an ultrasound beam is focused over a wide depth region. This is a method of evaluating the beam width at the focal length by determining how many times the beam width is. Using this method, the results of FIGS. 11(a) and 11(b) will be evaluated. This time, we evaluated the distance and range before and after the beam width becomes 1.5 times the narrowest beam width.

In the results of the ultrasonic probe of the comparative example in Fig. 11(b), -3 dB is from 14 [mm] to 28 [mm], and the range is 14 [mm], and even -6 dB is from 14 [mm] to 28 [mm]. [mm], and the range is 14 [mm]. On the other hand, the result of the ultrasonic probe 10 of FIG. 11(a) having the configuration of this embodiment is that -3 dB is from 11 [mm] to 31 [mm], the range is 20 [mm], and -6 dB Then, the distance is from 11 [mm] to 34 [mm], and the range is 23 [mm]. From these results, the ultrasonic probe 10 of this embodiment has a configuration that is 1.4 to 1.6 times as deep as the configuration of the comparative example, and the ultrasonic beam is focused without spreading. It has been confirmed that the ultrasonic beam is focused over a wide range.

As described above, when comparing FIG. 11(a) and FIG. 11(b), it is clear that the frequency characteristics of the piezoelectric section 1 of this embodiment are changed from the center to the end in the Y-axis direction. In the ultrasonic probe 10 shown in FIG. 11(a), the beam spread is smaller from short distance to long distance in the depth direction, and high-resolution images can be obtained over a wide range.

The intermediate layer 9 provided between the piezoelectric part 1 and the reflective layer 5 has a thin and uniform thickness in about 50% of the center region in the Y-axis direction of the piezoelectric part 1, and thickens from there toward the ends. However, the slope of the thickness of the intermediate layer 9 is not limited to this, and the same effect can be obtained by changing the thickness in any region.

As described above, according to the present embodiment, the intermediate layer 9 has a value smaller than the value of the acoustic impedance of the reflective layer 5, and the thickness increases from the center to the end in the Y-axis direction of the piezoelectric section 1. .

Therefore, by changing the thickness of the intermediate layer 9, the frequency (of the ultrasonic waves) can be easily changed to a small value from the center to the end of the piezoelectric section 1 in the Y-axis direction. A high-frequency response is obtained at the center of the piezoelectric section 1 in the Y-axis direction, and the frequency shifts from high to low toward the ends, and a lower frequency response is obtained at the ends of the piezoelectric section 1 than at the center. In addition, by changing the aperture size in inverse proportion to the frequency, a narrow ultrasonic beam diameter with a deep focal depth from short distances to long distances can be obtained. The sonic diagnostic apparatus 100 can have high resolution.

Further, the thickness of the intermediate layer 9 can be adjusted continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric part 1 in the Y-axis direction by tilting at least the piezoelectric part 1 or the reflective layer 5. Make it thicker. Therefore, the frequency (of the ultrasonic waves) can be easily changed to a small value from the center to the end of the piezoelectric section 1 in the Y-axis direction using various aspects of the intermediate layer 9.

Further, the piezoelectric portion 1, the reflective layer 5, or both are thick at the center in the Y-axis direction of the piezoelectric portion 1 and thin toward the ends. The thickness of the intermediate layer 9 increases at least continuously or stepwise from the center of the piezoelectric section 1 in the Y-axis direction toward the ends. Therefore, it is possible to easily change the frequency (of the ultrasonic waves) to a small value from the center of the piezoelectric part 1 in the Y-axis direction to the end by using various aspects of the piezoelectric part 1, the reflective layer 5, and the intermediate layer 9. I can do it.

Further, a plurality of grooves are provided in the piezoelectric portion 1, the reflective layer 5, or both. The depth of the groove is shallow at the center in the Y-axis direction and becomes deeper toward the ends. Therefore, the frequency (of the ultrasonic waves) can be easily and reliably changed to a small value from the center of the piezoelectric section 1 in the Y-axis direction toward the ends.

Further, the thickness of the intermediate layer 9 is set so that at least the piezoelectric part 1 or the reflective layer 5 has a change in unevenness or surface roughness, and the thickness of the intermediate layer 9 is set continuously or stepwise from the center to the end in the Y-axis direction of the piezoelectric part 1. to thicken in a targeted, regular or irregular manner. The frequency (of the ultrasonic waves) can be easily and reliably changed from the center to the end of the piezoelectric section 1 in the Y-axis direction.

(Third embodiment)
A third embodiment according to the present invention will be described with reference to FIGS. 12 and 13. FIG. 12 is a diagram showing frequency characteristics when the sound speed of the intermediate layer 9 of the ultrasound probe 10 of this embodiment is changed. FIG. 13 is a diagram showing the relationship between the center frequency fc when the sound velocity of the intermediate layer 9 of the ultrasound probe 10 of this embodiment is changed.

In this embodiment, the ultrasonic diagnostic apparatus 100 of the first embodiment is used as the device configuration, but the ultrasonic probe 10 is replaced with the ultrasonic probe 10 shown in FIG. 3. shall be. In the ultrasonic diagnostic apparatus 100, the same components as those in the first and second embodiments are given the same reference numerals, and the description thereof will be omitted.

FIG. 12 shows the results when the thickness of the intermediate layer 9 is set to 0.025 wavelength, the acoustic impedance is set to 6 [MRayls], and the sound velocity value of the intermediate layer 9 is changed in the range of 1000 to 7000 [m/s]. It shows a change in the frequency characteristic of the sensitivity [dB] of the ultrasound probe 10 on the vertical axis with respect to the frequency [MHz] on the horizontal axis.

Further, FIG. 13 shows changes in the center frequency fc and the sound speed at −6 dB calculated from each frequency characteristic in FIG. 12. The horizontal axis shows the sound velocity [m/s] in the intermediate layer 9, and the vertical axis shows the center frequency fc [MHz]. Note that FIGS. 12 and 13 show the results of calculations using the method shown in the first embodiment and the specifications in Table I while varying the sound speed in the intermediate layer.

In FIGS. 12 and 13, when the speed of sound in the intermediate layer 9 is high, the frequency characteristic extends to high frequencies, and as the speed of sound in the intermediate layer 9 becomes slow, the frequency characteristic shifts to lower frequencies. ing.

From FIG. 13, the center frequency fc at 1000 [m/s], where the sound speed is slow in the intermediate layer 9, is approximately 8 [MHz], and increases as the sound speed increases, and at 7000 [m/s], where the sound speed is fast. It can be seen that the center frequency fc at ] is about 10 [MHz].

As an example of means for changing the sound velocity of the intermediate layer 9, it is possible to use multiple types of materials with different sound velocities. A configuration in which the sound velocity is reduced in stages from the center of the piezoelectric section 1 in the Y-axis direction toward the ends will be described below.

A material having a sound velocity of 6500 [m/s] or more is provided in the first region located at the center of the piezoelectric portion 1 in the Y-axis direction. Examples include the following materials. Ceramics of oxides, carbides, and nitrides such as alumina having a speed of 10,520 [m/s], silicon carbide having a speed of 13,060 [m/s], and tungsten carbide having a speed of 6,700 [m/s], and ceramics of 8,430 [m/s] such as silicon with A second region located next to the first region is provided with a material having a sound velocity in the range of 4500 to 6500 [m/s]. Examples include the following materials. Metal materials such as titanium with a speed of 6100 [m/s], stainless steel with a speed of around 5700 [m/s], and free-cutting ceramics with a speed of about 5500 [m/s] are available. Next, a material having a sound velocity in the range of 3000 to 4500 [m/s] is provided in the third region located next to the second region. Examples include the following materials. By filling graphite-based materials such as DFP-1C (Poco Graphite, Inc.), which has a speed of 3240 [m/s], and epoxy resin with powder of carbides such as silicon carbide or oxides such as alumina. , composite materials that can achieve the above sound speed. Next, in the fourth region located next to the third region, that is, at the end of the piezoelectric section 1 in the Y-axis direction, a material having a sound velocity in the range of 1000 to 3000 [m/s] is provided. Examples include the following materials. A material such as silicone rubber with a speed of around 1000 [m/s], urethane rubber with a speed of around 2000 [m/s], or epoxy resin with a speed of around 2500 [m/s] is provided.

In this way, in the width direction of the piezoelectric part 1 (the Y-axis direction in FIG. 3), the intervals between the materials with different sound velocities in four stages may be equal or different; By arranging the intermediate layer 9 so that the speed of sound is the highest and becomes slower toward the ends, the frequency can be varied. Note that the thicknesses of the four levels of material of the intermediate layer 9 may be uniform or non-uniform, and the thicknesses are not limited as long as they can be adjusted so that the frequency changes.

Furthermore, in the above description, a configuration has been described in which the sound velocity of the intermediate layer 9 is divided into four stages in the Y-axis direction of the piezoelectric section 1, but the number of divisions is not limited to this. Alternatively, the speed of sound may be continuously variable.

Further, another example of means for changing the sound velocity of the intermediate layer 9 will be described below. The sound speed can be varied by making the intermediate layer 9 a composite of at least two types of materials, one with a high sound speed and one with a slow sound speed, and changing the volume ratio in a plurality of regions in the Y-axis direction. The configuration of the composite given as an example below is an explanation of a case where materials with high sound speed and materials with low sound speed are arranged alternately and their volume ratio is changed, but the configuration of the composite is not limited to this. It's not something you can do.

In the central region of the piezoelectric part 1 in the Y-axis direction, a region with a high sound speed is provided by increasing the volume ratio of a material with a high sound speed as the intermediate layer 9, and as it goes to the end of the piezoelectric part 1, a region with a low sound speed is provided. By gradually increasing the volume ratio of the material, it is possible to provide a region where the speed of sound is low. For example, barium titanate ceramics has a sound speed of 5,450 [m/s] as a material with a high sound speed, and epoxy resin has a sound speed of 2,500 [m/s] as a material with a slow sound speed. When the volume ratio is changed to 75%, 50%, and 25%, the sound speed changes to 4760 [m/s], 4450 [m/s], and 3930 [m/s], respectively. In this way, by changing the volume ratio of materials with different sound speeds, it is possible to vary the sound speed, and the intermediate layer 9 changes the sound speed from the center to the ends of the piezoelectric section 1 in the Y-axis direction. It can be changed continuously or in steps. It was understood that in addition to the materials listed above, the combination of materials with different sound velocities is not limited to these materials.

In this way, the sound speed of the intermediate layer 9 is changed, that is, the sound speed of the intermediate layer 9 is provided at the center of the piezoelectric portion 1 in the Y-axis direction, and the sound speed of the intermediate layer 9 is slow as it goes toward the ends. With such a configuration, it is possible to transmit and receive ultrasonic waves having a frequency characteristic having a high frequency range at the center of the piezoelectric section 1 and a frequency characteristic having a low frequency component toward the ends. Therefore, since it can have the same function as the first and second embodiments, it is possible to obtain a narrow ultrasonic beam diameter from a short distance with a deep depth of focus to a long distance, so that high resolution can be achieved.

The intermediate layer 9 provided between the piezoelectric part 1 and the reflective layer 5 has a uniform thickness, and the sound velocity is high in the center of the piezoelectric part 1 in the Y-axis direction and slows down toward the ends. In addition to this, the same effect can be obtained in a structure in which the intermediate layer 9 has a non-uniform thickness.

Note that the intermediate layer 9 provided between the piezoelectric part 1 and the reflective layer 5 has a structure in which the sound velocity is high in the center of the piezoelectric part 1 in the Y-axis direction and gradually slows down toward the ends. In addition, the same effect can be obtained in a configuration in which the sound speed of the intermediate layer 9 is gradually, regularly, or irregularly slowed from the center to the end of the piezoelectric section 1 in the Y-axis direction. It will be done.

In addition, although the acoustic impedance of the piezoelectric part 1 or the reflective layer 5 has been described as having a uniform value from the center to the end of the piezoelectric part 1 in the Y-axis direction, in addition to this, the acoustic impedance of the piezoelectric part 1 or the reflective layer 5 is The same effect can also be obtained in a configuration in which the acoustic impedance is changed continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric part 1 in the Y-axis direction. .

As described above, according to the present embodiment, the sound velocity of the intermediate layer 9 is made to slow down continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric part 1 in the Y-axis direction.

Therefore, a high frequency response is obtained at the center of the piezoelectric section 1 in the Y-axis direction, and the response shifts from high frequency to low frequency toward the ends. In addition to being able to obtain a response, by changing the aperture size in inverse proportion to the frequency, a narrow ultrasonic beam diameter with a deep focal depth from a short distance to a long distance can be obtained, and the ultrasonic probe 10 , the ultrasonic diagnostic apparatus 100 can have high resolution.

Note that the description in each of the above embodiments is an example of a suitable ultrasound probe and ultrasound diagnostic apparatus according to the present invention, and the present invention is not limited thereto. For example, at least two of the above embodiments may be combined as appropriate.

Further, the detailed configuration and detailed operation of each part constituting the ultrasonic diagnostic apparatus 100 in each of the above embodiments can be changed as appropriate without departing from the spirit of the present invention.

100 Ultrasonic diagnostic apparatus 10, 40 Ultrasonic probe 1 Piezoelectric section 1a, 41 Piezoelectric element 2 Ground electrode 3 Signal electrode 4, 44 Backing 5 Reflection layer 6, 46 Acoustic matching layer 6a First acoustic matching layer 6b Second Acoustic matching layer 6c Third acoustic matching layer 6d Fourth acoustic matching layer 7 Signal electrical terminal 8 Acoustic lens 9 Intermediate layer 14 Cable 11 Main unit 13 Display unit 15 Operation input unit 16 Transmitting unit 17 Receiving unit 18 Image generation Section 19 Image processing section 20 DSC
21 Control section 12 Connector section

Claims (12)

a piezoelectric section in which a plurality of piezoelectric elements that transmit and receive ultrasonic waves are arranged;
a backing part provided on the back side of the piezoelectric part;
a reflecting section disposed between the piezoelectric section and the backing section and having an acoustic impedance greater than an acoustic impedance of the piezoelectric section;
an intermediate part disposed between the piezoelectric part and the reflective part,
The intermediate portion has a frequency of ultrasonic waves at a center portion of the piezoelectric portion in a direction orthogonal to an arrangement direction of the plurality of piezoelectric elements higher than a frequency of ultrasonic waves at the end portions ,
The intermediate portion has an acoustic impedance value that is equal to or lower than the acoustic impedance of the reflecting portion, and has an acoustic impedance value that is continuous, stepwise, regular, or irregular in the direction from the center portion to the end portion of the piezoelectric portion. Regularly reduce acoustic impedance,
The intermediate portion is a composite of a first material having an acoustic impedance value equal to or lower than the acoustic impedance of the reflecting portion and a second material having an acoustic impedance smaller than the first material. , an ultrasonic probe in which the volume ratio of the first material is large at the center of the piezoelectric part, and the volume ratio of the first material is small toward the ends ; a piezoelectric section in which a plurality of piezoelectric elements that transmit and receive ultrasonic waves are arranged;
a backing part provided on the back side of the piezoelectric part;
a reflecting section disposed between the piezoelectric section and the backing section and having an acoustic impedance greater than an acoustic impedance of the piezoelectric section;
an intermediate part disposed between the piezoelectric part and the reflective part,
The intermediate portion is a composite using a plurality of materials having different acoustic impedances, and the value of the acoustic impedance of the composite at the center of the piezoelectric portion in a direction perpendicular to the arrangement direction of the plurality of piezoelectric elements is determined at the end. An ultrasonic probe whose acoustic impedance value is larger than that of the composite body, and the frequency of the ultrasonic waves at the center is higher than the frequency of the ultrasonic waves at the ends. The intermediate portion has an acoustic impedance value that is equal to or lower than the acoustic impedance of the reflecting portion, and has an acoustic impedance value that is continuous, stepwise, regular, or irregular in the direction from the center portion to the end portion of the piezoelectric portion. The ultrasonic probe according to claim 2 , wherein the acoustic impedance is regularly reduced. The ultrasonic probe according to claim 1 or 3, wherein the intermediate portion has at least a uniform thickness, or has a thickness that increases continuously or stepwise from the center to the end of the piezoelectric portion. Child. a piezoelectric section in which a plurality of piezoelectric elements that transmit and receive ultrasonic waves are arranged;
a backing part provided on the back side of the piezoelectric part;
a reflecting section disposed between the piezoelectric section and the backing section and having an acoustic impedance greater than an acoustic impedance of the piezoelectric section;
an intermediate part disposed between the piezoelectric part and the reflective part,
The intermediate portion has a frequency of ultrasonic waves at a center portion of the piezoelectric portion in a direction orthogonal to an arrangement direction of the plurality of piezoelectric elements higher than a frequency of ultrasonic waves at the end portions ,
The intermediate portion has a value smaller than the value of the acoustic impedance of the reflecting portion, and has a thickness increasing in a direction from the center portion to the end portion of the piezoelectric portion,
The thickness of the intermediate portion may be increased continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric portion by tilting at least the piezoelectric portion or the reflective portion. ,
A plurality of grooves are provided in the piezoelectric part, the reflective part, or both,
In the ultrasonic probe , the depth of the groove is shallow at the center and becomes deeper toward the ends . a piezoelectric section in which a plurality of piezoelectric elements that transmit and receive ultrasonic waves are arranged;
a backing part provided on the back side of the piezoelectric part;
a reflecting section disposed between the piezoelectric section and the backing section and having an acoustic impedance greater than an acoustic impedance of the piezoelectric section;
an intermediate part disposed between the piezoelectric part and the reflective part,
The intermediate portion has a frequency of ultrasonic waves at a center portion of the piezoelectric portion in a direction orthogonal to an arrangement direction of the plurality of piezoelectric elements higher than a frequency of ultrasonic waves at the end portions ,
The intermediate portion has a value smaller than the value of the acoustic impedance of the reflecting portion, and has a thickness increasing in a direction from the center portion to the end portion of the piezoelectric portion,
The thickness of the intermediate portion may be increased continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric portion by tilting at least the piezoelectric portion or the reflective portion. ,
The thickness of the intermediate portion is such that at least the piezoelectric portion or the reflective portion has variations in unevenness or surface roughness, and is continuous, stepwise, or regular in the direction from the center to the end of the piezoelectric portion. or an irregularly thickened ultrasound probe. 6. The acoustic impedance of the piezoelectric part, the reflecting part, or both changes continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric part. The ultrasonic probe according to any one of . a piezoelectric section in which a plurality of piezoelectric elements that transmit and receive ultrasonic waves are arranged;
a backing part provided on the back side of the piezoelectric part;
a reflecting section disposed between the piezoelectric section and the backing section and having an acoustic impedance greater than an acoustic impedance of the piezoelectric section;
an intermediate part disposed between the piezoelectric part and the reflective part,
The intermediate portion has a frequency of ultrasonic waves at a center portion of the piezoelectric portion in a direction orthogonal to an arrangement direction of the plurality of piezoelectric elements higher than a frequency of ultrasonic waves at the end portions ,
The piezoelectric portion, the reflecting portion, or both are ultrasonic probes in which acoustic impedance changes continuously, stepwise, regularly, or irregularly from the center to the end of the piezoelectric portion. . The ultrasound probe according to any one of claims 1 to 8 , wherein the intermediate portion lowers the frequency of the ultrasound waves from the center portion toward the end portions. Claim 1: The intermediate portion changes the frequency of the ultrasonic wave from a high frequency to a low frequency continuously, stepwise, regularly or irregularly from the center to the end of the piezoelectric portion. The ultrasonic probe according to any one of 9 to 9 . One or more acoustic matching layers are provided in the direction from the piezoelectric part to the subject,
The ultrasound probe according to any one of claims 1 to 10 , wherein the acoustic matching layer has a uniform thickness. The ultrasonic probe according to any one of claims 1 to 11 ;
An ultrasonic diagnostic apparatus comprising: an image generation section that generates ultrasonic image data based on a received signal input from the ultrasonic probe.

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