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JP2011166399

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DESCRIPTION JP2011166399
An acoustic lens capable of focusing high frequency ultrasonic waves with low loss, an ultrasonic
probe having the acoustic lens, and an ultrasonic diagnostic apparatus having the ultrasonic
probe are provided. A first lens body having a central portion thinner than that of a peripheral
portion and having one surface concave is formed of a material whose ultrasonic wave
propagation speed is slower than that of the first lens body. The second lens body having a
thickness greater than that of the peripheral portion, one surface being a convex surface, and
disposed between the concave and convex surfaces facing each other, the concave surface of the
first lens body and the convex surface of the second lens body being ultrasonic waves An
acoustic lens characterized by being joined to a structure that suppresses reflection of the lens.
[Selected figure] Figure 3
Acoustic lens, ultrasonic probe, and ultrasonic diagnostic apparatus
[0001]
The present invention relates to an acoustic lens, an ultrasound probe, and an ultrasound
diagnostic apparatus.
[0002]
An ultrasonic diagnostic apparatus is a medical imaging apparatus that obtains a tomogram of
soft tissue in a living body from the body surface in a minimally invasive manner by an ultrasonic
pulse reflection method.
03-05-2019
1
Compared with other medical imaging devices, this ultrasound diagnostic device has features
such as small size, low cost, high safety with no exposure to X-rays, and the ability to perform
blood flow imaging by applying the Doppler effect. There is. 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]
An ultrasonic probe used for such a medical ultrasonic diagnostic apparatus generally uses a
piezoelectric element made of lead zirconate titanate to transmit and receive ultrasonic waves
with high sensitivity and high resolution. used. In this case, as a vibration mode of the
transmission piezoelectric element, an array type probe in which a single type or a plurality of
probes which are single type probes are 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]
On the other hand, harmonic imaging diagnosis using harmonic signals is becoming a standard
diagnostic method because a clear diagnostic image which can not be obtained by conventional
B-mode diagnosis is obtained.
[0005]
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.
[0006]
On the other hand, an acoustic lens is used for an ultrasonic probe in order to focus the beam of
an ultrasonic wave and to improve 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.
03-05-2019
2
[0007]
Conventionally, silicone rubber is mainly used as such a material.
Since silicone rubber has a slower propagation velocity of sound waves (hereinafter also referred
to as sound velocity) than a subject (living body), the central portion of the cross-sectional shape
is formed in a convex shape, and the time for ultrasonic waves to pass through the thick central
portion Was made longer than the thinner part to focus the ultrasound.
[0008]
However, since silicone rubber has a large propagation loss of ultrasonic waves, it is difficult to
improve the receiving sensitivity of the ultrasonic probe. In particular, since the high frequency
propagation loss is large, it can be said that the material is unsuitable for harmonic imaging
using harmonic signals.
[0009]
On the other hand, polymethylpentene which is a resin material, for example, is known as a
material having a small propagation loss, but polymethylpentene has a higher speed of sound
than a subject (living body), so the center of the cross-sectional shape is formed concave. It is
necessary to make the ultrasound converge.
[0010]
However, in the concave shape, the contact with the surface of the subject (living body) is poor,
and a clear image can not be obtained.
[0011]
Therefore, the flat side of the concave acoustic lens using polymethylpentene is the biological
contact side, the concave side is the piezoelectric element side, and the concave portion is filled
with the acoustic medium made of silicone rubber so that the air layer is not interposed.
Japanese Patent Application Laid-Open Publication No. 2000-147118 discloses a method of
03-05-2019
3
[0012]
Moreover, in the conventional ultrasonic probe, although the matching layer which laminated |
stacked the layer from which an acoustic impedance differs between the piezoelectric element
and the acoustic element is provided, since an acoustic impedance differs greatly in the boundary
of each layer of a matching layer, The reflection of the ultrasonic wave is generated, which is a
cause of lowering the transmission / reception sensitivity of the ultrasonic wave.
[0013]
Therefore, an additive is added so that the content ratio changes as it is 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. An ultrasound probe provided with a matching lens has been proposed (see, for
example, Patent Document 2).
[0014]
JP-A-6-254100 JP-A-2006-263385
[0015]
However, as disclosed in Patent Document 1, when the acoustic medium is provided to fill the
concave portion of the acoustic lens, the acoustic impedance is largely different at the boundary
between the acoustic lens and the acoustic medium, so that the reflection of the ultrasonic wave
occurs. , There is a problem that the transmission and reception sensitivity of ultrasonic waves is
lowered.
[0016]
In particular, when silicone rubber is used as the acoustic medium, there is a problem that the
transmission loss of ultrasonic waves by the silicone rubber is large and the reception sensitivity
is insufficient when using high-order harmonics.
[0017]
On the other hand, in the acoustic matching lens disclosed in Patent Document 2, a convex
curved surface is provided in one of three matching layers in which an additive is added to
silicone rubber, and ultrasonic waves are converged.
03-05-2019
4
However, since a material with a low propagation loss of high frequency generally has a higher
sound velocity than the object, the ultrasonic wave can not be converged on the convex surface,
and such a configuration can not be applied when using a high frequency signal.
[0018]
The present invention has been made in view of the above problems, and is an acoustic lens
capable of converging high frequency ultrasonic waves with low loss, an ultrasonic probe having
the acoustic lens, and the ultrasonic probe. An object of the present invention is to provide an
ultrasonic diagnostic apparatus having a child.
[0019]
In order to solve the above-mentioned subject, the present invention has the following features.
[0020]
??
The first lens body having a central portion thinner than the peripheral portion and one surface
being concave, and a material whose ultrasonic wave propagation speed is slower than that of
the first lens body, and the central portion has a peripheral portion The second lens body whose
one surface is a convex surface, and the concave surface of the first lens body and the convex
surface of the second lens body are joined to a structure that suppresses the reflection of
ultrasonic waves, and are arranged An acoustic lens characterized by being
[0021]
??
The structure for suppressing the reflection of the ultrasonic wave is a structure comprising an
acoustic matching layer in which a thin film layer whose propagation speed gradually changes is
laminated between the first lens body and the second lens body. The acoustic lens as described in
03-05-2019
5
1 above.
[0022]
??
The acoustic lens according to 2 above, wherein the first lens body and the acoustic matching
layer are formed using a resin material in which an additive is added to a matrix resin forming
the second lens body.
[0023]
??
The acoustic lens as described in 2 or 3 above, wherein the acoustic matching layer is composed
of a plurality of layers having different contents of additives added to a matrix resin.
[0024]
??
In the structure for suppressing the reflection of the ultrasonic wave, at least one of the
cemented surfaces of the first lens body and the second lens body is formed with a plurality of
grooves having different widths along the direction of the sound axis. The acoustic lens as
described in 1 above, which is characterized in that
[0025]
??
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6
The acoustic lens according to any one of 1 to 5, wherein an attenuation characteristic of the
acoustic lens is 10 dB / cm or less at a frequency of 5 MHz.
[0026]
??
The shape of the acoustic lens is a rectangular solid, and the surface opposite to the concave
surface of the first lens body and the surface opposite to the convex surface of the second lens
body are both flat. The acoustic lens as described in any one of 6.
[0027]
??
7. The acoustic lens as described in 7 above, wherein the concave surface of the first lens body
and the convex surface of the second lens body are provided on two opposing surfaces of the
rectangular parallelepiped.
[0028]
??
In the ultrasonic probe for performing at least one of transmission of ultrasonic waves toward
the subject and reception of reflected waves of ultrasonic waves from the subject, the acoustic
lens according to any one of 1 to 8 above An ultrasound probe comprising: transmitting and
receiving ultrasound waves via the acoustic lens; and transmitting or receiving ultrasound waves.
[0029]
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7
??? An ultrasonic diagnostic apparatus for transmitting an ultrasonic wave to a subject and
generating an image in accordance with a reflected wave of the ultrasonic wave received from
the subject, comprising: the ultrasonic probe according to the above 9; The ultrasound diagnostic
device that features.
[0030]
In the acoustic lens of the present invention, the thickness of the central portion is thinner than
that of the peripheral portion, and the first lens body whose one surface is concave, the thickness
of the central portion is thicker than the peripheral portion, and one surface is convex And a
second lens body, and disposed between the opposing concave and convex surfaces so as to be
bonded to a structure that suppresses the reflection of ultrasonic waves.
[0031]
The second lens body is formed of a material having a slower ultrasonic wave propagation speed
than the first lens body, and the acoustic matching layer has an ultrasonic wave propagation
speed and an acoustic impedance between the first lens body and the second lens body. It is
formed to change monotonously between the two.
In this way, the reflection of ultrasonic waves between the first lens body and the second lens
body is small, and high-frequency ultrasonic waves with low loss can be converged.
[0032]
Therefore, it is possible to provide an acoustic lens capable of focusing high frequency ultrasonic
waves with low loss, an ultrasonic probe having the acoustic lens, and an ultrasonic diagnostic
apparatus having the ultrasonic probe.
[0033]
It is a perspective view of acoustic lens 7 of a 1st embodiment.
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8
FIG. 7 is a partially enlarged view of the acoustic matching layer 8 of the acoustic lens 7; FIG. 5 is
a cross-sectional view of a plane orthogonal to the Y axis of the acoustic lens 7; It is a graph
which shows the distance of Z-axis direction, and the relationship of acoustic impedance. It is a
graph which shows the distance of Z-axis direction, and the relationship of sound speed. It is an
explanatory view explaining an example of a manufacturing method of an acoustic lens of a 1st
embodiment. It is sectional drawing which shows the structure of the head part of the ultrasound
probe of 1st Embodiment. It is a figure showing the appearance composition of the ultrasonic
diagnostic equipment in an embodiment. It is a block diagram which shows the electric
constitution of the ultrasound diagnosing device in embodiment. It is sectional drawing of the
acoustic lens 7 of 2nd Embodiment.
[0034]
Hereinafter, one embodiment according to the present invention will be described based on the
drawings, but the present invention is not limited to the embodiment. In addition, the structure
which attached | subjected the same code | symbol in each figure shows that it is the same
structure, and abbreviate | omits the description.
[0035]
FIG. 1 is a perspective view of the acoustic lens 7 according to the first embodiment, and FIG. 2 is
a partially enlarged view of the acoustic matching layer 8 of the acoustic lens 7.
[0036]
The following description will be made based on the coordinate axes indicated by X, Y, and Z in
the drawing.
The X direction is the elevation direction (the direction in which dicing is performed) of the
ultrasonic probe 1 (not shown in FIG. 1) joining the acoustic lens 7, and the Y direction is the
longitudinal direction of the acoustic lens 7, the Z axis positive The direction is the direction in
which the ultrasound is transmitted.
[0037]
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9
The external appearance of the acoustic lens 7 of the present embodiment is a rectangular
parallelepiped as shown in FIG. The surface on the Z-axis negative direction side orthogonal to
the Z-axis on the opposite side to the concave surface of the first lens body 21 is a flat surface
that is joined to a piezoelectric element (not shown). Further, the surface on the Z-axis positive
direction side orthogonal to the Z-axis on the opposite side of the convex surface of the second
lens body 20 is a flat surface that is in contact with the not-shown object.
[0038]
As described above, since the surface in contact with the subject is flat, the contact with the
surface of the subject is good and the subject and the acoustic lens 7 can be easily brought into
close contact with each other.
[0039]
In the first embodiment, an example in which the acoustic matching layer 8 is used as a structure
for suppressing the reflection of ultrasonic waves according to the present invention will be
described.
In the acoustic lens 7, the thickness of the central part is thinner than that of the peripheral part,
and the first lens body 21 whose one surface is concave and the thickness of the central part is
thicker than the peripheral part, and one surface is convex It comprises the second lens body 20
and the acoustic matching layer 8 in which the concave and convex surfaces facing each other
are joined as shown in FIG.
[0040]
The second lens body 20 is formed of a material having a propagation velocity of ultrasonic
waves (hereinafter also referred to as sound velocity) lower than that of the first lens body 21.
[0041]
Further, in the present embodiment, each of the first lens body 21 and the second lens body 20
is formed of a material having a propagation loss of ultrasonic waves with a frequency of 5 MHz
of 10 dB / cm or less.
03-05-2019
10
[0042]
As a material having a propagation loss of 10 dB / cm or less of ultrasonic waves at a frequency
of 5 MHz, for example, polymers or copolymers of polyethylpentene, styrene, polystyrene,
polymethyl methacrylate, polycarbonate, polypropylene and the like can be used.
[0043]
For example, in the first lens body 21, a resin liquid obtained by adding lipophilic zinc oxide
nanoparticles at a mass ratio of 93.7% to styrene having a mass ratio of 5.8% and divinylbenzene
having a mass ratio of 0.4% is heat-treated. It can be formed by polymerization.
The second lens body 20 can be formed of a copolymer obtained by crosslinking styrene and
divinylbenzene at a mass ratio of 95: 5.
[0044]
In this example, the speed of sound of the material forming the first lens body 21 is 3600 m / s,
the speed of sound of the material forming the second lens body 20 is 2350 m / s, and the
second lens body 20 is closer to the first lens body 21. It is made of a material with a slow sound
velocity.
[0045]
Further, in this example, the acoustic impedance of the material forming the first lens body 21 is
22.0 Pa и s и m <?1>, and the acoustic impedance of the material forming the second lens body
20 is 2.5 Pa и s иии It is m <-1>.
[0046]
The acoustic impedance of the piezoelectric element is generally about 24 to 36 Pa и s и m <?1>,
and if the acoustic impedance of the first lens body 21 to be joined is a value close to that as in
this example, It is possible to suppress the reflection of sound waves.
Further, the acoustic impedance of the human body which is the subject is about 1.8 Pa и s и m
<?1>, and the acoustic impedance of the second lens body 20 in contact is set to a similar value
03-05-2019
11
as in this example. It is possible to suppress the reflection of ultrasonic waves generated at the
contact surface.
[0047]
The acoustic matching layer 8 is provided to suppress reflection of ultrasonic waves generated at
the boundary between the first lens body 21 and the second lens body 20 having different
acoustic impedances, and in the present embodiment, the enlargement of FIG. As shown in the
figure, it comprises six layers 8a, 8b, 8c, 8d, 8e and 8f.
[0048]
As described above, since the acoustic impedances of the materials constituting the first lens
body 21 and the second lens body 20 are largely different, six layers are provided in this manner,
and the propagation velocity (sound velocity) of ultrasonic waves and the acoustic impedance Is
made to change monotonously between the first lens body 21 and the second lens body 20.
[0049]
[0050]
In the example of FIG. 2, each layer of the acoustic matching layer 8 is formed of a resin material
having a low acoustic impedance and a low acoustic velocity as the distance from the first lens
body 21 increases, and the acoustic impedance and the acoustic velocity of the second lens body
20 It is configured to approach.
Specifically, as shown in Table 1, the acoustic impedance is 22.0 Pa и s и m <?1> of the first lens
body 21, 18.9 Pa и s и m <?1> of the layer 8a,. The value decreases monotonously such as 4.2 Pa
и s и m <?1> of the layer 8 f and 2.5 Pa и s и m <?1> of the second lens body 20.
[0051]
Also, the velocity of sound decreases monotonously, such as 3600 m / s of the first lens body 21,
3340 m / s of the layer 8a, 2410 m / s of the layer 8f, 2350 m / s of the second lens body 20,
and so on. There is.
03-05-2019
12
[0052]
In this way, changes in the velocity of sound and the acoustic impedance between the layers are
reduced, and the reflection of ultrasonic waves generated at the boundary can be suppressed.
[0053]
The layers 8a to 8f can be formed by thermally polymerizing a resin solution in which the ratio
of adding lipophilic zinc oxide nanoparticles to styrene and divinylbenzene is changed for each
layer, as described in detail later.
The thickness of each layer is about several ?m.
[0054]
The number of layers of the acoustic matching layer 8 is not limited to six, and may be more than
two, and may be one if the difference in acoustic impedance between the first lens body 21 and
the second lens body 20 is small. .
[0055]
The principle by which the acoustic lens 7 of the present invention converges an ultrasonic wave
will be described with reference to FIGS. 3, 4 and 5.
3 is a cross-sectional view of a plane orthogonal to the Y axis of the acoustic lens 7, FIG. 4 is a
graph showing the relationship between the distance in the Z axis direction and the acoustic
impedance, and FIG. 5 is the relationship between the distance in the Z axis direction and the
velocity of sound. FIG.
[0056]
Arrow S1 of FIG. 3 indicates an ultrasonic wave traveling at the center of the width of the
acoustic lens 7 in the X-axis direction, and arrow S2 indicates an ultrasonic wave traveling at the
peripheral portion of the width of the acoustic lens 7 in the X-axis direction. There is.
03-05-2019
13
Also, the surface 20a is in contact with the subject.
[0057]
In FIG. 3, 21a is a surface to be bonded to the piezoelectric element, and 20a is a surface to be in
contact with the object.
Z1 is the distance from the surface 21a of the position where the advancing ultrasonic wave as
shown by the arrow S1 reaches the acoustic matching layer 8, and the ultrasonic wave advancing
as shown by the arrow S2 is Z2 is the acoustic matching layer 8 It is the distance from the
surface 21a of the position to reach.
[0058]
In the center of the acoustic lens 7 shown by S1 in FIG. 4, the surface 21a to Z1 is the acoustic
impedance R1 of the first lens body 21, and in the section corresponding to the acoustic
matching layer 8, it gradually decreases according to the distance. The acoustic impedance R2 of
the two-lens body 20 is obtained.
Further, in the peripheral portion shown by S2, the surface 21a to Z2 is the acoustic impedance
R1 of the first lens body 21, and in the section corresponding to the acoustic matching layer 8, it
gradually decreases according to the distance. Becomes the acoustic impedance R2.
Although FIG. 4 illustrates that the acoustic impedance is continuously reduced, in actuality, the
acoustic impedance differs for each layer.
[0059]
Similarly, at the center of the acoustic lens 7 shown by S1 in FIG. 5, the surface 21a to Z1 is the
sound velocity V1 of the first lens body 21, and in the section corresponding to the acoustic
03-05-2019
14
matching layer 8, it gradually decreases according to the distance. The sound velocity V2 of the
second lens body 20 is obtained.
Further, in the peripheral portion shown by S2, the surface 21a to Z2 is the sound velocity V1 of
the first lens body 21, and in the section corresponding to the acoustic matching layer 8, it
gradually decreases according to the distance. The sound velocity is V2.
Although FIG. 5 illustrates that the sound velocity is continuously reduced, in reality, the velocity
is different for each layer.
[0060]
As described above, the ultrasonic wave indicated by S2 traveling in the peripheral portion has a
shorter distance traveling in the region of sound velocity V2 than the ultrasonic wave indicated
in S1 traveling in the center and a long distance traveling in the region of sound velocity V1
faster than the sound velocity V2 At the same time, the object coming into contact with the
surface 20a is reached earlier than the ultrasonic wave shown by S1 incident on the surface 21a.
[0061]
Since the ultrasonic wave traveling in the peripheral portion shown by S2 is incident on the
subject earlier than the ultrasonic wave traveling in the center, it travels a longer distance by the
time difference and travels in the central portion at a distance f It converges with the ultrasonic
wave shown by.
[0062]
The focal length can be set to a desired value by changing the sound velocity difference between
the first lens body 21 and the second lens body 20, and the curvatures of the concave and
convex surfaces.
[0063]
As described above, the acoustic lens 7 of the present embodiment is configured such that the
time it travels from the surface 21a to the surface 20a differs according to the position where the
ultrasonic wave is incident on the surface 21a, and the ultrasonic wave emitted from the surface
20a is predetermined. It converges to the distance of
03-05-2019
15
As a result, even if a resin material having a sound velocity faster than that of the subject is used,
it is possible to make the surface in contact with the subject a planar shape that easily adheres to
the subject.
[0064]
Further, since the acoustic lens 7 of the present embodiment is formed of a resin material having
a frequency of 5 MHz and 10 dB / cm or less, the attenuation of the harmonic signal is small, and
an array type ultrasonic probe using the harmonic signal is used. It is suitable.
[0065]
Furthermore, since it is formed of a resin material, the surface in contact with the subject is less
likely to be worn away.
Therefore, like the acoustic lens made of silicone rubber, the surface of the acoustic lens
gradually wears off when the jelly-like substance applied when using the ultrasonic probe is
wiped after use, and the focus position is adjusted from the original design It is hard to raise the
problem that it disappears.
[0066]
In addition, since the resin material is hard to transmit gas and liquid, the disinfecting gas or
liquid may intrude from the surface of the acoustic lens 7 in contact with the object, and the
characteristics of the ultrasonic probe may be degraded. Few.
[0067]
In the present embodiment, the surface 20a is a surface to be bonded to a piezoelectric element,
and the surface 21a is a surface to be in contact with an object. However, the surface 21a is a
surface to be bonded to a piezoelectric element. Even if it is used, the ultrasonic waves can be
converged.
[0068]
Next, a method of manufacturing the acoustic lens of the first embodiment will be described.
03-05-2019
16
[0069]
FIG. 6 is an explanatory view illustrating an example of a method of manufacturing the acoustic
lens according to the first embodiment.
[0070]
<Production Process of Resin Base> FIG. 6A is an example of the resin base 25 forming the
second lens body 20. FIG.
The resin base 25 is in the shape of a bowl in which one surface is convex as shown in FIG. 3 (a).
There is no particular limitation on the size of the resin base material, but as an example, the
width W1 = 10 mm, the depth L = 100 mm, the height H1 = 5 mm, and the convex curvature
radius 10 mm.
[0071]
Although various resin materials can be used for the material which forms the resin base
material 25, As for the attenuation characteristic of an ultrasonic wave, the resin material of 2 dB
/ cm or less is preferable at a frequency of 5 MHz.
For example, polymers or copolymers of methyl pentene, styrene, methyl methacrylate,
carbonate, propylene and the like can be used.
[0072]
The resin base material 25 is produced, for example, by casting a resin material in a mold.
[0073]
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17
<Lamination Step> After applying resin liquid 1 to which the additive is added to the convex
surface of the resin base 25 at a ratio that an acoustic impedance higher than the resin base 25
and a predetermined sound velocity can be obtained to a predetermined thickness w, Heat cure.
Next, the resin solution 2 to which the additive is added is applied so as to have a predetermined
thickness w at a rate at which a predetermined faster sound velocity can be obtained, and then
heat curing is performed.
As described above, the application of the resin solution and the heat curing are sequentially
repeated to form the layers 8 f to 8 a constituting the acoustic matching layer 8 in order.
Finally, the resin liquid 7 is applied and heat curing is repeated until the thickness reaches a
predetermined thickness, as shown in FIG. 6B, a portion to be the first lens body 21 is formed.
[0074]
Examples of the additive added to the resin material to change the sound velocity of the resin
material of the base material include zinc oxide, aluminum, aluminum oxide, duralumin, titanium,
silicon nitride, boron carbide, molybdenum and the like.
These additives are preferably used in the form of a powder sufficiently small with respect to the
wavelength so as to be uniformly added to the resin material of the base material and not to
cause acoustic mismatch at the interface between the base material and the additive. The
diameter is preferably 10 ?m or less, more preferably 0.5 ?m or less.
[0075]
Cutting and Polishing Process As shown in FIG. 6B, the surface and side surfaces of the first lens
body 21 are cut and cut so as to form a rectangular solid having a width W2 and a height H3 in
which resin materials are sequentially laminated. The surface is polished to obtain an acoustic
lens 7 as shown in FIG. 6 (c).
[0076]
As a cutting method, a dicing saw, a laser cutter, an ultrasonic cutter, a high pressure water
03-05-2019
18
cutter or the like can be used.
[0077]
FIG. 7 is a cross-sectional view showing the configuration of the head portion of the ultrasonic
probe of the first embodiment.
[0078]
In the present embodiment, an example in which the present invention is applied to a single type
ultrasonic probe that performs transmission and reception with a single piezoelectric element
will be described, but the present invention is not particularly limited and a transmission
piezoelectric element and a reception piezoelectric element Can also be applied to an array-type
ultrasound probe in which the operations at the time of transmission and reception of ultrasound
are separated.
[0079]
The following description will be made based on the coordinate axes indicated by X, Y, and Z in
the drawing.
The X direction is the elevation direction of the ultrasound probe 1 (the direction in which dicing
is performed), and the Z-axis positive direction is the direction in which ultrasound is transmitted.
The Z-axis direction is the stacking direction.
[0080]
The ultrasound probe 1 shown in FIG. 7 is laminated on the backing material 5 in the order of
the first electrode 15, the transmission / reception element layer 2, the second electrode 14, and
the acoustic lens 7.
[0081]
Hereafter, each component is demonstrated in order of lamination | stacking.
03-05-2019
19
[0082]
(Transmission / reception element layer) The transmission / reception element layer 2 is a
piezoelectric element made of a piezoelectric material such as lead zirconate titanate, and
includes the second electrode 14 and the first electrode 15 on both sides facing each other in the
thickness direction.
The thickness of the transmission / reception element layer 2 is about 320 ?m.
[0083]
The second electrode 14 and the first electrode 15 are connected to a cable 33 (not shown) in
FIG. 4 by a connector (not shown), and connected to the transmission circuit 42 via the cable 33.
When an electric signal is input to the second electrode 14 and the first electrode 15, the
piezoelectric element vibrates, and ultrasonic waves are transmitted from the transmitting /
receiving element layer 2 in the positive Z-axis direction.
[0084]
The second electrode 14 and the first electrode 15 are formed on both surfaces of the
transmission / reception element layer 2 using a metal material such as gold, silver, or aluminum
by using a vapor deposition method or a photolithography method.
[0085]
The second electrode 14 and the first electrode 15 are also connected to the receiving circuit 43
via a cable 33 (not shown) in FIG.
[0086]
When the transmitting / receiving element layer 2 receives and vibrates the reflected wave of the
ultrasonic wave reflected by the object, an electrical signal is generated between the second
03-05-2019
20
electrode 14 and the first electrode 15 according to the reflected wave.
An electrical signal generated between the second electrode 14 and the first electrode 15 is
received by the receiving circuit 43 via the cable 33 and is imaged by the image processing unit
44.
[0087]
The transmitting / receiving element layer 2 in which the second electrode 14 and the first
electrode 15 are formed is adhered on the backing material 5 by an adhesive and laminated as
shown in FIG.
Further, if necessary, an intermediate layer having an intermediate acoustic impedance may be
provided between the transmission / reception element layer 2 and the acoustic lens 7.
[0088]
After lamination, dicing is performed from the transmission / reception element layer 2 in the
direction opposite to the ultrasonic radiation direction, and dicing is further performed from the
adhesive layer of the backing material 5 and the first electrode 15 to a depth of 100 ?m in the
negative Z-axis direction.
After filling the filler made of silicon resin or the like in the groove portion made by dicing, the
acoustic lens 7 is adhered to the uppermost layer.
[0089]
Alternatively, dicing may be performed after laminating up to the acoustic lens 7, and after filling
the groove with silicon resin or the like, a surface protection layer made of the same material as
the upper part of the acoustic lens 7 may be adhered.
[0090]
The acoustic lens 7 converges the ultrasonic waves transmitted from the transmission / reception
03-05-2019
21
element layer 2 to a predetermined distance.
[0091]
(Each Configuration and Operation of Ultrasonic Diagnostic Apparatus and Ultrasonic Probe) FIG.
8 is a view showing an appearance configuration of the ultrasonic diagnostic apparatus in the
embodiment.
FIG. 9 is a block diagram showing an electrical configuration of the ultrasonic diagnostic
apparatus in the embodiment.
[0092]
The ultrasonic diagnostic apparatus 100 transmits an ultrasonic wave (ultrasound signal) to a
subject such as a biological body (not shown), and the ultrasonic wave reflected by the received
subject (echo, ultrasonic signal) The internal state in the sample is imaged as an ultrasonic image
and displayed on the display unit 45.
[0093]
The ultrasound probe 1 transmits ultrasound (ultrasound signal) to a subject, and receives a
reflected wave of ultrasound reflected by the subject.
As shown in FIG. 8, the ultrasound probe 1 is connected to the ultrasound diagnostic apparatus
main body 31 via a cable 33, and is electrically connected to the transmission circuit 42 and the
reception circuit 43.
[0094]
The transmission circuit 42 transmits an electrical signal to the ultrasound probe 1 via the cable
33 according to a command from the control unit 46, and causes the ultrasound probe 1 to
transmit ultrasound to the subject.
[0095]
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The receiving circuit 43 receives an electric signal corresponding to the reflected wave of the
ultrasonic wave from the inside of the subject from the ultrasonic probe 1 through the cable 33
according to the command of the control unit 46.
[0096]
The image processing unit 44 images the internal state inside the subject as an ultrasound image
based on the electrical signal received by the receiving circuit 43 according to an instruction
from the control unit 46.
[0097]
The display unit 45 includes a liquid crystal panel or the like, and displays an ultrasonic image
imaged by the image processing unit 44 according to an instruction from the control unit 46.
[0098]
The operation input unit 41 includes 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 the
subject.
[0099]
The control unit 46 includes a CPU, a memory, and the like, and controls the respective units of
the ultrasonic diagnostic apparatus 100 according to a procedure programmed based on the
input of the operation input unit 41.
[0100]
Hereinafter, the present invention will be described by way of examples, but the present
invention is not limited to these examples.
[0101]
[Example] (Production of Acoustic Lens) In the example, the width W = 7 mm in the X-axis
direction, the height H = 7 mm in the Z-axis direction, and the length L = 100 mm in the Y-axis
direction A rectangular solid acoustic lens with a focal length f = 40 mm was produced by the
procedure described in FIG.
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The thickness of each of the layers 8a to 8f is 3 ?m.
[0102]
<Production Process of Resin Base> A copolymer obtained by crosslinking styrene and
divinylbenzene at a mass ratio of 95: 5 is used as a material and cast in a mold, and L = 100 mm
as shown in FIG. A bowl-shaped resin substrate 25 of W1 = 10 mm and H1 = 5 mm was
produced.
When the sound velocity V1 and the acoustic impedance R1 of the resin base material 25 were
measured, they were 3600 m / sec and 22.0 Ps и s и m <-1>, respectively.
[0103]
<Resin Liquid Production Step> Resin Liquids 1 to 7 were prepared by mixing lipophilic zinc
oxide nanoparticles of an additive and a thermal polymerization initiator with styrene and
divinylbenzene at a mass ratio in Table 2.
[0104]
[0105]
The mass ratio of the additives contained in the resin liquids 1 to 7 shown in Table 2 is such that
the volume ratio P of adding the additive to the resin material of the base material is determined
so that the acoustic impedances Ra to R2 of Table 1 can be obtained. , Determined in terms of
mass ratio.
[0106]
The zinc oxide in Table 2 is lipophilic zinc oxide nanoparticles (VP AdNano Z805 manufactured
by Degussa), and has an average particle diameter of 250 nm.
Further, azobisisobutyronitrile was used as a thermal polymerization initiator.
03-05-2019
24
[0107]
<Lamination Step> Resin solution 1 was applied to the convex surface of the resin base 25 by dip
coating to a thickness of 3 ?m, immediately followed by high-temperature drying and crosslinking to form a layer 8a.
Similarly, coating and heat curing were performed in the same procedure for resin liquids 2 to 6
to form layers 8 b to 8 f.
[0108]
The second lens body 20 repeated application and heat curing of the resin liquid 7 on the layer 8
f to have a shape as shown in FIG. 6 (b).
The coating thickness was up to 6 mm.
[0109]
<Cutting and Polishing Step> The surface and the side of the first lens body 21 are cut so that the
laminate obtained in the laminating step becomes a rectangular solid having a width W2 = 7 mm
and a height H3 = 7 mm, and the cut surface is polished To obtain an acoustic lens 7 as shown in
FIG. 6 (c).
[0110]
(Production of Ultrasonic Probe) The prototyped ultrasonic probe 1 was produced as follows.
[0111]
The transmitting / receiving element layer 2 was produced by lapping a sheet of lead zirconate
titanate as a material with a length of 10 mm in the X direction, a length of 55 mm in the Y
direction, and a length (thickness) of 320 ?m in the Z direction.
03-05-2019
25
[0112]
Next, gold was vacuum-deposited on both sides of the transmission / reception element layer 2
to fabricate a 0.3 ?m thick second electrode 14 and a first electrode 15.
[0113]
The transmitting / receiving element layer 2 in which the second electrode 14 and the first
electrode 15 are formed is adhered on the backing material 5 by an adhesive and laminated as
shown in FIG.
After lamination, dicing was performed from the transmission / reception element layer 2 in the
negative Z-axis direction, and dicing was further performed from the adhesive layer of the
backing material and the fourth electrode to a depth of 100 ?m in the negative Z-axis direction.
[0114]
Finally, the acoustic lens 7 was adhered to the uppermost layer, and five ultrasonic probes 1 of
Example and Example 2 were produced.
[0115]
Comparative Example (Preparation of Acoustic Lens) An acoustic lens having a convex lens
surface with a width W of 6 mm in the X-axis direction, a width L of 100 mm in the Y-axis
direction, and a curvature radius of 10 mm in the Z-axis direction is 40 mm. And silicone rubber
were prepared.
The maximum width H in the Z-axis direction is 460 ?m.
[0116]
(Production of Ultrasonic Probe) Each layer was laminated in the same procedure as in the
example, and finally an acoustic lens made of silicone rubber was adhered to the top layer, and
five ultrasonic probes 1 of the comparative example were produced. .
03-05-2019
26
[0117]
[Evaluation Method] The focal length and the attenuation amount of each of the ultrasonic
probes of the example and the comparative example were measured, and the average value was
obtained.
The focal length was measured by an underwater hydrophone method, and the attenuation was
measured by a single-around method.
[0118]
In addition, after the surface of the acoustic lens of the example and the comparative example
was subjected to a friction test of 500 times by applying a load of 50 g to a non-woven wiper
(BEMCOT M-3II (trade name), manufactured by Asahi Kasei Co., Ltd.) Was measured.
[0119]
[result]
[0120]
[0121]
The focal lengths of the example and the comparative example before the friction test were both
40 mm as shown in Table 3.
[0122]
As shown in Table 3, the attenuation is 1.2 dB at a frequency of 5 MHz, 8.3 dB at a frequency of
15 MHz at the center of the ultrasound probe of the embodiment, 2.3 dB at a frequency of 5
MHz at the end, and 12 at a frequency of 15 MHz. .1 dB.
[0123]
On the other hand, in the comparative example, as shown in Table 3, the attenuation is 4.1 dB at
a frequency of 5 MHz, 21 and 3 dB at a frequency of 15 MHz, and about 3 dB at a frequency of 5
03-05-2019
27
MHz and 9 dB at a frequency of 15 MHz. There is.
Thus, in the present invention, it has been confirmed that an attenuation characteristic of 10 dB /
cm or less can be obtained at a frequency of 5 MHz.
In addition, it has been confirmed that an acoustic lens with less propagation loss can be
obtained at the same focal length.
[0124]
The focal length of the example after the friction test was not changed as shown in Table 3, but
the focal length of the comparative example was changed to 12 mm far.
From this, it can be confirmed that the acoustic lens of the present invention is excellent in
abrasion resistance and high in durability.
[0125]
Next, as a structure for suppressing the reflection of ultrasonic waves according to the present
invention, at least one of the cemented surfaces of the first lens body 21 and the second lens
body 20 has a plurality of grooves having different widths along the sound axis direction. An
example of formation will be described.
[0126]
FIG. 10 is a cross-sectional view of the acoustic lens 7 of the second embodiment.
[0127]
In the example of FIG. 10A, the grooves 71 and 72 are provided on the concave surface of the
opposing first lens body 21 and the convex surface of the second lens body 20, respectively, and
the grooves 71 and 72 are joined to each other.
[0128]
In this way, the acoustic impedance between the first lens body 21 and the second lens body 20
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can be continuously changed in the Z-axis direction from the first lens body 21 toward the
second lens body 20.
[0129]
FIG. 10 (b) is a modification of FIG. 10 (a), in which grooves 71 and 72 are provided on the
concave surface of the opposing first lens body 21 and the convex surface of the second lens
body 20, respectively. The acoustic matching material 73 is filled and joined between them.
[0130]
In the example of FIG. 10C, the groove 71 is provided only on the convex surface of the opposing
second lens body 20, and the groove is not provided on the concave surface of the first lens body
21.
In this example, the acoustic matching material 73 is filled between the concave surface of the
first lens body 21 and the groove 71 and joined.
[0131]
The acoustic matching material 73 is formed of a material having an acoustic impedance
between the first lens body 21 and the second lens body 20.
For example, a resin liquid in which the ratio of additives as described in Table 2 is changed may
be used.
[0132]
Similarly in the examples of FIGS. 10B and 10C, the acoustic impedance between the first lens
body 21 and the second lens body 20 is directed from the first lens body 21 to the second lens
body 20 in the Z-axis direction. Can change continuously.
[0133]
As described above, according to the present invention, an acoustic lens capable of converging
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high frequency ultrasonic waves with low loss, an ultrasonic probe having the acoustic lens, and
an ultrasonic wave having the ultrasonic probe A diagnostic device can be provided.
[0134]
DESCRIPTION OF SYMBOLS 1 ultrasonic probe 2 transmitting / receiving element 5 backing
material 7 acoustic lens 8 acoustic matching layer 14 2nd electrode 15 1st electrode 20 2nd lens
body 21 1st lens body 25 resin base material 31 ultrasonic diagnostic apparatus main body 33
cable 41 Operation input unit 42 Transmission circuit 43 Reception circuit 44 Image processing
unit 45 Display unit 46 Control unit 100 Ultrasonic diagnostic apparatus
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