close

Вход

Забыли?

вход по аккаунту

?

JP2010252065

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2010252065
The present invention provides an acoustic lens which has excellent adhesion to a subject and
which has a small propagation loss of ultrasonic waves, an ultrasonic probe having the acoustic
lens, and an ultrasonic diagnostic apparatus having the ultrasonic probe. According to a position
where an ultrasonic wave is incident on the first lens surface, the ultrasonic wave is specified by
changing the propagation speed of the ultrasonic wave while traveling from the first lens surface
to the second lens surface. An acoustic lens characterized in that it converges to a distance of.
[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.
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
03-05-2019
1
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]
Harmonic imaging has many advantages as described below compared to the fundamental wave.
[0006]
1.
The smaller side lobe level results in better S / N ratio and better contrast resolution.
[0007]
2.
03-05-2019
2
The higher the frequency, the narrower the beam width and the better the lateral resolution.
[0008]
3. The sound pressure is small at short distances and there is little fluctuation in sound
pressure, so multiple reflections do not occur.
[0009]
4. Attenuation beyond the focal point is similar to the fundamental wave, and it is possible to
obtain a large depth velocity compared to the ultrasonic wave that uses the frequency of the
harmonic wave as the fundamental wave.
[0010]
などである。
[0011]
As a specific structure of an array type ultrasonic probe used for harmonic imaging, an array
type in which the transmitting piezoelectric vibrator and the receiving piezoelectric vibrator are
separately provided and the operation at the time of transmitting ultrasonic wave and at the time
of receiving ultrasonic wave is separated Ultrasonic probes have been proposed.
[0012]
It is desirable that the receiving piezoelectric vibrator used for such an array-type ultrasonic
probe can receive harmonic signals with high sensitivity.
However, since the transmission / reception frequency of a piezoelectric element made of lead
zirconate titanate or the like depends on the thickness of the piezoelectric element, the
piezoelectric element needs to be processed in a smaller size as the frequency to be received
becomes higher. there were.
03-05-2019
3
[0013]
In order to solve such problems, a piezoelectric element for transmission and a sheet-like
piezoelectric element for reception are laminated or laminated in a single layer or laminated
structure of sheet-like piezoelectric ceramic, and piezoelectric elements for transmission and
reception are separated. There have been proposed methods for obtaining a high sensitivity
ultrasonic probe by separating into two and using a high sensitivity organic piezoelectric element
material for reception (see Patent Documents 1, 2 and 3).
[0014]
On the other hand, an acoustic lens is conventionally used for an ultrasound probe in order to
focus a beam of ultrasound 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.
[0015]
Conventionally, silicone rubber is mainly used as such a material.
Silicon rubber has a slower propagation velocity of sound waves (hereinafter also referred to as
sound velocity) than the object (living body), so the central portion of the cross-sectional shape is
formed in a convex shape, and the time for ultrasound to pass through the thick central portion
Was made longer than the thinner part to focus the ultrasound.
[0016]
However, since silicone rubber has a large propagation loss of ultrasonic waves, it is difficult to
improve the reception 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.
03-05-2019
4
[0017]
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.
[0018]
However, in the concave shape, there is a problem that the contact with the surface of the subject
(living body) is deteriorated.
[0019]
Therefore, there is disclosed a method of fixing a biconvex acoustic region on a concave acoustic
lens using polymethylpentene to improve the contact with the surface of a subject (living body).
(For example, refer to patent document 4)
[0020]
Patent Document 1: Japanese Patent Application Publication No. 2008-188415 Patent Document
2: International Publication No. 2007/145073 Patent Document: International Publication No.
2008/010509 Patent Document 2: Japanese Patent Application Laid-Open No. 6-254100
[0021]
However, when the biconvex acoustic region is provided on the concave acoustic lens as
disclosed in Patent Document 4, the total propagation loss of the acoustic lens is hardly improved
because the propagation loss in the acoustic region is added.
In particular, when silicone rubber is used as the acoustic region as in Patent Document 4, the
propagation loss of ultrasonic waves by the silicone rubber is large, and when using high-order
harmonics, the reception sensitivity becomes insufficient.
03-05-2019
5
[0022]
The present invention has been made in view of the above problems, and is an acoustic lens
excellent in adhesion to a subject and having a small propagation loss of ultrasonic waves, an
ultrasonic probe having the acoustic lens, and the ultrasonic waves. An object of the present
invention is to provide an ultrasonic diagnostic apparatus having a probe.
[0023]
In order to solve the above-mentioned subject, the present invention has the following features.
[0024]
1.
An acoustic lens which radiates an ultrasonic wave incident from a first lens surface from a
second lens surface and converges the ultrasonic wave to a predetermined distance, the
ultrasonic wave corresponding to a position where the ultrasonic wave is incident to the first lens
surface. An acoustic lens characterized in that the ultrasonic wave is converged to a
predetermined distance by changing the propagation speed of the ultrasonic wave while
advancing from the lens surface of 1 to the second lens surface.
[0025]
2.
The acoustic lens according to the above 1, wherein the second lens surface is a flat surface.
[0026]
3.
03-05-2019
6
The position of the ultrasonic wave incident on the first lens surface is configured such that the
propagation speed of the ultrasonic wave is increased as the distance from the center of the first
lens surface is increased. The acoustic lens as described in 2.
[0027]
4. A central portion of the rectangular parallelepiped, and two peripheral portions of the
rectangular parallelepiped disposed such that the surfaces of the same shape are in contact with
two opposing surfaces of the central portion orthogonal to the direction in which the ultrasonic
wave travels. The peripheral portion is composed of at least one layer formed in parallel with two
opposing surfaces of the central portion, and the layer is formed of a material having a higher
ultrasonic wave propagation speed as the distance from the central portion is larger. The acoustic
lens as described in any one of 1 to 3 above, characterized in that:
[0028]
5. The acoustic lens according to any one of the above 1 to 4, characterized in that it is formed
using a resin material in which an ultrasonic wave propagation speed is adjusted by adding an
additive to a matrix resin.
[0029]
6. The acoustic lens according to any one of 1 to 5, wherein an attenuation characteristic of
the acoustic lens is 2 dB / cm or less at a frequency of 5 MHz.
[0030]
7. An ultrasonic probe for transmitting an ultrasonic wave to a subject and receiving a
reflected wave of the ultrasonic wave from the subject, comprising: the acoustic lens according to
any one of 1 to 6, An ultrasonic probe characterized by transmitting and receiving ultrasonic
waves through an acoustic lens.
03-05-2019
7
[0031]
8. An ultrasonic diagnostic apparatus for transmitting an ultrasonic wave toward 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 7; The ultrasound diagnostic
device that features.
[0032]
According to the present invention, the ultrasonic wave is changed by changing the propagation
speed of the ultrasonic wave while traveling from the first lens surface to the second lens surface
according to the position where the ultrasonic wave is incident on the first lens surface. Is
converged to a predetermined distance, the ultrasonic waves can be converged to a
predetermined distance even if the shape of the second lens surface is flat.
[0033]
Therefore, it is possible to provide an acoustic lens which is excellent in adhesion to a subject and
has little propagation loss of ultrasonic waves, an ultrasonic probe having the acoustic lens, and
an ultrasonic diagnostic apparatus having the ultrasonic probe. it can.
[0034]
It is a perspective view of acoustic lens 7 of an embodiment.
It is explanatory drawing for demonstrating the principle on which the acoustic lens 7 of
embodiment converges an ultrasonic wave.
It is an explanatory view explaining an example of a manufacturing method of acoustic lens 7
concerning an embodiment. It is a sectional view showing the composition of the head part of the
ultrasound probe of an 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.
03-05-2019
8
[0035]
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.
[0036]
FIG. 1 is a perspective view of the acoustic lens 7 of the embodiment. FIG. 2 is an explanatory
view for explaining the principle of causing the acoustic lens 7 of the embodiment to converge
ultrasonic waves. 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), and the Z-axis positive direction is the direction in which ultrasonic waves
are transmitted.
[0037]
The external appearance of the acoustic lens 7 is a rectangular solid having a width W in the Xaxis direction, a width H in the Z-axis direction, and a width L in the Y-axis direction as shown in
FIG. Of the two opposing surfaces orthogonal to the Z-axis, the surface in the negative Z-axis
direction is the surface (first lens surface) on which the ultrasonic wave emitted from the
piezoelectric element (not shown) is incident. The surface in the positive Z-axis direction Is a
surface (second lens surface) which is in close contact with a subject (not shown) and emits
ultrasonic waves to the inside of the subject. The two opposing surfaces orthogonal to the Z-axis
are both flat.
[0038]
The acoustic lens 7 is composed of a central portion 4 and a peripheral portion 8 made of a resin
material having a higher sound velocity (hereinafter also referred to as sound velocity) than the
resin material of the central portion 4.
[0039]
03-05-2019
9
In the example of FIG. 1, the peripheral portion 8 is configured of ten layers formed in parallel
with the two surfaces of the central portion 4 of the rectangular parallelepiped, which are
opposed to each other in the X-axis direction.
That is, the layers 8a, 8b, 8c, 8d, 8e, 8g, 8h, 8i, 8j are formed on the left side of the drawing of
the central portion 4 with a width w in the X direction. , 8l, 8m, 8n, 8o, 8p, 8q, 8r, 8s, 8t are
formed with the same width w. The width of the central portion 4 in the X direction is W0, the
width of the peripheral portion 8 sandwiching the central portion 4 is W1, and the widths of the
central portion 4 and the peripheral portion 8 in the Z direction are both H.
[0040]
The layers 8a to 8j and the layers 8k to 8t of the peripheral portion 8 are formed of a resin
material having a higher sound velocity as the distance from the central portion 4 increases.
[0041]
For example, assuming that the central portion 4 is formed of a resin material of sound velocity
V1, the peripheral portion 8a and the peripheral portion 8k are formed of a resin material of
sound velocity Va faster than the sound velocity V1.
The peripheral portion 8 b and the peripheral portion 8 l are made of a resin material having a
sound velocity Vb faster than the sound velocity Va. The peripheral portion 8c and the peripheral
portion 8m are made of a resin material having a sound velocity Vc faster than the sound
velocity Vb, and the peripheral portion 8d and the peripheral region 8n are made of a resin
material having a sound velocity Vd faster than the sound velocity Vc.
[0042]
Similarly, each part of the peripheral part is configured to increase the propagation velocity of
the sound wave according to the distance from the central part, and the outermost peripheral
part 8 j and the peripheral part 8 t are the fastest among the acoustic lenses 7. It consists of resin
material of sound velocity Vj.
[0043]
03-05-2019
10
The principle on which the acoustic lens 7 of the present invention converges an ultrasonic wave
will be described with reference to FIG.
In FIG. 2, in order to simplify the description, an example in which the peripheral portions 8 are
all formed of the same material is described. The central portion 4 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. Further, it is assumed that the surface in the positive Z-axis direction of
the acoustic lens 7 is in contact with the liquid 50 of the sound velocity V0 stored in a container
(not shown).
[0044]
12 indicates a state in which the ultrasonic wave incident from the center of the central portion 4
travels through the central portion 4 and the liquid 50. Il indicates a state in which the ultrasonic
wave incident from the center of the peripheral portion 8 on the left side of the drawing travels
through the peripheral portion 8 and the liquid 50 and converges with l2 at the position of the
focal length f. x is the distance between l1 and l2 incident on the acoustic lens 7;
[0045]
Since the velocity of sound V2 of the peripheral portion 8 is faster than the velocity of sound V1
of the central portion 4, the ultrasonic waves incident from the peripheral portion 8
simultaneously enter the liquid 50 earlier than the ultrasonic waves incident from the central
portion 4 and The wavefront travels concentrically.
[0046]
The time difference t1 of passing the acoustic lens 7 between the ultrasonic wave incident from
the peripheral portion 8 and the ultrasonic wave incident from the central portion 4 can be
obtained by the following equation (1).
[0047]
[0048]
03-05-2019
11
In FIG. 2, m is a distance traveled by the ultrasonic wave incident from the peripheral portion 8
during the time difference t1.
Assuming that the sound velocity of the liquid 50 is V0, the distance m can be obtained by the
following equation (2).
[0049]
m = V0 × t1 (2) The ultrasonic wave incident from the center of the peripheral portion 8 on the
left side of the drawing travels the distance m, and then the same distance f as the ultrasonic
wave incident from the center of the central portion 4 And converge to the point q.
The focal length f can be obtained by the following equation (3) using the Pythagorean theorem.
[0050]
f = (x <2> -m <2>) / 2 m (3) When Formula (1) and Formula (2) are substituted into Formula (3),
the focal distance f is the following Formula (4) You can ask for
[0051]
[0052]
H is the width (thickness) of the acoustic lens 7 in the Z-axis direction, V1 is the speed of sound
of the central portion 4, V2 is the speed of sound of the peripheral portion 8, V0 is the speed of
sound of the liquid 50.
[0053]
Thus, the ultrasonic wave 12 traveling in the central part 4 and the ultrasonic wave 11 incident
from the peripheral part 8 can be converged at one point by the difference in the sound velocity
between the central part 4 and the peripheral part 8.
03-05-2019
12
[0054]
For example, when 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 30 mm.
In addition, the other values are the same, and when H is changed to 5 mm, the focal length f is
14.9 mm.
[0055]
As shown in FIG. 1, when the peripheral portion 8 is formed of ten layers with the central portion
4 in between, the ultrasonic waves traveling in the respective layers in parallel with the
ultrasonic waves traveling in the central portion 4 become one point. Set the speed of sound of
each layer to converge.
The sound velocity V2 of the resin material forming the peripheral portion 8 converging to the
focal length f can be obtained by the following equation (5).
[0056]
[0057]
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.
[0058]
Similarly, using Equation (5), layers 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h, 8i, 8j, and layers 8k, 8l, 8m, 8n
for focusing the ultrasonic waves at the same focal length f. The velocity of sound Va, Vb, Vc, Vd,
Ve, Vf, Vg, Vh, Vi, Vj of the resin material that forms 8o, 8p, 8q, 8r, 8s, 8t can be obtained.
[0059]
As will be described later, such resin materials having different sound speeds can be obtained by
adding an additive to the resin material as the base material.
03-05-2019
13
[0060]
Next, an example of a method of manufacturing the acoustic lens 7 will be described.
[0061]
FIG. 3 is an explanatory view illustrating an example of a method of manufacturing the acoustic
lens 7 according to the embodiment.
[0062]
<Production Process of Resin Substrate> FIG. 3A is an example of a resin substrate on which the
central portion 4 is formed.
The resin substrate is a rectangular parallelepiped having a width L, a height H1, and a depth M
as shown in FIG. 3 (a).
There is no particular limitation on the size of the resin substrate, but as an example, L = 100
mm, M = 150 mm, and H1 = 2 mm.
[0063]
Although various resin materials can be used for the material which forms a resin substrate, 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.
[0064]
The resin substrate of FIG. 3A is manufactured, for example, by casting a resin material in a mold.
03-05-2019
14
[0065]
<Lamination Step> On both opposing surfaces of the resin substrate forming the central portion
4, resin liquid 1 to which an additive was added at a rate at which a predetermined sound
velocity faster than the central portion 4 is obtained was applied to a predetermined thickness w.
After that, heat curing is performed.
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 heating and curing are
sequentially repeated to form layers 8a to 8j and layers 8k to 8t in the next step as shown in FIG.
3B.
The number of layers is not limited to the example shown in FIG. 3B, and may be determined
according to the specifications of the acoustic lens 7.
[0066]
Examples of additives added to the resin material to change the sound velocity of the matrix resin
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 μm or less, more preferably 0.5 μm or less.
[0067]
The volume ratio P of adding the additive to the matrix resin can be obtained by the equation (6),
03-05-2019
15
where Vx is the sound velocity of the additive and V0 is the sound velocity of the resin material
of the matrix.
[0068]
P = (Vα-V1) / (Vx-V1) (6) For example, assuming that Vx = 6400 m / sec, V1 = 2500 m / sec,
and Vα = 2771 m / sec, P = 0.0695 It is sufficient to add 6.95% by volume ratio.
[0069]
In this manner, the layers 8a to 8j and the layers 8k to 8t are respectively formed using the resin
material in which the propagation speed of the ultrasonic waves is adjusted by adding the
additive to the base resin.
[0070]
The mass ratio R can be obtained by equation (7), assuming that the specific gravity of the
additive and the specific gravity ratio C of the resin material of the base material are used.
[0071]
R = P × C / ((1−P) + P × C) (7) For example, when the specific gravity ratio C = 5.41 and P =
0.0695, the mass ratio R is 0.288 In terms of mass ratio, 28.8% may be added.
[0072]
<Cutting and Polishing Step> From the state of being laminated as shown in FIG. 3B, the surface
perpendicular to the surface on which the resin material is laminated so that the distance
between the first lens surface and the second lens surface becomes a predetermined thickness.
The surface is cut along the surface to be cut (in the present embodiment, the surface in the Yaxis direction), and the cut surface is polished to obtain an acoustic lens 7 as shown in FIG.
The acoustic lens 7 of FIG. 3 (c) has the same shape as the acoustic lens 7 described in FIG. 1,
and is a view seen from the Z-axis negative direction.
[0073]
As a cutting method, a dicing saw, a laser cutter, an ultrasonic cutter, a high pressure water
03-05-2019
16
cutter or the like can be used.
[0074]
As described above, in the acoustic lens 7 according to the present embodiment, the propagation
speed of the ultrasonic wave while traveling from the first lens surface to the second lens surface
is in accordance with the position where the ultrasonic wave is incident on the first lens surface.
The ultrasonic waves emitted from the second lens surface are converged to a predetermined
distance.
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.
[0075]
Further, since the acoustic lens 7 of the present embodiment 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 to be 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.
[0076]
Furthermore, since the resin material is hard to transmit gas and liquid, the gas or liquid for
disinfecting penetrates from the surface of the acoustic lens 7 in contact with the object, and the
characteristics of the ultrasonic probe are less likely to deteriorate. .
[0077]
Furthermore, since the acoustic lens 7 of the present embodiment can be formed of a resin
03-05-2019
17
material with a small propagation loss, the acoustic lens 7 with a small attenuation can be
manufactured.
In particular, when a resin material having a frequency of 5 MHz and 2 dB / cm or less is used,
an acoustic lens 7 suitable for an array-type ultrasonic probe using harmonic signals can be
manufactured.
[0078]
FIG. 4 is a cross-sectional view showing the configuration of the head portion of the ultrasound
probe of the embodiment.
[0079]
In this embodiment, an example in which the present invention is applied to an array-type
ultrasonic probe in which the transmitting piezoelectric element and the receiving piezoelectric
element are separated and the operation at the time of transmitting and receiving the ultrasonic
wave is separated will be described. However, the present invention is not particularly limited,
and the present invention can be applied to a single type ultrasonic probe which performs
transmission and reception with a single piezoelectric element.
[0080]
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), and the Zaxis positive direction is the direction in which ultrasonic waves are transmitted.
The Z-axis direction is the stacking direction.
[0081]
The ultrasonic probe 1 shown in FIG. 4 has a fourth electrode 15, a transmitter element layer 2, a
third electrode 14, an intermediate layer 13, a second electrode 10, a receiver element layer 3, a
first electrode on a backing material 5. 9, the matching layer 6, and the acoustic lens 7 are
03-05-2019
18
laminated in this order.
[0082]
Hereafter, each component is demonstrated in order of lamination | stacking.
[0083]
(Transmission Element Layer) The transmission element layer 2 is a piezoelectric element made
of a piezoelectric material such as lead zirconate titanate, and is provided with the third electrode
14 and the fourth electrode 15 on both sides facing each other in the thickness direction.
The thickness of the transmission element layer 2 is about 320 μm.
[0084]
The third electrode 14 and the fourth 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 electrical signal is input to the third electrode 14 and the fourth electrode 15, the
piezoelectric element vibrates, and ultrasonic waves are transmitted from the transmitting
element layer 2 in the positive Z-axis direction.
[0085]
The third electrode 14 and the fourth electrode 15 are formed on the both surfaces of the
transmission element layer 2 using a metal material such as gold, silver, or aluminum by a vapor
deposition method or a photolithography method.
[0086]
(Intermediate Layer) The intermediate layer 13 is formed in the receiving element layer 3 so that
the transmitting element layer 2 does not resonate and vibrate when the receiving element layer
3 receives and vibrates the reflected wave of the ultrasonic wave reflected by the object. It is
provided to absorb vibration.
03-05-2019
19
[0087]
Such an intermediate layer 13 can be formed by molding a resin material.
As a resin material used for the intermediate layer 13, for example, polyvinyl butyral, polyolefin,
polyacrylate, polyimide, polyamide, polyester, polysulfone, epoxy, oxetane, etc. can be used.
[0088]
The thickness of the intermediate layer 13 is selected depending on the sensitivity and frequency
characteristics to be obtained, and is, for example, about 180 to 190 μm.
[0089]
The intermediate layer 13 can be omitted depending on the sensitivity and frequency
characteristics to be obtained.
[0090]
(Receiving Element Layer) The receiving element layer 3 is composed of a plurality of
piezoelectric elements made of an organic piezoelectric material.
[0091]
As an organic piezoelectric material used for the receiving element layer 3, for example, a
polymer of vinylidene fluoride can be used.
Also, for example, as the organic piezoelectric material, a vinylidene fluoride (VDF) based
copolymer can be used.
This vinylidene fluoride-based copolymer is a copolymer (copolymer) of vinylidene fluoride and
other monomers, and as the other monomers, trifluorinated ethylene (TrFE), tetrafluoroethylene
(TeFE) Perfluoroalkylvinylether (PFA), perfluoroalkoxyethylene (PAE), perfluorohexaethylene and
03-05-2019
20
the like can be used.
[0092]
Generally, a piezoelectric element made of a piezoelectric material such as lead zirconate titanate
can only receive ultrasonic waves in a frequency band about twice the frequency of the
fundamental wave, but a piezoelectric element made of an organic piezoelectric material is For
example, ultrasonic waves in a frequency band of about 4 to 5 times the frequency can be
received, which is suitable for broadening the reception frequency band.
Since the ultrasonic signal is received by the organic piezoelectric element having the property of
being able to receive such ultrasonic waves over a wide frequency, the ultrasonic probe 1 and the
ultrasonic diagnostic apparatus 100 in the present embodiment are relatively The frequency
band can be made broadband with a simple structure.
[0093]
The thickness t of the receiving element layer 3 is appropriately set according to the frequency of
the ultrasonic wave to be received, the type of the organic piezoelectric material, and the like.
Assuming that the wavelength of the ultrasonic wave to be received is λ, the reception efficiency
of the reception element layer 3 is the best when the thickness t of the reception element layer 3
is t = λ / 4.
[0094]
Such a receiving element layer 3 is cast from a solution of an organic piezoelectric material to
form a film of a predetermined thickness, heated and crystallized, and then molded into a sheet
of a predetermined size. Make.
[0095]
A first electrode 9 and a second electrode 10 are formed on both sides of the receiving element
layer 3 facing each other in the thickness direction (Z-axis direction).
03-05-2019
21
[0096]
The first electrode 9 and the second electrode 10 are connected to the receiving circuit 43 via a
cable 33 (not shown in FIG. 4).
[0097]
When the receiving element layer 3 receives and vibrates the reflected wave of the ultrasonic
wave reflected by the object, an electrical signal is generated between the first electrode 9 and
the second electrode 10 in the piezoelectric element according to the reflected wave.
The electrical signal generated between the first electrode 9 and the second electrode 10 is
received by the receiving circuit 43 via the cable 33 and is imaged by the image processing unit
44.
[0098]
(Matching Layer) The matching layer 6 has an acoustic impedance that is intermediate between
the acoustic impedances of the human body that is one of the objects and the receiving element
layer 3 to achieve matching of the acoustic impedance.
The matching layer 6 can be formed, for example, by molding a resin material.
[0099]
As a material used for the matching layer 6, it is preferable to use a material having an acoustic
impedance of about 1.7 to 1.8 and a sound velocity of 1300 m / s or more and 2200 m / s or
less near the human body.
For example, polymethylpentene can be used.
03-05-2019
22
[0100]
On the backing material 5, the transmission element layer 2 in which the third electrode 14 and
the fourth electrode 15 described above are formed, the intermediate layer 13, and the reception
in which the first electrode 9 and the second electrode 10 are formed The element layer 3 and
the matching layer 6 are bonded in this order by an adhesive and laminated as shown in FIG.
After lamination, dicing is performed from the matching layer 6 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 fourth electrode 15 to a depth of 100 μm in the negative Z-axis
direction.
After filling a groove made of dicing with a filler made of silicon resin or the like, the acoustic
lens 7 described in FIGS. 1 to 3 is adhered to the uppermost layer.
[0101]
The acoustic lens 7 converges the ultrasonic waves transmitted from the transmission element
layer 2 to a predetermined distance.
[0102]
(Each Configuration and Operation of Ultrasonic Diagnostic Apparatus and Ultrasonic Probe) FIG.
5 is a view showing an appearance configuration of the ultrasonic diagnostic apparatus in the
embodiment.
FIG. 6 is a block diagram showing an electrical configuration of the ultrasonic diagnostic
apparatus in the embodiment.
[0103]
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.
03-05-2019
23
[0104]
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. 6, 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.
[0105]
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.
[0106]
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.
[0107]
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.
[0108]
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.
[0109]
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.
03-05-2019
24
[0110]
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.
[0111]
Hereinafter, the present invention will be described by way of examples, but the present
invention is not limited to these examples.
[0112]
[Examples 1 and 2] (Preparation of Acoustic Lens) In Example 1, the width W = 6 mm in the Xaxis direction and the width H = 2.5 mm in the Z-axis direction in the same configuration as FIG.
An acoustic lens having a focal length f of 30 mm was produced by the procedure described in
FIG. 3 in a rectangular parallelepiped with a width L of 100 mm.
The widths w of the layers 8a to 8j and the layers 8k to 8t were 0.2 mm and W1 = 2 mm,
respectively.
[0113]
In the second embodiment, a rectangular solid having a width W = 6 mm in the X-axis direction, a
width H = 5 mm in the Z-axis direction, and a width L = 100 mm in the Y-axis direction having
the same configuration as FIG. An acoustic lens was made in the same procedure.
The widths w of the layers 8a to 8j and the layers 8k to 8t are the same as in the first
embodiment.
[0114]
Hereafter, it demonstrates in order of a process.
03-05-2019
25
[0115]
<Manufacturing process of resin substrate> A copolymer obtained by crosslinking styrene and
divinylbenzene at a mass ratio of 95: 5 is cast in a mold as a material, and L = 100 mm, M as
shown in FIG. A resin substrate having a rectangular central portion 4 of 150 mm and H1 = 2
mm was produced.
It was 2500 m / sec when sound velocity V1 of the resin substrate which forms central part 4
was measured.
[0116]
<Lamination Step> The sound speeds Va to Vj determined for the layers 8 a to 8 j and the layers
8 k to 8 t of Example 1 were determined as shown in Table 1 using Equation 5.
[0117]
However, H = 2.5 mm, f = 30 mm, V0 = 1530 m / sec, V1 = 2500 m / sec, and x is far from the
center of central portion 4 in the X-axis direction, layers 8a-8j and layers 8k-8t respectively The
distance in the X-axis direction to the side was substituted.
[0118]
[0119]
Next, the ratio of adding the additive which can obtain the sound velocity in Table 1 was
determined as shown in Table 2 using the equations (6) and (7).
[0120]
In the examples, resin liquids 1 to 10 are prepared by mixing, in a predetermined mass ratio,
lipophilic zinc oxide nanoparticles of an additive and a thermal polymerization initiator in styrene
and divinylbenzene, and the resin liquids 1 to 10 are used. Layers to be layers 8a to 8j and layers
8k to 8t were formed, respectively.
[0121]
03-05-2019
26
The mass ratio of the additive contained in the resin liquids 1 to 10 substitutes the sound
velocity Va to Vj obtained in Table 1 into the equation (6) to determine the volume ratio P of
adding the additive to the resin material of the base material And (7), it converted into mass ratio
and calculated | required.
However, the specific gravity ratio C of the copolymer of styrene and divinylbenzene and the
lipophilic zinc oxide nanoparticles was set to 5.41.
[0122]
Table 2 shows mass ratios of styrene, divinylbenzene, lipophilic zinc oxide nanoparticles, and
thermal polymerization initiator of the resin liquids 1 to 10 thus obtained.
[0123]
[0124]
The lipophilic zinc oxide nanoparticles are VP AdNano Z 805 manufactured by Degussa, and
have an average particle diameter of 250 nm.
Further, azobisisobutyronitrile was used as a thermal polymerization initiator.
[0125]
After heat-hardening resin liquid-1 at room temperature and applying it to a thickness w on both
facing surfaces of the resin substrate forming the central portion 4, it was placed in an oven and
heated at 120 ° C. for 5 minutes to be cured.
Next, after applying resin liquid 2 so as to have a thickness w after heat curing at normal
temperature, heat curing was performed under the same conditions.
03-05-2019
27
Thereafter, the application of the resin solution and the heat curing were sequentially repeated
under the same conditions, and the application to the resin solution -10 and the heat curing were
performed.
[0126]
<Cutting, Polishing Step> From the laminated state as shown in FIG. 3 (b), after cutting in the Yaxis direction along the plane orthogonal to the surface on which the resin material is laminated
every 3 mm in the Z-axis direction Polishing was performed to obtain H = 2.5 mm, L = 100 mm,
W = 6 mm, and acoustic lens 7 of Example 1 as shown in FIG. 3C was obtained.
[0127]
In addition, after cutting in the Y-axis direction along the plane orthogonal to the plane on which
the resin material is laminated every 5.5 mm in the Z-axis direction from the laminated state as
shown in FIG. H = 5 mm, L = 100 mm, W = 6 mm to obtain an acoustic lens 7 of Example 2 as
shown in FIG. 3 (c).
[0128]
In addition, the cutting was performed with a dicing saw.
[0129]
(Production of Ultrasonic Probe) The prototyped ultrasonic probe 1 was produced as follows.
[0130]
The transmitter 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 μm in the Z direction.
[0131]
Next, gold was vacuum-deposited on both sides of the transmission element layer 2 to produce
0.3 μm thick third and fourth electrodes 14 and 15.
[0132]
The intermediate layer 13 was formed of polyvinyl butyral as a material with a length of 10 mm
03-05-2019
28
in the X direction, a length of 55 mm in the Y direction, and a length (thickness) in the Z
direction of 185 μm.
[0133]
Receiving element layer 3 heats polyvinylidene fluoride copolymer powder (weight average
molecular weight 290,000) having a molar ratio of vinylidene fluoride (hereinafter VDF) to
trifluoroethylene (below 3FE) of 75:25 to 50 ° C. A solution dissolved in a 9: 1 mixed solvent of
ethyl methyl ketone (hereinafter MEK) and dimethylformamide (hereinafter DMF) was cast on a
glass plate.
Thereafter, the solvent was dried at 50 ° C. to obtain a film (organic piezoelectric material)
having a thickness of about 140 μm and a melting point of 155 ° C.
[0134]
This film was drawn four times at room temperature by a uniaxial stretching machine with a load
cell capable of measuring the load applied to the chuck.
The tension in the stretching axial direction at the end of the 4-fold stretching was 2.2 N per unit
width (mm).
The stretching machine was heated while maintaining the stretched length, and heat treatment
was performed at 135 ° C. for 1 hour.
Then, it cooled to room temperature, controlling the distance between chucks (relaxation
processing) so that tension might not become zero.
The film thickness of the obtained film after heat treatment was 40 μm.
[0135]
03-05-2019
29
Thereafter, it was formed into a sheet having a length of 55 mm in the Y direction and a length of
10 mm in the X direction.
Gold or aluminum is deposited on both sides of the film obtained here so that the surface
resistance is 20 Ω or less, and 0.3 μm thick surface electrodes (first electrode 9 and second
electrode 10) are attached on both sides. A sample was obtained.
[0136]
Subsequently, a polarization process was performed while applying an AC voltage of 0.1 Hz to
this electrode at room temperature.
The polarization treatment was performed from a low voltage, and a voltage was gradually
applied until the interelectrode electric field finally reached 100 MV / m.
The final amount of polarization was determined from the amount of residual polarization when
the piezoelectric material was regarded as a capacitor, that is, the film thickness, the electrode
area, and the charge storage amount with respect to the applied electric field. .
[0137]
The matching layer 6 was made of polymethylpentene, and was manufactured to have a length of
55 mm in the Y direction, a length of 10 mm in the X direction, and a length (thickness) of 140
μm in the Z direction.
[0138]
Transmitting element layer 2 in which third electrode 14 and fourth electrode 15 are formed on
backing material 5, receiving element layer 3 in which intermediate layer 13, first electrode 9
and second electrode 10 are formed, matching The layers 6 are adhered in the order of the
adhesive and laminated as shown in FIG.
03-05-2019
30
After lamination, dicing was performed from the matching layer 6 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 μm in the negative Z-axis direction.
[0139]
Finally, the acoustic lens 7 was adhered to the uppermost layer, and five ultrasonic probes 1 of
Example 1 were produced.
[0140]
[Comparative Example 1] (Fabrication of Acoustic Lens) Acoustic lens having a convex lens
surface having 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 Were produced by molding
silicone rubber.
The maximum width H in the Z-axis direction is 460 μm.
[0141]
(Production of Ultrasonic Probe) Each layer was laminated in the same procedure as in Example
1, and finally an acoustic lens made of silicone rubber was adhered to the top layer, and five
ultrasonic probes 1 of Comparative Example 1 were used. Made.
[0142]
[Evaluation Method] The focal length and the attenuation of each of the ultrasonic probes of
Example 1 and Example 2 and Comparative Example 1 were measured, and the average value
was determined.
The focal length was measured by an underwater hydrophone method, and the attenuation was
measured by a single-around method.
03-05-2019
31
[0143]
The surface of the acoustic lens was subjected to 500 friction tests by applying a load of 50 g to
a non-woven wiper (BEMCOT M-3II (trade name), manufactured by Asahi Kasei Co., Ltd.), and the
focal length was measured again.
[0144]
[result]
[0145]
[0146]
As shown in Table 3, the focal length of Example 1 before the friction test is 30 mm, the focal
length of Example 2 is 15 mm, and an acoustic lens having a predetermined focal length can be
obtained by changing the thickness H of the acoustic lens. That was confirmed.
[0147]
[0148]
The focal lengths of Example 1 and Comparative Example 1 before the friction test were 30 mm
as shown in Table 4.
[0149]
As shown in Table 4, Example 1 was 1.2 dB at a frequency of 5 MHz and 8.3 dB at a frequency of
15 MHz, and Example 2 was 2.4 dB at a frequency of 5 MHz and 16.6 dB at a frequency of 15
MHz.
Since the acoustic lens 7 of Example 1 has H = 2.5 mm, the attenuation characteristic at a
frequency of 5 MHz is 4.8 dB / cm.
In addition, since the acoustic lens 7 of Example 2 has H = 5 mm, the attenuation characteristic
of the frequency 5 MHz is 4.8 dB / cm.
03-05-2019
32
[0150]
On the other hand, in Comparative Example 1, as shown in Table 4, the amount of 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 MHz and 13 dB at a frequency of 15 MHz. It has become.
Thus, according to the present invention, it has been confirmed that an acoustic lens with less
propagation loss can be obtained at the same focal length.
[0151]
The focal length of Example 1 after the friction test was not changed as shown in Table 4, but the
focal length of Comparative Example 1 was changed to 41 mm.
From this, it can be confirmed that the acoustic lens of the present invention is excellent in
abrasion resistance and high in durability.
[0152]
As described above, according to the present invention, it has an acoustic lens which is excellent
in adhesion to a subject and has a small propagation loss of ultrasonic waves, an ultrasonic probe
having the acoustic lens, and the ultrasonic probe. An ultrasonic diagnostic apparatus can be
provided.
[0153]
Reference Signs List 1 ultrasound probe 2 transmitting element 3 receiving element 4 central
portion 5 backing material 6 matching layer 7 acoustic lens 8 peripheral portion 9 first electrode
10 second electrode 13 intermediate layer 14 third electrode 15 fourth electrode 20 substrate
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 50 Liquid 100 Ultrasonic diagnostic apparatus
03-05-2019
33
Документ
Категория
Без категории
Просмотров
0
Размер файла
46 Кб
Теги
jp2010252065
1/--страниц
Пожаловаться на содержимое документа