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DESCRIPTION JP2013042248

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DESCRIPTION JP2013042248
Abstract: The present invention provides a technology relating to an ultrasonic probe and an
ultrasonic diagnostic imaging apparatus having a low ultrasonic wave propagation loss and a
favorable ultrasonic wave transmission rate. In an ultrasonic probe 1 including a piezoelectric
element layer 5, an acoustic matching layer 6, and an acoustic lens 9, the acoustic lens 9 is made
of a resin cross-linked composition, and from the center side of the acoustic lens 9, the acoustic
lens The crosslink density of the resin crosslink composition is adjusted and formed so as to
increase the ultrasonic wave propagation speed as it is separated in the direction intersecting
with the thickness direction of 9. [Selected figure] Figure 3
ULTRASONIC PROBE, ULTRASONIC IMAGING DEVICE, AND METHOD FOR MANUFACTURING
ULTRASONIC PROBE
[0001]
The present invention relates to an ultrasound probe, an ultrasound imaging apparatus, and a
method of manufacturing an ultrasound probe.
[0002]
The ultrasound diagnostic imaging apparatus is a medical imaging apparatus for obtaining a
tomographic image of soft tissue in a living body from the body surface in a minimally invasive
manner by an ultrasonic pulse reflection method.
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1
This ultrasound diagnostic imaging system has features such as small size, low cost, high safety
without exposure to X-rays, and high blood flow imaging by applying the Doppler effect
compared to other medical imaging devices. ing. Therefore, it is widely used in the circulatory
system (coronary of the heart), digestive system (gastrointestinal), internal medicine (liver,
pancreas, spleen), urology (kidney, bladder), and obstetrics and gynecology.
[0003]
In ultrasonic probes used in such medical ultrasonic diagnostic imaging apparatuses,
piezoelectric elements made of lead zirconate titanate are generally used to transmit and receive
ultrasonic waves with high sensitivity and high resolution. Used in As such an ultrasound probe,
a single type which is a single type probe or an array type probe in which a plurality of probes
are one-dimensionally or two-dimensionally arranged is often used. The array type is widely used
as a medical image for diagnostic tests because it can obtain a fine image.
[0004]
Further, harmonic imaging diagnosis using a harmonic signal is becoming a standard diagnostic
method because a clear diagnostic image which can not be obtained by conventional B-mode
diagnosis is obtained. In order to obtain an ultrasonic signal sufficient for performing harmonic
imaging, it is important to design how to efficiently receive harmonics that are higher in
frequency and easier to attenuate than the fundamental wave.
[0005]
Therefore, the ultrasonic probe is provided with an acoustic lens that converges the beam of
ultrasonic waves to improve the resolution. Since the acoustic lens is in close contact with the
subject (living body), it is easy to cause the subject to be in close contact with the subject, and a
material having a small attenuation factor at the frequency used for diagnosis is required.
Conventionally, silicone rubber is mainly used as such a material. Since silicone rubber has a
lower (slow) propagation velocity (hereinafter also referred to as sound velocity) than that of a
subject (living body), an acoustic lens made of silicone rubber has a convex central portion in its
cross-sectional shape. The time for the sound wave to pass through the thick part in the center is
made longer than in the thin part to make the ultrasonic waves converge. However, since silicone
rubber has a large propagation loss of ultrasonic waves, it is a difficult material to improve the
14-04-2019
2
transmission sensitivity and reception sensitivity of an ultrasonic probe. The propagation loss
depends on the frequency, and the propagation loss particularly increases at high frequencies, so
it can be said that the material is unsuitable for harmonic imaging using harmonic signals that
are high frequencies.
[0006]
For example, polymethylpentene is known as a material having less propagation loss as
compared to the silicone rubber. Since polymethylpentene has a higher sound velocity (faster)
than the subject (living body), it is necessary to form a polymethylpentene acoustic lens so that
the central part of its cross-sectional shape is concaved to focus the ultrasonic waves. is there.
However, if the cross-sectional shape of the acoustic lens is concave, the contact with the surface
of the subject (living body) is poor, and if an ultrasonic jelly is used, air bubbles form between the
acoustic lens and the subject (living body) There is a possibility that a clear image can not be
obtained due to mixing or the like. In order to eliminate such problems, the flat surface side of
the concave acoustic lens using polymethylpentene is the biological contact side, the concave
side is the piezoelectric element side, the concave portion is filled with the acoustic medium, and
the air layer is not interposed. An acoustic lens is known (see, for example, Patent Document 1).
[0007]
In addition, an additive is added so that the content ratio changes as being separated from the
piezoelectric element, and the acoustic impedance between the piezoelectric element and the
acoustic lens is gradually changed to improve the transmission / reception sensitivity of
ultrasonic waves. There is known a technique related to an ultrasonic probe provided with a
matching lens (see, for example, Patent Document 2).
[0008]
In addition, on both sides of the central portion of the lens, there is provided a peripheral portion
composed of a plurality of layers so that the propagation velocity of the ultrasonic wave
increases with distance from the central portion, and the cross-sectional shape is formed flat.
There is known a technology relating to an acoustic lens to be processed (see, for example,
Patent Document 3).
[0009]
JP-A-6-254100 JP-A-2006-263385 JP-A-2010-252065
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[0010]
However, in the case of Patent Document 1 described above, if the acoustic medium filling the
concave portion of the polymethylpentene acoustic lens is silicone rubber, there is a problem that
the propagation loss is increased accordingly.
[0011]
Further, in the case of Patent Document 2 described above, the acoustic matching lens has a
sound velocity distribution in which the acoustic impedance with the piezoelectric element
gradually changes, but this acoustic matching lens has a convex shape based on silicone. There is
still a problem that the transmission loss of the ultrasonic wave is still large because it has.
In addition, since this acoustic matching lens is based on silicone, silicone with weak physical
strength is worn or deformed, and the focal length of the lens changes to deteriorate the
convergence of ultrasonic waves. There was a problem.
[0012]
Further, in the case of Patent Document 3 above, since the propagation speed of the ultrasonic
wave is made different by adjusting the amount of the particulate additive added to the plurality
of layers in the peripheral portion, the ultrasonic waves are scattered by the particles. And there
is a problem that the transmittance of ultrasonic waves is reduced.
[0013]
An object of the present invention is to provide a technology relating to an ultrasound probe and
an ultrasound imaging apparatus having a low ultrasound transmission loss and a favorable
ultrasound transmission rate.
[0014]
In order to solve the above problems, the invention according to claim 1 is characterized in that:
a piezoelectric element unit for transmitting and receiving an ultrasonic wave; an ultrasonic wave
transmitted from the piezoelectric element unit is emitted from a lens surface and converged to a
predetermined focal length. Ultrasonic probe comprising: an acoustic lens to be used; an acoustic
matching layer disposed between the piezoelectric element portion and the acoustic lens for
matching the acoustic impedance between the piezoelectric element portion and the acoustic lens
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Wherein at least one of the acoustic lens and the acoustic matching layer includes a resin crosslinking composition, and the resin cross-linking composition intersects the thickness direction of
the resin cross-linking composition from the center side of the resin cross-linking composition It
is characterized in that the crosslink density is adjusted and formed in a plane perpendicular to
the transmission direction of the ultrasonic wave so that the propagation velocity of the
ultrasonic wave increases as the directions are separated.
[0015]
The invention according to claim 2 is the ultrasonic probe according to claim 1, wherein the resin
cross-linked composition intersects the thickness direction of the resin cross-linked composition
from the center side of the resin cross-linked composition It is characterized in that the crosslink
density is formed to be higher as it is separated in the direction.
[0016]
The invention according to claim 3 is the ultrasonic probe according to claim 1 or 2, wherein the
crosslink density of the resin cross-linked composition is adjusted according to the electron beam
intensity irradiated to the resin cross-linked composition. It is characterized by
[0017]
The invention as set forth in claim 4 is the ultrasonic probe according to any one of claims 1 to 3,
wherein the resin cross-linked composition is formed by adding an amount of the cross-linking
agent added to the resin cross-linked composition. Accordingly, the crosslink density is adjusted.
[0018]
The invention according to claim 5 is the ultrasonic probe according to any one of claims 1 to 4,
wherein the acoustic lens includes the resin cross-linked composition, and the acoustic lens is the
acoustic lens. The cross-link density of the resin cross-linked composition is adjusted so that the
propagation speed of the ultrasonic wave increases as it is separated from the center side of the
cross-section in the direction crossing the thickness direction of the acoustic lens. Do.
[0019]
The invention according to claim 6 is characterized in that, in the ultrasound probe according to
claim 5, the lens surface is planar.
[0020]
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The invention according to claim 7 is the ultrasonic probe according to any one of claims 1 to 4,
wherein the acoustic matching layer includes the resin cross-linked composition, and the acoustic
matching layer is The crosslink density of the resin cross-linked composition is adjusted so as to
increase the ultrasonic wave propagation speed as it is separated from the center side of the
acoustic matching layer in the direction intersecting with the thickness direction of the acoustic
matching layer. It is characterized by
[0021]
The invention according to claim 8 is an ultrasonic diagnostic imaging apparatus which transmits
ultrasonic waves toward a subject and forms an image in accordance with a reflected wave of the
ultrasonic wave received from the subject, And the ultrasonic probe according to any one of the
above.
[0022]
The invention according to claim 9 is the method for producing an ultrasonic probe according to
any one of claims 1 to 7, which comprises: a plate member in which a resin material containing a
crosslinking agent is formed into a flat plate shape. And an electron beam irradiation step of
forming the resin cross-linked composition by irradiating an electron beam, and in the electron
beam irradiation step, the thickness direction of the plate member from the center side with
respect to the center side of the plate member The intensity of the electron beam irradiated to
the plate member is increased as the distance in the crossing direction is increased, and the
crosslink density of the resin crosslink composition is adjusted.
[0023]
The invention according to claim 10 is the method for manufacturing an ultrasonic probe
according to claim 9, wherein in the electron beam irradiation step, the electron beam is
irradiated in a state where a part of the plate member is provided with a mask. Each time the
arrangement of the mask is switched, the crosslink density is adjusted to be different for each
part of the resin crosslink composition.
[0024]
The invention according to claim 11 is the method for manufacturing an ultrasonic probe
according to claim 9, wherein in the electron beam irradiation step, the plate member is provided
with a mask having different electron beam transmittances for each portion. It is characterized in
that an electron beam is irradiated to adjust the crosslink density to be different for each part of
the resin crosslink composition.
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[0025]
According to the present invention, it is possible to obtain an ultrasonic probe and an ultrasonic
diagnostic imaging apparatus having a low ultrasonic wave propagation loss and a favorable
ultrasonic wave transmission rate.
[0026]
It is a perspective view which shows the external appearance structure of an ultrasound
diagnostic imaging apparatus.
It is a block diagram showing an internal configuration of an ultrasound diagnostic imaging
apparatus.
It is a schematic diagram showing an ultrasound probe.
It is a schematic perspective view which shows an acoustic lens.
It is explanatory drawing which shows the principle which an acoustic lens makes an ultrasonic
wave converge.
It is explanatory drawing (a) (b) (c) (d) which shows the manufacturing process of an acoustic
lens.
It is explanatory drawing regarding the transmission sensitivity of an acoustic lens.
It is explanatory drawing (a) (b) (c) (d) which shows the manufacturing method of an acoustic
lens.
It is the schematic which shows the modification of an ultrasound probe.
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It is explanatory drawing (a) (b) (c) (d) which shows the manufacturing process of an acoustic
matching layer.
[0027]
Hereinafter, preferred embodiments of the present invention will be described with reference to
the drawings.
However, although various limitations preferable for carrying out the present invention are given
to the embodiments described below, the scope of the invention is not limited to the following
embodiments and the illustrated examples.
[0028]
(Ultrasound Image Diagnostic Apparatus) The ultrasonic image diagnostic apparatus transmits an
ultrasonic wave (ultrasound signal) to a subject such as a living body and receives a reflected
wave (echo) of the ultrasonic wave reflected in the subject. It is a medical device that images and
displays the internal state inside the subject as an ultrasound image based on the received wave.
FIG. 1 is a diagram showing an appearance configuration of an ultrasound diagnostic imaging
apparatus in the present embodiment.
FIG. 2 is a block diagram showing an electrical configuration of the ultrasound diagnostic
imaging apparatus in the present embodiment.
[0029]
As shown in FIGS. 1 and 2, the ultrasonic diagnostic imaging apparatus 100 includes an
apparatus main body 10 and an ultrasonic probe 1 (1 a) connected to the apparatus main body
10 via a cable 17.
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The apparatus body 10 includes, for example, an operation input unit 11, a transmission circuit
12, a reception circuit 13, an image processing unit 14, a display unit 15, a control unit 16, and
the like.
[0030]
The ultrasound probe 1 (1a) transmits an ultrasound (ultrasound signal) to a subject and receives
a reflected wave of the ultrasound reflected in the subject.
The ultrasound probe 1 (1a) is connected to the apparatus main body 10 via the cable 17, and is
electrically connected to the transmission circuit 12 and the reception circuit 13.
[0031]
The transmission circuit 12 transmits an electric signal to the ultrasonic probe 1 (1a) through the
cable 17 according to a command from the control unit 16, and the ultrasonic probe 1 (1a)
directs the ultrasonic wave toward the object. Send
The receiving circuit 13 performs an ultrasonic probe via the cable 17 according to a command
from the control unit 16 with an electric signal according to the reflected wave of the ultrasonic
wave from the inside of the subject received by the ultrasonic probe 1 (1a). Receive from child 1
(1a).
[0032]
The image processing unit 14 images the internal state inside the subject as an ultrasound image
based on the electrical signal received by the receiving circuit 13 according to an instruction of
the control unit 16.
The display unit 15 displays the ultrasound image imaged by the image processing unit 14
according to an instruction of the control unit 16.
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The display unit 15 includes, for example, a liquid crystal panel.
[0033]
The operation input unit 11 is configured of a switch, a keyboard, and the like, and is provided to
input data such as a command that the user instructs to start diagnosis and personal information
of a subject. The control unit 16 includes a CPU, a memory, and the like, and controls each unit
of the ultrasound diagnostic imaging apparatus 100 (apparatus main body 10) according to a
procedure programmed in advance based on a command or the like input from the operation
input unit 11. Do.
[0034]
(Ultrasound Probe) Next, an ultrasound probe of the ultrasound diagnostic imaging apparatus
100 will be described.
[0035]
Embodiment 1 of the ultrasound probe of the ultrasound diagnostic imaging apparatus 100 will
be described.
In the present embodiment, an ultrasonic probe that transmits and receives ultrasonic waves
with a single piezoelectric element is described as an example, but the present invention is not
limited to this, and a plurality of piezoelectric elements (for example, transmission piezoelectrics)
The present invention is also applicable to an ultrasonic probe having an element and a
piezoelectric element for reception. In the following description, various directions will be
described based on coordinate axes indicated by X, Y, and Z in the drawing. The X-axis direction
is an elevation direction, the Y-axis direction is an arrangement direction (scanning direction) of
the piezoelectric elements, and the positive Z-axis direction is a direction to transmit ultrasonic
waves.
[0036]
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10
The ultrasound probe 1 includes, for example, a piezoelectric element layer 5, an acoustic
matching layer 6, an acoustic lens 9 and the like as shown in FIG. Specifically, in the ultrasonic
probe 1, the second electrode 25, the piezoelectric element layer 5, the first electrode 56, the
acoustic matching layer 6, and the acoustic lens 9 are sequentially stacked in the Z-axis direction
on the backing material 2 It has the following configuration. Since the second electrode 25 and
the first electrode 56 are extremely thin members (thin films) as compared with other constituent
layers, they are illustrated as linear members at the interface in FIG.
[0037]
The piezoelectric element layer 5 is, for example, an inorganic piezoelectric material such as lead
zirconate titanate, an organic piezoelectric material such as polyvinylidene fluoride or a
copolymer of vinylidene fluoride, a material obtained by combining an inorganic piezoelectric
material and an organic piezoelectric material, Or the like, and is provided with a first electrode
56 and a second electrode 25 which form a pair on both sides in the thickness direction. The
thickness of the piezoelectric element layer 5 varies depending on the required transmission /
reception frequency, but is approximately 10 to 200 μm. The piezoelectric element layer 5 may
be a laminated structure in which two or more element layers are laminated regardless of the
illustrated single-layer structure.
[0038]
The first electrode 56 and the second electrode 25 are connected to the cable 17 by a flexible
printed circuit or a connector (not shown), and are connected to the transmission circuit 12 via
the cable 17. Then, when an electric signal is input from the transmission circuit 12 to the first
electrode 56 and the second electrode 25, the piezoelectric element vibrates, and ultrasonic
waves are transmitted from the piezoelectric element layer 5 in the positive Z-axis direction. .
Further, the first electrode 56 and the second electrode 25 are connected to the cable 17 by a
connector (not shown), and are connected to the receiving circuit 13 via the cable 17. Then,
when the piezoelectric element layer 5 receives the reflection wave of the ultrasonic wave
reflected by the object and the piezoelectric element vibrates, electricity is generated between the
first electrode 56 and the second electrode 25 sandwiching the piezoelectric element according
to the vibration. A signal is generated. The electrical signal generated between the first electrode
56 and the second electrode 25 is received by the receiving circuit 13 via the cable 17 and is
imaged by the image processing unit 14. The first electrode 56 and the second electrode 25 are
electrodes formed by depositing thin films of metal materials such as gold, silver, aluminum or
14-04-2019
11
the like on both surfaces of the piezoelectric element layer 5 by vapor deposition or
photolithography. is there. A portion in which the first electrode 56, the second electrode 25, and
the piezoelectric element layer 5 are stacked functions as a piezoelectric element portion.
[0039]
The acoustic matching layer 6 has, for example, an acoustic impedance between the acoustic
impedance of the human body which is one of the objects and the piezoelectric element layer 5,
and matching of the acoustic impedance between the piezoelectric element layer 5 and the
acoustic lens 9 Have a function to The acoustic matching layer 6 is, for example, a member
formed by molding a resin material. The material used for the acoustic matching layer 6 is
preferably a material having an acoustic impedance of about 1.7 to 20 and a sound velocity of
2000 m / s or more and 4000 m / s or less. For example, an epoxy resin, a mixture of an epoxy
resin and a filler made of an inorganic material, or a machinable ceramic can be suitably used.
[0040]
The piezoelectric element layer 5 on which the first electrode 56 and the second electrode 25 are
formed and the acoustic matching layer 6 are sequentially laminated on the backing material 2
and are adhered by an adhesive. Then, after bonding the piezoelectric element layer 5 and the
acoustic matching layer 6 to the backing material 2, dicing is performed from the side of the
acoustic matching layer 6 in the direction opposite to the ultrasonic radiation direction to
electrically insulate each element Element division is performed. After filling a filler made of
silicone resin or the like in grooves (not shown) formed by the dicing, the acoustic lens 9 is
adhered and laminated on the uppermost layer on the acoustic matching layer 6.
[0041]
The acoustic lens 9 has a function of causing the ultrasonic waves transmitted from the
piezoelectric element layer 5 to converge to a predetermined focal length. The acoustic lens 9
only needs to have a function of focusing the ultrasonic waves in at least one direction (in the
present embodiment, the X-axis direction), and it is necessary to focus the ultrasonic waves at
one point in all directions. It does not have to be. It also has the same function as the acoustic
matching layer 6 to match the acoustic impedance of the human body, which is one of the
objects, and the piezoelectric element layer 5. The acoustic lens 9 is, as shown in FIG. 3 and FIG.
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4, composed of a central portion 7 and peripheral portions 8 respectively disposed on both sides
of the central portion 7. In the following description, various directions will be described based
on coordinate axes indicated by X, Y, and Z in the drawing. The X-axis direction is an elevation
direction (dicing groove direction), and the Z-axis positive direction is a direction for transmitting
an ultrasonic wave.
[0042]
As shown in FIG. 4, the acoustic lens 9 has a rectangular parallelepiped shape having a width W
in the X-axis direction, a length L in the Y-axis direction, and a thickness H in the Z-axis direction.
The lower surface in the negative direction of the Z-axis is a lens surface on which the ultrasonic
wave emitted from the piezoelectric element (not shown) is incident, and the upper surface in the
positive direction of the Z-axis is not shown. It is a lens surface which adheres to a sample and
emits an ultrasonic wave to the inside of the sample. The two lens surfaces forming a pair on
both surfaces in the Z-axis direction are both formed in a planar shape parallel to the XY plane.
Although the lens surface for emitting the ultrasonic wave may be a convex surface, it is
preferable to make it planar from the viewpoint of suppressing the propagation loss of the
ultrasonic wave as much as possible.
[0043]
The acoustic lens 9 is made of a resin crosslinking composition, and has a relatively low crosslink
density in the central portion 7 and a crosslink density higher than the central portion 7 and an
ultrasonic wave propagation speed (also referred to as the speed of sound) faster than the central
portion 7 A peripheral portion 8 is provided. The peripheral portion 8 is formed such that the
crosslink density becomes higher as it is separated from the central portion 7 in the direction
intersecting the thickness direction of the acoustic lens 9. The peripheral portion 8 of the
acoustic lens 9 has a plurality of regions (layers) which are substantially orthogonal to the lens
surface (X-Y surface) and which are divided in parallel to the Y-Z surface. The peripheral portion
8 in this embodiment is, for example, disposed on both sides of the central portion 7 and has
three layers divided in parallel to the YZ plane. Specifically, as shown in FIG. 4, the peripheral
portion 8 is formed along the X-axis direction with the same width in the direction separating
from the central portion 7 side, and the layers 8a to 8b divided in parallel to the YZ plane It has
three layers of 8c.
[0044]
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The layers 8a to 8c of the peripheral portion 8 are formed by adjusting the crosslink density of
the resin crosslink composition so that the propagation speed (sound velocity) of the ultrasonic
wave increases as the distance from the central portion 7 increases. ing. For example, if it is
assumed that the central portion 7 has a crosslinking density at which the sound velocity V1 is
reached, the layer 8a of the peripheral portion 8 is adjusted to the crosslinking density at which
the acoustic velocity Va is faster than the acoustic velocity V1. In addition, the layer 8b of the
peripheral portion 8 is adjusted to a crosslink density which makes the sound velocity Vb faster
than the sound velocity Va. Similarly, the layer 8c of the peripheral portion 8 is adjusted to a
crosslink density which makes the sound velocity Vc faster than the sound velocity Vb. The
outermost layer 8 c is formed to be adjusted to the crosslink density which gives the fastest
sound velocity Vc in the acoustic lens 9. Thus, in the acoustic lens 9, the crosslink density is
adjusted so that a distribution is formed in the propagation velocity of the ultrasonic wave in the
plane perpendicular to the transmission direction of the ultrasonic wave.
[0045]
Here, based on FIG. 5, the principle of the acoustic lens 9 of the present invention for converging
an ultrasonic wave will be described. In FIG. 5, in order to simplify the description, the case
where all the peripheral portions 8 are formed of the same material will be described as an
example. The central portion 7 is made of a material of sound velocity V1, and the peripheral
portion 8 is made of a material of sound velocity V2 faster than the sound velocity V1. The lens
surface in the positive Z-axis direction of the acoustic lens 9 is in contact with the liquid of the
sound velocity V0 stored in a container (not shown).
[0046]
I2 indicates a state in which an ultrasonic wave incident from the center of the central portion 7
passes through the central portion 7 and travels through the liquid. I1 indicates a state in which
an ultrasonic wave incident from the center of the peripheral portion 8 on the left side in the
figure passes through the peripheral portion 8 and travels through the liquid and converges with
I2 at the position of the focal distance f (point q) . x is the distance between I1 and I2 incident on
the acoustic lens 7;
[0047]
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Since the velocity of sound V2 of the peripheral portion 8 is larger than the velocity of sound V1
of the central portion 7, the ultrasonic waves entering from the peripheral portion 8
simultaneously reach the liquid faster than the ultrasonic waves incident from the central portion
7 and make the liquid concentrically. The wavefront advances. The time difference t1 of passing
the acoustic lens 9 between the ultrasonic wave incident from the peripheral portion 8 and the
ultrasonic wave incident from the central portion 7 can be obtained by the following equation
(1).
[0048]
[0049]
In FIG. 5, m is a distance by which the ultrasonic wave incident from the peripheral portion 8
travels in the liquid during the time difference t1.
Assuming that the sound velocity of the liquid is V0, the distance m can be obtained by the
following equation (2). m = V0 × t1 (2) The ultrasonic wave incident from the center of the
peripheral portion 8 on the left side in the figure travels the distance m, and then travels the
same distance f as the ultrasonic wave incident from the center of the central portion 7 It
converges to the point q. The focal length f can be obtained by the following equation (3) using
the Pythagorean theorem. f = (x <2> -m <2>) / 2 m (3) When Formula (1) and Formula (2) are
substituted into this Formula (3), the focal distance f is the following Formula (4) You can ask for
H is the width (thickness) of the acoustic lens 9 in the Z-axis direction, V1 is the speed of sound
of the central portion 7, V2 is the speed of sound of the peripheral portion 8, and V0 is the speed
of sound of the liquid.
[0050]
[0051]
Thus, the ultrasonic wave I2 incident from the central portion 7 and the ultrasonic wave I1
incident from the peripheral portion 8 can be converged to one point (point q) by the difference
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15
in the sound velocity between the central portion 7 and the peripheral portion 8.
For example, assuming that V0 = 1530 m / sec, V1 = 2500 m / sec, H = 2.5 mm, x = 3 mm, and
V2 = 2771 m / sec, the focal length f is f = 30 mm. Also, when the other values are the same and
H is changed to 5 mm, the focal length f is f = 14.9 mm.
[0052]
And as shown in FIG. 4, when the peripheral part 8 is comprised from three layers of the both
sides which pinched | interposed the center part 7, each layer (8a-8c of the peripheral part 8 is
paralleled with the ultrasonic wave which injected from the center part 7). The speed of sound of
each layer (8a to 8c) is set so that the ultrasonic wave incident on () converges on one point. For
example, the sound velocity V2 of the resin cross-linked composition that forms the peripheral
portion 8 that converges to the focal distance f can be obtained by the following equation (5).
[0053]
[0054]
For example, assuming that the focal length f = 30 mm, V0 = 1530 m / sec, V1 = 2500 m / sec, H
= 2.5 mm, x = 3 mm, then V2 = 2771 m / sec.
Similarly, the sound velocities Va to Vc of the resin cross-linked composition for forming the
layers 8a to 8c for focusing the ultrasonic waves at the same focal length f can be determined
using the equation (5). In addition, as described later, each layer (8a to 8c) of the peripheral
portion 8 having different sound velocities adjusts the crosslink density of the resin cross-linking
composition, and the cross-link density of the resin cross-linking composition is different for each
layer of the peripheral portion 8 Can be obtained by the reaction (see Table 1).
[0055]
Next, a method of manufacturing the acoustic lens 9 will be described with respect to a method
of manufacturing an ultrasonic probe.
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[0056]
In manufacturing the acoustic lens 9, as shown in FIG. 6A, a lens plate member 9a to be the
acoustic lens 9 is prepared.
The lens plate member 9a is a plate-like member in which a resin material containing a
crosslinking agent is formed in a flat plate shape. For the lens plate member 9a, for example, a
polyolefin-based resin material, an aromatic polyamide-based resin material or the like can be
used as a resin material, and as a crosslinking agent, triallyl isocyanurate (TAIC), diallyl mono
Glycidyl isocyanurate (DA-MGIC) etc. can be used.
[0057]
Here, the lens plate member 9a will be described.
[0058]
[0059]
For example, as shown in Table 1, 0 to 5 wt% of a crosslinking agent is added to various
predetermined resin materials (Nos. 1 to 8), and a phenolic antioxidant (Irganox 1010 (Ciba
Specialty Chemicals Co., Ltd.) 1% by weight) and molding a plate member 1 mm thick and 50 mm
square by injection molding.
The plate member was irradiated with an electron beam under each of the conditions described
in Table 1 to promote the crosslinking reaction of the plate member to form a resin crosslinked
composition.
After cooling, the plate member was taken out and the storage elastic modulus was measured by
DMA (Dynamic Viscoelasticity Measurement Device). Further, the sound velocity of the plate
member was measured by a sound velocity measuring device. (See Table 1). Then, as shown in
Table 1, according to the electron beam intensity (irradiation amount, irradiation time, irradiation
temperature) of the electron beam conditions applied to the plate member, the cross-link density
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17
of the resin cross-linking composition is made different to obtain storage elastic modulus Can be
different. That is, it was found that the speed of sound of the plate member (resin cross-linked
composition) was changed according to the electron beam intensity applied to the plate member
(resin cross-linked composition). Thus, the crosslink density of the resin crosslink composition
can be adjusted by the electron beam intensity (irradiation amount, irradiation time, irradiation
temperature) applied to the lens plate member 9a, and the desired sound velocity can be set. . In
addition, regarding the crosslinking density of the resin crosslinked composition, if the storage
elastic modulus can be adjusted to a range of about 1 to 10 GPa and the speed of sound to a
range of about 2000 to 3000 m / s, it can be preferably used for the acoustic lens 9 of the
present invention.
[0060]
In this embodiment, TPX (made by Mitsui Chemicals, Inc.), which is a polyolefin resin material, 3
wt% of triallyl isocyanurate (TAIC), and a phenolic antioxidant (IRGANOX 1010 (Ciba Specialty
Chemicals Co., Ltd.) 6% (width (W) 5.6 mm, length (L) 42.5 mm, thickness (H) 0.5 mm by mixing
and molding 1 wt% of the product). As shown in a), a lens plate member 9a was obtained.
[0061]
The lens plate member 9a is irradiated with an electron beam to perform an electron beam
irradiation process of forming a resin cross-linked composition.
For example, first, as shown in FIG. 6B, the first mask M1 is a lens that covers a portion of the
lens plate member 9a and is provided with an opening at a portion corresponding to the layer 8a
of the peripheral portion 8 of the acoustic lens 9. For example, the layer 8a of the peripheral
portion 8 is irradiated with an electron beam intensity of an irradiation dose of 400 [kGy], an
irradiation time of 1 [h], and an irradiation temperature of 40 [° C]. Form Then, as shown in FIG.
6C, a second mask M2 is provided that covers a portion of the lens plate member 9a and is
provided with an opening in a portion corresponding to the layer 8b of the peripheral portion 8
of the acoustic lens 9. The layer 8b of the peripheral portion 8 is formed on the member 9a by
performing electron beam irradiation with an electron beam intensity of, for example, an
irradiation amount of 600 [kGy], an irradiation time of 1 [h] and an irradiation temperature of 40
[° C]. Do. Then, as shown in FIG. 6D, the third mask M3 is provided to cover a portion of the lens
plate member 9a and to have an opening provided in a portion corresponding to the layer 8c of
the peripheral portion 8 of the acoustic lens 9. Electron beam irradiation of electron beam
intensity of 800 [kGy], irradiation time of 1 [h], irradiation temperature of 40 [° C.] is performed
on the member 9a, for example, to form the layer 8c of the peripheral portion 8 Do.
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[0062]
The acoustic lens 9 can be manufactured by such a three-step electron beam irradiation process.
[0063]
Then, on the backing material 2, a piezoelectric element layer 5 processed into a size of width
(W) 5.6 mm, length (L) 42.5 mm, thickness (H) 0.16 mm, and electrodes provided on both sides
Then, the acoustic matching layer 6 was laminated and adhered with an epoxy adhesive, for
example.
Furthermore, on the bonded acoustic matching layer 6, the acoustic lens 9 manufactured by the
above-described three-stage electron beam irradiation process is adhered, and the 0.2 mm pitch
(cut width 0.02 mm) in the major axis direction (azimuth direction) The element was converted to
an element to obtain an ultrasonic probe 1. The ultrasonic probe 1 was applied to a threedimensional scanning acoustic intensity measurement system (AMS) (manufactured by SONORA)
to measure the beam profile of one element. As a result, the transmission sensitivity in the depth
direction was as shown in FIG. 7 and was found to have a focus at a depth of about 27 mm.
[0064]
In this manner, the cross-link density of the resin cross-linked composition is adjusted so as to
increase the propagation speed of the ultrasonic wave as it is separated from the center side of
the acoustic lens 9 in the direction intersecting the thickness direction. The lens 9 has a flat
plate-like lens shape, and even with a structure having a flat lens surface, it is possible to
preferably focus the ultrasonic wave on a predetermined focal point. As a result, it is possible to
eliminate the problem related to high frequency attenuation by the lens thick portion in the
convex lens, and to solve the problem related to air bubble mixing at the time of measurement in
the concave lens.
[0065]
As described above, since the acoustic lens 9 of the present invention has a low ultrasonic wave
propagation loss and a good ultrasonic wave transmission rate, the technique related to the
ultrasonic probe and the ultrasonic image diagnostic apparatus can be improved. it can.
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[0066]
In addition, the manufacturing method of the acoustic lens 9 is not restricted to the said
embodiment.
In the above embodiment, as shown in FIGS. 6A to 6D, when manufacturing the acoustic lens 9,
the electron beam is irradiated in a state where the mask is disposed so as to cover a part of the
lens plate member 9a. That was repeated every time the mask placement was switched.
Specifically, using the three masks of the first mask M 1, the second mask M 2, and the third
mask M 3, the resin cross-linked composition is obtained by a three-stage electron beam
irradiation process in which the arrangement for irradiating the electron beam is switched.
Although the acoustic lens 9 in which the crosslink density is different for each part was
manufactured, it is also possible to manufacture the acoustic lens 9 in which the crosslink
density is different for each part of the resin crosslink composition by one electron beam
irradiation step using one mask. it can.
[0067]
For example, as shown in FIG. 8 (a), the layer 8a of the peripheral portion 8 of the acoustic lens 9
is made to be gradually thinner as it is separated from the thickest portion corresponding to the
central portion 7 of the acoustic lens 9. A mask M4 having a portion corresponding to the layer
8b, a portion corresponding to the layer 8c, and a portion corresponding to the layer 8c, and the
cross section of which is formed in a substantially stepped shape is disposed on the lens plate
member 9a. The acoustic lens 9 can also be manufactured by performing intense electron beam
irradiation. The ultrasonic probe 1 using this acoustic lens 9 was applied to a three-dimensional
scanning acoustic intensity measurement system (AMS) (manufactured by SONORA), and the
beam profile of one element was measured. As a result, it was found that the transmission
sensitivity in the depth direction (the acoustic intensity of the azimuth cross section) is
substantially the same as that in FIG. 7 and has a focus at a depth of about 28 mm.
[0068]
Further, as shown in FIG. 8B, the portion corresponding to the central portion 7 of the acoustic
14-04-2019
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lens 9 is the thickest, and has a curved surface so as to be gradually thinner as it is separated
from the central side, The acoustic lens 9 can also be manufactured by arranging the mask M5
formed in a circular or substantially bowl-like shape on the lens plate member 9a and performing
electron beam irradiation with a predetermined electron beam intensity. In this case, the
boundaries between the layer 8a, the layer 8b, and the layer 8c in the peripheral portion 8 of the
acoustic lens 9 are not clear, and the crosslinking density of the resin cross-linking composition
changes continuously. The crosslink density is formed to be high such that the propagation
velocity of the ultrasonic wave is increased toward the end of 8.
[0069]
Further, as shown in FIG. 8C, the portion corresponding to the center of the central portion 7 of
the acoustic lens 9 is the thickest, and the cross section is formed in a triangular shape so as to
be gradually thinner as it is separated from the center side. The acoustic lens 9 can also be
manufactured by arranging the mask M6 on the lens plate member 9a and performing electron
beam irradiation with a predetermined electron beam intensity. Also in this case, the crosslink
density of the resin crosslink composition is continuously changed, and the crosslink density is
formed to be high such that the propagation speed of the ultrasonic wave increases toward the
end of the peripheral portion 8 of the acoustic lens 9.
[0070]
Further, as shown in FIG. 8D, the portion corresponding to the center of the central portion 7 of
the acoustic lens 9 is thickest, and the cross section is formed in a substantially bell shape so as
to be gradually thinner as it is separated from the center side. The acoustic lens 9 can also be
manufactured by arranging the mask M7 on the lens plate member 9a and performing electron
beam irradiation with a predetermined electron beam intensity. Also in this case, the crosslink
density of the resin crosslink composition is continuously changed, and the crosslink density is
formed to be high such that the propagation speed of the ultrasonic wave increases toward the
end of the peripheral portion 8 of the acoustic lens 9.
[0071]
The present invention is not limited to the above embodiment. For example, as shown in FIG. 9,
the acoustic matching layer in the ultrasonic probe can also have the same layer configuration as
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the acoustic lens 9.
[0072]
For example, as shown in FIG. 9, the ultrasound probe 1a includes a piezoelectric element layer
5, an acoustic matching layer 66, an acoustic lens 9, and the like. Specifically, in the ultrasound
probe 1a, the second electrode 25, the piezoelectric element layer 5, the first electrode 56, the
acoustic matching layer 66, and the acoustic lens 9 are sequentially stacked in the Z-axis
direction on the backing material 2 It has the following configuration.
[0073]
As shown in FIG. 9, the acoustic matching layer 66 is composed of a central portion 3 and
peripheral portions 4 disposed on both sides of the central portion 3. The acoustic matching
layer 66 is made of a resin cross-linking composition, and the central portion 3 having a
relatively low cross-link density and the cross-link density higher than the central portion 3 and
the ultrasonic wave propagation velocity (also called the speed of sound) than the central portion
3 Have a large (fast) perimeter 4. The peripheral portion 4 is formed such that the crosslink
density becomes higher as it is separated from the central portion 3 in the direction intersecting
the thickness direction of the acoustic matching layer 66. The peripheral portion 4 of the
acoustic matching layer 66 has a plurality of regions (layers) which are oriented substantially
orthogonal to the X-Y plane and are divided in parallel to the Y-Z plane. The peripheral part 4 in
this embodiment is, for example, disposed on both sides of the central part 3 and has three layers
divided in parallel to the YZ plane. Specifically, as shown in FIG. 10D, the peripheral portion 4 is
formed in the same width in the direction separating from the central portion 3 side along the Xaxis direction, and is a layer divided in parallel to the YZ plane. It has three layers 4a to 4c. In the
layers 4a to 4c of the peripheral portion 4, the crosslink density of the resin cross-linked
composition is adjusted so that the ultrasonic wave propagation speed (also referred to as the
speed of sound) becomes larger (faster) as the distance from the central portion 3 increases.
Being formed. Thus, the crosslink density of the resin cross-linked composition is adjusted so that
the propagation speed of the ultrasonic wave increases as it is separated from the center side of
the acoustic matching layer 66 in the direction intersecting with the thickness direction thereof
(ultrasonic wave In addition to the acoustic lens 9, the acoustic matching layer 66 is also
provided with the same speed difference of sound speed so that the crosslink density is adjusted
so that a distribution is formed in the propagation velocity of ultrasonic waves in a plane
perpendicular to the transmission direction. Thus, the acoustic matching layer 66 also has the
same function as the acoustic lens 9 for focusing the ultrasonic waves transmitted from the
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piezoelectric element layer 5 to a predetermined focal length, and the time difference is sufficient
even if the acoustic lens 9 is thinned. Can be generated in the plane, the same focus can be
achieved with a thin acoustic lens, and the propagation attenuation by the acoustic lens can be
reduced. The technique of combining the acoustic matching layer 66 and the acoustic lens 9
(ultrasound probe 1a) is particularly useful at high frequencies where the influence of
propagation attenuation is large. In addition, as the acoustic lens 9, you may use a normal convex
lens. Also in this case, since the thickness of the acoustic lens can be reduced by the convergence
effect of the acoustic matching layer 66, the propagation loss of ultrasonic waves can be
suppressed.
[0074]
In the case where the acoustic matching layer 66 has a laminated structure including a plurality
of layers (3, 4a to 4c), the crosslink density of the resin crosslink composition may be adjusted
for all the layers, or some layers may be adjusted. The crosslink density may be adjusted only for
At this time, it is not necessary to adjust the crosslink density for the outermost layer, and the
above effect can be obtained by adjusting the crosslink density for at least one layer.
[0075]
Next, a method of manufacturing the acoustic matching layer 66 will be described with respect to
a method of manufacturing an ultrasonic probe.
[0076]
In manufacturing the acoustic matching layer 66, as shown in FIG. 10A, the acoustic matching
plate member 6a to be the acoustic matching layer 66 is prepared.
The acoustic matching plate member 6a is a plate-like member in which a resin material
containing a crosslinking agent is formed in a flat plate shape. For the acoustic matching plate
member 6a, for example, an epoxy resin material, an aromatic polyamide resin material, an
acrylic resin, a methacrylic resin or the like can be used as a resin material, and an epoxy acrylate
as a crosslinking agent is used as a basic skeleton. DA-314, DA-721, DM-201 (all manufactured
by Nagase Chemtech Inc.), etc. can be used.
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[0077]
Here, the acoustic matching plate member 6a will be described.
[0078]
[0079]
For example, as shown in Table 2, 0 to 3 wt% of a crosslinking agent is added to various
predetermined resin materials (No. 1 to 5), and a phenolic antioxidant (Irganox 1010 (Ciba
Specialty Chemicals Co., Ltd.) 1% by weight) and heat-cured, and processed to form a 1 mm thick,
50 mm square plate member.
The plate member was irradiated with an electron beam under the conditions described in Table
2 to promote the crosslinking reaction of the plate member to form a resin crosslinked
composition.
After cooling, the plate member was taken out and the storage elastic modulus was measured by
DMA (Dynamic Viscoelasticity Measurement Device). The sound velocity of the plate member
(resin crosslinked composition) can be determined based on the storage elastic modulus (see
Table 2). And as shown in Table 2, according to the electron beam intensity (irradiation amount,
irradiation time, irradiation temperature) of the electron beam conditions given to the plate
member, the cross-link density of the resin cross-linking composition is made different to obtain
storage elastic modulus Can be different. That is, it was found that the speed of sound of the
plate member (resin cross-linked composition) was changed according to the electron beam
intensity applied to the plate member (resin cross-linked composition). Thus, the crosslink
density of the resin cross-linked composition can be adjusted by the electron beam intensity
(irradiation amount, irradiation time, irradiation temperature) applied to the acoustic matching
plate member 6a, and the desired sound velocity can be set. it can. In addition, regarding the
crosslink density of the resin cross-linked composition, if the storage elastic modulus can be
adjusted to about 1 to 10 GPa and the sound velocity can be adjusted to the range of about 2000
to 3000 m / s, it can be preferably used for the acoustic matching layer 66 of the present
invention.
[0080]
In this embodiment, C-1001A / B (made by Tesk Co., Ltd.) which is an epoxy resin material, 3
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wt% of DA-314, and a phenolic antioxidant (Irganox 1010 (manufactured by Ciba Specialty
Chemicals Co., Ltd.) ) After heat curing by compounding 1 wt%, the processed plate member is
processed into a size of width (W) 5.6 mm, length (L) 42.5 mm, thickness (H) 0.5 mm, As shown
in FIG. 10 (a), a plate member 6a for acoustic matching was obtained.
[0081]
The acoustic alignment plate member 6a is irradiated with an electron beam to perform an
electron beam irradiation process of forming a resin cross-linked composition.
For example, first, as shown in FIG. 10B, a first mask M1 covering a portion of the acoustic
matching plate member 6a and having an opening in a portion corresponding to the layer 4a of
the peripheral portion 4 of the acoustic matching layer 66. Is disposed on the acoustic matching
plate member 6a, and for example, electron beam irradiation of electron beam intensity of
irradiation dose 400 [kGy], irradiation time 1 [h], irradiation temperature 40 [° C.] is performed.
Form the layer 4a. Next, as shown in FIG. 10C, the second mask M2 covering a portion of the
acoustic matching plate member 6a and having an opening in a portion corresponding to the
layer 4b of the peripheral portion 4 of the acoustic matching layer 66 is acoustically The layer of
the peripheral portion 4 is disposed on the alignment plate member 6a, for example, with
electron beam irradiation of an electron beam intensity of irradiation dose 600 [kGy], irradiation
time 1 [h], irradiation temperature 40 [° C] Form 4b. Next, as shown in FIG. 10D, the third mask
M3 covering a portion of the acoustic matching plate member 6a and having an opening in a
portion corresponding to the layer 4c of the peripheral portion 4 of the acoustic matching layer
66 is acoustically The layer of the peripheral portion 4 is disposed on the alignment plate
member 6a, for example, by irradiating an electron beam having an irradiation dose of 800 [kGy],
an irradiation time of 1 [h] and an irradiation temperature of 40 [° C]. Form 4c. The acoustic
matching layer 66 can be manufactured by such a three-step electron beam irradiation process.
[0082]
When manufacturing the acoustic matching layer 66, the first mask is repeated so that the
electron beam irradiation is repeated while the mask is arranged to cover a part of the acoustic
matching plate member 6a every time the mask arrangement is switched. It carried out using
three masks, M1, the 2nd mask M2, and the 3rd mask M3. However, the method of
manufacturing the acoustic matching layer 66 in which the crosslink density is different for each
portion of the resin crosslink composition uses three masks (the first mask M1, the second mask
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M2, and the third mask M3) to produce electron beams. It does not restrict to performing by the
electron beam irradiation process of three steps which switched the arrangement | positioning to
irradiate. For example, similarly to the production of the acoustic lens 9, each portion of the resin
crosslinked composition is obtained by one electron beam irradiation step using one mask (M4 to
M7) shown in FIGS. 8 (a) to 8 (d). Acoustic matching layers 66 with different crosslink densities.
[0083]
Similar to the acoustic lens 9, such an acoustic matching layer 66 has a small ultrasonic wave
propagation loss and a good ultrasonic wave transmission rate, so the technology related to the
ultrasonic probe and the ultrasonic image diagnostic apparatus is improved. It can be done.
[0084]
In the present embodiment, the crosslink density of the resin crosslink composition is adjusted
such that the propagation speed of the ultrasonic wave increases as it is separated from the
center side of the acoustic matching layer in the direction intersecting the thickness direction.
Although the acoustic matching layer 66 has been described, it is not limited thereto.
For example, the cross-linking density of the resin cross-linking composition is adjusted in the
thickness direction of the acoustic matching layer and in the propagation direction of the
ultrasonic wave, and the acoustic impedance decreases as it approaches the acoustic lens 9 from
the piezoelectric element layer 5 side. (A configuration in which the propagation speed of the
ultrasonic wave increases as going from the acoustic lens 9 side to the piezoelectric element
layer 5) may be adopted. In this case, the cross-link density of the resin cross-linked composition
can be adjusted in the thickness direction of the acoustic matching layer (the propagation
direction of the ultrasonic waves) by performing electron beam irradiation from the direction
perpendicular to the thickness direction of the acoustic matching layer. Specifically, the acoustic
matching layer in this case is formed with a predetermined width (for example, the same width)
in the thickness direction of the acoustic matching layer along the Z-axis direction (see FIG. 9),
and is divided parallel to the XY plane The cross-link density of the resin cross-linked
composition is adjusted so that the propagation speed of the ultrasonic wave increases as going
from the acoustic lens 9 side to the piezoelectric element layer 5.
[0085]
The application of the present invention is not limited to the above-described embodiment, and
can be appropriately changed without departing from the spirit of the present invention.
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[0086]
Reference Signs List 1 ultrasonic probe 1a ultrasonic probe 5 piezoelectric element layer
(piezoelectric element portion) 6 acoustic matching layer 66 acoustic matching layer 7 central
portion 8 peripheral portion 8a to 8c layer 9 acoustic lens 9a lens plate member 100 ultrasonic
wave Diagnostic imaging device M1 to M7 mask
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